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Coalbed methane (CBM) is an increasingly important unconventional natural gas. Production logging can provide important information about the production status of each layer in a CBM well, which is crucial for developing and adjusting development plans. However, currently, only open-hole logging is done for CBM wells, and there is no mature technology for production testing of wells that produce low amounts of gas. To address this issue, a new method has been proposed in this paper for measuring the production profile of CBM wells. This method is based on the pressure difference method and measures the gas–liquid two-phase flow in a 125 mm vertical rising circular tube. The researchers established a simulation model of the CBM wellbore pressure difference method and obtained four flow patterns: bubble flow, slug flow, churn flow, and annular flow. We studied the relationship between the pressure difference and gas and water flow rates at different positions and spacing between measuring points in the wellbore. A differential pressure flowmeter without a throttling device was developed, and gas–liquid dynamic experiments were carried out through a simulation experiment platform to verify the feasibility of the flowmeter. Two well field tests were conducted in Shanxi CBM fields using differential pressure flowmeters, which accurately and quantitatively measured the stratified gas production of CBM wells. This technology can help improve the productivity and development efficiency of CBM wells. [ABSTRACT FROM AUTHOR]

Gas sensors are essential devices to detect harmful gases that are present in the environment. Metal oxide semiconductors (MOSs) are used as sensing materials to detect harmful gases. Some of the metal oxides, like ZnO, SnO2, WO3, NiO, etc. have been used to detect the gases. This paper provides a theoretical study of gas sensing using MOSs. Many programs are available for the theoretical Density Functional Theory (DFT) approach. The theoretical calculation provides many properties about the sensing material, like electronic properties, magnetic properties, charge difference calculation, and Vander wall interaction between the sensing material surface and adsorbing molecule. The nanostructure provides better gas sensing performance due to its high surface-to-volume ratio. This paper is based on the DFT study and provides gas-sensing results using electronic properties. [ABSTRACT FROM AUTHOR]

As demand for energy increases, the number of "three-high" (high-pressure, high-yield, high-sulfur) gas Wells has doubled, the severe stress fluctuation of pipe string caused by downhole high-pressure environment leads to the failure of rope fracture is particularly prominent. It is easy to cause pipeline blockage and large amount of high-pressure toxic gas leakage caused by tool string accidental falling. Therefore, based on the theory of Love and elastoplastic contact theory, and considering the influence of Poisson's ratio effect, this article establishes a calculation model for tensile fatigue of interaction between rope strands to study the influence of key structural parameters and breaking wire position on stress distribution and fatigue life of rope. The results show that: the core strand of the rope is the main force position, the overall stress shows the trend of decreasing with the increase of winding radius; when the rope is stretched, the axial deformation near the core of the rope is smaller than the deformation far from the core; under the same number of broken wires, the fatigue life of different ropes is related to the location of broken wires, the farther the location of broken wires from the core of the rope, the higher the fatigue life. The research work in this article provides theoretical guidance for the safe operation of ropes in "three-high" gas wells. [ABSTRACT FROM AUTHOR]

Fracturing horizontal well casing deformation has become very prominent, particularly in tectonic stress-concentrated shale gas fields, limiting the efficient development progress of shale gas. The main failure mode of casing shearing deformation had been attributed to fault slip caused by multi-fracturing. The current research did not provide a clear picture of the dynamic evolution relationship between hydraulic fracturing, fault slip, and casing deformation. In this paper, the dynamic model of fault slip induced by formation pressure change is established, incorporating the effects of stress drop, physical change of friction, and casing and cement-sheath resistance loads. The discontinuous displacement approach and explicit/implicit coupling iteration methods are used to reveal the relationships between the effective normal stress, shear stress, friction coefficient, and sliding velocity during the fault slip process. Furthermore, the microscopic process of casing deformation sheared by fault slip is investigated using static equilibrium theory, and a characterization method for determining the amount casing deformation caused by real-scale fault slip is proposed. The results show that three stages exist in the process of casing deformation sheared by fault slip, including trigger activation stage, accelerated slip stage, and deceleration slip stage. Fault slip is clearly influenced by fault strike. To reduce the amount of fault slip, the fault direction with the maximum in-situ stress should be avoided as much as possible. Serious casing deformation still occurs for large-scale activated faults even though the optimization measure of wellbore structure has been well taken. To fundamentally reduce the possibility of casing shear deformation, it is necessary to prevent fault slip through optimizing the design of hydraulic fracturing. This study lays the theoretical groundwork for the casing deformation control method in shale gas wells. [ABSTRACT FROM AUTHOR]

This article provides an overview of the political and economic challenges faced by the Labor Government in Queensland from July to December 2023. The government struggled with issues such as inflation, youth crime, housing, and health. Infrastructure cost blowouts caused public opinion pain and led to a change in Labor leadership. The period also saw Queensland record the lowest 'Yes' vote in the First Nations Voice to Parliament referendum. The economy faced challenges with rising inflation and joblessness, and the government faced criticism for its handling of infrastructure projects and increased coal royalty rates. The government announced support packages for the copper industry and renewable energy initiatives. Environmental concerns and natural disasters also impacted the state. The government faced challenges in addressing youth crime, the housing crisis, and health issues such as hospital ramping and staff shortages. Public opinion support for the government and the premier declined during this period, with polls showing lower primary votes for Labor and decreasing approval ratings for Premier Palaszczuk. The leadership of the Labor party also faced challenges, leading to the resignation of Palaszczuk and the appointment of Steven Miles as the new premier. The Voice to Parliament referendum in Queensland, which aimed to establish an Aboriginal and Torres Strait Islander advisory body, saw a majority 'No' vote in the state. The defeat of the referendum led to the withdrawal of support for a treaty with First Nations people by both the government and the opposition leader. The article also mentions the passing of two political figures in Queensland, former Premier Mike Ahern and [Extracted from the article]

The following study presents the results of research in the field of the performance of geopolymers consisting of Class F fly ash with an alkaline activator solution consisting only of sodium metasilicate (Na2SiO3) and water. The performances of this geopolymer are compared to the those of American Petroleum Institute (API) Class G cement. This comparison is to evaluate the potential of the geopolymer as an alternative to cement in cementing hydrocarbon wells in the oil and gas industry. The gap in the research is determining the performance properties that restrict the use of fly ash in the oil and gas industry. Using only sodium metasilicate as an activator with water, the solution creates a strong binding gel for the geopolymer and activates the aluminosilicate properties of the fly ash. This geopolymer is compared with Class G cement without additives to determine their base performances in high pressure and high temperature conditions, as well as note any properties that are affected in the process. This commences by formulating recipes of these two materials from workable ratios and concentrations. The ratios are narrowed down to the best working models to proceed to comparative performance testing. The tests included exploring their vital performances in fluid loss and thickening time. The results produced suggest that Class G cement generally has less fluid loss at low temperature than the geopolymer but could not maintain its integrity and structure as temperatures increased. Class G cement exhibited stability, consistencies of 100 Bcs (Bearden Consistency Units), and a faster thickening time of 1 h and 48 min when placed under high temperature and high-pressure conditions, respectively. However, the geopolymer showed more consistency regarding fluid loss with respect to rising pressure and temperature, and smoother, less fractured samples emerging from both tests. Though the geopolymer showed stronger performances in thickening and water retention, the experiments showed that it is not a uniform and consistent material like Class G cement. Through the use of different additives and intricate design, the sample may show success, but may prove more difficult and complex to apply than the industry standard and uniform content of Class G cement. [ABSTRACT FROM AUTHOR]

The paper focuses on the excellent chemical inertness characteristics of nonmetallic materials and evaluates the performance of three types of new carbon fiber‐reinforced resin‐based composites under various simulated corrosion conditions in wellbores. Through comprehensive analysis of macro and micromorphology, moisture absorption performance, strength performance, and molecular structure, the damage characteristics and applicability of carbon fiber composites in oil and gas wellbore conditions were clarified. T700/epoxy and T300/epoxy composites experienced damage dominated by physical effects such as moisture absorption and wet thermal stress, manifested as swelling, deformation, and cracking at the macro level, and pore formation and delamination cracking at the micro level. After continuous corrosion tests, the tensile strength of T700/bismaleimide composite (913 MPa) was higher than that of T700/epoxy composite (814 MPa) and T300/epoxy composite (636 MPa), with reductions of 12.4%, 14.3%, and 19.5% respectively. The research results showed T700 carbon fiber/bismaleimide resin composites had the best mechanical and chemical stability. [ABSTRACT FROM AUTHOR]

The intensive cluster fracturing technology is widely applied in deep shale reservoirs. However, field data show that the fracture initiation time and propagation length of each cluster are different, which causes significant non-uniformity and affects the fracturing results. In this paper, a hydraulic fracture asynchronous initiation and propagation model for deep shale gas is established based on mechanics theory, which can consider the influence of in-situ stress variation and stress interference effect on the fracture asynchronous initiation and propagation behavior. According to the model design parameters, deep shale hydraulic fractures are regulated and optimized in combination with the non-uniform flow-limiting perforation technology to achieve uniform fracture propagation. The results show that, the non-uniformity of each fracture is obvious using conventional uniform perforation. However, with non-uniform perforation, each cluster perforation number is adjusted, the difference of initiation time and each fracture propagation velocity is significantly reduced, and the length of all fractures tend to be basically the same. And the field monitoring data are in good agreement with the calculation results, which verifies the reliability of the model. This study can reduce design blindness of non-uniform flow-limiting perforation technique, and has an important theoretical guidance for the optimal design of fracturing. [ABSTRACT FROM AUTHOR]

Coal seams exhibiting nearly horizontal bedding, and fractures can be characterized as transversely isotropic media with a vertical axis of symmetry, known as vertical transverse isotropy coal seams. The resulting anisotropy cannot be overlooked in high‐precision seismic velocity analysis, migration imaging and pre‐stack inversion. Therefore, we estimate the anisotropy of the vertical transverse isotropy coal seam (using the anisotropic Thomsen's parameters ε, γ and δ) by inverting the horizontal P‐ and SH‐wave velocities and fracture density based on a rock physics model. The Mori–Tanaka model and Brown–Korringa formula were first used to quantify the anisotropy of the vertical transverse isotropy coal seams impacted by dry and fluid‐saturated fractures. Subsequently, we formulated an equation for the inversion of horizontal P‐ and SH‐wave velocities, considering the measured vertical P‐ and SH‐wave velocities as constrained parameters. This approach is generally applied in vertical drilling scenarios. We tested the inversion method using the ultrasonic test results of coal samples collected from the southern margin of the Qinshui Basin, China and then used it on the full waveform logging data from a vertical coalbed methane well. Both the inversion results of horizontal P‐ and SH‐wave velocities and the estimated anisotropic parameters (ε and γ) were in good agreement with the ultrasonic test results of coal samples, although the accuracy of δ was slightly lower. Therefore, we believe that the proposed method can be extended to estimate the anisotropy of vertical transverse isotropy medium (assuming suitable rock physics models) for the ultrasonic testing of rock samples and full waveform logging along the vertical direction in near‐horizontal formations. [ABSTRACT FROM AUTHOR]

It is the key technology to reduce the pollution of production layer by using retrievable bridge plug to plug production string and carry out snubbing operation. This paper establishes the simulation calculation model of the small diameter bridge plug rubber tube through the rubber thermal aging experiment. The influence of rubber combination on sealing performance and safety under high temperature and high pressure was analyzed, and the rubber structure was optimized. The results show that the sealing performance of the three-rubber tube structure is about 8.7% higher than that of the double-rubber tube structure at 120 °C and 55 MPa. In order to take into account the deformation and sealing requirements of the rubber tube, the preset trapezoidal ring groove structure (groove number n, groove width l, groove depth δ) in the rubber tube is optimized. Under the condition of 35 MPa setting load, the optimized A-structure rubber tube (n = 3, l = 10.5 mm, δ = 0.5 mm) improves the sealing performance by about 21.15% and reduces the Mises stress by 4.88% compared with that before optimization. It is suitable for oil and gas wells with long-term sealing and high safety requirements. The sealing performance of the optimized B-structure rubber tube (n = 3, l = 10.5 mm, δ = 1.5 mm) can be improved by about 43.94%. Although the Mises stress is increased by 15.97%, it is still within the safe range and can be applied to the working conditions with high sealing pressure and short-term sealing. [ABSTRACT FROM AUTHOR]

Groundwater at depths exceeding 500 m can be an important source of freshwater. However, the characteristics of deep groundwater in many regions of the world, including Indonesia's sedimentary basins, remain vaguely defined. This study investigates the pressure regimes, hydraulic head distributions, salinity, and hydrochemical facies of deep groundwater using available evidence from oil and gas exploration wells in the Lower Kutai Basin of Indonesia. Pressure measurements and wireline log data reveal three pressure regimes within the basin: hydrostatic, overpressure, and underpressure. The top of the overpressure varies, from close to the surface onshore to depths of ~4.5 and ~3.8 km in the Mahakam Delta and offshore, respectively. Computed hydraulic heads at the top of the overpressure range from ~191 m above sea level onshore to ~71 m below sea level offshore, and are indicative of regional groundwater flow. The observed salinity of deep groundwater within the basin indicates predominantly brackish or saline conditions. Fresh (total dissolved solids < 1 g/L) groundwater to a depth of ~2 km is found at a small minority of wells onshore and in the delta; no fresh groundwater is found offshore. Four hydrochemical facies are observed: Na+/Cl–, Ca2+/Cl–, Na+/HCO3–, and Na+–Ca2+/HCO3–. This study indicates that deep fresh groundwater in the Lower Kutai Basin is of localized occurrence. Recharge from meteoric water may replenish deep fresh groundwater within the hydrostatic zone and sustain water supplies, whether brackish or fresh. Water produced from clay diagenesis is also cited as a possible process of freshening deep groundwater. [ABSTRACT FROM AUTHOR]

Lesser prairie-chicken (Tympanuchus pallidicinctus) populations of in the Sand Sagebrush Prairie Ecoregion of southwest Kansas and southeast Colorado, USA, have declined sharply since the mid-1980s. Decreased quality and availability of habitat are believed to be the main drivers of declines. Our objective was to reconstruct broad-scale change in the ecoregion since 1985 as a potential factor in population declines. We assessed temporal change from 1985–2015 in landcover types and calculated landscape metrics using Land Change Monitoring, Assessment, and Projection imagery layers. We also documented presence of anthropogenic structures including oil wells and electrical transmission lines. Landcover type composition changed little since 1990 across the Sand Sagebrush Prairie Ecoregion. However, anthropogenic structures (i.e., oil/gas wells, cell towers, wind farms, and transmission lines) notably increased, potentially causing functional habitat loss at a broad scale. Increased anthropogenic structures may have decreased habitat availability as well as the quality of existing habitat for lesser prairie-chickens, possibly contributing to recent population declines throughout the Sand Sagebrush Prairie Ecoregion. [ABSTRACT FROM AUTHOR]

In the future, hydrogen will be more frequently injected into natural gas networks for storage and transportation purposes. A diffusion jet flame forms when gaseous fuel leakage occurs during the transportation or utilization of hydrogen-enriched natural gas, and the fuel is ignited by an ignition source in still air. In the study, methane was chosen to simulate natural gas. Experiments with the hydrogen addition fraction reaching up to 20% were performed to study the effects of the initial flame angle (θ = 90°, 60°, 30°, 0°, and −30°), variable nozzle diameter (d e = 3.15, 4, 4.94, 5.65, and 6 mm) and a multitude of fuel flow rates (10, 20, 30, 40, 50, and 60 L/min) on the morphological parameters of the gas jet flames. The geometrical features of the jet flame were determined via video processing for each experiment. The geometrical parameters of hydrogen-enriched natural gas were quantified under different conditions. The experimental results indicate that a dimensionless prediction model was established for the flame height of hydrogen-enriched natural gas by modifying the flame Froude number ( F r f) for vertical jet flames. For upward jet flames, the normalized flame horizontal projection length (L x) of hydrogen-enriched natural gas is well correlated with Q ∗. A global prediction model for inclination angles of 0° ≤ θ ≤ 60° and 2000 < Q ∗<20,000 was proposed based on the experimental data. For downward jet flames, the normalized horizontal projection length and downward extension length (L d) of the hydrogen-enriched natural gas jet flame are correlated with Q ∗, with powers of 2/5 and 3/5, respectively. Dimensionless prediction models for the horizontal projection length and downward extension length are given by modifying the flame Froude number. Quantitative results were proposed in order to gain insight into the development of the key parameters and the effects on the environment, from which extinguishing concepts and safety areas can be directly derived. • Hydrogen-enriched natural gas jet fire under various conditions was studied. • Macroscopic characteristics of hydrogen-enriched natural gas jet fire were quantified. • A unified empirical model was established to predict the horizontal extension length of hydrogen-enriched natural gas jet fire. • The normalized flame height and downward extension length correlated to the modified Froude number. [ABSTRACT FROM AUTHOR]

Horizontal wells have significant advantages in coal bed methane exploration and development blocks. However, its application in new exploration and development blocks could be challenging. Limited geological data, uncertain geological conditions, and the emergence of micro-faults in pre-drilled target coal seams make it hard to accurately control the well trajectory. The well trajectory prior to drilling needs to be optimized to ensure that the drilling trajectory is within the target coal seam and to prevent any reduction in drilling ratio (defined here as the percentage of the drilling trajectory in the entire horizontal section of the well located in the target coal seam) caused by faults. In this study, the well trajectory optimization is achieved by implementing the following process to drill pilot hole, acquire 2D resonance, and azimuthal gamma logging while drilling. The pilot hole drilling can obtain the characteristic parameters of the target coal seam and the top and bottom rock layers in advance, which can provide judgment values for the landing site design and real-time monitoring of whether the wellbore trajectory extends along the target coal seam; 2D resonance exploration can obtain the construction of set orientation before drilling and the development of small faults and formation fluctuations in the horizontal section, which can optimize the well trajectory in advance; the azimuth gamma logging while drilling technology can monitor the layers drilled by the current drill bit in real time, and can provide timely and accurate well trajectory adjustment methods.The horizontal well-Q in the Block-W of the Qinshui Basin was taken as a case study and underwent technical mechanism research and applicability analysis. The implementation of this new innovative process resulted in a successful drilling of a 711 m horizontal section, with a target coal seam drilling rate of 80%. Compared to previous L-type wells, the drilling rate increased by about 20%, and the drilling cycle shortened by 25%. The technical experience gained from this successful case provides valuable insight for low-cost exploration and development of new coalbed methane blocks. [ABSTRACT FROM AUTHOR]

Gas migration incidents, particularly stream contamination cases, have been rarely investigated and gone through the peer review process, with the exception of three sites in northeast Pennsylvania (Dimock and two Sugar Runs in Lycoming and Bradford counties, respectively) where air emission surveys, dissolved methane measurements, and structural (hydro)geologic interpretations have been used to demonstrate potential environmental impacts due to shale gas operations. In addition to reviewing previously published work from these three sites, we report and analyze unpublished new data trying to determine if a direct relationship between methane migration, stream contamination, and air emissions exists at those sites. Our analysis indicates that subsurface methane migration, stream methane contamination, and air emissions might not be all present or detectable at a faulty/leaky shale gas well. Which of these signs of contamination, if any, exist is largely controlled by the local (hydro)geologic conditions. In each case, the most likely migration pathway was from gas charged zones up well annular spaces to confined permeable formations, then laterally to a direct discharge or by vertically controlled joints to streams, water wells, and the atmosphere. The confining units act as barriers to the buoyant movement of stray gases, allowing subsurface travel of gas for 1–4 km from a leaky gas well. The knowledge we learn from these three sites can guide the future investigations of methane contamination cases in other regions. [ABSTRACT FROM AUTHOR]

Context. The past few years have seen a revolution in the study of circumstellar disks. New instrumentation in the near-infrared and (sub)millimeter regimes have allowed us to routinely spatially resolve disks around young stars of nearby star-forming regions. As a result, we have found that substructures with scales of ~10 au in disks are common. We have also revealed a zoo of different morphologies, sizes, and luminosities that is as complex as the diversity of architectures found in evolved exoplanet systems. Aims. We study disk evolutionary trends as they appear in scattered light observations. Scattered light traces the micron-sized particles at the disk surface that are well coupled to the gas. This means that scattered light observations can be used to trace the distribution of the disk gas and its interaction with embedded perturbers. Methods. We used VLT/SPHERE to observe 20 systems in the Cha I cloud in polarized scattered light in the near-infrared. We combined the scattered light observations with existing literature data on stellar properties and with archival ALMA continuum data to study trends with system age and dust mass. We also connected resolved near-infrared observations with the spectral energy distributions of the systems. Results. In 13 of the 20 systems included in this study we detected resolved scattered light signals from circumstellar dust. For the CR Cha, CT Cha, CV Cha, SY Cha, SZ Cha, and VZ Cha systems we present the first detailed descriptions of the disks in scattered light. The observations found typically smooth or faint disks, often with little substructure, with the notable exceptions of SZ Cha, which shows an extended multiple-ringed disk, and WW Cha, which shows interaction with the cloud environment. New high S/N K-band observations of the HD 97048 system in our survey reveal a significant brightness asymmetry that may point to disk misalignment and subsequent shadowing of outer disk regions, possibly related to the suggested planet candidate in the disk. We resolve for the first time the stellar binary in the CS Cha system. Multiple wavelength observations of the disk around CS Cha have revealed that the system contains small, compact dust grains that may be strongly settled, consistent with numerical studies of circumbinary disks. We find in our sample that there is a strong anti-correlation between the presence of a (close) stellar companion and the detection of circumstellar material with five of our seven nondetections located in binary systems. We also find a correlation between disk mass, as inferred from millimeter observations, and the detection of scattered light signal. Finally, we find a tentative correlation between relative disk-to-star brightness in scattered light and the presence of a dust cavity in the inner (unresolved) disk, as traced by the system spectral energy distribution. At the same time, faint disks in our sample are generally younger than 2 Myr. [ABSTRACT FROM AUTHOR]

Aiming at the problem that the water intrusion control factors of multi-stage fracturing horizontal wells in tight gas reservoirs in edge and bottom water are not clear, the linear supply boundary is used to characterize the water intrusion characteristics and derive the mathematical characterization formula, considering the stress sensitivity and diffusion mechanisms of tight gas, and the water intrusion flow model of multi-stage fracturing horizontal well in tight gas reservoirs in edge and bottom water is established, and the bottom pressure and its derivative curves are obtained by Laplace and perturbation transformation. Furthermore, the influence of water intrusion strength, matrix-fracture channeling capacity, storage capacity coefficient, fracture segment spacing, fracture conductivity and other factors on the degree of water intrusion and water exposure time were analyzed. By fitting the well test data of the established model, the water intrusion intensity parameters can be obtained, and the water intrusion control of gas wells can be guided according to this parameter. The data analysis of two typical wells in the western oilfield was carried out by applying the established model, and the analysis results were well matched with the actual production, which verified the reliability of the model, and according to the analysis results, the treatment measures of the two wells were proposed, and the two wells obtained good production results. [ABSTRACT FROM AUTHOR]

• The model for multiple horizontal wells considers heterogeneous fracture network. • The number of frac hits is determined by pressure differentials and derivatives. • Higher conductivity promotes inter-well pressure equilibrium. • Lower conductivity is beneficial to extended interference testing. Frac hits can significantly impact the final development results. Therefore, accurately and quickly understanding the frac-hit interference between wells is crucial for efficient development. At present, traditional pressure/production data analysis methods and numerical simulation methods can characterize the frac-hit interference. However, challenges such as quantitatively assess interference, high uncertainty in modeling parameters and computational time still exist. A quantitative evaluation method for the interference between wells with complex fracture networks has not been reported yet. This paper takes shale oil reservoir with three production wells as an example and establishes a semi-analytical model (frac-hit semi-analytical model, FSM) based on the linear flow characteristics. The model accurately characterizes the non-uniform distribution of complex fracture networks in the stimulated reservoir volume by introducing fractal theory. A quantitative evaluation index, interference coefficient, is defined to assess the interference. The coupled flow model is applied to evaluate the effects of interference in three typical wells in a continental shale oil field in China. We can see from the actual data fitting of the FSM model that the interference coefficients between target well A and adjacent wells B and C are 0.1 and 0.05, respectively, which means there are about 8–10 and 3–5 frac hits, respectively. Comprehensive analysis for the effects of interference shows that the current inter-well interference is beneficial for production in low-pressure areas but detrimental to new well production. Based on this, sensitivity analysis is generated to illustrate the relationship between the conductivity of combined fractures arising from hits and the interference coefficient. As the interference increases, the propagation of inter-well pressure accelerates, significantly reducing the time required for inter-well pressure equilibrium. The research findings have important guiding implications for the quantitative evaluation of inter-well interference in field operations of horizontal shale oil and gas wells and optimization of fracturing operations. [ABSTRACT FROM AUTHOR]

In order to improve the comprehensive performance of TC11 titanium alloy and make it more widely used in the field of oil and gas wells, cobalt oxide micro‐powder from 0 to 0.8 g·L−1 was added in the electrolyte. The effects of cobalt oxide micro‐powder concentration on properties of micro‐arc oxidation (MAO) coatings were analyzed by scanning electron microscopy, X‐ray diffraction, X‐ray photoelectron spectroscopy, and electrochemical workstation. With cobalt oxide micro‐powder increased, the oxide voltage increased, and the discharge coating micropores became more uniform. The increase in thickness and hardness also improved corrosion resistance. The comprehensive performance after added 0.6 g·L−1 of cobalt oxide was the best, with a doubling increase in thickness and hardness, reaching 32.1 µm and 721.2 HV, respectively. The corrosion rate reduced to 4.19 × 10−10 mm·a−1, which reduced by three orders of magnitude. In addition, the substrates and samples prepared with 0.6 g·L−1 cobalt oxidation were used for the erosion corrosion tests in different NaCl solutions, and it was found that the weight loss and rate of the MAO sample (slight corrosion) were lower than substrates, indicating that the cobalt oxide doped coatings had better corrosion resistance. [ABSTRACT FROM AUTHOR]

Assessing the appropriateness of existing native plant materials can both determine which seed source to utilize for restoration projects, and identify locations for which new seed sources need to be developed. Here, we demonstrate an approach to meet these needs. This method identifies areas of high restoration need based on disturbance patterns, assesses the regional suitability of existing native plant materials based on climate similarity, and highlights geographic (and climatic) gaps where existing materials are likely unsuitable and where plant material development projects can be prioritized. We examined 12 high priority restoration species across the Colorado Plateau, a 38‐million‐ha region of the Intermountain West, United States to test our methodological pipeline. Fifty‐four percent of the Colorado Plateau is disturbed by livestock grazing, wildfires that have burned in the past 20 years, or energy production from oil and gas wells, natural gas pipelines, and coal mines. Of the 28 commercially available plant materials for six of the focal species, only 3 have climate similarity that encompass more than 50% of the species modeled habitat on the Colorado Plateau. Across all commercial materials, most species (10 of 12) do not have any suitable plant material for 70% or more of their geographic range on the Colorado Plateau. Of those areas identified as not having any suitable plant materials, 47–56% are also disturbed. Our method provides usable, flexible protocols and spatially referenced data sources for optimizing the planning of new native plant materials in any region where restoration is needed and spatial data are available. [ABSTRACT FROM AUTHOR]

The estimated ultimate recovery (EUR) of a single well must be predicted to achieve scale-effective shale gas extraction. Accurately forecasting EUR is difficult due to the impact of various geological, engineering, and production factors. Based on data from 200 wells in the Weiyuan block, this paper used Pearson correlation and mutual information to eliminate the factors with a high correlation among the 31 EUR influencing factors. The RF-RFE algorithm was then used to identify the six most important factors controlling the EUR of shale gas wells. XGBoost, RF, SVM, and MLR models were built and trained with the six dominating factors screened as features and EUR as labels. In this process, the model parameters were optimized, and finally the prediction accuracies of the models were compared. The results showed that the thickness of a high-quality reservoir was the dominating factor in geology; the high-quality reservoir length drilled, the fracturing fluid volume, the proppant volume, and the fluid volume per length were the dominating factors in engineering; and the 360−day flowback rate was the dominating factor in production. Compared to the SVM and MLR models, the XG Boost and the RF models based on integration better predicted EUR. The XGBoost model had a correlation coefficient of 0.9 between predicted and observed values, and its standard deviation was closest to the observed values' standard deviation, making it the best model for EUR prediction among the four types of models. Identifying the dominating factors of shale gas single-well EUR can provide significant guidance for development practice, and using the optimized XGBoost model to forecast the shale gas single-well EUR provides a novel idea for predicting shale gas well production. [ABSTRACT FROM AUTHOR]

The detection of N-hexanoyl-l-homoserine lactone (C6-HSL), a crucial signal in Gram-negative bacterial communication, is essential for addressing microbiologically influenced corrosion (MIC) induced by sulfate-reducing bacteria (SRB) in oil and gas industries. Metal oxides (MOx) intercalated into conducting polymers (CPs) offer a promising sensing approach due to their effective detection of biological molecules such as C6-HSL. In this study, we synthesized and characterized two MOx/polyaniline-dodecyl benzene sulfonic acid (PANI-DBSA) nanocomposites, namely ZnO/PANI-DBSA and Fe2O3/PANI-DBSA. These nanocomposites were applied with 1% by-weight carbon paste over a carbon working electrode (WE) for qualitative and quantitative detection of C6-HSL through electrochemical analysis. The electrochemical impedance spectroscopy (EIS) confirmed the composites' capability to monitor C6-HSL produced by SRB-biofilm, with detection limits of 624 ppm for ZnO/PANI-DBSA and 441 ppm for Fe2O3/PANI-DBSA. Furthermore, calorimetric measurements validated the presence of SRB-biofilm, supporting the EIS analysis. The utilization of these MOx/CP nanocomposites offers a practical approach for detecting C6-HSL and monitoring SRB-biofilm formation, aiding in MIC management in oil and gas wells. The ZnO/PANI-DBSA-based sensor exhibited higher sensitivity towards C6-HSL compared to Fe2O3/PANI-DBSA, indicating its potential for enhanced detection capabilities in this context. Stability tests revealed ZnO/PANI-DBSA's superior stability over Fe2O3/PANI-DBSA, with both sensors retaining approximately 85–90% of their initial current after 1 month, demonstrating remarkable reproducibility and durability. [ABSTRACT FROM AUTHOR]

Optimal design for pipelines layout is gaining further importance because of the increase in demand on oil and gas products. Due to the crucial importance of pipelines design, the need for optimization of pipelines layout and pipeline networks has acquired the attention of operators and practitioners. Shortest path optimization schemes of pipelines need new assessment to find the optimal solution for real-world topologies. In this paper, three optimal path planning techniques—breadth-first search (BFS), A-star (A*), and artificial potential field (APF)—are compared and introduced to the field of choosing pipelines layout. Although these three techniques are successfully used in other applications, such as robotics and self-driving vehicles, a benchmark study is required to determine the most suitable technique out of these three techniques for pipelines placement application. In this work, a comparison between the three techniques was applied on three types of maps represented different degrees of difficulties, simple, medium, and complex, to choose the optimal technique. Also, these techniques were applied on a real-world problem considering real topologies and complex obstacles. Results of this work show the superiority of the APF algorithm with respect to finding the more realistic, shortest path and taking the lowest computational time. However, the application on real-world problems shows some limitation of this technique due to local minimum problem. The test of the A* algorithm shows moderate computational time and moderate generated path with regard to length. Practical Applications: Shortest path planning is usually related to minimizing cost of construction and operation of pipelines. In this work, the objective was to provide practitioners and field engineers with a tool to choose the shortest path for pipelines. Usually, pipelines are designed without considering the shortest path but to prevent geographical obstacles. This work used three path planning techniques, A* , BFS and APF algorithms, to create pipeline paths on various geographical difficulty-level maps. These techniques were appraised in other fields of research but were not compared to solve path planning problems. The results of this work are used to complete the path planning from oil and gas wells to the production and test manifolds and from manifolds to the early production facility (EPF). Further work is currently being done to obtain a software that performs this design and the cost calculations to obtain a realistic pipeline path on all type of maps. [ABSTRACT FROM AUTHOR]

Unprecedented levels of seismicity have been seen in southern Sichuan, China, since the large‐scale exploitation of shale gas. Fluid and pore pressure transported through hydrological channel are thought as pivotal elements in the induction of earthquakes. Our high‐resolution tomography results reveal two inclined seismic anomalies featured by low Vs and high Vp/Vs at different depth range. The deeper anomaly extends 15 km from NE to SE and connects the well g048 from 3 km depth to the vicinity of the Ms 4.7 Gongxian earthquake 5.4 km deep, which is hinted to be a hydrological channel inferred from the high fluid overpressure of 28 Mpa calculated from focal mechanism solution. The injection operation of multiple shale gas wells along the channel may potentially accumulate the pore pressure and cause the fault near the end of the channel to reach critical stress state through various mechanisms. Plain Language Summary: Increasing seismicity in southern Sichuan is suspected to be linked to hydraulic fracturing stimulation for shale gas extraction. Induced earthquakes resulting from fracturing operations at nearby wells can be verified using in‐situ fracturing data, while remote‐induced factors are hard to prove. In this study, a seismic anomaly of low Vs and high Vp/Vs inferred to be a long‐distance hydrological channel connecting the 2021 Ms 4.7 Gongxian earthquake to the active shale gas well 15 km away. Our results indicate that pore fluid pressure generated by hydraulic fracturing in multiple wells may continuously accumulated at the end of the channel, ultimately resulting in high pore pressure and triggering the fault rupture. Therefore, it is urgent to plug this channel and prevent the filtration loss. Key Points: Two long‐distance hydrological channels were observed in southern SichuanThe injection operation of multiple wells along the channel may increase the pore pressure in the hydrological channelThe accumulation of pore pressure at the end of the hydrological channel was confirmed by the occurrence of Ms 4.7 Gongxian earthquake [ABSTRACT FROM AUTHOR]

Velocity string (VS) is one of the most common methods to unload water in gas-producing field. In order to understand the behavior affecting production rate, we obtained several parameters including well completion, gas well production data, gas liquid ratio (GLR) and pressure data at tubing and casing head pressure, flowing bottom hole pressure. We then explore the relationship between these parameters against reservoir pressure and perform sensitivity analysis using multiphase steady-state flow simulator to analyze the parameters are the most sensitive to gas production rate. The results show that: (1) at larger inner diameter of the VS, there is a certain increase trend of gas production of gas wells. However, the production rate does not show a linear increase relationship with the larger internal diameter. It will reach certain inflection point before it decreases; (2) the gas production of the VS well is mainly driven by the reservoir pressure, the higher the reservoir pressure, the greater the gas production; (3) the root cause of relatively low initial production rate after small inner diameter coiled tubing VS installation is categorized as an abnormal well startup. This study provides theoretical support for selecting the optimum size and depth of VS to maintain well productivity. [ABSTRACT FROM AUTHOR]

Accurate well productivity prediction plays a significant role in formulating reservoir development plans. However, traditional well productivity prediction methods lack accuracy in tight gas reservoirs; therefore, this paper quantitatively evaluates the correlations between absolute open flow and the critical parameters for Linxing tight gas reservoirs through statistical analysis. Dominant control factors are obtained by considering reservoir engineering theories, and a novel machine learning-based well productivity prediction method is proposed for tight gas reservoirs. The adaptability of the productivity prediction model is assessed through machine learning and field data analysis. Combined with the typical decline curve analysis, the estimated ultimate recovery (EUR) of a single well in the tight gas reservoir is forecasted in an appropriate range. The results of the study include 10 parameters (such as gas saturation) identified as the dominant controlling factors for well productivity and geological factors that impact the productivity in this area compared to fracturing parameters. According to the prediction results of the three models, the R2 of Support Vector Regression (SVR), Back Propagation (BP), and Random Forest (RF) models are 0.72, 0.87, and 0.91, respectively. The results indicate that RF has a more accurate prediction. In addition, the RF model is more suitable for medium and high-production wells based on the actual field data. Based on this model, it is verified that the productivity of low-producing wells is affected by water production. This study confirms the model's reliability and application value by predicting recoverable reserves for a single well. [ABSTRACT FROM AUTHOR]

Hydraulic fracturing is an essential technology in the development of coalbed methane reservoirs. Hydraulic fracturing can create a highly conductive fracture in the reservoir and increase its permeability. At present, the focus of coalbed methane reservoir fracturing optimization is gradually shifting to the fracturing scale. In the current development process, more and more coalbed methane blocks try to increase the fracturing scale to increase the gas production of coalbed methane wells. Field tests show that gas production of coalbed methane wells will increase to a certain extent with the increase of fracturing scale. However, the increase in the scale of fracturing also increases its cost. Therefore, the most economical fracturing scale is not necessarily the optimal fracturing scale for gas production. The field test usually pays more attention to the gas production effect, but the development of a coalbed methane field should pay more attention to the economic benefit, and the optimization of fracturing should take the economic benefit as the goal. Taking economic benefits as the starting point, this paper uses fracturing simulation to calculate the fracture extension under different geological conditions and different fracturing scales. It also uses numerical simulation to calculate the gas well productivity under different fracture extension conditions. The economic evaluation model was established to calculate the economic benefits under different fracturing scales, and the optimal fracturing scale was obtained. Finally, the typical maps of fracturing optimization under different geological conditions are formed. The optimization method of fracturing scale integrating economy, fracturing, and gas reservoir is realized. The research results have been successfully applied to the optimization scheme of Liulin block development, and very good results have been achieved. Because this method is targeted at different geological conditions, it can be used to guide the fracturing optimization of other coalbed methane blocks and has very important significance for the development and optimization of coalbed methane reservoirs. [ABSTRACT FROM AUTHOR]

Coalbed methane (CBM) seepage is a significant geological factor affecting the capacity of CBM wells. Using the example of the Qinnan-East Block of the Qinshui Basin, in this work, the CBM seepage law under different in situ stresses, coal reservoir pressures, and temperatures is systematically analyzed using on-site well test data. A permeability calculation model that includes the coal reservoir stress, pressure, and temperature is established, and the coal permeability and its control mechanism under the action of multiple fields are revealed. The results demonstrate that the in situ stress, pressure, and temperature in the study area increase linearly with increasing depth. The coal reservoir geothermal gradient is 0.72–2.11 °C/100 m, and the mean value is 1.67 °C/100 m. The coal reservoir geothermal gradient rises with an increasing depth as a logarithmic function. The permeability of the coal reservoir is 0.01–0.20 × 10−3 μm2, the mean value is 0.05 × 10−3 μm2, and the CBM seepage under the action of multiple physical fields is relatively low. With increasing effective stress and temperature, the permeability continuously decreases following a negative exponential function. The CBM seepage is tightly bound to the fracture aperture and is controlled by the change in the in situ stress, the pore fluid pressure, and the temperature stress. [ABSTRACT FROM AUTHOR]

Cement-based cementing materials have some disadvantages, such as high brittleness and poor mechanical properties. In the long-term production process of oil and gas wells, it is easy to damage, resulting in annulus pressure and interlayer channeling. However, curable resin-based cementing materials have the advantages of good toughness, high strength, and low elastic modulus, and have the potential as cementing materials. A water-based epoxy resin cementing fluid system suitable for cementing was obtained in this article, which has good toughness and high strength, and can directly replace cement slurry for cementing. When the temperature was 50 °C and 70 °C, the fluidity of water-based epoxy resin cementing fluid system was greater than 18 cm, and the thickening time was 74 minute and 128 minute, respectively. The 28 day compressive strength of the resin cured at 70 °C increased by 276.3% and the tensile strength increased by 117.9% compared with the blank cement paste. Scanning electron microscope test indicated that the matrix of water-based epoxy resin is denser than that of blank cement paste. Fourier transform infrared spectrometer and X-ray diffraction analyses demonstrate that the cured epoxy resin products are not affected by curing age. According to the thermogravimetric results, epoxy resin can be used in high temperature deep well. On the whole, replacing cement with water-based epoxy resin cementing fluid can improve the cementing quality, which has broad application value. [ABSTRACT FROM AUTHOR]

The casing deformation prevention technology based on the optimization of cement slurry is proposed to reduce the casing deformation of shale oil and gas wells during hydraulic fracturing. In this paper, the fracture mechanism of hollow particles in cement sheath was firstly analyzed by discrete element method, and the effect of hollow particles in cement on casing deformation was investigated by laboratory experiment method. Finally, field test was carried out to verify the improvement effect of the casing deformation based on cement slurry modification. The results show that the formation displacement can be absorbed effectively by hollow particles inside the cement transferring the excessive deformation away from casing. The particles in the uncemented state provide deformation space during formation slipping. The casing with diameter of 139.7 mm could be passed through by bridge plug with the diameter of 99 mm when the mass ratio of particle/cement reaches 1:4. According to the field test feedback, the method based on optimization of cement slurry can effectively reduce the risk of casing deformation, and the recommended range of hollow microbeads content in the cement slurry is between 15% and 25%. [ABSTRACT FROM AUTHOR]

The severe health risk associated with elevated levels of indoor radon gas is well known and widely reported. Measuring residential indoor radon-in-air levels is expensive, labour- and time-intensive. Two of the most important estimators of high levels of indoor radon gas are the underlying geology of an area and the climatic conditions, especially temperature and wind. While varying geology leads to different exhalation rates of radon gas, the climate can mitigate or enhance indoor radon gas levels. The research in this study developed and tested a novel approach to rapidly identify the most probable areas of high indoor radon levels, potential targets for indoor radon measurements. The study utilizes GIS tools to superimpose overlays of geology, climate, and wind to identify possible radon hotspots. South Africa was selected as a study site due to its varying climatic conditions and unique geology which have large areas of underlaying uranium-bearing rock units. Several of the identified hotspots were compared to actual indoor radon measurements, and a good similarity between actual and estimated indoor radon levels was found. This method can easily be applied to other sites or regions, giving it both practical and theoretical values. [ABSTRACT FROM AUTHOR]

Velocity string (VS) is one of the most common methods to unload water in gas-producing field. In order to understand the behavior affecting production rate, we obtained several parameters including well completion, gas well production data, gas liquid ratio (GLR) and pressure data at tubing and casing head pressure, flowing bottom hole pressure. We then explore the relationship between these parameters against reservoir pressure and perform sensitivity analysis using multiphase steady-state flow simulator to analyze the parameters are the most sensitive to gas production rate. The results show that: (1) at larger inner diameter of the VS, there is a certain increase trend of gas production of gas wells. However, the production rate does not show a linear increase relationship with the larger internal diameter. It will reach certain inflection point before it decreases; (2) the gas production of the VS well is mainly driven by the reservoir pressure, the higher the reservoir pressure, the greater the gas production; (3) the root cause of relatively low initial production rate after small inner diameter coiled tubing VS installation is categorized as an abnormal well startup. This study provides theoretical support for selecting the optimum size and depth of VS to maintain well productivity. [ABSTRACT FROM AUTHOR]

As the development of well types for low permeability reservoirs shifts from vertical to highly inclined/horizontal wells, targeted studies of oil and gas reservoir damage must be conducted for such well types to improve the science and effectiveness of acidification conversion. Taking into account the formation of mud cake and the dynamic damage factors caused by drilling fluid on the reservoir during horizontal well drilling, a refined dynamic description model for nonuniform damage in horizontal wells was established. The coupled simulation accounts for the dynamical destruction of the skin factor of the reservoir and the dynamical generation of the slurry. The coupled model consists of a radial mud cake dynamic formation model, a reservoir damage radius model, a permeability distribution model, and a horizontal well inhomogeneous skin factor model. It captures the dynamic evolution of reservoir damage due to drilling fluid contamination during horizontal well drilling and provides a real‐time representation of changes in the reservoir skin factor of horizontal wells, measuring the depth and extent of radial reservoir damage. Clarifying the extent of reservoir damage and its impact in horizontal well sections can help select appropriate acidification methods, improve acid distribution processes, and ultimately improve the effectiveness of mitigating reservoir damage and increasing oil and gas well productivity. [ABSTRACT FROM AUTHOR]

Ecologists strive for laws that explain interactions between organisms. Myriad hypotheses have been fundamental in increasing our understanding of plant–herbivore interactions, including the forage maturation hypothesis (FMH). The FMH has recently been extended to include contingencies of body size and digestive system: selection for greater energy potential should be negatively correlated with body mass and selection for proximity to surface water should be greater for hindgut fermenters compared to foregut fermenters or ruminants. While these general trends hold at a broad scale, intrapopulation variability still exists. For feral species that did not coevolve within their current ecological context, variability in habitat selection among populations may be greater. Consequently, understanding habitat selection of each population is imperative to properly inform management. For the case of feral horses, Equus ferus caballus , a large-bodied hindgut fermenter, understanding how they compare in habitat selection to sympatric species is of particular interest due to habitat alteration and potential competition. Across much of their range in western North America, horses are sympatric with the smaller-bodied ruminant pronghorn, Antilocapra americana. The two species overlap in space use, but we lack information on how each species selects resources within areas of overlap. Accordingly, we compared habitat selection between these two species during the growing season to understand how each responded to predictions of the FMH and to better guide potential management actions. Horses followed FMH predictions by selecting proximity to surface water and greater forage biomass. Meanwhile, pronghorn did not follow predictions of the FMH; pronghorn selected greater forage biomass but did not select greater energy potential. Both species selected greater herbaceous cover, flatter slopes and farther distances from oil and gas well pads. Our analysis reveals a high degree of selection overlap and underscores the importance of conducting population level studies to best understand how herbivores interact with the unique environments they inhabit. • We compared habitat selection of feral horses and pronghorn in an arid shrubland. • We assessed responses to predictions of the forage maturation hypothesis (FMH). • Feral horses selected proximity to surface water, following FMH predictions. • Pronghorn did not select greater energy potential, deviating from FMH predictions. [ABSTRACT FROM AUTHOR]

The coupling relationship between the deformation field, the diffusion field, and the seepage field is an important factor in fluid transport mechanisms in the long-term coalbed methane (CBM) exploitation process. A mathematical model of gas–water two-phase fluid–structure coupling in a double-porosity medium in coal reservoirs is established in this paper. Taking Hancheng Block, a typical production block in Qinshui Basin, as the geological background critical desorption pressure, reservoir permeability anisotropy is considered in the model. COMSOL Multiphysics (COMSOL_6.0) was used to create the model. The accuracy and rationality of the model were verified by comparing field production data with the results of the simulation. Using the simulation, the influence law of various reservoir geological characteristics parameters (Langmuir strain constant, ratio of critical desorption pressure to reservoir pressure of coal seam (CDPRP), elastic modulus, initial water saturation, Langmuir pressure, etc.) on CBM productivity, reservoir pressure, and permeability ratio was discussed, and a thorough analysis of the factors affecting productivity was obtained using the orthogonal test method. The findings of this study indicate that the change in permeability is the result of the superposition effect of many factors. Different stages of drainage have different primary regulating factors. Rock skeleton stress has a consequence on coal matrix permeability in the early drainage stage, and coal matrix shrinkage is primarily impacted in the later drainage stage. Besides the initial water saturation, other reservoir geological parameters (e.g., CDPRP, Langmuir volume, Langmuir strain constant, elastic modulus) have a strong relationship with productivity. When the value of coal geological parameters increases, the degree of productivity release is higher (as the initial water saturation increases, the production decreases correspondingly). Different coal and rock parameters have varying levels of impact on the drainage stage of CBM wells. The influences of the CDPRP, Langmuir volume, Langmuir strain constant, and elastic modulus on gas production are mainly concentrated in the initial and intermediate drainage stages and begin to fall off during the last drainage stage. Per the multi-factor analysis, the main coal–rock parameters affecting the productivity release are the Langmuir strain constant, followed by the CDPRP and other parameters. The analysis findings can offer theoretical guidance for CBM well selection and layer selection and enhance the block's overall CBM development level. The improved productivity prediction model for CBM, which is based on fluid–structure coupling theory, can offer a new technical benchmark for CBM well productivity prediction. [ABSTRACT FROM AUTHOR]

Purifying olefin from ternary paraffin/olefin/alkyne mixtures through a one‐step adsorption process is extremely desirable. Herein, a stable zirconium(IV) metal‐organic framework with a customized pore surface composed of nonpolar phenyl and slightly polar thiophene rings is reported to access the adsorption preference of paraffin and alkyne over olefin. Noteworthily, this material displays a superior ability to discriminate C3 hydrocarbon molecules, which is principally more challenging compared with C2 ones and rarely documented. Computational studies disclose that its featured pore shape fits well with C3 gas molecules, enabling them to get close contact with the immobilized affinity sites. Leveraging surface chemistry and pore shape engineering synergistically gives rise to excellent C3 adsorption capacities (>5 mmol g−1) and concurrently high C3H8/C3H6 (1.4) and C3H4/C3H6 (1.9) selectivities (at 298 K and 1 atm). Dynamic column breakthrough experiments demonstrate that one‐step purification of C2H4 and C3H6 can be simultaneously realized on this material. [ABSTRACT FROM AUTHOR]

Horizontal well development of natural gas hydrate (NGH) can greatly improve gas production and make it cost-effective, which is one of the key technologies for the efficient development of NGH in the future. World widely, there is only limited experience in drilling horizontal wells into gas hydrate sediments, which lacks certain reference. In this paper, the practice of drilling horizontal wells into gas hydrate sediments, were analyzed the challenges. The challenges encountered when drilling horizontal wells into hydrate sediments were also analyzed. At least, the application of horizontal wells and complex well structure, which based on horizontal wells are analyzed. The advantages and disadvantages of several novel well structure are compared. This paper will contribute to the development of natural gas hydrate of our country. [ABSTRACT FROM AUTHOR]

Coalbed methane (CBM) can be recovered more effectively through heat injection mining. The slippage effect in coal becomes more significant as CBM is exploited, essential for maintaining consistent production of CBM wells. By "slippage effect," we mean that gas molecules exhibiting non–zero velocity near the wall surface of coal pores, leading to higher gas permeability than liquid permeability. To explore the slippage effect and its control mechanism during heat injection mining, methane seepage experiments with constant effective stress were conducted under five different temperatures and seven pore pressures. An analysis was conducted on the mechanisms by which pore pressure and temperature affect gas slippage effect. Furthermore, the correlation between coal pore structure and the gas slippage effect was revealed using the nuclear magnetic resonance (NMR) technique. The results appear that, first, as pore pressure increases, the slippage effect is suppressed due to the influence of the average molecular free path, despite the positive impact of adsorption–induced matrix expansion. Second, as temperature rises, the average molecular free path and thermal expansion have a positive impact on gas slippage, while matrix shrinkage caused by desorption has a negative impact. The positive impact is stronger, resulting in a continuous enhancement of the slippage effect. Finally, a new slippage factor calculation based on NMR T2 distribution of micropores and transitional pores (<100 nm, T2 < 8.33 ms) was provided, and the method was verified by slippage factor fitted by permeability experimental data. The heat injection mining of CBM can be theoretically guided by the research results. [ABSTRACT FROM AUTHOR]

This paper takes the huff and puff development of multi-component thermal fluid as the main research object, based on the reservoir characteristics of multi-component thermal fluid in the development of heavy oil, through searching relevant literature and carrying out formation simulation experiments of multi-component thermal fluid core displacement, cavitation water jet rock breaking and other experiments, it is found that the dissolution of high-temperature components of multi-component thermal fluid, cavitation, viscosity reduction, and composition changes of multi-component thermal fluid will lead to reservoir sand production. Furthermore, through the sand production simulation experiment of multi-component thermal fluid huff and puff, it is found that the soaking time is the main factor affecting sand production. In view of the multi-round characteristics of huff and puff development, multi-round sand production simulation experiments are also carried out in this paper. In view of the multi-round characteristics of huff and puff development, multiple rounds of sand production simulation experiments were carried out. As the huff and puff rounds change, the influence of various factors on sand production becomes more and more obvious, that is, temperature has the strongest influence, and injection speed is the second. In short, the pressure is the weakest. This study is helpful to guide fine sand control, set up a reasonable production and mining system, and play a very important role in prolonging the life of oil and gas wells and improving economic benefits. [ABSTRACT FROM AUTHOR]

Aiming at the problem that the suction chamber of the gas‐driven jet pump has insufficient mixing of the power gas and the sucked fluid leading to efficiency reduction, this study proposes to effectively combine the static mixer with the annular jet pump and design a new type of annular jet pump and apply it to the gas wells to improve the fluid recovery capacity. Numerical simulations based on the gas–liquid two‐phase flow model are carried out for a conventional annular jet pump (CAJP) and a new annular jet pump (NAJP). The reliability of the simulation results is verified by gas–liquid two‐phase flow experiments, and the differences between the two in terms of velocity, pressure loss, and turbulent kinetic energy are analyzed. Meanwhile, the validity of NAJP is verified, and the effects of different structures such as static mixer torsion angle, suction chamber angle, and area ratio on the performance of NAJP are analyzed. The results show that NAJP enhances the degree of mixing between the sucked fluid and the power gas through the cyclonic effect created by the static mixer compared with CAJP. It results in a 10.6% year‐on‐year increase in the velocity of the sucked fluid, a 3% year‐on‐year increase in the pressure drop, and a 12.2% year‐on‐year increase in efficiency. NAJP can significantly improve the fluid‐carrying performance. With a mixer angle of 210°, a suction chamber angle of 21°, and an area ratio of 1.77, the NAJP achieves an efficiency of 39.7%, which is a year‐on‐year increase of 7.3% compared to the structure under the same conditions before optimization. This study lays a foundation for the determination of the optimal design scheme of the annular jet pump and at the same time can provide theoretical and technical support for researchers in related fields. [ABSTRACT FROM AUTHOR]

The Permian Longtan Formation in the Songzao coalfield, Southwest China, has abundant coalbed methane (CBM) stored in high-rank coals. However, few studies have been performed on the mechanism underlying the differences in CBM gas content in high-rank coal. This study focuses on the characterization of coal geochemical, reservoir physical, and gas-bearing properties in the coal seams M6, M7, M8, and M12 based on the CBM wells and coal exploration boreholes, discusses the effects of depositional environment, tectono-thermal evolution, and regional geological structure associated with CBM, and identifies major geological constraints on the gas-bearing properties in high-rank coal. The results show that high-rank coals are characterized by high TOC contents (31.49~51.32 wt%), high Tmax and R0 values (averaging 539 °C and 2.17%), low HI values (averaging 15.21 mg of HC/g TOC), high porosity and low permeability, and high gas-bearing contents, indicating a post-thermal maturity and a good CBM production potential. Changes in the shallow bay–tidal flat–lagoon environment triggered coal formation and provided the material basis for CBM generation. Multistage tectono-thermal evolution caused by the Emeishan mantle plume activity guaranteed the temperature and time for overmaturation and thermal metamorphism and added massive pyrolytic CBM, which improved the gas production potential. Good geological structural conditions, like enclosed fold regions, were shown to directly control CBM accumulation. [ABSTRACT FROM AUTHOR]

Pump-rate regulation is frequently used during hydraulic fracturing operations in order to maintain the pressure within a safe range. An emergency pump-rate reduction or pump shutdown is usually applied under the condition of sand screen-out when advancing hydraulic fractures are blocked by injected proppant and develop wellhead overpressure. The drastic regulation of the pump rate induces water-hammer effects—hydraulic shocks—on the wellbore due to the impulsive pressure. This wellbore shock damages the well integrity and then increases the risk of material leakage into water resources or the atmosphere, depending on the magnitude of the impulsive pressure. Therefore, appropriate emergency pump-rate regulation can both secure the fracturing operation and enhance well-completion integrity for environmental requirements—a rare mutual benefit to both sides of the argument. Previous studies have revealed the tube vibration, severe stress concentration, and sand production induced by water-hammer effects in high-pressure wells during oil/gas production. However, the water-hammer effect, the induced impulsive pressures, and the mitigation measures are rarely reported for hydraulic fracturing injections. In this study, we present a data-driven workflow integrating real-time monitoring and regulation strategies, which is applied in four field cases under the emergency operation condition (screen-out or near screen-out). A stepwise pump-rate regulation strategy was deployed in the first three cases. The corresponding maximum impulsive pressure fell in the range of 3.7~7.4 MPa. Furthermore, a sand screen-out case, using a more radical regulation strategy, induced an impulsive pressure 2 or 3 times higher (~14.7 MPa) than the other three cases. Compared with the traditional method of sharp pump-rate regulation in fields, stepwise pump-rate regulation is recommended to constrain the water-hammer effect based on the evolution of impulsive pressures, which can be an essential operational strategy to secure hydraulic fracturing and well integrity, especially for fracturing geologically unstable formations (for instance, formations near faults). [ABSTRACT FROM AUTHOR]

The finite-element method is applied for the numerical simulation of gas filtration in porous inhomogeneous media. The model is based on the fractional derivatives with respect to time in terms of the Grünvald–Letnikov operator. The results of numerical analyses are verified by comparing with real-life empirical data on physical and geometric parameters to reveal their excellent agreement. [ABSTRACT FROM AUTHOR]

In the process of constructing deep natural gas wells in Sichuan and Chongqing, gas wells encounter various technical challenges such as high temperature, high pressure, and a corrosive environment containing H2S and CO2. The corrosion of rubber materials in these acidic environments can easily lead to seal failure in downhole tools. To better investigate the corrosion resistance of rubber materials in acidic environments, we utilized a dynamic cyclic corrosion experimental device capable of simulating the service conditions experienced by downhole tools under high-temperature, high-pressure multiphase flow. Corrosion-resistance tests were conducted on fluororubbers (FKM) 1, 2, 3, and HNBR (hydrogenated nitrile-butadiene rubber) under acidic conditions (80 °C and 160 °C), along with sealing corrosion tests on O-rings. These tests aimed to analyze the mechanical properties, hardness, and corrosion resistance before and after exposure to acid media as well as the sealing performance of O-rings. Ultimately, our goal was to identify suitable rubber materials for acidic pressure environments. Experimental results revealed that all four types of rubber exhibited decreased elongation at break after undergoing corrosion testing; however, fluororubber 3 demonstrated significant susceptibility to temperature effects while the other three types showed minimal impact from temperature variations. Fluororubber 1 and fluororubber 3 displayed substantial deformation levels whereas mechanical properties greatly deteriorated for fluororubber 2. Overall, HNBR showcased superior comprehensive performance. [ABSTRACT FROM AUTHOR]

Wellhead chokes play key roles in liquid-flowback and gas-production processes of hydraulically fractured shale-gas wells. The characteristic of choke flow is quite complex and involves many factors, such as choke size, pressure and liquid-gas ratio (LGR). Gilbert-type correlations have been widely used in choke flow studying, but they are empirical and their accuracy is easily affected by operational conditions or special reservoir properties. Therefore, it is worth paying attention to the applicability of Gilbert-type correlation. This paper collected over 10,000 sets of data from 12 shale gas wells in Changning region, analyzed the influence of LGR on the prediction accuracy of Gilbert-type correlations, and developed a new correlation named Piecewise Gilbert-type Correlation (PGC) for gas-liquid two-phase flow through chokes. The results showed that LGR had a great impact on the prediction accuracy, and therefore the LGR data during the flowback period could be divided into several stages for data-fitting separately. PGC was established on multiple LGR stages, which led to multiple different groups of empirical coefficients, and had been proved to be more accurate on the whole. Specifically, the overall error and the mean error of PGC for the testing data were reduced to 13.3 and 0.0839. [ABSTRACT FROM AUTHOR]

The field of nanotechnology has shown promise in addressing major problems and improving drilling effectiveness. An overview of the difficulties encountered during oil and gas well drilling operations and the demand for creative solutions opens the debate. This review explores how nanotechnology is transforming the oil industry and enhancing performance as a whole. The evaluation of the uses of nanotechnology for better oil recovery, real-time monitoring, innovative materials, drilling fluids, and reservoir characterization are extensively discussed in this review. The primary function of additives is to improve the fundamental characteristics of drilling fluids. The variety of fluid additives available is a reflection of the complex drilling–fluid systems that are currently being used to enable drilling in increasingly difficult subsurface conditions. Common additives used in water- and oil-based drilling fluids include lubrication, shale stability, filtration control, rheology control, viscosification, and pH regulation. Drilling fluids frequently contain filtration control additives such as starch, polyanionic cellulose (PAC), carboxymethyl cellulose (CMC), and nanoparticles (NP). Commonly used rheology-modifier additives are xanthan gum, carboxymethyl cellulose, guar gum powder, and, more recently, salt-responsive zwitterionic polymers that were used as viscosifiers to water-based drilling fluids. The three main additives that regulate pH are citric acid monohydrate, potassium hydroxide, and sodium hydroxide. Additives that stabilize shale, such as potassium and sodium salts and asphaltenes, are often used. A wide range of materials are included in the category of lubricating additives, including polymers, asphaltenes, glass beads, oils of various grades, and oil-surfactants. Various fibrous materials, including wood, cotton, fibrous minerals, shredded tires from vehicles, and paper pulp, are used as additives to control circulation. Furthermore, shredded cellophane, bits of plastic laminate, plate-like minerals like mica flakes, granulated inert materials such as nut shells, and nano-polymers are used in wellbores to reduce fluid loss. The incorporation of nanoparticles into drilling fluids has produced upgraded fluids with better features, including improved lubricity, thermal stability, and filtering capacities. These developments aid in lowering friction, enhancing wellbore stability, and enhancing drilling efficiency. This paper also emphasizes how nanotechnology has made enhanced drilling equipment and materials possible. Drilling equipment's longevity and performance are increased by nanocomposite materials that have been reinforced with nanoparticles due to their improved mechanical strength, wear resistance, and thermal stability. Advanced reservoir characterisation tools, including nanoparticle tracers and nanoscale imaging methods, can help locate the best drilling sites and increase production effectiveness. On the other hand, nanofluids and nanoemulsions can potentially increase oil recovery because they enhance fluid mobility, lower interfacial tension, and alter rock wettability. Although nanotechnology has many advantages, there are also issues that need to be resolved. For an implementation to be effective, factors including nanoparticle stability, dispersion, and potential environmental effects must be carefully taken into account. This review highlights the need for future research to create scalable manufacturing procedures, improve nanoparticle behaviour, and determine nanomaterials' long-term environmental effects. In conclusion, this in-depth analysis illustrates the use of nanotechnology in transforming the process of drilling oil and gas wells. [ABSTRACT FROM AUTHOR]

Different from conventional gas reservoirs, the permeability of coalbeds is affected by stress sensitivity and matrix shrinkage during production. These two conditions lead to lower permeability in the reservoir and affect the production efficiency of the gas well. In addition, coalbed methane wells have single-phase water flow in the initial stage of production. When the reservoir pressure is reduced to its critical desorption pressure, the adsorbed gas in the reservoir desorbs into the pore space and participates in the flow. The flow state in the reservoir changes from single-phase to two phase, and the permeability of the reservoir decreases. The occurrence of these three damage mechanisms is related to the flow rate of fluid in the reservoir. At present, there is a lack of research on the optimization of drainage and production systems considering the damage mechanism of coal reservoirs. This study comprehensively considers how to optimize the production rate of coal reservoirs under the influence of stress sensitivity, matrix shrinkage and two phase flow in the production process to achieve the purpose of production with the least damage to the reservoir. [ABSTRACT FROM AUTHOR]

Indonesia has natural gas reservoirs with high CO 2 content, such as Natuna and Bojonegoro gas fields. Various technologies have been developed, including cryogenic distillation separation technology suitable for application to gas wells with high CO 2 content. Cryogenic distillation separates CO 2 with high purity according to the operating conditions and the CO 2 dew point. Cryogenic distillation was simulated in this study to determine the purity of the CO 2 and to compare the economic potential of each approach. The highest CO 2 purity using CFZ technology is 98.72% in the Natuna, while the highest purity of CH 4 using Pellegrini Distillation technology is 99.95% in the Bojonegoro. Economically, the Natuna and Bojonegoro estimates using the CFZ technology have a lower total annual cost than the Pelegrini distillation. However, CFZ technology has a lower CO 2 capture cost than Pellegrini Distillation technology, 7.9 USD/tonne CO 2 and 10.26 USD/tonne CO 2. In other words, separation using the CFZ technology is more effective for gas fields with higher CO 2. [Display omitted] • Indonesia has two gas fields with high CO 2 content such as Natuna and Bojonegoro. • Cryogenic technology is most economical for gas field with high CO 2 content. • CFZ concept involves the controlled freezing of CO 2 in a specially designed column. • CO 2 capture cost for CFZ lower than Pellegrini Distillation in both gas fields [ABSTRACT FROM AUTHOR]