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Nowadays, there has been a recognition of the remarkable potential of nanofluids and microorganisms as eco-friendly agents for enhanced oil recovery. on the other hand, one of the unique strategies for boosting hydrocarbon recovery is altering the wettability of the rock surface of oil and gas reservoirs. Herein, a nanohybrid that combines graphene oxide (GO) and silica (SiO2) was synthesized using a low-temperature, facile, and eco-friendly approach (sol-gel). GO-SiO2 nanocomposite was characterized with the aid of XRD, SEM, and FTIR analyses. Afterward, Nanofluids with different concentrations (0.005, 0.01, 0.015, and 0.02 wt%) of GO-SiO2 nanocomposite at various ratios (1:1, 1:2, and 2:1) were prepared using a surfactant-free and pH-neutral approach with a salinity of 30,000 ppm. The results of the Zeta potential measurement reveal that the manufactured nanofluids have great stability and the ratio of 1:1 was the most effective ratio for improving the reservoir wettability change from oil-wet to water-wet. At a higher temperature of 80 °C compared to the ambient condition of 25 °C, a more significant change in wettability was observed (23° to 161°). At the optimal concentration of nanofluid (0.015 wt%), the contact angle increased from 23° (on a non-treated surface) to 161°. These findings suggest that GO-SiO2 has great potential as an affordable, flexible, and environmentally friendly natural nanofluid, particularly under harsh conditions for the EOR process. [ABSTRACT FROM AUTHOR]

Fault-block gas reservoirs are dominated in the K Gas Field, Xihu Sag, East China Sea Shelf Basin. Research on the effectiveness of fault-block traps is lacking. A quantitative method for the evaluation on the effectiveness of fault-block traps has been developed in the study. Based on the core test, logging and geophysical data, detailed depiction and trap effectiveness research were conducted on the pools of the gas field. Anticline traps, lithological traps and mudstone-correspondent traps are effective traps with high probability of reservoir formation, while sandstone-correspondent traps are the least effective with 35% probability of effective traps. Twenty-one drilling wells in the K Gas Field show that when the fault displacement pressure is less than the reservoir displacement pressure, the trap is non-effective, which matches the result 92% of traps without oil and gas. On the contrary, the trap is effective, which matches the result 100% of gas reservoirs. The discrimination diagram of fault-block trap effectiveness can quickly identify trap effectiveness and contribute to fault-block oil and gas exploration in K Gas Field. The method has a wide application potential for the exploration of fault-block reservoirs in other areas. [ABSTRACT FROM AUTHOR]

Fault-block gas reservoirs are dominated in the K Gas Field, Xihu Sag, East China Sea Shelf Basin. Research on the effectiveness of fault-block traps is lacking. A quantitative method for the evaluation on the effectiveness of fault-block traps has been developed in the study. Based on the core test, logging and geophysical data, detailed depiction and trap effectiveness research were conducted on the pools of the gas field. Anticline traps, lithological traps and mudstone-correspondent traps are effective traps with high probability of reservoir formation, while sandstone-correspondent traps are the least effective with 35% probability of effective traps. Twenty-one drilling wells in the K Gas Field show that when the fault displacement pressure is less than the reservoir displacement pressure, the trap is non-effective, which matches the result 92% of traps without oil and gas. On the contrary, the trap is effective, which matches the result 100% of gas reservoirs. The discrimination diagram of fault-block trap effectiveness can quickly identify trap effectiveness and contribute to fault-block oil and gas exploration in K Gas Field. The method has a wide application potential for the exploration of fault-block reservoirs in other areas. [ABSTRACT FROM AUTHOR]

As unconventional oil and gas receive more and more attention, scholars pay more and more attention to waterless fracturing technology. Among them, carbon dioxide fracturing technology, as the main representative of waterless fracturing technology, has unique advantages and broad application prospects in the development of unconventional oil and gas reservoirs. However, when using carbon dioxide fracturing fluid for construction, carbon dioxide is greatly affected by temperature and pressure, so it is necessary to simulate the temperature and pressure in the wellbore during carbon dioxide fracturing construction. In this article, the basic physical properties of carbon dioxide under different temperatures and pressures are analyzed, and the changes of wellbore temperature and pressure during carbon dioxide fracturing are studied based on the generalized heat conduction theory. The results show that the faster the injection rate of CO2 fracturing fluid at the wellhead, the lower the bottom hole temperature and the higher the bottom hole pressure. However, the higher the wellhead injection temperature, the higher the bottom hole temperature, and the lower the bottom hole pressure. [ABSTRACT FROM AUTHOR]

The magnitude versus offset (MVO) curve, a type of frequency domain marine controlled-source electromagnetic data, is the most common way to identify electromagnetic anomalies in oil and gas reservoirs. However, in actual exploration, it can be difficult to identify the boundary of the high resistance anomaly when there are response signals of multiple emission frequencies. Also, the noise would reduce the accuracy of manually detecting electromagnetic anomalies. The robustness of the bidirectional long short-term memory (LSTM) network is relatively strong, and the LSTM neural network would get the most out of the sequence information of the data for feature extraction purposes and to achieve automatic classification and identification. Therefore, this paper proposes a method of using bidirectional LSTM to solve the problem of anomaly identification in marine controlled-source electromagnetic data. The LSTM unit was applied to establish anomaly identification models of single-layer LSTM, two-layer LSTM, and bidirectional LSTM, respectively. In this paper, theoretical data were calculated by a one-dimensional uniform layered medium model, and the synthetic noise data were constructed by adding random noise with different signal-to-noise ratios. The three types of models were trained, verified, and tested, respectively, to compare the accuracy of electromagnetic anomaly identification. According to the comparison, a conclusion can be drawn that the bidirectional LSTM model suggests the best manifestation of learning the characteristics of the sample. Its electromagnetic anomaly identification accuracy reached 100% in the theoretical dataset and 79.58% in the synthetic noise dataset. [ABSTRACT FROM AUTHOR]

For tight oil and gas reservoirs to form complex fracture networks with high conductivity and repeated treatment of old wells, temporary plugging and diverting fracturing technology has become one of the important stimulation methods. Previous articles have been carried out on different types of temporary plugging agents in fracture pressure rise law and placement shape, but studies on the permeability of temporary plugging cakes are relatively lacking. In this paper, the pressure rise law of five kinds of temporary plugging agent is studied by conventional fracture simulation device, and the permeability properties of temporary plugging cakes are studied by original design manufactured porous medium device. The results show that there are some differences between the permeability of temporary plugging cakes and the formation of pressure-bearing plugging cakes, the permeability is related to the types of plugging cakes, and the pressure rising law is related to the type and particle size distribution of temporary plugging material. The maximum length of DA-1, DA-2, DA-3 and KMS-D aggregates is 2.93 cm, 5.83 cm, 6.73 cm and 6.00 cm, and the minimum aggregate permeability is 23.88 mD, 19.19 mD, 15.13 mD and 36.97 mD. [ABSTRACT FROM AUTHOR]

The coral reef pores are the main reservoir space of oil and gas resources. Through determining the structural form and distribution characteristics of pores, it can be helpful for scientific and reasonable stratigraphic division and reservoir evaluation, and provide basic data for the efficient development of using coral reefs as oil and gas reservoir sites. The core difficulty of interpretation and evaluation of coral reef pore structure and distribution characteristics is the pore recognition and feature extraction. In view of problems of low accuracy and efficiency in the recognition and feature extraction of coral reef pore at present, this paper proposes a method of coral reef pore recognition and feature extraction based on borehole image data. First of all, based on the borehole image and combined with the pore characteristics in borehole image, this paper proposes the coral reef pore recognition method. By using the feature of color gradient difference between the pore and the non pore in the borehole image, it realizes the segmentation of coral reef pore with low noise and weak interference. On the basis of obvious coral reef pores, the contour tracking method and image filling system of coral reef pore are established. Then, on the basis of traditional eight connected region marking algorithm, a pore region feature extraction method is proposed. The equivalent relationship between the temporary mark and the final mark is established, and an evaluation criterion that can comprehensively reflect the pore region feature parameters in the borehole image is formed. Finally, a systematic analysis and a comparison of results are carried out based on the actual coral reef borehole images. The results are consistent with the real values, which verifies the correctness of method. [ABSTRACT FROM AUTHOR]

Conventional drainage gas recovery and water-controlled gas recovery technologies are difficult to meet the needs of tight gas reservoirs. In order to solve this problem, nanofluid for drainage gas recovery was proposed to improve the effect of tight gas reservoir development. In this paper, the phase inversion method was used to prepare nanofluid with small particle size. Nanofluid could change the core surface characteristics, improve the drainage effect, and prolong its validity period. The influences of nanofluid on the gas-water flow in tight core and core surface properties have been systematically investigated by the experiments. The mechanism of the drainage gas recovery was discussed. The results showed that nanofluid with different mass concentrations can shift the isotonic point of gas-water relative permeability to the left (58.65%→54.78%@6.25 wt%, 56.49→54.66%@100wt%), reduce the irreducible water saturation (38.35→29.51%@6.25 wt%, 51.75→47.01%@100wt%), greatly increase the water relative permeability (63.79%@6.25 wt%, 100%@100wt%) and slightly reduce gas relative permeability (9.80%@6.25 wt%, 13.04%@100wt%), which has a significant drainage effect. A dense hydrophobic film was formed on the tight core surface to change its microstructure and wettability, which can achieve drainage gas recovery. Nanofluid will have a broad application in tight oil and gas reservoir stimulations. [ABSTRACT FROM AUTHOR]

This study evaluates the dependency of production rate on the recovery of hydrocarbon from conventional reservoirs using MBAL simulator. The results indicated that the recoveries are sensitive to the production rate in almost all hydrocarbon reservoirs. It was also found that the recovery of volumetric gas drive reservoirs is not impacted by the production rate. In fact, any increase in the production rate improves gas recovery in weak and strong water drive reservoirs. Moreover, increasing the production rate in oil reservoirs decreases the recovery with a significant effect observed in the weak water drive reservoirs. The results of this study demonstrate the need for implementing an effective reservoir management in order to obtain a maximum recovery. [ABSTRACT FROM AUTHOR]

Subtle reservoir exploration could not be commonly carried out by costly conventional methods especially when subtle reservoirs are becoming smaller in surfaces and reserves. The epochal genetic quantitative techniques were proved to be suitable for the subtle reservoir prospecting, but the anomaly grade classification method did not match the quantitative data qualitative dividing. And the combination of genetic quantitative techniques and geophysical exploration methods to the prospecting application for subtle reservoirs still need more studies. For the questions, 194 topsoil samples and 237.05 km continuous electromagnetic profiling (CEMP) lines were arranged in typical subtle reservoirs in the Suganhu Basin. The realtime-PCR technique was used to get methanotrophic, propanotrophic functional gene pmoA and prmA quantitative data. The results showed that the classification method using cumulative probability distribution curves with regression analyses could be used to classify the genetic quantitative anomalies by the equation of y = az. The genetic quantitative anomalies and source strata thickness showed positive correlation along the section lines in the east of study areas. Integrated studies between genetic quantitative anomalies and CEMP results in the stereoscopic direction indicated three promising areas in the Suganhu Basin. This research is expected to be extended to the same type of reservoirs prospecting work. [ABSTRACT FROM AUTHOR]

In order to investigate the geochemical characteristics, sources and accumulation process of Lower-Jurassic Sangonghe Formation tight sandstone oil, multiple geochemical analyses were performed on source rocks, oil samples and sandstone particles from Wenjisang area in Turpan Basin. The results show that coal-measure source rocks have relatively higher organic matter abundance and type-II organic matter for Xishanyao and Badaowan Formations, with the potential of liquid hydrocarbon generation. Oil samples of Sangonghe Formation have the characteristics of coal-measure-formed oil. Higher maturity indicate the oil may be mainly generated by Lower-Jurassic Badaowan Formation source rocks. Quantitative fluorescence parameters also reflect that hydrocarbons charged into Sangonghe Formation through continuous migration from the bottom of sand body to the top gradually. In down dip direction of Wenjisang area may develope continuous tight oil and gas reservoirs in Lower Jurassic. [ABSTRACT FROM AUTHOR]

Iran has enormous energy resources and owns the second largest oil and gas reservoirs in the world. Cheap domestic energy prices and energy subsidies had led to a rapid increase in domestic energy consumption in the country. In 2010, increasing domestic energy prices and targeted subsidies reform were implemented. The objective of this article is to allocate optimally to each end-user a certain amount of energy to be supplied by a given resource in Iran regarding targeted subsidies reform. For this purpose, energy demands of end-users are forecasted and the outcomes are used in a fuzzy linear programing model, which determines the best allocation of energy resources of Iran from 2012 to 2020. The results would provide a scientific basis for the optimal allocation of energy resources in meeting the future energy demand in Iran. [ABSTRACT FROM AUTHOR]

Tight gas reservoirs have been researched nearly 50 years and become more and more important in the future with the increasing consumption of nature gas. In this study, the characteristics of Guang’an tight gas reservoir, which lies in the middle of Sichuan Basin, China, was analyzed. This reservoir is a typical tight gas reservoir. First, the porosity and permeability of it are low. Second, it has high water saturation and diffused boundaries. Third, it does not have an obvious seal. Fourth, it does not have a clear gas-water contact. Fifth, it has geologic “sweet spots,” close to source rock. Sixth, it has normal reservoir pressure. According to the actual conditions of Guang’an tight gas reservoir, a new reservoir accumulation model is established, which integrates the knowledge of conventional and unconventional reservoir, and which can explain the special phenomenon that tight gas reservoir can produce water and have normal pressure. [ABSTRACT FROM AUTHOR]

One of the problems of producing wells is water movement to production oil zone and so decreasing in wellhead pressure. Water produced from oil and gas reservoirs is a problem encountered all over the world since last two decades. The water quantities produced along with oil and gas are large due to the depletion stage of the reservoirs. The costs in treating and disposing of this water are very high and usually a negative impact on the economics of the petroleum reservoir production then it is necessary to set a long time to plan for make facility for protection or separation water produce with oil so very important to know about water breakthrough time. Therefore, in order to prevent to appear this problem it is necessary to try to have production with a suitable flow rate. However, because of economical considerations production in critical rate (the maximum rate of oil production without concurrent production of the displacing phase by coning; the critical rate, the built-up cone is stable but is at a position of incipient breakthrough), it is not economical. It is necessary to know when conning reach to the well if producing is above the critical rate to following causes: (a) production in optimum rate to delay water breakthrough time as far as possible, and (b) predicting water breakthrough time to help engineers to plan appropriate schedule for wellhead facilities preparing and well completion methods in order to maximum in place oil production. After review of two available methods for predicting water breakthrough time, the authors present a water-coning correlation to predict critical rate and water breakthrough time with less error than others. [ABSTRACT FROM AUTHOR]

CO2displacement and storage technology is a feasible technology for developing countries to relieve energy supply and control climate change. Based on the fractional flow theory, considering comprehensive key factors affect CO2flow in reservoir, including viscous fingering, gravity separation, and reservoir heterogeneity, to establish CO2miscible displacement mathematical model and develop evaluation software CS-EOR. Aiming at the concrete reservoir, the oil displacement and CO2storage efficiency assessment were carried out, and the CO2utilization coefficients were quantified. The results will provide important theoretical foundation and reliable tool for further the evaluation of CO2injection project in mature oil reservoir around the word. [ABSTRACT FROM PUBLISHER]

In abnormal pressure gas reservoirs, a traditional binomial deliverability equation is insufficient to accurately describe the gas filtration theory, but only the trinomial deliverability equation considering non-Darcy flow effect and ripple effect can be reasonable to some extent. When gas reservoirs are characterized by low porosity and permeability, strong heterogeneity, and high water saturation, gas flow, similar to liquid flow, is featured in significant threshold pressure gradient effect. Therefore, a threshold pressure gradient is added to the trinomial deliverability equation, and it is derived that the pressure drop caused by the pressure gradient is a variable related to production but not a constant. Consequently, a novel deliverability equation of abnormal pressure gas reservoirs considering variable threshold pressure drop has been established, providing theoretical guidance for determining reasonable gas production in abnormal pressure gas reservoirs. [ABSTRACT FROM PUBLISHER]

Marun oil field is one of the giant oil fields in southwest of Iran. It consists of two oil reservoirs and one gas reservoir named Asmari, Bangestan, and Khami, respectively. One of the major problems in this field is contamination of Asmari reservoir with H2S gas. The aim of this article was to study the trend and history of H2S spreading in Asmari reservoir of Marun oil field and also to investigate communication of Asmari reservoir layers via evaluation of fracture distribution, horizontal and vertical permeability distribution, and repeat formation test results. The results demonstrated good communication of layers in the center, especially in sectors 4 and 6 of the southern limb, central part of Asmari reservoir, due to higher fracture, higher permeability, and good pressure communication in these sectors. Moreover, the history of H2S concentration during time showed a decreasing trend while this contamination is spreading from the southeast to northwest of Asmari reservoir. [ABSTRACT FROM PUBLISHER]