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In this paper, the ionic liquids Met-1, Met-2, Asp-1 and Asp-2 were prepared by acid-base neutralization reactions with different molar ratios of amino acids (methionine and aspartic acid) and concentrated sulfuric acid as raw materials. Four ionic liquids were formulated into different concentrations of inhibitors, and their hydration inhibition and inhibition mechanism were investigated by anti-expansion experiment, linear swelling experiment and flocculation experiment. The results showed that when the molar ratio of aspartic acid to concentrated sulfuric acid was 1:1.5, which was named Asp-2, and the concentration of Asp-2 was 1.0%, the inhibitor achieved the best hydration inhibition performance on clay with 91.95% anti-swelling rate and 21.37% linear swelling rate. Infrared spectra (FT-IR) analysis, thermogravimetric analysis (TGA), and laser particle size analysis were used to investigate the inhibition mechanism of Asp-2. The results showed that the average particle size of the hydrated soil samples increased by 0.282 μm and the median particle size increased by 2.101 μm after the addition of Asp-2 inhibitor, indicating that Asp-2 inhibitor played a good inhibitory role in the drilling fluid. [ABSTRACT FROM AUTHOR]

High‐voltage electric pulse rock breaking has excellent potential for exploiting deep geothermal resources. Numerous researchers have conducted experimental studies on this topic, particularly in rock mechanics, where the breakdown occurs. However, there has been limited scholarly research on drilling fluid. Therefore, the study focuses on the drilling fluid suitable for electric pulse drilling, considering the characteristics of electric pulse rock breaking, which differ from traditional rock breaking. The study focused on the impact of various drilling fluid parameters on the effectiveness of electric impulse rock breaking using red sandstone as the experimental material. This was investigated using the finite element method, and indoor electric rock‐breaking tests were conducted in a drilling fluid environment. The results indicate that the plasma channel mainly grows in the permeable layer of the drilling fluid, resulting in shallow rock breaking depth in the drilling fluid environment. The pore permeated by drilling fluid guides the growth of the plasma channel. The higher the conductivity of the drilling fluid, the closer the ion channel of rock breaking by electric pulse is to the rock surface. This results in a smaller crushing volume and shallower damage depth, which is more detrimental to rock breaking by an electric pulse. The viscosity of drilling fluid can impede the breakdown to some extent. In this paper, the influence of drilling fluid parameters on electro‐pulse rock‐breaking technology is preliminarily studied, which has significant reference value for the selection of actual drilling fluid. [ABSTRACT FROM AUTHOR]

In view of the extremely developed bedding of shale formations, which are dominated by micro-nano pores and fractures, traditional sealing agents make it difficult to produce a tight seal on shale formations due to their huge particle sizes. Combining the bridging effect of inorganic nanoparticles and the deformation properties of organic particles, this article synthesized a core-shell structure nano-blocking agent through emulsion polymerization, which was called P(MMA-St-BD)/KH570-SiO2. The structure of the synthesized nano-plugging agent was characterized utilizing Fourier transform infrared spectroscopy (FT-IR), particle size distribution, thermogravimetric analysis (TGA), and transmission electron microscopy (TEM). Performance characterization was carried out through the effect of nano-blocking agents on emulsion stability, rheological properties, microporous filter membrane plugging experiments, and core pressure-bearing capacity tests. The findings demonstrate that P(MMA-St-BD)/KH570-SiO2's structure satisfies design specifications, and that the nano-plugging agent has outstanding thermal stability, homogeneous particle size distribution, and good dispersion. Its decomposition temperature also exceeds 400 °C. This study analyzed the plugging efficiency of nano-blocking agents from the temperature perspective, indicating that the nano-blocking agents seal shale formations tightly. Ultimately, through mechanism analysis, nanomaterials can squeeze and deform through the polymer shell and enter the shale micropores and micro-cracks for sealing, forming a high-strength sealing zone. [ABSTRACT FROM AUTHOR]

Natural gas hydrate is a promising unconventional natural gas source due to its high energy density and huge global reserves. During exploitation, the drilling fluid may invade the hydrate formation and induce hydrate decomposition, causing reservoir damage. Herein, a novel reservoir protectant made by bio-degradable temporary plugging material (BDTPM) was developed in the form of polymer-ceramic composite microcapsules. As an additive to the drilling fluid, the BDTPM can minimize drilling fluid intrusion by plugging the reservoir during drilling and afterwards maximize permeability recovery by degrading the material. The particle size distribution was in the range of 1–130 μm. The optimal mass ratio between modified ceramic particles, ethyl cellulose and epoxy resin was found to be 4:2:1. The plugging rate was 100% when ethyl cellulose and epoxy resin were mixed to coat the ceramic particles to form BDTPM, and the plugging performance was the best. At a temperature close to the typical hydrate reservoir environment (5 °C), 0.02 wt% low-temperature complex enzyme can degrade BDTPM, and the permeability recovery rate is 64.66%. The efficient reservoir protectant developed in this work could play an important role in the successful drilling of natural gas hydrate reservoirs. [ABSTRACT FROM AUTHOR]

The evaluation of the use of sawdust in drilling fluid formulation is covered in this study. The investigation focused on the physicochemical and rheological properties of water-based mud (WBM) drilling fluids that included four different dosages of sawdust. These properties included yield stress, plastic viscosity, rheological behavior, gel strength, filtration test (API filtrate; American Petroleum Institute), and pH. The sawdust was employed as a substitute for the polymers commonly used in water-based muds (WBMs) to serve either as a viscosifier or as a fluid loss controller. The current study set out to evaluate how sawdust (diameter ≤630 µm) affected the primary characteristics of the drilling muds. Sawdust was utilized in place of carboxymethyl cellulose polymer (CMC) as a viscosifier and polyanionic cellulose polymer (PAC) as a filtrate reducer at several dosages (0, 10, 20, 50, and 100 g/L). It was found that the sawdust dosage and its role had a significant impact on the rheological characteristics of the drilling fluids. At amounts between 20 and 50 g/L, the sawdust was added as a viscosifier to the drilling fluids under study, resulting in a significant improvement in their physicochemical and rheological parameters (yield stress, plastic viscosity, and gel strength). However, the drilling fluids showed extremely high rheological properties and a viscosity that can slow down fluid circulation in the well when 100 g/L of sawdust were used, totally substituting for the polymers. [ABSTRACT FROM AUTHOR]

In underground diaphragm wall and pile foundation engineering operations, calcium ions from the concrete continually invade into the drilling fluids because of the frequent contact of the drilling fluids with the concrete, leading to gradual deterioration of the basic properties of the drilling fluids and large amount of waste muds after the operations. To improve the calcium resistance of the drilling fluids and minimize the amount of waste drilling fluids produced, the natural bentonite used to formulate the drilling fluids needs to be modified. A calcium-resistant compound bentonite ACB-16 is synthesized with natural bentonite purified through high-speed centrifuging and monomers for polymerization, such as a hydrophilic monomer BX with double carbon bonds, hydrophilic monomers AS and AP with sulfonic acid groups. In the polymerization reaction, the monomers enter into the crystal spaces of the purified bentonite, reacting with each other through in-situ free radical polymerization. Studies on the polymerization products with FT-IR, particle size distribution test, SEM and TEM show that the monomers successfully in-situ polymerize in the crystal spaces of the bentonite. The quality of ACB-16 exceeds the quality of the OCMA bentonite. A drilling fluid formulated with ACB-16 has an apparent viscosity of 26 mPa∙s, an API filter loss of 7.6 mL, a good rheology and filtration property as well as a good calcium resistance. When contaminated with 1% calcium chloride, the rheology and filtration property of the drilling fluid are still stable. The limit of calcium resistance of a drilling fluid formulated with ACB-16 is 6,300 mg/L (equivalent to 1.75% CaCl2 ), perfectly satisfying the requirements for a drilling fluid to resist calcium contamination in foundation engineering. Using particle size analysis and SEM, the working mechanism of ACB-16 is studied. The high molecular weight polymers located on the networking structures of the bentonite hinder the ion exchange between the calcium ions and the bentonite, thereby maintaining the thickness of the hydration membrane and the c-spacing of the bentonite and supporting the network structures generated by the hydrated bentonite. Direct mixing of ACB-16 with water can obtain a calcium-resistant drilling fluid with excellent properties. ACB-16 is easy to use, it will have good application prospects in foundation engineering and other fields, and it can also be used in formulating anti-sloughing drilling fluids for high calcium environment such as salt and gypsum drilling. [ABSTRACT FROM AUTHOR]

Two wells, the well Long-XX and the well Ning-XX, in Longdong area are recently tested, and the target zone located in the bauxite formation has been found an important alternative resource for the Changqing Oilfield. Significant findings were obtained in exploring the bauxite formation through these two wells. Technical difficulties, such as prevailing of dissolution pores and fractures, borehole wall collapse, mud losses and poor hole cleaning etc. have been encountered in drilling the target bauxite formation. The main factors contributing to borehole wall collapse were found in analyzing and testing the bauxite samples for physical properties, chemical properties, mechanical properties and sensitivity characteristics, and a fast-plugging, inhibitive drilling fluid for safe drilling of the bauxite formation was developed. This drilling fluid has high temperature (170 ℃) high pressure filter loss of less than 10 mL and percent secondary cuttings recovery of greater than 91%. After soaking the bauxite samples in the drilling fluid and fresh water respectively for 15 days, the compressive strength of the samples tested in the drilling fluid is 81.8% higher than that of the samples tested in the fresh water. This drilling fluid has been tried in drilling the first horizontal Long-4XX well targeted the bauxite reservoir in Changqing, a horizontal section of 700 m was successfully drilled. The daily flowing production rate of this well is 3.53 × 106 m³, a new record made in developing the upper Paleozoic resources in the Erdos basin in the last 50 more years. This technology has provided a technical support to the development of the similar reservoirs. [ABSTRACT FROM AUTHOR]

The effect of silicon dioxide nanoparticles on the rheology of aqueous solutions of xanthan gum was studied. Tests were carried out on a rotational viscometer and by the oscillatory method on an Anton Paar rheometer. Additions of nanoparticles up to 2 wt.% to solutions containing up to 1 wt.% gum were analyzed. In the studied concentration ranges, the influence of nanoparticles maintains the shape of the flow curves and viscosity curves, introducing small changes. It was shown that with increasing concentration of nanoparticles, the elastic modulus of suspensions, the values of their yield strengths and flow points increase. At the same time, the pseudoplasticity index practically does not increase, leading to the manifestation of a brittle rupture with increasing load in the oscillatory test of the suspension. The storage modulus at a nanoparticle concentration of 1% takes on a two-stage form, and at a concentration of 2% it forms a hysteresis curve, indicating a brittle rupture of the material. It was shown that the effect of the conformational transition is about 30% and decreases with increasing flow shear rate. [ABSTRACT FROM AUTHOR]

Ultrasonic wave propagates with strong penetration, high stability, and has non-contact nature, therefore it is widely used in the petroleum industry. As an application example, an ultrasonic flowmeter can accurately measure the annular flow rate of water-based drilling fluid. According to the outlet flow rate, it can be noticed if there is an abnormal situation in the well to avoid accidents such as well kick and blowout. However, due to the attenuation of ultrasonic wave in the drilling fluid, the relevant research results are not reliable. Herein, based on the theory of acoustics, the influences of water-based drilling fluid density, solid particle size and solid particle number on the ultrasonic attenuation characteristics under different frequencies are studied by numerical simulation. First, the propagation characteristics of ultrasonic wave in water-based drilling fluid are systematically analyzed, then the accuracy of the above results is verified by laboratory tests. The results show that the ultrasonic attenuation rate is positively correlated with the solid particle size, solid particle number and ultrasonic frequency in water-based drilling fluid, while it is negatively correlated with the density of water-based drilling fluid. Furthermore, it is established that the ultrasonic energy decreases with increasing propagation distance. The results of this study can provide a theoretical basis and practical guidance for using an ultrasonic flowmeter to accurately measure the annulus return flow rate of drilling fluid and develop an intelligent drilling system, so as to improve the efficiency of field operation and drilling success rate. [ABSTRACT FROM AUTHOR]

In the development of ultra-deep wells, extremely high temperatures can lead to inefficiency of additives in drilling fluids. Hence, there is a need to prepare additives with a simple preparation process and good effects at ultra-high temperatures to ensure stable drilling fluid performance. In this study, a high temperature resistant filtration loss polymer (LY-2) was prepared using γ-methacryloyloxypropyltrimethoxysilane (KH570), N,N-dimethylallyl ammonium chloride (DMDAAC), sodium p-styrenesulfonate (SSS), and β-cyclodextrin (β-CD). The impact of the different monomer ratios on particle size, rheology, and filtration performance was systematically investigated. Infrared spectroscopy afforded the structural features. Thermogravimetric Analysis detected the temperature stability, and scanning electron microscopy characterized the polymer micromorphology. LY-2 was completely decomposed at a temperature above 600 °C. Experiments showed FLAPI of the drilling fluid containing 3% LY-2 aged at 260 °C/16 h was only 5.1 mL, which is 85.4% lower compared to the base fluid. This is attributed to the synergistic effect of the polymer adsorption through chemical action at high temperatures and the blocking effect of carbon nanoparticles on the filter cake released by cyclodextrin carbonization at high temperatures. Comparing LY-2 with commercial filter loss reducers shows that LY-2 has excellent temperature resistance, which exhibited five times higher filtration performance and relatively low cost, making it possible to be applied to ultra-high temperature drilling operations in an industrial scale-up. [ABSTRACT FROM AUTHOR]

Laponite® (LAP) is an intensively studied synthetic clay due to the versatility given by its layered structure, which makes it usable in various applications. This review describes the multifaceted properties and applications of LAP in aqueous dispersions and gel systems. The first sections of the review discuss the LAP structure and the interactions between clay discs in an aqueous medium under different conditions (such as ionic strength, pH, temperature, and the addition of polymers) in order to understand the function of clay in tailoring the properties of the designed material. Additionally, the review explores the aging phenomenon characteristic of LAP aqueous dispersions as well as the development of shake-gels by incorporating LAP. The second part shows the most recent studies on materials containing LAP with possible applicability in the drilling industry, cosmetics or care products industry, and biomedical fields. By elucidating the remarkable versatility and ease of integration of LAP into various matrices, this review underscores its significance as a key ingredient for the creation of next-generation materials with tailored functionalities. [ABSTRACT FROM AUTHOR]

As the deep hole drilling environment becomes more and more complex, the phenomenon of well wall instability during the implementation of rope coring drilling technology becomes more and more prominent. In order to solve this technical issue, the factors leading to well wall instability in the process of rope coring were discussed in detail from both geological and engineering factors. Taking the key investigation hole DZK4 in a major water supply project as an example, the synergistic anti-collapse theory of "cation-high adhesion-wetting reversal-chemical inhibition-reasonable density support" was proposed in combination with the actual situation of deep hole and complex rock formation, and the drilling fluid formula was formed in combination with this theory. The application shows that the density of drilling fluid, water loss and other related indexes meet the control standard of drilling fluid, and the performance of drilling fluid is more stable. [ABSTRACT FROM AUTHOR]

The effective determination of pressure losses depends on accurate knowledge of the drilling fluid rheology. As the fluid circulates deeper around the wellbore, its rheological behavior undergoes significant alterations due to the variations in downhole conditions encountered. The present study investigates the effects of the rheological properties of Yield-power law fluid at various pressures and temperatures on annular pressure losses and velocity profiles. Simulations were performed using Computational Fluid Dynamics to examine the fluid flow in turbulent and laminar regimes. Comparison between numerical, experimental and slot approximation model results showed a good agreement. Results indicated that pressure losses have reduced in both regimes with increasing temperature, at a constant pressure. However the pressure has the opposite effect at a constant temperature. For a drilling fluid flow velocity of 1 m/s, the elevation of temperature from 25 °C to 90 °C, decreases the pressure drop gradient by (31% to 48%) at low and high- pressure conditions respectively. Whereas, the influence of increasing pressure on pressure losses is more apparent at 25 °C. Earlier transition from laminar to turbulent is observed with temperature rise. Therefore, the temperature effect on pressure losses in the turbulent region; is shown for different Generalized Reynolds numbers. [ABSTRACT FROM AUTHOR]

Deep oil and gas are essential alternative resources for future energy sources, but the lack of high temperature and high salt resistance mechanisms and agents significantly limits their development. Copolymers of six commonly used high-temperature and salt resistance monomers and acrylamide with similar molecular weights were prepared to improve oil recovery in deep reservoirs. The effects of different functional groups on the high-temperature and salt resistance of polymers were revealed by the drilling fluid and elemental analysis, TOC test, Zeta potential, particle size, and other analytical methods. Experimental results indicate that the pyrrole ring groups, quaternary amine groups, long-chain sulfonate groups, and benzenesulfonic acid groups can effectively improve the high-temperature stability of polymers in an aqueous solution. Quaternary ammonium groups and pyrrole rings can enhance the polymer adsorption with clay under high temperatures and high salinity conditions due to charge attraction. However, these functional groups hinder the clay dispersion and reduce the stability of drilling fluids. Hydration groups, such as sulfonic and carboxylic acid groups, can better maintain the colloidal stability of drilling fluids under high temperatures and high salinity, and benzene sulfonic acid groups are the optimal hydration groups. After the polymer is adsorbed on the clay surface, the benzene sulfonic acid group assists in forming a thicker hydration film on the clay surface, effectively hindering the damage of high temperature and high salinity on the clay. The findings and observations of this study provide theoretical support for the development of high-temperature and salt resistance polymers for water-based drilling fluids of ultra-deep wells. [ABSTRACT FROM AUTHOR]

It is very important to clarify the reservoir damage characteristics and damage characteristics and damage mechanism of tight sandstone gas reservoirs in Jinhua-Zhongtai mountain area of central SiChuan Basin, and put forward the technical countermeasures of "Double protection" drilling fluid to protect the reservoir and the environment, which is very important for the efficient well construction in this area. Through X-ray diffraction, scanning electron microscopy, casting thin sections and other testing methods, the mineral composition and microstructure characteristics of the block were analyzed, and the potential damage factors of the reservoir were clarified. Based on the sensitivity evaluation, it was revealed that the overall sensitivity damage of the block was weak. The main damage type was salt-sensitive damage, and the critical salinity was 9472.5 mg/L. On the basis of the environmental protection drilling fluid system used in this block, the surfactant which can effectively prevent gas invasion and reduce surface tension is selected, and the "Double protection" drilling fluid system is constructed. Through comprehensive performance test and reservoir protection performance evaluation, the core permeability damage rate of the optimized drilling fluid system is reduced from 88.77 to 18.66%, and the cuttings recovery rate is increased to more than 66%, and the cuttings expansion rate is reduced to less than 3.2%, which can effectively solve the problem of reservoir damage in drilling in Jinhua-Zhongtai mountain block in central Sichuan. [ABSTRACT FROM AUTHOR]

In the weighting drilling fluid, barite will adsorb the free water and additives in the drilling fluid, which often worsens the performance of the drilling fluid. In order to optimize the performance of drilling fluid, a method for measuring the specific surface area of powder in liquid phase based on low field nuclear magnetic resonance (NMR) relaxation was established to study the occurrence state of barite in drilling fluid. The variation of specific surface area of barite in suspension with different concentrations were measured by particle size calculation and low field NMR, and the experimental results show that the specific surface area obtained by low field NMR can reflect the aggregation state of barite in liquid phase. Through organic carbon adsorption and rheological test, the adsorption law of barite to different drilling fluid additives was obtained. This study can solve the problem of additive addition in drilling fluid and optimize the performance of drilling fluid. [ABSTRACT FROM AUTHOR]

The impact of conventional drilling fluid treatment agents on hydrate decomposition was analyzed, and the inhibition of hydrate decomposition by different inhibitors was evaluated・ Two types of efficient hydrate decomposition inhibitors were selected and their mechanisms of action were explored・ The results indicate that conventional drilling fluid treatment agents exhibit a certain degree of inhibition of hydrate decomposition, among which XC has the strongest inhibitory effect on hydrate decomposition, extending the hydrate decomposition time by 21.9%・ There is a good linear positive correlation between the decomposition time of hydrates and the apparent viscosity, w让h a correlation coefficient R2 greater than 0・95・ The polyvinylcaprolactam(PVCap) composite product and antifreeze protein were selected to have good hydrate decomposition inhibition effects, w让h a delay rate of 97.3% and 66. 6% ・ The oxygen atoms in the PVCap seven membered ring structure are prone to hydrogen bonding w让h water molecules on the surface of the hydrate, forming a stable cage like structure on the surface of the hydrate crystal nucleus・ A large number of seven membered rings adsorb to form a layer of coating film, weakening the mass and heat transfer effects brought by external fluids・ Antifreeze proteins adsorb to the surface of hydrates through hydrogen bonding and hydrophobic interactions, reducing the surface area of hydrates and increasing the resistance of external fluids to mass and heat transfer to the surface, thereby delaying the decomposition of hydrates・ The viscosity effect of commonly used drilling fluid treatment agents on hydrate decomposition inhibition and the two selected high・Efllciency hydrate decomposition inhibitors can provide drilling fluid technical support for hydrate formation drilling. [ABSTRACT FROM AUTHOR]

Thermo-responsive nanocomposites have recently emerged as potential nanoplugging agents for shale stabilization in high-temperature water-based drilling fluids (WBDFs). However, their inhibitory properties have not been very effective in high-temperature drilling operations. Thermo-responsive Janus nanocomposites are expected to strongly interact with clay particles from the inward hemisphere of nanomaterials, which drive the establishment of a tighter hydrophobic membrane over the shale surface at the outward hemisphere under geothermal conditions for shale stabilization. This work combines the synergistic benefits of thermo-responsive and zwitterionic nanomaterials to synchronously enhance the chemical inhibitions and plugging performances in shale under harsh conditions. A novel thermo-responsive Janus nanosilica (TRJS) exhibiting zwitterionic character was synthesized, characterized, and assessed as shale stabilizer for WBDFs at high temperatures. Compared to pristine nanosilica (SiNP) and symmetrical thermo-responsive nanosilica (TRS), TRJS exhibited anti-polyelectrolyte behaviour, in which electrolyte ions screened the electrostatic attraction between the charged particles, potentially stabilizing nanomaterial in hostile shaly environments (i.e., up to saturated brine or API brine). Macroscopically, TRJS exhibited higher chemical inhibition than SiNP and TRS in brine, prompting a better capability to control pressure penetration. TRJS adsorbed onto the clay surface via chemisorption and hydrogen bonding, and the interactions became substantial in brine, according to the results of electrophoretic mobility, surface wettability, and X-ray diffraction. Thus, contributing to the firm trapping of TRJS into the nanopore structure of the shale, triggering the formation of a tight hydrophobic membrane over the shale surface from the outward hemisphere. The addition of TRJS into WBDF had no deleterious effect on fluid properties after hot-treatment at 190 °C, implying that TRJS could find potential use as a shale stabilizer in WBDFs in hostile environments. [ABSTRACT FROM AUTHOR]

It is well known that the type of drill pipe motion has an important effect on the cuttings transportation process and pressure loss gradient in the annular space, in particular for horizontal and deviated wells. For that, it is needed to understand more about the effect of planetary motion on the pressure loss gradient during circulation of the drilling mud in the bottom hole of explored wells. In the present paper, the influence of the drill pipe planetary motion on the pressure loss gradient of a mixture (Ostwald-de Waele fluid with solid particles) in a turbulent regime during its circulation through an annular space is evaluated for different drilling parameters including eccentricity, rate of penetration, and solid particles size. In addition, the effect of drill pipe planetary motion for various conditions of temperature and pressure is evaluated for two types of muds water-based and oil-based. The numerical analysis revealed that an angular speed of 120 rpm of planetary motion can be considered as an optimal value in terms of pressure loss gradient. In addition, it was observed that the effect of the planetary motion on the pressure loss gradient depends mainly on the fluid temperature for both types of mud. [ABSTRACT FROM AUTHOR]

In this work, we studied a method for producing organophilic clay with a contact angle of more than 150° from bentonite clay from the Taganskoye deposit, demonstrating high stability in an organic environment, with the aim of further creating drilling fluids based on it, exhibiting thixotropic properties in an anhydrous environment. During the course of our research, A novel method for producing superhydrophobic clays from bentonite have been developed and explored their potential applications in the production of anhydrous drilling fluids for the petroleum industry. A variety of cationic surfactant compounds were used as superhydrophobic agents.In the presence of tetrakis (decyl) ammonium bromide (TKAB), organophilic (superhydrophobic) clay with a wetting angle of 170 degrees was obtained. The distribution and stability of organophilic clay particles obtained using TKAB in diesel fuel were determined. It was proved that the particles of organophilic clay formed on the basis of TKAB create a stable suspension in diesel fuel and do not mix with the aqueous phase at all. [ABSTRACT FROM AUTHOR]

Produced water is the main waste stream in the oil and gas sector, with significantly greater concentrations of hydrocarbons, heavy metals, and other contaminants. Several works and technologies were developed to reuse the produced water in many applications including drilling and completion fluids. However, in general, a pretreatment is required. According to our knowledge, the reuse of produced water in non-aqueous drilling is still not reported. Therefore, this work proposed the formulation of olefin-based drilling fluids containing between 20-40% of untreated produced water. Through factorial experimental design, the influence of produced water, emulsifier, and viscosifier on the properties of the formulated emulsions was investigated. Our results show that produced water without treatment can be used as an aqueous phase for olefin-based drilling fluids, with the best formulation being the test that has RO/A = 60/40, emulsifier concentration of 14.26 kg/m³ and viscosifier concentration of 2.85 kg/m³. The well-cleaning properties of the proposed formulation were evaluated through numerical simulation in a well with high inclination. The results showed that the hole cleaning was not affected by using untreated produced water in the fluid formulation. The results presented here open a new possibility to reuse produced water in drilling operations without performance loss. [ABSTRACT FROM AUTHOR]

High viscosity heavy oil invasion in the Tahe block have caused serious damage to the properties of the drilling fluids. To deal with this problem, the key properties of the Tahe heavy oils and those of the typical poor quality heavy oils were compared, and the change of the viscosity of the Tahe heavy oil asphaltenes in toluene solution with the concentration of the heavy oils was studied. It was found that the high viscosity of the Tahe heavy oils comes from high asphaltene content and high aromaticity. Based on this finding, two programs were prepared; one is, at the time when there is only slight heavy oil invasion, a compound additive containing appropriate dispersants and aromatic fraction can be added into the contaminated drilling fluid to disperse the heavy oils. This treatment has been best done in the 5# drilling fluid. In drilling the well TH121155X, the dispersity of the heavy oils in the solids-free drilling fluid was more than 99%. The other treatment involves the contamination of drilling fluids by large amount of heavy oils. In this treatment the heavy oils are wrapped up by wrapping agents and therefore lose their adhesiveness. The adhesiveness of the wrapped heavy oils on the surfaces of the drilling tools is minimized and the heavy oils can thus be effectively and efficiently separated out by the shale shakers. Study results show that wrapping agent BGJ-2-4 has good wrapping capacity for the treatment of heavy oils found in the well TH12471H, and the adhesion rate on the walls of mud tanks is only 0.3%. [ABSTRACT FROM AUTHOR]

High temperature environment has many negative effects on the drilling fluid system. In order to avoid or delay these negative effects, phase change materials (PLMs) microcapsule technology was introduced into the high temperature drilling fluid system in this study to further improve the applicability of the high temperature resistant drilling fluid under extremely high temperature formation environment. The microcapsules circulate with drilling fluid, and PLMs melt endothermically at high temperature in deep formation and solidify exothermically at shallow formation. A PLMs microcapsule with solar salt (NaNO 3 : KNO 3 = 3:2) as core material and nano silica as shell material was prepared by sol-gel interfacial polymerization. The structure and properties of the microcapsules were characterized, the temperature-control performance of the microcapsule and its stability and compatibility with drilling fluid were evaluated. The results showed that the microcapsules were well encapsulated, and the single microcapsule particles were spherical, but there was a certain agglomeration phenomenon. The particle size distribution of microcapsules was concentrated in 4–16 µm, with a median particle size of 7.79 µm. The highest encapsulation rate was 60.6%, and the melting enthalpy was 68.48 J/g. The microcapsules had no obvious mass loss below 400 ℃ and had excellent thermal stability. It was proved that the microcapsules had good sealability, shear stability and cycling stability, with the enthalpy/mass retention rate all above 90%. The addition of microcapsules will not affect the basic properties of drilling fluid, and can reduce the peak temperature of high temperature drilling fluid. Different from existing researches, this paper uses a method that absorbs heat to slow down the heating rate of drilling fluid in the formation. This is a new idea, which is expected to be widely studied in the field of high temperature drilling fluids. [Display omitted] • PCM microcapsules were prepared to increase the applicability of high temperature drilling fluid. • PCM microcapsules had good morphology, suitable size, and excellent shear and cycling stability. • PCM microcapsules had good compatibility with water-based drilling fluid. • PCM microcapsules had perfect thermal stability and considerable temperature control effect. [ABSTRACT FROM AUTHOR]

A high performance viscosifier DV-1 has been developed to solve the problem of degradation and losing effectiveness of drilling fluid viscosifiers in high temperature and high salinity conditions. VD-1 is synthesized through free radical copolymerization with monomers such as MAPS, MAC and NVP. The initiator of the polymerization reaction is AIBA. The optimal reaction condition, determined through orthogonal experiment method, is as this: reaction temperature is 50 ℃, concentration of the monomers is 40%, concentration of initiator is 0.4%, and reaction time is 4 h. The reaction product was characterized using FTIR, 1H-NMR and TG-DTA, and the viscosifying capacity, high temperature high salinity performance and the ling-term effectiveness of the synthesized product were evaluated. The evaluation experimental results show that 1% water solution of DV-1 has apparent viscosity of 44.7 mPa∙s. After aging at 180 ℃ for 16 h, the viscosity of the water solution is still maintained at 53.2% of its original viscosity. DV-1 is resistant to the contamination of salts. DV-1 also has good long-term effectiveness; after aging at 180 ℃ for 72 h and 120 h, the viscosity of the solution is still maintained at 50.5% and 40.7% of its original viscosity. DV-1 has EC50 of 30 200 mg∙L−1, meeting the standard of discharge in offshore area. The viscosifying mechanisms of DV-1 are studied by observing the spatial 3D morphology and by analyzing the Zeta potential of DV-1 in solution, it is concluded that DV-1 viscosifies in solution because the molecules of DV-1 have stable main chains and rigid side chains, the amphoteric ionic structure inhibits the continual curling of the side chains, thus effectively improving the salt resistant performance of DV-1 as a viscosifier. [ABSTRACT FROM AUTHOR]

The technical problems of drilling fluid in ultra-deep, unconventional oil/gas, deep water, hot dry rock, polar, natural gas hydrate and other complex formations are systematically sorted out. The key scientific problems and core engineering problems are discussed. Combined with the research progress of drilling fluid technology in recent years, the development of drilling fluid technology for ultra-deep, unconventional oil/gas, deep water, hot dry rock, polar, natural gas hydrate and other complex oil and gas is provided. The problems in the drilling of complex formations, such as hightemperature, high-pressure and high- salinity, serious shale hydration, wellbore instability, large temperature difference, loss circulation, formation damage, and low degree of automation of drilling fluid maintenance, domestic and foreign researchers have developed key material, systems and equipments such as high-temperature and high-salinity water-based/oil-based drilling fluid, constant rheological drilling fluid, anti-ultra-high temperature foam drilling fluid, environmentally friendly ultra-lowtemperature drilling fluid, intelligent temperature and pressure response plugging material, degradable reservoirprotection material, drilling fluid online monitoring and automatic feeding system. However, with the increasingly complex formationconditions of drilling, there are still deficiencies in drilling fluid materials in terms of ultra-high temperature resistance, ultra-long-term stability, clay swelling inhibition, and environmental protection performance. Severe/total loss circulation, reservoirprotection, and drilling fluid automation control still face severe challenges. In order to meet the performance requirements of drillingfluid in the process of drilling in complex formations, it is necessary to further study the working/failure mechanism of drilling fluidadditives under complex formation conditions, the structure-activity relationship changes and action mechanism of drilling fluidadditives at different scales such as micro-meso-macro scales, establish a safe and efficient multi-functional integrated controlmethod of drilling fluid, construct intelligent drilling fluid theory and technology, and provide technical support for the development of complex underground resources. [ABSTRACT FROM AUTHOR]

Reducing friction between drill string and wellbore wall is one of the key functions of drilling fluid which may result from tight holes, key seats, differential sticking, or cutting build up along the drill string. However due to growing environmental concerns, biodegradable lubricants which are also cost-efficient are appreciated and mandated in many countries. This study discusses the performance analysis of biodegradable biodiesel produced from pomelo peels and Petroleum-based lube oil as drilling fluid lubricants. The test samples comprise 700 mL of water + 10 % bentonite + 3 % barite + 0.25 % CaCO3 + 0.25 % KOH + 1 % CMC + lubricant. Two sets of lubricants were utilized to prepare 10 samples of drilling fluid, one set with petroleum-based lubricant and other with biodiesel. Essential oil was extracted from pomelo peel with the help of the Clevenger apparatus. The oil was then converted to biodiesel through the process of transesterification. Biodiesel properties were tested for the ASTM standards. Both sets of drilling fluid samples were tested for their rheological, filtration and lubricating properties and from the results obtained it can be concluded that both type of lubricating agents have almost negligible impact on rheological and filtration loss properties. However, the lubricity coefficient values drastically decreased as we increased the lubricant content, which is an indication that biodiesel extracted from pomelo peel acts as a better lubricant. The values of the lubricity coefficient for biodiesel based drilling fluid also fell well within the advised range (<0.30). We can therefore draw the conclusion that biodiesel made from pomelo peel can replace petroleum-based lubricants while also lowering the environmental concerns related to lubricants. [ABSTRACT FROM AUTHOR]

The effects of nano-molybdenum disulfide (nano-MoS2) on the tribological behavior of polycrystalline diamond compact (PDC) with a cobalt leaching depth of 422 μm were studied in this research. Ball-on-disk friction tests were conducted to evaluate the impact of nano-MoS2 concentration and bearing capacity on the lubrication effect of drilling fluid and the friction performance of PDC. The results demonstrated that the addition of nano-MoS2 enhanced the lubrication effect of drilling fluid and improved the friction performance of PDC. The study also discussed the lubrication mechanism of drilling fluid and the mechanism by which adding nano-MoS2 enhances tribological properties. These findings contribute to deepen the understanding of the friction and wear mechanism of PDC in lubricating environment, and provide a theoretical reference for the future application of PDC in the petroleum field. [ABSTRACT FROM AUTHOR]

When drilling into a reservoir, the drilling fluid containing bentonite is prone to solid phase invasion, causing serious damage to the reservoir, and the conventional API barite suspension stability is poor, which makes it easy to cause sedimentation and blockage. Therefore, in order to avoid accidents, we use ultrafine barite to obtain a good suspension stability. More importantly, the method of modifying zwitterionic polymers on the surface of nano-silica is used to develop a temperature-resistant and salt-resistant fluid loss reducer FATG with a core-shell structure, and it is applied to ultra-fine clay-free water-based drilling fluid (WBDF). The results show that the filtration loss of clay-free drilling fluid containing FATG can be reduced to 8.2 mL, and AV can be reduced to 22 mPa·s. Although the viscosity is reduced, FATG can reduce the filter loss by forming a dense mud cake. The clay-free drilling fluid system obtained by further adding sepiolite can reduce the filtration loss to 3.8 mL. After aging at 220 °C for 15 d, it still has significant salt tolerance, the filtration loss is only 9 mL, the viscosity does not change much, a thinner and denser mud cake is formed, and the viscosity coefficient of the mud cake is smaller. The linear expansion test and permeability recovery evaluation were carried out. The hydration expansion inhibition rate of bentonite can reach 72.5%, and the permeability recovery rate can reach 77.9%, which can meet the long-term drilling fluid circulation work in the actual drilling process. This study can provide guidance for technical research in related fields such as reservoir protection. [ABSTRACT FROM AUTHOR]

Presently there are two core problems existed in downhole drilling fluid colling technology, i.e., the necessities of performing drilling fluid cooling and the real time control of the temperature of the downhole drilling fluid. Based on the borehole heat transfer model, the effects of drilling fluid cooling parameters on the downhole temperature are investigated. Based on the non-dominated sorting generic algorithm with elitest strategy, a drilling fluid cooling parameter optimization model is established, and a method for calculating the cooling limit of downhole drilling fluids is constructed. Using the model and the method, the necessity of performing cooling operation can be evaluated. Then, based on the borehole heat transfer model, the quantitative relationship between surface cooling and downhole cooling is investigated, and it is found that a simple linear relationship exists between the change of downhole temperature and the change of surface injection temperature. Based on these relations obtained and the PID control algorithm, a method for real-time control of downhole drilling fluid temperature is developed. The aforementioned models and methods are then verified using data obtained from an example well. The verification shows that using the optimized model of cooling parameters, the downhole cooling limit obtained is 17 ℃ lower than the cooling limit obtained from the non-optimized model. Also, the downhole temperature control method based on PID control can be used to quantitatively control downhole temperature in a real-time manner., thereby minimizing energy consumption of the surface cooling equipment and ensuring the downhole temperature to quickly reach the designed level. [ABSTRACT FROM AUTHOR]

Borehole wall collapse has been encountered when drilling the Shasanyi sub-member in many wells in the NP-280 block in Jidong Oilfield. Study has shown that the shales in the block are easy to hydrate when in contact with water. Microfractures with medium and high angles are developed in the thief zones. These microfractures, with original widths of 0.1 μm – 100 μm, become widened under pressure and hence further become fractures through which drilling fluids are lost. This in turn induces large-scale sloughing of the borehole walls and borehole collapse has thus occurred. In this paper, the studies on the mechanisms of borehole wall stabilization in the broken formations in the NP-280 block and the methods of borehole wall instability evaluation are described. Using the high temperature inhibitive drilling fluid, which was used to drill the third interval of the wells, a new inhibitive drilling fluid with high plugging capacity is developed thorough laboratory optimization. This drilling fluid is suitable for drilling formations with induced microfractures. Field application shows that it can be used to effectively prevent the borehole wall collapse problems encountered in drilling the Shasanyi sub-member, and this technology is worth applying in future drilling operation in this area. [ABSTRACT FROM AUTHOR]

Synthetic-based drilling muds (SBMs) are complex mixtures of man-made fluids used during the drilling of oil and gas wells. SBM-derived chemicals can enter the environment through failed wells and routine or poor disposal practices, where they can persist and thereby warrant measurement. SBMs are commonly formulated with linear and methyl branched α- and internal-olefins mostly in the C14 to C20 carbon range, which are not native to crude oils. Thus, SBM-derived olefins can provide a basis to recognize the impact of these drilling wastes in the environment. However, the presence of abundant native hydrocarbons in oils and sediments can hinder the detection of trace level SBM-derived olefins by conventional organic sample preparation and analytical methods. Silver ion chromatography using silver nitrate (AgNO3) impregnated silica gel can serve to physically separate olefins from saturated aliphatic hydrocarbons native in crude oils, which can subsequently be analyzed and measured by conventional one-dimensional gas chromatography-flame ionization detection (GC-FID). In this study, SBM-derived olefins are measured in crude oils from the Deepwater Horizon oil spill and in their laboratory mixtures to a detection limit of approximately 5000 µg/g (0.5 wt%). In oiled sediment, SBM-derived olefins were reliably detected at concentrations as low as 1 µg/g-dry. An application of this method is demonstrated through analysis of crude oils and oil-contaminated seafloor sediment from the Taylor Energy oil spill site in the northern Gulf of Mexico where SBM was historically used and discharged. [ABSTRACT FROM AUTHOR]

This study focuses on developing an efficient and environment-friendly drilling fluid using biodiesel as an alternative to the conventional diesel-based drilling fluid for drilling highly technical and challenging formations. The biodiesel was synthesized and produced from castor oil using the transesterification process. The physicochemical properties suggests that produced biodiesel has a high flashpoint (148 °C) and low pour point (-12 °C) compared to diesel oil. The synthesized biodiesel is utilized as a base oil to formulate an ester-based drilling fluid. A thorough experimental study is performed to evaluate the performance of formulated drilling fluid at ambient and reservoir temperature condition. A diesel-based drilling fluid is also formulated for comparative analysis. The experimental findings show that castor biodiesel-based drilling fluid's plastic viscosity and yield points are 10% and 25% higher than the diesel-based drilling fluid. However, the least filtrate loss volume is obtained for castor biodiesel-based drilling fluid than the diesel-based drilling fluid at high-temperature conditions. The filtrate loss by diesel-based drilling fluid was 17% and 9% higher than castor biodiesel-based drilling fluid at 25 °C and 100 °C, respectively. The results suggest the non-Newtonian and shear-thinning behavior of castor biodiesel-based mud (n < 1) associated with the Herschel–Bulkley model. [ABSTRACT FROM AUTHOR]

In the process of deep oil and gas exploration and development, there are often challenges of high temperature and high pressure. The performance of drilling fluid can change under complex working conditions such as high temperature and high pressure. Studying the flow friction change law of drilling fluid under complex working conditions can provide a theoretical basis for increasing drilling speed and well control in ultra-deep wells. According to the actual working conditions, a high-temperature and high-pressure drilling fluid circulating flow friction testing device was established. The effects of temperature, pressure, solid particles, and gas content on the flow friction of drilling fluid were experimentally studied. Multiple regression method was used to fit and draw the temperature and pressure friction coefficient chart, which can better explain the quantitative relationship between temperature and pressure and drilling fluid flow friction. The results show that the flow friction of drilling fluid in the Shunbei block decreases with increasing temperature and increases with increasing pressure. The friction coefficient chart can more accurately reflect the quantitative relationship between the friction coefficient and temperature and pressure. The solid particle content has little effect on the flow friction, and the flow friction of drilling fluid increases with increasing gas content. This experimental device and analysis method are of great significance for studying the variation law of drilling fluid flow friction under complex working conditions. [ABSTRACT FROM AUTHOR]

This paper reviews the synthesis methods and basic properties of high temperature resistant natural modified AMPS filtrate reducer, high temperature resistant zwitterionic AMPS filtrate reducer and high temperature resistant rigidized modified AMPS filtrate reducer. And introduces the introduction of silicon, starch and graphene into natural modified AMPS filtrate reducer to improve salt and calcium resistance, the addition of cationic groups to ionic AMPS filtrate reducer to enhance electrostatic adsorption capacity and the introduction of rigid groups to rigidized modified AMPS filtrate reducer to increase molecular rigidity ・ This paper also evaluates the research directions of natural modified AMPS fluid loss additive, amphoteric AMPS fluid loss additive and rigidified AMPS fluid loss additive, with a view to providing a good reference for the development of new natural modified materials, the development of synthetic materials with multiple properties, and the introduction of other rigid groups with a ring structure. [ABSTRACT FROM AUTHOR]

With the gradual depletion of shallow oil and gas, deep oil and gas has become the focus of development. However, deep formations generally face the challenge of high-temperature and high-salinity, and drilling fluid agents are prone to failure, leading to drilling fluid intrusion into the formation that can cause serious drilling accidents such as well bore collapse. For this, a styrene-based nano-microsphere (SSD) modified with amphoteric ions was developed, with a particle size of 228 nm which could resist temperatures up to 200 °C and sodium chloride (NaCl) up to saturation. SSD has significant salt-responsive properties and its aqueous dispersion becomes transparent with increasing salinity. The SSD provided superior plugging performance in solutions containing NaCl, with a core plugging efficiency of 95.2%, and it was significantly better than the anion-modified microspheres. In addition, in drilling fluids under high temperature and high-salinity conditions, the SSD promotes particle gradation of drilling fluids and improves the zeta potential through its own plugging and synergistic effect with clay, which significantly improves the comprehensive performance of drilling fluids, such as stability, rheological performance, and filtration reduction performance. The development of SSD provides a new idea for research of high-temperature and high-salinity-resistant drilling fluid agents. [ABSTRACT FROM AUTHOR]

The object of the research is elastic plates located across the movement of the solution on the vibrosieve. The problem of uniform distribution of material on the surface of the sieve is considered, which is solved with the help of the design proposed in the work. Tensometry was used as a research method with subsequent processing of the results on an elector computer. In the course of the research, an analog-to-digital converter developed and manufactured at the Department of Mechanization of Construction Processes of the National University «Yuri Kondratyuk Poltava Polytechnic» (Ukraine) was used. As well as a computer with a free COM-1 port, «PROGRAM.EXE» software and a spreadsheet editor, strain gauges in the form of strain gauges with two pasted tensor resistors connected by a half-bridge circuit. The paper proposes a fundamentally new scheme of a vibrosieve with additional working bodies in the form of elastic plates located across the movement of the solution on the sieve. The elasticity and mass of the plates are selected in such a way that their oscillations during the operation of the vibrosieve exciter are close to resonance. At the same time, the mode of vibration of the vibrosieve itself is far beyond resonance. As a result, a higher-quality and energy-efficient cleaning of the washing liquid will be obtained. This is due to the fact that the proposed cleaning method has a number of features, in particular, dispersion of drilling fluid over the entire surface of the vibrosieve and maximum loading of the entire working surface of the sieve to avoid dead zones. Thanks to this, it is possible to obtain resonant oscillations. In comparison with known analogs that work in a resonant mode, this provides advantages in the cleaning of drilling mud. The amplitude of oscillations of elastic plates reaches 1.2–1.5 mm, which is significantly greater than the amplitude of oscillations of a vibrating table. In practice, it will be possible to use the proposed fundamentally new scheme of a vibrosieve with additional working bodies in the form of elastic plates that work in a resonant mode, as a way of supplementing vibrosieves that are in use or new when manufactured at manufacturers’ factories. [ABSTRACT FROM AUTHOR]

In order to cope with the complexity of drilling encounters the use of nanoparticle materials to improve the plugging performance of drilling fluids as one of the countermeasures has attracted widespread attention. Nanoparticle materials are selected to optimize the plugging performance of drilling fluids and the microscopic morphology salt resistance rheology and filter loss wall building properties of various nanoparticle materials are compared and analyzed. The result showed that nanoparticle materials produce agglomeration effect in aqueous solution due to their large surface free energy and the agglomerated DS0 particle size is between 1 - 10 and their dispersed particle size is not affected by salt concentration and can coexist with salt ions added in drilling fluid. By comparing the effects of different nanoparticles on the viscous cut and filter lost wall-building properties of the base slurry it was obtained that the Si02 nanoparticles have better compatibility and sealing performance compared with other particle materials and when they were added to 1.5 Si02 nanoparticles in 5 base slurry the filter lost of the base slurry was reduced from 34.5 mL to 23 mLand the filter cake thickness was reduced from 7. 2 mm to 2 mm. The addition of nano-Si02 particles in the potassium-based polysulfide drifting fluid can reduce the PPT filtration lost of drilling fluid from 12 mL to 8 mL which has good sealing effect in low permeability layer and can cope with the leakage problem in dense formations and has broad application prospects. [ABSTRACT FROM AUTHOR]

In recent years, the problem of tight sandstone reservoir damage and protection has attracted the attention of scholars. Due to the existence of natural fracture channel communication, the fluids can easily enter the reservoir along the fractures during the development of fractured tight reservoirs and cause serious damage to the reservoir. In order to investigate the degree and mechanism of mud damage to fractured reservoirs, this paper conducts mud intrusion damage experiments with fractured tight sandstone reservoirs in Tarim Kucha Piedmont block as the research object. The experimental results show that the mud intrusion process can be divided into four stages according to the formation process of mud cake, namely, no mud cake stage, mud cake rapid generation stage, mud cake dynamic equilibrium stage and formation of sealing stage; the mud intrusion rate is affected by the reservoir permeability, mud cake permeability, fluid properties and specific gravity, and when the reservoir permeability is higher than the critical permeability, the intrusion rate is mainly determined by the filter cake permeability; by Scanning electron microscope results show that the blockage state of mud solid phase particles in core pore throat is divided into three kinds: blockage, adhesion and filling, and different blockage states have different degrees of damage to reservoir permeability. The mud dynamic damage analysis and solid-phase particle intrusion study obtained in this paper can help improve the complex reservoir simulator, which has certain guiding significance for the field construction operation and mud optimization. [ABSTRACT FROM AUTHOR]

The influence of different weighting agent on the performance of synthetic drilling fluid system (SBM) were studied in this work. Based on the MODRILL drilling fluid system of China Oilfield Services Co., LTD., the variation of SBM performance with 2.04 g/cm³ were investigated with different weighting agent of 4.3 g/cm³ Barite, 4.4 g/cm³ Barite and 4.8 g/cm³ Trimanganese tetra oxide with the ratio of 10∶0∶0、0∶10∶0、5∶0∶5、6∶0∶4、7∶0∶3、8∶0∶2、5∶5∶0. The results showed that the rheological property, emulsion-breaking voltage and high temperature and pressure filtration are affected by the different weighting agent. The apparent viscosity and the plastic viscosity would be decreased and the yield point and 6 rpm reading would be increased with the increasing trimanganese tetra oxide. The emulsion-breaking voltage would be decreased with the increasing trimanganese tetra oxide. The high temperature and high pressure filtration would be substantially increased when adding the increasing trimanganese tetra oxide. The above conclusions were verified in the filed test by studying the effect of weighting agent on the performance of synthetic drilling fluids. [ABSTRACT FROM AUTHOR]

Drilling the broken formations in the faulted fractured reservoirs in west Sichuan has been encountered with frequent drill pipe sticking and a well is very difficult to be drilled in accordance with the designed parameters. Geological characteristics analyses and laboratory evaluation results have shown that the rocks in the faulted fractured broken formations are weakly bonded and are developed with microfractures. When a liquid invades into the microfractures, the microfractures extend and the integrity and mechanical property of the rocks are damaged, which in turn changes the status of the effective stresses of the rocks around the borehole and results in borehole collapse. Based on this conclusion, a high temperature chemical borehole wall strengthening agent was developed and a high efficiency plugging agent selected to formulate a drilling fluid with the capacity of plugging and strengthening the borehole walls in the faulted and fractured formations. This drilling fluid, with an enhanced plugging and strengthening capacity, has been successfully used in drilling several wells, including the well M6, and the walls of the borehole penetrating the broken faulted fractured formations were maintained stable during drilling. This drilling fluid will have a good application prospect. [ABSTRACT FROM AUTHOR]

DFT simulation was used to investigate the bonding effects of different polar segments on iron (001) surface. These polar segments were intercepted from the hydrophilic chain segments of oleic acid amide lubricants, include primary amine, secondary amine, amide, and hydroxyl. Results indicated that amide group, primary amine group, and hydroxyl group generated the most stable adsorption at the bridge site of Fe (001) surface, and secondary amino group generated the most stable adsorption on the top site of Fe (001) surface. The adsorption energy in descending order were primary amine group, secondary amino group, hydroxyl group, and amide group. Results of population analysis indicated that the orbital population of four polar groups changed during the process and obtained electrons from Fe (001) surface. Among them, secondary amino group obtained 0.16e electrons, primary amino and amide group obtained 0.09e electrons, and hydroxyl group obtained the lowest number of electrons at 0.08e. Results of DOS analysis showed that there exist DOS overlap between 2p orbitals of N and 3p、4s orbitals of iron, with chemical bonding effect. In the extreme pressure lubrication test and four ball friction test results, the lubrication coefficient reduction rate of oleic acid Diethylenetriamine is 83.6%, higher than 78.2% of oleic acid diethanolamide, and the wear scar radius is 287.184 μ m. The wear radius is lower than that of oleic acid diethanolamide. The experimental results indicate that surfactants containing amine and amide groups have better lubrication performance than surfactants containing hydroxyl groups. [ABSTRACT FROM AUTHOR]

This paper reviews the evaluation methods and development of micro and nano plugging performance of drilling fluids at home and abroad, and describes the characteristics of each evaluation method・ And the development of intelligent and precise micro-nano plugging evaluation methods is prospected ・ It provides a new idea for the development of efficient, intelligent and grounded microplugging evaluation methods. [ABSTRACT FROM AUTHOR]

In-situ pressure-preserved coring (IPP-Coring) is considered to be the most reliable and efficient method for the identification of the scale of oil and gas resources. During IPP-Coring, because the rotation behavior of the pressure controller valve cover in different medium environments is unclear, interference between the valve cover and inner pipe may occur and negatively affect the IPP-Coring success rate. To address this issue, we conducted a series of indoor experiments employing a high-speed camera to gain greater insights into the valve cover rotation behavior in different medium environments, e.g., air, water, and simulated drilling fluids. The results indicated that the variation in the valve cover rotation angle in the air and fluid environments can be described by a one-phase exponential decay function with a constant time parameter and by biphasic dose response function, respectively. The rotation behavior in the fluid environments exhibited distinct elastic and gravitational acceleration zones. In the fluid environments, the density clearly impacted the valve cover closing time and rotation behavior, whereas the effect of viscosity was very slight. This can be attributed to the negligible influence of the fluid viscosity on the drag coefficient found in this study; meanwhile, the density can increase the buoyancy and the time period during which the valve cover experienced a high drag coefficient. Considering these results, control schemes for the valve cover rotation behavior during IPP-Coring were proposed for different layers and geological conditions in which the different drilling fluids should be used, e.g., the use of a high-density valve cover in high-pore pressure layers. [ABSTRACT FROM AUTHOR]

This paper reviews the research status of biopolymer in drilling fluid, fracturing fluid, water shutoff profile control, enhanced oil recovery, oilfield water treatment, etc. The application of biopolymer in petroleum industry can effectively make up for the deficiency of synthetic polymer, effectively achieve oil field stimulation, and reduce environmental pollution at the same time, its application has great advantages. Finally, the application of biopolymers in petroleum industry is summarized, aiming to provide reference for the development and application of biopolymers. [ABSTRACT FROM AUTHOR]

Water-soluble polymers are used to improve drilling operations to ensure that oil and gas wells are drilled in less time and completed with minimized formation damage. However, excessive utilization of these polymers additives may have implication on the drilling outcomes. In this work, drilling fluids comprising of different compositions of polyanionic cellulose (PAC), and starch; and a constant amount of bentonite were formulated to examine the effects of excessive use of each additive or their combinations in a water-based drilling fluid (WBDF). The fluid properties were further investigated at low pressure and low temperature (LPLT) as well as high pressure and high temperature (HPHT). The results suggest that the viscosities of the fluid are not only dependent on the shear rate, shear stress, and composition but also on the temperature and pressure. Model plots of shear stress (Pa) against shear rate (s−1) using the Power law, Bingham plastic and Herschel-Bulley shows that all composition have low viscosity and low yield point. Increasing the amount of additive increases, the equivalent circulating density (ECD) which may increase differential sticking and consequent formation damage. [ABSTRACT FROM AUTHOR]

Designing an effective drilling mud is a critical aspect of the drilling process. A well-designed drilling mud should not only provide efficient mud hydraulics but also fulfill three important functions: enhancing mud rheology, inhibiting hydrate formation in deepwater drilling, and suppressing shale swelling when drilling through shale formations. Achieving these functions often requires the use of various additives, but these additives are often expensive, non-biodegradable, and have significant environmental impacts. To address these concerns, researchers have explored the potential applications of ionic liquids and deep eutectic solvents in drilling mud design, which have shown promising results. However, an even more environmentally friendly alternative has emerged in the form of natural deep eutectic solvents (NADES). This research focuses on an in-house-prepared NADES based on calcium chloride and glycerine, with a ratio of 1:4, prepared at 60 °C, and utilizes it as a drilling mud additive following the API 13 B-1 standards and checks its candidacy as a rheology modifier, hydrates, and shale inhibitor. The findings of the study demonstrate that the NADES-based mud significantly improves the overall yield point to plastic viscosity ratio (YP/PV) of the mud, provides good gel strength, and inhibits hydrate formation by up to 80%. Additionally, it has shown an impressive 62.8% inhibition of shale swelling while allowing for 84.1% improved shale recovery. Moreover, the NADES-based mud exhibits a 28% and 25% reduction in mud filtrate and mud cake thickness, respectively, which is further supported by the results of XRD, zeta potential, and surface tension. Based on these positive outcomes, the calcium chloride–glycerine NADES-based mud is recommended as a versatile drilling mud additive suitable for various industrial applications. Furthermore, it presents a more environmentally friendly option compared to traditional additives, addressing concerns about cost, biodegradability, and environmental impact in the drilling process for an ultimate global impact. [ABSTRACT FROM AUTHOR]

Combining smart polymers and nano-silica is an effective method to prevent free water intrusion into micro-nanopores of shale, maintaining the wellbore stability in the drilling process. A core–shell structure nano-plugging agent (NPA) for water-based drilling fluid was synthesized through modifying nano-SiO2 by using N-isopropylacrylamide, 2-acrylamide-2-methylpropane-sulfonic acid and KH-570. The structure and properties of NPA were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, particle size distribution, and transmission electron microscopy methods. Results show that NPA presents a good thermal stability with the decomposition temperature of 370 °C. The median particle size of NPA is 193 nm. The results of the pressure transfer experiments indicate that NPA presents a good sealing performance. The permeability of the cores after NPA sealing was significantly reduced to 0.031 × 10–7 μm2. After reaching the response temperature, the wetting angle of the shale surface treated by NPA is 77.22°. After aging at 150 °C for 16 h, the FLHTHP of the water-based drilling fluid system was controlled within 5 mL. NPA can enhance wellbore stability and effectively reduce the leakage of the drilling fluid during drilling process. [ABSTRACT FROM AUTHOR]

During the development of the carbonate reservoir of the Tahe oilfield, the conventional polysulfonate drilling fluid damages reservoir duo to non-acid-soluble solid phase after loss, and sulfonalized agent does not conform to the concept of green development. The oilfield water is introduced to formulate a solid free drilling fluid to avoid damage reservoir from solid, and the key treatment agents such as anti-high temperature anti-calcium viscosifier, flow pattern modifiers, high-temperature anti-calcium polymer filtrate reducer. The dual-protective oilfield water drilling fluids system without solid was developed. Indoor evaluation datas show that the drilling fluid was heat resistant to 150 ℃，the ratio between yield point and plastic viscosity is as high as 0.68～0.76 Pa/mPa·s, the EC50 value of biological toxicity indicators is as high as 28,600 mg/L, and the bio-degradation index BOD5 /CODCr is as high as 21.35%. The dynamic permeability recovery value is as high as 91.8%, which has good formation damage control performance. The developed dual-protective oilfield water drilling fluids without solid were successfully used in more than ten sidetrack wells,and the application effect was significant. [ABSTRACT FROM AUTHOR]

In order to improve the bubble inhibition and environmental protection performance of the waterproof locking agent for drilling fluid, a natural modified product SMFS-1 was synthesized from alginic acid, 2-(2-aminoethylamino)ethanol (AEEA), epichlorohydrin (ECH) and pentaerythritol (PETP) as raw materials. The molecular structure was characterized by Fourier infrared spectrometer (FT-IR). The test results of waterproof lock performance show that the surface tension of aqueous solution can be reduced to less than 25 mN/m after the addition of SMFS-1, which can reduce the volume of core self-absorption, promote the change of rock surface from hydrophilic to neutral, and increase the recovery value of core permeability to more than 80%. SMFS-1 is resistant to temperature up to 120 ℃, has excellent adsorption performance, no bubbling effect, and has little impact on rheological properties and filtration properties of drilling fluid. The environmental performance test results showed that the semi-lethal concentration (EC50) of SMFS-1 was 32,250 mg/L, and the biodegradability evaluation index (Y) was 17.36, which met the emission standard and was easy to biodegrade. [ABSTRACT FROM AUTHOR]

In this study, a drilling fluid prediction method based on an online sequential extreme learning machine (OS-ELM) is proposed, which is prepared for water well drilling on the muddy clay formation of Tarim Basin, Qinghai Province. First, we investigated the mechanism linking mix ratio to fluid performance, allowing us to employ an OS-ELM algorithm derived from the extreme learning machine. Particularly, the proposed prediction method is bidirectional to identify an appropriate slurry formulation. The forward prediction model is established to predict the fluid performance, where the mud additive contents are inputs, and the drilling fluid properties parameters are outputs. Correspondingly, the backward prediction model is established to modify the slurry formula, where differences in the drilling fluid properties are inputs and percentages of slurry additives amount are output. The simulation results show that the two-direction OS-ELM prediction model can better predict the drilling fluid properties in water well drilling. [ABSTRACT FROM AUTHOR]