In this study, nanosilica-based polymers were synthesized and optimized for water-based drilling fluid applications using response surface methodology (RSM). The synthesis process involved the polymerization of methacryloyloxyethyl trimethyl ammonium chloride (DMC), methacrylic acid (MAA), and silane-modified nanosilica (KH570-SiO2) under varying conditions of temperature, initiator concentration, and pH. Characterization by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (1H-NMR), thermogravimetric analysis, and optical microscopy confirmed the successful polymerization and incorporation of nanosilica while maintaining structural integrity and thermal stability. The reaction conditions were optimized using RSM with variables including the temperature, pH, and initiator concentration. The optimized conditions (70.9 °C, pH 7, and 0.57 wt.% initiator concentration) resulted in significant enhancements in drilling fluid performance, including a 46.0% reduction in filtration loss, a 28.6% decrease in coefficient of friction (CoF), and improved cutting-carrying capacity (YP/PV ratio). Post-reaction analyses demonstrated the thermal stability and reusability of the synthesized polymers under high-temperature conditions, confirming their applicability in field operations. This work highlights the potential of nanosilica-based polymers in improving drilling fluid performance, offering insights into optimization strategies and enhanced material stability.

The increasing demand for oil and gas resources, coupled with growing concerns over the environmental impact of conventional chemical agents, has heightened the need for sustainable alternatives. CO2 responsive materials, which utilize CO2 as an environmentally friendly stimulus, have emerged as promising solutions for improving chemical performance while minimizing environmental impact in petroleum engineering. This review systematically examines the functional groups, response mechanisms, and synthesis strategies of CO2 responsive polymers in oil and gas operations, with particular emphasis on their applications in drilling and reservoir engineering. The review explores the relationship between the reversibility of CO2 responsive materials and their environmental adaptability, focusing on applications in cementing, oil-water separation, gas channeling plugging, viscosity modification, and enhanced oil recovery. By evaluating response mechanisms and environmental adaptability, this work offers valuable insights into the optimization of CO2 responsive materials for practical use in petroleum operations. Additionally, challenges such as response sensitivity and long-term stability are critically explored, and potential solutions and strategies are proposed. The findings aim to support the low-carbon transformation of the oil industry and promote the adoption of sustainable practices in hydrocarbon extraction.

To solve the problem of wellbore instability, cationic asphalt particles obtained through synthesis of asphalt and dimethyl sulphate (CH3O)2SO2 at molar ratio of 1:1 were incorporated into water-based mud. After chemical synthesis, various characterization techniques were performed to confirm suitability of the synthesized cationic asphalt particles for enhancing wellbore stability and water-based mud properties. These tests include: particle size analysis, Zeta Potential test, Fourier-Transform Infrared Spectroscopy (FT-IR), low-pressure/lowtemperature (LPLT) and High-pressure/High-temperature (HPHT) rheology evaluation, LPLT/HPHT fluid loss test, shale dispersion tests, and clay swelling tests. Owing to the displacement of hydrogen present in the asphalt amine group (N-H) by the (CH3)2 during chemical synthesis, asphalt particle size changed from an initial 50 mu m to 356.2 nm. FT-IR spectroscopy indicated formation of new C-N covalent bond at wavenumber 1200cm-1 (90 % Transmittance) highlighting the occurrence of chemical reaction. The cationic asphalt particles zeta potential values ranged between-39 mV to-65 mV, thereby highlighting the synthesized asphalt particles excellent colloid stability in aqueous media. The asphalt particles induced fluid loss reduction when incorporated with CMC into the base mud. Due to encapsulation, electrochemical attractive and bridging forces between the (CH3O)2SO2 cationic asphalt and net negatively charged clay surface, a shale recovery percentage of 77.7 % was achieved while clay swelling test results highlighted clay swelling index of 0.73 mm. These indicate that the synthesized cationic asphalt particles can reduce clay swelling and shale dispersion thereby improving wellbore stability.

The objective of this study is to improve the performance of water-based drilling fluids for high temperature, salt and calcium resistance in the exploration of deep and ultra-deep wells. In this study, poly(anionic cellulose), 2-acrylamido-2-methylpropanesulfonic acid (AMPS), diallyldimethyl ammonium chloride (DMDAAC), N,N-dimethylacrylamide (DMAA), sodium p-styrene sulfonate (SSS) and silica nanoparticles were used as raw materials to form copolymer PAC-DDAS-SiO2 by free radical copolymerization in aqueous solution. Using X-ray photoelectron spectroscopy (XPS), Monomers were polymerized successfully. The rheological properties of the drilling fluid were maintained after the addition of copolymers to the drilling fluid, the filtration volume after aging at 260 degrees C is only 8 mL. At the same time, the 35 wt% Cacl(2) copolymer base slurry aged at 200 degrees C showed a filtration loss of only 14.4 mL. The polymer helped the drilling fluid resist 10 wt% Nacl at 260 degrees C. Analysis of the filter cake after ageing, the microscopic morphology of clay-polymer interactions in the drilling fluid after ageing and the particle size of the drilling fluid was carried out. The presence of a large number of anionic groups in the chains on the copolymer spheres formed hydrogen and ionic bonds with the clay, adsorbed Na+ and Ca2+ and prevented the intrusion, thus ensuring the normal size of the clay particles, resulting in the formation of a wider particle size distribution phenomenon in the drilling fluid, dense filter cake and reduced filtration volume.

The effect of Nano asphalt shale stabilizer on water-based drilling mud properties and shale dispersion is presented in this work. To analyze its impact on water-based mud functionality, rheological and fluid loss tests were performed before and after hot rolling at 130 ℃. Hot rolling shale dispersion test was performed by dispersing 20 g of shale cuttings into formulations containing different test samples and hot rolled for 16 h at temperature 120 ℃. After which, the shale recovery percentage was calculated. To evaluate the effectiveness of the Asphalt shale stabilizer on clay hydration and swelling, clay swelling test was performed. Results from rheological tests showed that, increasing the concentration of asphalts in the water-based mud led to an increase in rheological properties such as: apparent viscosity and gel strength (10 s, 10 min). This suggests its ability to improve cutting carrying, suspension and hole cleaning capacity in addition to micropore plugging. Further increase in mud rheological properties was observed after hot rolling at 130 ℃. Interestingly, fluid loss was however not significantly affected by the addition of 2% w/v and 3% w/v asphalt shale stabilizer, as results indicated a slight decrease in fluid loss in comparison with the water-based mud. From the shale dispersion test, the percentage recovery of shale cuttings was 76.5%, indicating its capacity to reduce shale cutting disintegration and improve shale cutting carrying capacity. Results from this investigation presents the in-house developed asphalt shale stabilizer as a promising shale stabilizing agent due to its ability to improve water-based mud rheological properties, reduce shale dispersion and enhance plugging in ultra-tiny pores of shale formations.

This article presents extensive analysis and review on recent developments in smart fluids as well as future opportunities of smart drilling fluids utilization in oil and gas well drilling while focusing on the following smart fluids: smart nanoparticles, electrorheological, magnetorheological, and viscoelastic surfactant (VES) fluids. The distinctive properties of nanoparticles such as tiny particle sizes, high specific surface area, mechanical strength, and thermal stability make them suitable for utilization in drilling fluids. In bentonite water-based drilling fluid systems, this review suggests that charged nanoparticles are capable of displacing exchangeable ions in between bentonite clay platelets, thereby forming intercalates which can interact with clay surfaces through electrostatic attraction or repulsion. In improving wellbore stability, it is presented in this review that nanoparticles are able to invade and plug ultratiny pore spaces in shale formations, thereby further enhancing shale formations’ mechanical strength and wellbore stability. According to this review, the magnitude of changes in properties of smart electrorheological and magnetorheological fluids largely depends on the intensity of applied electric and magnetic fields. The intensity of smart fluids properties alteration due to applied field would equally depend on wt.% concentration and chemical compositions of particles susceptible to electric and magnetic fields. Based on review carried out on VES smart fluids, attractive and repulsive forces in the smart VES fluids solution result in the formation of micelles which can cause changes in viscoelastic property of the formulated smart viscoelastic fluids. The more the concentration of charged ions in the base fluid which VES fluids come in contact with, the higher the viscoelasticity of the smart VES fluids. According to this review, utilization of smart materials in drilling fluids can result in meeting oil and gas well drilling technical challenges including enhancing wellbore stability, improving hole cleaning performance, lost circulation control, fluid loss control, enhancing rate of penetration, pressure drop control, and easing cutting carrying efficiency of drilling fluids. This review equally suggests that the utilization of smart fluids such as smart magnetorheological and electrorheological fluids would facilitate drilling automation and real-time data acquisition processes, which is the future technology in oil and gas drilling.

智能流体作为一种物理性能"可控"的智能材料,在航天、生物、医疗以及微电子等行业得到了广泛应用.根据智能流体响应条件,将智能流体分为了外场可控智能流体(以磁流变流体和电流变流体为代表)和刺激响应可控智能流体(以智能水凝胶为代表),系统总结了智能流体的流变机理、研究现状,指出将纳米材料引入智能流体是目前研究热点.在此基础上,介绍了可应用于钻井液中的智能流体室内研究进展,分析了智能流体应用于钻井液的可行性.最后结合智慧油田发展需求,提出了开发智能钻井液、研发智能钻井设备以及智能钻井液操控系统是未来智能钻井发展新方向.

The effect of corrosion inhibitor Benzotriazole on synthetic-based mud system was studied. Rheological performance of the benzotriazole enhanced synthetic-based fluid system was studied and compared against the base mud. To study its effect on dynamic wellbore conditions, different drilling fluid compositions were placed in a hot rolling oven for 16 hours at temperatures 150 °C and 170°C and the effect of temperature on mud properties were studied. Tests carried out include rheological test (before and after hot rolling), filtrate pH, lubricity test, and fluid loss test. The corrosion penetration rate was studied using the weight loss method. Based on experiment results, the synthetic-based mud system which comprised of benzotriazole displayed a reduction in coefficient of friction up to 95.93%. At ambient condition, optimal ratio of mineral oil:benzotriazole (M:B) which gives best lubricity performance on synthetic-based mud system is 80:20. This leads to improved corrosion inhibition and lubricity of the synthetic-based fluid by reducing the coefficient of friction up to 90.13%. Increased temperature led to further decrease in coefficient of friction with a % torque reduction of 95.93 displayed by the 80:20 ratio M:B mud composition at 170 °C. Significant alterations of the mud composition rheological and fluid loss parameters before and after exposure to high temperature in hot rolling oven were not observed. pH values were maintained ≥7 at the dynamic conditions highlighting solubility of the formulated fluid composition and absence of contaminants which can pose significant threats to the rates of corrosion in drill pipes. Increasing the concentration of Benzotriazole led to a reduction in corrosion rate. However, as the temperature effect increased, the corrosion rate elevated. Based on results from this investigation, it was concluded that Benzotriazole can be applied as a corrosion inhibitor in a synthetic-based drilling fluid system as an alternative corrosion inhibitor without significant alteration of the base mud properties. Benefits of this will be the optimization of extended reach well drilling operations due to excellent lubricity performance, corrosion rate reduction, compatibility with HPHT wellbore condition and fluid loss control.

石油的发展关系到国家的工业化水平和国际竞争力,系统梳理石油领域的发展态势以及研究热点,可以为石油研究领域学者和机构提供科研依据和战略参考.以Web of Science核心合集数据库为数据源,从论文产出、研究机构、核心作者、研究热点等角度对2008-2018年全球石油工程的文献数据进行了文献计量学可视化分析.结果表明:近10年石油工程的发文量呈现增加趋势,论文发表集中在中国、美国和俄罗斯等国家;目前该领域研究热点为提高采收率、水力压裂、非常规油气资源、重油开发、油藏数值模拟以及原油脱硫等方面;而机器学习和非常规油气藏开发将是该领域未来的研究前沿.该研究结果可为石油工程领域科研人员和科研机构把握领域走向、洞悉未来研究热点等提供科研参考.

生物柴油主要成分是脂肪酸烷基酯,其闭杯闪点高不易着火,且不含或含少量硫和芳香烃,其性能稳定、毒性低、无荧光性,对测井无影响,是良好的酯基钻井液基液.因常规油基钻井液处理剂与生物柴油配伍性较差,笔者针对生物柴油包水钻井液的处理剂进行了优选,优选出主乳化剂TC-PEM、辅乳化剂TC-GSEM、提切剂UP-GEL和降滤失剂UP-GEL,并通过对生物柴油包水钻井液性能评价实验,研制出3种不同密度的生物柴油包水钻井液体系.该体系具有良好的抗温性,抗温为120℃,抗淡水侵能力为15％、抗CaO能力为2％;生物柴油包水钻井液体系生物降解性评级为容易,是一种环境友好型钻井液体系.现场应用表明,该钻井液具有良好的流变性能,提高了机械转速,大幅度缩短了建井周期.

Biodiesel-based drilling fluid (BBDF) draws considerable attention because biodiesel has excellent environmental acceptability and great potential to provide high drilling performance. There are some investigations reported about BBDF both in laboratory and in the field recently, demonstrating its feasibility. In contrast to traditional petrodiesel and mineral oil, biodiesel has some chemical activity which affects the reliability of BBDF in drilling environment. This paper details the principles and strategies for developing and selecting additives of BBDF. A variety of experimental results obtained by laboratory tests were presented to elucidate the importance of suitable additives for an eligible BBDF. Electrical stability test and centrifuge test were conducted to evaluate the effectiveness of emulsifier. A six-speed viscometer and a high-pressure-high-temperature (HPHT) rheometer were used to measure the parameters of BBDF to evaluate organophilic clays and rheological modifiers. Density test was performed to investigate the suspendability of the fluids. Hot rolling treatment was carried out to study the thermal tolerance of the fluids. The laboratory results and the literature showed that both lime content and calcium chloride concentration have significant effects on the stability and rheological parameters of BBDF. Even moderate amount of lime in BBDF will significantly decrease the stability of BBDF. The effect of calcium chloride concentration on BBDF varies according to the type of emulsifier. A compound emulsifier based on fatty alkanolamides and alkyl sulfonates exhibits reliable ability to prepare stable, thermal-tolerate invert biodiesel emulsion. It offers biodiesel emulsion reduced viscosity compared to those given by traditional Span/Tween emulsifier combinations. For another, commercial organophilic clays cannot give satisfactory rheological parameters because the viscosity-temperature profile of BBDF is often steeper than those of traditional oil based drilling fluids (OBDFs). Therefore, rheological modifier should be used to compensate the viscosity loss of BBDF under high-temperature conditions. A condensate of alkoxylated fatty amine and polycarboxylic acid showed good performance to provide a relatively flat rheological profile. Some empirical laws, principles and strategies are summarized for BBDF additive selection. One is that the combinations of non-ionic and anionic emulsifiers have better effectiveness for biodiesel. The other conclusion is that lime content must be strictly controlled. With the boom of the biodiesel industry, it is predicted BBDF will take a place in the family of drilling fluid. However, most previous works show that BBDF may be not satisfactory when the temperature is over 120 Celsius degrees. This work presents valuable experience for further improvement of this promising drilling fluid.

Nanomaterials have drawn considerable attention of the oil and gas industry due to their peculiar properties and interesting behaviors. Many experiments, trials and practices were conducted by petroleum scientists and engineers in the last two decades to use various novel nanomaterials to improve exploration and production. Based on the published literature, this article comprehensively reviews the strategies and experience of nanomaterial application in frac fluids, the current problems, and relevant challenges. Based on elaborated design, the nanomaterials such as nano-sized metal, metal oxide, silica, carbonate, carbon, polymer, fiber, organic-inorganic hybrid and other composites can be incorporated in frac fluids to greatly enhance or precisely tune the properties and performances. Consequently, nanomaterial-assisted frac fluids perform well in different aspects including density, rheology, stability, heat conductivity, specific heat capacity, fluid loss, breaking, clean up, proppant suspendability and frictional drag. To optimize the performance and cost-effectiveness of nano-frac fluids, advanced principles and theories in physical chemistry, heat and mass transfer, mechanics and rheology along with industrial design philosophy have been considered and applied. According to the investigation of the literature, nanomaterials have successfully fulfilled the following functions in frac fluids: (1) Improving the rheological behavior by intermolecular interactions (e.g., pseudo-crosslinking in frac fluids, or changing the aggregation pattern of surface-active molecules in surfactant based fluids); (2) Increasing the stability of fluids by enhancing the interfacial strength and toughness, especially in foams and emulsions; (3) Forming a low-permeability pseudo-filter cake to lower the fluid loss; (4) Increasing the viscosifying effect of polymers, which dramatically decreases the required loading of polymer in the fluid; (5) Boosting the thermal stability of frac fluids; (6) Improving the regained fracture conductivity; (7) Reducing the frictional drag of frac fluids; (8) Helping self-suspended proppants achieve better performance and (9) Reducing the required displacing pressure for the residual frac fluid by decreasing interfacial tension to help clean up. These achievements, along with the related design ideas, are reviewed. This paper also discusses the major difficulties and challenges for nano-frac fluids including compatibility, cost and HSE issues. Comprehensive laboratory work should be performed before field application to ensure the reliability of nano-assisted fluid formulations. Large-scale industrial production and a steady supply of nanomaterials will promote the application of nano-frac fluids. Exposure risk, eco-toxicity and biodegradability of nanomateials should be paid more attention. Incorporating the attractive, cutting-edged achievements in chemical and material sciences, nano-frac fluid is predicted to be fully accepted by the petroleum industry due to its great potential and the increasingly declining price of nanomaterials.

为了提高页岩气现场配液施工效率,降低不同压裂液间配伍性对压裂液性能的影响,利用AM、DMC、DMDB为原料,采用混合胶束水溶液聚合,合成一种滑溜水胶液一体化用稠化剂.用管路摩阻仪和高温流变仪对滑溜水体系降阻性能和组装压裂液体系耐温耐剪切性能进行评价.结果表明,该疏水缔合聚合物溶解时间小于2 min,0.1％的滑溜水黏度达到10 mPa·s,降阻率为65.7％,组装压裂液在90℃,170 s-1条件下剪切2 h,表观黏度大于50 mPa·s.滑溜水和胶液具有良好的降阻效果及耐温耐剪切性,能够满足滑溜水和压裂液在线混配的要求,可以实现滑溜水胶液一体化.

粘度是度量流体粘滞性大小的物理量,粘度的测量在许多领域都有着重要的作用.不同领域适用不同的粘度测量方法和仪器,选择合适的粘度测量方法和仪器对科学研究和工业生产至关重要.旋转法、毛细管法、落体法和振动法是几种常见的粘度测量方法,它们的原理、优缺点、适用范围和改进方向都有所不同,而现在的研究热点是基于新技术的非接触式测量方法.

Waste drilling fluids (WDF) is a complex mixture of different additives with different chemical and biologic properties, which have no biodegradability and seriously pollute the soil system without any disposal. After the later stage treatments, like landfill and solidification, waste drilling fluids also have potential detrimental to the environment and health. In this paper, a formula has been studied that can turn the waste water-based drilling fluids into an environment friendly soil. The treatment process can realize the harmless disposal and effective utilization of water-based drilling wastes. In the laboratory column study, by assessing the germination time and growth of ten kinds of plants which were grown on the high quality soil mixture with the waste drilling fluids (10:1, wt:wt), the Festuca arundinacea seed was selected to evaluate the quality of the soil. The formulas were used as a treatment agent mixing with drilling wastes collected from drilling well sites in Dagang, Tianjing, China with design of orthogonal experiment. The analysis was comprised of evaluation of heavy metals, chemical oxygen demand (COD), soluble salt content, and pH. The formula (20%coal + 10%solid sludge +5%chips) was proposed as a low-cost strategy to reduce leaching of toxic elements, and improve plant establishment. The concentrations of heavy metals in leachate solution exacting from the soil were lower than the EPA toxicity limit set by USEPA. The pH was approximately 7 similar to 8. COD was less than 100 mg O-2/L and the soluble salt content was less than 25 g/kg. In the Field application, the environment friendly formula developed in this study has been successfully applied to Dagang Oilfield. The treated waste drilling fluids are favorable to the growth of the plants (the soil organic matter is more than 30 g/kg, the porosity is more than 50%). The treatment process is easy to handle, low-cost (< 100RMB/m(3)) and realizes a new, sustainable soil resources for landscaping. (C) 2017 Published by Elsevier B.V.

Abstract The use of organophilic clays as additives for providing proper rheological and filtration properties in non-aqueous drilling fluids (NADFs) has long been a topic of study. Currently, most of these clays are based on the modification of bentonite with quaternary ammonium salts. As new NADF systems emerging, novel clay-modification technologies are needed urgently to obtain more effective organophilic clays for specific drilling fluids. This paper introduced a modified rectorite designed for biodiesel-based drilling fluid (BBDF). Through a suspension production technique, rectorite, a clay mineral formed by dioctahedral mica layer and dioctahedral smectite layer with a 1:1 type of layer structure and a peculiar banded structure, was modified by non-ionic surfactants. The swell behavior of the modified rectorite in invert biodiesel emulsion was investigated. Effects of this novel organophilic clay on the electrical stability, rheological parameters and suspendability of biodiesel emulsion were also tested. The results showed that some non-ionic surfactants can be intercalated into the structure of rectorite, altering the wetting characteristic of the clay surface. Compared to traditional organophilic bentonite, modified rectorite has better swell performance in biodiesel emulsion. The abilities of modified rectorite to improve yield point (YP) and low end rheology (e.g., 6 rpm reading) of biodiesel emulsion are also significantly stronger than those of traditional organophilic bentonite, suggesting a higher efficiency of adjusting rheology and suspendability. Combined with appropriate rheological modifiers (RMs), the modified rectorite can provide formulated BBDF a great suspendability, which is evidenced by static barite-sag test. Electrical stability of biodiesel emulsion was also enhanced with the addition of the modified rectorite due to the forming of Pickering emulsion. This novel modified clay is a reliable guarantee of steady properties of BBDF. The origin of its good performance can be attributed to the selection of suitable surfactants and the rational preparation technology. Rectorite is widespread all around the world and there are some rectorite mining areas in various countries although the degree of utilization for this clay is still low at present. In view of the relatively lower price of rectorite compared to bentonite, modified rectorite can be considered as a high-performance, cost-effective viscosifier for BBDF and perhaps, other NADFs.

In shale oil and gas exploration,chemical tracer technology is effectively applied to the evaluation of fracturing technology. The precondition for the application of this technology is the establishment of corresponding analysis method.The authors selected 21 kinds of halogenated hydrocarbons as tracer,with stable chemistry character and low stratigraphic background values.And a high sensitivity detection method for the tracer by purge?and?trap and gas chromatography mass spectrometry(GC-MS)was developed. The conditions of purge?and?trap and GC-MS were optimized and the optimum conditions were obtained. The results showed that the detection limits were 0.027-0.162 μg/L. The average recoveries were 74.16%-121.9% with a precision lower than 12.79%(RSD, n=7). The established method is simple and fast,hence is applicable for the determination of tracer in fracturing outlet fluid samples after reservoir reconstruction.

Abstract The traditional methods of treating and disposing waste drilling fluid are encountering severe challenges with the tightening of environmental regulations in China. Commonly used chemical destabilization technology needs to be improved, and treating processes are required to be optimized and updated. This paper details a laboratory investigation on two waste water-based drilling fluids (a high-density drilling fluid and a reservoir drilling fluid) from the rig sites, as well as the corresponding treatment and disposal process design. The laboratory work focused on a solid-liquid separation technique on the basis of chemical flocculation and centrifugation. According to the properties of each waste drilling fluid, different flocculants were added to initiate chemical flocculation. The effects of type and concentration of flocculants as well as treating conditions (including sulfuric acid, dilution ratio, centrifugal speed and agent adding sequence) on the degree of separation were comprehensively investigated. To apply the separation technology in various fields, two integrated processes for collective and in-site treatments were designed and discussed respectively. The results showed that the correct combination of inorganic and polymeric flocculants can lead to a great degree of separation. In particular, a novel flocculant based on modified starch exhibited excellent performance. The molecular weight of polymeric flocculant substantially influences treatment efficiency, which can be explained by the combination of adsorption-bridging and sweep-flocculation mechanisms. Adding sulfuric acid to the waste drilling fluid in treatment is beneficial to solid-liquid separation due to the reduction of electrostatic repulsion between solid particles. Molecular weight of flocculant is also a crucial factor influencing the separation effectiveness and rate. For the two waste fluids studied, the optimal treating conditions were proposed. The weight fraction of separated liquid phase reached higher than 80% and the liquid content of the solid phase was lower than 30%. Detailed analysis and discussion of the advantages of this process were presented. Preliminary field practice of this technique exhibited its satisfactory performance. This highly-integrated technique based on novel chemical agents, rational design and high-efficiency equipment is helpful to deal with the increasing technical and environmental challenges. The information provided in this work offers a reference to relevant researchers, designers and engineers.

Nano-additive is a hot research object in the ifeld of drilling lfuids now. When nano-materials are added into drilling lfu-ids, they can control the rheological property, decrease ifltration rate, and improve temperature resistance and lubricity of drilling lfuids. This paper analyzed nano-materials (e.g. nano SiO2, nano CaCO3, C nano-material and nano-emulsion) in terms of material structure, physical property and chemical property. Then it introduced the working principles and ifeld applications of nano-materials in drilling lfuids. Finally, it proposed to build up a mathematical model based on the unique physical and chemical properties of nano-materials to predict the application results of nano-additives and to reduce the cost of nano-additives by means of combination.

Summary This paper presents an environmentally friendly, biodiesel-based invert-emulsion drilling fluid (BBDF). On the basis of the stable emulsion previously optimized (which was presented in Part 1), several necessary additives, including an organophilic clay (OC), a fluid-loss (FL) -control agent and a rheological modifier (RM), were developed or selected to formulate the BBDF. Numerous laboratory tests of different properties were conducted to evaluate the properties of this drilling fluid. BBDF has a rheological behavior and filtration properties that meet the requirements of drilling operations. It exhibits good shale-inhibition ability, excellent lubricity, and tolerance to contaminants. Low toxicity and great biodegradability are the prominent advantages of this system. After evaluating the suitabilities of known rheological models for BBDF, a hydraulic simulation was carried out on the basis of the Herschel-Bulkley model. BBDF performs similarly to conventional oil-based drilling fluids (OBDFs) subject to deepwater drilling conditions. High performance and great environmental compliance make BBDF a promising option for marine or extended-reach drilling. In addition, novel OC produced from rectorite and nonionic surfactants was successfully introduced into this drilling fluid. This modified rectorite is expected to be a substitute for conventional organobentonite.