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Articles in press have been peer-reviewed and accepted, which are not yet assigned to volumes /issues, but are citable by Digital Object Identifier (DOI).
Display Method:
Study and Application of Stabilization and Differentiated Acidizing Stimulation System for Unconsolidated Sandstone Reservoirs
SHAO Shangqi, LI Shengsheng, LI Xiaonan
Abstract(156) HTML(131) PDF (2828KB)(32)
Abstract:
One of Middle East oilfield main production layers is a sandstone reservoir, primarily composed of sandstone and argillaceous siltstone. The rock is loose and prone to sand production. Conventional acidizing technologies are slow-acting and may even cause sand production. This paper analyze the mechanism of sand production and blockage in the reservoir, and develop a composite acidizing stimulation technology targeted at unconsolidated sandstone reservoirs. Based on the principle of "stabilization first, then stimulation," this technology can not only alleviate well blockage damage but also maintain reservoir stability. Through laboratory experiments, this paper developed a sandstone stabilizer suitable for high scouring flow rates. Under a flow rate of 1800 mL/h, the sand production rate can be stably controlled within 0.01%. Meanwhile, by applying the synergistic principle of different working fluid systems and aiming for "more scale removal, less sand dissolution," a differentially dissolving acidizing and descaling system was developed. Laboratory tests show that the dissolution rate of scale samples in the acid system is ≥95%, while the sand dissolution rate is <25%. The acid fluid can effectively alleviate the dissolution of sandstone minerals and maintain rock structure stability. Field tests have demonstrated that the composite acidizing technology, which follows the "stabilize first, then descale" approach, has increased average production and extended the treatment's effective period, effectively mitigating the problem of sand production in the reservoir. This provides a theoretical basis and practical direction for acidizing treatments in unconsolidated sandstone oilfields.
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Display Method:
FORUM
Research Progress and Key Research Directions of Wellbore Fluids in China and Abroad
WANG Jianhua, SUN Jinsheng
2026, 43(2): 145-151, 160.   doi: 10.12358/j.issn.1001-5620.2026.02.001
Abstract(13) HTML(5) PDF (2383KB)(0)
Abstract:
Wellbore working fluids are critical enabling technologies for the safe and efficient exploration and development of unconventional, deep, and ultra-deep oil and gas resources. This paper reviews and benchmarks domestic and international advances in wellbore fluid technologies. The results show that comparable performance has been achieved in high-performance water-based drilling fluids for unconventional reservoirs and in wellbore fluids for deep and ultra-deep applications, while notable gaps remain in reservoir protection technologies and intelligent control systems. With the continuous deepening of exploration and development, existing wellbore working fluids are still insufficient to meet the increasing demands of deeper, longer, and smarter drilling operations. Therefore, further efforts are required to promote iterative upgrading toward environmentally friendly, high-performance, and intelligent wellbore fluid systems, and to develop fully autonomous formulations integrated with advanced testing and control technologies.
DRILLING FLUID
A Model for Predicting Borehole Wall Stability in High Stress Fractured Formations
WANG Weiji, ZHANG Dujie
2026, 43(2): 152-160.   doi: 10.12358/j.issn.1001-5620.2026.02.002
Abstract(9) HTML(2) PDF (5416KB)(0)
Abstract:
To deal with the wellbore collapse and instability problems encountered in drilling the broken marine carbonate formations in Shunbei and western Sichuan, a visual true triaxial wellbore instability physical simulation experimental platform was prepared and used to study the microstructural characteristics, physiochemical characteristics and mechanical properties of the broken formations, and it was understood that concentrated geostress, formation fragmentation and the mechanical-chemical coupling effect between the drilling fluid and the rocks are the main controlling factors for wellbore instability. By introducing a formation integrity coefficient, a parameter relationship between the “formation integrity coefficient + drilling fluid soaking” and formation mechanics was established. Based on finite element simulation, the distribution of the geostress of the broken formations was revealed. Based on equivalent rock mechanics parameters and taking into account the chemical interaction between drilling fluid and rock, a collapse pressure prediction model based on M-C criterion was constructed. The prediction accuracy of collapse pressure in typical wells, such as the well SHB9X, PZ5-3D and PZ6-5D, is as high as 86.0%-93.9%.
A New High-temperature Tackifier for Solid-free Drilling Fluids
ZHOU Guowei, ZHANG Xin, YAN Weijun, HUA Guiyou, ZHANG Zhenhua, QIU Zhengsong
2026, 43(2): 161-171.   doi: 10.12358/j.issn.1001-5620.2026.02.003
Abstract(1118) HTML(886) PDF (4086KB)(45)
Abstract:
The Ordovician buried-hill reservoir in Liaohe Oilfield exhibits a challenging high-temperature (200 ℃ at reservoir center) and low-pressure (pressure coefficient 1.01~1.06) environment characteristic of typical high-temperature, low-pressure oil/gas reservoirs. To achieve formation protection, a solids-free water based drilling fluid was prioritized, with tackifier selection being critical. Through molecular structure optimization, a novel high-temperature/salt-resistant tackifier was developed using four monomers: N-vinylpyrrolidone (NVP), 2-acrylamido-2-methylpropane sulfonic acid (AMPS), N,N-diethylacrylamide (DEAA), and 1-(3-sulfopropyl)-2-vinylpyridinium hydroxide inner salt. The synthesis employed N,N'-methylene bisacrylamide as crosslinker with potassium persulfate and sodium bisulfite as redox initiators. FTIR and TGA analysis confirmed successful polymerization, demonstrating superior thermal stability with 296.66 ℃ initial decomposition temperature and only 45.96% mass loss during degradation phase, outperforming commercial HE300. The fluid achieved remarkable rheological performance with 722 consistency coefficient (K) at 0.5% concentration. Laboratory evaluations verified exceptional thermal stability up to 220 ℃ and saturated salt tolerance. Field applications demonstrated excellent viscosity-enhancing performance and robust durability of this novel tackifier, providing vital technical support for buried-hill reservoir development and high-temperature formation drilling operations.
Research and Application of Elastic Expanding Bridging Efficiency-Enhancing Material
CUI Kaixiao, LIU Jinhua, LI Daqi
2026, 43(2): 172-178.   doi: 10.12358/j.issn.1001-5620.2026.02.004
Abstract(9) HTML(4) PDF (3148KB)(0)
Abstract:
Current bridging lost circulation materials (LCMs) exhibit poor lost circulation control performance and limited pressure bearing capacity when used in controlling mud losses into complex fractured formations such as those with multiscale fractures and stress-sensitive fractures, and mud losses controlled with these LCMs are easy to re-occur. Based on the idea of enhancing the elasticity and toughness as well as the volumetric expandability of the LCMs, an elastic expanding bridging efficiency-enhancing material was developed. The optimal synthesis formula and conditions were obtained through component optimization experiments. Laboratory evaluations were conducted on the material mechanics, expansion performance and lost circulation control capacity of the elastic expanding bridging efficiency-enhancing material, followed by field application. The research findings show that the elastic expanding bridging efficiency-enhancing material exhibits high compressive strength and good elasticity-toughness before and after expansion. After aging at 160 ℃, the volume of the elastic expanding bridging efficiency-enhancing material can expand to 116.67% of its original volume. Through elastic-tough deformation and continuous three-dimensional expansion, the elastic expanding bridging efficiency-enhancing material can enhance the compactness of the plugging layers and improve their elasticity-toughness, thereby strengthening the pressure-bearing and anti-breathing capacity of the seal. Preliminary field applications of this elastic expanding bridging efficiency-enhancing material in wells with lost circulation in the southwest drilling block have achieved favorable results in mud loss control, demonstrating broad promotion prospects.
Drilling Fluid Technology for Ultra-High Temperature Fractured Bedrock Reservoirs
HAO Shaojun, XING Xing, AN Xiaoxu, WEI Shijun, ZOU Jun, HAO Tian
2026, 43(2): 179-187.   doi: 10.12358/j.issn.1001-5620.2026.02.005
Abstract(7) HTML(2) PDF (2131KB)(0)
Abstract:
The Kunteyi gas field is located in the #1 buried structure of the Kunteyi sag on the northern margin of the Qaidam Basin, the bedrock reservoirs of which are developed with fractures and have a weathering crust, and the formations of which have weak segments and natural channels for mud losses, together with complex geological conditions such as ultra-high temperatures (approximately 200 ℃) and abnormal high pressures (pressure coefficient up to 1.63). To address the drilling fluid challenges confronted in drilling ultra-high temperature bedrock reservoir formations, such as thick and loose mud cakes, low pressure-bearing capacity and ease of lost circulation etc., an ultra-high temperature drilling fluid with high plugging capacity for the prevention of lost circulation was developed through synergistic design of core additives. In the drilling fluid “SC-200+Redu240” are used to construct a high-temperature colloidally stable framework, and “nano-silica + white asphalt NFA-25” used to achieve plugging of the multiscale fractures and finally an integrated function of “filtration control + fracture plugging + wellbore stability” is realized. Experimental results confirm that this drilling fluid functions normally at temperatures up to 200 ℃. After aging, the rates of change in the apparent viscosity and plastic viscosity are both less than 3%, the high-temperature high-pressure filtration rate is less than 12 mL, and the drilling fluid can resist contamination by 15%NaCl. Additionally, the sand-bed filtration rate of the drilling fluid after aging is only 4.2 mL, and the filtration rate for fracture plugging is 8.6 mL, indicating that the drilling fluid has excellent fracture plugging capacity and formation pressure-bearing capacity. This drilling fluid exhibits remarkable effects in lost circulation control and wellbore stabilization in drilling ultra-high temperature fractured formations. In field application of this drilling fluid in the well K2-3 (well depth 7170 m, and bottomhole temperature 199.5 ℃), “zero mud loss” was achieved in drilling the bedrock section, and no downhole complex situation caused by lost circulation or drilling fluid properties occurred throughout the whole drilling process, with a complex time efficiency of zero. The application of this drilling fluid technology significantly reduced the non-productive time due to lost circulation, providing reliable technical support for the safe and efficient drilling of ultra-deep wells in this area.
Research on Class Structural Environmentally Friendly Emulsifiers for Oil-based Drilling Fluids
CHENG Bingfang, WANG Chengjun, BU Fankang, BAO Linghan, WANG Chongchong, XIANG Peng
2026, 43(2): 188-193.   doi: 10.12358/j.issn.1001-5620.2026.02.006
Abstract(451) HTML(344) PDF (3288KB)(31)
Abstract:
Using environmentally friendly ester derivatives such as epoxy fatty acid esters as raw materials, react with polyamines to form a main emulsifier with a Gemini surfactant structure. Then, using the main emulsifier as raw material, partially sulfonate it to form a multi class environmentally friendly emulsifier with a similar structure for oil-based drilling fluids. The molecular structure of the emulsifier was determined through infrared and mass spectrometry characterization, with a temperature resistance of up to 180 ℃, a demulsification voltage of over 900 V, and an emulsification rate of over 90%. Capable of adapting to low oil-water ratio oil-based drilling fluid environments and drilling fluid systems formulated with different base oils. Adapt to drilling fluid systems with different densities. Has excellent biodegradability. A method for evaluating the microstructure of emulsion droplets was established to determine the stability of emulsion droplet formation, and it was determined that high emulsifier dosage can effectively improve the uniformity and high-temperature stability of oil in water emulsion droplets.
Development and Performance of a Water-Based Drilling Fluid Suspending Agent Resistant to 230 ℃
LIN Xin, LI Gongrang, YU Weichu
2026, 43(2): 194-201.   doi: 10.12358/j.issn.1001-5620.2026.02.007
Abstract(9) HTML(3) PDF (3797KB)(0)
Abstract:
In high-temperature and ultra-high-temperature drilling operations, the decrease in drilling fluid gel strengths causes the settling stability and the sand carrying capacity of the drilling fluid to reduce, which results in uneven dispersion of the solid particles and cuttings agglomeration in the drilling fluid. To address this problem, a quaternary polymer drilling fluid suspending agent, XFJ-3#, which exhibits temperature resistance up to 230 ℃, was designed and synthesized using AMPS (2-acrylamido-2-methylpropanesulfonic acid), SAS (sodium allylsulfonate), SSS (sodium p-styrenesulfonate) and MBA (methylene bisacrylamide) as the main raw materials. Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and 1H nuclear magnetic resonance spectroscopy (1H-NMR) were used to characterize XFJ-3#. The results show that XFJ-3# is the target product. XFJ-3# loses only 60% of its weight at 600 ℃. Performance evaluation results show that a 5% Bohai drilling clay slurry treated with 1%XFJ-3# retains more than 70% of its gel strengths after aging at 230 ℃ for 10 days. The suspending agent XFJ-3# can effectively improve the ability of a drilling fluid to maintain its settling stability for a long time under ultra-high temperature environments.
Evaluation of Sulfide Removing Rate by Basic Zinc Carbonate in Oil Based Drilling Fluids and Analyses of Sulfide Removing Mechanisms
ZHANG Zhen, YIN Da, QIN Guochuan, CHEN Lin, WANG Gui
2026, 43(2): 202-208.   doi: 10.12358/j.issn.1001-5620.2026.02.008
Abstract(8) HTML(1) PDF (2325KB)(0)
Abstract:
Basic zinc carbonate is a commonly used sulfide scavenger for drilling high-sulfide content formations with water-based drilling fluids, its ability to remove sulfide and the mechanism of sulfide removal in oil-based drilling fluids are still not well understood. In evaluating the rate if hydrogen sulfide removal, conventional methods use relatively low concentration and flow rate of hydrogen sulfide, the results of these methods are not suitable for high temperature application, and the reaction time in these methods is too short. To overcome these deficiencies of the old evaluation methods, a new experimental platform for evaluating the rate of sulfide scavenging of deep-well drilling fluids has been constructed. Using this platform, the rates of sulfide scavenging of basic zinc carbonate in oil, water, water-in-oil emulsion and oil-based drilling fluid were tested; the test results were used to analyze the existence forms of hydrogen sulfide in water-in-oil emulsions, the sulfide scavenging mechanisms of basic zinc carbonate in neutral and weakly-alkaline aqueous phases were clarified, and the sulfide scavenging mechanism of basic zinc carbonate in oil-based drilling fluids was then revealed. The test results show that the rate of sulfide scavenging of basic zinc carbonate in oil-based drilling fluids can be as high as 100%; most of the hydrogen sulfide (>90%) invading into an oil-based drilling fluid exists as undissociated hydrogen sulfide molecules in the oil phase of the oil-based drilling fluid, and only a small fraction (<10%) of the invading hydrogen sulfide dissolves into the aqueous phase to form ions dominated by HS. In the aqueous phase of an oil-based drilling fluid, the Zn2+ ions ionized from basic zinc carbonate react directly with the primary ionization product HS of hydrogen sulfide to form ZnS precipitate, and a high pH of the aqueous phase is not a necessary condition for sulfide scavenging; the reaction-diffusion coupling effect is the primary mechanism of sulfide scavenging by basic zinc carbonate in oil-based drilling fluids, and temperature increase is helpful to enhance the rate of sulfide scavenging. The revealed working mechanism of basic zinc carbonate in oil-based drilling fluids provides a scientific basis for using this chemical as a sulfide scavenger in oil-based drilling fluids.
CEMENTING FLUID
The Influence of Calcium-Based Whisker Self-Healing Agent on Self-Healing of Oil Well Set Cement Cracks in CCUS Wells
CAO Hongchang, DANG Donghong, ZHANG Ye, REN Qiang, LIU Jingli, LIU Yan, PENG Song, MA Jun
2026, 43(2): 209-216.   doi: 10.12358/j.issn.1001-5620.2026.02.009
Abstract(12) HTML(3) PDF (4570KB)(0)
Abstract:
In wells for carbon capture, utilization and storage (CCUS), cement sheaths are easy to get chemically damaged, hence reducing their service life. A study was conducted to enhance the self-healing capacity of cement sheaths by reacting calcium-based whisker self-healing agent with CO2 to produce CaCO3. The influence of calcium-based whisker self-healing agent on the self-healing process of cement sheaths was studied using mechanical tester, X-ray diffractometer (XRD), thermogravimetric analyzer (TGA), scanning electron microscope (SEM) and industrial computed tomography (CT) etc. The results of mechanical performance tests showed that after 28 days of self-healing, the self-healing rate of the compressive strength of the set cement incorporated with the calcium-based whisker reached 83.87%, which is 90.31% higher than that of the set cement without incorporating calcium-based whisker. Phase analysis and SEM observation results show that a large number of calcite-type calcium carbonate crystals were generated around the self-healing material and deposited in the cracks of the set cement, thereby rendering the cracks in the set cement carbonized self-healing. CT test results further confirmed the self-healing effect of the calcium-based whisker self-healing agent; after 28 days of self-healing, the volume of the cracks in the set cement incorporated with the calcium-based whisker self-healing agent was reduced by 4,165.95 mm3, a self-healing rate of 72.32%. This indicates that in the CCUS well environment, the incorporation of calcium-based whisker self-healing materials into a cement slurry has a positive impact on the carbonized self-healing process of the cement sheath.
Preparation of C-S-H/APC Nanoseed and Its Effect on the Early Strength of Set Cement
FU Xiongtao, DONG Zhiming, LI Jiajia, ZHOU Xingchun, MA Haiyun
2026, 43(2): 217-222.   doi: 10.12358/j.issn.1001-5620.2026.02.010
Abstract(9) HTML(3) PDF (4419KB)(0)
Abstract:
Hydrated calcium silicate/polycarboxylic acid nanocrystalline species (C-S-H/PCE) is a kind of nanocomposites with nucleation effect can accelerate the hydration reaction of cement and improve the early strength of cement stone, but the conventional anionic polycarboxylic acid dispersant has strong retarding effect. In this paper, a strongly dispersing and weakly retarding amphoteric polycarboxylic acid dispersant (APC) was firstly synthesized by introducing methacryloyloxyethyltrimethylammonium chloride cationic monomer, and then a hydrated calcium silicate/amphoteric polycarboxylic acid nanocrystalline seed (C-S-H/APC) with high early-strength performance was prepared from the APC, and the structure of the crystal seed was characterized. The compressive strength of C-S-H/APC cementite was 10.8%, 8.2% and 8.9% higher than that of C-S-H/PCE cementite when the addition amount of the crystalline seed was 1%, and the curing time at 20 ℃ was 6 h, 12 h and 24 h. The XRD patterns of C-S-H/APC cementite showed that the Ca(OH)2 diffraction peaks were obviously stronger than that of the blank group, while those of C2S and C3S were lower than that of the blank group, and there were some water-induced and water-soluble peaks in the XRD patterns of the cementite. C2S, C3S, and the diffraction peaks of hydration product AFt were lower than those of the blank group. The SEM image of cement stone shows that the hydration degree of the blank cement stone is very low and the structure is loose, and the structure of the nanometer C-S-H/APC cement stone with the same age of maintenance is denser and the hydration degree of the cement is higher, which indicates that the nanometer C-S-H/APC improves the hydration rate of the cement and accelerates the formation of the spatial network structure of the hydration products, so as to improve the early strength of the cement stone, and the performance of this low-temperature early-strengthening agent slurry system is stable, and it has been used in Changqing Oil Industry. The low-temperature early strength cement slurry performs well and has been successfully applied in the low-temperature wells in the long 6 layers of Ordos Basin of Changqing Oilfield.
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Synthesis and Evaluation of A Primary Emulsifier for High Temperature Oil Base Drilling Fluid
QIN Yong, JIANG Guancheng, DENG Zhengqiang, GE Lian
2016, 33(1): 6-10.   doi: 10.3969/j.issn.1001-5620.2016.01.002
[Abstract](5074) [PDF 4926KB](781)
摘要:
以妥尔油脂肪酸和马来酸酐为主要原料合成了一种油基钻井液抗高温主乳化剂HT-MUL,并确定了妥尔油脂肪酸单体的最佳酸值及马来酸酐单体的最优加量。对HT-MUL进行了单剂评价,结果表明HT-MUL的乳化能力良好,配制的油水比为60:40的油包水乳液的破乳电压最高可达490 V,90:10的乳液破乳电压最高可达1000 V。从抗温性、滤失性、乳化率方面对HT-MUL和国内外同类产品进行了对比,结果表明HT-MUL配制的乳液破乳电压更大、滤失量更小、乳化率更高,整体性能优于国内外同类产品。应用主乳化剂HT-MUL配制了高密度的油基钻井液,其性能评价表明体系的基本性能良好,在220℃高温热滚后、破乳电压高达800 V,滤失量低于5 mL。HT-MUL配制的油基钻井液具有良好的抗高温性和乳化稳定性。
Progress Made and Trend of Development in Studying on Temporarily Type Plugging Reservoir Protection Drilling Fluids
JIANG Guancheng, MAO Yuncai, ZHOU Baoyi, SONG Ranran
2018, 35(2): 1-16.   doi: 10.3969/j.issn.1001-5620.2018.02.001
[Abstract](3163) [PDF 4562KB](505)
摘要:
通常在勘探开发油气过程中会发生不同程度的油气层损害,导致产量下降、甚至"枪毙"油气层等,钻井液是第一个与油气层相接触的外来流体,引起的油气层损害程度往往较大。为减轻或避免钻井液导致的油气层损害、提高单井产量,国内外学者们进行了长达半个世纪以上的研究工作,先后建立了"屏蔽暂堵、精细暂堵、物理化学膜暂堵"三代暂堵型保护油气层钻井液技术,使保护油气层效果逐步提高,经济效益明显。但是,与石油工程师们追求的"超低"损害目标仍存在一定差距,特别是随着非常规、复杂、超深层、超深水等类型油气层勘探开发力度的加大,以前的保护技术难以满足要求。为此,将仿生学引入保护油气层钻井液理论中,发展了适合不同油气层渗透率大小的"超双疏、生物膜、协同增效"仿生技术,并在各大油田得到推广应用,达到了"超低"损害目标,标志着第四代暂堵型保护油气层钻井液技术的建立。对上述4代暂堵型保护油气层技术的理论基础、实施方案、室内评价、现场应用效果与优缺点等进行了论述,并通过梳理阐明了将来的研究方向与发展趋势,对现场技术人员和科技工作者具有较大指导意义。
Status Quo of Water Base Drilling Fluid Technology for Shale Gas Drilling in China and Abroad and Its Developing Trend in China
SUN Jinsheng, LIU Jingping, YAN Lili
2016, 33(5): 1-8.   doi: 10.3969/j.issn.1001-5620.2016.05.001
[Abstract](4505) [PDF 1051KB](1273)
摘要:
综述了国内外页岩气井井壁失稳机理、稳定井壁主要方法及水基钻井液技术研究与应用现状,讨论了当前中国页岩气井钻井液技术面临的主要技术难题,分析了美国页岩气井与中国主要页岩气产区井壁失稳机理的差异,指出了中国页岩气井水基钻井液技术研究存在的误区与不足,提出了中国页岩气井水基钻井液技术发展方向。
Preparation and Characteristics of Nano Polymer Microspheres Used as Plugging Agent in Drilling Fluid
WANG Weiji, QIU Zhengsong, HUANG Wei'an, ZHONG Hanyi, BAO Dan
2016, 33(1): 33-36.   doi: 10.3969/j.issn.1001-5620.2016.01.007
[Abstract](2574) [PDF 2843KB](309)
摘要:
页岩具有极低的渗透率和极小的孔喉尺寸,传统封堵剂难以在页岩表面形成有效的泥饼,只有纳米级颗粒才能封堵页岩的孔喉,阻止液相侵入地层,维持井壁稳定,保护储层。以苯乙烯(St)、甲基丙烯酸甲酯(MMA)为单体,过硫酸钾(KPS)为引发剂,采用乳液聚合法制备了纳米聚合物微球封堵剂SD-seal。通过红外光谱、透射电镜、热重分析和激光粒度分析对产物进行了表征,通过龙马溪组岩样的压力传递实验研究了其封堵性能。结果表明,SD-seal纳米粒子分散性好,形状规则(基本为球形),粒度较均匀(20 nm左右),分解温度高达402.5℃,热稳定性好,阻缓压力传递效果显著,使龙马溪组页岩岩心渗透率降低95%。
Experimental Study on Airtightness of Cement Sheath Under Alternating Stress
LIU Rengguang, ZHANG Linhai, TAO Qian, ZHOU Shiming, DING Shidong
2016, 33(4): 74-78.   doi: 10.3969/j.issn.1001-5620.2016.04.015
[Abstract](2234) [PDF 2049KB](234)
摘要:
利用自主研发的水泥环密封性实验装置研究了套管内加卸压循环作用下水泥环的密封性,根据实验结果得出了循环应力作用下水泥环密封性失效的机理。实验结果显示,在较低套管内压循环作用下,水泥环保持密封性所能承受的应力循环次数较多;在较高循环应力作用下,水泥环密封性失效时循环次数较少。表明在套管内较低压力作用下,水泥环所受的应力较低,应力水平处于弹性状态,在加卸载的循环作用下,水泥环可随之弹性变形和弹性恢复;在较高应力作用下,水泥环内部固有的微裂纹和缺陷逐渐扩展和连通,除了发生弹性变形还产生了塑性变形;随着应力循环次数的增加,塑性变形也不断地累积。循环压力卸载时,套管弹性回缩而水泥环塑性变形不可完全恢复,2者在界面处的变形不协调而引起拉应力。当拉应力超过界面处的胶结强度时出现微环隙,导致水泥环密封性失效,水泥环发生循环应力作用的低周期密封性疲劳破坏。套管内压力越大,水泥环中产生的应力水平越高,产生的塑性变形越大,每次卸载时产生的残余应变和界面处拉应力也越大,因此引起密封性失效的应力循环次数越少。
Progresses in Studying Drilling Fluid Nano Material Plugging Agents
MA Chengyun, SONG Bitao, XU Tongtai, PENG Fangfang, SONG Taotao, LIU Zuoming
2017, 34(1): 1-8.   doi: 10.3969/j.issn.1001-5620.2017.01.001
[Abstract](4777) [PDF 2528KB](879)
摘要:
分析了硬脆性泥页岩井壁失稳的原因,介绍了纳米材料特点及其应用,并概述了国内外钻井液用纳米封堵剂的研究进展,包括有机纳米封堵剂、无机纳米封堵剂、有机/无机纳米封堵剂,以及纳米封堵剂现场应用案例。笔者认为:利用无机纳米材料刚性特征以及有机聚合物可任意变形、支化成膜等特性,形成的一种核壳结构的无机/聚合物类纳米封堵剂,能够很好地分散到钻井液中,且对钻井液黏度和切力影响较小,这种类型的纳米封堵剂能够在低浓度下封堵泥页岩孔喉,建立一种疏水型且具有一定强度的泥页岩人工井壁,这不仅能够阻止钻井液侵入,而且还能提高地层承压能力,无机纳米材料与有机聚合物的结合是未来钻井液防塌剂的发展方向。
Progress in Study and Application of Waste Mud Disposal Technologies
CHEN Gang, WANG Peng, ZHAO Yi, TONG Kun, ZHANG Jie, SUN Peizhe
2020, 37(1): 1-8.   doi: 10.3969/j.issn.1001-5620.2020.01.001
[Abstract](2558) [PDF 814KB](372)
摘要:
废弃钻井液污染大、种类多、处理难,给水质和土壤环境带来巨大的负面影响,随着近些年环保法规的日益完善,对废弃钻井液的处理技术也提出了新要求。概述了9种不同处理方法及其发展现状,重点分析了固化法、热解吸法、化学强化固液分离法、不落地技术和多种技术联用等处理技术,并对几种现行的主流处理技术进行了对比,指出了各类方法的发展前景,得出多种技术联用具有较好的发展潜力。分析认为今后的研究方向与热点在于如何低能耗、高效率地实现对废弃钻井液的资源化处理,具体工作既要包含污染物的源头、过程和结果控制,也要加强管理和相关制度的建立,综合开发新技术。
Borehole Wall Collapse and Control in Shale Gas Well Drilling
LIU Jingping, SUN Jinsheng
2016, 33(3): 25-29.   doi: 10.3969/j.issn.1001-5620.2016.03.005
[Abstract](2150) [PDF 7874KB](286)
摘要:
页岩气井水平井段井壁失稳是目前中国页岩气资源勘探开发的关键技术难题。通过云南昭通108区块龙马溪组页岩的X-射线衍射分析、扫描电镜(SEM)观察、力学特性分析、润湿性、膨胀率及回收率等实验,研究了其矿物组成、微观组构特征、表面性能、膨胀和分散特性,揭示了云南昭通108区块龙马溪组页岩地层井壁水化失稳机理。该地层黏土矿物以伊利石为主要组分,不含蒙脱石及伊蒙混层,表面水化是引起页岩地层井壁失稳的主要原因。基于热力学第二定律,利用降低页岩表面自由能以抑制页岩表面水化的原理,建立了通过多碳醇吸附作用改变页岩润湿性,有效降低其表面自由能、抑制表面水化,进而显著抑制页岩水化膨胀和分散的稳定井壁方法。
Effect of Retained Fracturing Fluid on the Imbibition Oil Displacement Effciency of Tight Oil Reservoir
GUO Gang, XUE Xiaojia, LI Kai, FAN Huabo, LIU Jin, WU Jiang
2016, 33(6): 121-126.   doi: 10.3969/j.issn.1001-5620.2016.06.022
[Abstract](2308) [PDF 11047KB](262)
摘要:
统计长庆油田罗*区块2015年存地液量与油井一年累积产量的关系发现,存地液量越大,一年累积产量越高,与常规的返排率越高产量越高概念恰恰相反,可能与存地液的自发渗吸替油有关。核磁实验结果表明,渗吸替油不同于驱替作用,渗吸过程中小孔隙对采出程度贡献大,而驱替过程中大孔隙对采出程度贡献大,但从现场致密储层岩心孔隙度来看,储层驱替效果明显弱于渗吸效果。通过实验研究了影响自发渗吸效率因素,探索影响压裂液油水置换的关键影响因素,得出了最佳渗吸采出率及最大渗吸速度现场参数。结果表明,各参数对渗吸速度的影响顺序为:界面张力 > 渗透率 > 原油黏度 > 矿化度,岩心渗透率越大,渗吸采收率越大,但是增幅逐渐减小;原油黏度越小,渗吸采收率越大;渗吸液矿化度越大,渗吸采收率越大;当渗吸液中助排剂浓度在0.005%~5%,即界面张力在0.316~10.815 mN/m范围内时,浓度为0.5%(界面张力为0.869 mN/m)的渗吸液可以使渗吸采收率达到最大。静态渗吸结果表明:并不是界面张力越低,采收率越高,而是存在某一最佳界面张力,使地层中被绕流油的数量减少,渗吸采收率达到最高,为油田提高致密储层采收率提供实验指导。
Progress in the Study of Environmentally Friendly Drilling Fluid Filtration Reducer
WU Xinlei, YAN Lili, WANG Lihui, WANG Fayun
2018, 35(3): 8-16.   doi: 10.3969/j.issn.1001-5620.2018.03.002
[Abstract](2258) [PDF 851KB](315)
摘要:
解决环境污染问题是改善钻井液的关键,开发环保型抗高温降滤失剂是当前研究的重要领域之一。概述了国内外环保型降滤失剂的研究进展,对国内外在环保型降滤失剂研制中所使用的原材料及产品性能,以及中国抗温改性天然高分子降滤失剂的发展近况进行了介绍。天然高分子降滤失剂是通过对淀粉、纤维素及木质素等天然高分子材料进行改性以提高其抗温、抗盐能力,使其可以应用于井温更高的深井钻探中。目前,中国环保型降滤失剂普遍可以应用到150℃的高温中,部分抗温能力可达到180℃却未能推广使用。通过对现有降滤失剂的研究,分析其抗高温的作用机理,探寻能有效提高抗温能力的单体分子结构及发挥作用的功能基团,例如磺酸基团、内酰胺基团等,以期对环保型抗高温降滤失剂的研制起到一定的指导和参考作用,加快环保型抗高温降滤失剂的发展。
Dissolution of Barite Filter Cake Using Chelating Agents: A review of Mechanisms, Diagnosis and Removal Strategies
WEI Zhongjin, ZHOU Fengshan, XU Tongtai
2020, 37(6): 685-693.   doi: 10.3969/j.issn.1001-5620.2020.06.002
[Abstract](8976) [PDF 5710KB](1009)
Abstract:
As a weighting agent of drilling fluid, barite is easy to migrate, transform and precipitate in the reservoir to form acid insoluble barite mud cake, which causes serious damage to oil and gas reservoir. Therefore, it is necessary to remove the blockage of barite safely and reliably. However, many reasons, such as put too little emphasis on barite blocking, unclear mechanism of barite blocking and removal, improper design of removal methods, large investment but poor output, confidentiality of business, et al, have restricted the progress of remove barite blockage technology in China. The chelating agent with amino polycarboxylate as the main component is the most promising process choice for removing the barite blockage, while the chelating agent structure (amino group type, carboxyl number, ring chain size, chemical stability, et al), the properties of metal ions (charge, ion radius, ionization potential or alkalinity, co-associated metal ions, et al), medium environment (pH, temperature, pressure, et al) and so on, have a profound influence on the dissolution of barite. The economic and efficient design of chelating barite blocking remover and its removal process must take removal characteristics of different chelators, concentration, catalyst, converting agent, polymer breaker, bottom temperature, environment friendly, corrosiveness, formation rock matrix, secondary reservoir damage caused by removal process and other factors into account. With the help of modern experimental technique evaluation, such as filtrate cake dissolution, dissolution product composition and morphology, core flow, et al., and carefully design the details of chelating removal process, such as injection volume, injection pressure, soaking time, flow-back fluid treatment, et al, so as to fully understand the mechanism of barite blocking, the design of chelating removal agent and its application in oil and gas fields. In this paper, the systematic work of removing the blockage of barite filter cake is reviewed, which done by the previous researchers in recent years. Hoping to provide a new perspective for the readers, so as to improve the technical innovation level of drilling fluid and completion fluid in China.
Status Quo of Water Base Drilling Fluid Technology for Shale Gas Drilling in China and Abroad and Its Developing Trend in China
SUN Jinsheng, LIU Jingping, YAN Lili
2016, 33(5): 1-8.   doi: 10.3969/j.issn.1001-5620.2016.05.001
[Abstract](4505) [PDF 1051KB](943)
Abstract:
This paper summarizes the studies and applications of the mechanism of borehole collapse, the main methods used for stabilizing instable borehol, and the status quo of water base drilling fluid technology, discusses the major difficulties presently faced in shale gas drilling in China, analyzes the differences between the mechanisms of borehole collapse both in China and in the America, illustrates the misconceptions and deficiencies existed in the studies on water base drilling fluids for shale gas drilling in China, and points out the technical direction for the development of water base drilling fluids for shale gas drilling in China.
Progresses in Studying Drilling Fluid Nano Material Plugging Agents
MA Chengyun, SONG Bitao, XU Tongtai, PENG Fangfang, SONG Taotao, LIU Zuoming
2017, 34(1): 1-8.   doi: 10.3969/j.issn.1001-5620.2017.01.001
[Abstract](4777) [PDF 2528KB](928)
Abstract:
This paper analyzes the mechanisms under which the hard and brittle shale formations destabilize, introduces the characteristics and application of nano materials, and summarizes the progresses made in the studies of drilling fluid nano material plugging agents, including organic and inorganic nano plugging agents. Also discussed in this paper are several case histories of the application of nano plugging agents. The authors believe that plugging agents having core-shell structures, which take advantage of the rigidity of inorganic nano materials and the deformability and filming ability of organic polymers, do not heavily affect the viscosity and gel strength of the drilling fluids in which the plugging agents can well dispersed. This kind of nano plugging agents can plug the pore throats of shales at low concentrations, thereby produce a pseudo hydrophobic "borehole wall" with some strength. This pseudo "borehole wall" not only hinders the invasion of drilling fluids, it also increases the pressure bearing of formation. The authors thus believe that the combination of inorganic nano materials and organic polymers indicates the direction for the development of anti-collapse additives in the future.
Status Quo of Methods for Evaluating Filtration Performance and Mud Cake Quality of Drilling Fluid
YAO Rugang, ZHANG Zhenhua, PENG Chunyao, FENG Yanyun, DING Guangbo
2016, 33(6): 1-9.   doi: 10.3969/j.issn.1001-5620.2016.06.001
[Abstract](3528) [PDF 2116KB](795)
Abstract:
This paper discusses the instruments and procedures available presently for evaluating fltration property, sizes of pore throats, thickness and compressibility of mud cake. Analyzed in this paper are the status quo of using SEM and energy spectrum in studying the microstructure of mud cake and the distribution of mud cake constituents. Studies presently conducted were focused on the observation of surface topography, while knowledge about the interior microstructure of mud cake is still in demand when optimizing the quality of mud cake. The spatial distribution of the microstructure of mud cake needs to be extensively studied in the future to further understand the mechanism of fltration control and the way of reducing fltration rate. These studies are of help to the development and perfection of the basic theory of controlling drilling fluid fltration and ability of building mud cake, and will provide guide and technical support to the development of new high performancemud additives and to the improvement of drilling fluid technology.
Synthesis and Evaluation of A Primary Emulsifier for High Temperature Oil Base Drilling Fluid
QIN Yong, JIANG Guancheng, DENG Zhengqiang, GE Lian
2016, 33(1): 6-10.   doi: 10.3969/j.issn.1001-5620.2016.01.002
[Abstract](5074) [PDF 4926KB](1293)
Abstract:
A primary emulsifier, HT-MUL, for high temperature oil base drilling fluid was developed using tall oil fatty acids and maleic anhydride, and the optimum acid value of tall oil fatty acids and optimum concentration of maleic anhydride for the reaction were determined. Evaluation of HT-MUL shows that HT-MUL performs very well as an emulsifier. Using HT-MUL, a water-in-oil emulsion (O/W ratio=60:40) was formulated, having electrical stability of 490 V, and another water-in-oil emulsion (O/W ratio=90:10), having electrical stability of 1,000 V. Comparison of HT-MUL with other primary emulsifiers demonstrates that emulsions formulated with HT-MUL have higher electrical stability voltage, lower filter loss and higher rate of emulsion, proving that HT-MUL has better general performance than other emulsifiers. A high performance high density oil base drilling fluid was formulated using HT-MUL, retaining electrical stability of 800 V and filter loss less than 5 mL after hot rolling at 220℃. Oil base drilling fluids formulated with HT-MUL have good high temperature performance and emulsion stability.
Drilling Fluid Technology for “Three High” Wells in Qaidam Basin in Qinghai
WANG Xin, ZHANG Minli, WANG Qiang, ZHUANG Wei, ZHANG Weijun, WANG Zhibin, LI Yifeng
2016, 33(6): 45-50.   doi: 10.3969/j.issn.1001-5620.2016.06.008
[Abstract](3390) [PDF 729KB](808)
Abstract:
Four blocks in the Qaidam Basin, Niudong, Lenghu, Zahaquan and Yingxi, have formation rocks with complex lithology, such as salt, gypsum, mirabilite, and hard and brittle shales etc. Downhole troubles have been frequently encountered in previous drilling operations. The Niudong nasal structure in the piedmont of the Altun Mountain in the basin, affected by the orogenesis, has overall formation dipping angles between 60° and 70°. High formation stress, high pressure saltwater and varied coeffcients of pressure have resulted in frequent borehole wall instability in open hole section. A BH-WEI drilling fluid for the so-called "three high" (high pressure, high sulfde, and high risk area) wells, has been used in drilling 20 wells since 2013. To perform well in drilling fluid technical service, relevant data were investigated prior to drilling. Based on laboratory experiment and feld practice, it was concluded that drilling fluid with low activity, strong plugging and inhibitive capacity was benefcial to borehole wall stability. Four key exploratory wells, the frst multi-lateral horizontal well and the frst horizontal well in Zahaquan have been completed, the maximum mud density used was 2.35 g/cm3, the average percentage of hole enlargement was 4.67%, and the ratio of successful wireline logging was 100%. The well Zaping-1 is the frst horizontal well targeted with tight oil reservoir in Zahaquan. In the block Dongping, a four-interval horizontal well was drilled in 2013 with Weatherford's MEG drilling fluid. This well was not be able to drill to the designed depth because of severe mud losses and other downhole troubles. Using the BH-WEI drilling fluid, six horizontal wells were completed successfully in 2013-2014 in the same block, and no downhole trouble has been encountered throughout the drilling operations. Two horizontal wells, Ping-1H-2-1 and Ping-1H-2-2, put into production in 2014, were both high production rate wells in the same block; the average daily gas production rate was 50×104 m3/d. Field application has shown that the BH-WEI drilling fluid had simple formulation, and the mud properties were thus easy to maintain. The BH-WEI drilling fluid had good shear thinning property, high YP/PV ratio, low plastic viscosity, low pressure loss in annular space, good hole cleaning performance and good lubricity and inhibitive capacity. Using this drilling fluid, borehole collapse in drilling the dark gray Jurassic mudstone, inability to exert WOB in horizontal drilling and differential pipe sticking were avoided. To concluded, the BH-WEI drilling fluid is a unique drilling fluid suitable for use in drilling exploratory well and horizontal well in the troublesome drilling areas in Qinghai oilfeld.
A New Fracturing Fluid with Temperature Resistance of 230℃
YANG Zhenzhou, LIU Fuchen, SONG Lulu, LIN Lijun
2018, 35(1): 101-104.   doi: 10.3969/j.issn.1001-5620.2018.01.019
[Abstract](3821) [PDF 604KB](896)
Abstract:
The natural vegetable gum fracturing fluid presently in use works effectively at temperatures up to 177℃. To fracture formations with higher temperatures, a fracturing fluid with temperature resistance of 200-230℃ has been developed with ultrahigh temperature thickening agent, high temperature resistant zirconium crosslinking agent, high temperature stabilizer and efficient gel breaker through large quantity of laboratory experiments. The experimental results showed that, under the synergetic effect of these additives, the fracturing fluid is suitable for use in fracturing formations whose temperatures are higher than the temperature limit of conventional gels. The fracturing fluid has good shear-resistance property at high temperatures up to 230℃, and the polymer consumption for formulating the fracturing fluid is obviously reduced. Complete gel breaking can be realized with the fracturing fluid, and damage to the fluid conducting formations with proppants is low.
Plugging Micro-fractures to Prevent Gas-cut in Fractured Gas Reservoir Drilling
HAN Zixuan, LIN Yongxue, CHAI Long, LI Daqi
2017, 34(1): 16-22.   doi: 10.3969/j.issn.1001-5620.2017.01.003
[Abstract](3480) [PDF 2831KB](830)
Abstract:
The Ordovician carbonate rock reservoirs drilled in Tazhong area (Tarim Basin) have complex geology and developed fractures, 50% of which with widths between 20 μm and 400 μm. These fractures have led to frequent lost circulation, well kick and severe gas cut, which in turn resulted in well control risks. Complex distribution of fractures and high formation temperatures (180℃) make bridging with sized particles less effective in controlling mud losses. In laboratory experiment, commonly used testing methods for evaluating the performance of plugging drilling fluids are unable to effectively simulate the real fractures, and hence there is a big discrepancy between the laboratory evaluation and practical performanceof the plugging agents. To solve this problem, a new method has been presented based on the idea of plugging micro-fractures to prevent gas-cut. In this method, natural/artificial cores are used to make test cores with fractures of 20 μm-400 μm in width and roughness that is closely simulating the fractures encountered in the reservoirs drilled. Included in the new method are a device used to evaluate the performance of a drilling fluid in plugging micron fractures, and an evaluation procedure. With this method, particle, fiber and deformable LCMs sized in microns and nanometers were selected and an LCM formulation compatible with polymer sulfonate drilling fluid and ENVIROTHERM NT drilling fluid developed. This plugging PCM formulation, having acid solubility of greater than 70%,does not render contamination to reservoir.
Development of Extreme Pressure Anti-wear Lubricant MPA for Water Base Drilling Fluids
QU Yuanzhi, HUANG Hongjun, WANG Bo, FENG Xiaohua, SUN Siwei
2018, 35(1): 34-37.   doi: 10.3969/j.issn.1001-5620.2018.01.006
[Abstract](3397) [PDF 963KB](844)
Abstract:
An extreme pressure organic sulfur anti-wear additive has been developed for use in water base drilling fluids. Structural characteristics and extreme pressure anti-wear performance evaluation showed that the organic sulfur compound is a saturated alkane, with sulfur content as high as 35.49%, and has good extreme pressure anti-wear property. An extreme pressure anti-wear additive, MPA, was developed with a modified vegetable oil as the base oil, the extreme pressure organic sulfur anti-wear additive and surfactants. The components of MPA are all environmentally friendly. Performance evaluation showed that MPA has good compatibility with other additives, and is completely dispersible in fresh water or drilling fluids. It helps optimize the properties of drilling fluids and has excellent lubricity.
Progress in Studying Cement Sheath Failure in Perforated Wells
LI Jin, GONG Ning, LI Zaoyuan, HAN Yaotu, YUAN Weiwei
2016, 33(6): 10-16.   doi: 10.3969/j.issn.1001-5620.2016.06.002
[Abstract](3493) [PDF 2703KB](844)
Abstract:
Perforation well completion is a widely used completion method, and is of great importance to oil and gas well stimulation. With more and more wells completed with perforation, more attentions have been paid to the sealing integrity of cement sheaths after perforation, especially the perforation of wells with thin pay zones. Research work presently done has been focused on the effects of perforation on casing strings, while little attention has been paid to the damage of cement sheath. Oil and gas well perforation has characteristics such as being powerful, short time, high temperature, and being highly destructive. It is pointed out in this paper, based on analysis, that the diffculties in studying the failure of cement sheath mainly lie in laboratory simulation, determination of the degree of damage to the cement sheath, determination of the cement sheath's resistance to impact under practical conditions, and ascertaining the effects of perforation parameters on the integrity of cement sheath, etc. Researches presently done on the topics such as perforation simulation methods used both in China and abroad, integrity of cement sheath after perforation, shock or impact resistance of cement sheath, and the effects of perforation parameters, are summarized in this paper. Defciencies of the researches are also discussed herein. Also included in this paper are technical measures concerning self-healing cement, cement slurry and set cement performance designs, optimization of perforation parameters, and prediction of dynamic damage to downhole cement sheath etc.
Governed by:
China National Petroleum Corporation Ltd
Sponsored by:
CNPC Bohai Drilling Engineering Co. Ltd
Editor-in-Chief:Shi-chun Chen(Engineer Technology Research Institute,BHDC)
Deputy Editor-in-chief:
Gui-juan Wang(Engineer Technology Research Institute,BHDC)Qiang Ren(Engineer Technology Research Institute,BHDC)
Address:
Room A517, China Petroleum Tianjin Building, No. 83, Second Avenue, Tianjin Economic and Technological Development Zone
Postcode: 300457
Tel:022-65278734
022-25275527
E-mail: zjyywjy@126.com
   CN   12-1486/TE
ISSN   1001-5620