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2021, 38(3).  
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Molecular Simulation of the Hydration of Montmorillonite under High-temperature and Highpressure
LI Lizong, SU Junlin, ZHAO Yang, ZUO Fuyin
2021, 37(3): 265-270.   doi: 10.3969/j.issn.1001-5620.2021.03.001
Abstract(0) PDF (2167KB)(0)
The hydration expansion of clay minerals in shale is an important factor affecting the sidewall stability of shale gas well. The montmorillonite is the main constituent of clay minerals, and its hydration mechanism is very important to solve the problem of borehole wall instability in shale gas well. In order to further explore the hydration mechanism of the montmorillonite under high temperature and high pressure, molecular simulation software was used to study the inter-layer spacing, inter-layer material movement, ionic hydration properties and mechanical parameters of the montmorillonite under different temperature and pressure conditions from a microscopic perspective. The results show that when the temperature increases and the pressure decreases, the inter-layer spacing of montmorillonite augments, and relatively the temperature has a great influence on the inter-layer spacing, which ranges from 1.823-2.042 nm. The diffusion rate of inter-layer water molecules and sodium ions increases with the increase of temperature and decreases with the increase of pressure. The hydration coordination number of sodium ion is large at low temperature and high pressure, and the coordination number varies from 2.35 to 4.35. When the temperature goes up, the volume modulus, shear modulus and elastic modulus of montmorillonite crystal goes down and poisson's ratio increases, while the effect of pressure on the mechanical parameters of montmorillonite crystal is the opposite. It can be seen that the research results of this paper have important theoretical guiding significance for the research of shale formation hydration mechanism under high temperature and high pressure formation environment.
Study of Rheological Dynamics of Water-Based Drilling Fluids at High Temperature and High Pressure
HE Miao, SHI Haohan, XU Mingbiao
2021, 37(3): 271-279.   doi: 10.3969/j.issn.1001-5620.2021.03.002
Abstract(0) PDF (2745KB)(0)
In order to ensure the safety of drilling process, it is necessary to have a more profound understanding of the rheological properties of drilling fluid under high temperature and high pressure (HTHP). Polysulfide drilling fluid has excellent performance and is widely used. Experimental research on the rheological properties of drilling fluid under HTHP still needs to be strengthened. Under wide range of temperature and pressure(-180℃, -100 MPa), the rheological properties of the selected water-based drilling fluid were evaluated, and the rheological parameters were quantitatively evaluated and analyzed. The experimental data show that the rheological property of Polysulfide drilling fluid is less affected by pressure than by temperature. By fitting the commonly used rheological models (Bingham model, Power Law model, Casson model, Herschel-Bulkely model and Robertson-Stiff model) in drilling field, the fitting effect of each model is analyzed, and the best rheological model for describing the rheological behavior of the drilling fluid is found out. The results show that both The H-B model and the R-S model can describe the rheological behavior of the drilling fluid under HTHP, and the fitting effect of the H-B model is slightly better than that of the R-S model. The order of the fitting effect of each mode is as follows:Herschel-Bulkely ≈ Robertson-Stiff ≈ Bingham > Casson > Power Law. Based on the H-B model, the optimal fitting equation of rheological parameters with temperature and pressure was obtained from the nine combinations of (T,P), (T,1/P), (T,lnP), (1/T,1/P), (1/T,lnP), (lnT,P), (lnT,1/P) and (lnT,lnP) by direct fitting method and finally the prediction formula of shear stress of polysulfide drilling fluid was obtained. The prediction accuracy of the formula was good, and the relative error rate was mostly concentrated between -7.15%-11.46%, The average error was only 1.03%.
Equipment and Methods of Measuring High Temperature Rheology of Drilling Fluids
LIU Xiaodong, LIU Tao
2021, 37(3): 280-284.   doi: 10.3969/j.issn.1001-5620.2021.03.003
Abstract(0) PDF (1372KB)(0)
Since the six-speed direct reading viscometer is unable to measure the change of mud rheology with downhole temperature, downhole pressure, downhole shear rate and time, drilling fluid researchers turn to the high temperature high pressure (HTHP) rheometer for evaluating the rheology and thermal stability of drilling fluids, hoping that it will give more scientific and effective test results. To simulate the actual mud properties downhole, several test methods are established, which are test of low shear rate viscosity, test of loss of viscosity at high temperatures and test of changes of mud viscosity with time at dynamic and static conditions. These tests are used to characterize the cuttings carrying capacity, rheology at elevated temperatures and high temperature stability of drilling fluids at dynamic and static conditions, the test results can reveal the actual rheology of the drilling fluids downhole. Field application of the HTHP rheometer in testing the properties of the organic salt drilling fluid used in drilling the well Chengtan-1 indicated that the test method can be used to provide field engineers with accurate data for judging whether the mud properties can meet the requirements of drilling operation under high bottomhole temperatures. The test method and the HTHP rheometer have provided a scientific and reliable way of designing, developing and using high temperature drilling fluids and mud additives, and greatly made up for the shortcomings and defects of using the six-speed viscometer to measure the rheology of drilling fluids.
A high-temperature and High-Density Environmentally-Friendly Water-Based Drilling Fluids Based on Modified Plant Polyphenols
LIU Ziguang, SONG Fengbo, YOU Zhiliang, ZHUO Lyuyan, PENG Yuntao, XIANG Chunfen, JIANG Guancheng
2021, 37(3): 285-291.   doi: 10.3969/j.issn.1001-5620.2021.03.004
Abstract(0) PDF (885KB)(0)
To improve the high-temperature resistance and density upper limit of environmentally friendly water-based drilling fluids, the fluid-loss reducer EHT-FL and the thinner EHT-TH were developed by modifying plant extracts of natural polyphenol. Two synthesized products were characterized by infrared spectroscopy. In laboratory experiments, the fluid-loss reducer EHT-FL and the thinner EHT-TH exhibited good high-temperature resistance. And the EC50 reached 2.38×105 mg/L and 4.49×105 mg/L, respectively, with no biological toxicity. The medium-pressure and high-temperature/high-pressure fluid-loss of freshwater-based mud with 2.0% EHT-FL are only 7.2 mL and 23.6 mL after aging at 200℃. When the dosage of EHT-TH is 1.0%, the apparent viscosity of high-density water-based drilling fluid (ρ=2.0 g/cm3) after aging at 200℃ decreases from 106.5 mPa·s to 66.5 mPa·s, and the high-temperature thickening phenomenon disappears. Based on the excellent temperature-resistance of EHT-FL and EHT-TH, a high-temperature and high-density (ρ=2.0 g/cm3) environmentally friendly water-based drilling fluid has been developed. This drilling fluid has reasonable rheological and fluid-loss properties. It has high-temperature resistance of 210℃ and resistance to 25% salt contamination, 1% calcium contamination, and 10% inferior soil contamination. EC50 of this drilling fluid is 4.19×104 mg/L, BOD5/CODCr is 29.23, heavy metal content is lower than the standard value, non-toxic, biodegradable. Therefore, this environmentally friendly drilling fluid can meet the drilling needs of deep-wells complex formations.
Ultra-High Temperature Drilling Fluid Technology for Drilling Well Jiantan-1
HAO Shaojun, AN Xiaoxu, WEI Xihai, ZHANG Chuang, LI Baoqing, LEI Biao
2021, 37(3): 292-297.   doi: 10.3969/j.issn.1001-5620.2021.03.005
Abstract(0) PDF (769KB)(0)
The well Jiantan-1 is a key exploratory well of PetroChina located in the Jianshan structure of the central rhinoplasty belt in the Chaidamu Basin. The main purpose of this 6343 m well is to explore the gas reserves in the base rocks of the Jianshan structure. The highest bottom hole temperature measured is 235℃, one of the highest bottom hole temperatures encountered in onshore drilling. The formations drilled in this area have fractures that are fully developed, long sections of gypsum and mudstones, high pressure saltwater zones, high CO2 concentrations and high geothermal gradient. Borehole wall collapse, mud losses, overflow, creeping and tight hole in the gypsum/mudstone formations are downhole troubles encountered and sometime intertwined with each other during drilling. To deal with these problems, laboratory study was conducted on several aspects of the drilling fluid used, which are high temperature stability, rheology and high temperature filtration control. An organic salt drilling fluid was formulated with additives specially selected, such as ultra-high-temperature filter loss reducers, anti-collapse additives with plugging capacity, lubricants and thermal stabilizers etc. This drilling fluid is able to resist high temperatures up to 240℃. After aging for 72 hours, the HTHP filtration rate was maintained with 10 mL, the coefficient of friction was less than 0.1, and the invasion depth on a sand-bed less than 12 cm. In addition, the fourth and fifth intervals of the well penetrated formations with micro-fissures and a basal rock weathered crust, and mud losses occurred many times into the fissures. A lost circulation material slurry for the well Jiantan-1 was then developed with choice rigid, flexible and gel-like plugging additives which are suitable for use at elevated temperatures. Using this mud loss control slurry, the pressure bearing capacity of the formations into which mud losses have occurred was finally enhanced. The organic salt drilling fluid and the mud loss control slurry played a major role in preventing and controlling borehole wall collapse and mud losses, ensuring the success of the drilling of the first ultra-high temperature Jiantan-1 well in Chaidamu Basin.
Study on a Lyophobic Nanophase Plugging Agent for Oil Base Muds
NI Xiaoxiao, JIANG Guancheng, WANG Jianhua, YAN Lili, LIU Rentong
2021, 37(3): 298-304.   doi: 10.3969/j.issn.1001-5620.2021.03.006
Abstract(0) PDF (13890KB)(0)
Physical plugging with nanophase materials and wettability alteration of rock surface were used to solve the borehole wall stability problem encountered in shale gas drilling with oil base muds. The surface of the nanophase silica was modified sol-gel method, turning the silica into a lyophobic nanophase plugging agent, SNP-1. Molecule structure characterization with NMR and laboratory evaluation with SEM and natural imbibition revealed that SNP-1 gains the functional groups it was expected to have. With SNP-1, the contact angle of liquid on the surface of shale is greater than 150° and the additional capillary pressure is reversed to a force resisting the liquid phase from entering the pore throats of shales, further reducing the oil content of rocks through natural imbibition. The HTHP filtration rate and electrical stability of the oil base mud treated with SNP-1, after being aged at 150℃, were 2.4 mL and above 800 V, respectively, effectively hindering the pressure transmission through shale cores.
Applicability of Methods for Evaluating Temperature Resistance of Foaming Agents Used in Foam Drilling Fluids
YANG Qianyun, WANG Baotian, YANG Hua
2021, 37(3): 305-310.   doi: 10.3969/j.issn.1001-5620.2021.03.007
Abstract(0) PDF (2205KB)(0)
The applicability of several methods used to evaluate the high temperature stability of foaming agents was studied in an effort to find the most applicable method for selecting the best foaming agent used to formulate high temperature foam drilling fluids. Three industrial high temperature foaming agents, sodium dodecyl benzene sulfonate (SDBS), sodium dodecyl sulfate (SDS) and sodium α-olefin sulfonate (AOS) were tested and compared using hot rolling method and dry powder heating method, both of which are based on mechanical mixing. Investigation of the effects of temperature on the foaming property of these foaming agents and the stability and rheology of the foaming fluids showed that the same foaming agent evaluated with different methods gives different results. Using the hot rolling method to test at 0-190℃, the performance of SDS is better than that of AOS and SDBS; on the other hand, SDS cannot perform properly at temperatures above 200℃, while AOS and SDBS, after hot rolling at 240℃ for 16 hours, still had good foaming performance. Evaluating the performance of the three foaming agents with dry powder heating method showed that AOS and SDBS, after heating at 260℃ for 4 hours, still foamed, while SDS can only last for 3 hours at 150℃. Based on the evaluation and other tests, it is recommended that hot rolling test method be used to evaluate the performance of foaming agents; with this method, the effects of temperature on the performance of foaming agents can be understood and suggestion can be given to the formulation of foaming fluids used for drilling at different temperatures.
Drilling Fluid Technology for Shale Oil Exploration and Development in Daqing Oilfield
YU Kun, CHE Jian
2021, 37(3): 311-316.   doi: 10.3969/j.issn.1001-5620.2021.03.008
Abstract(0) PDF (2575KB)(0)
In this paper the geological characteristics, operation difficulties and mechanisms of borehole wall collapse of the Gulong block in Daqing Oilfield are summarized and analyzed in an effort to solve the borehole wall instability problem encountered in shale oil horizontal drilling in the Qijia-Gulong block. Different measures have been presented to solve different problems encountered for the use of oil base muds, such as borehole wall stabilization, mud rheology control and hole cleaning. Key plugging agents such as SFD-1, non-fluorescent anti-collapse agent BY and Soltex were selected for use in the oil base (water-in-oil) drilling fluid that was used in the past and was now optimized. Laboratory evaluation tests showed that the optimized oil base mud has HTHP filter loss of less than 3 mL and is resistant to the contamination from 30% drilled cuttings. Filed application of this mud on the well **2HC in the Gulong block was successful and no downhole troubles have ever happened during drilling. The optimized oil base drilling fluid can be used to solve borehole wall collapse problem encountered in long horizontal drilling, and will have broader prospects of application in shale oil exploration and development in Daqing Oilfield.
Preparation and Performance Study of an Octaamino Star-Shaped Low Molecular Weight Polymer Inhibitor
LIU Fengbao, ZHANG Shuncong, YAN Zhihang, LUO Xiao, DONG Yinghua, SUN Aisheng
2021, 37(3): 317-323.   doi: 10.3969/j.issn.1001-5620.2021.03.009
Abstract(0) PDF (2621KB)(0)
The hyperbranched low molecular weight polyamine inhibitors presently in use have some deficiencies such as low density of primary amino groups and lack of inhibitive capacity in high pH environment. To overcome these deficiencies, an octaamino star-shaped low molecular weight polymer (OASS) with regular molecular structure and high density of amino groups was developed through twostep reaction with pentaerythritol as the raw material. Molecular simulation of OASS showed that the adsorption density of OASS on the surfaces of clays is almost the same as that of pentaerythrityltetramine (PTTA) and 3,3-bis(2-aminoethyl)-1,5-pentanediamine (BAPD), but the adsorption energy of a single molecule layer of OASS is significantly greater than that of PTTA and BAPD, indicating that the adsorption centers of the three polyamines on the clay surfaces are all provided by the amino groups, and OASS which has the highest amino group density has the highest adsorption capacity. Test on the adsorption capacity of OASS showed that at 25℃, the saturated adsorption capacity of OASS is only 1.12 mmol/L, and the molar concentration of OASS at saturated adsorption capacity I sonly 10 mmol/L. Laboratory experiment on the capacity of OASS in inhibiting clay yield and linear expansion, and in percent recovery of drilled cuttings in hot roller test showed that OASS is remarkably superior to PTTA and BAPD in inhibiting the yield of shale cuttings. Laboratory experiment also showed that OASS is compatible with filed drilling fluids and does not affect the rheology of the drilling fluids before and after aging. OSAA also helped improve the filtration control property of the drilling fluids. The results of the study have prove d that OASS has excellent inhibitive capacity and is well compatible with different drilling fluids.
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](426) [PDF 1051KB](865)
High Performance Water Base Drilling Fluid for Shale Gas Drilling
LONG Daqing, FAN Xiangsheng, WANG Kun, FAN Jianguo, LUO Renwen
2016, 33(1): 17-21.   doi: 10.3969/j.issn.1001-5620.2016.01.004
[Abstract](531) [PDF 540KB](262)
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](664) [PDF 4926KB](447)
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。
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](374) [PDF 2843KB](217)
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](191) [PDF 2049KB](152)
Temporary Plugging Diverting Test with Fuzzy Ball Fluids in Non-Water Producing Coal Beds in Re-fracturing Well Zheng-X
ZHENG Lihui, CUI Jinbang, NIE Shuaishuai, LIU Bin, FU Yuwei, LI Zongyuan
2016, 33(5): 103-108.   doi: 10.3969/j.issn.1001-5620.2016.05.022
[Abstract](389) [PDF 1759KB](483)

郑庄煤层气田郑X井欲实施绒囊暂堵流体重复压裂转向,既形成新裂缝又不影响原缝生产,增加供气体积以达到满意产量。室内先用绒囊流体暂堵直径38 mm煤岩柱塞的中间人工剖缝,后用活性水测试绒囊流体暂堵剖缝承压能力达20 MPa,超过地层18 MPa的破裂压力,满足转向要求;绒囊暂堵流体伤害郑庄煤岩柱塞渗透率恢复值85%,满足原缝继续生产要求;现场利用混砂车和水罐建立循环,通过剪切漏斗配制密度为0.94~0.98 g/cm3、表观黏度为30~34 mPa·s的绒囊暂堵流体。先用活性水顶替检测原缝是否存在后,用排量为3.0~3.5 m3/h注入绒囊暂堵流体60 m3,停泵30 min油压稳定在12 MPa,表明绒囊封堵原缝成功。用活性水压裂液压裂,油管压力上升至18 MPa时出现破裂。微地震监测新缝方位为N13°W,相对于原缝N42°E转向55°。压后间抽2 h产气200 m3,是压裂前产量的2倍以上。采用微地震监测和对比压裂前后产量证明,绒囊可迫使压裂液转向压开新缝,且不伤害原裂缝,适用于煤层气老井重复压裂恢复生产。

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](451) [PDF 2528KB](542)
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](231) [PDF 11047KB](189)
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。
Cement Slurry Treated with Latex Nano Liquid Silica Anti-gas-migration Agent
GAO Yuan, SANG Laiyu, YANG Guangguo, CHANG Lianyu, WEI Haoguang
2016, 33(3): 67-72.   doi: 10.3969/j.issn.1001-5620.2016.03.014
[Abstract](379) [PDF 6834KB](210)
针对顺南区块超深高温高压气井固井面临井底温度高、气层活跃难压稳的问题,研究了胶乳纳米液硅高温防气窜水泥体系。通过将纳米液硅防气窜剂与胶乳防气窜剂复配使用,协同增强水泥浆防气窜性能;不同粒径硅粉复配与加量优化,增强水泥石高温稳定性;无机纤维桥联阻裂堵漏,抑制裂缝延展,提高水泥浆防漏性能和水泥石抗冲击性能。该水泥浆体系具有流动性好、API失水量小于50 mL、直角稠化、SPN值小于1,水泥石具有高温强度稳定性好、胶结强度高、抗冲击能力强的特点。密度为1.92 g/cm3的水泥浆体系在190℃、21 MPa养护30 h后超声波强度逐渐平稳,一界面胶结强度达12.6 MPa;水泥石弹性模量较常规低失水水泥石降低52%,抗冲击强度增加了188%,且受霍普金森杆冲击后仅纵向出现几条未贯穿的裂纹。该高温防气窜水泥浆体系在顺南5-2井和顺南6井成功应用,较好地解决了顺南区块超深气井固井难题。
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](191) [PDF 4562KB](369)
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](426) [PDF 1051KB](4)
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.
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](270) [PDF 2116KB](4)
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.
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](216) [PDF 729KB](2)
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.
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](374) [PDF 2831KB](4)
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.
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](322) [PDF 2703KB](3)
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.
A Temperature Sensitive Expanding Microcapsule Anti-Gas-Channeling Cement Slurry
ZHANG Xingguo, YU Xuewei, GUO Xiaoyang, YANG Jixiang, YAN Rui, LI Zaoyuan
2018, 35(1): 71-76.   doi: 10.3969/j.issn.1001-5620.2018.01.014
[Abstract](97) [PDF 4092KB](2)
A temperature sensitive expanding microcapsule anti-gas-channeling agent has been synthesized with acrylonitrile (AN), methylmethacrylate (MMA) and methyl acrylate (MA) as the wall material, and iso-butane as the core material. The effects of the amount of iso-butane used in the synthesis on the performance of the anti-gas-channeling were studied, and the performance of the temperature sensitive expanding microcapsule anti-gas-channeling cement slurry in controlling gas channeling was evaluated. The studies and the evaluation results showed that the temperature sensitive expanding microcapsule anti-gas-channeling agent can be obtained under the following conditions:in 100 g of deionized water add AN, MMA and MA in a ratio of 3:0.4:2, 30% iso-butane, 1% lauroyl peroxide (LPO, as initiator), 0.1% 1, 4-butanediol dimethacrylate (BDDMA, as crosslinking agent), 20% nano silicon dioxide (as dispersant), and react these substances at 65℃ with the protection of nitrogen. The anti-gas-channeling agent has initial expansion temperature of 65℃, optimal expansion temperature of 83℃, and is resistant to temperature as high as 120℃. Rate of expansion of the anti-gas-channeling agent is 50. Stimulation of water-channeling/gas-channeling in oil well cement and test of cement slurry condensation and contraction indicated that volumetric contraction of cement slurry can be made up for with less than 2% of the synthesized anti-gas-channeling agent, meaning that this anti-gas-channeling agent has good gas-channeling prevention ability.
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](451) [PDF 2528KB](5)
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.
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](137) [PDF 604KB](9)
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.
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](141) [PDF 963KB](4)
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 on Drilling Fluid Technology for Hot Dry Rock Drilling
2018, 35(4): 7-13.   doi: 10.3969/j.issn.1001-5620.2018.04.002
[Abstract](146) [PDF 535KB](4)
Two key issues encountered in hot dry rock drilling are high temperature and lost circulation. This paper introduces the analyses made on the geological characteristics of hot dry rock and the drilling fluid technology required for drilling the hot dry rock, and surveying performed on drilling fluid system for hot dry rock drilling and the field applications of the drilling fluids. New technologies for hot dry rock drilling found both in China and abroad suitable for different formation conditions are summarized. Problems found of the hot dry rock drilling fluid are also presented with the prospecting for the development of the technology. Presently, polymer sulfonate water base drilling fluid is mainly used for hot dry rock drilling, however, some other drilling fluids, such as high temperature foam mud, aerated drilling fluid, liquefied nitrogen fluid etc. are also prospective fluids for hot dry rock drilling. These new hot dry rock drilling fluids have been successfully applied in field operation with good results; they impose low formation damage, and are high temperature and salt resistant. Other advantages include good adaptability to different formation conditions and performance in environment protection, all of which represent the future of the development of the hot dry drilling fluid technology.
Competent Authorities:China National Petroleum Corporation Ltd
Sponsored by:CNPC Bohai Drilling Engineering Co. LtdPetroChina Huabei Oilfield Company
Editor-in-Chief:Shi-chun Chen
Address: Editorial Department of Drilling Fluid and Completion Fluid, Bohai Drilling Engineering Institute, Yanshan South Road, Renqiu City, Hebei Province
Postcode: 062552
Tel:(0317)2725487 2722354