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Optimization of Hydrate Inhibition Performance of Deep Water Shallow Drilling Fluid
REN Guanlong, MENG Wenbo, HE Yufa, HUANG Liang, WANG Jintang
2022, 39(5): 529-537.   doi: 10.12358/j.issn.1001-5620.2022.05.001
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The deep water and shallow geological conditions are complex, the soil is loose, the operating pressure window is narrow, the submarine mud line temperature is low, and hydrates are easy to form in the well bore. The drilling fluid is faced with problems such as well bore stability, difficulty in regulating low-temperature rheology, environmental pollution and so on, so the drilling safety operation risk is high. Therefore, taking the shallow drilling of a deep water well in the South China Sea as the research object, the application status of deep-water shallow drilling fluid are summarized and analyzed, the ECD calculation model and well bore temperature field calculation model is established, and the well bore temperature field distribution and hydrate formation risk during deep-water shallow drilling is analyzed. The hydrate inhibition performance of shallow drilling fluid system is optimized in combination with numerical simulation and indoor experiments. The following research results are obtained. First, compared with the measured data, the average error of ECD calculation model and well bore temperature field calculation model for deep-water shallow drilling is less than 8%; Second, it is calculated that the range of hydrate formation area in the well bore gradually decreases with the increase of drilling depth, but there is still a risk of hydrate formation in the well bore during drilling preparation and early drilling; Third, the conventional semi preventive drilling fluid system is optimized as HEM+14%NaCl+6%KCl, which can meet the operation requirements during normal drilling. It is concluded that through the optimization of deep water shallow drilling fluid system, the addition of hydrate inhibitor can be reduced, the drilling fluid formula can be simplified, the drilling cost can be reduced, and the operation efficiency can be improved, which can provide guidance for the drilling fluid design of deep water oil and gas drilling.
Development and Performance Evaluation of High Temperature Salt Resistant Drilling Lubricant
WANG Zonglun, SUN Jinsheng, LIU Jingping, LYU Kaihe, SHAO Zihua, ZHANG Xianfa
2022, 39(5): 538-544.   doi: 10.12358/j.issn.1001-5620.2022.05.002
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Using boric acid, polyols and long-chain fatty acids, a high temperature salt resistant drilling lubricant SOB has been developed to deal with high torque high friction encountered in deep and ultra-deep well drilling. SOB has good lubricity at high temperatures and high salinities. A 5% base mud treated with 1% SOB has its friction coefficient reduced by 92.7%, and the adhesion coefficient of the mud cake produced by that mud is reduced to 0.0405, meaning that SOB has a sustainable lubricity under extreme pressure condition. Percent reduction of friction coefficient at 210 ℃ is generally 90.2%, percent reduction of friction coefficient of a mud containing 35%NaCl at 210 ℃ is generally 81.3%. At high temperature and high salinity conditions, SOB has good compatibility with other components of a high density drilling fluid. After aging at 200 ℃, the rheology of the drilling fluid was not affected, the mud filtration rate can be reduced, and the coefficient of friction of the mud was reduced by 45.09%, meaning that SOB has better lubricity than conventional drilling lubricants. The reason for this phenomenon is that SOB can be effectively adsorbed on the surfaces of the drill strings, forming a layer of film with strong hydrophobicity. The existence of this film changes the direct contact between the drill strings and the borehole wall to a contact between two films of the lubricant, thereby effectively reducing the friction therebetween.
Characteristic Study of Thermosensitive Shape Memory Lost Circulation Materials
FENG Jie, ZANG Xiaoyu, QIU Zhengsong, BAO Dan, ZHENG Lihui
2022, 39(5): 545-549.   doi: 10.12358/j.issn.1001-5620.2022.05.003
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In order to improve the self-adaptability and plugging efficiency of bridging materials and increase the success rate of plugging fractured formation, this paper develops a kind of thermosensitive shape memory lost circulation materials. By crushing and granulating, shape memory particles with different sizes were obtained. Evaluation experiments show that the mechanical properties and shape memory performance of thermosensitive shape memory lost circulation materials are preferable, and the particle size growth rate under high temperature activation is more than 55%. The simulation experiments of fracture plugging show that the temperature has a significant influence on the plugging effect, and the plugging effect of thermosensitive shape memory lost circulation materials is better than that of traditional bridging materials under high temperature. Building a set of formula of plugging fluid with strong self-adaptability, it can successfully plug 3-5 mm coexisting fractures, achieving adaptive and high-efficiency plugging.
Development of Paraffin Microemulsion and Its Application in Water-Based Drilling Fluids
SONG Hanxuan, YE Yan, ZHOU Zhishi, ZHANG Hanyu, ZHANG Qingwen, ZHOU Fujian, GUO Jixiang
2022, 39(5): 550-557.   doi: 10.12358/j.issn.1001-5620.2022.05.004
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Analyses of seepage losses through micron and nanometer fractures and pores encountered in ultra-deep drilling in the southwest Tarim Basin show that the plugging agents in the potassium based polymer sulfonate drilling fluid are unable to effectively plug these fractures and pores. To improve the particle sizing for better plugging, a paraffin microemulsion was developed in laboratory. The optimum conditions for the development of the microemulsion was determined through particle size comparison method. It was found through experiment that the optimum quantity ratio of “S+A” : paraffin is 9:1, the optimum agitation speed is 1400 r/min, and the optimum reaction temperature is 120 ℃. The microemulsion thus prepared has D50 particle size of about 2.9 μm, monodisperse particle sizes between 200 nm and 300 nm, surface tension between 45.0 mN/m and 47.5 mN/m, and stable time up to 30 d. The potassium based polymer sulfonate drilling fluid was then optimized with the microemulsion, and good compatibility between them was seen after mixing. The optimized drilling fluid has its apparent viscosity reduced by 3.5 mPa·s, filtration rate reduced by 3.5 mL, thickness of mud cake reduced by 1 mm, and the filtration and wall building performance of the drilling fluid was enhanced. Evaluation of the plugging capacity of the paraffin microemulsion by pressure transmission methos shows that the paraffin microemulsion can be used to improve the pressure bearing capacity of the formation; test of the paraffin microemulsion on plugging the Keziluoyi dense sandstone shows that 58.4% of the microfractures and pores were plugged, indicating that the paraffin microemulsion has good plugging capacity
A Synthetic Based Drilling Fluid with Strong Plugging Capacity for Block Wushi17-2
MA Lei, YUAN Xueqiang, ZHANG Wandong, CAO Feng, DENG Wenbiao, ZHANG Xuefei, YANG Lili
2022, 39(5): 558-564.   doi: 10.12358/j.issn.1001-5620.2022.05.005
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The block Wushi17-2 is an important part of the Nanhai West Oilfield and has significant exploration and development prospects. However, there are severe potential downhole problems encountered during drilling operations, such as borehole wall instability, mud losses and formation damage, has imposed serious challenges to the properties of drilling fluids. Since this block is located nearby a national nature reserve, the environmental friendly performance of drilling fluids remains a great challenging. To deal with these problems, this study proposes the research idea of formulating high performance synthetic based drilling fluid with gas-to-liquid (GTL), followed by optimizing with a primary emulsifier, a secondary emulsifier and a high efficiency plugging agent OSD-2, eventually formulating a synthetic based drilling fluid with a density of 1.5 g/cm3, a temperature resistance of 150 ℃, a high temperature high pressure filtration rate of less than 5 mL and an electric stability of greater than 400 V. The synthetic based drilling fluid has excellent rheology, lubricity, inhibitive capacity and resistance to clay contamination (resistant to contamination of 10% poor-quality clay). The synthetic based drilling fluid satisfied the demands of field operation and helped to solve drilling fluid-related problems during drilling process.
Development and Application of a Protective Agent for Tight Oil and Gas Reservoirs
LI Xintong, ZHENG Wenwu, LIU Fu, SUN Zhongwei, WANG Song
2022, 39(5): 565-572.   doi: 10.12358/j.issn.1001-5620.2022.05.006
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In developing the Benbutu oilfield in Xinjiang, hole size irregularities were often encountered in the water- and hydrocarbon-containing sections, and these greatly affect the quality of the cementing job and damage the reservoirs. To protect the oil and gas reservoirs in the Benbutu oilfield, an elastic polymer microsphere NWL was developed through soap-free emulsion polymerization and was characterized. A reservoir protective agent CBJ was formulated with NWL, a selected anti water-block agent, a kind of rigid acid soluble nanometer particles (CaCO3) and a petroleum resin in a certain quantity ratio. Laboratory experiment was conducted to evaluate CBL in the aspects such as: the compatibility of CBL with the sizes of formation fractures, the acid solubility and oil solubility of CBL, the compatibility of CBL with the drilling fluids presently used, and the reservoir protection performance of CBL. CBL was also tested in field operations. CBL has the particle size distribution that is suitable for plugging formation fractures, good acid solubility and oil solubility. Drilling fluids treated with CBL have filtration rate reduced by about 20%, and percent permeability recovery by more than 80%. Field application and laboratory study show that CBL has good reservoir protection effect, it can be used to protect the reservoirs of Benbutu oilfield in accordance with the local conditions and maximize the production of oil wells.
Borehole Wall Strengthening with Micron and Nano Materials in “Dabadong” Area of Changning
SHE Chaoyi, LI Bo, DAI Feng, XIAO Xinyu, WEN Qianbin
2022, 39(5): 573-578.   doi: 10.12358/j.issn.1001-5620.2022.05.007
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The Longmaxi formation in Changning is highly developed with microfractures because of the tectonic action in the “Dabadong” area and the formation rock components. The sizes of the primary pores are distributed in a range of 0.05-2 μm. The formation stability is very poor and overpull and resistance have been frequently encountered during drilling. Increase in mud weight only cannot control wellbore instability. The drilling fluids presently in use only contain micron-sized plugging agents and are unable to effectively plug the nanometer pores. The lack of nanometer plugging agents cannot help form low permeability plugging layers to hinder the transmission of borehole pressure into the formations. By introducing a nanometer graphene plugging agent, the drilling fluid has both micron-sized and nano-sized plugging agents. Furthermore, the mud weight was determined through geomechanics model. With all these technologies and mud property control, the borehole wall was strengthened. Application of the borehole wall strengthening technology in the well Ning-209H69 showed that the properties of the drilling fluid were stable, no downhole troubles were encountered in the whole drilling process, the average percent hole enlargement was less than 8%, and the borehole wall collapse was effectively eliminated.
Study on Mechanisms of a Highly Adsorptive Polyol Ester Bonded Lubricant for Water Based Drilling Fluids
TAO Huaizhi, MING Xiansen, MA Guangchang, YANG Xukun, JIANG Guancheng
2022, 39(5): 579-586.   doi: 10.12358/j.issn.1001-5620.2022.05.008
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Common lubricants used in water based drilling fluids have weak adsorption on the friction interfaces of metals, and therefore are difficult to form dense and shear-resistant lubricating films thereon, which leads to high friction and torque during drilling. High friction and torque generally result in pipe sticking and high overpull or resistance during tripping of drill string. To improve the adsorption of drilling fluid lubricants on the surfaces of drilling tools, a polyol ester bonded lubricant was developed with a polyol and a long-chain fatty acid through dehydration condensation reaction. This new lubricant worked better in extreme pressure friction test, filter cake adhesion test and “point-to-point” friction test than similar products both from China and abroad. It can be used at temperatures up to 150 ℃. The working mechanisms of the lubricant were studied through four-ball friction test, SEM observation and X-ray photoelectron spectroscopy etc. It was concluded that the polyhydroxy structure of the lubricant can form bonded adsorption on the surface of Fe, which is stronger than the general physical adsorption, it thus can form a dense and shear-resistant lubricating film, having a thickness of about 45 nm, on the surfaces of drilling tools. The lubricant can also be adsorbed onto the surfaces of barite particles, thereby reducing the internal friction of a drilling fluid.
The Synthesis and Evaluation of a Pentaerythritol-Based Hyperbranched Polymer Filter Loss Reducer
SONG Yongtao, ZHOU Feng, YU Weichu, ZHANG Ying, SHU Wenming
2022, 39(5): 587-595.   doi: 10.12358/j.issn.1001-5620.2022.05.009
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Filter loss reducers presently in use have some deficiencies such as great negative impact on mud rheology, poor high temperature resistance and poor salt contamination resistance etc. To overcome these deficiencies, a pentaerythritol-based hyperbranched polymer filter loss reducer PPAAN-1 was developed through radical polymerization with tetraallyl ether (PPTE, a polyene monomer with pentaerythritol as its core molecular structure), 2-acrylamido-2-methylpropanesulfonic acid (AMPS), N-vinyl pyrrolidone (NVP) and acrylamide (AM) as raw material. Based on orthogonal experiment results, the effects of the concentration of the tetraallyl ether on the apparent viscosity of the filter loss reducer PPAAN-1 was also studied. The optimum synthesis condition of PPAAN-1 was finally determined as follows: concentration of PPTE = 17%, AMPS∶AM∶NVP = 2 ∶6∶1, reaction temperature=55 ℃, initiator (AIBN) concentration = 0.2%. In laboratory evaluation, the properties of PPAAN-1 were compared with Driscal and DrisTemp. PPAAN-1 has little effect on mud rheology, good thermal stability and good filtration control capacity. The thermal decomposition temperature of PPAAN-1 is 302.29 ℃. A 30% NaCl drilling fluid treated with 1% PPAAN-1 had API filtration rate (220 ℃) of 9.8 mL and HTHP (150 ℃) filtration rate of 18.5 mL. In high temperature high salinity conditions, PPAAN-1 can form a network structure and adsorb on the surfaces of the clay particles, thereby widening the range of the particle size distribution of clays in a drilling fluid, helping the drilling fluid form dense mud cakes, and reducing the filtration rate of the drilling fluid.
Friction reduction of oleamide lubricants on iron surface
ZHANG Shuncong, DAI Yao, XU Hao, WANG Jiqian, LU Fuwei, LIU Guiying
2022, 39(5): 596-600.   doi: 10.12358/j.issn.1001-5620.2022.05.010
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The adsorption and lubrication properties of four surfactants on the iron surface based on molecular simulation was investigated. Surfactants include oleamide, oleic acid diethylenetriamine, oleic acid triethylenetetramine, and oleic acid tetraethylenepentamine. Results of adsorption simulation showed that the adsorption energies enlarged with the increase of nitrogen atom content. The adsorption energy of oleic acid tetraethylenetetetramine molecule on the iron surface was −1512.4679 KJ·mol−1, which was higher than other three amides. Results of shear dynamics simulation showed that the nitrogen atoms of four surfactants were concentrated on the iron surface. With higher nitrogen content, oleic acid tetraethylenepentamine adsorbed on the shear surface preferentially. On this surface, the nitrogen atom was about 1.6 times the density of the fixed surface. Results of four-ball friction experiment showed that the friction coefficient and the wear scar radius decreased as the nitrogen atom content increased. The friction coefficient of oleic acid tetraethylenepentamine was 0.004,36, which was 1/2 of oleamide. The wear scar radius of oleic acid tetraethylenepentamine was 241.7 μm, which was smaller than other three amides. Results of molecule simulation and experimental showed that the oleamide surfactant has better lubrication effect on the iron surface as the atom content of nitrogen in the molecule increase.
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](827) [PDF 1051KB](979)
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](529) [PDF 2843KB](230)
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%。
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](695) [PDF 540KB](281)
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](1145) [PDF 4926KB](514)
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。
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](789) [PDF 2528KB](610)
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](269) [PDF 2049KB](156)
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](364) [PDF 11047KB](199)
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 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](418) [PDF 4562KB](396)
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](527) [PDF 6834KB](239)
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。
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](525) [PDF 1759KB](490)

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。

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](4635) [PDF 5710KB](45)
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](827) [PDF 1051KB](56)
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](484) [PDF 2116KB](25)
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](359) [PDF 729KB](19)
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.
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](789) [PDF 2528KB](52)
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.
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](535) [PDF 2831KB](26)
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](454) [PDF 2703KB](18)
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](301) [PDF 4092KB](15)
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.
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](393) [PDF 963KB](33)
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.
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](468) [PDF 604KB](63)
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.
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