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Hole Cleaning Technology for Horizontal and Deviated Drilling: Progress Made and Prospect
CHANG Xiaofeng, SUN Jinsheng, WANG Qingchen
2023, 40(1): 1-19.   doi: 10.12358/j.issn.1001-5620.2023.01.001
Abstract(623) HTML(79) PDF (3943KB)(161)
Although progresses made in horizontal drilling have been very beneficial to the development of conventional and unconventional oil and gas, two factors related to the cleaning of drilled cuttings from the horizontal section of a well seriously hinder the drilling operation. One of the factors is borehole wall instability, and the other is the difficulties in wellbore cleaning. Inability to remove drilled cuttings from a wellbore in a timely manner often results in increases in friction and torque on the downhole drill string, and the frequency of pipe sticking, and the worse is the simultaneous occurrence of lost circulation. First in this paper, the causes of cuttings bed formation and technical parameters for field operation are analyzed and summarized from two aspects, which are hole cleaning mechanisms and the main factors affecting hole cleaning (mud rheology, pipe rotation, hole inclination, sizes of the drilled cuttings, mud weight and flowrate etc.). Second, the methods and mechanisms of cuttings removal were systematically elaborated from the drilling fluid technologies and hole cleaning tools available both in China and abroad to help deal with the difficulties in hole cleaning in deviated and horizontal drilling. Finally, the development direction for horizontal and deviated hole cleaning technology is prospected to provide a reference for the hole cleaning technology development in the future.
Specific Surface Area Measurement and Adsorption Characteristics of Drilling Fluid Weighting Materials
QIU Zhengsong, WANG Di, ZHANG Shuhao, WANG Qi, ZHONG Hanyi, ZHAO Xin, FAN Lijun
2023, 40(1): 20-27.   doi: 10.12358/j.issn.1001-5620.2023.01.002
Abstract(151) HTML(57) PDF (2397KB)(84)
In deep and ultra-deep drilling, weighting materials are added to the drilling fluids to produce a pressure that is enough to balance the formation pressure. Weighting materials added to a drilling fluid can adsorb water and additives, thus affecting and even exacerbating the properties of the drilling fluid. To investigate the form and adsorptive characteristics of weighting materials in a drilling fluid, a method of measuring the specific surface area of a weighting material in a liquid has been established based on low-field nuclear-magnetic resonance (LF-NMR). The specific surface area of a weighting material in water based drilling fluids with densities between 1.1 g/cm3 and 2.4 g/cm3 and the specific surface area of the same weighting material in dry powder state, and the change of the specific surface area of the weighting material in liquid and as dry powder were analyzed using the LF-NMR method and particle size estimation method. The adsorption capacity of a weighting material in fluids of different densities were investigated through organic carbon adsorption experiment and rheology measurement. It was found that the weighting material in fluids of different densities has different adsorption capacities for different mud additives. In three 500 mL drilling fluids, each of which has a density of 1.2 g/cm3, 1.8 g/cm3 and 2.4 g/cm3, respectively, the adsorption capacities of the weighting material for sulfonated lignite were 10.83 g, 13.06 g and 17.69 g, respectively. This testing result can be correlated with the specific surface area results obtained with LF-NMR.
A Pickering Emulsion Oil Based Drilling Fluid
LI Chao, DI Wenwen, GENG Tie, REN Liangliang, GAO Yaxin, HAO Tianhao, SUN Dejun
2023, 40(1): 28-34.   doi: 10.12358/j.issn.1001-5620.2023.01.003
Abstract(145) HTML(53) PDF (5511KB)(72)
In a Pickering emulsion, the solid particle emulsifier is absorbed at the interface between oil and water, forming a stable interfacial film to prevent the coalescence of water droplets. This property can be used to improve the stability of oil based drilling fluids. However, in studies on the oil based drilling fluids based on Pickering emulsion, the interaction between a water droplet in the oil phase and an inorganic hydrophilic particle has been omitted; the effects of inorganic particles added to an oil based drilling fluid, such as calcium hydroxide, weighting agents and the drilled cuttings, on the existence of the water droplets in the emulsion are not considered. In laboratory study, calcium hydroxide, barite and kaolinite particles of different hydrating capacities were added into a W/O Pickering emulsion. Macro sedimentation experiment and microscope observation with microscopic images have proved that the water droplets are combined with the solid particles, existing in a form of bound water. This explains the aggregation of the solid particles. The bound water was characterized with laser confocal microscope and low temperature differential scanning calorimetry. The solid particles with bound water can be dispersed by treating the system with a dispersant, in this way the stability of the drilling fluid can be improved. An oil based drilling fluid based on W/O Pickering emulsion is not a water-in-oil (W/O) drilling fluid, it is, however, a system in which the bound water droplets are moderately dispersed into an oil phase. In addition, low temperature constant rheology can be achieved by adjusting the rheology of a low density oil based drilling fluid.
Development and Application of an Environmentally Friendly Compound Filter Loss Reducer
SHU Yong, JIANG Luming, YANG Jun, JIANG Guancheng, WANG Guoshuai, HE Yinbo
2023, 40(1): 35-40.   doi: 10.12358/j.issn.1001-5620.2023.01.004
Abstract(169) HTML(58) PDF (2441KB)(84)
To control the pollution of drilling fluids to the environment from the source and minimize the difficulty and cost of waste drilling fluid treatment, a compound filter loss reducer PLS has been developed through crosslinking modification of plant polyphenol (a biomass material), sodium lignosulfonate and corn starch. PLS is non-toxic and is easy to degrade, it has an EC50 of 7.78 × 104 mg/L, and BOD5/CODCr of 5.05%. Evaluation of PLS shows that a base mud treated with 2% PLS has API filtration rate of only 9.6 mL after hot rolling at 180 ℃ for 16 hours. PLS is better than carboxymethyl starch, CMC-LV and SAP (an amphoteric starch graft copolymer) in resisting salt and calcium contamination. An environmentally friendly water based drilling fluid was formulated with PLS as the only filter loss reducer and other environmentally friendly additives such as bonding lubricant, organo- and hydro-phobic nanometer plugging agent and bionic borehole wall strengthening agent. This drilling fluid was used to drill the horizontal mudstone section of an exploratory well in Dagang oilfield. The rheology, filtration property of the drilling fluid during drilling were very stable, the mud cake had low friction coefficient and was thin and tough. The drilling operation was successful with no downhole troubles encountered throughout the horizontal section.
Development and Application of Environmental Friendly High Temperature Resistant Biomass Synthetic Resin Filtrate Reducer in Yuanba Area
ZHOU Qicheng
2023, 40(1): 41-46.   doi: 10.12358/j.issn.1001-5620.2023.01.005
Abstract(129) HTML(57) PDF (5467KB)(71)
In view of the fact that the marine carbonate formation in Yuanba area is often polluted by acid radical and hydrogen sulfide, which causes the viscosity and water loss of drilling fluid to rise, the temperature resistance to decline, and the flow pattern to be difficult to control, bringing great challenges to on-site maintenance. In this paper, a bio chemical method is proposed to modify lignin to develop an environment-friendly filtration reducer LDR of biomass synthetic resin with a cluster multi branch structure. The performance evaluation results show that the product has a temperature resistance of 200 ℃, a salt resistance of 25%, and a calcium resistance of 3,000 mg/L, showing a strong temperature and salt resistance performance. With this as the core of the high temperature resistant material, a high temperature resistant composite brine drilling fluid system is constructed by introducing potassium, calcium, and sodium plasma. Two wells were applied in Yuanba area. The field application shows that the maximum density of drilling fluid in Yuanba X-701 well is 2.34 g/cm3, the electric measurement shows that the temperature is 157 ℃, and the acid radical content is 21,157 mg/L. The system still has good rheological property and strong anti pollution ability. The two electric measurements successfully reached the bottom at one time, and the drilling fluid viscosity returned for 48 s after 7 consecutive days of standstill. It only took 28.88 days to complete the sidetracking task. The successful application of this system indicates that biomass resources have made a new breakthrough in high-temperature and high-density drilling fluid, effectively meeting the requirements of high-temperature slim hole for drilling fluid, and has good guidance and reference significance for deep wells and ultra deep wells in Yuanba area.
Lost Circulation Material and Technology Research of Self-healing Hydrogel
YANG Lili, WU Yunpeng, JIANG Guancheng, XIE Chunlin, ZHANG Yongwei
2023, 40(1): 47-53.   doi: 10.12358/j.issn.1001-5620.2023.01.006
Abstract(168) HTML(61) PDF (2749KB)(100)
Excessive development of pore fractures in the formation during drilling operations can lead to lost circulation and can easily result in safety incidents. In this research, a self-healing hydrogel based on cation-π, electrostatic, hydrogen bonding was prepared by a free radical polymerisation method for formation plugging, forming a dense sealing layer to contain lost circulation and prevent recurrence. Excellent self-healing properties in harsh conditions, with a self-healing efficiency of 70%, and can effectively seal the pores of 180 D sand discs with a sealing rate of nearly 90%. It also shows good sealing ability for other consolidated sand discs (permeability 2 D, 5 D, 20 D) and unconsolidated sand beds (20-40 mesh, 40-60 mesh, 60-80 mesh). Compared to conventional materials, the hydrogel can be self-healing by reducing the operating pressure drop to achieve an efficient seal. The self-repairing hydrogel can effectively improve the denseness of the sealing layers through secondary reduction of the permeability of the sealing layer, which improves the high temperature stability of the hydrogel and still has good sealing ability after high temperature aging. The hydrogel particles are well dispersed in the salt water and maintain stable rheological properties after hot rolling, which is beneficial for drilling fluid circulation. This study shows the potential of self-healing materials as plugging materials in the oil drilling industry.
Study on Construction Parameters of Pressure Bearing Plugging Considering High Stress Difference
QIU Xiaojiang, ZHANG Hongliang, WEI Yimeng, WU Ke, LIU Cheng, YANG Xinhui, YU Huichao
2023, 40(1): 54-59.   doi: 10.12358/j.issn.1001-5620.2023.01.007
Abstract(108) HTML(57) PDF (3892KB)(72)
As a common technology for the prevention and control of lost circulation in low pressure bearing formations, the theoretical system and plugging materials have made great progress, but the important construction parameters have not been paid enough attention. Therefore, according to the underground in-situ stress environment, this paper selects high-strength plugging materials, and establishes the pressure plugging experimental scheme with different construction parameters and plugging materials while drilling.The self-developed large-scale true triaxial pressure plugging experimental equipment is used to conduct the test on the dense sandstone sample (size: 300 mm×297 mm×297 mm), and the hydraulic-fracture propagation law was observed. Based on the hydraulic-fracture, the pressure plugging experiment was carried out.According to the experimental results, for the formation with weak bearing capacity, the construction parameters will cause the pressure change in the well, thus affecting the plugging effect; repeated plugging operations in the same formation will cause fracture expansion and reduce the plugging effect; the sequence of plugging slurry entering the fracture and the structure of the plugging layer are closely related to the geometric parameters of the fracture. The regular knowledge obtained in this paper can provide some reference for the formulation of pressure plugging scheme.
Study on Compatibility of Drilling Fluid Lubricants and Screw Rubbers
YANG Chuan, MENG Xiangjuan, KOXMAK Sayyara, LI Xu, TIAN Ming, LIU Feng, HUANG qian
2023, 40(1): 60-66.   doi: 10.12358/j.issn.1001-5620.2023.01.008
Abstract(115) HTML(57) PDF (2657KB)(60)
This paper discusses the experimental studies on the compatibility of drilling fluid lubricants with screw rubbers at high temperature and deep well conditions. At different temperatures and additive concentrations, eight kinds of rubbers were tested for rates of volume increment, rates of mass increment and changes in tensional strength when they were in contact with drilling fluid additives, and the test results were compared and evaluated. The experimental results show that the rubber sample has big changes in drilling fluids treated with the lubricants R-1 and R-3; in the drilling fluid treated with R-1, the rates of volume increment of the rubbers were distributed between 56% and 175%, while in the drilling fluid treated with R-3, the rates of volume increment were distributed between 49% and 148%. When the concentrations of the lubricants were increased, the rates of volume and mass increments of the two rubbers are all increased, and the rubbers swell at higher rates. These results indicate that the raw oil of a lubricant is the key factor affecting the swelling of rubber. Using GC-MS technology, the raw oils were analyzed, and it was found that a lubricant whose raw oil has high content of aromatics has relatively large influence on the swelling of the rubbers. Based on the application properties of the lubricants, some lubricants suitable for use in high temperature deep well drilling were selected. The selected lubricants were used to replace those lubricants with high contents of unsaturated hydrocarbons in the third interval and the reservoir section of the wells drilled in the Taipen block, and rubber disintegration from the screw was significantly reduced. Statistic data showed that times of rubber disintegration was reduced from 11 well times/month in the past to 0.5 well times/month, and this greatly reduced the number of times of tripping and improved the productive efficiency.
A Study on Borehole Wall Strengthening Technique and Its Application in Block Ledong
XING Xijin, XIE Renjun, QIU Zhengsong, LI Jia, GAO Jian
2023, 40(1): 67-72.   doi: 10.12358/j.issn.1001-5620.2023.01.009
Abstract(149) HTML(68) PDF (2554KB)(72)
The Ledong block, a typical high temperature high pressure offshore block, is located in the depression slope zone of the Yinggehai Basin. Some formations drilled in this block have narrow safe drilling windows and mud losses in deep hole occurred frequently during drilling. To deal with the mud losses, the drilling data was studied and the mechanisms and nature of the mud losses were analyzed. Using the viscous element method, the change of the stresses around the borehole before and after borehole wall strengthening was simulated, and the opening of the prefilled fractures predicted. Using a new experiment apparatus which can simulate the plugging of variable fractures, a study was conducted on the particle size distribution and concentration optimization for borehole wall strengthening. The experimental results show that the D50 criterion is a better particle size matching criterion, and a reasonable concentration of the particles is 5%. A drilling fluid that is suitable for use in the Ledong block and has the ability of borehole wall strengthening is developed through optimization experiment. In a comprehensive evaluation experiment, the additives for borehole wall strengthening showed little effects on the rheology of the drilling fluid. Sand bed test showed that the depth of the filtrate invasion was only 1.5 cm. Dynamic pressure bearing capacity of 1mm fractures tested with the drilling fluid can be as high as 12 MPa.
The Field Application of a Drilling Fluid for a Two-Interval Horizontal Well Penetrating Tight Gas Reservoir
KONG Weisheng, LI Xiaoming, HAN Chengfu, QU Yanping, WANG Qingchen, ZHAO Peng
2023, 40(1): 73-81.   doi: 10.12358/j.issn.1001-5620.2023.01.010
Abstract(117) HTML(60) PDF (3480KB)(70)
Two-interval horizontal well profile is used to develop the tight gas reservoirs in the Sulige gas field. Downhole problems such as coexistence of borehole wall collapse and mud losses, high friction and poor hole cleaning have long remained difficulties during drilling operations. Based on the analyses of the geological characteristics and the collapse mechanisms of shale formations, a model for friction and torque calculation is developed. The changes of friction and torque between different well profiles are compared. A new drilling fluid with good plugging capacity and lubricity was developed with a nanophase emulsion, plugging agents o hard and soft particles, compound lubricants and high efficiency gel strength additives which were all selected through laboratory experiment. This drilling fluid has been successfully applied in field operations. Laboratory study has shown that this drilling fluid has good inhibitive capacity and good plugging capacity, and it can extend the instability period of hard and brittle shales, thereby maintaining the borehole wall stable. This drilling fluid also has good rheology and lubricity, low sand content and solid content. In field application, the resistance to casing string running into the hole was controlled within 350 kN, the friction to drilling string running into the hole was reduced by 24.21%, the torque was reduced by 34.31%, the average drilling time was 29.04 d, the average ROP was 17.64 m/h, which was 36.5% higher than that in drilling three-interval horizontal wells. Time spent in reaming because of borehole collapse was reduced by 89.50%. This drilling fluid has provided a powerful technical support for promoting the application of two-interval horizontal drilling in developing the tight gas reservoirs in the Sulige gas field.
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](1013) [PDF 1051KB](992)
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](1352) [PDF 4926KB](531)
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](613) [PDF 2843KB](235)
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](820) [PDF 540KB](281)
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](317) [PDF 2049KB](156)
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](1031) [PDF 2528KB](630)
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](541) [PDF 4562KB](403)
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](431) [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。
Research on Mechanisms of Wellbore Instability of Longmaxi Shale Formation and High Performance Water Base Drilling Fluid Technology
TANG Wenquan, GAO Shuyang, WANG Chengbiao, ZHEN Jianwu, CHEN Xiaofei, CHAI Long
2017, 34(3): 21-26.   doi: 10.3969/j.issn.1001-5620.2017.03.004
[Abstract](393) [PDF 7199KB](167)
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](588) [PDF 6834KB](243)
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。
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](4885) [PDF 5710KB](90)
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](1013) [PDF 1051KB](88)
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](648) [PDF 2116KB](50)
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](502) [PDF 729KB](62)
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](1031) [PDF 2528KB](89)
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](675) [PDF 2831KB](50)
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.
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](660) [PDF 604KB](92)
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.
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](607) [PDF 2703KB](46)
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.
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](577) [PDF 963KB](62)
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 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](492) [PDF 4092KB](44)
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.
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