Mechanism of Fluid Shale Interaction and Construction of Drilling Fluid System in Marine Land Transitional Shale Reservoirs
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摘要: 我国海陆过渡相页岩地质储量大、资源丰度高,开发前景广阔。但钻井过程中井壁极易发生掉块、坍塌,导致井壁失稳影响钻井安全。本文通过钻井岩心观察、电镜和CT扫描、X射线衍射分析等相关实验,得到储层岩样矿物组分及微观结构等特征,结果表明:页岩气储层全岩主要含石英和黏土矿物,地层黏土矿物含量高达45.7%,且黏土矿物中不含蒙脱石,高岭石含量为35%,伊/蒙混层含量为26%;岩样表面纳微米孔隙和微裂缝发育,裂缝宽度在微米级并连通多条窄裂缝;通过岩液作用后晶层间距、表面张力、线性膨胀率和裂缝扩展变化分析,海陆过渡相页岩仅发生表面水化,揭示了海陆过渡相页岩气储层岩液作用机理。优选了水基钻井液抑制剂、封堵剂与润滑剂,构建了一套海陆过渡相页岩气储层的高性能水基钻井液体系,并对其展开了室内评价。钻井液常规性能、抑制性、封堵性、润滑性评价实验结果表明,该钻井液体系抗温100 ℃,高温高压失水6 mL,泥页岩膨胀率为1.03%,钻井液润滑系数整体小于0.15,体系30 min的API滤失量较基浆降低40%,可对地层微裂缝实现有效封堵,且生物毒性EC50值为37 260 mg/L,属于无毒级别,能够满足海陆过渡相页岩气钻井作业施工对钻井液性能的要求并进行了现场应用,封堵防塌效果良好,可有效解决海陆过渡相泥页岩井壁失稳的技术难题。Abstract: China possesses abundant shale geological reserves and a high concentration of resources in the coastal transition zone. However, drilling operations in this area are susceptible to wall collapse and instability, creating significant risks. This study investigates the mineral composition and microstructure of reservoir rocks through drilling core observation, electron microscopy, CT scanning, and X-ray diffraction analysis. The findings reveal that the shale gas reservoir is predominantly composed of quartz and clay minerals, with a clay mineral content of 45.7%. Notably, montmorillonite is absent, while kaolinite represents 35%, and the illite/montmorillonite mixed layer accounts for 26% of the clay minerals. The rock samples exhibit nano-scale pore development, micro-crack formation with widths in the micron range, and interconnected narrow cracks. Analysis of alterations in interlayer spacing, surface tension, linear expansion rate, and crack expansion after rock-fluid interaction unveils that shale in the coastal transition zone solely undergoes surface hydration, offering insights into the mechanisms of rock-fluid interaction in shale gas reservoirs. Consequently, a high-performance water-based drilling fluid system specifically designed for the coastal transition zone shale gas reservoir is formulated, encompassing the selection of water-based drilling fluid inhibitors, plugging agents, and lubricants. The system is subsequently subject to comprehensive laboratory evaluation, which substantiates its exceptional performance in terms of conventional properties, inhibitory effects, sealing capabilities, and lubrication. It demonstrates a temperature tolerance of up to 100 ℃, experiences a fluid loss of merely 6 mL under high-temperature and high-pressure conditions, exhibits a shale swelling rate of 1.03%, possesses an overall drilling fluid lubrication coefficient of less than 0.15, reduces API filtration loss by 40% compared to the base slurry after 30 min, and effectively seals micro-cracks in the reservoir formations. Additionally, the system demonstrates a low level of biotoxicity, with an EC50 value of 37,260 mg/L. It can meet the requirements of drilling fluid performance for transitional shale gas drilling operations between sea and land, and has been applied on site with good sealing and anti-collapse effects. This research addressing the considerable technical challenge of wall instability in the coastal transition zone shale wells.
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表 1 大吉3-4山西组海陆过渡相页岩全岩矿物组成及黏土矿物组成表
矿物组成/% 黏土矿物/% 石 英 钾长石 斜长石 菱铁矿 黄铁矿 铁白云石 黏土矿物 伊蒙混层 伊利石 高岭石 绿泥石 43.0 0.4 1.2 3.3 2.0 4.4 45.7 26 29 35 10 表 2 山西组海陆过渡相页岩岩心粉溶解水样的水质组成
阳离子 矿化度/(mg·L−1) 阴离子 矿化度/ (mg·L−1) Na+ 529.233 F− 1.191 K+ 543.693 Cl− 363.666 Ca+ 111.285 Br− 0.924 Mg2+ 10.590 NO32− 0.594 Sr2+ 5.280 SO42− 1594.386 Ba2+ 0.393 NO2− 0.843 表 3 岩样在不同抑制剂溶液中的毛管力
抑制剂 接触
角/°表面张力/
mN·m−10.1 μm微裂缝
毛管力/MPa0.5 μm微裂缝
毛管力/MPa去离子水 9.20 72.75 1.44 0.29 1%聚胺 14.70 58.03 1.12 0.22 1%KCl 14.20 72.30 1.40 0.28 1%甲酸钾 14.40 71.11 1.38 0.28 1%疏水抑制剂 35.50 36.64 0.60 0.12 1%甲酸钠 14.40 71.73 1.39 0.28 表 4 山西组海陆过渡相页岩浸泡后裂缝扩展情况
浸泡时间/d 去离子水 1%甲酸钾 1%KCl 1%聚胺 1%疏水抑制剂 0 3 13 表 5 不同浓度KCl和甲酸钾水活度
序号 样品 水分活度 1 1%甲酸钾 0.968 2 3%甲酸钾 0.961 3 5%甲酸钾 0.958 4 3% KCl 0.965 5 5% KCl 0.953 6 7% KCl 0.943 表 6 白沥青加量优选
编号 膨润土浆/% 白沥青/% FLAPI/mL 1 2 0 40 2 2 1.0 30 3 2 1.5 26 4 2 2.0 24 5 2 2.5 23 6 2 3.0 22 7 2 3.5 20 表 7 超细碳酸钙加量优选
编号 CMJ-2/
%白沥青/
%乳化石蜡/
%超细碳酸/
%微孔滤膜
滤失量/mL1 7.8 2 1 2 1 1 7.2 3 1 2 1 2 7.0 4 1 2 1 2 6.4 5 1 2 1 3 6.0 6 1 2 1 4 6.6 表 8 CMJ-2加量优选
编号 CMJ-2/
%白沥青/
%乳化石蜡/
%超细碳
酸钙/%微孔滤膜
滤失量/mL1 0.5 2 1 3 6.6 2 1.0 2 1 3 6.0 3 1.5 2 1 3 5.6 4 2.0 2 1 3 5.6 表 9 乳化石蜡加量优选
编号 CMJ-2/
%白沥青/
%乳化石蜡/
%超细碳
酸钙/%微孔滤膜
滤失量/mL1 1.5 2 1.0 3 5.6 2 1.5 2 1.5 3 5.4 3 1.5 2 2.0 3 4.8 4 1.5 2 2.5 3 5.2 5 1.5 2 3.0 3 5.4 表 10 不同润滑剂极压润滑系数
样品 老化前/后润滑系数 基浆 0.486/0.527 2.0%高密度钻井液润滑剂+2%基浆 0.150/0.151 2.0%甘油单油酸酯+2%基浆 0.112/0.126 2.0% LUBE +2%基浆 0.144/0.162 2.0%油酸甲酯+2%基浆 0.142/0.145 注:实验条件,80 ℃条件下热滚16 h后常温条件下测定。 表 11 水基钻井液老化前后性能
条件 AV/
mPa·sPV/
mPa·sYP/
PaGel/
Pa/PaFLAPI/
mLFLHTHP/
mLEP 老化前 35.0 27 8 2/16 4.4 8.8 0.0850 80 ℃老化后 41.0 32 9 3/18 3.4 6.0 0.1147 100 ℃老化后 41.5 32 9.5 2/17 2.6 6.0 0.1225 表 12 不同污染条件下钻井液老化前后性能
污染源 实验
条件AV/
mPa·sPV/
mPa·sYP/
PaGel/
Pa/PaFLAPI /
mL10%NaCl 热滚前 39.5 28.5 11.0 1/12 5.2 热滚后 36.5 29.0 7.5 2/11 4.0 1%CaCl2 热滚前 42.0 30.0 12.0 3.5/27 6.4 热滚后 49.0 33.0 16.0 15/34 5.2 8%膨润土 热滚前 43.5 33.0 10.5 3/25 4.4 热滚后 46.0 35.0 11.0 4/35 4.2 表 13 不同污染条件下钻井液老化前后性能
t/min 基浆滤失量/mL 水基钻井液体系滤失量/mL 0 0 0 10 4.5 2.4 20 7.8 3.2 30 10.2 4.2 表 14 JY-P03-1H井水平段钻井液性能
井深/
mρ/
g·cm−3FV/
sPV/
mPa·sYP/
PaPV/YP/
mPa·s/PaFLAPI/
mL滤饼厚度/
mmpH 2657 1.40 60 39 11.0 0.28 2.6 0.3 9 2796 1.41 65 40 12.5 0.31 2.6 0.3 9 2908 1.43 68 41 13.5 0.33 2.2 0.3 9 2993 1.45 70 39 11.5 0.29 2.6 0.3 9 3146 1.45 72 38 13.5 0.36 2.5 0.3 9 3232 1.45 71 37 13.5 0.36 2.6 0.3 9 3490 1.45 75 40 14.0 0.35 2.4 0.3 9 3603 1.45 75 40 13.5 0.34 2.4 0.3 9 3711 1.45 82 38 16.5 0.43 2.4 0.3 9 3865 1.45 87 37 17.5 0.47 2.4 0.3 9 -
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