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筠连地区煤储层敏感性及配伍性分析

Analysis of coal reservoir sensitivity and compatibility in Junlian Area

  • 摘要: 储层敏感性,包括速敏、水敏、盐敏、酸敏和应力敏感性(五敏),直接影响钻井、压裂等施工过程中的流体选择和煤层气井产能。为查明筠连地区煤储层敏感性和注入流体配伍性,采集筠连地区二叠系乐平组C2+3和C7+8号煤层样品,分析其低温液氮吸附和核磁共振分析孔渗特征。在此基础上,通过岩心流动试验进行五敏性测试,并选择不同井的地层水与压裂液进行配伍性试验研究。研究结果表明:测试样品主体为半暗型煤、中高灰分、镜质体反射率在2.2%以上。煤层渗流孔发育较少,孔隙类型以吸附孔为主,微孔和小孔占优势且微孔-小孔与较大孔连通性差。低温液氮吸附测试的煤岩比表面积平均为4.55 m2/g,总孔体积平均值为0.004 9 mL/g。针对JL-1和JL-2两口井段煤岩样品,测试的速敏伤害率为20.74%和25.26%;水敏伤害率分别为12.52%和19.29%;盐敏损害程度分别为14.68%和19.84%;酸敏损害率为负伤害,分别为-0.077%和-0.057%;应力敏感性损害程度分别为76.82%和47.67%。根据SY/T 5358—2010《储层敏感性流动实验评价方法》,煤储层呈现弱速敏、弱水敏、弱盐敏性和无酸敏性,但分别表现出了中等偏弱和强应力敏感性。将地层水与压裂液过滤后分别按不同体积比例混合(0∶1、1∶1、1∶2)测其浊度,总体压裂液与地层水配伍性良好,浊度清亮,无沉淀产生。相关成果对查明煤储层敏感性影响因素,指导后续压裂施工提供科学依据和技术支持。

     

    Abstract: Reservoir sensitivities,including velocity sensitivity,water sensitivity,salt sensitivity,acid sensitivity and stress sensitivity (five sensitivities),directly affect the fluid selection and coalbed methane production in the process of drilling,fracturing and other engineering processes. In order to find out the coal reservoir sensitivity and fluid compatibility,samples of C2+3 and C7+8 coal seams of Permian were collected,and the characteristics of porosity and permeability were analyzed by low temperature liquid nitrogen adsorption and nuclear magnetic resonance. On this basis,five sensitivities test were carried out through core flooding,and the compatibility of formation water and fracturing fluid in different wells was studied. The results showed that the coals are mainly semi dull coal,medium to high ash content,with the vitrinite reflectance being higher than 2.2%. There are few seepage pores in the coal,and the pore types are mainly adsorption pores. Micropores and mesopores are dominant,and the connectivity between micro-meso pores and macropores is poor. The average specific surface area of coal is 4.55 m2/g and the average total pore volume is 0.004 9 mL/g. Focusing on samples from JL-1 and JL-2 wells,the velocity sensitive damage ratio is 20.74% and 25.26%,with the water sensitive damage of 12.52% and 19.29%,salt sensitive damage of 14.68% and 19.84%,acid sensitive damage of -0.077% and -0.057%,and stress sensitive damage of 76.82% and 47.67%,respectively .According to the standard of SY/T 5358—2010,the coal reservoir shows weak velocity sensitivity,weak water sensitivity,weak salt sensitivity and no acid sensitivity,while shows medium weak and strong stress sensitivity. After filtering formation water and fracturing fluid,the turbidity was measured by mixing them in different volume proportions (0∶1,1∶1,1∶2). The overall compatibility of fracturing fluid and formation water was good,the turbidity was clear,and there was no precipitation. The relevant results provide scientific basis and technical support for identifying the influencing factors of coal reservoir sensitivity and guiding the follow-up fracturing construction.

     

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