潍北凹陷孔店组二段上亚段页岩气储层压裂可行性研究

Feasibility study on shale gas reservoir fracturing in the upper member of the Second Member of Kongdian Formation in the Weibei sag

始新统孔店组二段上亚段泥页岩是济阳坳陷潍北凹陷良好的页岩气储层,为了了解孔店组二段上亚段页岩气储层压裂可行性,在岩芯观察、有机地化分析、测井、扫描电镜分析、X衍射、岩石力学测试分析的基础上,对孔店组二段上亚段岩性特征、有机地化特征、地应力特征、裂隙发育特征、矿物含量特征、岩石力学特征、脆性指数等进行了研究。结果表明:潍北凹陷孔店组二段上亚段泥页岩发育厚度为40~160m,泥地比大于70%;有机碳含量一般为1%~3%,镜质体反射率为0.78%~1.04%,干酪根类型以Ⅱ1型为主,现场解析含气量平均值为1.2m3/t;现今最大水平主应力方向为近东西向;泥岩中裂缝发育,微裂缝沿矿物间隙延伸,连通性较好;脆性矿物含量为43.4%~65.2%,以脆性矿物计算的岩石脆性指数为42.5%~64.7%,脆性很强,黏土矿物含量为34.8%~56.6%,不含水敏性较强的蒙脱石;岩石力学计算获取的岩石脆性指数在6%左右,显示脆性较差;综合分析认为潍北凹陷孔店组二段上亚段页岩气储层具有较好的可压性,利于人工压裂改造,但也存在一定风险。

The upper shale in the Second Member of the Eocene Kongdian Formation is a good shale gas reservoir in the Weibei Sag,Jiyang Depression.In order to understand the feasibility of shale gas reservoir fracturing in the upper member of the Second Member of the Kongdian Formation,based on core observation,organic geochemical analysis,logging,scanning electron microscopy analysis, X-ray diffraction,rock mechanics test analysis,this article studied the lithologic characteristics and organic ground of the upper section of the second section,geostress characteristics,fracture development characteristics,mineral content characteristics,rock mechanics characteristics,brittleness index,etc.of the Kongdian Formation chemical characteristics.The results show that the thickness of the shale in the upper member of the Second Member of the Kongdian Formation in the Weibei Sag is 40~160 m,the mudto-earth ratio is greater than 70%,the organic carbon content is generally 1% to 3%,and the vitrinite reflectance is 0.78% ~1.04%;the type of kerogen is mainly type II1,and the average desorption gas content on site is 1.2 m3/t;the maximum horizontal principal stress direction is near east-west direction;the crack develops in mudstone,the micro-crack extends along the mineral gap,and connectivity is good;brittle mineral content is 43.4%~65.2%,rock brittleness index calculated from brittle minerals is 42.5%~64.7%,brittleness is strong,clay mineral content is 34.8% ~ 56.6%,and water sensitive montmorillonite is seldom;rock brittleness index obtained by rock mechanics calculation is about 6%,showing poor brittleness.In summary,the shale gas reservoir in the upper member of the second section of Kongdian Formation in the Weibei Sag has good compressibility,and is beneficial to fracture transformation,but there are also certain risks.