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通过大安寨先导井焦页3-2HF井下全尺寸岩心及对应储层介壳灰岩露头岩心,开展介壳灰岩微观特征、岩石力学参数及水力压裂裂缝扩展物理模拟试验。结果表明:(1)介壳灰岩层间微缝隙及次生微孔隙较发育,孔隙度在0.04%~4.5%,平均1.4%左右,局部裂缝发育;(2)介壳灰岩在平行与垂直层理面方向存在弱各向异性特征,单轴压缩表现明显的硬脆性特征,有利于压裂缝的起裂与扩展延伸;(3)三轴压缩围压增加,试样的承载力和刚度提高,屈服应力和峰值强度增大,弹性模量较单轴时明显增大,破裂模式由脆性向延性转化;(4)介壳灰岩压裂后主要形成垂直于最小水平主应力方向的压裂裂缝,同时压裂缝可沟通天然裂缝,形成交叉压裂缝,有利于提高油气采收率通道。
The micro-features, rock mechanics parameters and physical simulation experiments of hydraulic fracturing propagation are carried out through the core of the full-size downhole and the corresponding limestone outcrop core in the Daanzhai Pilot Well 3JHF. The results show that: (1) microcracks and secondary micropores are more developed in the limestones of crust, with porosity ranging from 0.04% to 4.5% with an average of about 1.4% and local fractures developing; (2) Weak anisotropy in the plane direction and uniaxial compression with obvious hard and brittle features, which is favorable for the initiation and propagation of fractures; (3) the increase of triaxial compressive confining pressure and the increase of bearing capacity and stiffness of the specimen, yielding The stress and peak strength increase, the elastic modulus increases obviously as compared with uniaxial, and the fracture mode changes from brittleness to ductility; (4) Fracture cracks are formed mainly in the direction perpendicular to the minimum horizontal principal stress after crustal limestone fracturing, meanwhile, Fracturing cracks can communicate with natural fractures to form cross-fracturing cracks, which can help increase the channel of oil and gas recovery.