深层致密砂岩气藏高异常破裂压力影响因素分析

Analysis on factors inducing abnormal high fracture pressure of deep tight sandstone gas reservoir

川西坳陷深层气藏具有超埋深、超高压、圈闭形成历史复杂等特征,压裂施工难度大。现有压裂及测试资料表明该套地层存在高异常破裂压力。通过对可能引起致密砂岩储层高异常破裂压力的影响因素研究后发现,导致高破裂压力的因素主要有地质因素和工程因素,如储层致密、岩石中含有较多黏土矿物及层状、网状、斑状碳质层、地层超压、钻井诱导井眼附近应力场畸变、流体能量损失等。研究结果可为今后在该地区开展储层压裂改造提供参考。

The deep gas reservoir of Western Sichuan Depression features in super depth, ultrahigh pressure, and complicated trap formation, so fracturing gets difficult. The reservoir may have abnormal high fracture pressure. The factors that may lead to the abnormal high fracture pressure of tight sandstone reservoir are studied in this paper. The tensile strength of rock increases due to the super tight reservoir. The high level of clay minerals of the rock and the presence of a large number of laminated, reticulation, porphyritic rocks result in the the increase in the carbon layer of plastic and the additional pressure caused by overpressure formation. All these above are the geological factors leading to the increase in formation fracture pressure. Engineering factors are mainly the following： the aberration of stress field near a hole induced by drilling may result in the increase in rupture pressure of no-crack formation. The formation fracture pressure may be caused by the fluid energy loss during the extension of cracks, the fluid flow friction, and the bending friction caused by bending cracks. The analysis of the main factors that may induce the abnormal high fracture pressure of the studied area is favorable for carrying out reservoir fracturing in the area in near future.