斜井及水平井在不同构造应力场水力压裂起裂研究

HYDRAULIC FRACTURING OF DEVIATED WELL AND HORIZONTAL WELL UNDER DIFFERENT TECTONIC STRESS FIELD

水力加砂压裂是储层特别是低渗透储层改造的重要手段。压裂施工时,储层破裂压力直接决定水力压裂的成功与否。影响储层破裂压力的因素较多,例如射孔相位、密度、孔径等,但对于斜井或水平井,构造应力场及其与井身结构之间的匹配关系对破裂压力和初始起裂方向影响更为显著。在压裂施工中,由于缺乏对上述因素的认识,常常导致施工因压力过高而中止。基于线弹性断裂力学结合岩石的抗拉破坏准则,对构造应力场进行分类,展开了不同构造应力场下斜井和水平井压裂施工中破裂压力及裂缝起裂方向研究,为水力压裂起裂及优化设计提供参考依据。

Hydraulic sand fracturing is an effective way of stimulating the tight reservoir. When fracturing, the fracture pressure of reservoir is crucial. There are many factors of influencing the fracture pressure, such as perforating phase, perforating density, and the depth of the perforating etc. And for deviated well or horizontal well, the geo-structure stress field and the match relation between it and the casing programme have great influence on initiation pressure. Being short of knowledge about the factors above, the fracturing is often suspended by over-high pressure. Therefore, based on the liner-elastic and fracture mechanics theory, the generic model is established to predict the initiation pressure of fracture and its orientation when hydraulic fracture on a deviated or horizontal wellbore under the different geo-structure stress field, which could be used for the fracture optimum design.