油气储层开发程度对地质力学的影响规律

为研究油气储层注采不平衡引起的孔隙压力变化对地质力学造成的影响,通过建立含密闭断层的多孔介质弹性储层地质力学模型,分析正应力与剪应力的相关关系,研究了储层压力变化对断层附近水平地应力场的影响规律。结果表明:孔隙压力变化使得密闭断层附近产生剪应力,并造成储层地应力场大小和方向均发生变化,受剪应力出现的影响,地应力大小发生更大程度的线性降低;地应力方向也可能发生偏转,偏转角度是孔隙压力变化、断层夹角、岩石泊松比的函数;在考虑脱水作用与顶板效应后,储层压力变化对上覆盖层的地应力也会造成一定范围的影响,以渤海岐口18-1油田为例,评估了储层压力衰竭对盖层地应力场的影响范围不超过20 m。

The Influence Law of Oil and Gas Reservoir Development Degree on Geo-mechanics

In order to study the influence of pore pressure change caused by unbalanced injection and production in oil and gas reservoirs on geomechanics, the relationship between normal stress and shear stress was analyzed by establishing a geomechanical model of porous reservoir elastic reservoir with closed faults. The influence of pressure changes on the horizontal geostress field near the fault. The results show that the change of pore pressure causes shear stress near the closed fault, and the magnitude and direction of the stress field of the reservoir change. Due to the influence of shear stress, the magnitude of the ground stress decreases linearly. The direction of the geostress also decreases. Deflection may occur. The deflection angle is a function of the pore pressure change value, the angle of the fault, and the Poisson"s ratio of the rock. After considering the dewatering effect and the roof effect, the reservoir pressure change will also have a certain range of influence on the ground stress of the upper cover layer. Taking the 18-1 oilfield in Bohaikou as an example, the influence of reservoir pressure failure on the geostress field of the caprock is estimated to be no more than 20m.