川东北宣汉-达县地区构造应力场对裂缝的控制

摘要

川东北宣汉—达县地区晚白垩世受到南东方向的挤压作用,始新世晚期—渐新世早期受到北东方向的挤压作用,两期构造活动导致宣汉—达县地区下三叠统飞仙关组碳酸盐岩中形成构造裂缝,对油气藏开发产生较大的影响.在考虑岩层与岩层之间相互影响的基础上,结合共轭节理和机械双晶的分析结果,利用三维有限元分析技术,计算宣汉—达县地区飞仙关组古构造应力大小,获得了两期古构造应力场的分布特征.通过岩石破裂阈值的限定,对普光、毛坝区块构造裂缝(张裂缝和剪裂缝)的发育区域进行预测,依据综合破裂率对岩层破裂强度进行评价,为提高裂缝钻遇率,降低勘探开发风险提供了科学的地质依据.%Structural stress field is one of the main reasons on fracture formation. It is the key of prediction structural fracture that paleostructure stress field is microscopically quantitative calculated. So we can well understand the fracture distribution in underground strata based on careful analysis to geological structure and numerical model coincides with the practice about the region of interest. It was influenced due to squeezing process from the SE direction during Late Crataceous and compressed from the NE direction in the period of Late Eocene-Early Oligocene in the Xuanhan-Daxian area of the northeast of Sichuan, China. The structural fracture development in Feixianguan formation in Lower Triassic series was effected by the two periods of structural action in Xuanhan-Daxian region. The fracture is an important geologic factor affecting the development of the oilfield. Through analysis of interaction in rock layers, calculation results on conjugate joints and mechanical twinning and using three dimensional finite element analysis method, we have obtained paleostructure stress in Feixianguan Formation of Xuanhan-Daxian region* We well know the distribution feature of paleostructure stress on the two periods. By threshold value-limited of the carbonatite burst, fracture area in Puguang and Maobawe blocks was predicted prediction. The integrated fracture rates give the basis to evaluate fracture strength. It provides the scientific geological basis for increasing the rate of drilling fractures and reducing the risk and cost of exploration and development.