基于构造应变分析的裂缝预测方法及其应用

地层应变是构造裂缝产生的直接因素，根据构造应变大小可以预测构造裂缝发育的位置和强度，对研究区的主要裂缝发育区进行划分。文章以松辽盆地徐家围子断陷徐中地区营城组四段（简称营四段）为研究对象，在建立研究区精细的三维构造模型基础上，利用“构造恢复”方法实现研究区古构造恢复，通过开展有限应变值计算来预测构造裂缝的平面分布。研究表明:研究区营四段主要包括3个造缝期，即营城组末期、泉头组—青山口组时期、嫩江组时期，其中，营城组末期与泉头组—青山口组时期的构造变形较为强烈，是裂缝的主要形成时期。根据应变大小与试气产量的关系，将研究区划分为3类裂缝发育区，Ⅰ类裂缝发育区已钻井验证，表明利用构造应变对裂缝的预测结果可靠，Ⅱ类裂缝发育区可作为深层天然气的下一步挖潜的重要方向，Ⅲ类裂缝发育区产能较低，裂缝对储层的改造作用有限。 

The methods of fracture prediction based on structural strain analysis and its application

Formation strain can directly affect the generation of structural fractures. According to the magnitude of structural strain, the location and intensity of structural fracture development can be predicted, and the chief fracture development areas in the study area can be divided. This paper takes the fourth member of the Yingcheng formation (referred to as the YING-4 section) in the Xuzhong area of the Xujiaweizi rift in the Songliao basin as the research object. Based on establishing a detailed 3D structural model of the study area, we used the “structural restoration” method to restore the paleo-structure of the study area and calculated finite strain values to predict the planar distribution of structural fractures. The research shows that the YING-4 section in the study area mainly includes three fracture-making periods, namely the end of the Yingcheng formation, the Quantou–to–Qingshankou formation, and the Nenjiang formation. Among them, the tectonic deformation at the end of the Yingcheng formation and the Quantou–to–Qingshankou formation is relatively strong, which is the main formation period of the fracture. The study area is divided into three types of fracture development zones according to the relationship between strain size and test gas production. Type I fracture development zone has been verified by well-drilling, indicating that the prediction results of fractures using structural strain are reliable. Type Ⅱ fracture development zone can be used as an important direction for the next step of deep natural gas exploration. Type Ⅲ fracture development zone has low productivity, and the fractures have limited effect on reservoir reconstruction.