川西大邑构造须家河组应力场数值模拟

Numerical Simulation of Stress Field in Xujiahe Formation of Dayi Structure Region in Western Sichuan

根据野外调查、钻井岩心、测井和地震解释等资料,结合构造应力场数值模拟,对四川盆地大邑地区须家河组裂缝进行了综合预测及评价。结果表明,构造裂缝的发育程度是大邑地区天然气高产的重要控制因素。川西大邑构造是龙门山前一个重要的三级构造,其须二、须三段整体为一个被F1、F2断层所夹持的南西扬起、北东倾伏,北西翼陡、南东翼缓的大型不对称鼻状构造。构造形成于早白垩世晚期的燕山Ⅱ幕构造运动,经历了早喜山期构造运动的进一步加强和改造,于晚喜山期最终定型。须二段Ⅰ砂组及须三段Ⅰ砂组裂缝均发育于F1、F2断层所夹持的构造轴部及近轴部区域,主体上呈北东向条带状展布。靠近断层带、羽状断层与主干断层形成的断块以及褶皱倾伏端裂缝相对发育,构造鞍部、斜坡裂缝发育程度则较差。

According to field survey,drilling cores,logging data and seismic interpretation,combined with the tectonic stress field numerical simulation,this paper has carried on the comprehensive prediction and evaluation of fractures of the Xujiahe Formation in the Sichuan Basin.The results show that the degree of development of tectonic fractures Dayi area gas yield is an important controlling factor.Dayi structure in Sichuan is an important three class structure of Longmenshan piedmont,the second and third members of the Xujiahe Formation is sandwiched by F1,F2 faults which SW raised,overturning the NE,NW steep,south east wing slow large asymmetric nose structure.Structure was formed in the late Early Cretaceous Yanshan tectonic movement,through the Early and Late Himalayan tectonic movement further strengthening and trans formation.The crack in sand groupⅠ of the second and third members of the Xujiahe Formation were developed in the F1,F2 fracture structure sandwiched-shaft portion and the near-axis region,the subject was on the north-east banded cloth.Near the fault zone,feathery main fault rupture and block the formation of cracks and folds overturning end relatively developed,constructed saddle,slope fracture development is poor.