镇泾地区延长组多期次裂缝发育特征及分布

摘要

According to the analysis and summary of outcrops,non-directional cores,imaging logging data,the measured results of the stable isotopes in fracture fillings,and the acoustic emission experiments of core samples,this paper analyses the characteristics and the formation periods and genetic types of the natural fractures in Ordos Yanchang Formation.The results show that there mainly are vertical fractures and high angle fracture in this block,whose main group system is S-N and N-E.There develops tension fractures and shear fractures.The fractures of the study area are thought to be 3 rupture periods.The main rupture period is the second episode of Yanshan phase, whose corresponding depth is 1190 m.The results of the comprehensive analysis show that there are multiple phase regional fractures and fault symbiotic fractures.Using the fault symbiotic fracture evaluation software and the FLAC3D rock fracture simulation software,the plane distribution of the fault symbiotic fractures and the multiple phase regional fractures can be predicted and evaluated.The results show that the regional tectonic fractures in the south of this block develop more than that in the north,and the more of sand bodies,the more of the fractures.The development degree of the fracture over the range of the fractured zone is generally higher than that of the non-fractured zone.%根据野外、非定向岩心、成像测井、裂缝充填物的稳定同位素测定、岩心的声发射实验等资料对鄂尔多斯盆地镇泾地区延长组天然裂缝特征、形成期次及成因类型进行分析，结果表明该区裂缝以垂直和高角度裂缝为主，主要组系为南北向、北东向，发育张破裂和剪破裂2种裂缝类型；延长组裂缝有3个破裂期，主要破裂期为燕山期第Ⅱ幕，对应埋深约为1190 m；研究区存在多期的区域性裂缝及断裂共（派）生裂缝。运用断层共生裂缝参数评价软件和FLAC3D岩石破裂数值模拟软件，预测和评价断层共（派）生裂缝和多期次区域构造裂缝的平面分布。结果表明，南部的区域构造裂缝比北部发育，砂体越多的地方裂缝发育程度也越高，断裂带范围内裂缝发育程度普遍高于非断裂带范围。