陕北安塞地区延长组长8段裂缝发育特征

(1.延长油田股份有限公司,陕西 延安 716000; 2.长安大学 地球科学与资源学院,陕西 西安 710054)

地质资源与地质工程; 裂缝; 古地磁定向; 延长组; 长8段; 陕北; 安塞地区

Development characteristics of fractures of Chang 8 member in Yanchang Formation in Ansai Area,North Shaanxi
WEI Fan-rong1,ZHANG Zhi-dong1,WU Xiang-yang1,FU Guo-min2

(1.Yanchang Oilfield Co.,Ltd.,Yan'an 716000,China; 2.Shool of Earth Science and Resources,Chang'an University,Xi'an 710054,China)

geological resources and geological engineering; fracture; paleo magnetic orientation; Yanchang Formation; Chang 8 member; North Shaanxi; Ansai Area

DOI: 10.13800/j.cnki.xakjdxxb.2018.0614

备注

应用相似露头及岩心裂缝统计分析技术、地下裂缝古地磁定向技术对鄂尔多斯盆地安塞地区延长组长8段裂缝发育程度及其特征进行研究,并与注水开发动态裂缝监测结果进行对比,发现安塞地区三叠系延长组长8段碎屑岩普遍发育天然裂缝,裂缝形成时期主要为燕山期和喜山期,裂缝以构造裂缝为主,裂缝面均直立、裂缝间距20~40 cm,受局部构造应力场控制裂缝发育程度和组系存在差异; 古地磁定向天然显裂缝及微裂缝方位计有4组,其中东北及其东南方向裂缝最位发育,平均方位角分别为64.5°及141.5°,次为东西向裂缝,平均方位角为190°,南北向裂缝不发育,平均方位为2.5°.注水开发动态裂缝监测结果表明:在现今北东60°~80°最大主应力作用下,人工裂缝优先沿北东向天然显裂缝开启延伸,注水效果明显,局部引起油井水窜,而西北-东南方向储层裂缝张开程度差,注水效果不明显,在注水开发中应充分考虑裂缝特征进行井网型式及其压裂作业参数优化。

It has been studied the development degree and characteristics of fracture characteristics of chang 8 member of Yanchang Formation in Ansai Area of Ordos Basin,with the application of statistical analysis technique on similar outcrops and core fractures,and underground fracture paleo magnetic orientation technique.Compared with the results of reservoir dynamic analysis technique,it is showed that natural fractures are commonly developed in the detrital rocks of Chang 8 member of Yanchang Formation of the Triassic in Ansai Area.The formation of the fractures is mainly in Yanshanian and Himalayan periods.The fractures are mainly structural fractures and the fracture surfaces are all upright.The fracture spacing is 20~40 cm,the fracture development degree and formation are different under the control of local tectonic stress field,4 sets of Paleomagnetic directional natural fracture and microfracture azimuth meter,in which both E-N trending fractures and E-S trending fractures are most developed,the average azimuth is 64.5° and 141.5° respectively and E-W trending fractures are secondly developed,the average azimuth is 190°,the N-S trending fractures is not developed,with an average azimuth of 2.5°.The monitoring results of waterflooding development show that under the present 60°~80° N-E trending major principal stress,artificial fractures preferentially extend along the N-E trending natural fractures,waterflooding effect is obvious,partly caused water channeling in oil well,but the open degree of NW-SE trending reservoir fractures are poor,waterflooding effect is not obvious.In waterflooding program,the characteristics of fractures should be fully consideredto optimize the spacing pattern and fracturing operation parameters.