摘要
准噶尔盆地南缘侏罗系致密砂岩储层埋深普遍大于4500 m,储层物性差,裂缝是重要的储集空间和主要的渗流通道,影响深层致密砂岩的油气富集分布和产能。通过野外露头观测、岩心、薄片和实验资料,对侏罗系储层裂缝发育特征、控制因素及有效性进行了研究。准噶尔盆地南缘侏罗系储层以发育高角度构造裂缝为主,其次是成岩裂缝和异常高压裂缝。准噶尔盆地南缘构造裂缝的方位主要有NNE-SSW向、NNW-SSE向、NEE-SWW向和NW-SE向,但中段NNW-SSE向裂缝不发育,且由东向西,构造裂缝的发育程度逐渐降低。构造裂缝的形成和分布受应力场、构造、岩性、层厚及储层非均质性等因素的影响,而裂缝的渗流能力则与流体活动、异常高压和现今地应力分布等因素相关。研究区裂缝的有效性较好,有效裂缝比例占85%以上。高压渗流实验结果显示围压增加,裂缝渗透率呈负指数递减。当有效围压小于15 MPa(埋深>1000 m)时,裂缝渗透率随围压的变化快;超过该围压(深度),裂缝渗透率递减缓慢;至最大实验轴压115 MPa(埋深>8000 m),围压为65 MPa时,裂缝的渗透率仍有22.5×10^-3μm^2。表明即使在深层,天然裂缝仍然是有效的储集空间和渗流通道,是改善深层致密储层储渗性能和油气富集高产的重要因素。
The Jurassic tight sandstones at the south margin of the Junggar Basin are characterized by great burial depth(more than 4500 m),poor physical properties and natural fractures that serve as the dominant storage space and percolation channels for hydrocarbon.A study on the characteristics,controlling factors and effectiveness of the fractures is carried out with field outcrop observation,core and thin section data analyses as well as experimental results.The result shows that high-angle structural fractures dominate the sandstones,followed by diagenetic fractures and fractures related to overpressure.The fractures are mostly NNE-SSW-,NNW-SSE-,NEE-SWW-and NE-SW-trending,but NNW-SSE-trending fractures are rarely seen in the middle of the margin and density goes down from east to west.The distribution and formation of the fractures are controlled by stress field,tectonic movement,lithology,layer thickness and reservoir heterogeneity,while the permeability of the fractures is related to fluid activities,overpressure and present in-situ stress.The results also indicate that more than 85%of the fractures in the study area are effective.The high-pressure percolation experiment demonstrates a negative power exponent decrease of the fracture effectiveness with increasing confining pressure.However,the fracture permeability decreases differently under different confining pressure ranges.It decreases rapidly with the increase of the confining pressure less than 15 MPa(at a burial depth of over 1000 m).The reduction slows down when the pressure exceeds 15 MPa.And at a confining pressure of 65 MPa(equal to the maximum experimental axial pressure of 115 MPa or a burial depth of more than 8000 m),the permeability stays at 22.5×10^-3μm^2.Therefore,natural fractures are still the effective storage space and seepage channels even in deep formations,where they serve to improve physical properties and indicate high-quality deep reservoirs.
作者
毛哲
曾联波
刘国平
高志勇
田鹤
廖青
张云钊
Mao Zhe;Zeng Lianbo;Liu Guoping;Gao Zhiyong;Tian He;Liao Qing;Zhang Yunzhao(State Key Laboratory of Petroleum Resources and Prospecting,China University of Petroleum(Beijing),Beijing 102249,China;College of Geosciences,China University of Petroleum(Beijing),Beijing 102249,China;RIPED Petroleum Geology Research and Laboratory Center,PetroChina,Beijing 100083,China)
出处
《石油与天然气地质》
EI
CAS
CSCD
北大核心
2020年第6期1212-1221,共10页
Oil & Gas Geology
基金
国家科技重大专项(2016ZX05003-001,2017ZX05009001,2017ZX05049006-001)。
关键词
裂缝有效性
裂缝
致密砂岩
深层
侏罗系
准噶尔盆地南缘
前陆盆地
effectiveness of fracture
natural fracture
tight sandstone reservoir
deep formation
Jurassic
south margin of the Junggar Basin
foreland basin
