摘要
准噶尔盆地吉木萨尔凹陷二叠系芦草沟组发育一套致密储层,致密储层低孔致密的特征决定了裂缝对于改善其孔渗结构十分关键。通过野外露头、岩心、铸体薄片和扫描电镜观察,识别出芦草沟组致密储层主要发育构造缝、成岩缝和异常高压缝3种类型裂缝。构造缝包括剪切缝和扩张缝,成岩缝包括层理缝、粒内缝和粒间缝,异常高压缝主要为泄水缝。构造缝多数为高角度,与准噶尔盆地经历的几期构造运动有关。层理缝存在两种可能成因,包括构造作用和生烃作用;粒内缝和粒间缝的成因与溶蚀作用有关。泄水缝的成因是岩层在受到异常流体高压时,其中一个应力变为张应力,形成走向弯曲开度不一的裂缝脉群。通过对上甜点体13口井和下甜点体8口井的成像测井统计,发现构造缝发育较少,其密度多在0.5条/m以下;而层理缝密度高很多,多在2条/m以上;结合岩心观察统计发现,层理缝是芦草沟组致密储层最主要的裂缝类型,占总数的70%以上。影响芦草沟组致密储层裂缝发育的控制因素包括沉积微相、岩性、岩层非均质性、岩层厚度、有机碳含量和构造作用等。
The Permian Lucaogou Formation in the Junggar Basin contains typical tight reservoir with low porosity, where natural fractures are of great importance for improving the seepage structure. Based on analysis of outcrops, cores, casting thin sections and scanning electron microscope （SEM）, three types of natural fractures were identified in the Lueaogou Formation tight reservoir, including structural fractures, diagenetic fractures and abnormally high-pressure fractures. The structural fractures include shear fractures and expansion fractures, which are usually high-dipped and were developed during several stages of tectonic movements in the Junggar Basin. The diagenetic fractures consist of bedding, intragranular and intergranular fractures, of which the bedding fractures might be formed during tectonic action and hydrocarbon generation, while the intragranular and intergranular fractures are related to dissolution. The abnormally high-pressure fractures, mainly drainage fractures, are the products of extremely high fluid pressure which induced one principal stress to convert into tensile stress and produced fracture clusters in bent orientation and with different openings. Imaging logging statistics of 13 wells drilled into the upper ＂sweet spot＂ and 8 wells drilled into the lower ＂sweet spot＂ reveal less structural fractures - generally less than 0.5 fractures/m, and well-developed bedding fractures - generally more than 2 fracture/m. Core observation further confirms that the bedding fractures are primary in the Lueaogou Formaion tight reservoir, accounting for over 70%. Primary factors controlling the development of natural fractures in the Lucaogou Formation tight reservoir are sedimentary microfacies, lithology, heterogeneity, layer thickness, TOC and tectonic action.
出处
《中国石油勘探》
CAS
北大核心
2017年第4期36-47,共12页
China Petroleum Exploration
基金
国家重点基础研究计划(973)项目"陆相致密油甜点成因机制及精细表征研究"(2015CB250901)
国家自然科学基金(青年基金)项目"天山地区上二叠统-中
下三叠统不整合类型及成因机制"(41502209)
中国石油大学(北京)引进人才科研启动基金"鄂尔多斯盆地上三叠统延长组储层评价及控制因素研究"(2462014YJRC031)
关键词
吉木萨尔凹陷
芦草沟组
天然裂缝
成像测井
发育特征
控制因素
Jimsar sag, Lucaogou Formation, natural fractures, imaging logging, development characteristics, controlling factors
