玛湖凹陷二叠系风城组深层陆相页岩储层天然裂缝及其有效性

刘国平; 金之钧; 曾联波; 何文军; 杨森; 李淑凤; 杜晓宇; 陆国青

doi:10.3799/dqkx.2023.128

地球科学 ›› 2024, Vol. 49 ›› Issue (07) : 2346 -2358. DOI: 10.3799/dqkx.2023.128

玛湖凹陷二叠系风城组深层陆相页岩储层天然裂缝及其有效性

刘国平 ¹ ,
金之钧 ¹^,² ,
曾联波 ¹^,³ ,
何文军 ⁴ ,
杨森 ⁴ ,
李淑凤 ⁴ ,
杜晓宇 ¹ ,
陆国青 ³

作者信息 +

Natural Fractures and Their Effectiveness in Deep Continental Shale Reservoirs of Permian Fengcheng Formation in Mahu Sag

Guoping Liu ¹ ,
Zhijun Jin ¹^,² ,
Lianbo Zeng ¹^,³ ,
Wenjun He ⁴ ,
Sen Yang ⁴ ,
Shufeng Li ⁴ ,
Xiaoyu Du ¹ ,
Guoqing Lu ³

Author information +

文章历史 +

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摘要

准噶尔盆地玛湖凹陷二叠系风城组陆相页岩最大埋深超过5 000 m，油气资源丰富，其中广泛发育的天然裂缝对烃类聚集和储层勘探开发具有关键作用.通过岩心、成像测井、薄片和扫描电镜观察，建立了基于地质成因和裂缝产状的深层陆相页岩天然裂缝分类方案，阐明了不同类型天然裂缝的发育特征和有效性，并讨论了深层陆相页岩天然裂缝的非均质性及其对储层的贡献.深层陆相页岩天然裂缝依据地质成因分为构造裂缝、成岩裂缝和异常高压相关裂缝.按照裂缝产状构造裂缝细分为穿层和顺层剪切裂缝、及层内张裂缝，成岩裂缝划分为层理缝、缝合线和收缩裂缝.构造裂缝规模相对较大，组系特征明显，主要以高角度和近直立为主.成岩裂缝主要为近水平发育，缝面弯曲、易分叉.层内张裂缝、层理缝和缝合线是深层陆相页岩储层的优势裂缝类型.天然裂缝可被方解石和含有机质的细粒混合物等矿物不同程度充填，其中构造裂缝和层理缝的充填程度较低，缝合线更易被充填.微观构造裂缝的开度较小，而成岩裂缝的开度通常较大.推测认为构造裂缝主要为储层中流体渗流提供了有效通道，层理缝发育程度更高，不仅是储层流体的渗流通道，也是其有效储集空间的重要组成部分.研究成果对于完善深层陆相页岩天然裂缝分类方案及深入认识这类储层天然裂缝分布规律具有重要的借鉴意义.

Abstract

The continental shale in the Permian Fengcheng Formation of the Mahu Sag in the Junggar Basin has a maximum burial depth exceeding 5 000 m, rich in oil and gas resources. The widely developed natural fracture plays a crucial role in the accumulation and exploration of hydrocarbons in these reservoirs. A classification scheme is established for natural fractures in deep continental shale based on their geological genesis and occurrence by observing cores, image logs, thin sections, and SEM samples. Moreover, the development characteristics and effectiveness of different types of natural fractures Were analyzed, and the natural fracture heterogeneity and their contributions to reservoirs are discussed. Accordingly, natural fractures in deep continental shale are divided into tectonic, diagenetic, and abnormal high-pressure related fractures based on their geological genesis. Tectonic fractures can be subdivided into translayer shear, bed-parallel shear, and intralayer open fractures based on their occurrence, while diagenetic fractures are divided into bedding, stylolite, and shrinkage fractures. Tectonic fractures have relatively large scales, obvious groups, and high dipping and nearly vertical angles. Diagenetic fractures mainly develop horizontally, with curved surfaces and easily branched extensions. Intralayer open, bedding, and stylolite fractures are the dominant types of fractures in deep continental shale reservoirs. Natural fractures can be filled in varying degrees by minerals such as calcite and fine-grained mixtures containing organic matter, among which tectonic and bedding fractures are less filled, and stylolites are easier to be filled. Microscopic tectonic fractures have smaller apertures, while diagenetic fractures usually have larger apertures. This study speculates that tectonic fractures mainly provide effective pathways for fluid flow in reservoirs, while bedding fractures are more developed, which are not only seepage channels for reservoir fluid but also an important part of the effective storage space. The research results provide an important reference for improving the classification scheme of natural fractures in deep continental shale and for better understanding of the natural fracture distribution in such reservoirs.