摘要
随着我国对非常规油气勘探理论的完善和技术的提高,页岩油气勘探开发不断获得突破,其战略地位也在不断上升。页岩储层的品质通常是制约其资源潜力的主要因素,其中裂缝是页岩油气富集、高产、稳产的关键。因此裂缝作为富有机质页岩储层重要的储集空间和渗流通道,其相关研究一直都是该领域内的重点。我国页岩储层内天然裂缝大量发育,而非构造裂缝同样比较发育,对页岩油气的富集和保存评价亦具有重要意义。目前对页岩储层构造裂缝的研究比较深入,而对页岩非构造裂缝的研究则相对薄弱。为此本文在充分调研近年来国内外页岩非构造裂缝研究成果的基础上,重点梳理了非构造裂缝的分类、识别与表征、主控因素、期次及演化序列等方面的研究进展。页岩储层非构造裂缝以成因和形态复杂、分布不规则、尺度较小为特征,依据成因机制差异可将其分为成岩缝、异常高压缝、层理缝和表生缝4个大类,它们的识别与表征目前主要还停留在定性描述的阶段;尽管不同类型的非构造缝主控因素存在差异,但均在不同程度上受控于沉积作用、成岩作用、矿物组分及含量、岩石力学性质,呈现出一定的共性。综合分析并指出了页岩储层非构造裂缝研究的关键问题及发展趋势:一是基于页岩储层岩心、薄片、成像测井、常规测井的典型特征,结合先进图像技术,建立不同类型不同尺度非构造裂缝综合有效识别与定量化表征新方法。二是针对页岩储层非构造裂缝的形成发育具有“多成因类型、多控制因素、多期次演化”的特点,并且页岩非构造裂缝的形成与演化与“古温压、古流体、古成岩”过程联系紧密。据此提出了利用页岩储层非构造裂缝中普遍存在的方解石等充填物的流体地球化学、同位素地球化学(C,O,Sr)及微区原位同位素年代学(U-Pb,Sm-Nd)等先进实验分析技术,综合确定页岩储层非构造裂缝形成时间和活动期次及演化序列是未来研究的关键手段。三是由页岩储层非构造裂缝发育程度与单因素主控因素之间的定性-半定量分析,向多个主控因素耦合控制下的非构造裂缝发育程度的定量研究方向发展,即采用数学方法确定不同主控因素对于裂缝发育程度影响的权重,并构建适合我国页岩非构造裂缝发育程度的综合指数与多个主控因素之间的定量关系模型。
Shale oil and gas exploration and development in China has become increasingly important strategically,as breakthroughs are continually to be made with the improvement of unconventional oil and gas exploration theory and technology.The resource potential of shale reservoirs is largely constrained by reservoir quality,where fracture development is key to oil/gas enrichment and reservoir productivity.Fractures have always been a research focus of organic-rich shale oil and gas reservoirs as they play an important role in petroleum storage space and seepage channels.Shale reservoirs in China are naturally fractured in general and have relatively wide distribution of non-tectonic fractures.Presently,tectonic fractures have been studied more in depth.This paper,therefore,focuses on non-tectonic fractures with comprehensive review of recent domestic and foreign research achievements,focusing on fracture classification,identification and characterization as well as fracture controlling factors,stages and evolutionary sequences.Non-tectonic fractures are characterized by complex formation mechanism and morphology,irregular distribution pattern and small scale.According to their formation mechanism,non-tectonic fractures can be divided into four categories:diagenetic fractures,abnormal high-pressure fractures,bedding fractures and supergene fractures;whereas fracture identification and characterization are still largely based on descriptive analysis.Although the main fracture controlling factors differ between different fracture types,they share certain commonalities as all fractures are controlled,to some degrees,by sedimentation,diagenesis,mineral composition/content and rock mechanical properties.This paper further analyzes the key research challenges and points out key development trends in the field.First,a novel method should be developed to perform comprehensive and effective identification and quantitative characterization of non-tectonic fractures of different types and scales,based on typical characteristics of shale reservoir core,thin section,imaging logging and conventional logging,combined with advanced image technology.Second,as non-tectonic fractures exhibit“multi-genetic type,multi-control factor,multi-stage evolution”characteristics,with paleotemperature/paleopressure,paleofluids and paleodiagenesis playing a key role in their generation and evolution,advanced experimental analysis techniques,such as fluid geochemistry,isotope geochemistry(C,O,Sr)and in situ isotope chronology(U-Pb,Sm-Nd)of common filling materials such as calcite should be the key techniques to determine their formation time,active stages and evolutionary sequence.Last,the future trend is a shift from qualitative/semi-quantitative analyses of fracture development under a single controlling factor to quantitative,multi-factor coupling analysis.That is,using mathematical methods to determine the weights of different controlling factors and construct a quantitative relationship model to quantify the relationship between a comprehensive fracture development index and multiple controlling factors.
作者
丁文龙
王垚
王生晖
刘霆锋
张子游
勾通
张梦阳
贺湘
DING Wenlong;WANG Yao;WANG Shenghui;LIU Tingfeng;ZHANG Ziyou;GOU Tong;ZHANG Mengyang;HE Xiang(School of Energy Resources,China University of Geosciences(Beijing),Beijing 100083,China;MOE Key Laboratory for Marine Reservoir Evolution and Hydrocarbon Abundance Mechanism,China University of Geosciences(Beijing),Beijing 100083,China;MNR Key Laboratory of Strategy Evaluation for Shale Gas,China University of Geosciences(Beijing),Beijing 100083,China)
出处
《地学前缘》
EI
CAS
CSCD
北大核心
2024年第1期297-314,共18页
Earth Science Frontiers
基金
国家自然科学基金面上项目(42072173,42372171)。
关键词
页岩油气
非构造裂缝
裂缝分类
主控因素
裂缝发育程度
裂缝期次
shale oil and gas
non-tectonic fracture
fracture classification
main control factor
fracture development degree
fracture formation period
