辽河坳陷沙三、沙四段泥页岩微观孔隙特征及其成藏意义

摘要

为深入研究辽河坳陷次级凹陷沙河街组三、四段泥页岩储层孔隙特征及成藏意义，选取了5口泥页岩钻井岩心样品进行了氩离子抛光-扫描电镜（ FIB-SEM）、氦气吸脱附、X-衍射全岩分析、干酪根镜检及配套有机地化等实验，从微观孔隙结构到成藏意义进行了深入探讨。结果表明，研究层段共存在粒间孔、粒内孔、晶间孔、溶蚀孔、有机孔、微裂缝6种孔隙类型。孔隙发育不仅与沉积压实、胶结、溶解作用相关，另外还与页岩岩性、矿物组构、有机质类型、有机地化等因素密切相关。粘土矿物集合体粒间孔和层间微孔缝对页岩油气的赋存和运移贡献最大，且是页岩储层各向异性（渗透率）的主要控制因素；溶蚀孔及晶间孔次之；有机孔因相对不发育，对页岩油气的渗透贡献较小，但仍然是吸附态页岩油气的主要场所；微裂缝的影响不容忽视，是沟通宏孔与中孔的主要微通道。另外，低熟条件下粘附-结合态有机质中有机孔的大量发现表明粘土矿物对有机质的早期催化生烃起到重要作用，同时，有机质与矿物（主要是粘土矿物）紧密共生的保存特点，也反映了有机质保存形式与油气生成之间的密切关系。实验同时表明无定形体是研究层段生成页岩油气的主要贡献者。%In order to further study the pore characteristics of shale reservoir oin Sha-3 and Sha-4(the 3rd and 4th Member of Shahejie Formation respectively ) and their accumulation significance in Liaohe depression ,samples from 5 wells were chosen to conduct a series of experiments including focused ion beam-scanning electron microscope(FIB-SEM),helium adsorption and desorption ,whole rock analysis by XRD ,microscopic examination of kerogen and related organic geochem-istry experiments.The results show that there are 6 types of pore including intergranular pore ,intragranular pore ,inter-crystal pore,dissolution pore,organic pore and micro-cracks.Furthermore,development of these pores are not only related to sedimentary compaction , cementation and dissolution , but also closely related to the lithology , mineral fabric , type of organic matter and organic geochemistry .The intergranular pores and interlayer micropores and cracks of clay mineral ag-gregates make the greatest contribution to the storage and migration of shale oil and gas ,and they are also the major con-trolling factor of the anisotropic ( permeability ) of the shale reservoir , followed by the dissolution pores and inter-crystal pores.The organic pores contribute the least due to the relatively poor development ,but they still plays an important role in storage of absorbed shale oil and gas .Meanwhile , micro-cracks are also negligible in connecting macro-pores and me-so-pores.In addition ,large amount of organic pores are found in adhesive-combining organic matter with low maturity ,in-dicating that clay minerals play an important role in the early period of hydrocarbon generation .The feature of close sym-biosis between organic matter and minerals ( mainly clay minerals ) also reflects the close relationship between the preser-vation pattern of organic matter and hydrocarbon generation .The experiments also demonstrate that the amorphous solid is the major contributor to the generation of shale oil and gas in Sha-3 and Sha-4 shale .