鄂尔多斯盆地三叠系延长组富有机质页岩孔隙特征及发育机制

发布时间：2018-04-05 07:50

本文选题：矿物基质孔　切入点：有机质孔　出处：《天然气地球科学》2016年07期

【摘要】：页岩储层孔隙发育特征是页岩储层评价的重要内容,也是开展页岩油气赋存机理研究的基础。提出了通过"基质类型—孔隙产状—孔隙成因"划分孔隙类型的方案。利用氩离子抛光和场发射扫描电镜技术观察孔隙发育情况,根据基质类型和孔隙产状,识别了4类孔隙:粒间孔、粒内孔、有机质孔和微裂缝,并根据孔隙成因将粒间孔分为碎屑颗粒间原生孔、黏土矿物片体间孔和颗粒间溶蚀孔,将粒内孔分为长石颗粒内溶蚀孔、黏土矿物片体内孔和黄铁矿晶体间孔。有机质孔主要为有机质颗粒内的微裂缝和有机质内孤立分布的孔径较小的孔隙。微裂缝主要表现为纹层缝或页理缝。综合孔隙图像分析、低温液氮吸附实验结果、孔隙结构参数与矿物组成、有机碳含量和有机质成熟度等参数相关性分析,认为沉积条件、成岩作用和有机质热演化控制了孔隙的形成和保存。半深湖—深湖沉积环境下,富有机质页岩中发育重力流成因的薄层砂质纹层,纹层段碎屑颗粒含量高,有利于形成碎屑颗粒粒间孔、碎屑颗粒粒内孔和顺层微裂缝。早期成岩作用阶段形成黄铁矿,有利于形成黄铁矿晶间孔,但黄铁矿也是压实作用的主要参与者;压实作用造成粒间孔和粒内孔的孔径变小和孔体积降低,碎屑颗粒和黄铁矿与有机质颗粒间呈凹凸接触,有机质孔在压实作用下闭合导致有机质孔不发育;溶蚀作用促进长石粒间溶孔和长石粒内溶孔的形成,一定程度改善储层质量。在成熟度达到一定阶段(RO≈0.75%)后,开始出现有机质孔。有机质孔发育程度差,一方面受成熟度的影响,另一方面可能是压实作用造成的。此外,富有机质泥页岩渗透性较差,烃类被吸附在有机质表面或溶于干酪根内部,造成干酪根体积膨胀也可能是有机质孔不发育的一种原因。
[Abstract]:The pore development feature of shale reservoir is an important part of shale reservoir evaluation, and is also the basis of the research on shale oil and gas occurrence mechanism.The method of dividing pore type by matrix type, pore occurrence and pore genesis is put forward.The development of pores was observed by argon ion polishing and field emission scanning electron microscopy. According to the matrix type and pore pattern, four types of pores were identified: intergranular pore, intragranular pore, organic pore and microfracture.According to the origin of pores, intergranular pores are divided into primary pores between clastic grains, intergranular pores and intergranular dissolution pores of clay minerals, and internal pores are divided into inner dissolution pores of feldspar particles, internal pores of clay minerals and intercrystalline pores of pyrite.The organic pores are mainly micro-fractures in organic matter particles and pores with small pore size in isolated distribution of organic matter.The microcracks are mainly shown as striated seam or laminated seam.Comprehensive pore image analysis, low temperature liquid nitrogen adsorption experiment results, pore structure parameters and mineral composition, organic carbon content and organic matter maturity and other parameters correlation analysis, the deposition conditions,Diagenesis and thermal evolution of organic matter control the formation and preservation of pores.In semi-deep lacustry-deep lacustrine sedimentary environment, there are thin layers of gravimetric flow in shale rich in organic matter, with high clastic grain content, which is conducive to the formation of intergranular pores, intergranular pores and microfractures in the clastic grains.The formation of pyrite in the early diagenesis stage is beneficial to the formation of intergranular pyrite pores, but pyrite is also the main participant in compaction. Compaction results in the reduction of pore size and volume of intergranular and intragranular pores.Clastic particles, pyrite and organic matter particles are in concave and convex contact, organic pore is closed under compaction, and dissolution promotes the formation of intergranular dissolution pore and dissolution pore in feldspar, and improves reservoir quality to a certain extent.When the maturity reaches a certain stage, the organic matter pores begin to appear.The porosity of organic matter is poor, which is influenced by maturity on the one hand, and compaction on the other.In addition, the permeability of organic-rich shale is poor, and hydrocarbons are adsorbed on the surface of organic matter or dissolved in the interior of kerogen. The volume expansion of kerogen may also be one of the reasons for the undeveloped pore of organic matter.
【作者单位】：西安石油大学地球科学与工程学院;陕西省油气成藏地质学重点实验室;中国石油大港油田分公司第二采油厂;中国石油集团测井有限公司;
【基金】：陕西省自然科学基金项目(编号:2013JQ503) 陕西省教育厅重点科研项目(编号:15JS092) 国家科技重大专项(编号:2011ZX5018001)联合资助
【分类号】：P618.13

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