陆相页岩储层孔隙结构演化特征及其控制因素

发布时间：2018-12-07 12:17

【摘要】：陆相页岩气资源占到页岩气总资源的三分之一,但陆相页岩气勘探突破不大,制约页岩含气性的储层孔隙结构研究还非常薄弱。论文以鄂尔多斯盆地三叠系延长组和柴达木盆地中侏罗统大煤沟组陆相页岩为研究对象,针对未经抽提等处理的原始页岩样品,利用TOC分析、岩石热解、X-射线衍射、场发射扫描电镜、低压CO2/N2吸附、高压压汞等技术,开展陆相页岩储层特征、孔隙结构特征、孔隙结构演化以及控制因素的研究。结果表明,研究区陆相页岩具有“两高两低多种类型”的特点:即有机碳含量和黏土矿物含量高,热演化程度和脆性矿物含量低;有机质类型多,以偏腐殖混合型为主。主要岩相类型包括黏土质页岩、硅质页岩和混合页岩,其中硅质页岩纹层最发育,黏土质页岩和混合页岩TOC含量较高。扫描电镜揭示研究区陆相页岩孔隙类型主要为粒间孔、粒内孔和有机质孔隙,与海相页岩相比,陆相页岩粒间孔隙直径较大(可达微米级),而粒内孔隙直径较小(几十到几百纳米),有机质孔隙发育相对较少且孔径和分布不均匀。陆相黏土质页岩孔隙孔径整体偏小,孔隙连通性整体较好,具有平行壁的狭缝状孔隙和墨水瓶型孔隙相对发育;混合页岩孔隙孔径整体偏大,孔隙连通性较差,楔形狭缝状孔隙相对较发育,墨水瓶型孔隙发育较少。随成熟度增加,黏土质页岩单位TOC孔体积呈减小趋势,混合页岩整体呈先减小后增大的趋势,微孔体积呈减小的演化趋势。两类岩相页岩中孔体积占总孔体积的比例高,微孔和中孔提供主要的比表面积。随演化程度增加,黏土质页岩2~10nm的中孔占总孔体积和总比表面积的比例降低,混合页岩2~10nm的中孔占总孔体积和总比表面积的比例增加。未熟油气的生成以及有机酸溶蚀促进了页岩孔隙的发育,液态烃充填和页岩储层的埋深压实导致页岩有效孔隙的减少。生油窗阶段孔隙的数量和孔径都快速变化,液态烃的大量生成和残留堵塞孔隙,残留烃主要赋存于0.3~0.6nm的微孔以及2~20nm的中孔之中,残留烃的存在对于陆相页岩储层孔隙结构的表征以及含气性的分析均有影响。凝析气阶段有机质孔隙随着烃类的排出和裂解而增多,被残留液态烃堵塞的孔隙开启,同时页岩储层内部压力下降,压实作用增强。除此之外,有机质孔隙的发育还与有机质的赋存状态有关,黏土矿物和黄铁矿的催化生烃作用导致分散伴生态有机质中孔隙的孔径小于富集态有机质,较富集态有机质孔隙更加发育。
[Abstract]:The terrestrial shale gas resources account for 1/3 of the total shale gas resources, but the exploration breakthrough of the terrestrial shale gas is not large, and the pore structure of the reservoir which restricts the shale gas content is still very weak. In this paper, the continental shale of the Triassic Yanchang formation of the Ordos Basin and the Dawagou formation of the Middle Jurassic in the Qaidam Basin are taken as the research objects. The original shale samples, which have not been extracted and treated, are analyzed by TOC, pyrolysis of rocks, and X-ray diffraction. Field emission scanning electron microscopy (SEM), low pressure CO2/N2 adsorption, high pressure mercury injection and other techniques are used to study the reservoir characteristics, pore structure evolution and controlling factors of terrestrial shale. The results show that the continental shale has the characteristics of "two high and two low types": high organic carbon content and clay mineral content, low thermal evolution degree and brittle mineral content, and a large number of organic matter types, mainly partial humic mixed type. The main lithofacies types include clay shale, siliceous shale and mixed shale, in which siliceous shale has the most developed grain layer, and the TOC content of clay shale and mixed shale is high. Scanning electron microscope revealed that the pore types of continental shale in the study area are mainly intergranular pore, intragranular pore and organic pore. Compared with marine shale, the intergranular pore diameter of continental shale is larger (up to micron size). However, the pore diameter is small (tens to hundreds of nanometers), and the pore size and distribution of organic matter are not uniform. The pore size of continental clay shale is relatively small, the pore connectivity is good, and the slit pores with parallel walls and the ink bottle pores are relatively developed. The pore size of mixed shale is relatively large, the pore connectivity is poor, the wedge-shaped slit pore is relatively developed, and the ink bottle pore is less developed. With the increase of maturity, the unit TOC pore volume of clay shale decreases, the whole mixed shale decreases and then increases, and the micropore volume decreases. The ratio of pore volume to total pore volume of two types of lithofacies shale is high, and micropore and mesopore provide the main specific surface area. The ratio of mesopore to total pore volume and total specific surface area of clay shale 2~10nm decreased with the increase of evolution degree, while the proportion of 2~10nm medium pore to total pore volume and total specific surface area of mixed shale increased. The formation of immature oil and gas and the dissolution of organic acids promote the development of shale pores. The filling of liquid hydrocarbon and the deep compaction of shale reservoirs result in the decrease of effective pores of shale. The number and pore size of pores change rapidly in the window stage of oil generation. The formation of liquid hydrocarbons and the residual plugging of pores occur mainly in the micropores of 0.3~0.6nm and the mesoporous pores of 2~20nm. The existence of residual hydrocarbon has influence on pore structure characterization and gas bearing analysis of continental shale reservoir. At the stage of condensate gas, the pores of organic matter increase with the expulsion and cracking of hydrocarbons, and the pores blocked by residual liquid hydrocarbon open, and the internal pressure of shale reservoir decreases and the compaction increases. In addition, the development of organic pores is related to the occurrence of organic matter. The pore size of pores in organic matter is smaller than that of enriched organic matter due to the catalytic hydrocarbon generation of clay and pyrite. The porosity of organic matter is more developed than that of enriched organic matter.
【学位授予单位】：中国石油大学(北京)
【学位级别】：博士
【学位授予年份】：2016
【分类号】：P618.13

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