【作者】 张创；

【导师】 孙卫；

【作者基本信息】 西北大学 ， 油气田地质与开发， 2013， 博士

【摘要】 本文以三类具有不同盆地地温背景、埋藏史条件与岩性特征的低渗砂岩储层为研究对象(苏北盆地沙埝地区古近系阜宁组阜三段储层、三塘湖盆地牛圈湖地区侏罗系西山窑组西二段储层与鄂尔多斯盆地延安地区二叠系石盒子组盒八段储层),应用铸体薄片、扫描电镜、液氮吸附法微孔测试、粒度分析、x衍射、阴极发光、电子探针、常规压汞、恒速压汞等技术与方法,分析、对比了低渗储层孔隙与喉道的分布特征。在筛选和建立较为准确的孔隙度演化计算方法的基础上,结合储层成岩作用进行了孔隙度演化史恢复。最后,分析了三类低渗储层孔隙度演化特征,对其影响因素进行了探讨。取得以下认识：(1)不同砂岩类型低渗储层均为各种成因的孔喉并存,孔隙、喉道半径分布范围也往往较大,但半径较大的孔隙与喉道分布频率低,通常是造成其低孔低渗的主要原因；是否含有相对粗大喉道及粗大喉道的半径与数量是渗透率的决定因素；微孔在低渗储层的孔隙中占据相当比例,且随储层物性变差,微孔占总孔隙度的比例显著提高：由于小于0.1μm的微孔仍是天然气的有效储集空间,因此,微孔是低渗-超低渗天然气储层孔隙的重要组成部分。(2)不同砂岩类型低渗储层初始孔隙度存在一定差别,但与储层现今物性面貌相比,初始孔隙度的差别相对较小：除部分早期碳酸盐胶结物发育的储层外,大部分储层的主要孔隙度损失由压实作用造成；不同砂岩类型的低渗储层均经受了不同强度溶蚀作用的改造,溶蚀强度由主要溶蚀期酸性介质的浓度及孔隙渗流能力所决定；胶结损失孔隙度存在较大差异,但除成岩早期形成的碳酸盐胶结物外,其余胶结物共同的作用均是充填孔隙、堵塞喉道,使储层致密化。(3)较高地温场、短深埋期、早期弱碱性成岩环境下的长石砂岩类储层,早期碳酸盐胶结物一般沉淀于压实快速减孔阶段,抑制压实的同时为后期溶蚀提供了物质基础；较高地温场下,有机质成熟形成的有机酸对碳酸盐胶结物与骨架颗粒的溶蚀形成了较为发育的扩大粒间孔；长石溶蚀产物就地沉淀形成的高岭石等粘土矿物沉淀于孔隙较为狭窄处或充填喉道,使储层在具有较高孔隙度的同时,渗透率却较低。(4)低地温场、中等深埋期、酸性成岩环境(煤系地层)的岩屑砂岩类储层,缺乏早期碳酸盐胶结物对骨架颗粒的支撑,塑性岩屑在压实过程中强烈变形,导致孔隙度随埋深增大迅速减小：低地温场下有机质程成熟度低,提供的有机酸有限,加之孔隙渗流条件较差,胶结作用和溶蚀作用均较弱。压实作用往往是造成此类储层低渗的主要原因。(5)中等地温场、长深埋期、酸性成岩环境下的石英砂岩类储层,压实快速减孔阶段形成的少量石英次生加大边抑制压实的效果非常有限；深埋期长时间较高的地温环境使骨架颗粒溶蚀产物沉淀为更为稳定的硅质胶结物和粘土矿物,造成粒间孔隙大量封闭的同时,又充填了部分溶孔。在压实损失孔隙度较大的情况下,长时间较高地温条件下石英次生加大的普遍发育与粘土矿物和含铁碳酸盐的充填,往往造成此类储层为超低渗储层。更多还原

【Abstract】 Taking three low-permeability reservoirs with different palaeogeothermal background, burial history and different sandstone classifications as the research object, which is Funing formation of Early Paleogene in Shanian, North Jiangsu basin, Xishanyao formation of Middle Jurassic in Niujuanhu, Santanghu basin, and Shihezi formation of Middle Permian in Yan’an, Erdos basin, with the technique of casting sections, staining, scanning electron microscopy, liquid nitrogen adsorption method micropore testing, grain size analysis, X-diffraction, electron microprobe analysis, energy dispersive analysis, mercury penetration and rate-controlled mercury penetration, the microscopic pore structure of low-permeability sandstone reservoirs is studied. Base on the accurace method of model analysis, the porosity evolution pathways of the three low-permeability reservoirs are studied, and their influential factors are analysed.The conclusions are in following:(1) There are pores and pore-throats of various genetic types in s low-permeability reservoirs with different sandstone classifications, and their radius changes in a large scale. The quantities of relatively large pore-throats are usually small, which is the main reason for their low-permeability. The results of rate-controlled mercury penetration show, the permeability of sandstone reservoirs is mainly controlled by the quantity and radius of relatively large pore-throats. The micropores occupy a considerable proportion of porosity in low-permeability reservoirs, and their proportions are obviously mproving with reservoir physical property being worse. As a sort of effective accumulating space of natural gas, micropores are important part of porosity in ultra low-permeability natural gas reservoirs.(2) There are some differences of original porosity in different sandstone reservoirs, which are lower than today. The major porosity losses of most reservoirs are caused by compaction, except those being cemented by carbonate in early phase. Different sandstone reservoirs suffered dissolution more or less, which is controlled by organic acid concentration and filtrate capability of pore network. There are great differences of cementational porosity losses in sandstone reservoirs, all cement will fill pores and block pore-throat to make reservoirs densifying, except carbonate cement in early phase.(3) The reservoir of arkose sandstone with the relatively high palaeogeothermal, short period of large buried-depth, week-alkaline environment in early diagenetic phase, is offen cemented by carbonate in the smaller depth, where the porosity declined sharply with depth. The carbonate cementation can retard compation, and provides dissolution mass. In the relatively high palaeogeothermal condition, organic acid supplying by organic maturation dissolved carbonate and framework grains, and formed substantial secondary porosity. The products of dissolution of aluminum-silicate framework grains, are precipitated in the pore network as an authigenic kaolinite, what results in a significant decrease in permeability of reservoir.(4) The reservoir of lithic sandstone with relatively low palaeogeothermal, moderate period of large buried-depth, acidic diagenetic environment (coal measure strata) in early diagenetic phase, is offen free of carbonate cements. The ductile lithic strongly deformed in compacting process, and the porosity decreased sharply with depth.In the relatively low palaeogeothermal condition, organic acid supplying by organic maturation is limited, the dissolution and cementation are both relatively week in the more closed pore network caused by intensive compaction.(5) The reservoir of quartzose sandstone with moderate palaeogeothermal, long period of large buried-depth, because of the late time of quartz overgrowth formation, porosity decreased sharply with depth. The quartz and authigenic clay mineral are precipitated from the dissolution mass of framework grains, which makes intergranular pores consuming drasticly, and filled part of secondary porosity. In the condition of substantial porosity loss in compacting process, the quartz overgrowth and clay mineral filled primary and secondary porosity severely, what makes the reservoir be ultra-low-permeability usually.更多还原