【作者】 王瑞飞；

【导师】 孙卫；

【作者基本信息】 西北大学 ， 矿产普查与勘探， 2007， 博士

【摘要】 本文通过高压压汞技术、恒速压汞技术、核磁共振技术、X-CT成像技术、环境电镜扫描技术、铸体技术、水驱油实验及岩矿分析等对鄂尔多斯盆地延长组几个有代表性的低渗储层区块进行研究，旨在探讨低渗砂岩储层的微观孔隙结构特征、微裂缝特征、微观水驱油驱替特征及低渗储层物性演化过程，从而取得以下认识：(1)影响低渗砂岩储层物性的因素复杂，孔隙喉道类型多样是储层渗透性差的主要原因。过高或过低的孔喉分选系数都不利于储层渗流。储层性质主要由喉道控制。(2)低渗储层可动流体饱和度、可动流体孔隙度、原始含油饱和度、可动油饱和度、可动油百分数、驱油效率等参数低且非均质性强。渗透率越低，上述各参数随渗透率的降低衰减越快。微观孔隙结构是影响储层可动流体量、原始含油量、可动油量、驱油效率的主要因素。中、高渗透储层研究中一些可以忽略的因素在低渗透储层研究中不能忽略。(3)储层微裂缝分布具有条带性的特点，微裂缝主体方向与构造裂缝方向基本相同。微裂缝参数的定量研究表明微裂缝是改善低渗储层渗透性的重要因素。微裂缝分布的差异性和不均一性是造成低渗致密油气储层中有相对高渗储层的主要原因。(4)低渗透砂岩油田开发中，贾敏效应强、应力敏感性强、储层敏感性伤害程度大、自吸水驱油强度大、孔喉网络中小孔喉比例高。减弱贾敏效应是其高效开发的有效途径；以接近于自吸速度的水驱油速度会取得较好的开发效果。(5)受沉积和成岩的控制，物性好的储层粒间孔和次生溶孔的比重较大，物性差的储层次生溶孔和微孔的比重较大。薄片计点统计分析及孔隙度参数演化表明，沿25区块储层早期胶结作用和后期溶蚀作用强度大；庄40区块储层早期压实作用和后期溶蚀作用、交代作用强度大。孔隙度参数演化分析中影响误差的主要因素为分选系数(S_o)，各成岩作用阶段的相互重叠也是造成误差的一个重要原因。(6)胶结作用一定程度上提高了储层的抗压实能力，也为后期的次生溶蚀作用提供物质基础，但胶结物的产生也占据了一定的孔隙空间。统计储层成岩过程中形成的胶结物时，还应加入形成次生孔隙溶蚀掉的那部分胶结物。(7)成岩作用是沿25和庄40区块储层物性演化的最主要控制因素，储层类型为次生低渗透储层(或成岩型低渗透储层)。沿25区块为压实-胶结型低渗透储层；庄40区块为压实-交代型低渗透储层。在构造格局和沉积环境的基础上，成岩作用及其差异性是控制储层性质变化的主要地质营力。不同储层岩石，因所处沉积微相带不同，其原岩结构和矿物组成不同，岩石孔隙结构也就有很大差别。不同的原岩结构和矿物组成，虽经历了相同的成岩史，但相同的成岩作用对孔隙改造程度可以很不相同，表现出不同特征的孔隙演化史，最终体现在储层孔隙结构及物性的差异。更多还原

【Abstract】 With the technique of High pressure Hg injection, of rate-controlled Hg penetration, of NMR, of X-CT scanned image, of ESEM, of blue epoxy resin-impregnated thin sections, of water driving experiment, of geoanalysis, the aim is focused on studying the properties of reservoir’s micropore structure, the characteristics of micro-fractures, the characteristics of microscopic water displacement, and the evolution of low-permeability sandstone reservoir’s quality in several representative areas in Yanchang Formation of Ordos Basin. The conclusions are in the following:(1)The factors that affect physical properties are complicated. The variety of pores and throats are the main reasons that the permeability is low. The sorting. coefficient of pore throat, whether it is high or low, is detrimental to the fluid flowing in the reservoir. The reservoir quality is controlled by the throats.(2)The parameters of mobile fluid saturation, of mobile fluid’s porosity, of initial oil saturation, of mobile oil saturation, of mobile oil’s percent, of oil-displacement efficiency are low and strongly heterogeneous. The lower the permeability is, the larger the attenuation rate of those parameters is. They are mainly affected by the reservoir’s micropore structure. Some neglected factors in medium-high permeability reservoir research must be emphasized in low permeability one.(3)The distribution of micro-fractures is flaser. The main direction of micro-fractures is the same as that of tectonic fractures. The quantitative research of micro-fracture’s parameters indicates that the micro-fracture is the main factor which improves low permeable reservoir’s permeability. The existence of relatively high permeability reservoir lies in the difference and heterogeneity of the distribution in low permeability reservoir.(4)Jamin effect, stress sensitivity, reservoir sensitivity damage, and spontaneous imbibition are strong, the proportion of thin pore-throat is higher in the development of low permeability oil fields. Lowing Jamin effect is an effective way to develop low permeability reservoir highly. If the velocity of water driving is near to that of spontaneous imbibition, the development efficiency will be high.(5)Controlled by sedimentation and diagenesis, the proportion of intergranular pore and of secondary dissolved pores are great in relatively good reservoirs. While the proportion of secondary dissolved pores and of micropores are high in relatively bad reservoirs. Statistical analysis in rock thin-section and the porosity evolution show that the cementation and dissolution are intensive in Yan 25 area, the compaction, dissolution and metasomatism are intensive in Zhuang 40 area. Sorting coefficient is the main factor affecting error, and the overlapping of the diagenetic stages is also one factor.(6)The cementation, in a sense, improves reservoir’s resistance to compacting, also provides the material foundation for secondary solution effect. However, the cement occupies some sandstone pores. When the cement is calculated, the dissolved cement should be included.(7)Diagenesis is the essential controlling factors of reservoir quality evolution, and the type is secondary low permeability reservoir(or low permeability reservoir of diagenesis) in Yan 25 and Zhuang 40 areas. There is the type of the compaction and cementation in Yan 25 area, the type of compaction and metasomatism in Zhuang 40 area. Based on the tectonics framework and sedimentary environments, the diagenesis and its differences are the essential geological agencies that control the reservoir quality. Because different reservoir rocks are in different sedimentary microfacies, their primary texture, mineral composition and rock pore structure are also different. Although different primary texture and mineral composition had experienced the same diagenetic histories, the same diagenesises function differently on pore evolution in different areas. Therefore, there are different porosity evolution histories, which are embodied the discrepancies of pore structures and reservoir properties.更多还原