【作者】 高辉；

【导师】 孙卫；

【作者基本信息】 西北大学 ， 油气田地质与开发， 2009， 博士

【摘要】 特低渗透砂岩储层物性差、孔喉细小、孔隙结构非均质性强、微观渗流机理不同于常规储层,开展此项研究工作有助于对特低渗储层的微观孔隙结构进行系统认识,从本质上揭示影响特低渗储层微观渗流机理变化的关键因素。本文以高压压汞、恒速压汞、核磁共振、真实砂岩微观驱替、启动压力梯度测试和油水相渗实验结果等为基础,结合岩矿分析对鄂尔多斯盆地延长组长8、长6和长4+5储层的微观孔隙结构特征、油水微观驱替特征、微观渗流规律和油水相渗曲线特征进行了深入研究,主要取得如下认识:(1)特低渗透储层物性受孔隙、喉道特征影响较大,物性差异正是孔隙结构差异性的一种体现。喉道半径的多种分布形态对渗透率贡献值影响较大,孔隙结构的差异主要体现在喉道半径大小及分布上,特低渗透储层品质主要由喉道控制,渗透性主要由占少部分的较大喉道所贡献。4个研究区中,渗透率较大的样品其分选系数主要介于2.0～3.0之间,变异系数主要介于0.15～0.3之间。毛管压力曲线在进汞压力较小时主要受孔隙影响,当进汞压力增加到一定程度后,其变化趋势主要取决于喉道的变化。(2)孔隙结构均质系数(Ep)可较好地评价孔隙结构的非均质程度,4个研究区块的Ep平均值介于1.144～1.607之间,样品Ep分布曲线呈上翘、平缓、下凹的三段式。(3)可动流体百分数是特低渗储层微观特征的综合反映,研究区储层实验样品的可动流体百分数差异较大,主要分布于14.04%～72.15%之间,平均为47.38%,复杂、多变的微观孔隙结构是造成这一现象的主要原因。(4)油水微观驱替实验结果表明,研究区特低渗储层实验模型表现出6种主要驱替通道、4种主要驱替类型和3种主要残余油类型。微观孔隙结构和润湿性的非均质性是影响油水驱替特征与剩余油分布的主要原因。驱替压力只能在一定程度上提高驱油效率,注入倍数在1～2PV时对驱油效率的影响较大。可动油百分数是驱替效率的上限,驱替效率与可动油百分数之间的差距说明特低渗储层注水开发后的潜力仍然较大。(5)启动压力梯度是特低渗储层液体渗流的一种特殊表现,也是临界启动渗透率存在的根本原因,建立有效的驱替压力系统,降低临界启动渗透率,有助于改善开发效果。(6)特低渗透储层油水相渗曲线两相共渗区窄,实验样品两相共渗区平均值为28.56%,储层微观孔隙结构和润湿性的改变都会影响油水相渗曲线特征。更多还原

【Abstract】 Micro-flow mechanism of Ultra low permeability sandstone reservoir is different from traditional reservoir because of the poor physical property, fine pore throat and strong pore structure heterogeneity. Micro-pore structure is understood by the numbers and key elements which affect on Micro-flow mechanism are revealed essentially through this study, micro-pore structure characteristics, oil/water micro-displacement characteristics, micro-flow rule and oil/water relative permeability curve characteristics of Chang8, Chang6, Chang4+5 reservoir in Yanchang Formation of Ordos Basin are studied in depth based on the results of high pressure mercury penetration, constant speed mercury penetration, NMR, true sandstone micro-displacement, kickoff pressure gradient test, oil/water relative permeability test and geoanalysis In this dissertation. The main conclusions are as follows:(1) Physical property of ultra low permeability reservoir is influenced by pore and throat attributes. Physical property difference is the reflection of pore structure difference. Contribution value of permeability is affected by the manifold distribution of throat radius, pore structure difference is reflected in the size and distribution of throat radius. Quality of ultra low permeability reservoir is controlled by throat, permeability is contributed by little portion greater throat. In four studied areas, the permeability of samples is higher when the separation factor value distribute within 2.0~3.0 and the variation coefficient value distribute within 0.15～0.3. Capillary pressure curve is mainly influenced by pore in the low input mercury pressure. Variation tendency of capillary pressure curve mainly depends on throat alteration when the input mercury pressure increases to certain extent.(2) Pore structure uniformity coefficient (Ep) can evaluate pore structure inhomogeneous degree preferably. Ep average values of four areas distribute within 1.144～1.607. Distribution curves of Ep present upwarp, smooth and ward triple section.(3) Mobile fluid percent is the comprehensive reflection of micro-attributes of ultra low permeability. Difference of mobile fluid percent of laboratory sample is greater in studied areas for the complex and versatile micro-pore structure. The mobile fluid percent mainly spread within 14.04%～72.15%, average value is 47.38%.(4) The results of oil/water micro-displacement experiment show that experimental models of studied areas display six kinds of displacement passageways, four kinds of displacement types and three kinds of irreducible oil modes. Heterogeneity of micro-pore structure and wettability are the main reasons that affect the oil/water displacement attribute and remaining oil distribution. Displacement pressure only can improve the displacement efficiency to some extent. Inject multiple from 1PV to 2PV impact on displacement efficiency greater. Difference between displacement efficiency and Mobile oil percent which is the upper limit of displacement efficiency indicates the greater potential after waterflood development of ultra low permeability reservoir.(5) Kickoff pressure gradient is the particular performance of fluid flow through porous medium in ultra low permeability reservoir, also is the essential reason why the critical threshold permeability exists. Displacement pressure system established to decrease the critical threshold permeability can contribute to improve development effect.(6) Two-phase flow range of oil/water relative permeability curves is narrow in ultra low permeability reservoir and average value of laboratory sample is 28.56%. Alteration of micro-pore structure and wettability of reservoir can create influences on attribute of relative permeability curve.更多还原