【作者】 高潮；

【导师】 王震亮；

【作者基本信息】 西北大学 ， 矿产普查与勘探， 2011， 博士

【摘要】 低渗透储层在全国的油气勘探和开发中的地位非常重要。由于沉积、成岩相带变化快,非均质性强,形成以低孔、低渗、低含油饱和度、油层规模小、油水分异程度低为主要特点的低渗油藏。因此,分析、评价低渗透储层的形成、演化及其对油藏分布的影响,具有重要理论意义和较大实用价值。位于鄂尔多斯盆地陕北斜坡西部的张天渠-韩渠油田,在延长组长2段主要发育低渗透砂岩储层,是进行低渗储层成因及对油水分布影响研究的理想地区,本文以该地区作为重点解剖对象,以低渗储集体宏观分布及其内部组成精细刻画为基础,从宏观和微观角度分析低渗透储集体演化与油藏分布特点。研究中以岩心观察为基础,综合利用测井、试油、试采等原始资料和储量计算结果,研究低渗透储集体宏观几何形态(平面和垂向)对油藏分布的影响；利用薄片观察、扫描电镜、图像分析、压汞分析等测试方法与资料,研究低渗储集体物性及其演化对油藏分布的影响；结合油藏油水性质变化的研究,重点分析低渗油藏形成的主控因素,在上述研究的基础上,总结低渗透储集体成因对油藏分布规律的影响。研究分析表明：(1)低渗透储集体具有独特的油藏地质特征,低渗油藏物性致密,其中多发育2-5m的油水同层,纯油层几乎不发育,油藏类型和分布受控沉积相和成岩作用的综合影响,油藏内易出现油水倒置的油水分布特征；(2)低渗储集体为不同时期的条带状和椭圆状砂体单元呈多边式和垂积式叠加形成具有一定连通性和连续性的砂岩连通体,其内部空间受隔夹层分割影响,平面和层间非均质性较强；(3)张-韩地区低渗砂岩,较之常规砂岩具有粒度细结构成熟度低、成分成熟度低的特点,是低渗砂岩致密的物质基础,在初始沉积环境和后期演化过程中均不利于孔隙的形成和保存。(4)低渗储集体储集空间以次生溶蚀孔隙为主,发育溶蚀-残余孔隙型和溶蚀-微孔隙型等2种组合类型；受微观非均质性的影响,孔隙度为正态分布,渗透率呈非正态的对数分布,随着渗透率的降低,其与孔隙度的相关性越差；(5)张-韩地区低渗砂岩成岩程度较强,成岩事件类型复杂,压实作用是物性降低的主要因素,胶结作用是次要因素,后期的溶解作用对物性的改善程度较大。砂岩在经历了不同的成岩演化过程后最终形成四类不同物性特征的成岩相砂体,其中多数属于特低—超低渗级别。(6)低渗储层背景下,微构造和较强的层内非均质性是低渗油藏的形成主要宏观因素；较高的束缚水饱和度(20%-40%以上),厚度较大的油水过渡带,渗透率的方向性是造成低渗油藏油水分布复杂的的微观因素。更多还原

【Abstract】 Lowly permeability sandstone reservoirs play a significant part on Chinese hydrocarbon exploration and development activity.Owing to quickly change of the sedimentary and diagenetic facies,strong heterogeneity, the lowly permeability reservoirs characteristiced by lowly porosity, lowly permeability, low oil saturation, small reservoir thickness, bad separation of oil and water. Thus, it has important theoretical and more practical value in analyzing and evaluating the origin and evolution of low permeability sandstone reservoir and its influence on oilfield distribution. Lowly permeability sandstone reservoirs where developed in Chang 2 division of Zhang-han oilfield is the ideal study area for research on origin of lowly permeability sandstone reservoir and its influence on oil and water distribution. The region was taken as the key object to analyse in this paper, the origin and evolution of low permeability reservoir and oilfield distribution were researched from the macroscopic and microcosmic perspective based on refined description of its macroeconomic distribution and microscopic composition. All research based on the core observation, and the influence of lowly permeability reservoir macro geometric shape (plane and vertical) on the oilfield distribution was researched by the comprehensive utilization of logging, well testing, producing test and the reserves calculation. The affect of physical property and its evolution to oilfield distribution was researched by micro-pore structure analysis, cast thin section observation, scanning electron microscopy and other test method and material. The key factors that control the distribution of oilfield were emphatically analyzed combing the research of oil-water propertie variation in low permeability reservoirs, finally, the law of oilfield distribution that influenced by the origin and evolution of lowly permeability sandstone reservoir bed was summarized on the basis of the study.The result of research show that:(1) Lowly permeability reservoir characteristic with special geological reservoir features, as almost no oil layer developed in poor physical properties and lowly permeability sandstone reservoir, and the thickness of oil-water layer mainly distribute from 2 to 5 m,the types of reservoir be controlled by synthesis influence of sedimentary facies and diagenesis, It’s easier to occur the oil/water inversion within the reservoir; (2) Lowly permeability sandstone reservoirs is connected and outspread sandstone bed that be composed of multilateral and vertical superposition of a ribbon and elliptic sand body unit at different phases. And its plane and interlayer heterogeneity are stronger owing to the division of isolated layer; (3) The lowly permeability sandstone of Zhang-han oilfield characteristic with finer grain size, lower mineral and compositional maturity compare to convention sandstone, is the material base of the compacted lowly permeability sandstone, and go against the formation and preservation of the pore through the initial sedimentary environment to later evolution; (4) The secondary dissolved pores is the main pore spaces in lowly permeability reservoir, and combined with residual intergranular pores and micro-porosity formed two kinds of pore compile including dissolved-residual pore type and dissolved-micropore type. Influenced by microscopic heterogeneity, the porosity is in normal distribution, and the permeability is in non-normal and logarithm distribution. And the lower permeability value is, the correlation between porosity and permeability is poorer; (5) The diagenesis degree is strong in lowly permeability sandstone of Zhang-han oilfield, the types of diagenesis is various, compaction is the main factor that reduced the reservoir quality of the sandstones.cementation is less important factor, dissolution contributes more to physical property,In four diagenetic facies formed in sandstone pass through different diagenesis, predominant sandstones with these diagenetic facies are belong to level of ultra-lowly permeability; (6) Micro structure and strong inner heterogeneity are main macroscopical factors that contribute to the formation of lowly permeability reservoirs under the background of low permeability; Higher bound water saturation (20% to 40%), larger thickness of oil-water transitional zone, directional permeability are microscopic factors that perplex the distribution of oil and water within Low-permeability reservoir.更多还原