塔里木盆地东南地区侏罗系低孔渗砂岩储层成岩作用及孔隙演化

Diagenesis and Pore Evolution of Jurassic Low-porosity and Low-permeability Sandstone Reservoir in Southeastern Tarim Basin

依据大量铸体薄片、扫描电镜、X射线衍射、物性分析、粒度分析、阴极发光、包裹体等分析化验资料，对塔里木盆地东南（简称为塔东南）地区侏罗系砂岩储层的成岩作用和孔隙演化进行系统研究。结果表明，塔东南地区侏罗系储层的岩石类型主要为长石岩屑砂岩、岩屑长石砂岩、岩屑砂岩，成分成熟度与结构成熟度均较低，为典型的低孔低渗储层。该砂岩储层经历了强烈的压实、胶结作用，是孔隙度降低的主要原因；后期的溶解及破裂作用总体较弱，但发育极为不均，局部发育层段对储层物性的改善贡献较大。储层目前已处于中成岩阶段A期。通过物性分析、薄片观察并结合相关理论公式进行定量分析，结果表明塔东南地区侏罗系砂岩原始孔隙度为28.5％～36.2％，压实作用损失了9.5％～17.0％的孔隙度，胶结作用损失了12.6％的孔隙度，溶解作用贡献了1.5％的孔隙度。在各种因素的共同作用下最终形成现今3％～14％、平均7.9％的孔隙度。

Based on bulk laboratory results of cast thin section,scanning electron microscope,X-ray diffrac-tion,physical property analysis,particle size analysis,cathodoluminescence,inclusions,the characteristics of diagenesis and pore evolution of Jurassic sandstone reservoir in southeastern Tarim Basin were systematically studied in this paper.The result shows that the rock type of Jurassic reservoir in southeastern Tarim Basin is mainly composed of feldspathic lithic sandstone,lithic arkose and lithic sandstone,with low compositional matu-rity and low textural maturity.It is a typical low-porosity and low-permeability reservoir.This sandstone reser-voir went through strong compaction and cementation,which are mainly responsible for losing porosity.The dis-solution and fissure are generally poor,but they are extremely uneven and generated a significant contribution to the improvement of reservoir properties in local development layers.The reservoir is now in the A period of mid-dle diagenesis stage.By using physical property analysis,cast thin section and related theories to make quanti-tative analysis,the result shows that initial porosity of Jurassic sandstone reservoir is 28.5% to 36.2% in southeastern Tarim Basin;9.5% to 17.0% of porosity is lost due to the early stage compaction;the cementa-tion causes 12.6%of porosity to loss;the dissolution adds 1.5% of porosity.Thus those various factors finally＆amp;nbsp;cause the current reservoir porosity to be 3% to 14% with average value of 7.9%.