鄂尔多斯盆地上三叠统延长组机械压实作用与砂岩致密过程及对致密化影响程度  

The Relationship between the Mechanical Compaction and the Densification Process of Sandstones and the Affect Degree of Compaction to the Densifying of Yanchang Formation,Ordos Basin

作　　者：刘明洁[1] 刘震[1] 刘静静[1] 蔡长娥[1] 张胜斌[1] 

机构地区：[1]中国石油大学油气资源与探测国家重点实验室,北京102249

出　　处：《地质论评》2014年第3期655-665,共11页Geological Review

基　　金：中石油"十二五"科技重大专项"岩性油气藏成藏动力;临界条件与分布模式"(编号2011ZX05001-001-04);中石化"十二五"科技重大专项"鄂尔多斯盆地油气成藏主控因素与富集规律"(编号2011ZX05002-006-009HZ)的成果

摘　　要：近年来,随着致密砂岩油气藏研究的不断深入,亟需明确致密砂岩储层致密化机理,从而更好地利于致密砂岩油气藏的勘探与开发。机械压实作用通常被理解为中浅层砂岩所经历的主要成岩作用,而深层的机械压实作用长期以来被人们所忽视。为探讨机械压实作用在砂岩致密过程中的作用及对致密化的影响程度,本次研究以鄂尔多斯盆地上三叠统延长组致密砂岩为例,通过井孔浅层与深层孔隙度变化趋势分析、镜下岩石结构的证据和砂岩压实模拟实验3个方面对延长组致密砂岩储层机械压实作用特征进行了分析。研究发现砂岩在深层与浅层压实减孔趋势一致或平行;随着上覆压力的增加,砂岩一直表现为减孔效应且机械压实作用强度随埋深的增加而变大;薄片特征显示延长组致密砂岩机械压实作用存在分级特征,不同级别的压实强度对应一定的镜下压实特征,通过统计薄片数据发现样品都处于压实作用与胶结作用对孔隙度影响评价图(Houseknecht图版)的左下区域。结果表明砂岩在埋藏致密化过程中自始至终存在机械压实作用,并且机械压实作用是导致砂岩致密减孔最重要的原因,远远超过胶结作用产生的减孔效应。由于砂岩孔隙度演化不仅与埋深有关,同样受到地质时间的影响,本次研究通过数学推导建立了砂岩孔隙度时间埋深双元函数模型,进而通过孔隙度双元函数可以对压实减孔进行定量分析,表征机械压实作用对砂岩致密化过程的影响程度。The mechanical compaction is generally regarded as a main diagenesis of sandstones in shallow layers. And it is ignored in deep strata for a long time. In recent years, the genetic mechanism research of the tight sandstones has been a central issue. In order to resolve the problem this paper utilizes porosity contrast between shallow layers and deep layers, microscopic view of sandstones composition and simulated experiment of sandstones compaction to analyze the features of the compaction. The research has found that the trend of pore decreasing between shallow strata and deep strata is consistent or parallel. And as the addition of overburden pressure, the porosity of sandstone has been decreasing and the compaction becomes stronger with the depth gets deeper. In addition, the samples data of microscopic view are all in the lower left area of the evolution map that the compaction and cementation affect the porosity. The results demonstrate that the compaction is always exists in the burial process of sandstones. It is a vital factor to densification of sandstones and its effect of pore decreasing is far greater than the action of cementation. Because the mathematical derivation of porosity evolution indicates that the compaction is controlled by burial depth and burial time, so the pore deceasing amount can be analyzed quantitatively by the binary function and then the affect degree of the compaction to the process of sandstones densification can be gained.

关 键 词：砂岩致密 机械压实作用 压实趋势 压实定量分级 压实模拟 孔隙度双元函数 

分 类 号：P618.13[天文地球—矿床学]