中国油气盆地砂岩储层的成岩压实机制分析

Diagenetic mechanisms of sandstone reservoirs in China oil and gas-bearing basins.

埋藏成岩作用理论认为碎屑沉积物的压实作用是由上覆岩柱的有效应力产生的,但该理论解释不了我国油气盆地砂岩储层的成岩作用特征。我国油气盆地复杂的地质条件导致碎屑岩成岩压实机制的多样性,它既有上覆岩柱引起的压实效应(静岩压实效应),也有盆地热流控制的压实效应(热压实效应)、地层流体性质影响的压实效应(流体压实效应)以及构造变形引起的压实效应(构造压实效应)。静岩压实效应、流体压实效应和热压实效应是沉积盆地中普遍的砂岩成岩作用现象;构造控制成岩作用贯穿于整个成岩过程,本文的构造活动指施加于岩石的构造变形作用,它引起的压实效应见于我国西部地区的油气盆地物理模拟的实验结果表明静岩压实速率为0.013～0.138%/MPa,模拟温度提高,其压实速率变大。热压实效应具有深度加大,热效应压实量(或热效应压实速率)减小;以及盆地的地温梯度差距加大,热效应压实量(或热效应压实速率)增大的特点;在相同的地层温度(T)下,低地温梯度地区的砂岩孔隙度是高地温梯度地区的e^(0.077+0.0042×T)倍。流体压实效应具有粒级越粗,其压实效应越强;以及深度变大,一定岩性储层的流体压实效应变弱,而不同粒级之间储层流体压实效应的差距变大的特点构造压实效应反映在多个方面,侧向构造挤压和基底隆升加快砂岩的压实进程,侧向构造挤压应力每增加1.0MPa,砂岩压实量平均增加0.1051%;而晚期构造推覆使下伏砂岩储层保持较高孔隙度。

The traditional theory on burial Diagenesis suggests that the compaction of deposites caused from effect stress of overloading rocks, but the theory can not interprate the diagenetic features of the Clastic Rock Reservoirs in china basins. The complicated geological conditions of china basins resulted in diversious diagenetic mechanisms of clastic rocks which includ in static compaction process caused by overloading rocks, themal compaction process by geo-themal field, fluid compaction process by strata fluid features and structure compaction process by structure deformation. The three processes afront are universal diagengtic phenomenons, and the last one only insisted in china western basins. The physical modeling tests indicates that the static compaction rates which increses as the modeling temperature are grown up is 0. 013 -0. 138%/MPa. The larger the depths ,The smaller the themal compaction values（or themal compaction rates） and the larger the geo-temperature gradiants differences between basins, the larger the themal compaction vaules. The sandstone porosity in lower geo-temperature gradiant area is e^（0.077-0.0042×T） times as the one in high geo-temperature gradiant area. fluid compaction process varied with grain sizes of sandstones and burial depth, which the coarser is the grain size and the smaller the burial depth, the larger the fluid compaction process under same grain size and the smaller the fluid compaction process besides different grain sizes. The structure compaction processes includ in lateral structure compression and base-up which sandstone compaction quickly, and late-structure thrust which let sandstone compaction vaules get smaller . The study suggests that sandstone compaction values caused by lateral structure compression were increased by 0. 1051 percentage with structure compression stress increasing 1.0MPa .