镇泾长8砂岩古孔隙度恢复方法与应用

Restoration Methodology of Sandstone Paleoporosity and Its Application to Chang Formation in Zhenjing Area

砂岩储层古孔隙度特征和演化过程是油气成藏机制研究的重点和难点。现行方法存在一些缺陷,包括影响因素考虑不全面,应用过程复杂繁琐,运用结果可靠性不高,不能体现孔隙度演化的整个过程。本文提出一种新的砂岩古孔隙度恢复研究方法,综合考虑了建设性和破坏性成岩作用的影响,建立砂岩孔隙度演化的数学模型,以此恢复砂岩孔隙度演化的整个过程。建立的模型以效应模拟为原则,包括增孔作用和减孔作用模型,通过模型叠加得到总孔隙度演化模型。模型以时间为变量、现今孔隙度为约束条件体现动态性和可靠性。在镇泾地区的应用结果表明,镇泾地区砂岩孔隙度演化受到构造和沉积相的控制,优质储层主要分布在水下分流河道和局部微构造的高点。储集层孔隙度演化过程是高产油藏的主控因素。

Paleoporosity and its evolution of sandstone reservoir is a hard and key task for studying the mechanism of hydrocarbon accumulation. Current methodology has some limitations. It can not take all controlling factors into consideration,the application process is too complicated,the precision of result is low and it can not embody the whole process of porosity evolution. Based on the project which studies on the mechanism of hydrocarbon accumulation within Chang Formation in Zhenjing area of Ordos Basin,a newly methodology to restore the paleoporosiy of sandstone is presented. This methodology is based on diagenetic history of strata and takes constructive and deconstructive diagenesis of porosity into account. With the effect-oriented simulation as the principle,the simulation process is divided into porosity decrease process and increase process. With the geological time as variable and constrained by the current porosity,the model demonstrates dynamic and reliable characteristics. The application of this methodology to Zhejing Area indicates that the evolution of the sandstone porosity is controlled by structure and sedimentary facies,and the distributary channel sandbodies along the up-lip direction of the monocline is the favorable location for the high-quality reservoirs. The process of porosity evolution of sandstone is a key control factor for a high-production hydrocarbon accumulation.