箕状断陷湖盆不同构造区带成岩作用特征及差异性研究:以东营凹陷沙河街组为例

东营凹陷在沙河街组沉积期为北陡南缓的箕状断陷湖盆,凹陷内可进一步细分为陡坡带、缓坡带、洼陷带及中央背斜带。在沙河街组成岩演化过程中发育了多种类型的成岩作用,主要包括压实作用、压溶作用、溶解作用、胶结作用等。不同构造区带成岩作用具有明显的差异性,具体表现为:压实作用总体表现为早期压实影响较大,后期较小,但不同构造区带差异明显;胶结作用在不同构造区带碳酸盐胶结胶物含量不同。不同粘土矿物在不同构造区带含量及转化深度不同;溶蚀作用在不同构造区带发育深度不同,从而导致次生孔隙带发育深度均明显不同。不同构造区带成岩作用的差异性导致不同构造区带成岩相带类型、特征不同。详细研究这种差异性对于寻找岩性油气藏具有重要的理论价值和实际意义。

Research on Diagenetic Difference of Various Structural Belts in the Halfgraben-like Rift Lake Basin:Taking Shahejie Formation in Dongying Depression as an Example

Dongying depression is a halfgraben-like rift lake basin with the characteristics of steep slope developed in the north while gentle slope in the south during Shahejie period.The depression can be divided into four structural zones,i.e.steep slope zone,gentle slope zone,sag zone and build-up zone.There are various diageneses developed in the Shahejie Formation,including compaction,pressolution,solution and cementation,and so on.Diagenses developed in different structural belts are always different.Compaction during earlier period can impress more effect on the reservoirs than that during later period.The amounts of carbonate cements and clays vary in different structural belts.The solution depth differs in various structural belts,thus the depth with secondary porosity occurrence is different obviously.The diagenetic difference of various structural zones can create different diagenetic facies belts with unique characteristics.Therefore,it is quite important theoretically and practically to study such differences among various structural belts for lithological oil and gas pool exploration.