东濮凹陷文23气田沙四段储层沉积相特征

Characteristics of sedimentary facies in the fourth member of Shahejie Formation in Wen 23 Gas Field,Dongpu Depression

东濮凹陷文23气田沙河街组四段是该地区主要的天然气储集层系,其发育及展布主要受沉积相带和后期构造控制。综合利用地震、钻井和测井资料,分析文23气田沙四段沉积体系与沉积微相特征,并根据沉积相演化特点探讨其古地理特征。研究认为:文23气田区沙四段上部以咸水较深湖沉积为主,其次为滨浅湖相滩坝沉积和重力流沉积,发育较厚的灰色粉砂岩,为沙四段主要储气层;沙四段下部主要为漫湖相砂坪、混合坪和泥坪沉积,发育紫红色粉砂岩。沙四段沉积时期盆地处于初始裂陷期,盆地为浅水湖泊环境干旱、半干旱气候湖水面受季节性洪水补给作用影响;沙四段上部沉积时期湖水逐渐加深。沙四段沉积整体处于湖泊水进期物源体系主要来自西北方向。

The fourth member of Shahejie Formation in Wen 23 Gas Field of Dongpu Depression is main gas reservoir series in this area.Its development and distribution are mainly controlled by sedimentary facies and later structure.This paper analyzes the sedimentary system and sedimentary microfacies charateristics of the fourth member of Shahejie Formation in Wen 23 Gas Field by the use of seismic,drilling and logging data.The paleogeographic features are discussed according to the evolution characteristics of sedimentary facies.It is believed that the upper fourth member of Shahejie Formation in Wen 23 Gas Field was mainly deposited in the saline water environment of deep lake,followed by the beach bar deposit of shore-shallow lake facies and gravity flow deposit,with the thick grey siltstone developed,which was the main gas reservoir in the fourth member of Shahejie Formation.The lower fourth member of Shahejie Formation was mainly the flood-overlake facies sand flat,mixed flat and mud flat deposits,with crimson siltstone developed.In the depositional period of the fourth member of Shahejie Formation,the basin was in the initial faulted depression period.The basin deposited in shallow water lake environment with dry and semiarid climate and the lake water level was controlled by seasonality flooding alimentation.The lake water deepen in the deposition period of the upper fourth member of Shahejie Formation.The deposition of the fourth member of Shahejie Formation was entirely in the lake water entering period and the provenance system was from northwest direction.