气候与构造控制下湖相优质烃源岩的差异分布——以渤中凹陷为例

Differential distribution of high-quality lacustrine source rocks controlled by climate and tectonics:a case study from Bozhong sag

基于地球化学、测井和沉积相等资料开展了渤中凹陷的优质烃源岩分析。结合区域地震解释,对渤中凹陷优质烃源岩的分布进行了刻画,并探讨了气候、构造作用下优质烃源岩分布的差异性。结果表明,受气候控制的咸化环境与受构造控制的快速沉降环境所形成的优质烃源岩具有不同的富集特征。在咸化环境控制下,沙河街组一段优质烃源岩的分布面积占洼陷面积的81.9%,呈广覆式分布;在构造沉降控制下,平面上,沙河街组三段和东营组三段的洼陷沉降速率与优质烃源岩所占洼陷面积的比例呈明显正相关,纵向上,湖泊的氧化-还原界面控制了优质烃源岩的富集程度。在气候形成的咸化环境和构造快速沉降的控制下,渤中凹陷及邻区优质烃源岩的发育条件可分为3类:以咸化水体为主导、以构造沉降为主导以及咸化水体-构造沉降共同控制。在潮湿气候和构造沉降速率较低的情况下,不发育优质烃源岩。

Based on the geochemistry data,well logging and sedimentary facies in Bozhong sag,an analysis was performed on highquality lacustrine source rocks.In combination with regional seismic interpretation,this paper describes the distribution of high-quality source rocks in Bozhong sag,and then discusses the differences of source rocks under the effect of climate and tectonics.The results show that the high-quality source rocks formed in the saline environment controlled by climate and the rapid subsidence environment controlled by tectonics present different enrichment characteristics.The distribution area of high-quality source rocks in the Member 1 of Shahejie Formation under the main control of the salinized environment accounts for 81.9% of the depression area,showing a broad distribution;in Member 3 of Shahejie Formation and Member 3 of Dongying Formation under the control of tectonic subsidence,a significant positive correlation exists between the depression subsidence rate and the distribution area of high-quality source rocks in the depression.The redox interface of the lake controls the enrichment of high-quality source rocks in the longitudinal direction.Under the control of saline environment and rapid tectonic subsidence formed by climate,the development conditions of high-quality source rocks in Bozhong sag and adjacent areas can be divided into three categories dominated by salinized water,tectonic subsidence,and jointly by salinized water and tectonic subsidence,respectively.In the case of humid climate and low sedimentation rate,high-quality source rocks are not developed.