川西坳陷新场构造带下沙溪庙组气藏成藏模式及高产富集主控因素

Accumulation Models and Main Controlling Factors of High Output and Enrichment in Lower Shaximiao Formation Gas Reservoir, Xinchang Structural Belt, Western Sichuan Depression

摘要: 中侏罗系下沙溪庙组致密砂岩储层是川西坳陷新场构造带重要的产气层，随着中浅层陆相碎屑岩勘探开发程度不断提高，寻找沙溪庙组潜力河道砂岩储层及明确不同河道致密砂岩储层天然气的成藏模式和富集规律对下一步的勘探开发至关重要。本次研究从烃源条件、储层特征、构造特征、断层特征等成藏地质条件分析的基础上，通过气藏解剖、成藏差异性分析以及断砂配置关系明确了新场构造带侏罗系下沙溪庙组高效源储配置模式和气藏高产富集的主控因素。其中断砂动态配置成藏模式可分为早期成藏后期保持型、早期成藏后期调整保留型、早期未有效成藏型三类。气藏高产富集的主控因素主要受“源、相、位”三因素的控制，成藏期持续活动的通源断层、较大的断距(>40 m)；高能水下分流河道沉积砂体；古今构造高部位、更大的圈闭幅度、更远的运移距离，且成藏期砂体以下倾方向与通源断层相接的早期成藏后期保持型、早期成藏后期调整保留型为其主要的断砂配置类型。

Abstract: The tight sandstone reservoir of lower Shaximiao formation is an important gas producer in Xinchang structural belt of Western Sichuan depression. With the continuous improvement of exploration and development in shallow continental clastic rocks, it is very important for the next exploration and development to find the potential channel sandstone reservoir and clarify the accumulation mode and enrichment law in different channel tight sandstone reservoirs. Based on the analysis of hydrocarbon source conditions, reservoir characteristics, structural characteristics, fault characteristics and other geological conditions, through the analysis of gas reservoir anatomy, accumulation differences, fault sand configuration relationship, the high-efficiency source reservoir configuration mode and the main control factors of high-output and enrichment of gas reservoir in lower Shaximiao Formation of Xinchang structural belt are clarified. The accumulation models of dynamic configuration can be divided into three types: early accumulation and late retention type, early accumulation and late adjustment retention type, and early ineffective accumulation type. The main controlling factors of high output and enrichment of gas reservoirs are controlled by “source, facies and position”, hydrocarbon source fault with continuous activity and large fault distance (>40 m) during hydrocarbon accumulation period, high energy underwater distributary channel sedimentary sandstone, the main types of fault sand configuration are the high position of ancient and modern structures, larger trap amplitude, longer migration distance, and the sand body dip direction connecting with the hydrocarbon source fault during the accumulation period.