The model of compound traps development and controlling factors of hydrocarbon enrichment in Kongqueting area of the Xihu Sag

With the advancement of exploration degree, the western slope belt of the Xihu Sag in the East China Sea has fully entered the stage of fault-lithologic compound reservoir exploration. The Kongqueting area, located in the north-central part of the western slope belt, is a favorable area for compound reservoirs. We specified the formation conditions, the development patterns, and the controlling factors of differential enrichment of hydrocarbon in compound reservoir of the study area by studying on the structure and sedimentary settings, the controlling effect of faults and paleogeomorphology on sand distribution, and hydrocarbon accumulation and enrichment rule in different zones and formations. In geomorphology, it was high in the west and low in the east in the study area. It developed multiple U- and V-shaped valleys on the ancient uplifts in the west of the study area, the ancestral rivers and the sand distribution were controlled by the north-east faulted slope-break and the north-west flexural slope-break. The north-west sand bodies matches the north-east faults, and formed the fault-lithological compound traps, which has become an important field for exploration and expansion of reserves in the study area, and achieved a breakthrough in fault-lithological reservoir exploration. The degree of hydrocarbon enrichment is different in Konqueting area, and is controlled by the distance between trap and source, the size of sand body, the fault plugging capacity, and their combinations. The middle and low Kongqueting area has the highest degree of hydrocarbon enrichment and the best expansion potential because of the proximity to source rock, the best storage condition, the large sand body, and the good reservoir properties.