STUDY ON INTERLAYER KARST MODEL OF ORDOVICIAN CARBONATE RESERVOIRS IN THE TAZHONG AREA, TARIM BASIN, CHINA

摘要

The current exploration of interlayer karst reservoirs in the Tazhong area of the Tarim Basin has achieved breakthroughs, and large-scale industrial oil flow has been obtained. Karst is one of the key factors for the formation of high-quality carbonate reservoirs. In order to further clarify the development patterns and reservoir characteristics of interlayer karst in the Tazhong area, we conducted a field outcrop survey and indoor rock sample analysis for two typical interlayer karst profiles and one weathering crust karst profile. Through this study, an interlayer karst reservoir geological model was established, which includes single-stage and multi-stage inter-layer karst modes. At the same time, the distribution law and scale of interlayer karst were analyzed. The study shows that the interlayer karst has obvious vertical zoning, and the single-stage interlayer karst develops the Tuberculum loam zone, the weathered crack zone and the dissolution cave zone. The connectivity of the dissolution caves is poor, but they are the main contributors to the karst reservoir. The inter-layer karst develops multi-stage sedimentary cycles, which are significantly different from the traditional weathering crust karst. Multiple sedimentary cycles can form tens of meters of inter-layer karst development zones and form favorable carbonate reservoirs.