Exploration Breakthrough and Recognition of Peripheral Potential in the Southwest Margin of Weixi'nan Low Uplift

Weizhou oilfield on the southwest margin of Weixi'nan low uplift has made a major breakthrough in exploration and evaluation, which proved reserves exceeding 10 million tons. It indicates that the marginal depression D Sub-sag is a hydrocarbon rich depression. To further explore the exploration potential around D Sub-sag, combined with regional data, the exploration potential around the southwest margin of Weixi'nan low uplift is re-recognized based on the comprehensive analysis of drilling, seismic and laboratory data. It is believed that the high-quality semi-deep and deep lacustrine facies source rocks in the second member of Liushagang Formation are developed in D Sub-sag and Haizhong-depression, with the thickness of 200～1 000 m, organic matter abundance of 1.4%～7.8% and organic matter typeⅠ-Ⅱ₁, which have the exploration potential of 100 million tons. Based on the new understanding of "Near source three-dimensional accumulation, favorable structural background control wealth", comprehensive analysis shows that the structural ridge in the eastern slope zone of D Sub-sag has favorable conditions of "stereo expulsion of hydrocarbon, high efficiency conduction and integral block". The northern steep slope of Haizhong depression has the characteristics of "hydrocarbon supply in deep faulted depression, inheritance uplift, efficient transport of faulted sand and enrichment of multi-type traps", and it is a accumulation area of large and medium-sized oil and gas reservoirs. It points out the direction for further exploration and deployment in the study area.