Abstract:

The exploration of basement buried hill in Qiongdongnan basin is facing many problems, such as unclear geological age, strong reservoir heterogeneity and complex accumulation forming conditions. Through regional tectonic evolution, basement zircon dating, buried hill reservoir description and accumulation forming dynamic analysis, the development area and favorable accumulation area of buried hill reservoir are identified. The study shows that under the superimposed control of Indosinian, Yanshanian and Himalayan orogenic movements, Indosinian granite buried hill reservoirs are widely developed in Songnan low uplift and Lingnan low uplift. In plane view, three groups of faults and fractures in NW, NE and near EW directions are cut into a network, forming a double-layer structure with a total thickness of more than 300 m in weathering fracture zone vertically. It is clear that brittle minerals and bidirectional fluid transformation are the key factors for the development of fractured reservoirs. Based on the Early Oligocene paleogeomorphology and source rock sedimentary study, the accuracy of TOC distribution prediction of terrigenous marine source rocks in Yacheng Formation is improved, and the distribution law of high-quality hydrocarbon source in central depression is clarified. By comprehensive analysis of the relationship between the distribution of Paleogene burial hill reservoir and space-time configuration with Yacheng Formation hydrocarbon source stove, two natural gas accumulation models are established, which are “long-distance lateral migration and high buried hill limited-accumulation outside the source” and “short-distance migration and low buried hill efficient-accumulation alongside the source”.So L26-B is the the potential prospect.

Key words: Indosinian, basement buried hill, fractured reservoir, terrigenous marine source rock, hydrocarbon accumulation model