Oil And Gas Enrichment And Favorable Zone Optimization Of Ordovician In Bachu - Megaidi Area

The Paper focused on the Ordovician stratigraphic framework, tectonic evolution, reservoir prediction, and hydrocarbon accumulation in Bachu-Magati area of Tarim Basin, with the comprehensive discriminant technology about hydrocarbon accumulation periods in complex area and the prediction technology about small-medium scale crack-pore-cave carbonate reservoir as the key technique. Researches on the law for the development of reservoir, reservoir prediction technology and the law of accumulation and control factors were carried out to establish hydrocarbon accumulation regulation, to optimize the favorable exploration zone and the drilling target, and to provide a scientific basis for exploration and deployment in Bachu-Magati area.Research results show that the middle Caledonian act I karst, the late Caledonian karst and the early Hercynian karst were development in Ordovician in Bachu-Magati area, forming multiple sets of karst reservoirs. By the analysis of reservoir development condition and the formation and evolution of ancient uplift, it is believed that the Yubei area and East Bachu uplift area are the most favorable zones for oil and gas exploration in Ordovician in Bachu-Magati area. The oil and gas enrichment were controlled by reservoir and fault in Yubei area, the stability tectonic belt after the late hercynian activity are favorable zones for oil and gas enrichment. There are multi-period karst development in central region, so the area with good cap rock is more favorable for oil and gas accumulation.Results show that much hydrocarbon was accumulated during three periods successively. They are the early Hercynian, late Hercynian and Himalayan period. The early hercynian accumulation is characterized by early reservoirs destroyed, the late hercynian accumulation is the most effective on a large scale, and the Himalayan period is characterized by gas accumulation and reservoir adjustment. At the same time, four techniques for reservoir prediction is established, including seismic attribute analysis technology, geomorphology and karst fracture-cave engraving technology, fault-fractures detecting technology and comprehensive evaluation analysis technology.Ten favorable exploration zones are pointed out on the base of characters of geomorphology, fracture, the tectonic position, assemblages, oil and gas accumulation. This must lay a good foundation for a new breakthrough in prospecting petroleum in Bachu-Magati area.