The Study Of Tectonic Evolution And Evaluation Of Advantage Ordovician Reservoirs In Bachu-Markit Area

Bachu-Markit Area has huge oil and gas potentiality and broad prospect for exploration,and exists many problems of geological theory and practical exploration, so doing the researchof paleotectonic evolution of the area, especially the evolution process and distributioncharacteristics of palaeouplift have an extremely important geological significance for theprediction of favorable karst reservoirs.On the basis of current tectonic, of geological history peorids are restored by thecomprehensive utilization of seismic, logging and drilling data, according to the principle ofbackstripping analysis and balanced cross section. It includes several phases: early-middleCambrian, late Cambrian-middle Ordovician, late Ordovician, Silurian-middle Devonian,late Devonian-Carboniferous, Permian, Paleogene-Neogene. In addition, the distribution ofuplift, depression and ramp is divided according to the paleogeomorphology.Considering the development period and development model of faults, the palaeotectonicevolution of Bachu-Markit Area is analyzed. The result shows: the tectonic framework ofBachu-Markit Area has changed many times since the Sinian. In the early Caledonian andmid-Caledonian, the tectonic framework of Bachu-Markit Area appeared high in the northeastand low in the southwest. In the late Caledonian, The structural framework changed to be highin the north and low in the south. In the Hercynian, the tectonic framework0f Bachu Area washigh in the north and low in the south, but the Markit Area displayed high in the south and lowin the north. In the Himalayan, the Markit Area began to tilt and turned into the slope, Inaddition, the Bachu Area uplifted more intensely, forming the current tectonic framework ofBachu uplift and Markit slope.In the evolutional process of geological history, the formation period and evolution phaseof Bachu uplift and Hetian paleo-uplift are different. Bachu uplift forming in the Hercynian hasa dramatic change of the scale in the later period, but it has no direct control actions in thedevelopment of Ordovician reservoir. Hetian paleouplift beginning to form in the Caledonianhas an anticlockwise migration. It controls the development degree and distribution of theOrdovician karst reservoir of Yubei Area as the key exploration region.Through the analysis of the migration evolution of paleouplift, Bachu-Markit Areaexperiences three Paleokarst. Jade North region located at the Markit slope is the overlappedarea owning three stage of Karst, and therefore is proved to be the most favorable area of thedevelopment of the karst reservoir. In addition, the Ordovician karst reservoir developmentmode is discussesed. On the basis of seismic attributes, well logging, core data, the mostfavorable reservoir block is the most part of the region in the east of Jade North1fault, Mai2block and the junction part of Mai2block and Mai3block are the good reservoir developmentareas.