Discovery of Bozhong 13-2 Archean large monoblock volatile buried hill oilfield and its oil and gas exploration significance

Abstract

The hydrocarbon accumulation pattern of the Mesozoic covered Archean buried hill in the Bohai Oilfield was not clarified before, which restricts the oil and gas exploration progress in this area. In recent years, reservoir development modes and reservoir prediction technologies have been researched after the structural evolution and stratigraphic distribution characteristics of the buried hill in the Bozhong sag were investigated based on new 3D seismic data and a large number of cores and logging data of newly drilling wells. Then, the hydrocarbon accumulation pattern of covered type Archean buried hill was analyzed. Finally, this pattern was applied to guide the oil and gas exploration deployment in Bozhong 13-2 structure, and a significant discovery of Bozhong 13-2 large monoblock volatile buried hill oilfield was realized. And the following research results were obtained. First, the structure in this area mainly experienced multi-period tectonic movements, such as Indosinian, Yanshanian and Himalayan, and it is characterized by compression and thrusting to form a hill during Indosinian-early Yanshanian, extension and inversion transformation during middle Yanshanian, and burial and finalization during Himalayan, forming Bozhong 13-2 Mesozoic covered Archean large buried hill trap. Second, under the effect of Mesozoic cover and the control of multi-stage stress superposition, the reservoir development in this area has the distribution characteristics of “different vertical top, internal lateral continuity”. Third, the fracture prediction technology based on smooth reflection strength filter is developed. And by means of this technology, multi-scale fractured reservoirs inside buried hills can be predicted effectively. Fourth, the hydrocarbon accumulation pattern of “overpressure injection-relay migration” for covered type buried hills is established, which provides a basis for long-distance migration and large-scale accumulation of oil and gas in covered type buried hills. In conclusion, these understandings guide the discovery of Bozhong 13-2 Oilfield, achieve a breakthrough in the oil and exploration of Mesozoic covered buried hill in the Bohai Oilfield and can be used as the reference for the oil and gas exploration in the similar covered type buried hills of the Bohai Bay Basin and other areas.