Tectonic Characteristics And Its Control On Hydrocarbon Accumulations In The South Region Of Bohai Bay Basin

Bonan is an important hydrocarbon accumulation zone,which located in the Bohai Bay basin.The tectonic evolution controlled the process of hydrocarbon accumulation.Therefore,the paper focused on the research of basic geological reservoir conditions Oil-gas accumulation controlled bystructural characteristics,basing on the region structural study.Furthermore,through anatomy of typical reservoirs,this paper has been finally clear about the main control factors of the different structural belts and enrichment regularity.At last,this paper predicts oil-gas favorable exploration zone.The Cenozoic fault system of Bonan area have three groups of directional faults,three faults properties,three stage tectonic evolution.These features controlled the formation and evolution of basin structure and tectonic style.The activity of fault controlling sags,basin geomorphology,sedimentation and subsidence center allied to regulate the distribution characteristics and thermal evolution difference of source rock.In the paleogene period,the basin subsidence was dominated by the strongly active fault,which controlled the areal extent deposition of fan delta,braided river delta and half-deep and deep lake-deep facies.In the neogene period,the fault activity start to weaken sharply,which controlled the areal extent deposition of the braided river plains,meandering-stream delta,shore-shallow lake sedimentary facies.Cenozoic tectonic tectonic movement dominate the whole process of Oil & gas migration and accumulation.Oil source fault is the key factor of hydrocarbon accumulation,that transporting capacity of oil source fault is determined by the intensity of fault activity at the main stages of hydrocarbon generation and expulsion,regional caprock,fault-reservoir dispositional relation.When the fault activity rate less than 5m/Ma in the period of hydrocarbon expulsion and the capping rock effective thickness over than 10 m,are favourable for deep layer oil and gas pool forming.Meanwhile,when the fault activity rate over 8m/Ma in the period of hydrocarbon expulsion and the capping rock effective thickness less than 0m,are in favor of shallow layer oil and gas pool forming.The fault-reservoir displacement pressure determines the filling ability of oil and gas reservoirs.The ability of lateral Lateral migration of oil and gas was under control of strata pressure and fluid potential.Structural traps make up of the main types of traps in Bonan area.The NNE Tanlu fault zone and near NWW and EW fault controlled lateral distribution of traps.The number and types of shallow traps are more than deep traps owing to Tanlu fault slip late-reformation.The distribution of effective traps is controlled by the lateral fault sealing ability.The main controlling factors and pool-forming model are obviously different from each structural belt.The main controlling factors of hydrocarbon accumulation in the Western strike slip zone is the late fault activity intensity,central strike slip zone and steep slope zone is regional mudstone caprock thickness and fault-caprock configuration relation,but hydrocarbon source rock condition is main factor in eastern strike slip zone.On the contrary,the gentle slope belt and the central uplift belt of reservoir were hydrocarbon migration and accumulation conditions.