The Physical Simulation Of Oil And Gas Accumulation On Convex Convergent Ridge In Bohai Sea Area

Shallow layer in Bohai Sea is an important exploration target layer in Bohai Bay basin.Different types of convergence ridges are the key to control shallow oil and gas enrichment,and also the important basis for exploration target optimization.Taking Penglai 19-3 oilfield as an example,based on the comprehensive analysis of regional structure,reservoir type,source reservoir cap assemblage characteristics,geological conditions and main controlling factors of oil and gas reservoirs in Bozhong uplift zone,and by using drilling,logging and various analysis and test data,the series of different fault dip angles are carried out according to the unique geological conditions and main controlling factors of oil and gas reservoirs in Penglai 19-3 oilfield Physical simulation of shallow hydrocarbon accumulation controlled by convergence ridge with different unconformity dip angle series and different injection rate series,and physical simulation of hydrocarbon migration and accumulation of main fault transitional convex convergence ridge and low convex convergence ridge.Based on the physical simulation of four kinds of transport channels with different parameters,two different types of convex convergence ridges and one physical model with Penglai 19-3 geological characteristics,the dominant migration channels of shallow reservoirs in Bohai Sea and the main controlling factors of migration adjustment process of different types of convex convergence ridges are preliminarily determined Based on the experimental results,the hydrocarbon migration and accumulation rules of Penglai 19-3 oilfield in Bohai uplift are summarized.The main conclusions are as follows(1)The Buoyancy is the main driving force of shallow oil and gas in Bohai Sea,and low fault and unconformity dip angle are the important factors affecting its vertical component.The relative size relationship between them is the main factor determining the optimization of oil and gas migration path.According to the results of physical simulation experiments,the semi quantitative evaluation criteria for the effectiveness of secondary migration pathways in this area are established:when the unconformity dip angle is less than 10°,faults and unconformities can be used as migration channels;When the dip angle of unconformity is more than 20°,As the dip angle of unconformity continues to increase,unconformity replaces faults and becomes the dominant channel for hydrocarbon migration.When the fault dip angle is less than 60°,unconformity is the main channel of secondary migration;When the dip angle of fault is more than 70,Fault can replace unconformity and become the main channel of secondary migration.(2)Before reaching the fault of high angle cutting ridge,the oil in high convex convergent ridge only occupies a small part of the thickness of unconformity transport layer;When it reaches the cut ridge fault,due to the high dip angle of the fault,large vertical buoyancy component and sufficient migration power,it can quickly adjust to the upper Anticline of the convergence ridge and fill the whole anticline trap,and the adjustment speed is far faster than the hydrocarbon expulsion rate.Nearly 50%of the oil is transferred to shallow reservoirs,which shows that the high convex convergent ridge has strong hydrocarbon accumulation ability and good reservoir control effect.(3)Due to the smaller wing angle and less buoyancy in the vertical direction,the corresponding convergence ridge has weak internal movement force,low adjustment efficiency and slow adjustment process.Although the shallow layer of the low uplift type convergence ridge can also enrich oil and gas,compared with the high uplift type convergence ridge,the accumulation of oil is small,the migration efficiency is low and the time required is long.(4)The simulation of hydrocarbon accumulation in Penglai 19-3 structure shows that the amplitude,physical properties and thickness of convergence ridge,and the distance between ridge and source are the main factors affecting the hydrocarbon accumulation capacity of convex convergence ridge.The multi-stage high angle fault and large area unconformity constitute the dominant migration and accumulation system of the convergence ridge of Penglai 19-3 high uplift,resulting in the relative concentration of oil and gas in the core of the convergence ridge;The wing of convergence ridge and slope area can only be used as lateral migration path,and it is difficult to form large-scale oil and gas accumulation.