Research On Fault Sealing Mechanism And Hydrocarbon Migration And Accumulation Characteristics

Exploration shows that fault reservoirs are widely distributed in China.When faults are sealing,they can seal oil and gas to form fault reservoirs.When the fault is not sealed,the fault plane can be used as the main advantage channel for hydrocarbon migration,and the deep hydrocarbon migration can be moved to the shallow layer to accumulate and accumulate.In the process of exploitation of fault reservoirs,it is necessary to deeply study fault sealing mechanism,main controlling factors of fault sealing,hydrocarbon accumulation characteristics of closed faults and migration characteristics of open faults,so as to improve the accuracy of exploration,reduce the risk of exploitation and avoid hydrocarbon escape.Therefore,this paper systematically starts from the fault sealing mechanism,sets up the physical simulation experiment method of fault sealing,and combines theory and experiment to demonstrate the main controlling factors of fault sealing mechanism and the influence law of changing the related factors of fault sealing.In addition,typical faults in the study area are selected to be analyzed from the perspective of mechanics to establish a three-dimensional model of faults.Numerical simulation software COMSOL is used to simulate faults under the action of oil and gas accumulation and faults under the action of oil and gas migration to obtain the change rule of stress and strain of faults.The main work completed is as follows:(1)Based on the fault sealing theory,the main controlling factors of fault sealing are the fault gouge ratio,the occurrence of the section and the lithology of the two walls.The fault sealing mechanisms include argillaceous filling sealing mechanism,late diagenetic sealing mechanism,mudstone smearing sealing mechanism,sand and mud butt sealing mechanism,etc.(2)In combination with the main controlling factors of fault sealing,a physical simulation experiment of fault sealing was set.The change rules of vertical fault sealing and lateral fault sealing were obtained by changing different dip angles and different mudstone contents,and the critical fault sealing pressure was obtained by using interpolation method.(3)When the fault is in open state,the fault can be used as the dominant channel for oil and gas migration to transport deep oil and gas to shallow oil and gas reservoirs.The fault model with different dip angles and different shale content is set up,and the influence of changing fault conditions on oil and gas migration is obtained through numerical simulation.(4)In the process of oil and gas migration along the fault,the stress inside the fault changes with the passage of oil and gas.The numerical simulation software is used to simulate the stress and strain of three-dimensional fault under the action of oil and gas migration,and the migration mode of oil and gas along the fault is predicted according to the simulation results.(5)When the fault is sealed,the fault can block oil and gas,so as to accumulate and form fault reservoirs.By classifying the characteristics of fault reservoirs and selecting the closed faults in the study area for modeling simulation,the stress and strain conditions of faults under oil and gas accumulation and accumulation can be obtained.