Study On The Relationships Between Faults And Oil Accumulation Of Shallow And Non-generating Beds In Zhanhua Depression

As the junction of source rocks and reservoirs,faults play a significant role in controlling the generation and distribution of the allochthonous reservoirs in shallow strata.The Neogene of Zhanhua Depression is shallow non-hydrocarbon generation strata which develops numerous faults and is rich in oil and gas.There's close relationship between hydrocarbon distribution and faults.This paper makes comprehensive research on the relationship between the control of fault and hydrocarbon accumulation in order to investigate the fault controlling mechanism which can reflect the hydrocarbon accumulation characteristics in the non-hydrocarbon generation strata.The faults in Zhanhua Depression are divided into four levels according to the size and fault activity.Primary and secondary faults are mainly pathways of hydrocarbon migration in shallow strata,four-level faults work as adjusting faults while Tertiary fault contributes little.The oil in the shallow layers mainly distribute along primary and secondary faults.Faults control the distribution of oil in fault basin.Fault activity plays an important role in controlling on hydrocarbon accumulation which can manifest itself in multiple ways.(1)Fault activity affects the hydrocarbon generation intensity and the distribution of source rocks.(2)Fault activity affects the distribution and scale of sand body.(3)The faults break the sealing ability of cap rock.(4)The quantitative evaluation method of fault transport capacity is proposed.The fault transport capacity controls the enrichment of Neogene oil and gas.The control of fault sealing on hydrocarbon reservoir distribution is divided into two aspects of vertical and lateral sealing.Lateral sealing ability of faults at different depths have differences,caused the differences of oil-gas enrichment in both sides layers.Based on judging fault during the event as the possibility of vertical channel we proposed quantitative evaluation method for faults vertical sealing in order to establish the relationship between distribution of shallow oil and gas and vertical sealing.Through the analysis of the accumulation process of Gudao drape body and Chenjiazhuang North-slope,two hydrocarbon accumulation patterns were established including "near-source for hydrocarbon,fault transportation,structure controlling traps" and "far-source for hydrocarbon,combinated transportation,stratum controlling traps".