Study On The Evolution Characteristics Of Bedrock Natural Gas Transport Force In Dongping Uplift In The Front Of Altun Mountains

With the development of exploration work in the Dongping area,people have recognized the potential of natural gas reservoirs in the Dongping area and gradually increased their research work in the area.Through previous studies on the comparison of oil and gas sources in Dongping area,we realized that the natural gas in Dongping area is an out-source gas reservoir.There is no source rock in the area itself.The geochemical characteristics of natural gas in the area are similar to the Jurassic hydrocarbons in Pingdong depression.The source rocks are highly consistent,relying on the connection of deep and large faults,and migrated to the Dongping area in a long distance to form reservoirs.However,so far,there have been few studies on the natural gas transportation force in Dongping area.In this paper,the Dongping area is taken as the research object,using logging,seismic data and measured data,etc.,to develop the characteristics of formation pressure in Dongping area.Study and analyze the cause mechanism of abnormal pressure in the study area by logging curve method and plate recognition.Then,based on the analysis of the pressure characteristics and the cause,numerical simulation of the study area was carried out from the perspective of fluid potential This paper analyzes the streamline during the main reservoir-forming period in Dongping area,with a view to summarizing the evolution law of natural gas migration force in Dongping area.The final study concluded that?1?the overpressure and normal pressure systems coexist in the formation of Dongping area,and the reservoir generally exhibits abnormally high pressure,the pressure coefficient is between 1.26 and 1.48,and the excess pressure is between5¹5MPa;the mudstone pressure characteristics are based on the equilibrium depth According to the calculation method,the pressure in different layers shows obvious differences.The buried depth is more than 1000m and it shows normal compaction.E₃¹ has abnormally high pressure and the excess pressure is between 6.22⁸.21MPa.E₁₊₂+2 also shows high abnormal pressure.2 The residual pressure of the gypsum mudstone at the bottom can reach about15MPa;?2?The abnormal pressure of mudstone in the Dongping uplift of the Altun Mountains is due to uneven compaction,and the contribution of the remaining pressurization mechanisms is negligible;Reservoir abnormal pressure is controlled by multiple mechanisms.Hydrocarbon generation pressurization,fluid expansion and overpressure transmission play a major role,and the contribution of each mechanism of pressurization in different layers of reservoirs also varies greatly.The contribution of compression and fluid expansion is 37%⁴4%,and the contribution of uneven compaction is about 50%;The contribution of hydrocarbon generation pressurization and fluid expansion pressurization in E₁₊₂+2 reservoir is about 82%,and the contribution of bedrock reservoir hydrocarbon generation pressurization and fluid expansion pressurization is more than 90%;The contribution of structural squeezing and pressurization in the study area is based on the results of previous calculations.After the calculation of the sealing coefficient parameter 0.3391⁰.3474,the contribution is about 4%¹0%.?3?According to the instructions of the numerical simulation streamline,the oil and gas in the high potential area of Pingdong Sag has a tendency to migrate to the high structural part of Dongping uplift.Early Pliocene Entering a large amount of oil generation stage,after entering the Pliocene,it began to enter a large number of gas generation stages,and the late Pliocene reached the maximum amount of gas generation.The bedrock accumulation of the Ping uplift is an extra-source storage and accumulation model.It depends on the vertical transmission of the high-quality source rocks connecting the Pingdong Great Fault to the Pingdong Sag.It depends on the migration of unconformity and high-quality sand bodies in the lateral direction.With the combination of closed faults,the development of bedrock pores and fissures,and the anticline structure,the accumulation pattern of bedrock gas reservoirs in Dongping uplift was formed.