Natural Gas Accumulation Condition And Favorable Exploration Zone Prediction Of Carboniferous In Huaying Mountain Western Region

The oil and gas exploration of the Carboniferous in the Huaying West area has been carried out for several decades,but no major breakthrough has been made.To this end,it is necessary to carry out research work on formation conditions such as stratum,sedimentary facies,gas source,reservoir,trap and preservation,aiming at analyzing the advantages and disadvantages of natural gas accumulation conditions and accurately evaluating the exploration prospects of Carboniferous in Huaying West.In this paper,the theory and methods of carbonate reservoir geology,petroleum geology,structural geology and seismic stratigraphy are used to make full use of drilling,oil testing,logging,seismic and analytical tests,combined with field outcrops and The results of regional research,the research on the conditions of hydrocarbon accumulation in Carboniferous and the prediction of favorable exploration zones,the main research results and understandings are as follows:?1?The remaining Huanglong Formation of the Huashixi Carboniferous system,the actual drilling thickness is 9.0³5.2m,and the whole is gradually thinned from east to west until it is sharpened;the lithology of the reservoir rock is mainly powder crystal sandstone and powder crystal algae.Granular dolomite such as sand cloud,fine powder and granule cloud;the reservoir space is mainly intergranular,intragranular dissolved and intercrystalline?dissolved?pores,local cracks are relatively developed;average porosity is 4.60%,permeability It is mostly below1×10^-3?m²,belonging to the low-porosity and ultra-low permeability reservoir.The pore permeation has weak positive correlation and belongs to the fracture-porosity reservoir,which is mainly composed of type III reservoirs.The reservoir is mainly developed in the second section of Huanglong,which is generally developed in the area and thickens from west to east as a whole.?2?The Silurian Longmaxi Formation-Ordovician Wufeng Formation shale is the main source rock of the Carboniferous gas reservoir;the organic carbon content is0.06⁹.64%,and the bottom of the Silurian Longmaxi Formation^Ordovician Wufeng Formation The black shale has a high organic carbon content of 2.2%,which is a high-quality source rock;the source rock type is a saprolite type,which has reached the mature stage.?3?The top boundary structure of the Carboniferous system is generally characterized by a monoclinic slope that slopes to the northwest except for the high-steep tectonic belt of the Huaying Mountain.The sloping tectonic zone has a high point of local development and can form an anticline trap.The trap area is small overall and the closing height is not large;the Huayushan high-steep tectonic belt also develops a small number of broken anticline traps;when the reservoir dense belt develops on the fold structure,it will produce a reservoir in the main body of the fold structure.Separation,different reservoirs in the study area independently form a tectonic-lithologic composite gas reservoir.?4?The shale of the Liangshan Formation in the Upper Carboniferous of Huaying is its direct caprock,with a thickness of 10-20 m,and the Upper Permian thick shale,compact carbonate and cream rock layers of the Permian to Triassic sediments.For its regional indirect caprock,the capping conditions are good;the large-scale structural traps are lacking in the geohistory of the study area,the local structure inheritance development is conducive to oil and gas accumulation and preservation,and the multi-phase tectonic movement makes the reverse faults develop in the Huayingshan area.The fault mainly acts as a plugging function,and the current storage conditions are good;the water samples in the actual drilling formation are calcium chloride type,which also indicates that the storage conditions are good.?5?Extensive and long-term hydrocarbon migration and accumulation occurred in the Carboniferous of Huaying,China.Driven by pressure difference between source rock and Carboniferous reservoir,along the fracture,fault,unconformity and Carboniferous The transport system formed by the layer itself completes the migration of oil and gas.?6?Carboniferous in Huaying Mountain western region is not a unified gas reservoir,and the high part of the local structural trap may be a favorable exploration zone.According to the prediction basis of the exploration favorable zone,two favorable zones are mainly selected in the study area,namely Shuinan 2-Guifuyi latent structure high belt favorable area and Laitan latent structure high belt favorable area respectively.