The Discussion Of Volcanic Reservoir Characteristics And Formation Mechanism In The Southern Songiiao Basin, NE China

The void spacetypes and combination pattern of deep volcanic rocks gas pool arecomplex in the southern Songliao Basin, NE China. The geological data reveals thatthe volcanic reservoir effectiveness is controlled by secondary pores.It is beneficial tolocate the favorable volcanic reservoir and promote the process of exploration anddevelopment of volcanic gas pool that definite the formation and evolution ofvolcanic secondary pores.Through volcanic lithology correction and volcanicfacies classification based onthe core and debris, the volcanic physical properties analysis based on the measuredporosity and permeability, logging porosity, thin section identification, ScanningElectron Microscope(SEM)and energy spectrum analysis, X-ray diffraction analysisbased on the core and sidewall core, have a study on the deep volcanic rocks such ascharacteristics of lithology and facies, types of void space, types of diagenesis andreservoir formation and evolution stage within open and semi-open system in thesouthern Songliao Basin.Combining with burial history based on the logging data andseismic data, analyze the the formation and evolution of the typical well area volcanicreservoir in southern of Songliao Basin.The mainconclusions isas following:The types ofvolcanic void spaceincludeprimary pores, secondary pores andfractures which can be classified into9subtypes further.The relationship betweenprimary pores and secondary pores is inherited. The types of volcanic void spacearecontrolled by the lithology and facies, diagenetic models. The types of diagenesis isclassified into vaporization of volatile matter, corrosion, welding, compaction, filling,mechanical impaction and pressure solution, metasomatism, devitrification andrecrystallization, dissolution.The formation and evolution of volcanic reservoir can be classified into twostage: pre-burial stage and burial stage.The pre-burial stage is classified into3phases:condensation(compaction) phase, hydrothermal phase, weathering and leaching phase.The burial stage is classified into early burial stage (0-1000(±200)m, paleogeo-temperature:0-80(±10)℃), middle burial stage (1000-2500m, paleogeotemperature: 80(±10)-140℃), late burial stage (＞2500m, paleogeotemperature:＞160℃).Thepre-burial stage mainly influences the development of primary pores,the burial stagemainly influences the development of secondarypores and reconstruction of primarypores. The dissolution caused by release of organic acids during middle stage (periodfrom Quantou stage to Qingshankou stage) is the reason that volcanic reservoir formabnormal high porosity zone.The research suggests that the typs and content of clay inthe volcanic reservoir (openand semi-open system) can be compared with sedimentaryreservoir in some ways such as montmorillonitealters tomixed layer clay when burialdepth increases. The content of clay in volcanic reservoir is higher compared with thesedimentary reservoir because the unsatable minerals of volcanic rocks generateagreat quantity of clay during burial stage.