Reservoir Forming Regularity Of Volcanic Gas Reservoirs In Eastern Changling Fault Depression,Songliao Basin

The study area is the eastern part of Changling fault depression in the southern Songliao basin.The gas reservoir in this area is volcanic gas reservoir,and the offshore gas field in the south of Songnan area has been found with industrial gas drilling,but there are many failed wells.This paper selects 8 typical drilling wells in this area,and analyses the reservoir forming conditions of each drilling.The comparison of the differences is helpful to further optimize the target area.In this study,through comprehensive analysis of data,such as logging data,seismic profile,rock hand specimen,mirror thin slice,scanning electron microscope,mercury pressure test,nitrogen adsorption test and so on,the characteristics and types of the reservoir cover ring transportation of each drilling rig are studied in detail,and the conditions of the well formation are clarified.On this basis,the control is put forward.The main controlling factors of volcanic gas reservoirs in the eastern part of the Changling fault depression are summarized,and the reservoir forming pattern is summarized.According to the study,the source rocks in the study area are mainly distributed in the Shahezi Formation,a small number of them are distributed in the Huoshiling formation,and the contribution of Yingcheng Formation source rocks is relatively small.The main reservoirs are the Yingcheng Group volcanic reservoir,the middle part of the middle part of the Daerhan fault belt and the volcanic reservoir of the inner Yingcheng Formation of the North Zhigan flower inner Yingcheng Formation are mainly acid erupting rocks,the main lithology is the stomatal rhyolite,the massive rhyolite and the rhyolite tuff lava,while the Western gentle slope zone and the southern Chaganhua inthe daerhan fault convex belt are the main ones.The main volcanic rocks are mainly volcanic rocks with basalt and coarse volcanic clastic lava.The two wells in well waist depth 1 and well 3 well formed mainly with stomatal rhyolite as the main reservoir.The original gas hole is more developed and the stomatal connectivity is better.The reservoir space is mainly primary pore,devitrified pore and structural fracture,which belongs to high porosity and medium permeability reservoir,and the gas reservoir in well depth 2 well is low in structure position and in later period.The reservoir space is mainly composed of dissolution pores and structural fractures in the phenocrysts,and it is a meso medium permeable reservoir.Well the 4 well and 5 well in the waist depth are located in the sedimentary center of the source rock,but the main reason for the failure of the two well is that the hydrocarbon gas is difficult to move to the reservoir because of the two section of the granite intrusive rock in the Shahezi Formation.The waist depth 7 is located in the eastern slope of the Chaganhua sag.Because the distance from the hydrocarbon generation center is far away,the lateral migration is difficult and the development of the trap is poor,and it is difficult to form a large gas reservoir.The reservoir of long Shen 2 well is mainly pore rhyolite with good physical properties.However,due to the low structural position and under the gas water surface,the drilling water production is more.Well Dongshen 1 is located on the western slope belt of the daerhan fault belt.The reservoir is mainly basalt,and the basalt has a strong late effect.The primary pores and cracks are filled with quartz and calcite,and the reservoir is poorly developed.According to the study of source rock,reservoir,cap and trap,combined with the analysis of the success or failure factors of drilling,it is considered that the main controlling factors of the area are four factors of effective source rock,trap condition,fault condition and volcanic reservoir.The typical fractured anticline reservoir formation model in the middle waist depth 1 well position in the middle of the study area,the daerhan paleo uplift formed anticline structure,and later daerhan fault connected the hydrocarbon source rock and anticline trap in the ChaganHua depression,and the fracture provided the vertical migration channel,and hydrocarbon gas wasformed in the anticline trap.The unconformity surface-fault nose formation model of the 2 well position in the waist depth is unconformable contact with the formation of Shahezi Formation and Yingcheng Formation,and the hydrocarbon gases in the Shahezi Formation migrate along the sand body,and are migrated to the dense reservoirs vertically along the faults.The 3 well is the model of weathering crust and fault nose formation,the secondary fracture formed in the late stage of the fault structure connects the source rock and reservoir.The reservoir lithology is mainly the stomatal basalt,and its physical property is good and the reservoir performance is good.Because the East yingtai area is located at the high position,the volcanic rocks are strongly weathered and eroded and eroded,and the reservoir is improved.Therefore,the waist deep 3 well is accumulated in the weathering crust reservoir.