Research On The Characteristics And Evaluation Of Clastic Rock And Volcanic Rock Reservoirs In Dehui Fault Depression, Songliao Basin

Dehui fault depression in Songliao basin is an important target for regional oil and gas exploration.There are two types of reservoirs,clastic rock and volcanic rock.In this paper,the petrological characteristics,physical properties and influencing factors of these two types of reservoirs are studied.The reservoir performance of clastic rocks in Dehui fault depression is medium,and the proportion of siltstone fine sandstone and glutenite is about 30% except for the marginal area.Strong diagenesis seriously reduces porosity,resulting in poor reservoir performance of clastic reservoirs in the study area.In contrast,epigenetic diagenesis can improve the reservoir performance,but the increment of secondary pores is lower than the decrement of primary pores caused by diagenesis.Ultra micro permeability and micro permeability are the dominant clastic reservoir types in the study area.The heterogeneity of the reservoir is strong in the layer,between layers and between wells.Even in the same sand body(oil layer),the physical properties change greatly.On the whole,the reservoir performance of clastic reservoir in the south of Dehui fault depression is better than that in the north.The lithology of deep volcanic reservoir in Dehui fault depression mainly includes volcanic lava and pyroclastic rock.The main reservoir space of volcanic lava is secondary pores and fractures,with less primary pores.In contrast,the reservoir space of pyroclastic rocks is dominated by secondary pores with a small amount of primary intergranular pores.Secondary alteration,including carbonation,illitization and chloritization,is the main factor affecting volcanic reservoir performance.Among them,carbonate filling and metasomatism make reservoir physical properties worse,while illitization,chloritization,dissolution,vitrification and other actions produce a large number of secondary pores,which have dual functions of storage and connectivity,making reservoir physical properties better.In addition,the structural fractures formed by multi-stage tectonic activities in the study area can connect the primary pores and improve the reservoir performance of volcanic reservoirs.This study reveals the complexity of the factors affecting the reservoir performance of the two types of reservoirs in Dehui fault depression,and makes it clear that epigenetic rock is the main factor for improving the reservoir performance of clastic rock reservoirs,while dissolution is the main controlling factor for improving the physical properties of volcanic reservoirs,which provides reference information for the evaluation of reservoir performance and the determination of favorable exploration targets in the next step.