Study On The Gravity Flow Sedimentary Reservoir Architecture In The Gentle Slope-deep Depression Area Of The Continental Fault Basin

The stratigraphy of gravity flow depositional system are important oil and gas reservoirs in both Marine and continental basins.A series of hydrocarbon exploration breakthroughs in large gravity flow deposits have attracted many attentions.The studies mainly focus on the genesis mechanism,the fluid properties,the transport mechanism and so on.However,due to the various types of gravity flow deposits and the complex forming environment,the research on the internal structure and configuration characteristics of different gravity flow deposits is not enough at present,which restricts the effect of oil and gas development.In this paper,the gravity flow sedimentary characteristics of the landscapacity flow,the deposition characteristics of the collapse type gravity flow and the heteropathic stream are studied based on the previous studies.The controlling factors of gravity flow deposits and the corresponding sedimentary characteristics are clarified.The depositional models are established then.According to the different source supply modes,there are three types of gravity flow deposits in continental faulted basins: exogenous flood type gravity flow deposits,endogenous slump type gravity flow deposits,and both exogenous and endogenous control gravity flow and collapse type gravity flow deposits.According to the different tectonic styles,the types of gravity flow deposits are different: slump gravity flow deposits are mainly developed in the steep slope-deep sag area,flood gravity flow deposits are mainly developed in the axial slope-gentle slope area,and slump gravity flow deposits are mainly formed in the gentle slope-deep sag area.Gravity flow deposits in continental faulted basins are mainly generated around the maximum lake flood surface,at the end of lacustrine transgression zone and in the high zone.The characteristics and modes of gravity flow deposition were defined in this study.The slump gravity flow deposition was divided into sliding microfacies,slump microfacies,debris flow microfacies and turbidity current microfacies,and further divided into sliding microfacies,slump microfacies,clastic flow channel microfacies,clastic flow tongue microfacies and turbidity flow sheet microfacies.Flood-type gravity current deposits are divided into proximal subfacies,central subfacies and distal subfacies,and further divided into main channel microfacies,branch channel microfacies and lobular microfacies.Slump-density flow hybrid proximal gravity flow deposits mainly develop mixed subfacies,middle Asia and distal mix subfacies,further-slump microfacies can be divided into the main channel and main channel debris flow microfacies,branch channel slump microfacies,branch channel-debris flow microfacies,the branch channel-turbidity current sheet sand microfacies and lobes body-turbidity current sheet sand microfacies.To continental downfaulted basin ramp-deep depression area of gravity flow deposits configuration is divided into three types and eight sub-classes.The 3 types are single sand body internal configuration,different sand bodies combination configuration and sequence stratigraphy.The internal configuration of a single sand body contains three levels,respectively,for a single grain layer unit,a single grain layer group and single bedding units.There are two grades of different sand body combinations,namely,single genetic sand body unit and composite sand body unit.Sequence stratigraphic architecture consists of three grades,which are parasequence unit,parasequence group unit and sequence unit.The sedimentary architecture models of different genetic types of gravity flow are established.They are the slump type,the gravity flow configuration model and the combination of slump and gravity flow.In this study,level 3 and level 4 configuration unit distribution rule and the style are clarified.The vertical configuration style mainly includes positive rhythm,the rhythm,homogeneous rhythm type and compound type of rhythm.The profile configuration style mainly includes vertical superimposed type,vertical type,vertical fault fold,lateral superposed,lateral transfer and lateral separation.The surface configuration style mainly includes isolation type,half connected and connected.