Reservoir configuration characteristics of fan delta front and its control effect on reservoir quality:a case study of P Ⅰ Oil Group in D Oilfield of Chad
The P Ⅰ Oil Group reservoir in D Oilfield,Bongor Basin,Chad,is a fan delta front deposit,which has the characteristics of near-source rapid accumulation,coarse detrital particles and complex sand-body contact relationship.Based on core,logging,seismic and development dynamic data,the lithofacies and combination types in the study area are divided,and the types and characteristics of single sand body configuration are identified.The spatial combination styles of different configuration units are analyzed,and the fan-delta front configuration models and their evolution characteristics with the base level are established to discuss the control effect of single sand body configuration on reservoir quality.The results show that the study area is a fan delta front deposit,with 10 lithofacies,five lithofacies as-sociations and four main configurational unit types.There are four types of lateral splicing styles of sand bodies,and the vertical contact types of single sand bodies can be divided into three categories:cut and overlap type,superimposed type,isolated type,with a total of 10 sub-categories of vertical contact types.In the period of long-term base level rising,the vertical superposition relationship of single sand body configuration changes from cut and overlap type to superimposed type and finally to isolated type,and the development scale of sand body shrinks.The porosity and permeability characteristics of differ-ent configuration units are obviously different,and the physical properties of underwater distributary channels are the best,with the mean porosity and permeability of 21.31％and 1 276.92×10 μm2,re-spectively.The superposition pattern of single sand bodies and the location and deposition rhythm of the sand body in a single configuration obviously control the heterogeneity of reservoir physical properties,and the physical properties change from the main body in the middle of the channel corresponding to the box curve rhythm to the two sides corresponding to the bell curve rhythm.The superimposed contact sand body is more heterogeneous than the cut and overlap contact sand body.The results can provide reference for the exploration and development and well pattern deployment of D Oilfield in Chad and similar fields.
fan delta frontconfigurational unitsuperposition stylereservoir qualityBongor BasinD Oilfield in Chad
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