Reservoir Characterization And 3D Geological Modeling Of Gravity Flow Channel

Reservoir PI of Block N in Great Baobab Oilfield is located in the north of Baobab Sag,northern slope of Bongor Basin.The reservoir is running out of natural energy now and at the start water injection stage.The former geological knowledge of reservoir and 3D geological model can't meet the needs of oilfield development in current stage.To break the present condition,the writer established stratigraphic framework and divided PI oil bed group into 5 sand groups,using the rich data of seismic,well logging,mud logging,cores and chemical examination,based on the principle of cycle correlation and hierarchical control and according to the results of regional stratigraphic correlation and division.According to the analysis of lithological,electronical and geochemical facies marker,the writer identified the facies of this area.In the stratigraphic framework,the writer did the analysis of microfacies in individual well,section and plane,figured out the distribution of microfacies in each sand group,further more concluded the model of gravity flow channel in this area.Based on the analysis of mircofacies,microcosmic characteristics,macroscopic characteristics,heterogeneity and developmental factors were studied in this area.According to the above conclusions,a 3D geological model with a grid size of 25m×25m×0.5m was established based on the data of well drilling,well logging,horizons,facies and attributes by deterministic and stochastic modeling method.By comprehensive study of this area,the writer got some conclusions as the following.The resources are from the northern uplift.The sedimentary environment of gravity flow channel in this area is fault basin and the channel can be divided into center channel,marginal sand and flooded margin.The lithology of this area is mainly sandstone and gravel sandstone with low maturity,poor sorting and bad rounding.Occasionally flaser bedding,graded bedding and massive bedding are figured out in those sandstones.The development of reservoir is controlled by reverse tectonic movement and the sedimentary environment.The compression and dissolution in later period are the main factors of the changing porosity and permeability of the reservoir.