Stratigraphy and reservoir quality of the turbidite deposits, western sag,udBohai bay, China P.R.

摘要

Stratigraphic and subtle reservoirs such as pinchouts, sand lenses and unconformities have been discoveredudin Bohai basin. These reservoirs occur in sub-basins and sag structures called depressions. A prolificuddepression is the Liaohe depression that has been filled with rapidly changing mixed alluvial fan depositudof the Cenozoic age. Attempts made at recovering residual hydrocarbon from the subtle reservoir haveudnecessitated the re-evaluation of available data to characterize and model the prolific Shahejie Formationudturbidite deposit occurring as pinchouts and sand lenses for hydrocarbon assessment, reservoir qualityudand possible recovery through enhanced methods. Methods employed covered well logs analysis, clusteringudanalysis for electrofacies and fuzzy logic analysis to predict missing log sections. Stratigraphic andudstructural analysis was done on SEGY 3D seismic volume after seismic to well tie. Stochastic simulationudwas done on both discrete and continuous upscaled data. This made it possible to correctly locate andudlaterally track identified reservoir formation on seismic data. Petrophysical parameters such as porosityudand permeability were modeled with result of clustering analysis. Result shows that electrofacies convergedudon 2 rock classes. The area is characterized by the presence of interbeded sand-shale blanket formationsudserving as reservoir and seal bodies. The reservoir quality of the formations as seen on theudpetrophysical analysis done is replicated in simulation volume results. Reservoir rocks have porosityudbetween 0.1 and 0.25, permeability between 1 and 2mD and hydrocarbon saturation as high as 89%.udLithofacies are observed to be laterally inconsistent, sub-parallel to dipping and occurring as porousudand permeable continuous beds or pinchouts hosting hydrocarbon. The stochastic stratigraphic modeluddepicts rock units in associations that are synsedimentary. The prevalent configuration gotten fromudthe model gave an insight into exploring and developing the field for enhanced oil recovery of the heavyudhydrocarbon of this area.