Stratigraphy and reservoir quality of the turbidite deposits, western sag, Bohai bay, China P.R.
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Elsevier
Abstract
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Stratigraphic and subtle reservoirs such as pinchouts, sand lenses and unconformities have been discovered
in Bohai basin. These reservoirs occur in sub-basins and sag structures called depressions. A prolific
depression is the Liaohe depression that has been filled with rapidly changing mixed alluvial fan deposit
of the Cenozoic age. Attempts made at recovering residual hydrocarbon from the subtle reservoir have
necessitated the re-evaluation of available data to characterize and model the prolific Shahejie Formation
turbidite deposit occurring as pinchouts and sand lenses for hydrocarbon assessment, reservoir quality
and possible recovery through enhanced methods. Methods employed covered well logs analysis, clustering
analysis for electrofacies and fuzzy logic analysis to predict missing log sections. Stratigraphic and
structural analysis was done on SEGY 3D seismic volume after seismic to well tie. Stochastic simulation
was done on both discrete and continuous upscaled data. This made it possible to correctly locate and
laterally track identified reservoir formation on seismic data. Petrophysical parameters such as porosity
and permeability were modeled with result of clustering analysis. Result shows that electrofacies converged
on 2 rock classes. The area is characterized by the presence of interbeded sand-shale blanket formations
serving as reservoir and seal bodies. The reservoir quality of the formations as seen on the
petrophysical analysis done is replicated in simulation volume results. Reservoir rocks have porosity
between 0.1 and 0.25, permeability between 1 and 2mD and hydrocarbon saturation as high as 89%.
Lithofacies are observed to be laterally inconsistent, sub-parallel to dipping and occurring as porous
and permeable continuous beds or pinchouts hosting hydrocarbon. The stochastic stratigraphic model
depicts rock units in associations that are synsedimentary. The prevalent configuration gotten from
the model gave an insight into exploring and developing the field for enhanced oil recovery of the heavy
hydrocarbon of this area.
Keywords
TA Engineering (General). Civil engineering (General), TP Chemical technology