Clastic Reservoirs Productivity Index Estimation with Well Log Data

Abstract

Abstract Fluid filtration and mass transfer processes description are the key issue of the geological modeling and oilfields development design for reservoirs with complex structure. The well log data interpretation results are the basis of reservoir characterization. The advanced application of the effective porosity value provides description of reservoir properties for dynamic (absolute, effective and relative permeabilities, capillary pressures, free fluids) reservoir simulation. The outcome values of effective porosity and clay swelling index are properties, which confidently reflect filtration reservoir parameters. It is stated that effective porosity determined with log data provides evaluation of relative/phase permeability values and hydrocarbon distribution in transition zones using capillary pressure models. The application of Buckley Leverett function for known effective permeability gives evaluation of oil share in production. It is established that effective porosity has strong correlation with productivity index for wide range of clastic reservoir rocks from different region. Thus, the determination of effective porosity from well logs is resulted in prediction of oil and water amounts in production. The effective porosity determination with log data is complex task, which could be solved with NMR log or conventional log data interpretation. Authors of stated work developed petrophysical models and appropriate algorithms (adaptive log data interpretation) for effective porosity determination based on adaptation to well logging tools metrology and reservoir conditions. These algorithms provide determination of effective porosity values with conventional well logs (spontaneous potential log, formation density log, gamma-ray log, neutron log and sonic log). Proposed models of capillary pressure and relative/phase permeabilities are used in dynamic reservoir properties prediction algorithms. Dynamic properties are transferred in digital geological and hydrodynamic models for reservoirdevelopment process simulation. The well log derived effective porosity is used for reservoir rocks productivity index prediction. Oil and water effective/relative permeabilities have close relation to effective and dynamic porosity and this fact provides determination of oil and water effective/relative permeabilities in reservoirs as well as oil and water amounts in production. Obtained results are applied for fluid filtration processes modeling and reservoir development technology design.