An improved technique for modeling initial reservoir hydrocarbon saturation distributions: applications in Illinois (USA) Aux Vases oil reservoirs

• Published in: Journal of petroleum science & engineering Vol. 21; no. 3; pp. 143 - 152
• Main Authors: Udegbunam, Emmanuel, Amaefule, Jude O.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.11.1998; Elsevier Science
• Subjects: Applied sciences; Aux Vases Sandstone; Brooks–Corey capillary pressure interpretation; Characteristics of producing layers. Reservoir geology. In situ fluids; Crude oil, natural gas and petroleum products; Crude oil, natural gas, oil shales producing equipements and methods; Energy; Exact sciences and technology; flow units; Fuels; oil saturation; Prospecting and production of crude oil, natural gas, oil shales and tar sands; United States; North America; Illinois; America; Brooks–Corey capillary pressure interpretation; oil saturation; flow units; Aux Vases Sandstone; Three dimensional model; Reservoir rock; Saturation; Oil field; Capillary pressure; Permeability; Porosity; Modeling; Sandstone; Petroleum; Original oil in place
• ISSN: 0920-4105; 1873-4715
• DOI: 10.1016/S0920-4105(98)00075-8

An improved technique for modeling the initial reservoir hydrocarbon saturation distributions is presented. In contrast to the Leverett J-function approach, this methodology (hereby termed flow-unit-derived initial oil saturation or FUSOI) determines the distributions of the initial oil saturations from a measure of the mean hydraulic radius, referred to as the flow zone indicator (FZI). FZI is derived from porosity and permeability data. In the FUSOI approach, capillary pressure parameters, S wir, P d, and λ, derived from the Brooks and Corey (1966) model [Brooks, R.H., Corey, A.T., 1966. Hydraulic properties of porous media, Hydrology Papers, Colorado State Univ., Ft. Collins, No. 3, March.], are correlated to the FZI. Subsequent applications of these parameters then permit the computation of improved hydrocarbon saturations as functions of FZI and height above the free water level (FWL). This technique has been successfully applied in the Mississippian Aux Vases Sandstone reservoirs of the Illinois Basin (USA). The Aux Vases Zeigler field (Franklin County, IL, USA) was selected for a field-wide validation of this FUSOI approach because of the availability of published studies. With the initial oil saturations determined on a depth-by-depth basis in cored wells, it was possible to geostatistically determine the three-dimensional (3-D) distributions of initial oil saturations in the Zeigler field. The original oil-in-place (OOIP), computed from the detailed initialization of the 3-D reservoir simulation model of the Zeigler field, was found to be within 5.6% of the result from a rigorous material balance method.