f Saturation-Height Modeling of Bozova Oil Field

The capillary-saturation function plays an important role in describing fluid distribution and modeling flow in reservoir simulation. In this study, saturation height functions have been developed as part of an integrated petrophysical analysis of an oil field. Bozova Field is an oil field located in the Southeast Turkey. From the discovery of the field in 1995 to date, the production is made from a Maastrichtien age bioclastic limestone facies called Reservoir Level with approximately 18 % porosity and 27-40 m thickness (Figure 1). In this relatively mature field, a simulation study is realized to predict the field’s response to a prospective water-flooding program. To prepare a representative data to be used in the simulation model, log derived water saturation calculations are revised by considering the produced water values and capillary pressure measurements coming from special core analyses. In this case study, model used to calculate water saturation from logs include the deterministic Archie Equation. This equation is appropriate knowing the reservoir consists of clean bioclastic limestone facies. However, the resistivity logs are unable to give a proper idea about water saturation distribution respect to depth because of the fact that, they have almost same range of readings along the reservoir section. Using Archie model with a fixed value for water resistivity (Rw) causes mismatch between simulation with real water production history. This problem has led us to reevaluate the logs with the observed salinity data from the wells. After applying this correction, saturation height models are developed from core capillary pressure (Pc) data to calculate water saturation vs. depth, which is independent of logs. First step of the procedure is to model capillary pressure measurements using different methods, namely, Brooks-Corey, Lambda, Thomeer and Leverett-J functions. After this stage, each of these models is used to estimate water saturation along all the wells. Eventually, the best fit between log derived saturations with the capillary derived saturations is achieved using the Leverett-J Function model (Figure 2). The results show that, the saturation height functions provided more accurate water saturation values in Bozova oil field and they have mostly overcome uncertainties associated with log interpretation by use of Archie model. Newly created water saturation logs are used in the water saturation distribution of the geological model to calculate oil-in-place volume (Figure 3). This distribution shows better agreement with the production data of the field and with the oil-in place calculation made in the simulation stage. Linking the core capillary pressure data with well log analyses has enhanced the water saturation estimations.