THE WINLAND r35 FOR PERMEABILITY ASSESSMENT IN LOWER GITA MEMBER RESERVOIR, TALANG AKAR FORMATION, FIELD “X”, ASRI BASIN

Abstract

Sedimentation process creates heterogeneity in the physical properties of reservoir rock. Rock typing is a method to determine the physical properties of rocks easier, especially for permeability. One of the methods in rock typing analyses is Winland r35. In this method, pore throat size parameter is calculated and can be grouped as rock types using hierarchical cluster analyses with the ward's algorithm. The quality of rock type results can be observed by the regression value (R) from trend line of porosity and permeability plots. The high regression value is considered as good rock type result and vice versa. Another way to verify rock type result is by using reservoir simulation of single well model. Permeability calculation by trendline equation will be input to single well model with other supporting data from petrophysics and pressure transient analyses (PTA). Reservoir model with good rock type will match the flow rate and bottom hole pressure aligned to drill stem test (DST) data. The results are four rock types
formed by the Winland r35 method, showing low regression (R²) value with quite different permeability calculation from the core permeability. Based on the matching to the oil rate and bottom hole pressure from the drill stem test (DST) data, this result is considered quite good and this method can still be applied to the lower Gita reservoir.