Comparison between conventional and high-resolution measurements for unlocking the thin laminated potential reservoir, a case study

Abstract

In Low resistivity low contrast (LRLC), also known as low resistivity pay (LRP), one of the factors is, the existence of alternating thin sedimentary layers of various rock types in hydrocarbon reservoirs, commonly consist of sandstone, siltstone and claystone and have been widely reported today. This phenomenon causes the potential intervals to be misinterpreted as non-hydrocarbon bearing zone due to its ability to reduce the measured apparent resistivity which result in overestimated water saturation calculation and due to its low contrast, in comparison with water bearing interval, this phenomenon always make well analyst to by passed this interval. As a result, from falsified measured resistivity, the final reserves volume tends to be underestimated. A huge number of studies have proven this kind of interval able to produce oil with very low water-cut therefore this paper would like to present the case study of solving this complex lithology by using sophisticated petrophysical modeling with a combination of Thomas-Stieber plot. Measured vertical (Rv) and horizontal (Rh) resistivity is available for this study and will be used as comparison. In general, this paper will present two case studies for final saturation computation, a) The sand resistivity will be estimated through inversion using measured resistivity anisotropy (Rv - Rh), b) The sand resistivity is reconstruct based on identified volume fraction of clay, whereas the shale resistivity estimated from conventional resistivity (RDEEP). Both of the cases will be calibrated using measured saturation from core by using Dean-Stark technique. Selected interval in this study (X1 zone) is a proven oil interval with a standard volume production rate 698 bbl/day. The final comparison of saturation computed using measured resistivity anisotropy yield a high correlation in contrast, the inversion using conventional resistivity yields less correlation with saturation from core. Nonetheless, by comparing with conventional computed saturation i.e. Waxman Smith, the final saturation of these two cases is significantly increased and unmasked the hydrocarbon-bearing interval. Therefore, case b indicates the best approach to be used whenever the advance measured resistivity anisotropy is unavailable.