Petrophysical relationship for density prediction using Vp & Vs in Meyal oilfield, Potwar sub-basin, Pakistan

Abstract

Conventional petrophysical investigations are based on P-wave seismic velocity analysis to predict density information, while ignoring the important S-wave velocity. This study is based on S-wave velocity analysis of density estimation of Meyal Oil Field (Potwar Plateau, Pakistan), which reveals a very high correlation (R = 0.87) between predicted and actual density. Since the availability of S-wave velocity (Vs) data increases, it's highly appreciable to take into account the contribution of Vs in improvement of density estimates. This investigation only focuses on driving new constants (a = 1.92 and b = 0.186) for Gardner's relationship to estimate density of pure carbonates (Vsh< 10%) in the study area, where the traditional model gave poorer density predictions. The proposed empirical expression with locally extracted unknowns from well log data proved its ability in terms of density prediction (showing very close agreement with measured densities) and best fitting the datasets at low as well as high density values when compared with Gardner's equation. Based on our analysis, the exploratory study neither intends to replace the well established density estimation models nor to extend information over what information can possibly be extractable from Vp. However, our research does stimulate the growing use of Vs and importance of local unknown constants especially in carbonates reservoir interval to avoid misuse of most widely used Gardner relation in all geological settings. Keywords: Shale, Gardner, Potwar, Carbonates, S-Waves