Petrophysical analysis of well logs for reservoir evaluation: a case study of “Kadanwari” gas field, middle Indus basin, Pakistan

Abstract

Our study focuses on the interpretation of wire-line logs to evaluate the hydrocarbons potential of sandstone reservoir in the Kadanwari gas field, Sindh, Pakistan. We have considered wire-line logs of four drilled wells (K-01, K-03, K-10, and K-11) in the research area and interpreted 13 reservoir zones. Analytical reservoir analysis includes the shale content (V_sh), effective porosity (Ø_eff), hydrocarbon and water saturation (S_hc and S_w), and net pay thickness variations. Hydrocarbon-bearing zone characterized by high resistivity values, porosity high, permeability high, saturation of water low, and less V_sh suggest clean sand. The petrophysical analysis revealed the hydrocarbon potential of lower Goru sandstone packages at different levels (2886–3797 m). The petrophysical parameters of sub-reservoirs were carefully analyzed which are ranked as good quality sand reservoirs with average effective porosities ranging from 0.11–0.44%, average water saturation ranging from 0.18–0.45%, hydrocarbon saturation averaging between 0.59–0.86%, and permeability ranging from 10.539 to 477.76 m Darcy. Water saturation for heterogeneous shaly sand reservoirs was successfully tested by Indonesian model which suggests that S_w in each well is fewer than 60% therefore over all the region bearing good quality of hydrocarbon potential of the targeted formation and selected zones. The vertical and horizontal variations of reservoir parameters are studied through constructing the litho-saturation cross-plots and isoparametric maps of the petrophysical parameters, respectively. The isoparametric maps help to visualize the geographical distribution of reservoir configuration in the subsurface. The petrophysical estimates of this study appraise the national conventional fuel treasure of lower Goru formation in Kadanwari gas fields and suggest new prospects to drill more wells on the central portion of the southwestern part of the study area. The neighboring area to the south of Kadanwari-01 is economically viable for hydrocarbon exploration. The northeastern side of the study area is avoided due to the high concentration of water and excessive shale content.