UNCONVENTIONAL RESERVOIR CHARACTERIZATION BY UTILIZING SEISMIC AND WELL DATA: A CASE STUDY FROM THE TALHAR SHALE, LOWER INDUS BASIN, PAKISTAN

Abstract

Shale gas deposits have emerged as an important energy source with growing demand during the previous decade. TOC is a significant component for unconventional reservoirs that is often quantified using conventional approaches, including geochemical lab analysis of side wall cores and cuttings of formations. However, such research methods produce data in a non-continuous and time-consuming manner. High resolution and continuous information acquired from well logs can help to solve this challenge. To estimate TOC from well logs, many approaches has been attempted. Among these approaches, four have been selected to quantify TOC in the current study: Density Log, Spectral Gamma-Ray Log, Delta logR, and Multivariate Fitting. Apart from TOC other Geochemical parameters LMI (log-based Maturity index), LOM (log-based Organic Maturity), BI (Brittleness Index), and Kerogen Volume were estimated and computed using well-based characterization. LMI estimated by well log data 0.67, LOM estimated by well data 10.2, Brittleness Index 0.5 and volume of kerogen between 4 to 5% and TOC was calculated using Passey's method was 1to2%, Schmoker's, Multivariant technique up to 2 to 3 percent TOC, while Spectral Gamma Ray log provides average 1 to 1.5 TOC in the formation. Calculated results from well data show promising results. For analyzing the spatial distribution of TOC, the Hampson-Russel software was used for seismic inversion, which resulted in impedance volume estimate. The interpreted seismic cube was used to perform model-based inversion of supplied 3D seismic data. Tajjal-01 seismic to well tie technique yielded a statistical wavelet. The wavelet is convolved with the well's reflectivity series roughly approximates the proximal seismic traces. The available seismic data, well data, calculated TOC, and interpreted horizons data were used as input for inversion. The software found an excellent 99.96% correlation in the cross plot between computed TOC and predicted TOC.