Three parameter calculation method for dry rock modulus and its application in feasibility evaluation of time-lapse seismic in G oilfield

Abstract

This study focuses on the offshore GE Oilfield with typical marine turbidite sandstone reservoirs and rich reserves. Improving production efficiency is crucial, and OBN-based TLS monitoring is the key means. However, the Macbeth method for calculating dry rock modulus in TLS rock physics theory has limited applicability. It's hard to accurately assess TLS performance in different porous reservoirs, severely restricting in-depth reservoir understanding. To address this issue, this study innovatively proposes a three-parameter dry rock modulus TP method that comprehensively considers porosity, density, and effective pressure, based on the petrophysical test data of 9 representative rock samples. Through rigorous comparative verification of data from low-, medium-, and high-porosity rock samples, the results show the TP method can be stably used under different porosity conditions, with broad universality and high prediction accuracy. It's incorporated into the Gassmann equation for G Oilfield TLS evaluation. A relational template of the CWI difference of 16 reservoir types considering porosity and shale content versus water saturation and pressure changes is constructed, and the corresponding changing laws are clarified. Meanwhile, factoring in bound water and residual oil saturation, a comparative analysis of TLS evaluations of four reservoir rock samples (R1, R2, R3, R4) is performed. It aims to assess the feasibility of TLS monitoring for each reservoir under different conditions, including maximum fluid replacement, single fluid replacement, and the combined impact of fluid replacement and pressure drop. The results will offer a more accurate and efficient method for G Oilfield's TLS monitoring, strongly supporting the enhancement of production efficiency.