Patent ID: 11914091

Abstract:
A method for fluid identification (water, oil, gas or CO2) and saturation estimation in subsurface rock formations using the prestack inverted seismic data by calculating the target fluid saturation (Sfl)(114) in a reservoir given the magnitude obtained from the P- to S-wave velocity ratio (Vp/Vs) (103), and acoustic impedance (AI) (102) extracted from the seismic data inversion, comprising the following steps: a) obtaining wireline log data within a zone of interest in a nearby well (101) and determining the suitable cementation and mineralogy factors by calibrating the background water-bearing sand trend with the reference 0% (or 0 fraction) Sfl curve onto the acoustic impedance-Vp/Vs ratio plane (110), b) calibrating Sfl computed from the acoustic impedance-Vp/Vs ratio curves with Sfl obtained from a conventional method by iterating P-wave velocity (Vpfl) and density (ρfl) of the target fluid (111), c) obtaining inverted seismic data in the form of Acoustic Impedance (AI) (102) and Vp/Vs ratio (103) cubes, and d) calculating the target fluid saturation using the calibrated rock physics model inputting the obtained parameters from model calibration (cementation factor, mineralogy factor, density and P-wave velocity of the target fluid) along with inverted Vp/Vs ratio and acoustic impedance cubes data (113), resulting in a Sfl cube (114).