Integrated rock physics test and modelling to detect fluid changes in a carbonate reservoir: A case study from an Iranian oil field

The study performs fluid substitution and seismic modeling of an Iranian oil fields to validate Xu-Payne (2009) and Gassmann (1951) equations for carbonate reservoirs. Laboratory rock physics test and modelling are integrated in order to detect seismic response due to fluid changes in the target reservoirs. 13 core plugs from the target reservoir zones are tested in the laboratory. The Xu-Payne model is used to predict elastic logs. Then, Xu-Payne and Gassmann equations are used to build different reservoir scenarios for brine, oil and gas saturations. The fluid substitution results are compared and verified with the core measurements. This step is followed by forward modeling (generation of pre-stack seismic traces) based on the modeled saturation scenarios, and comparison of the modeled logs with the actual seismic response at the well location. The results of the fluid substitution confirm the applicability of the models to discriminate different fluid responses in the field. Moreover, this approach helps to identify the in-situ pore fluid within the carbonate field.