Feasibility Study for Seismic Monitoring of Gas Injection

Abstract

Abstract In this study, seismic monitoring of injected gas in a carbonate reservoir was investigated using multidisciplinary approach which consisted of geological/reservoir modeling, reservoir flow simulation, rock physics and seismic modeling. A case-study was conducted over the Lower Cretaceous carbonate reservoir offshore Abu Dhabi. The gas saturation and reservoir pressure data were obtained from the reservoir flow simulation. The velocity data of dry rock samples under the various conditions were also obtained from rock physics study. These outputs were converted to the velocity model using Gassmann 's equation. The calculated velocity from Gassmann's equation is well correlated with velocity from laboratory measurements. Therefore we can confirm that the Gassmann's equation is applicable to estimate the velocity of the gas saturated reservoir rock. Based on the velocity model, synthetic seismic sections before and after gas injection were constructed in order to verify the influence of gas flood. As the results, amplitude difference between the two synthetic seismograms was observed at top and bottom reflectors of the reservoir zone. This amplitude variation is caused by both gas saturation change and pressure change. Although further investigation is needed to detect the cause of the variation, this study indicates the possibility of seismic reservoir monitoring