Time Lapse Seismic to Assess Blowout Effects - A Case Study from Upper Assam Basin, India

The following study utilizes 3D seismic data from 1995 and 2008 to investigate blow-out related seismic amplitude changes in the Eocene reservoirs of the field. Differences in reflection amplitudes and other attributes in these data vintages are used to interpret and constrain the spatial distribution of reservoir properties and probe into insight of the depletion process due to blow-out. 4D seismic data is considered as a relative measure of change in the reservoir and it has to be suitably calibrated and normalized. NRMS data is used to remove more anomalous measurements. NRMS amplitudes can be interpreted as a fractional change in amplitude relative to the original. Production profiles for several wells and seismic based attributes align towards the results predicted through NRMS amplitude differences. This study normalizes the two seismic surveys acquired in two vintages and interprets the amplitude differences, as well as correlating the seismic volumes thereby identifying the regions which may be affected by the blowout. On the process of updating the reservoir by calibrating 4D data of different vintages has given a better understanding of changes to the reservoir and also reduces risk in forecasting, leading to better decisions about reservoir maintenance and infill well targeting.