Successful infill drilling campaign using fit-for-purpose seismic technologies doubles oil production and extends field life at Lakshmi Field, Gulf of Cambay, western India
The offshore Lakshmi Field, located in the southern part of Cambay Basin in the CB/OS-2 block in western India, is a success story of transitioning from a plateauing gas field to an oil-producing asset. Hydrocarbons sourced from Hazira Shale at Lakshmi Field are trapped in inversion-related four-way dip closures. The reservoirs are within the Miocene-age Tarkeshwar and overlying Babaguru formations; both have excellent reservoir quality with porosity ranging from 25% to 30% and Darcy-scale permeability. During the initial exploration stage, presence of oil was established in the deeper lower Tarkeshwar sands. However, the full oil potential of the field was not realized in the early stage of development due to difficulty in characterizing laterally and vertically discontinuous thin sands. These sands are often not detected in conventional 3D seismic data due to severe attenuation-related masking by overlying thick gas sands. Given the uncertainty of the oil potential of the field, a revised look using advanced seismic technologies was undertaken to drive a new infill drilling campaign. Seismic reprocessing using Q-tomographic inversion was performed to address the gas-attenuation problem, resulting in an improved seismic image. The new seismic data enabled characterization of thin reservoir sands using analytical techniques such as spectral decomposition and amplitude-variation-with-offset (AVO) attribute analysis. An integrated reservoir-characterization approach using field analogs, interpretation within a sequence stratigraphic framework, concepts of seismic geomorphology, and quantitative seismic analysis helped identify optimal areas of the sand fairway for infill well placement. Several infill wells have since been drilled that encountered good pay zones, validating the integrated approach. This successful campaign doubled oil production at Lakshmi and extended the field life by increasing reserves.