Unlocking India's Tight Reservoirs with Rock Physics, a Case Study in the Krishna-Godavari Basin, India

KG-ONN-2003/1 is an onshore block located in the south-western part of the Krishna-Godavari Basin, India (Figure 1). The block was awarded to the consortium of Cairn India and ONGC with Cairn India as the Operator. The JV made two discoveries in the block in early Cretaceous sandstone sequences, the Raghavapuram Formation sandstones and the deeper Golapalli Formation sandstones. The first discovery well-A was drilled based on 3D seismic data in year 2010. Well-A encountered both the Raghavapuram Formation and the Golapalli Formation sandstone reservoir units at depths of shallower than 4000m. Both these Cretaceous sandstone packages are very low permeability. Petrography of core material coupled with routine core analysis demonstrates that a combination of mechanical compaction and clay authigenesis has dramatically reduced porosities and permeability. The main objective of the rock physics studies reported here was to derive a methodology to map the extent of the reservoir in order to reduce the sub-surface uncertainties for the forthcoming field appraisal campaign. This paper illustrates why rock characterisation studies should be integral within field development, and how integration of studies which include rock physics, petrophysics, seismic and geological data can help fully delineate reservoir and non-reservoir zones.