Geology and Geocellular Modelling of a Saline Aquifer: From Integration of Hydrogeology and Petroleum Geology in a Study of the Thumbli Formation, Rajasthan, North-West India

David L. Sturrock¹, Ashok Kumar¹, Anurag Pattnaik¹, Nigel Banks², and Michael Price^3
1Cairn India Limited, Gurgaon, India
²Banks Geoscience, Oxford, United Kingdom
³Water Management Consultants (A Schlumberger Company), Shrewsbury, United Kingdom

The Mangala Oil Field was discovered by Cairn Energy in the Barmer Basin, Rajasthan, NW India in January 2004. It was apparent from an early stage of field appraisal that large amounts of water would be required to inject into the oil reservoir to maintain pressure and increase the recovery of the oil. Fresh water is scarce in Rajasthan due to desert climatic conditions and a study was conducted to identify a subsurface source of saline water which could be used as injection water during field production.

The Barmer Basin is a narrow NNW-SSE oriented rift basin, with normal fault growth occurring mainly during the Palaeocene to Eocene. The basin fill contains two sandstone units with excellent reservoir quality: the Palaeocene Fatehgarh Formation, which is the reservoir for the Mangala Oil Field, and the Eocene Thumbli Formation. A regional study of the Thumbli Formation using well and seismic data from petroleum exploration revealed the presence of large volumes of saline water in reservoirs approximately twenty kilometres south of the Mangala Field. An extensive drilling and testing programme of this saline aquifer has been conducted and a detailed geocellular model has been constructed. Using hydrogeological and petroleum geological techniques, this geocellular model has been used to design a water source field. This study of the Thumbli aquifer, incorporating extensive test data and continuous monitoring, has clearly shown that the volume of saline water planned to be extracted from the Thumbli Formation for Mangala Field development has only a minimal effect on the regional pressure and salinity distribution of the formation due to the extremely large reservoir volume of saline water in the Thumbli Formation in the Barmer Basin.

Presentation GEO India Expo XXI, Noida, New Delhi, India 2008©AAPG Search and Discovery