The Mangala Field, Rajasthan, India: A Story of Rapidly Advancing Subsurface Understanding in Readiness for Development

Yashwant Singh Rathore, B. Ananthakrishnan, Mark Flynn, and Paul Michael Compton
Cairn Energy India Pty Ltd, Chennai, India

Cairn Energy's recent exploration of the Barmer Basin has resulted in several significant oil and gas discoveries, highlighting its potential as an emerging oil province. In January 2004 the company made the billion barrel Mangala discovery with the 15th well in the basin. Tests flowed at rates up to 2837 bpd of 23.7-29.4 API waxy oil. The reservoir comprises high quality, high net/gross fluvial sands of possibly Palaeocene age belonging to the Fatehgarh Group.

The discovery was appraised by further 2D seismic and 6 additional wells from which were collected extensive core, log and test data. Sufficient confidence in STOIIP and potential reserves was gained that commerciality was approved on 15th October 2004, only 8½ months after discovery. A 3D seismic survey was acquired, and a fast-track volume of processed data was interpreted in November and December 2004, which has resulted in a robust model of the field's geology.

A lithostratigraphic framework for the Fatehgarh Group has been constructed, despite problems of correlation within fluvial sequences deposited in semi-arid environments. Core and image log studies have been used to describe the sedimentary architecture of the reservoir, from which an object-based reservoir model has been constructed. This model provides the basis for a predictive dynamic model of the field, used as an essential part of field development planning.

The high level of subsurface knowledge of the Mangala Field, achieved so quickly, has enabled the Field Development Plan to be submitted to the Indian Government on 4th October 2005, less than 2 years after discovery.