Multi-Scale Volcanic Facies Characterization of Deccan Volcanic Complex in the Barmer Basin of Rajasthan: Implication for Exploration in a Flood Basalt Province

Abstract

The Barmer basin marks the northern limit of the Western Indian Rift system. It is a prolific hydrocarbon province with 38 discoveries and 6.4 BBOE in place. Cairn has discovered 3 fields in Deccan age volcanics, with over 700 MMBOIP. Raageshwari Deep Gas is the largest field, producing approximately 40 MMCFD of gas from a large rift block. The reservoirs are very similar to Deccan volcanic outcrops exposed in western and central India, and form the northernmost limit. We map two seismic facies within the volcanic unit. The lowermost transparent unit is over 1000 m thick and unconformably overlies deeper reflections. It consists of very thin, compound braided and anastomosing lobes up to a few meters in thickness but cover broad areas. The upper reflective unit varies from 0-700 meters in thickness. It is dominated by much thicker (10-50 m) simple tabular basalt flows and pyroclastics. Porosity development and reservoir distribution are variable. The upper simple lava flows consist of a basal zone, a middle dense core with low vesicular porosity, and an upper highly porous (vesicular, brecciated/fractured) crust. The lower compound flows and ignimbrites have porosity controlled mainly by the amount of syn-depositional welding. Future volcanic hydrocarbon exploration requires an understanding of the emplacement processes, internal architectures, and controls on rock properties of the lava flows. We characterize the volcanic complex across the Barmer basin integrating seismic, well logs and core data. Learnings derived from this study can be applied widely to other basin and help delineate more resources with the Barmer Basin itself.

AAPG Datapages/Search and Discovery Article #90332 © 2018 AAPG International Conference and Exhibition, Cape Town, South Africa, November 4-11, 2018