Dhirubhai Discovery—Largest Discovery in 2002

Ross, Steven P.¹, Ravi Bastia², William Leslie¹, R. J. Singh², Neeraj Sinha², Ashwani Sharma² (1) Reliance Exploration and Production, Plano, TX (2) Reliance Industries Limited, Navi Mumbai, India

Reliance Exploration and Production discovered Dhirubhai A & B, the largest new field of 2002, in deep water (1000+ m) off the Godavari Delta, east coast India. Estimated recov­erable reserves from four wells are seven to ten TCF of biogenic gas. The field is a Pliocene structural/stratigraphic trap, or compaction anticline. An extensive marine, deep-water chan­nel system was deposited during lowstand conditions. Two distinct channel types form the reservoir facies. One channel type is fixed, hundreds of meters in thickness, and contains coarse- to fine-grained sandstone. Sandstones in the second channel type are thinner, tens of meters thick, and finer grained. While active, the latter channels migrated southward .

The Dhirubhai fields were discovered using a coarse grid of 2D seismic data and a focused 3D exploration survey. Channel-belt reservoirs are imaged as amplitude anomalies, whereas levees show no unique amplitude character and are thin, poor-quality reservoirs. High-impedance corresponds to reservoirs of coarse-grained sandstone with rare conglom­erate. Low-impedance exemplifies two reservoir types: 1) thick, well-sorted, coarse- to medium-grained sandstone; and 2) thick sections of interbedded, well-sorted, medium- to fine-grained sandstone and shale.

Over 100 km2 of the channel system is charged. Channel belts served as the carrier beds as well as, the reservoir. Slope shales form the updip seal and the top seal consists of fine­grained Pliocene highstand deposits.