High-Stand Fan Deltas: Exploration Targets in Indian Petroliferous Half-Graben Rift-Basins

Ramakrishna Madabhushi¹, Welborn W. Momin¹, Shaila Dhar Saikia¹, Venkateswara Rao Chinta¹, and Asim Samanta^2
1Cauvery Basin, ONGC, Chennai, India
²CEWELL, ONGC, Baroda, India

High-stand deltas form major hydrocarbon reservoirs world over. Half-graben rift basins representing fault-controlled short siliciclastic depositional regimes comprise the (high-stand) fan deltas as the principal reservoir facies within idealised petroleum systems. Based on sequence stratigraphic determinations in two Indian petroliferous rift basins - Cambay and Cauvery basins, lower order sequences/cycles with high-stand fan deltas ssem to be principal targets in hydrocarbon exploration.

Most hydrocarbon reservoirs in Cambay basin represent the high-stand coarser clastic sequences, while transgressive and the low-stand sequences were met with limited success. Short-distance variation of reservoir facies and their stratigraphic disposition reveals the presence of lower order sequences with structure controlled high-stand reservoir facies within known stratigraphic sections - U.Eocene Kalol Formation / Eocene Pay, Oligocene Gas pay, L.Eocene Kadi Formation,Basal Miocene reservoir facies and Palaeocene reservoirs within Olpad formation. Distribution of oil and gas fields in Cambay Basin also unravels three probably non-coincidental alignments or fairways - the western ‘prolific’ Miocene oil pays, the central Oligocene gas play and the Eastern Eocene (oil) play - between the Western Offshore Basin and the Cambay Basin.

In Cauvery Basin, fault-controlled, high-stand fan deltas within lower order sequences at U.Creataceous Nannilam-, L.Cretaceous Andimadam- and Bhuvanagiri- and L.Tertiary Kamalapuram- stratigraphic levels are interesting from hydrocarbon exploration standpoint. Most of the ‘anticlinal crests’ drilled with little success may represent the transgressive sytems tracts.

Exploration success lies in pursuing of high-stand fan deltas especially within the hydrocarbon fairways in the two petroliferous basins under discussion.

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