Source Rock Characteristics of Petroleum System in the Ganesha Discovery, Cauvery Offshore Basin, India

Jogendra Nath Sahu, Debashish Biswas, Satya Sai, Anantha Krishna, and Vishnu Vardhan
Hardy Exploration and Production (India) Inc, Chennai, India

The Ganesha prospect is located in the Ariyalur Pondicherry sub-basin of the Cauvery basin, East Coast of India. This sub-basin is bound by the Porto Novo high to the southeast and the Indian Craton to the northwest. The sub basin has a post rift Cretaceous section of 2500m-3500m thickness. Seismically the prospect is sitting on the Cretaceous palaeo slope. The sands associated with this prospect are low stand sand bodies overlain by transgressive shale of Upper Cretaceous age. The exploratory Fan A-1 well (Ganesha-1) was drilled to test the hydrocarbon potential of these Cretaceous slope fan prospects. The tested reservoir sands within Bhuvanagiri Formation of Turonian age produced hydrocarbons. The study evaluates the hydrocarbon potential of the source kitchen in offshore Ariyalur - Pondicherry sub basin based on the detailed geochemical evaluation of more than 50 rock extracts and 2 oil samples from Fan A-1 well and maturity modeling along with other available wells in this part.
Studies carried out on the well cutting samples of Sattapadi (Cenomanian) and Kudavasal shales (Santonain to Coniacian) indicate good organic enrichment, with fair hydrocarbon generation potentials. Isotope and Biomarker studies indicate terrestrially dominated organic source facies. The maturation history shows that the maturation of organic matter started from 90 Ma. Based on the modeling studies the predicted volumes expelled from a source kitchen of 1 km2 area with a source 100 m thick, vary between 1.8 and 2.0 million barrels of oil and gas at a minimum to 6.6 and 6.0 million barrels of oil and gas at a maximum, while with the same source in deeper parts the predicted volumes increase to 1.5 and 7.2 million barrels of oil and gas at a minimum and 13.7 and 17.8 million barrels at a maximum.