India's Hydrocarbon Outlook – 2022-2023

53 DGH: 3 DECADES OF UNLOCKING INDIA'S HYDROCARBON POTENTIAL followed by Deccan Trap volcanism. Phases of tectonic deformation in the Cenozoic are indicated by extensive unconformities. The basin was built with Pre-Cambrian basement overlain by Mesozoic sediments followed by Deccan traps. A thin cover of Neogene and Quaternary sediments occurs at the top. A number of volcanic plugs are present in the west and in the southeast. The Jurassic Lodhika Formation is composed of volcanic rocks and overlying Cretaceous sedimentary rocks are exposed over northeast part of the Saurashtra Peninsula and comprise the Lower Cretaceous Dhrangadhra and Wadhwan Formations. The Cenozoic consists dominantly of shallow-marine clays and limestones. Post-Trap carbonates and fine-grained clastics are considered to be prospective offshore targets. The drainage of Saurashtra shows a radial pattern from the central highland. The synrift sediments of Early Cretaceous constitute the principal source rocks in the basin. Almost all hydrocarbon accumulations in both Tertiaries and Cretaceous are sourced from Early Cretaceous sediments. It is inferred that the source rocks maturity of Cretaceous is poor and remains immature in onland. The effect of igneous intrusions in effect of igneous intrusions in onland wells (Not wells of onland) can be seen on the thermal maturity while the generation capacity of Jurassic source rocks is higher than the Cretaceous source rocks in onland. Prospectivity The Saurashtra basin has a total hydrocarbon inplace of 310 MMTOE, out of which 79 MMTOE has been discovered and this is now entirely sub-commercial inplace. The remaining, 231 MMTOE, nearly 75% of total inplace is potential to be explored and discovered. The basin has been assessed earlier during 1995- 96 study along with 14 other basins. During 2017 Hydrocarbon Resource Assessment Study, 3D PSM and Aerial Yield have been used. 2D seismic data are reported combined with Kutch Basin due to contiguity of datasets. The 2017 resource reassessment study has incorporated 27 drilled well information. Basin has sparse seismic data having less record length and a few number of wells drilled. Gravity, 2D seismic data and reports are good while magnetic, geochemical, 3D seismic, well data are fair. Reliability of results is good. 3D PSM and Trap Density method have been used to assess hydrocarbon resources due to adequate data coverage. Sub-basalt imaging, variable basalt thickness and inadequate onland seismic data are a few challenges. Cretaceous plays can be focus area. Low frequency 2D seismic API for Saurashtra onland, magneto-telluric (MT) and controlled source electromagnetic (CSEM) survey are recommended.