Evaluation of Hydrocarbon Prospects Using Surface Geochemical Data With Constraints From Geological and Geophysical Observations: Saurashtra Basin, India

Abstract

The Saurashtra Basin in western India is considered to have significant hydrocarbon potential. However conventional exploration methods, particularly for Mesozoic prospects, have been hampered by the thick basalt cover. In this study, near-surface geochemical methods are used to investigate the generation of thermogenic gaseous hydrocarbons in the basin. Shallow soil samples were collected from favourable locations identified by integrated geophysical and geochemical studies. The compositional and isotopic signatures of adsorbed gaseous hydrocarbons (methane through pentane) together with soil iodine concentrations were used as surface indicators of petroleum micro-seepages. High concentrations of adsorbed thermogenic methane (C 1 = 518 ppb) and ethane plus higher hydrocarbons (ΣC 2+ =977 ppb) along with iodine concentrations up to 68.5 ppm were observed. Total organic and inorganic carbon (TOC and TIC) measurements, fluorescence and X-ray diffraction (XRD) studies showed that the nearsurface hydrocarbon occurrences were seepage related. Elevated hydrocarbon and iodine concentrations were coincident with dykes and lineaments in the study area, which probably served as conduits for the micro-seepage of hydrocarbons.

Geochemical assessment of light gaseous hydrocarbons in near-surface soils of Kutch–Saurashtra: Implication for hydrocarbon prospects

“…High concentrations of hydrocarbons were found to be characteristic of areas near Anjar of Kutch and the area south of Rajkot of Saurashtra as shown in the concentration distribution maps of methane and C 2+ hydrocarbons (figure 7a, b) signifying the area's potential for hydrocarbons. Geological and magnetotelluric surveys in the Saurashtra peninsula have shown the presence of thick Mesozoic sedimentary sequences in the western part (Harinarayana 2008;Rao and Reddy 2005), and led to the drilling of the Lodhika-1 well near Rajkot (Mani et al 2012) which confirmed the presence of a Mesozoic section beneath the Deccan Traps which could have acted as source rock for the generation of hydrocarbons.…”

Carbon reservoir perturbations induced by Deccan volcanism: Stable isotope and biomolecular perspectives from shallow marine environment in Eastern India

“…Similar signatures can be found in OM derived from high-temperature alterations and external mixing from petroliferous sources. Extensive wildfires during volcanism and micro-seepage of petroleum from underlying basalts have previously been noted from within and around the volcanic province (Pal et al, 2015;Mani et al, 2012). Contribution from thermally altered biomass and hydrocarbon contamination therefore may have been prevalent during deposition of the initial phases of the inter-trappean.…”