Reaction kinetic, maturity, burial and thermal histories modelling of cambay shale source rocks, Cambay Basin, Western India

Abstract

The Cambay Shale Formation (CSF), the known source rock for conventional oil and gas, now becomes a key target for shale oil/gas exploration in the Cambay Basin. In the present study, maturity, wellbore temperature and kerogen kinetics data from the several locations in the Cambay Basin have been integrated into PetroMod®, a basin and petroleum system modelling (BPSM) software, to generate maturity profile, burial and thermal history in the Cambay Basin. The Optkin program optimised kerogen kinetic results indicated that the activation energy for the type III kerogens, which are prominently available in the basin, varies widely (44–72 kcal/mol). A sample from Mehsana-Ahmedabad Block shows a narrow activation energy range (40–50 kcal/mol), a characteristics of type II kerogen and the maximum (91%) of the initial petroleum potential is contributed by a single activation energy (46 kcal/mol). BPSM models indicate that the major portion of the CSF in the north of the basin is mainly under early and main oil generation window, where shale oil prospect can be explored. Compared to the north part of the basin where late oil and wet gas generation windows enter into the Olpad Formation at ~2700 m and ~3100 m respectively, the source rocks, i.e. CSF at the centre of the Broach block in the South Cambay Basin indicate the presence of late oil and wet gas generation windows at ~3100 m and ~3900 m, respectively. The models generated in the study area suggest that the deeper section of the South Cambay Basin may have prospective for shale oil/gas.