The value of fieldwork in making connections between onshore outcrops and offshore models: an example from India

Abstract

AbstractFieldwork provides an efficient and economical way of obtaining genuine geological data that can be used to constrain, test and develop exploration models in frontier areas. This study of the Cretaceous outcrops of NW India has been used to characterize models for petroleum systems postulated to have developed beneath the Deccan volcanic sequence, offshore western India, where well data are not available. To date, exploration of ‘sub-Deccan plays’ has mainly been limited to the NW, where the presence of a working Cretaceous petroleum system has been proven in the offshore Kutch Basin.A revised chronostratigraphic framework has been defined for the Cretaceous section as a result of new biostratigraphic data collected during this study and a thorough revision of existing palaeontological data. The revised framework, together with lithofacies observations from the field, has provided a basis for regional sequence stratigraphic correlation, which has been used to link data from onshore outcrops to models of offshore petroleum systems.A Lower Cretaceous clastic package that, in part, corresponds to the Lower Goru and Bhuj Formation reservoirs of the Indus Basin of Pakistan and the Kutch Basin in India has been correlated across the region. Towards the top of this package, a transition from fluvial to shallow-marine sedimentation marks the onset of a marine transgression that reaches its peak in the Turonian. Marly limestones and claystones associated with this regionally mapped event are a potential topseal to the Lower Cretaceous clastic package. Geochemical evaluation of several outcrop locations has identified potential source-prone facies that, if present downdip in the offshore, may provide a mechanism for charging a pre-Deccan play.