The tectonic evolution of western India and its impact on hydrocarbon occurrences: an overview

Abstract

The largest hydrocarbon accumulations of India were localized in western India by a unique convergence of tectonic events. Mesozoic rifting along the structural trends of Proterozoic mobile belts formed the passive margin basins of the Indian coast. During the Campanian rifting of Madagascar from India, north-south-striking normal faults propagated into the area of the Cambay Graben. Late Maastrichtian doming over the incipient Deccan/Réunion hotspot imparted extensional stresses to the northwestern Indian coast and formed the fault block that became the Bombay High. After eruption of the Deccan flood basalts in Early Paleocene, extension continued in the weakened crust. This resulted in enhanced subsidence of the Cambay Graben and Surat (Danahu) Depression, rifting of the Seychelles microcontinent from India, and reactivation of normal faults on the emergent Bombay High. The Cambay Graben and the Surat (Danahu) Depression filled with organic-rich source shales as they underwent thermal subsidence. Shallow-water Eocene to Miocene carbonates developed on the slowly subsiding Bombay Platform, and sea-level oscillations fostered secondary porosity development. Late Tertiary maturation of the Surat (Danahu) Depression shales generated hydrocarbons that migrated into the carbonate reservoirs on the Bombay High. Konkan-Kerala, and the older basins of the east coast of India, were unaffected by the post-Campanian tectonic events, and lack the favorable play elements that characterize the giant fields.