Variability in the Crustal Structure of Passive Margins: Implications for Hydrocarbon Exploration in South Asia
South Asia Exploration, BP Exploration Ltd., Sunbury-on-Thames, United Kingdom
Deep water passive margins are increasingly an area of focus for hydrocarbon exploration which has lead geoscientists into a deeper investigation of the formation mechanisms and basin characteristics of passive margins to inform exploration access decisions. In this paper we discuss the distinctive elements of volcanic and non-volcanic margin types considering the available constraints on crustal structure and also the present unknowns in passive margin geology and crustal geophysics. We discuss the commonly used assumptions which are made by the hydrocarbon industry when modelling the petroleum systems of a margin. An increase in the availability of high quality seismic reflection data brings significant new insights into the detailed variation in crustal structure and in a number of places is starting to indicate along strike changes in what were previously considered to be uniform passive margins. The importance of the pre-rift structural history relative to the mechanism of margin formation is evaluated as a factor in this variability. We draw on a number of examples from volcanic and non-volcanic margins in the North Atlantic where a combination of high quality seismic reflection and refraction data allow interpretation of the whole crustal structure. The structural elements which impact on hydrocarbon prospectivity are emphasised, in particular; (i) the distribution of stretched continental crust impacting the preservation of pre-rift stratigraphy and radiogenic contribution to heat-flow models and (ii) the impact of the inferred formation mechanism on the heat-flow history of the margin. In the final section of the paper we illustrate the types of deep water margins encountered in South Asia and draw on the presented analogues from the Atlantic margin to highlight the challenges and opportunities facing exploration geoscientists in this part of the world.
Presentation GEO India Expo XXI, Noida, New Delhi, India 2008©AAPG Search and Discovery