Thermal history and extension of the lithosphere in the Mannar basin and realization its hydrocarbon potential, offshore Sri Lanka

Abstract

Data on the structure of the sedimentary blanket and the composition of its rocks, measurements of deep temperatures and vitrinite reflectance published in the open press were used for the numerical 1-D reconstructions of the thermal evolution of the Mannar Basin and the history of its tectonic subsidence near wells Pearl-1, Dorado North, Pseudo Mannar Deep and Barracuda. Analysis of variations in the basin's tectonic subsidence and published geophysical data on the modern depth of the MOHO boundary made it possible to numerically estimate the degree of stretching of the basin's lithosphere at different stages of its evolution. Our analysis shows that a significant part of the lithosphere extension occurred before the start of the formation of the basin's sedimentary cover. The moderate lithosphere extension with amplitude β = 1.15–1.25 accompanied the thermal activation of the basin lithosphere during the second stage of the basin rifting in the Late Cretaceous. Our modeling suggests a more moderate history of changes in the thermal regime of the basin's lithosphere and lower degree of maturity and realization of hydrocarbon potential in sedimentary sections of the Pearl-1, Dorado North, Pseudo Mannar Deep and Barracuda wells than those reconstructed numerically in recent studies of the Mannar Basin.