Modelling petroleum generation of Late Cretaceous Dabut Formation in the Jiza-Qamar Basin, Eastern Yemen

Abstract

The Jiza-Qamar Basin in eastern Yemen is still undergoing hydrocarbon exploration and hydrocarbon potential has not been assigned yet. In this study, subsurface samples from two onshore and offshore wells were collected to characterize the source rocks of Dabut Formation and to incorporate into basin modelling in order to know and determine the timing of petroleum generation and expulsion of the Dabut source rocks. Based on organic geochemical analysis, the Dabut sediments have variable TOC content in the range of 0.5–2.5 wt%, indicating fair to good source rock generative potential. The organic matter of Dabut source rock is dominated by Type III kerogen with minor mixed III–II kerogen contributions, and is thus considered to be mainly gas-prone and some oil-prone. This is supported by HI values in the range of 50–212 mg HC/g TOC. Vitrinite reflectance in the range of 0.63–0.88%Ro and pyrolysis Tmax in the range of 427–454 °C, generally indicate that the Dabut source rocks contain mature organic matter.One-dimensional basin modelling was performed to analyse the hydrocarbon generation and expulsion history of the Dabut source rocks in the Jiza-Qamar Basin based on the reconstruction of the burial and thermal maturity histories in order to improve our understanding of the hydrocarbon generation potential. Calibration of the model with measured vitrinite reflectance (%Ro) and borehole temperature (BHT) data indicates that the paleo-heat-flow was constant during the Late Cretaceous–Paleogene but increased during the Late Paleogene–Neogene and then decreased exponentially from Neogene to present-day.The modelled maturity history predicts that the oil generation (0.5% Ro) in the Dabut source rock began from about 56 Ma to 42 Ma and the peak hydrocarbon generation (0.86% Ro) occurred approximately from 14 Ma to 13 Ma. These models also indicate that the main phase of oil generation was at 56 Ma to 25 Ma, whereas the main phase of gas generation began from about 25 Ma to 14 Ma and still generated in the present-day.