Last modified: 2011-08-16
Abstract
Palynological, organic geochemical and thermal maturation analyses have been carried out on 232 core and 256 ditch cutting samples collected from exploratory and productive wells drilled in the Madbi-Shabwa Basin, Central Yemen, to evaluate the hydrocarbon potential of the Madbi Formation sediments.
The Madbi Formation contains fair to good (0.5 min., 6.7 max., and 1.4 avg.) total organic carbon content (TOC %), which indicates a fair to good potential source rock with an average fair petroleum potential (PP) of 6.7 mg HC/g dry rock. Mapping of the organic carbon richness and petroleum potential of the Madbi Formation sediments shows higher TOC and PP values centralized in the basin centre, which gradually decrease in a NE-SW direction. Most of the Madbi analysed samples are mainly oil-prone material of kerogen type II, as indicated from the hydrogen index (HI) value of ~ 255 mg HC/g TOC and from the palynofacies analysis. Thermal maturation analyses (Tmax 420-460 °C,Rv 7 (~ 0.9) 1.3 %, TAI 2+ to 3+) indicate mature-oil generation window for the Madbi Formation source rock. Quality of the crude oil extracted from the studied productive wells is excellent, because it is free from S, Ni and Va and shows API gravity value of ~ 44°.
The present investigation confirmed the Madbi Formation as a good productive oil source rock at the centre of the Madbi-Shabwa Basin, and suggests further studying the formation at the southern part of the basin and in other adjacent basins.