Basin Analysis of the Southern Yemeni Red Sea: Significance of Halokinesis Upon Subsalt Source Rock Maturities and Hydrocarbon Migration Dynamics

John D. Pigott¹*, Omer Aksu²**, and Ahmed Alahdal^1
1University of Oklahoma, USA
²TPAO, Turkey
*[email protected]
**[email protected]

An integrated seismic stratigraphy and 2-D basin-analysis investigation of the relatively unexplored southern Yemen Red Sea suggests significant hydrocarbon potential exists. In particular, the study revealed the significance of halokinesis upon dynamic trap structuring, fault-migration pathways, and the concomitant cooling effects of salt thermal refraction upon sub-salt source rock maturities. The integration of supra-salt borehole lithologic and geochemical data with reprocessed 2-D seismic reflection and refraction data provided a constrained 2-D basin analysis of sub-salt to supra-salt stratigraphy. Such observations revealed that this region is the product of four principle tectonic phases of rifting and crustal stretching ß’s: (1) Pre-18 Ma, ß = 1.22; (2) 18–14 Ma, ß = 1.195; (3) 11–5 Ma, ß = 1.21; and (4) post-5 Ma, ß = 1.24. The second episode mobilized the salt and created primary fault and structural migration pathways. Cumulatively, these stretching episodes and concomitant heat pulses modeled both as steady-state and rifting-model end-members suggest that source rocks of the supra-salt South Gharib B and those of the sub-salt clastics are under all conditions mature enough to generate hydrocarbons. Important to reservoir GOR fill and migration pathways, the modeling demonstrates that maturities and timing of expulsion and migration vary between the two models, and thus the chronology of the fault mechanical stratigraphy is critical. By applying a lithologic replacement approach, the temporal and spatial effects of the sub-salt strata can be shown to have cooled significantly owing to heat refraction and thermal conductivity of overlying salts. As permeability of the faults is unknown, two spectral end-members of fault-pathway potential were modeled to bracket the uncertainties. Resulting migration vector-volume fill maps for the four scenarios (steady state, rifting, permeable faults, impermeable faults) differ markedly in structural fill and GOR of potential hydrocarbons.

AAPG Search and Discovery Article #90077©2008 GEO 2008 Middle East Conference and Exhibition, Manama, Bahrain