Geovalidation of a Basin’s Thermal-Tectonic Model: Example from Faras Field, North Western Desert, Egypt
Abouelresh, Mohamed O.*2; Pigott, John M.1
(1) Conoco-Phillips School of Geology and Geophysics, University of Oklahoma, Norman, OK. (2) Faculty of Petroleum and Mining Engineering, Suez Canal University, Suez, Egypt.
In order to constrain the basin model (“Thermal-Tectonic Geovalidation”), four distinct thermal crustal conditions are perturbed and compared to the geochemical maturity data available from the boreholes. Since most of thermal indicators are cumulative, irreversible, and being a function of temperature and time, therefore, in order to specify and geovalidate the specific pathway that a basin evolved and its hydrocarbons matured, one must be able to specify at least one of these two parameters (temperature and time) at a particular geological event.
Faras field is located to the west of Abu Gharadig Basin. For the North Western Desert of Egypt, such geovalidation modeling procedures are critical to its proper hydrocarbon exploration and understanding as a complex basin product of tectonics and sedimentary response. The fault mechanical stratigraphy corresponds to observed extensional periods in the tectonic subsidence analysis. With the tectonic events then specified in time and thermal magnitude, experimental kinetic modeling outputs were generated and compared to present day geochemical maturity observations with a systematic variation of geological and geophysical parameters. The modeled findings show that increases in heat flow decrease model maturity gradients though increasing maturity, increases in surface temperatures shift maturity gradients linearly to higher values, increases in sediment conductivities lower maturities with depth, and the addition of “ghost” layers prior to erosional removal increase maturities beneath, and vice versa. The burial history with maturity windows curves indicate that the timing and level of maturation in steady state heat flow differs from that in rifting heat flow owing to the changes of the heat flow during and after the rifting event. Three source rocks are identified; Khatatba, Alam El Bueib and Kharita formations. The thermal-tectonic modeling results which are best fit the observed seismic reflection and borehole data suggest a multiple rifting model with a present surface temperature of 20 oC and heat flow of 1.5 HFU and with the sedimentation rate-estimated missing thicknesses for the Faras field. Therefore, the Khatatba, Masajid, and lowest part of the Alam El Bueib source rocks entered the mid mature (0.7 Ro) oil window approximately 95Ma and entered the gas stage approximately 25 Ma. The upper Alam El Bueib source rocks are today within the oil window.
AAPG Search and Discovery Article #90141©2012, GEO-2012, 10th Middle East Geosciences Conference and Exhibition, 4-7 March 2012, Manama, Bahrain