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FIDUK, JOSEPH C., Independent Geologist, 4215 Evans Drive, Boulder, Colorado 80303

Abstract: Comparing Two Models of Source Rock Potential in the Perdido Fold Belt Area, Northwestern Deep Gulf of Mexico

Five intervals (Oxfordian, Tithonian, Barremian, Turonian, and lower Eocene) were modeled for source potential within the Perdido fold belt, Alaminos Canyon OCS protraction area. One-dimensional (1-D), thermal maturation models were run at sixteen locations along two regional profiles. Steady state and rifting heat flow model results are compared to evaluate potential source rocks. Maturation timing was primarily affected by the depth of burial, and to a lesser extent, by structural uplift and the thickness of underlying autochthonous salt.

The rifting heat flow model predicts source maturity earlier than the steady state model at all locations for all potential source intervals. Direct comparison of arrival at peak oil generation (%Ro=0.9) for the steady state to rifting model yields these ranges, respectively: Oxfordian -- 3.9 - 29.2 vs. 28.2 - 50.5 Ma, Tithonian -- 2.6 - 14.2 vs. 6.4 - 35.8 Ma, Barremian -- 3.2 - 10.0 vs. 4.2 - 30.2 Ma, and Turonian -- l.4 - 4.2 vs. 2.7 - 22.4 Ma. Separating the 1-D model locations into upthrown and downthrown groups produced more narrow ranges (3-14 my differences) for both models. Calculating the difference in arrival at peak oil generation for each location, the rifting model produced peak oil generation earlier by 13.5-37.3 my in the Oxfordian, 11.7-22.0 my in the Tithonian, 11.5-24.9 my in the Barremian, and 10.3-18.0 my in the Turonian. The lower Eocene source did not reach peak oil generation in either model.

In the steady state model, only Oxfordian and Tithonian source rocks reached peak oil generation at one-half or more locations. They reached peak oil generation after fold belt formation (36-30 Ma). In the rifting model, the Oxfordian, Tithonian, Barremian, and Turonian strata have all reached peak oil generation at one-half or more locations. However, the Oxfordian reached peak oil generation prior to fold belt formation (37.1-50.5 Ma) when structural traps were not present. With the number of assumptions required and our level of uncertainty, the two models probably serve as realistic end-members with the true maturation picture lying somewhere in-between. 

AAPG Search and Discovery Article #90924©1999 GCAGS Annual Meeting Lafayette, Louisiana