Sedimentary thermal maturation models for the deepwater eastern Gulf of Mexico



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Texas Tech University


In the eastern deepwater Gulf of Mexico, little drilling has taken place, relative to the highly studied Texas-Louisiana continental slopes. Thus, geologic data is relatively scarce and the petroleum system is not well understood. From 1999 through 2000, TDIBrooks international, Inc., collected a series of roughly 130 heat flow measurements in and around the De Soto Canyon, Lloyd Ridge, Lund, and Atwater Valley protractions in the eastern Gulf of Mexico. The data set revealed significant spatial variation of the heat flow values (5-87 mWW) throughout the survey region. Using this heat flow data set, well logs, and previously published information; sedimentary thermal history and hydrocarbon maturation models have been generated for the deepwater eastern Gulf of Mexico.

Six areas of similar heat flow values were identified within the region. Seismic stratigraphic studies and well logs were used to create a history of sediment accumulation and compaction since the Late Jurassic for each of the six areas. The effects of the cooling lithospheric basement, heat conduction up the thickening sedimentary column, dewatering due to compaction, and radiogenic heat generation were added to the model, using BasinMod 1-D, to complete a sedimentary thermal history. Comparison of the six models revealed that sedimentation from the Mississippi River and different crustal types were responsible for the spatial variation of heat flow across the study region.

The depth, timing, and degree of maturation in terms of vitrinite reflectance were then determined using the EASY%Ro method. It was found that the increased sedimentation from the Mississippi River did not effect thermal maturation, however increased radiogenic heat production in groups located atop thin transitional crust of granite-like composition significantly increased the thermal development of parts of the basin. Although to varying degrees, all groups in the study area experienced enough heating throughout the history of the Gulf to potentially form late mature oil and, in some areas, generate gas.