SOURCE AND MATURATION OF HYDROCARBONS IN THE FRIO FORMATION OF THE HUMBLE FIELD, SOUTHEAST-TEXAS GULF COAST BASIN
The source and maturity of hydrocarbons in the Frio Formation of the Humble oil field, Harris County, Texas, from the East Texas Gulf Coast basin, were interpreted by combining the geochemical characteristics of the Humble oils and thermal evolution history of the Humble field. Ten oil samples from the Frio Formation collected from depths of 720-1569 m were analyzed using high-resolution whole-oil gas chromatography (GC), high-performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS). Temperature and stratigraphic data were used in the 1-D PetroMod2012 model to predict the potential source rock and reconstruct the geologic history of the Humble field. Based on Geochemical Inversion analysis, the Humble oils likely belong to the same genetic family and are sourced from a clay-rich, suboxic/oxic, marine-terrigenous transitional depositional environment. The oils were likely generated from mature source rocks which had already entered the main oils generation window with vitrinite reflectance ranging from 0.68% to 1.3% and expulsion temperatures of 126°C to 137°C. Combining the maturity biomarker properties with thermal maturity modeling, the Lower Wilcox could be a possible source of the Frio reservoired oils with generation and expulsion window of 29-11 Ma. The Lower Wilcox in the Humble field was formed in a deltaic depositional environment belonging to the Rockdale delta system, which is consistent with the transitional depositional source facies concluded from the geochemical inversion and further supporting the modeling result. However this does not rule out the possibility that the hydrocarbons of the Humble field were generated from the Midway, Eagle Ford, and Woodbine formations, which also deposited in nonmarine-marine transitional environment and are consistent with predicted geologic ages. Comparison of the Humble oils with the South Liberty oils (Banga et al., 2011) and Brazoria oils (Guo, 2004) show they belong to one single genetic family with minor dissimilarities likely caused by facies variations resulting in different terrestrial input. The South Liberty oils likely received more higher-plant organic matter, whereas the Brazoria oils contain more marine input and the Humble oils lie in-between.
Source rocks, Maturity, Hydrocarbons, Humble, Geochemical inversion, Basin models
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