Application of Basin Analysis to Diagenetic Modeling
Basin modeling techniques can be used to predict diagenetic reaction pathways in clastic rocks as well as organic maturation levels in adjacent source rocks. The diagenesis of potential clastic hydrocarbon reservoirs is controlled principally by the primary mineral assemblage, the pore fluid chemistry, and the temperature through time. Previous models of clastic diagenesis in hydrocarbon reservoirs have relied on petrographic observation; therefore, they are limited to descriptive interpretation. Recent work has shown that water-soluble organic compounds can influence the diagenetic reaction path ways by controlling pH and Eh of the pore fluids and by forming soluble complexes with inorganic species, thereby increasing solubilities of framework grains, cements, or both. O ganic geochemical data demonstrated that these water-soluble organic compounds are released from the organic-rich source rocks prior to the generation of liquid hydrocarbons. Because these organic reactions are time and temperature dependent, basin-specific thermal models can be used to integrate organic maturation of hydrocarbon source rocks and porosity modification in potential clastic reservoirs.
Time-temperature models using kerogen-specific kinetic parameters have been developed for two tectonic settings: rift and Laramide-style basins. These models allow us to predict the extent and timing of oil generation within the source rocks, and they provide temperature data through time allowing us to model reservoir diagenesis.
In rift basins, the organic and inorganic reactions are mainly dependent on heat flow and basin geometry through time. Reservoir porosity and liquid hydrocarbons are generated early in basin development because of the high heat flow. In Laramide-style basins, porosity modification and liquid hydrocarbon production depend on post-Laramide basin geometry and occur later in basin development. Heat flow values are lower and relatively constant through time, so deeper burial is required for the more advanced stages of organic and inorganic diagenesis.
These applications demonstrate that basin modeling techniques can be combined with geochemical data to predict both hydrocarbon maturation and porosity patterns in clastic reservoirs. The basin modeling techniques can be applied to both developed and frontier basins.
AAPG Search and Discovery Article #91043©1986 AAPG Annual Convention, Atlanta, Georgia, June 15-18, 1986.