The Effects of Fractures on Reservoir Distribution, Reservoir Quality, and Hydrocarbon Migration

Horne, John C.¹, John R. Forster², Richard F. Inden³, William C. Pearson^4
1 Orion International Limited, Denver, CO
² The Wetterhorn Company, Centennial, CO
³ LSSI, Denver, CO
⁴ Pearson Technologies Inc, Lakewood, CO

Structurally and stratigraphically entrapped hydrocarbons, as well as the trends of reservoir facies and hydrocarbon migration pathways, are influenced strongly by fracturing associated with basement linears. At least three types of basement structural features influence production and migration of hydrocarbons and water: 1.) Basement structural highs, 2.) Short basement faults that commonly define the margins of basement structural highs, and 3.) Regional crosscutting linear features that define and create major structural and compositional discontinuities. Integration of aeromagnetic data with log and core facies, drill stem tests, hydrocarbon shows, and production information indicate that motion and the timing of the movement along regional basement linears is instrumental in controlling where entrapment of hydrocarbons takes place.

Sandstone reservoirs, coals, and other source beds vary in trend and thickness along paleotectonic features defined by basement linears. Fracturing associated with these basement linears enhances permeability and provides migration paths from source beds to reservoir facies. Movements along these linears formed paleotectonic features that controlled the distribution, trend, and thickness of reservoir facies in lowstand valley-fill, transgressive erosional remnants, and highstand shoreline deposits. These basement linears also influence the thickness and trends of coals and other source beds as well as the migration pathways of the generated hydrocarbons from the source intervals. These migration pathways define favorable hydrocarbon fairways. Exploration opportunities are enhanced where reservoir-potential facies pass through active hydrocarbon cells. Consequently, basement linears are important controls on the migration pathways of hydrocarbons as well as on structural development and the productive limits of many reservoir-potential facies.