The Lanyard Field, a Structural-Stratigraphic Trap, Denver Basin, Colorado

Abstract

Cretaceous sandstones are oil and gas productive throughout a large area in the Denver bas111. The Lanyard field is a structural-stratigraphic trap which has produced in excess of 2,388,000 bbls of oil and 4.1 Bcf of gas from the D Sandstone. Productive sandstones are interpreted to be channel deposits on the basis of subsurface mapping and core examination. Seven Cretaceous stratigraphic intervals from the Lanyard field area were identified from well data. Thickness variations on these isopach maps are caused by unconformities, convergence. and normal faulting. Thickness variations caused by unconformities and convergence may be related to paleostructure: variations caused by normal faulting are post depositional and related to Laramide (present) structure. Analyses of the seven stratigraphic intervals clearly show that paleostructure influenced D depositional patterns. D channel sandstones accumulated 111 a northeast-trending paleostructural low. Present-day structure 1s a southwest-plunging nose. The trend and location of the nose coincides with the trend and location of the D channel system. Thus. the paleostructural low has undergone structural inversion and is now a structural high. Knowledge of paleostructural control on reservoir facies provides a new idea for petroleum exploration in the D Sandstone of the Denver basin.