Three-dimensional structural model of the Painter and East Painter reservoir structures,Wyoming fold and thrust belt

摘要

The Painter and East Painter reservoir structures are located in the hanging wall of the Absaroka thrust in the Wyoming fold-thrust belt.Balanced cross sections and interpreted logs and dipmeter data from more than 50 wells have been integrated to develop a three-dimensional (3-D) structural model of the Painter reservoir structures.The structures are interpreted as a pair of asymmetric faulted detachment folds formed along the hanging-wall ramp in Triassic-Jurassic units in the Absaroka thrust sheet.The Painter reservoir structure verges to the southeast and has a gentle backlimb and a steeply dipping to overturned forelimb,whereas the East Painter structure displays steep dips on both limbs.The front limbs of both structures contain forelimb thrust faults with small displacements.A tight syncline separates the structures and contains several out-of-syncline thrusts in the Jurassic Twin Creek limestones.Cross sections through the structures are restored using line-length balancing for the Nugget formation and area balancing of the Ankareh-Thaynes-Woodside formations and the Twin Creek Formation.The structures are interpreted to have initiated as a pair of detachment folds cored by moderately ductile limestones and shales of Triassic age.Increasing shortening resulted in tightening of the structures,the development of out-of-syncline thrusts,and the propagation of thrust faults on the steep forelimbs.The tight geometry of the East Painter structure resulted from frictional resistance to fault slip along the hanging-wall ramp in the Triassic-Jurassic units.The balanced 3-D structural model ensures consistency of the geometry of all interpreted horizons and faults and can be used to construct improved structural maps of reservoir units in the Painter reservoir structures.