Abstract

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.

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