Petroleum Geology of the Cross Cut and Moran Sandstones (Lower Missourian), Callahan and Eastland Counties, Texas

HAMILTON, JASON F., OKT Petroleum Company, Inc., Edmond, OK, ARTHUR W. CLEAVES II, Oklahoma State University, Stillwater, OK, and JEFFERY A. JONES, Jones Company, Albany, TX

The Cross Cut and Moran sandstones were deposited from east-southeast to west-northwest in a high constructive, elongate cratonic deltaic environment. The sandstones are very fine- to fine-grained sublitharenites. Much secondary porosity is developed where abundant sand-size clay grains, and to a minor extent feldspar grains, have been partially or totally dissolved through diagenesis. Numerous tiny patches of ankerite cement are scattered throughout the sandstone section in the cores. Pore-filling vermiform kaolinite is the only authigenic clay present in significant amounts. These sandstones, because of their well-developed open pore systems with relatively little detrital matrix, authigenic clay or epitaxial cement, provide excellent petroleum reservoirs.

Sandstone geometry, log signature, outcrop and core sedimentology,

and thin section petrology indicate three facies: (1) incised channel, (2) distributary mouth bar, and (3) delta front. Strand zone development inferred from hingelines detected on structure, sandstone isolith, and total interval isochore maps provide further evidence for the delineation of the various facies and their relationships to one another. Production is obtained from all three facies. The Cross Cut and Moran fields in the study area are trapped by (1) stratigraphic termination of delta-front sandstone lentils encased in shale, (2) updip pinch out of incised channel complex sandstone or incised channel sandstone against regional dip, or (3) compactional drape and/or updip pinch out of distributary channel sandstone related to underlying structure.

AAPG Search and Discovery Article #91011©1991 AAPG Southwest Section Meeting, Abilene, Texas, February 9-12, 1991 (2009)