ABSTRACT: Reservoir Characterization of the Deep Upper Morrow Puryear Sequence in the Anadarko Basin, Western Oklahoma and Texas Panhandle

NICK, KEVIN E., PETER N. GALE, BRUCE CARPENTER, and LANNY KING, Target Reservoir Analysis, Oklahoma City, OK, CHARLES T. SIEMERS, P.T. Geoservices, Jakarta, Indonesia, CRAIG PECK, The GHK Company, Oklahoma City, OK, and R. DOUGLAS ELMORE, University of Oklahoma, Norman, OK

The deep Upper Morrow of the Anadarko basin (Western Oklahoma and Eastern Texas Panhandle) is one of the most prolific gas-producing units in the United States. Data from 15 cores and many logs were used to determine the controls on reservoir quality in the Puryear Sequence. The reservoir rocks are chert pebble conglomerates in the central part of the basin and pebbly arkoses in the northwest and southeast. Chert pebbles were apparently derived from uplifted Paleozoic rocks to the south and southeast. The coarse clastics are stacked, highly discontinuous linear sand bodies that rest unconformably on marine shales, terminate abruptly downdip, and are laterally bounded by mudstones. Depositional environments for individual channels are dominantly nonmarine and are interpreted to be rapi ly prograding fan deltas with relatively minor delta front deposits and/or valley-fill deposits. Marine shales associated with the conglomerates and sandstones have a characteristic "pedestal"

profile in logs, which can be a proximity indicator for channels. Shale conductivity maps also indicate proximity to terrigenous sources. A general paragenetic sequence that incorporates lithologic and geographic variation is early clay, carbonate, and silica cements; selective dissolution of chert and/or feldspar; emplacement of hydrocarbons; and late quartz, clay, ankerite, dolomite, and pyrite cements. The dominant porosity is secondary after the dissolution of chert and feldspar. Porosity in conglomerates shows no direct relation to permeability in the conglomerates. Dissolution is controlled by the amount of detrital clay and the cleanest, thickest units are most likely to develop significant secondary porosity.

AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)