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Play Start Page Play Summary Resources Kansas Info Region: Northern Midcontinent
System: Pennsylvanian

Morrow Play--Summary

This Morrow Play information is from the U. S. Geological Survey 1995 National Assessment of United States Oil and Gas Resources (available on CD-ROM from the U.S.G.S. as Digital Data Series DDS-30, Release 2).

Morrow Sandstone Gas and Oil Stratigraphic Play

by Mitchell E. Henry and Timothy C. Hester

This play includes all Pennsylvanian Morrow Group sandstones and shales and is oriented in a broad band that occupies most of the province, except the part along the northeastern and southwestern edges of the province where Morrowan age strata are absent, and that part included in the Deep Stratigraphic Gas Play. Depths range from about 4,000 ft on the northern shelf to 13,000 ft at the southern play boundary (upper depth limit of the Deep Stratigraphic Gas Play). Similar to the Springer Stratigraphic Gas and Oil Play but much more extensive, this play is gas prone and accumulations are almost always trapped stratigraphically in sandstone reservoirs.


Reservoirs are all sandstones of the Morrow Group, and include the Keyes, Puryear, Purdy, and Primrose sands. The Morrow Group ranges in thickness from erosional truncation along the northeastern and southwestern province boundaries to about 1,500 ft at the southern play boundary (adjacent to the Deep Stratigraphic Gas Play). The predominate lithology of Morrowan strata is shale but significant thicknesses of sand exist, generally increasing from northwest to southeast.

Morrow Group sands are generally fine grained and often well cemented (Pate, 1959). Reported porosities range from about 6 to 26 percent, with an approximate median value of 13 percent; permeability ranges from 1 to 600 mD with an approximate median value of 20 mD. Reservoir quality is expected to be good in much of the play area.

Source rocks

Because most reservoirs of this play are stratigraphically enclosed by shale and mudstone, the most probable hydrocarbon source is Morrow Group shales. Burruss and Hatch (1989) measured TOC values of selected Pennsylvanian shales (including Morrow Group shales) as high as 18 percent and concluded that these rocks have good genetic potential. However, Burruss and Hatch (1992) present evidence against a Morrowan source for Morrowan reservoirs in western Kansas and southeastern Colorado. Although Burruss and Hatch (1989) determined that Morrowan organic matter is both oil and gas prone (kerogen types II and III), gas is by far the most abundant resource produced from the Morrow Group. Modeling by Schmoker (1989) and others suggests that Morrowan age rocks in Oklahoma and Texas, and therefore most major hydrocarbon accumulations in the Morrow Group, are at or above the thermal maturity level required for the onset of oil generation (about Ro = 0.6 percent). In Kansas, Morrowan rocks are less mature.


Timing of petroleum formation and migration, and trap formation in this play is favorable as evidenced by the fact that more than 330 major accumulations have been discovered. Modeling by Schmoker (1989) indicates that Morrowan rocks entered the thermal zone of oil generation as early as 260 Ma in the southern part of the play, at about 50 Ma in the central part of the play, and may not yet have entered the thermal zone of oil generation in the northern part of the play. Hydrocarbon migration has probably occurred over very short distances in most areas of the play.


Traps types for reservoirs in the Morrow Group are almost exclusively stratigraphic. Reservoir origins are interpreted as valley fill, beach and offshore bar, and deltaic deposits (Rascoe and Adler, 1983). Seals are generally formed by enclosing Morrowan shales and mudstones. Major accumulations are distributed throughout western Oklahoma, Texas Panhandle, and southwestern Kansas, with a few in southeastern Colorado.

Exploration status

More than 26,000 wells penetrate Morrowan rocks in this play. Of these, more than 10,000 are hydrocarbon producers. Hydrocarbon production is more or less centered in the play, with the southeastern and northwestern ends being less productive. The northwestern part of the play is least productive and least well explored. Of the 333 major accumulations assigned to this play, 257 are gas and 76 are oil. The largest gas accumulation is at Watonga-Chickasha Trend, with an estimated ultimate recovery of 4.3 TCFG. The largest oil accumulation is at Postle field, with an estimated ultimate recovery of 120 MMBO.

Resource potential

This play is well explored in Oklahoma and Texas but less so in Kansas and Colorado. Future major hydrocarbon discoveries are expected, however, in spite of the present exploration density. Most new discoveries are expected to exist primarily in stratigraphic traps (R.A. Northcutt, oral commun., 1993). Some factors limiting the potential for new discoveries include the already high drilling density in many areas, and the fact that in some apparently unproductive areas, Morrowan rocks are composed of more shale and less sand (Rascoe and Adler, 1983). The potential for future discoveries in this play is expected to be moderately good. Trends in historical discoveries and completion data were used to estimate undiscovered resources.

Play Map

map showing fields in this play


Burruss, R.C., and Hatch, J.R., 1989, Geochemistry of oils and hydrocarbon source rocks, greater Anadarko basin--evidence for multiple sources of oils and long-distance oil migration, in Johnson, K.S., ed., Anadarko Basin Symposium, 1988: Oklahoma Geological Survey Circular 90, p. 53-64.

Burruss, R.C., and Hatch, J.R., 1992, Geochemistry of Pennsylvanian crude oils and source rocks in the greater Anadarko basin--Oklahoma, Texas, Kansas, Colorado, and Nebraska: An update [abs.], in Johnson, K.S., and Cardott, B.J., eds., Source rocks in the southern Midcontinent, 1990 Symposium: Oklahoma Geological Survey Circular 93, p. 197.

Pate, J.D., 1959, Stratigraphic traps along north shelf of Anadarko basin, Oklahoma: American Association of Petroleum Geologists Bulletin, v. 43, p.39-59.

Rascoe, Bailey, Jr., and Adler, F.J., 1983, Permo-Carboniferous hydrocarbon accumulations, Mid-Continent, U.S.A.: American Association of Petroleum Geologists Bulletin, v.67, no. 6, p. 979-1001.

Schmoker, J.W., 1989, Thermal maturity of the Anadarko basin, in Johnson, K.S., ed., Anadarko Basin Symposium, 1988: Oklahoma Geological Survey Circular 90, p. 25-31.

Kansas Geological Survey, Digital Petroleum Atlas
Updated July 11, 1996
Comments to webadmin@kgs.ku.edu