Region: Northern Midcontinent|
Upper Virgilian--Province Summary
This Upper Virgilian 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).
Upper Virgillian Stratigraphic Oil and Gas Play
by Mitchell E. Henry and Timothy C. Hester
This play extends throughout the province, except in the southwest part
of the Texas Panhandle and on the Wichita Mountains front where Upper
Virgilian strata are absent. Strata consists of all Middle and Upper
Virgilian Shawnee, Wabaunsee, and Admire Group rocks, including
correlative units in the Ada Group and in the lower part of the Ponotoc
Group. Drilling depths to the top of rocks in this play range from
about 2,000 ft in the east-central part to about 9,000 ft in the deep
southern part. The principal defining features of this play are that
both oil and gas are produced, primarily from limestone reservoirs.
Reservoir rocks are generally limestones of the Shawnee, Wabaunsee, and
Admire Groups. Most of these rocks are oolitic and skeletal
grainstones, originally formed in high- energy environments, in which
subsequent leaching resulted in secondary porosity development (Parham,
1993). Reported porosity values range from 8 to 17 percent, with a
median value of 13 percent. Because most porosity is secondary,
porosity in yet undiscovered reservoirs is expected to be good but
Source rocks and timing
Source rocks for this play are unknown, but the general lack of
thermally mature rocks in the immediate producing areas suggests that
longer distance migration of hydrocarbons may be involved (Rice and
others, 1989). Quality of possible source rocks for this play has been
discussed in other Pennsylvanian plays such as in the Morrow Sandstone
Gas and Oil Stratigraphic or Atokan Sandstone Stratigraphic Gas plays.
Strata in this play generally thicken southward from about 400 to about
3,500 ft. The presence of major accumulations indicates that the timing
of hydrocarbon generation and migration, and trap formation is favorable
for the charging of reservoirs in this play.
The most common trap type in this play is stratigraphic, although
structural and combination types do exist. Stratigraphic traps are
probably formed by overlying shales. Hydrodynamic trapping is an
important mechanism at the Greenwood gas area (Pippin, 1985). Known
accumulations occur at depths of about 3,000 to 6,100 ft with a median
depth of about 4,000 ft.
This play is extensively explored. Almost 16,000 wells have been
reported to reach rocks of this play. The large number of wells
targeting Chesterian through Lower Virgilian rocks could bring that
total to about 79,000. Seventeen major accumulations are assigned to
this play; 13 gas and 4 oil. The largest gas accumulation is at
Greenwood gas area, with an estimated ultimate recovery of 1.8 TCFG.
The largest oil accumulation is at Quinduno north field, with an
estimated ultimate recovery of 13 MMBO.
The potential for future major hydrocarbon discoveries in this play is
projected to be insignificant, primarily because of the relatively few
major accumulations contained in a very intensely explored area.
Because of the evidence of long distance migration of thermally
generated gas, the lack of thermally mature source rocks is not a
serious liability for this play. Historical discovery and well
completion data were the major sources of information used for
assessment of this play.
Pippin, Lloyd, 1970, Panhandle-Hugoton field, Texas-Oklahoma-Kansas--the first fifty years, in Halbouty, M.T., ed., Geology of giant petroleum fields: American Association of Petroleum Geologists Memoir 14, p. 204-222.
Rice, D.D., Threlkeld, C.N., and Vuletich, A.K., 1989, Characterization and origin of natural gasses of the Anadarko basin, in Johnson, K.S., ed., Anadarko Basin Symposium, 1988: Oklahoma Geological Survey Circular 90, p. 47-52.
Kansas Geological Survey, Digital Petroleum Atlas
Updated May 28, 1998
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