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Where the Action Is in Texas
(Excerpted with author and AAPG permission from article
developed by Eric Potter, UT Austin Bureau of Economic
Geology that will appear in the April issue of AAPG
Explorer)
Barnett shale, Fort Worth Basin
Hot spots continue to be Johnson
County and Tarrant County. Almost all wells are horizontals.
In many areas, state-of-the-art, highly automated
custom-designed rigs are drilling multiple horizontals from
a single surface pad. Frac operations in several areas have
been centralized to cut costs and reduce surface impacts.
Recent development plans indicate that locally, recoveries
of 50% of gas-in-place may be possible, utilizing aggressive
downspacing, in some cases to less than 400 feet between
horizontals.
Tight Gas plays, East Texas Basin
On the Sabine Uplift (east side
of the basin), aggressive development of the Cotton Valley
Sand and Travis Peak tight gas plays is continuing, mostly
with vertical wells. There is though some experimentation
with horizontals and vertical wells downspaced to 10 acres.
On the western side of the basin, the Cotton Valley Lime,
Travis Peak, Bossier and Deep Bossier plays dominate. The
Deep Bossier activity targets prograding wedge and lowstand
slope and basin floor sands at depths of 16,000 to 20,000
feet, typically thicker and much higher pressured than their
shelfal counterparts.
South Texas Tertiary and Cretaceous
Over 2000 well completions were
reported over the past two years in |
South Texas trends. The coast-parallel Tertiary-age Frio,
Vicksburg,
and Wilcox expansion-fault trends
and the Cretaceous Olmos tight sands fields in Webb County
all had significant drilling activity. Although most wells
were vertical, horizontals were drilled in all
plays—particularly in the Olmos. Except for the Frio,
reservoirs are tight sands that require hydraulic
fracturing.
Marathon Thrust Belt play, West Texas
SandRidge Energy, Inc. has
drilled more than 200 wells in the past four years along the
leading edge of the Marathon Thrustbelt south of Fort
Stockton. Production, which is from vertical wells in thrust
sheet targets (Wolfcamp and Tesnus sands, and fractured
Caballos Chert), has increased to 200 Mmcfd. SandRidge built
momentum by experimenting with drilling and completion
techniques, using their own equipment and crews, on lands
owned outright by the company, along with leased properties.
Bone Spring Formation, West Texas
Historically, Bone Spring
Formation development has focused on carbonate debris flows
along the margin of the northern Delaware Basin. Now, new
opportunities in siliciclastic slope and basin-floor fans
are being actively explored along the eastern margin of the
Delaware Basin in Texas. Activity is concentrated in Loving,
Pecos, Reeves, Ward, and Winkler Counties. Key technologies
include horizontal drilling and acid fracturing with
proppant.
Brookeland Field, East Texas, Austin Chalk
Horizontal-well development of
the Austin Chalk reservoir in Brookeland Field continues.
The Brookeland trend extends through parts of Tyler, Sabine
and Newton |
Counties, eastward into
Louisiana. In Texas, Tyler County saw most of the 2007
drilling, with over 20 new wells. Peak rates were in the
range of 2000 Bopd and 18 Mmcfd. Typical decline rates are
around 80% in the first year.
Wolfberry Play in the Midland Basin
Reservoirs in the “Wolfberry” low
permeability oil play are slope and basin systems, including
debris flows, grain flows, and turbidites composed of
carbonate detritus (Wolfcamp) or terrigenous sand and silt (Spraberry/Dean).
Natural fractures are probably also a factor. The target
zone is up to 3,000 ft thick. Here multi-stage fracs, as
many as 12, are making the difference in areas where earlier
vintage vertical wells were unsuccessful. In some cases, the
lower zones may be produced for several months before adding
upper zones.
Cleveland Sand horizontal play, Lipscomb Co (Northeast TX.
Panhandle)
Led by Jones Energy, over 350
horizontals have been drilled with ultimate recoveries
estimated at 1.5 Bcf per well, following completion
utilizing multistage open-hole frac jobs. The areas being
redeveloped were originally developed with vertical wells.
Edwards Reef Trend, Live Oak County (South Texas)
Pioneer Energy is leading this
resource-type play, based on its success in the Pawnee
Field. Pioneer estimated 300 Bcf of ultimate expected
production at Pawnee, and reported eight new discoveries on
the trend. 3-D seismic is an essential technology. Dozens of
NNW-directed horizontal wells have been permitted. |
Texas
& SE New Mexico
Region