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There’s no place quite like Texas.
Recent rig counts have shown 840 to 870 drilling rigs operating weekly in the state –80 percent of them with natural gas primary objectives.
Operators can enjoy drilling in areas with proven production, promising prospects, beautiful wide-open spaces and friendly people.
Although truth to tell, $9.50-per-Mcf natural gas and $100-a-barrel oil would have gotten the industry’s attention even if Texans were downright surly.
While the vast bulk of oil and gas produced in the state isn’t coming from recent exploration wells, new concepts are being tested in old plays all the time.
Current watchwords seem to be “horizontal” and “gas,” except in the Permian Basin, where scattered development drilling for oil occurs across the basin.
With that in mind – and mindful of the fact that the eyes of AAPG will be looking toward Texas this month for the Annual Convention and Exhibition in San Antonio – here’s a roundup of reports from the field.
Tight Gas Plays, East Texas Basin
East Texas is ground zero for the state’s tight-gas sand plays, where companies active in the East Texas Basin provide a good sampling of nationwide unconventional gas players.
Independents dominate drilling, but there’s been a re-appearance by majors via acquisition. For example, ConocoPhillips purchased Burlington and its interest in the play.
On the Sabine Uplift on the east side of the basin, aggressive development of the Cotton Valley sands and Travis Peak play continues. Vertical wells abound, but operators are experimenting with horizontals, as well as with downspacing vertical wells to 20-acre spacing.
On the basin’s western side, the Travis Peak, Cotton Valley lime, Bossier and Deep Bossier plays remain very active.
The Deep Bossier activity targets prograding wedge and lowstand slope and basin floor sands at depths of 16,000-20,000 feet, typically thicker and much higher pressured than their shelfal counterparts.
Recent rig activity reports showed 74 rigs active in the western part of the basin, and an additional 73 on the Sabine Uplift.
Collectively, over 3,200 wells have been completed in the past two years in these East Texas tight-formation plays, with the 2,440 being Cotton Valley sand wells on the Sabine Uplift.
James Lime Play, East Texas
The on-again, off-again, Lower Cretaceous James Lime play is on again.
Operators have looked at this extensional-basin, carbonate reservoir play in Texas and Louisiana since discovery of the Fairway Field in 1960.
Goodrich Petroleum Corp. of Houston recently completed its second and third horizontal James Lime wells drilled in the Angelina River Trend in Nacogdoches and Angelina counties.
The company’s initial James Lime horizontal well was drilled to a total depth of 14,960 feet with an approximate 5,400-foot lateral, and had a maximum test rate of 14 million cubic feet/day and a 24-hour initial production rate to sales of 6.8 million cubic feet/day.
St. Mary Land & Exploration Co. of Denver reported it had increased its acreage position in the James Lime trend to roughly 50,300 net acres by year-end 2007. The company said its leasing efforts are ongoing and competition in the play area has increased markedly.
South Texas, Tertiary and Cretaceous
More than 2,000 well completions were reported over the past two years in South Texas trends, which are mostly gas-producing.
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.
Most of the wells were vertical, but horizontals were drilled in all plays – particularly in the Olmos. Except for the Frio these are tight-sand trends that require hydraulic fracture treatments.
Operators include several major companies, plus large and small independents.
Marathon Thrustbelt Play, West Texas
Using a do-it-yourself model, SandRidge Energy Inc. of Oklahoma City has drilled more than 200 wells in the past four years along the leading edge of the Marathon Thrustbelt south of Fort Stockton, in Pecos County.
Production from vertical well completions in thrust sheet targets – Dimple Limestone, Tesnus sands and fractured upper and lower Caballos Novaculite – has increased to 200 million cubic feet/day. An abstract by Dick Boyce in the March 2008 West Texas Geological Society Bulletin suggests that autochthonous Wolfcamp sands also are contributing to production.
SandRidge, formerly Riata Energy, built momentum in this play by experimenting with drilling and completion techniques – using its own equipment and crews – on both lands owned outright by the company and leased properties.
It recently embarked on a major 3-D seismic acquisition program, and a 30-rig drilling program is under way to exploit Pinon field and to drill newly identified prospects.
Bone Spring Formation, West Texas
Most of the Bone Spring formation production and field development has been historically concentrated in 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 basin.
Current activity is concentrated in Loving, Pecos, Reeves, Ward and Winkler counties, with primary targets in the Third Bone Spring sandstone.
New exploration techniques of these sands include horizontal drilling and acid fracturing with proppant. Wells produce in the range of 170 barrels/day and 350 mcf/day.
The most active operators in the play are Chesapeake Operating of Oklahoma City and Cimarex Energy of Denver.
‘Wolfberry’ Play, Midland Basin, West Texas
Operators chasing production from the Wolfcamp and Spraberry formations in the same area began referring to the play as “Wolfberry,” which is how it’s now known by the local industry.
The Wolfberry low-permeability oil play is centered in Ector, Midland and Upton counties, and probably includes Glasscock and Reagan counties.
Reservoirs are slope and basin systems, including debris flows, grain flows and turbidites composed of carbonate detritus in the Wolfcamp or terrigenous sand and silt in the Spraberry/Dean. Natural fractures may also be a factor.
The target zone is up to 3,000 feet in thickness at depths of 7,000-10,000 feet. Selected intervals are perforated and fraced. Completions may include nine to 12 separate frac jobs, starting lower in the Wolfcamp and moving up-section.
In the 1980s and 1990s, the Wolfcamp basinal carbonate play was pursued using vertical wells to explore 3-D seismic facies prospects.
Many of those wells were abandoned because of low permeability. The Wolfberry play revisits many of those unsuccessful areas, with multistage frac jobs making the difference in viable production.
In some cases the lower zones may be put on production for several months before the upper zones are added and commingled. Initial production ranges from 30 to 125 barrels/day.
Pioneer Natural Resources of Irving, Texas, drills 400 Spraberry wells a year in the play area, and some of these wells qualify as Wolfberry. Other operators cited are Oxy USA, St. Mary Land & Exploration, and ExL Petroleum Co., Henry Petroleum Corp. and Cambrian Management Ltd., all in Midland.
Brookeland Field, East Texas, Austin Chalk
Horizontal-well development of the Austin Chalk reservoir in Brookeland Field continues. Major operators Ergon Energy Partners and Anadarko E&P dominated drilling action on the Texas side in the past year.
The Brookeland trend passes through parts of Tyler, Newton, Sabine and Newton counties, extending 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 2,000 barrels/day and 18 mcf/day. High oil and gas prices drive this play, in which typical decline rates are around 80 percent in the first year.
Cleveland Sand Horizontal Play, Lipscomb County (Northeast Texas Panhandle)
Jones Energy Ltd. of Austin is leading the way in redevelopment of the tight Pennsylvanian Cleveland sand using horizontal wells. The sands are in eastward-prograding deltas, fluvial trends and incised valley deposits, according to publications by the BEG’s Tucker Hentz.
Over 350 horizontals have been drilled in this northern Panhandle play, exploiting sands with microdarcy permeability. Ultimate recoveries are 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. Jones operates for itself and also on behalf of several major companies whose large acreage spreads in the area are held by production.
Edwards Reef Trend, Live Oak County, South Texas
Pioneer leads this resource-type play, based on its success in the Pawnee Field. It estimated 300 bcf of ultimate expected production at Pawnee and reported eight new discoveries on the trend.
Development drilling was occurring where 3-D seismic is available, and more than 900 square miles of new 3-D seismic are planned. Dozens of north-northwest directed horizontal wells have been permitted.
The company completed five wells in Live Oak County in 2007, with a median peak production rate of approximately 1.5 million cubic feet/day.
Barnett Shale, Fort Worth Basin
Any summary of Texas drilling activity has to include the Barnett shale in the Fort Worth Basin.
Total producing wells now number about 8,400, and daily production for the play in 2007 was about 2 bcf. A total of 3.6 tcf has been produced, with 175 operators completing more than 3,600 wells in the play in the past two years.
Hot spots continued to be Johnson and Tarrant counties, but the Baker-Hughes rig count in late February showed 171 rigs active throughout the play, almost all engaged in horizontal drilling.
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.
Devon Energy of Oklahoma City continues as top producer, but Chesapeake (also of Oklahoma City), XTO Energy of Fort Worth and EOG Resources of Houston, also are very active.
Both EOG and XTO recently presented development plans indicating that recoveries of 50 percent of gas-in-place may be possible, utilizing aggressive downspacing, in some cases to less than 400 feet between adjacent horizontal wellbores.
Chesapeake recently reported it expects to complete a Barnett well every 15 hours, on average, through 2012. The company also had excellent results in the early phase of a drilling program beneath the Dallas-Fort Worth Airport.
The city of Fort Worth estimates that more than 2,000 wells will be drilled from some 500 surface locations within the city limits, all subject to comprehensive permitting provisions, including setback, noise and lighting restrictions.
Editor's Note:
Play information in this article was provided by Eric Potter, associate director for the Bureau of Economic Geology, Jackson School of Geosciences, the University of Texas at Austin