An emerging resource play, centered on productive Woodbine fields in Grimes, Madison and Brazos counties in East Texas, appears to be in the early stages of commercial development. Horizontals drilled by a handful of small companies into the Woodbine-Eagle Ford section are highlighting the play’s potential.

Geology. The Upper Cretaceous Woodbine-Eagle Ford interval lies unconformably above the Buda limestone and unconformably below the Austin Chalk. The lower portion, the Woodbine, consists mainly of sandstone and shale that are non-marine in the northern and central parts of the East Texas Basin and marine in the south and southwestern portion. The Eagle Ford overlies the Woodbine, and consists largely of marine, gray to dark-gray shale with fine- to medium-grained porous to nonporous sandstone members.

One active area targets productive sands at Kurten Field found in the upper part of a thick section of black marine shale of the Woodbine-Eagle Ford section, just below the Austin Chalk. The entire interval is approximately 800 feet thick. Multiple sands have been identified in the field and designated “A” through “E” from top to bottom.

The field’s principle reservoir sands are the B, C and D, with the C sandstone being the best developed and most extensive. The sand consists of fine- to medium-grained, laminated sandstone with porosity ranging from 10% to 17% and relatively low permeability.

Targets for horizontal wells are the interbedded fine-grained sandstone and shale or the bioturbated facies, as well as the lesser-developed thinner, interbedded sand intervals.

Also of significant interest in the area is the Eagle Ford shale, which appears to have several potential oil zones. Depth to the reservoirs ranges from 7,400 to 9,400 feet.

Drilling activity. Most historical Woodbine fields were exploited using vertical wells with minimal fracture stimulations, since oil production was from shallow depths and reservoirs that had high porosity and permeability. Deeper targets, like the gas trends of Polk and Tyler counties, required more intense fracture stimulation for development.

In Kurten Field, vertical Woodbine well completions used through the 1970s and 1980s (which were fracture stimulated) had cumulative production of 10,000 to 200,000 barrels of oil per well (average of approximately 37,000 barrels per well). Analogous horizontal wells in the field and surrounding area have IPs from 250 to more than 1,000 barrels per day with some gas and little water.

Estimated ultimate recoveries (EURs) are thought to be 350,000 to greater than 500,000 barrels of oil.

Lateral length on new horizontal wells ranges from 5,000 to more than 8,000 feet, with 20- to 38-stage fracture stimulations. Reported well costs, including drilling and completion, are $4- to $6 million.

In this area, multistage fracture stimulations and horizontal wells have been used to create permeability in not only the Woodbine sands and Eagle Ford shale, but also the Buda and Georgetown reservoirs.

Early Woodbine movers. Several companies have accumulated acreage in the East Texas Woodbine-Eagle Ford trend. Chesapeake Energy Corp. and Devon Energy Corp. are two of the larger companies paying attention to the Eaglebine play in Grimes, Madison and Walker counties. Others having positions in the play include Energia Tejas LLC, Exterra Energy Inc., Southern Bay Operating LLC, Crimson Energy Partners III LLC, PetroMax Operating Co. Inc. and Sun Resources NL (an Australian company).

Toreador Resources Corp./ZaZa Energy LLC has approximately 80,000 gross acres in the East Texas Woodbine-Eagle Ford trend with plans to expand to 100,000 over the near term. The company is planning to drill multiple wells testing several potential reservoir targets, including Woodbine and Eagle Ford.

Gastar Exploration Ltd. has approximately 19,400 net acres in Leon and Robertson counties. It estimates well costs of approximately $6 million with EURs of 140,000 to 400,000 barrels of oil equivalent. The company has drilled four wells to the Glen Rose and Eagle Ford-Woodbine section that they are currently monitoring.

New Gulf Energy LLC (a subsidiary of Petro Texas) and partner PetroMax have completed 13 horizontal wells so far in their project in Madison, Brazos and Grimes counties. Recent laterals have been in excess of 8,000 feet with up to 38 frac stages. Well initial production (IP) rates have topped1,000 barrels of oil and 300,000 cubic feet of gas per day. A recent well, Alphin-1H in Madison County, had an IP of 1,395 barrels and 800,000 cubic feet of gas per day. With the latest well improvements, the company estimates EURs of more than 500,000 barrels of oil.

Clayton Williams Energy Inc. has a large land position in Robertson, Burleson and Lee counties, with its primary target the Austin Chalk in Giddings Field. However, the company has drilled and is producing from four Eagle Ford wells in Burleson and Lee counties. The company is drilling 4,800- to 5,500-foot laterals with nine- to 15-stage fracs, for $3.1- to $3.3 million.