Demonstration of massive fracturing to provide gas production from tight gas sands in the Piceance Basin production from tight gas sands in the Piceance Basin was the objective of this work by Mobil. The project was partially funded by the U.S. Department of Energy. During the period 1974–1979 two wells were drilled, tested and fractured. Encourging results were obtained from the second well.
The first well, Brush Creek Unit 1-25, located near Collbran, Colorado, was drilled to 10,330 ft. Three Mesaverde formation intervals were tested and two of these were fractured. Results were discouraging because of low formation conductivity which ranged from 0.005 to 0.15 md-ft in the three zones. The second well, Piceance Creek Unit 31-13, located near Rio Blanco, Colorado, was drilled to 10,800 ft. Nine intervals were tested in the Mesaverde and Fort Union formations and six fracturing treatments were performed. Combined flow from all of these zones began at 3.2 MMSCF/day and declined to 1.7 MMSCF/day in 207 days.
Details of drilling, testing and completion are given in this paper along with estimates of fracture effectiveness. Preliminary economics are also given, based on the short production history available.
This report discusses a demonstration of the use of massive hydraulic fracturing (MET) in Mesaverde and Ft. Union (Ohio Creek) sands in the Piceance Basin. The work was performed by Mobil with partial funding by the U.S. Department of Energy. Progress of the work has been reported at DOE Symposia and details are summarized as of September 30, 1979 in a final report.
The presence of very large gas resources in low permeability reservoirs of the Piceance Basin and other permeability reservoirs of the Piceance Basin and other Rocky Mountain basins is well known. The U.S. Government, Mobil, and other private companies have mounted a substantial effort to convert at least part of these resources to recoverable reserves. part of these resources to recoverable reserves. Some of these efforts have been previously reported.
Mobil's efforts to obtain commercial gas from the Mesaverde reservoir of the Piceance Basin began in 1971 After extensive analysis and planning, the Brush Creek Federal Unit near Collbran, Colorado was selected as the site of the first well (see Figure 1).
The well, Brush Creek Unit #1-25, was spudded in April, 1974. Attempts to fracture a first zone in July, 1974 resulted in a screen out after pumping less than 300,000 pounds of a planned 1 million pound treatment. Estimated properties of this zone are kh = 0.15 md-ft, h = 50 ft, k = 0.003 md. This zone subsequently was plugged back. A second zone (7516–7720) was successfully fractured with 1 million pounds of sand. After fracturing, the well was pounds of sand. After fracturing, the well was production tested for a period of about two months production tested for a period of about two months followed by a five month pressure buildup test. All tests indicated the zone to have a kh of about 0.04 md-ft, too low to be commercial. A third zone at 7246–7330 ft was also tested, yielding a kh of 0.005 md-ft. The well was subsequently abandoned.
The Piceance Basin is asymmetrical with steeper dips on the east side. The Piceance Creek Field is located in the deeper, northeast part of the basin. (See Figure 1.). The Williams Fork Formation comprises most of the Mesaverde Group and has an overall thickness varying from about 3300 ft to 4200 ft west to east across the Piceance Creek Unit. (See Figure 2.). The Mesaverde is overlain by a relatively thin Ohio Creek (frequently referred to as Ft. Union) interval, followed by the Wasatch. Underlying the Mesaverde are the transitional or marine shales and sands of the Mancos Formation. The Williams Fork contains numerous tight, lenticular, gas bearing sands.
Sands lens continuity can only be inferred from general studies in the basin since well-to-well correlation of individual sand intervals from available logs is difficult or impossible.