Multiseam Coal Stimulation Using Coiled-Tubing Fracturing and a Unique Bottomhole Packer Assembly

Multiseam Coal Stimulation Using Coiled-Tubing Fracturing and a Unique Bottomhole Packer Assembly G. Rodvelt; G. Rodvelt Halliburton Energy Services, Inc. Search for other works by this author on: This Site Google Scholar R. Toothman; R. Toothman CONSOL Energy, Inc. Search for other works by this author on: This Site Google Scholar S. Willis; S. Willis Halliburton Energy Services, Inc. Search for other works by this author on: This Site Google Scholar D. Mullins D. Mullins Halliburton Energy Services, Inc. Search for other works by this author on: This Site Google Scholar Paper presented at the SPE Eastern Regional Meeting, Canton, Ohio, October 2001. Paper Number: SPE-72380-MS https://doi.org/10.2118/72380-MS Published: October 17 2001 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Get Permissions Search Site Citation Rodvelt, G., Toothman, R., Willis, S., and D. Mullins. "Multiseam Coal Stimulation Using Coiled-Tubing Fracturing and a Unique Bottomhole Packer Assembly." Paper presented at the SPE Eastern Regional Meeting, Canton, Ohio, October 2001. doi: https://doi.org/10.2118/72380-MS Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex Search Dropdown Menu nav search search input Search input auto suggest search filter All ContentAll ProceedingsSociety of Petroleum Engineers (SPE)SPE Eastern Regional Meeting Search Advanced Search AbstractIn Virginia, coalbed methane (CBM) production can occur from as many as 25 seams with thicknesses from 0.5 to 6 ft. Fracture stimulations have evolved from single-stage, limited-entry designs to multiple-stage treatments with corresponding increases in gas production as additional staging was added. For mechanical and economical reasons, three to five stages have been typical. With the introduction of an integrated coiled-tubing (CT) rig and a specially designed bottomhole packer assembly (BHPA), additional staging to cover individual coal seams is possible.A five-well project in Buchanan County, Virginia was chosen for coiled-tubing fracturing (CTF). Job designs that use current fluid and proppant loading were modified for the injection rates and pressures expected in treating down 3,800 ft of 2 3/8-in. coiled tubing. Treatment procedures, fluid systems, and treatment graphs are presented illustrating job designs used to treat 11 to 19 different stages in each of the five wells. Economics are presented for accessing additional productive coal footage and the resulting net present value (NPV) gained. Lessons learned and recommendations for improving the efficiency of CTF in the Appalachian Basin are included.IntroductionCBM production in Virginia has increased since the production of natural gas was first documented in 1948.1 As reported by Guoynes, et al.,2 the CONSOL, Inc. (includes Consol Energy, Pocahontas Gas Partnership, and Buchanan Production Company) group has been stimulating both mined and nonmined coal for gas production with over 900 wells stimulated by the end of 2000. All of these wells have been fracture-stimulated to enhance gas production. Unlike thicker coal seams found in the San Juan and Black Warrior Basins,3 Appalachian coal is broken into a greater number of thinner seams, presenting a unique problem for stimulation engineers.Early attempts to stimulate all coals together were limited to perforating a few holes in each seam and attempting a "limited-entry" frac design as described by Spady.4 Proppant placement was limited, and extremely high rates and pressures were needed to overcome the stress contrast over the intervals. Associated production problems caused by too little fracture conductivity led engineers to look for ways to stimulate each coal more precisely. Design changes that incorporated the use of frac baffles or frac plugs improved completion success, resulting in higher production rates. Directing the treatments into individual coal seams was still necessary because pump-in tests (after frac) had revealed that some intervals were not being stimulated. Grouping the coals was bypassing some productive pays. McConkey and Stromquist5 had reported on a more economical method for completing bypassed Medicine Hat sands in the shallow-gas region of western Canada. By using CT, an integrated rig, and a new retrievable packer, they were able to complete multiple zones with one trip in the well more economically than previous treatments.In this project, one of the five Buchanan County wells indicated 22 separate coal seams. After review of the stimulation design, 19 stages were planned with CTF (with 3 seams being close enough to straddle together). Before the CTF process introduced in this paper, accessing all 22 coal seams mechanically in an economical manner would have been impossible.GeologyMethane production is obtained from the mined Pocahontas No. 3 (P3) at a depth of 1,500 to 2,500 ft from the surface. Production is also obtained from thin coal seams overlying the P3 seam. As many as 12 to 25 coal seams overlay the P3 seam, ranging in thickness from 0.5 to 6 ft (Fig. 1). These coals are in a gross interval of approximately 1,000 ft. The gas content of these coals range from 450 to 650 scf/ton. Keywords: perforation, coiled tubing, complex reservoir, stimulation, coal bed methane, coalbed methane, fracturing fluid, spe 72380, gas production, proppant Subjects: Hydraulic Fracturing, Unconventional and Complex Reservoirs, Fracturing materials (fluids, proppant), Coal seam gas, Well Integrity, Zonal isolation This content is only available via PDF. 2001. Society of Petroleum Engineers You can access this article if you purchase or spend a download.

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