Despite the increasing use of nitrogen breakdowns without proppant in the dry Horseshoe Canyon coals, introduction of proppant was shown to be beneficial to production.
North American demand for natural gas has resulted in attractive commodity pricing and thus a renewed interest in unconventional reserve exploration in Canada. Recent activity in Coal Bed Methane (CBM), or Natural Gas from Coal (NGC), has yielded two primary exploration targets that are promising; one of which is the Horseshoe Canyon coal.
The family of Horseshoe Canyon Coals is shallow and range in depths from about 492 ft (150 m) to 2,789 ft (850 m). Even though broadly referenced as Horseshoe Canyon, the stratigraphic range of the coal is from the Edmonton down to the Belly River formations which includes the Horseshoe Canyon formation. These coals are better described as seams or stringers and are most frequently between 1.5 ft and 5 ft in thickness and generally no more than 9.8 ft in thickness. Reservoir pressures at these depths average from 250 psi (1,700 kPa) to 510 psi (3,500 kPa). Production varies due to the commingling of up to 30 stringers per well bore and total well bore production ranges from 35 Mscf/day (1 E3m3/day) to 636 Mscf/day (18 E3m3/day). Horseshoe Canyon coals are generally accepted to be of very low water saturation, low gas production rates and produce little to no insitu water production upon completion.
The most common completion technique is the sequential stimulation of each stringer by the use of coiled tubing. Marginal gas production and intolerance to completion fluids has resulted in evolution of fracturing systems including binary foamed water, CO2 / N2 proppant, conventional borate water, some hydrocarbon based and pure proppantless nitrogen systems pumped at high rates.
Several issues that are dealt with in this paper include concurrent sandstone and coal perforating and stimulation, and a method for comparing coal to coal and coal to sand production. This paper will be used to examine the incremental sandstone contribution to the overall production of the well. Effect of sanding off the well will be examined as to its impact on production.
The objective of this paper is to present findings of an 18 well pilot study in an ongoing 90 well case study completed in a Horseshoe Canyon development near Red Deer, Alberta, Canada. An paper submission is being chosen, and more updated data will be presented at the conference.
Author(s): B.A. Rieb and T.T. Leshchyshyn, BJ Services Co. Canada
Paper Number: SPE 96864