New Method for Perforating,Isolating, and Fracturing Multiple Coal Seams During a Single Well Intervention

摘要

In coalbed methane (CBM)wells around the world, multiple coal seams must be completed and produced simultaneously, and typically are hydraulically fractured, to achieve economic production rates. Since the mid-1990s coiled tubing (CT) fracturing techniques, utilizing a dual-packer bottom hole assembly (BHA), have proven effective in straddling and treating individual coal seams, but not without drawbacks: ? Large-diameter CT is required to achieve adequate injection rates. ? All pay zones must be perforated prior to the treatment, giving rise to: 1.Potential crossflow into the annulus above the BHA and potential well-control issues during treatment. 2.Zones that can not be fracture stimulated due to these issues. An innovative new fracturing method overcomes these two drawbacks while providing superior zonal isolation at similar or lower total cost to the operator. The method uses conventional CT sizes (typically 1.75" or 2" OD))and does not require perforating beforehand. Perforations are generated through hydraulic jets in the BHA, and a rugged compression packer provides zonal isolation below the perforations while the treatment is pumped down the CT/casing annulus. After the treatment is completed, the BHA is moved up to the next interval and the process repeated, with the packer isolating the previously stimulated zones below. While this process also has application in conventional wells worldwide, this paper will focus on case histories from CBM stimulation campaigns in North America.