The foothills area of Alberta, Canada is a challenging exploration area for reservoir definition as well as drilling and completions. The complex geologic structures as well as the logistical difficulties in the area make it a costly area to drill and exploit. During the past three years, several multilateral wells have been successfully drilled and completed in this area. Some of these incorporated advanced drilling and completions system which allowed greater flexibility in both the drilling and testing/production phases of the wells. This paper presents case history descriptions of the application of advanced multilateral technology regarding drilling and completion systems for these wells and the capabilities which were utilized to successfully drill, test, and produce the wells.
During 1997 and 1998, Mobil Canada drilled and completed three wells in the Foothills area of Alberta using multilateral technology (two are discussed in this paper). These wells included several "first" for the Canadian industry, and represented a departure from previous drilling and completion practices for the area. These wells applied new technology in, both the drilling and completion phases of the operations to maximize the utility of the wellbore, while attempting to accelerate production.
The primary target zone for these wells is the Turner Valley formation. The reservoir is mostly dolostone with intercrystalline and moldic porosity. Natural fracturing contributes to reservoir permeability and is a consideration in the location of wellbores and in the design of well trajectories. Reservoir traps were formed by thrust faulting, so the identification of structurally favorable positiOns is accomplished using both, geophysical interpretations and correlation data during the drilling operations. In some cases, the drill bit will encounter stacked occurrences of the target formation due to the severe thrusting in the area. Figure 2 represents the Stolberg well as an example, with multiple sheets and fractures. The seals over these reservoir traps are supplied by the overlying tight formation of the Fernie and Luscar Groups.