Abstract
In low-permeability formations, natural fractures, fissures, and other geologic heterogeneities are important considerations in the design of hydraulic-fracture treatments. In some formations, it is considered beneficial to capitalize on these conduits to establish a greater network of connection to the reservoir. In the Bakken shale, near Westby, Montana, a simple planar fracture was desired because complex fracture growth could result in connectivity to a zone of nonproductive interest and led to the following issues:
Higher rates, which could result in extreme fracture complexity and limited fracture extension.
Inability to effectively place proppant for conductivity.
Excessive fluid leakoff caused by high net pressures requiring large pad volumes.
Connection to water-producing zone.
Less aggressive proppant schedule because of likelihood of screenout.
Increased cost, footprint, personnel, and equipment on location.
With an understanding of the formation-rock properties, stresses, and the natural fracture system, the treatment design parameters were established to help ensure lower treatment pressures and optimum fracture extension in the zone of interest. This paper presents the successful execution of a multi-interval fracture-stimulation treatment for a long-lateral horizontal completion in the Bakken shale using a state-of-the-art hybrid coiled-tubing (CT) system and hydrajet-assisted fracturing (HJAF) technology. The new approach incorporated the following technology:
Low-rate treatment schedule.
Multiple-fracture stimulation treatment.
Aggressive proppant-treatment schedule.
Higher gel viscosity to encourage desired fracture growth and proppant transport.
Hydrajet perforating.
Dynamic fluid diversion to isolate treatment to intended zone.
State-of-the-art hybrid CT system.
