Abstract

A common limitation of fracture stimulation is the inability to control placement of a hydraulic fracture, particularly in a multiple perforated wellbore. This shortcoming can be overcome by integrating the diverse technologies of coiled tubing with hydraulic fracturing. The combination provides the option to perform conventional hydraulic fracturing through a coiled tubing string. Such an operational modification adds versatility to the fracturing procedure. It also permits control of fracture placement and hence can be used to improve the economic benefits associated with multiple staged hydraulic fracturing. This fundamental procedure can also be used to effectively stimulate bypassed payzones where conventional fracturing may be limited by economical and operational considerations.

The effectiveness of coiled tubing fracturing operation can be constrained by excessive friction pressures, equipment limitations and limited fluid and proppant volumes. Its application thus requires specialized fracture fluids, additional operations, and alternative design procedures to ensure an efficient and successful fracture stimulation program.

The paper explains the motivation for these coiled tubing fracture treatments. Operational and design requirements associated with this technique are identified. The various constraints associated with this unconventional technique are largely overcome by using a non-polymeric, viscoelastic surfactant fluid system whose relevance to this technique is discussed. These modifications are subsequently combined with current fracturing and coiled tubing practices to outline a comprehensive methodology for application of coiled tubing conveyed fracture treatments.

The paper also describes this procedure with two case studies. These illustrate its application in diverse reservoirs that span a range of formation depths (600 ft – 8,000 ft), well completions (new and existing wellbores) and fracturing practices (multi-staged and single reservoir bypassed payzones). The diagnostic, design and application procedure applied in each case is discussed.