Single Trip, Multistage System Delivers Fast, Efficient Solutions in Deepwater

Abstract

The Lower Tertiary Wilcox formations are hard rock, low permeability formations that contain billions of barrels of oil. Fracture stimulation is required to allow access to these reserves. Multi-zone, single trip (MZST) frac pack systems have been the lower completion method of choice to allow operators to reduce costs when completing these lucrative reservoirs. The use of MZST systems reduces the time required to complete these wells versus the conventional cased hole frac pack system methods. However, these systems are relatively expensive, complex, and have similar space out limitations as the conventional systems that restricts reservoir contact. Despite the large quantity of reserves and production potential of Lower Tertiary wells, the operating environment and costs required to access these reservoirs makes this a marginal play. In order to reduce the commercial risk associated with these reservoirs a step change, 30 to 50% reduction in well construction and completion costs, is required. In order to achieve this cost reduction target, field proven unconventional multi-stage open hole stimulation technology was adapted for these reservoirs. Ball-activated multi-stage Frac sleeves with open hole packers, were integrated into deepwater operations to significantly reduce well construction and stimulation costs. The system design allows open hole deployment of a frac completion into a short radius borehole and the rapid stimulation of multiple zones in a single trip. As a result of this design, it is now possible to stimulate up to 22 stages and prevent the proppant from flowing back during production. In addition, the Frac sleeve system allows the operator to maximize production by strategically placing each zone in the optimum location based on LWD data with virtually no space out limitations. The stimulation design can then be optimized to ensure that the pay zone is properly stimulated while minimizing the risk of premature screen out. In addition, this system offers the only viable option for both casing and open hole should borehole sizes change as a result of geomechanical or drilling issues in the complex reservoirs. If the primary well design option for casing is not accomplished, adjustments can be made thereby eliminating the need to abandon or sidetrack the well. This paper will discuss the flexibility and cost savings that this system offers along with case histories and lessons learned from recent deployments in the Wilcox formations. A brief discussion of stimulation design will be included with regard to optimization of the frac stages and their interaction with the system. Detailed frac designs will not be included.