Expandable Liner Hanger Provides Cost-Effective Alternative Solution

Abstract

Abstract Establishing and maintaining hydraulic integrity between liner hangers and the base casing in which they are set has long been one of the most problematic areas facing operators. With failure rates on pressure seals in overlaps now exceeding 40% in some regions, the need for a solution to this decades-old problem has reached a critical level. Although new approaches have included turbolizers for cementing overlaps, special cements, and liner-top packers, many problems still remain. An operator and a service company are working together to develop a new drill liner hanger based on patented expandable-casing technology. This technology is being used to diametrically expand solid tubulars for a variety of drilling, completion, and remedial applications. The new liner system is designed to totally eliminate the liner lap by expanding an elastomer-coated casing into intimate contact with the casing from which the liner is being hung. Preliminary results indicate the new hanger design can result in load-carrying and burst capacities that exceed the capacity of the previous casing string. Furthermore, the overlap samples tested to date have all resulted in annular seals that have exceeded 10,000-psi differential capacities. In fact, casing has always failed during large-scale testing before any overlap leaks developed. This paper discusses the design and application of the new liner hanger and presents laboratory and field-test results. Introduction One of the long-standing challenges facing operators during well construction has been the establishment and maintenance of hydraulic integrity between liner hangers and the casings in which they are hung. In recent years, liner-top packers have been used to establish a pressure seal immediately above the liner hanger, while traditionally cement has been used to establish a pressure seal in the casing/liner overlap directly below the hanger. However, both methods of creating hydraulic integrity have frequently been unsuccessful, often because of inherent weaknesses in the design of conventional liner hangers (Fig. 1). A recent informal survey of several Gulf of Mexico operators revealed, for example, that 30 to 50% of the pressure seals in overlaps failed. Such failures not only reduce the effectiveness of the applications for which the liners are intended, but they also increase well costs because of the remedial operations that must be undertaken.