Large-Bore Expandable Liner Hangers Significantly Improve Operational Cost in a Deepwater Gulf of Mexico Well

Abstract

Abstract Offshore operations generally require that when casing strings are greater than 13-5/8-in., they are " hung-off?? in the casing hanger at the wellhead. Although this action is time consuming, and usually is costly, it has been the most widely used method to date. Other solutions have been needed, and finally, a new expandable technology that shows promise of offering a better alternative has been developed. An expandable large-bore liner hanger that allows an operator to set a liner instead of a full string of large casing has been designed. After successful application of a new large-bore expandable liner hanger in another part of the world, plans for another application in the GOM were begun. Due to wellhead restrictions in the new GOM application, the original product design required significant design modifications. These changes were completed, and this paper discusses the development and successful installation of the first large-bore expandable liner hanger designed for ENI's Triton well in deepwater Gulf of Mexico. The installation provided the following advantages:Casing placement flexibilityImproved support reliabilityA seal at the top of the casing.Capability to rotate and reciprocate during cementingCost savings from requiring less casingElimination of the possibility that the casing could not be seated properly in the casing hangerElimination of complications and high costs inherent to hanging the hanger in the mudline/casing. The installation of the large-bore expandable liner hanger saved the operator the cost of 2300 feet of 16-in. casing, which greatly improved job economics. Other benefits were the reduced equivalent circulating density and the capabilities of rotation and reciprocation, possible with the new large-bore expandable liner hanger; which improved cementing quality. In addition, it is expected that the latter benefit would further be noted in the future from increased well life and elimination of the future remediation work. Finally, expandable liner hangers also can improve operations on floating rigs in deepwater regions, because no liner space-out is required; this eliminates pressure integrity issues that can occur in conventional systems with improper space out. Introduction The original expandable liner hangers were introduced to the industry to resolve the problems experienced when the traditional liner hangers were used in difficult well scenarios (Cantu et al, 2004; Nida et al, 2004). The main components of the expandable liner system were an integral liner hanger/packer assembly made up of an upper polished bore receptacle (PBR) and elastomeric elements bonded directly to the body of the hanger. Until recently, there had been no requirement for large casing size expandable liners; thus, these had only been designed for small casing sizes. Figure 1 shows the basic components of the earlier expandable liner hanger system. In operation, the bonded elastomeric elements compress against the casing ID as the hanger expands to virtually eliminate leak paths between the liner hanger and casing and to provide pressure integrity at the top of the liner (Moore et al, 2002). The system has an impressive capacity to support tension and compression loads.