Abstract
Conventional liner-hanger systems typically rely upon the primary cement job as the main method of sealing the liner/casing overlap, and liner-top packers are run either integrally with the liner hanger or separately in a second trip. In certain applications, however, cementing the complete liner may not be feasible or obtaining a primary cement seal at the liner top may not be achievable; in these situations, a liner-top packer must be used as the primary seal. In cases where the top of cement is above the overlap but below the hanger, the liner top packer is used as a back-up seal for the overlap.
Almost all liner-top packers that are run integrally to the liner hanger are set through the application of weight applied through the drill-pipe or landing string. The capability of the liner-top packer to seal with a single element at the maximum pressure rating requires that a sufficient setting force of up to 100,000 lbf be applied through the drill pipe to the packer mechanism. Work performed in Latin America recently showed the limitations of this process and how shallow liner-top installations might not have the string weight to apply a sufficient setting force to the liner-top packer.
A conventional alternative to an integral packer design is a secondary tie-back packer, but this alternative requires at least two extra trips into the wellbore and picking up of a string of large drill collars to supply the significant force required.
A solution was found that was capable of resolving this problem, and the innovative technology applied will be the focus of this paper. An expandable liner hanger that allows a hydraulic setting force to be applied locally to the hanger was used. The setting force for the packer was measurable and consistent. With the success experienced on the first well, the expandable liner hanger was used in subsequent jobs, and in all of them, the operator saved several days of rig time in addition to experiencing a successful completion.
