Liner Completion Difficulties Resolved With Expandable Liner Top Technology

Abstract

Liner top packers, which are run as a standalone unit or integrally with conventional liner hangers, are set through the application of weight applied through the drill pipe or landing string. The capability of the liner top packer to seal at the stated pressures rated for which they are designed requires that a sufficient setting force of up to 355857.7 N (80,000 lbf) be applied through the drill pipe to the packer mechanism. Recently, work performed by an operator in Latin America showed the limitations of this process when used in shallow liner top installations where the available string weight alone to apply a sufficient setting force to the liner top packer is not available. Picking up a string of large drill collars in order to have the capability to supply the significant setting force required was an alternative. However, it was not a preferred option, safety being the main concern, followed by handling time, as was seen on the first well utilizing conventional liner hanger and liner hanger packer technology. The expandable liner hanger (ELH) was developed as a solution to resolve the problem of weight down required to set the liner top and allowing a setting force to be applied to the packer elements locally through the hanger body with the use of hydraulic pressure. The setting force for the packer is measurable and consistent, ensuring that a liner top seal and hang weight is obtainable without requiring weight down. This system contains no moving parts, which makes it possible to function with a drill string. Once deployed in the well, the liner hanger body expands radially through the pressurization of its elastomeric elements, thus, creating a gas-tight seal and achieving zonal isolation. The operator chose to deploy the expandable liner hanger system on two subsequent wells following the initial attempt to utilize a conventional system approach. The ELH installations were successful, saving the operator several days of rig time on each well. The case study discussion and system description presented in this paper will explain the flexibility and integrity of the expandable liner hanger in providing a liner top seal upon setting in a shallow liner top installation. Introduction Historically, problems obtaining a good primary cement job at the top of the liner have been associated with the installation of liners in oil and gas wells. Conventional liner hanger systems have relied upon the primary cement job to provide liner top pressure sealing integrity within the liner/casing overlap. In many wells however, cementing the complete liner and liner lap is often not achievable due to various problems, which include loss of circulation, fluid loss or other wellbore/formation conditions. In cases like these, obtaining a primary cement seal across the liner lap is not obtainable, and a liner top packer must be deployed on a second run to make the primary liner the top seal.