Expandable Liner Hanger Application in Arduous Well Conditions Proves Reliability: A Case History

Abstract

Proposal In an effort to increase production in the gas fields of East Texas, horizontal wells have become the standard, as they have in many regions worldwide. Many times the horizontal section is preceded with a drilling liner to cover the build section of the well and isolate weaker fracture gradient zones prior to penetrating the production interval. Previously, many operational challenges were encountered during liner installation, resulting in costly shoe and liner top remedial operations or the inability to reach the total depth of a hole section. Primary among the hurdles are successfully deploying the liner across the weaker zones and negotiating the hole angle. With the recent advancements made in the field of solid expandable tubular technology, several innovative products have developed from the core technology. One of these products is the expandable liner hanger. This product has been proven to greatly enhance liner operations in the well construction industry. Expandable liner hangers offer many novel features not available or applicable to conventional liner hangers. These features include radial geometry and a hanger / packer body construction with no moving parts. The primary benefits of this system are superior seal, improved installation reliability, and a significant reduction in time required to complete the installation and to resume drilling operations. These benefits and others derived from the features listed above will be discussed in detail in this paper including results from a recent case history in the Mossy Grove field of East Texas. Introduction Historically, many problems have been associated with the installation of a liner in oil and gas wells. As wells became more complex and tortuous due to drilling technology innovations, it became apparent that liner systems needed the ability to push, wash, and rotate to get the liner to the required setting depth. This has been accomplished with most modern types of liner hangers and setting tools to some degree, but at the expense of reliability. Conventional liner tops are prone to failure and an informal study performed in 1999 among operators in the Gulf of Mexico highlighted several problems associated with liner tops during the 18 months prior to the survey1(Fig. 1). Prevalent among the failure modes were:Liner top integrity - lap squeezesPacker/hanger/centralization issues - preset, or failure to setShoe integrity - shoe squeezes These results confirm earlier studies that identified the effort and expense that operators required to ensure liner top hydraulic integrity.2 Typical methods of achieving this integrity include:Multiple liner top squeezes after failed primary cementingOne or more "second trip" liner top isolation packers installed to ensure liner top hydraulic integrityTack and squeeze liner setting technique (tacking the shoe with cement and then intentionally squeezing the liner top without attempting to cover the liner top during the primary cementing job) Many failures are caused by the design of very complex liner hangers. Conventional hanger/packer slips and cones provide a lodging place for cuttings to build up. Two results of this build-up are increased equivalent circulating density (ECD) leading to lost circulation and preset of the hanger or packer mechanically as cuttings become wedged under the external components. Pipe movement during cementing operations is also limited with conventional designs, since the hangers are set prior to cementing the wells. This can lead to poor cementing practices and poor cementing results, especially at the shoe and the liner top, where cement assists with the hydraulic seal. Additional concerns arise when trying to work or ream the liner to setting depth in deviated holes where cuttings removal can be difficult. Both rotation and pump rates are limited with conventional equipment. Conventional "drill-in" liner hangers are set or released by applying a differential pressure across the hanger or setting tool. Running and rotation speeds are limited due to slip design and the use of conventional packer elements integral to these tools. This limits the ability to effectively clean the hole.