Patent Application
20110147015
The field of this invention is packers or bridge plugs that use a metal-to-metal seal and more particularly seal bore sections inserted in a tubular string in which such packers or bridge plugs are set.
Packers and bridge plugs are barrier devices to isolate zones in a borehole for a variety of purposes. Historically these devices have featured one or more resilient sealing members that were squeezed together longitudinally to increase their diameter to seal off an annular space around the packer or plug. Such devices could be mechanically set with setting tools or could be hydraulically set with a ball dropped on a seat followed by pressuring up the tubing. Typically the set position would be retained with slips that engaged the tubular wall on one or both sides of the sealing element.
While such designs have been used for decades, they have limitations when there are high differential pressures or high service temperatures. The resilient material for the seals generally has an upper temperature limit of about 350 degrees F. To make up for these limitations and limitations on the degree of expansion of the traditional mechanically set compressible elements, new designs have been developed that use a metal to metal seal such as by collapsing a pre-scored tube so that it folds along the scores and extends outwardly. Such a metal to metal seal design is described in U.S. Pat. No. 7,134,506. Other metal seal designs are described in U.S. Pat. Nos. 7,448,445; 7,165,622; 6,962,206 and 5,685,369. Such packers or bridge plugs are also the subject of technical articles such as: Wellbore Isolation Intervention Devices Utilizing a Metal-to-Metal Rather Than an Elastomeric Sealing Methodology Gordon Mackenzie and Garry Garfield, Baker Oil Tools SPE 109791-MS 2007; Recent Metal-To-Metal Sealing Technology for Zonal Isolation Applications Demonstrates Potential for Use in Hostile HPHT Environments Garry Garfield and Gordon Mackenzie, Baker Oil Tools SPE 105854-MS 2007; Metal-to-Metal Sealing Technology: Bridging the Gap Between Conventional and High-Expansion Zonal Isolation Applications SPE Garry Garfield and Gordon Mackenzie, Baker Oil Tools SPE 107107-MS 2007 and Wireline Deployed Metal Sealing Bridge Plug System: Operational Learning Curve and Subsequent Redevelopment I. C. Chapman, SPE, K. S. Ng, SPE, ExxonMobil Development Company; N. M. Nor, SPE, RasGas Company Limited; G. R. J. Mackenzie, SPE, G. L. Garfield, SPE, Baker Oil Tools SPE 113891-MS 2008.
The issue that has developed with metal-to-metal high expansion plugs is when they are set in API tubulars whose inner wall condition can undermine the sealing contact with the element. The tubular can have some degree of out of roundness or simply an uneven surface from external loads that have caused a part of the circumference to dent inwardly. There can be scale added to the inner surface or corrosion that takes away some of the wall surface. Scoring can occur from wireline damage or even a drilling assembly passing through the seal bore. In short, the tubular at the location where the metal seal is to be actuated is not ideal for a seal of the desired level or in some cases any seal at all.
The present invention addresses this issue by placing at strategic locations seal bores that have been machined and polished to required tolerances that when the metal seal is extended into contact with the seal bore, a seal to the required specification is accomplished. The seal bore can have an optional coating and can further be optionally recessed in a pup joint to further protect it until use. The sealing element will merely penetrate the coating to make sealing contact with the seal bore wall. These seal bores can be located by counting a distance from a predetermined number of casing collars for example or other location techniques can be used. An optional possibility is to use landing shoulders or some other internal tubular condition that makes the packer or bridge plug stop at the location where its sealing element will be in the seal bore. Alternatively a radioactive source can be placed in or near the seal bore whose presence can be detected by the packer or bridge plug as it is advanced in the bore.
While seal bores have been in use before, the application has been to insert an object with external ring seals into the seal bore in an interference fit to obtain sealing contact. A few examples of such seal bores are shown in U.S. Pat. Nos. 4,612,985; 4,443,726 and 4,111,435. The present invention associates a metal to metal seal or a non-metallic seal or a non-elastomeric seal with a seal bore with the option of protecting the polished surface having a predetermined diameter so that sealing integrity can be attained in the desired location or locations. Those skilled in the art will further appreciate other aspects of the present invention from the detailed description of the preferred embodiment and the associated drawings while recognizing that the full scope of the invention is to be determined by the appended claims.
One or more pup joints are provided in a tubular string at one or more predetermined locations. The seal bores are recessed to protect them from passing tool until needed as a sealing location for a packer or bridge plug having a metal-to-metal seal that is radially extended into sealing contact with the seal bore surface. The seal surface can be recessed to protect it from passing tools. A coating or sleeve can be fit to the sealing surface that is penetrated by the sealing element of the packer or bridge plug for the metal to metal seal. The presence of the protective sleeve can also enhance the metal to metal seal by abutting the sealing element on opposed sides after the sealing element penetrates through the sleeve.
Referring first to
Those skilled in the art will appreciate that seal bores 24 can be placed between zones based on available well data for where in the future isolation may be needed. By actuating metal to metal packers or bridge plugs 26 so that they engage a seal bore 24 having a surface 18 of a known dimension within narrow tolerances and the requisite surface smoothness or level of polish, the performance of the packer or plug 26 in getting a seal of the required degree will be more likely and the uncertainties of API tubulars that have been in service for a long time and have issues of out of roundness, corrosion, or scale buildup will be eliminated. With the use of a coating or cover 30 that is compatible with well fluids, even long term exposure downhole should not change the dimensional and polish characteristics of the seal bore 24 at its surface 18.
Recessing the surface 18 with respect to ends 20 and 22 will protect surface 18 with or without a coating or sleeve 30. The coating or sleeve or other protective shape 30 can be left in place and penetrated as shown in
The metal to metal packer or plug 24 are of a type known in the art and described in some of the cited art above such as U.S. Pat. No. 7,134,506. However, with the use of seal bores 24 having a surface 18 of a known dimension, prior designs of packers or plugs 26 can be designed to be set in a specific bore dimension as opposed to the current practice where a given packer or plug 26 is designed for a range of diameters to handle for example different wall thicknesses for a given size of tubular, with the seal nearer the larger dimension of the range seeing a smaller retained force to hold the metal to metal seal. Instead, with a known seal bore 24 the plug or packer can be optimized to a specific sealing dimension whose integrity will remain at the time the packer or plug 26 is finally run in for zonal isolation.
The above description is illustrative of the preferred embodiment and many modifications may be made by those skilled in the art without departing from the invention whose scope is to be determined from the literal and equivalent scope of the claims below.
