Patent Application
20130312981
The field of this invention is tieback connections above a liner top packer and hanger and more particularly where the tieback extension travels over the liner hanger stem for sealing to the outside of the stem.
Conventional liner hangers are tied back via a larger extension with a seal bore at the top of the preinstalled liner hanger and a smaller tieback stem with outside diameter seals at the bottom of the upper tieback string. In recent years there has been a challenge with tighter tolerance liners. As the outside diameter of the liner to the inside diameter of the casing gap closes, the room for an extension closes. The result is low extension pressure capability due to thin sleeves and reduced cementing capabilities due to high pressures required to circulate cement through the skinny extension outside diameter to casing inside diameter annulus.
This concept is illustrated in
This invention turns the conventional tieback connection upside down. The tieback receptacle on the top of the liner hanger is a smaller tube for sealing on the outside diameter with dimensions more or less equivalent to the liner pipe. The tieback shoe that is run on the bottom of the tieback string has dimensions that are more or less similar to the extensions of before. A couple of additional improvements are made. The first improvement is the ability to expand the shoe over the tieback receptacle creating a metal to metal seal and sandwiching steel from the pass through inside diameter all the way to the previous casing (in which the liner hanger is set) outside diameter for improved pressure capacity. The second improvement is making the top of the tieback receptacle have 2 different diameters or 2 steps which allow for improved pressure capacity. The smaller diameter at the top allows for a thicker outer section to carry internal pressure before disengaging the seal. The larger diameter below allows for more collapse capacity on the internal piece.
The following art is generally related to tiebacks and expansion: U.S. Pat. No. 7,195,073 Expandable tieback; U.S. Pat. No. 5,259,459 Subsea wellhead tieback connector; No. 5,299,642 Subsea wellhead tieback connector; U.S. Pat. No. 4,293,146 VMP Casing tieback; U.S. Pat. No. 4,519,633 Subsea well casing tieback connector; US2009/0277645 Internal Tieback for Subsea Well; U.S. Pat. No. 7,896,081 Internal tieback for subsea well; US2011/0155382 Internal Tieback for Subsea Well; U.S. Pat. No. 8,127,853 Internal tieback for subsea well; US2003/0145996 Externally actuated subsea wellhead tieback connector; U.S. Pat. No. 6,666,272 Externally actuated subsea wellhead tieback connector; U.S. Pat. No. 5,775,427 Internally latched subsea wellhead tieback connector; U.S. Pat. No. 5,279,369 Tieback receptacle with upward and downward facing funnel sections; U.S. Pat. No. 4,653,589 Mudline casing hanger tieback adaptor with adjustable load ring.
US 2010/0314130 is generally related to tubular expansion with a swage using internal supports to enhance the amount of expansion. US 2010/0314130 A1 by Douglas Durst of Enventure shows mid-string packing elements including a spacer that. US 2010/0089591 A1 by Gordon Thomson shows an under-gage shape hanger in FIG. 19.
Those skilled in the art will better appreciate additional aspects of the invention from a review of the detailed description and the associated drawings while recognizing that the full scope of the invention is to be determined by the appended claims.
A tieback extension is configured with an exterior cone and externals seals with a clearance space to accept a tieback stem that will wash over the extension and expand when landed and advanced over the cone. The lower end of the stem is tapered so that the thickness opposing the upper seal adds to burst and collapse resistance while the tapered lower end allows a thicker extension to be used in the area of the lower seal. The expansion can be accomplished with setting down weight which can also enhance the set of the liner hanger below. Minimal expansion in the order of 3% or less is needed. Exterior slots create cement flow passages and a no-go for the stem to prevent damage to the box further below. The extension is hardened and the sleeve can be coated to facilitate expansion. A metal to metal seal is created at the cone that is straddled by the exterior seals on the extension.
An interior profile 58 allows a known running tool to deliver the liner with the extension 40 as well as hanger 60 and packer 62.
In an example of the method the wellbore is drilled to 14.5 inches in diameter followed by scraping the 16 inch casing above. The liner is run to the point where the hanger 60 and the packer 62 are properly positioned near the lower end of the 16 inch casing. The hanger 60 is set and the running tool released followed by cementing. The packer 62 is then set and the running string is pulled out of the hole. The shoe 30 is secured to the lower end of the tieback string and the shoe 30 is brought down on the conical surface 38 of the receptacle 40 and is advanced to a point short of no-go 52 at a point preferably located near the wellhead, not shown. Optionally the tieback string can also be cemented.
This invention turns the conventional tieback connection upside down. The tieback receptacle on the top of the liner hanger is a smaller tube for sealing on the outside diameter with dimensions more or less equivalent to the liner pipe. The tieback shoe that is run on the bottom of the tieback string has dimensions that are more or less similar to the extensions of before. A couple of additional improvements are made. The first improvement is the ability to expand the shoe over the tieback receptacle creating a metal to metal seal and sandwiching steel from the pass through inside diameter all the way to the previous casing (in which the liner hanger is set) outside diameter for improved pressure capacity. The second improvement is making the top of the tieback receptacle have 2 different diameters or 2 steps which allow for improved pressure capacity. The smaller diameter at the top allows for a thicker outer section to carry internal pressure before disengaging the seal. The larger diameter below allows for more collapse capacity on the internal piece. Another item is an expandable liner hanger packer that has the same outside diameter as the liner string before expansion. After expansion the liner hanger packer has the same inside diameter as the liner string. This liner packer design would be preferred for pressure capability, run in clearance, cementing and equivalent circulating density of the cement.
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:
