GB2433540A

GB2433540A - Brush seal for grouting annuli

Info

Publication number: GB2433540A
Application number: GB0526101A
Authority: GB
Inventors: Martin Hardy; Seamark Systems Ltd
Original assignee: Individual
Current assignee: Individual
Priority date: 2005-12-22
Filing date: 2005-12-22
Publication date: 2007-06-27
Also published as: GB0526101D0

Abstract

A grouting method to grout the annular space between two concentrically placed steel tubes or members. In addition to a primary seal 22 or 23 provided to support the grouted column there is provided a secondary contingency brush seal 27 to support the grout if the primary seal fails. The method is particularly suitable for grouting the annuli between a offshore platform leg or pile sleeve 20 and a foundation pile 21 driven there through.

Description

Contingency Brush Seal for Grouting Annuli

Background

This invention provides for an improved grouting method for grouting the annular space between two concentrically placed steel tubes or members. In particular the invention is suitable for the annuli between a offshore platforms leg or pile sleeve and foundation pile driven there through. In addition to the primary seal provided to support the grouted column the invention provides for a secondary contingency method to support the grout if the primary seal fails.

With account of standard offshore practice the primary seal is normally a inflatable rubber packer or a wiper manufactured is such a way that it will support the grout placed above it or the grout is placed by pressure balancing the grout on the available head of water.

However, should such a grout column not be supported the grout will run out of the bottom of the annular space into the surrounding water. Also, if some way of sealing the annulus cannot be found so that the grout column can be placed in the annulus and allowed to harden, the annulus will remain empty and thus affect the stability of the offshore platform.

Previously, when trying to seal the annulus a wide variety of materials have been used.

Typically fast setting cements to form a grout plug, lost circulation materials used in well drilling have been tried. If the bottom of the annulus is accessible to divers or Remote Controlled Vehicles (ROVs) they have been used to seal or try to seal the annulus by filling it from the bottom with sacks, rags, rubber materials or by placing sand bags around the base of the annulus.

However, the use of fast setting or accelerated cements can plug up the flow lines, lost circulation materials have not proven satisfactory in bridging large openings and the use of divers and ROVs are time consuming, expensive and may not have access in many applications.

Statement of Invention

The invention is directed to improve the grouting method by providing an economic contingency method of sealing the annulus if the primary sealing method has failed. This is achieved by placing a brush below the primary seal. This provides a robust partial bridge of the annulus and allows a standard grout to be used to form a small internal grout plug that after setting can be used to support the required final column of grout.

Drawings To assist in understanding this invention the following drawings have been provided.

FIG. 1 Shows a typical offshore platform, illustrating both jacket legs and pile sleeves having foundation piles driven there through.

FIG. 2 Shows the invention in cross-section in a leg or sleeve with a driven pile.

FIG.3 Shows a cross section of the invention in use.

Referring to FIG.1, an offshore platform 10 having ajacket portion 11,jacket leg 12, pile sleeve 13 and piles 14 is resting on the bed 16, of a body of water. Annulus seals 15 are installed on the bottom of each leg 12 or pile sleeve 32. Piles 14, are shown as being driven to some depth below the jacket through a jacket leg 12 and pile sleeve 13.

Referring to FIG. 2, the seal assembly 15 from FIG. I which details the invention is shown installed on an annular support member of the platform 10, such as a jacket leg 12, although it may be a pile sleeve 13, having a pile 14 driven there through.

The seal assembly consists of the leg or sleeve 20 with the driven pile 21 and shows either a pile wiper seal 22 or a inflated pile packer 23 as alternative primary annulus seals.

Primary grout fill line 24, contingency grout fill line 25, grout overflow 26 and the contingency grout brush 27 that forms the invention are also illustrated.

The brush seal 27 consists of a shaped or flexible back with a staggered pattern tuft with a tuft length to spacing ratio of between 10 and 20 to 1. Materials of the backing and tuft are not implicit in the invention as it is the relative surface area that a brush provides that allows the required operation of trapping the grouting material during curing. Materials of the backing and tuft will be suitable for operation underwater.

The invention allows grout to be trapped in the matrix of the brush bristles and when allowed to set will bridge the annulus forming a plug to allow grouting operations to be undertaken to successfully complete filling the pile annulus.

The improved grouting method utilising the invention is active if the primary seal fails.

Referring to FIG.3, by way of an example only, shows a pile sleeve incorporating the invention and detailing the contingency grout brush 30, primary seal failure 32, Preliminary grout plug 31 and the final grout column 33.

If the primary seal failure is known prior to grouting operations the following procedure will be undertaken.

A. Pump a calculated volume of grout into the annulus via contingency grout fill line 25 to allow filling of the contingency brush (3 x nominal volume of brush + allowance for pipe line losses).

B. Flush water through the contingency grout fill line 25 to clear line. Flushing will continue until clear water flow is observed via the the grout overflow 26.

C. The contingency brush plug is allow to set to form a solid material.

D. A grout plug is formed by pumping grout via the contingency grout fill line 25 until grout is seen overflowing from the grout overflow 25.

E. The grout plug is allowed to set and form a solid.

F. Standard grouting operations can then be completed via the primary grout fill line 24.

If the primary seal failure occurs during grouting operations the following procedure will be undertaken A. Failure of the primary seal will be noted by observing grout flow from the bottom of the annulus and br unexpected grout flow from the grout overflow 25.

Allow grout flow to stop and then flush water via the primary grout fill line 24 keeping it available for further grouting operations until the grout is allow to set and form a solid plug.

C. Standard grouting operations can then be completed via the primary grout fill line 24.

It will be noted to those skilled in the art that such an improved grouting method and grouting arrangement may be modified to be used on a wide variety of marine structures in various locations thereon where it is desired to seal an annular space and grout the area located there above, such modifications being within the scope of the present invention.

Claims

Claims Having described our invention, we claim: 1. A method to

successfully grout a annular spaced formed by two concentrically placed steel tubes, typical example of which is a leg or pile sleeve with a driven foundation pile on a offshore platform, if the primary bottom seal fails. The method consists of positioning a contingency brush seal below the primary seal that will allow bridging of the annulus if required to form a grout plug.

2. The method of grouting of claim I wherein the annulus is formed by a caisson and repair clamp.

3. The method of grouting of claim 1 wherein the annulus is formed by a jacket member and repair clamp.

4. The use of a brush seal to form a seal with grout in an annular space.