DELIVERY METHOD AND COMPOSITIONS

This invention relates to methods of conveying or delivering sealing elements to a target area in a vessel, and particularly but not exclusively to methods of conveying or delivering sealing elements to the required location in vessels, valves, pipes or ducts. The present invention also relates to sealing compositions and in particular but not exclusively, the present invention relates to sealing compositions which are adapted to reduce or stop seepage through a leak in a vessel, valve, pipe or duct. More particularly, the present invention relates to sealing compositions which are particularly suitable for sealing leaks in vessels, pipes, valves or ducting used to transport hydrocarbons, water, control and process fluids.

The present Applicant has for many years been developing techniques for sealing and stemming leaks from ducts carrying, for example, hydrocarbons, water, control and process fluids.

The Applicant's patent application WO-A-01/86191 discloses a plurality of elements, each in the form of a membrane, which are introduced into a duct to be carried along the duct by the flow of the fluid therein. At the locality of the leak, at least one of the sealing elements is captured by a pressure differential associated with the leak and is thereby drawn to and held in position at the leak for stemming or sealing it.

The Applicant's patent application WO-A-03/93713 discloses introducing a plurality of sealing elements into a duct which have an effective size less than the effective size of the leak. Even though the pressure differential attributable to the leak is relatively small, the sealing elements are drawn to, move over and build up with the duct at the leak and reduce seepage therefrom.

As discussed in these two applications, through the techniques disclosed, it is possible to reduce or eradicate the problems associated with leakage from ducts which are inaccessible or only accessible with considerable difficulty.

WO 2009/112863 discloses a further method allowing sealing of a leak.

However, a problem remains with the techniques disclosed in the aforesaid two applications in that it can be difficult to convey the sealing element(s) to the leak site within the duct in sufficient numbers to ensure that an effective seal is formed. In particular this can be due to the density of the elements(s) particularly in comparison to the fluids flowing in the ducts which act to transport the element(s) to the required location.

Additionally, large diameter pipes or ducts may require a significant volume of sealing elements to be deployed in order to ensure that a sufficient number of elements reach the leak site. Controlling the delivery of the sealing elements to the leak site would greatly enhance the cost effectiveness of the sealing operation and minimise any risk to infrastructure.

A further problem with the previously proposed techniques is ensuring that once a sufficient number of sealing elements are conveyed to the leak site, they are prevented from flowing or falling away from the required location before they can become entrained within the leak. Solving this problem further enhances the cost effectiveness of the sealing operation as it further minimises the amount of the sealing composition required to effect a seal in the duct.

When a leak forms in the duct, a pressure differential is created between the interior and exterior of the duct. Fluid flow created by the pressure differential carries the sealing elements to the site of the leak. The target area for the sealing elements is an area of the duct interior surface or wall adjacent to or surrounding the leak, including the edges of the duct wall which define the aperture through which fluids can be lost. In the following description this target area will be referred to as the leak site. In some cases the pressure differential may be insufficient to draw the sealing elements towards the site and entrain them within the leak site. The longer an element can be held in the vicinity of the leak site, the more likely the element will be entrained within the leak site and the leak will be plugged.

Moreover, in the hydrocarbon industry there are particular safety constraints which often require a double seal barrier between the hydrocarbon carrying duct and the external environment. If there is then a small leak, even though the volume leakage of hydrocarbon due to seepage may be relatively small, i.e. a trickle leakage flow, it is nevertheless important that such leaks are completely sealed for health and safety reasons or for environmental reasons. In addition, leak development and leak appearance is a dynamic process and the techniques disclosed in the aforesaid two applications do not provide a way of sealing such leaks.

The present invention seeks to provide a method for overcoming the aforementioned disadvantages of the prior art and provide an improved method of delivering sealing elements to the leak site thereby reducing or completely sealing the leak.

Furthermore, the present invention seeks to provide a method of delivering a concentrated quantity of sealing elements to the leak site for use in reducing or completely sealing the leak.

Additionally, the present invention also seeks to provide sealing compositions which address the above mentioned problems and overcome or at least mitigate these problems.

According to one aspect of the present invention there is provided a method of delivering a concentrated quantity of sealing elements to a leak site as described in claim 1.

Conveniently the passage of material through the vessel is controlled to target the delivery of the sealing elements to the leak site.

Advantageously the body of material is drawn through the leak and pulls the sealing element(s) into the leak to effect a seal.

The passage of the body of material through the vessel is controlled by varying the density of the body of material and/or the density of the sealing elements to ensure that the body of material flows through the vessel at the optimum position to be drawn to the leak site.

The sealing element is/are provided within the body of material and are transported within the body of material to the leak site.

The body of material will be contained within a frangible membrane and the method may further comprise rupturing the membrane upon impact with the leak site to deliver the sealing elements directly to the leak site.

In one embodiment, the vessel is a valve, pipe, o-ring or a duct, although as would be appreciated by the person skilled in the art, the methods of the present invention may be used to seal any leak, such as but not limited to remediation of seal failure, tubing joints, pig launcher/receiver, hydrants, heat exchangers and glands.

According to a further aspect of the present invention there is provided a sealing composition according to claim 5 comprising a flexible body of material and at least one sealing element, the body of material being adapted to transport the sealing element(s) in a controllable and targeted manner to a leak site within a vessel and to constrain the sealing element(s) at the leak site.

Preferably the body of material and at least one sealing element form a slug which is transportable through the vessel by fluids flowing within the vessel.

Conveniently the body of material comprises a gel. Conveniently, the body of material comprises a viscosifier, most preferably a non-Newtonian viscosifer, and may comprise Xanthium gum or guar gum.

Advantageously the body of material may comprise Xanthium gum or guar gum crosslinked with agents including but not limited to borax or sodium borate.

The sealing element(s) is/are elastomeric.

Preferably the density of the body of material and or the density of the sealing elements is selected depending upon the density of the fluids flowing in the vessel. For example, the density may be selected such that the sealing composition floats within the fluid flowing in the vessel. Alternatively the density may be selected such that the sealing composition travels along the vessel at a submerged position within the fluid flow.

The sealing composition comprises a membrane, the membrane surrounding the body of material. In some embodiment, the membrane may be relatively thin in comparison to the size of the body of material. In some embodiments may be frangible.

The membrane may comprise an elastomeric material such as but not limited to latex, natural rubber, NBR, HNBR and FKM.

The membrane is adapted to rupture upon impact with the leak site to ensure that a concentration of sealing elements are delivered to the leak site.

Alternatively, the body of material and sealing elements may be deployed in a sealed container, for example but not limited to a pipeline pig or a wireline tool.

Conveniently as the container approaches the leak site, or alternatively once it reaches the leak site, the body of material and sealing elements may be forced from the container onto the leak site.

Methods according to the present invention may include sealing the container in position within the vessel at or adjacent the leak site prior to forcing the body of material and the sealing elements from the container.

The sealing elements may be uniformly or randomly distributed through the body of material or only provided at selected locations.

In some embodiments the body of material may be adapted to degrade over time such that the body will eventually dissolve within the fluids flowing in the vessel. Additionally or alternatively the body of material may be adapted to undergo a change or degrade for example based upon the temperature within the vessel, a change in temperature within the vessel or within the fluid flowing in the vessel, a reaction to an agent such as a chemical agent deployed into the vessel or in response to light stimulation, such as by ultraviolet light.

Preferably the body of material has a higher viscosity than the fluid(s) flowing within the vessel in order to assist in retaining the sealing elements within the body of material. Alternatively, the body of material may comprise or be formed of a material similar or identical to the fluids flowing in the vessel depending upon the concentration of sealing elements deployed with the body of material.

Advantageously a surfactant may be added to the body of material to promote the boding between the body and the sealing element(s).

Preferably, the sealing composition comprises a range of different sized sealing elements. The sizes of the individual sealing elements may be selected depending upon the size of the leak to be sealed.

Conveniently, the sealing elements may comprise an elastomeric material, silicone rubbers, polyurethane rubbers, natural rubbers, nitrile rubbers and/or a flouropolymer elastomer.

The sealing elements may be formed into a shape corresponding to any one of planar-oblong, cubes, spheres, pyramids, octahedrons, tetrahedrons, thistle-seed shaped, filament shaped or of an irregular shape.

There may be provided a sealing composition comprising at least one sealing element, said sealing element comprising a trace element.

Advantageously the trace element is a dye. Alternatively the trace element is a transmitter which sends out a signal which can be monitored by a suitable receiver to determine the location of the sealing element within a vessel.

In one embodiment the sealing composition may comprise sealing elements with different characteristics, each of which has an associated different trace element. For example, different sealing elements of different size or density may have a different coloured dye applied thereto or a different transmitter incorporated therewith such that by analysing the colour of the sealing elements escaping from the vessel or the location of the sealing elements within the vessel, information as to the characteristics of the leak site such as size or position may be obtained.

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings, in which:-

• Figure 1, 3, 4 illustrate, schematically, a sealing composition not covered by the present invention;
• Figure 2 illustrates, schematically a sealing composition according to the present invention in which a membrane is formed around the outer surface of a body of material;

An embodiment of the present invention is shown in Figure 2. In this embodiment, a thin membrane 5 surrounds the body of material to assist in delivering the concentration of sealing elements to the leak site.

The membrane may comprise an elastomeric material such as latex, natural rubber, NBR, HNBR and FKH or combinations thereof and may be provided in the form of a bag or balloon within which the body of material is contained. Alternatively, the membrane may be formed as a coating around the body of material.

The membrane 5 in this embodiment may be frangible and may be adapted to rupture upon contact with the leak site so that the contents of the membrane are only released once the body of material has reached the required location thereby ensuring that the maximum concentration of sealing elements are available at the leak site for sealing the site.

In this embodiment the membrane may be formed around the body of material of material by a known process.

Similarly as with the first embodiment, in this embodiment the density of the body of material 4 and/or the sealing elements 3 and/or the combination of the two may be selected in response to the nature of the fluids flowing in the duct and/or the position of the leak site within the duct.

As will be understood by the person skilled in the art, the examples illustrated show applications of the invention only for the purposes of illustration. In practice the invention may be applied to many different configurations, the detailed embodiments being straightforward for those skilled in the art to implement. Furthermore, any of the examples provided above for the body of material may be used in any of the embodiments of the invention as described.

For example the invention is equally applicable to many types of valve systems, and any kind of pipework such as water-carrying pipework.

As used herein, the terms leak site and defect are used interchangeably and are taken to mean any site at which unwanted seepage or leaking may occur.

The body of material of any of the embodiments described may also comprise an inhibiting agent to prevent enlargement of the leak such as by corrosion, once sealed.

Additionally or alternatively, any of the examples and embodiments described above may be modified to comprise a surfactant to promote the bond between the sealing element(s) and the body of material. Examples of surfactants include detergents such as for example sold under the trade mark DRIL-KLEEN II produced by MISwaco which is a detergent based surfactant with a specific gravity of 1.10, a PH (1 % soliution) of 9.3-9.5, solubility in water at 20°C and a flashpoint > 93°C which may be applied to the sealing elements prior to their inclusion with water based gels. Domestic detergents such as washing up liquid may also be used.

It will be understood by the person skilled in the art that the body of material described above may comprise different materials each having a different density and the sealing elements may include different sized or shaped individual elements with different densities such that the order of arrival of sealing elements at the leak site in quick succession can be controlled.

In embodiments in which larger or heavier sealing elements are used, for example sealing elements greater than 20mm in size or of greater density than 1200 kg/m³., the amount of viscosified fluid or non-Newtonian viscosifiers present in the body of material may be increased.

By modifying the density of the body of material, the flow rate of the sealing composition through the vessel may be altered. For example, the density may be set such that the sealing composition is pumped into a vessel with sufficient force to push the sealing composition through the fluid flowing in the vessel but once pumping is stopped, the buoyancy of the sealing composition may be such that the composition returns to the top of the vessel.

Furthermore, the body of material may be substrate phobic and/ or sealing element material phylic and/or vessel wall phylic. This will assist in keeping the body of material together as it travels through the vessel and increase the likelihood of the body of material to travel along the wall of the vessel which will give maximum probability for entrainment into leaks all around the vessel wall.

Additionally or alternatively, the body of material may be compressible to allow a mid deployment tuning of the density of the sealing composition such as to make sure it passes over a shaft in the vessel and drops to the bottom to seal a leak at that location.

Additionally or alternatively, the body of material may change state with pressure or temperature. This may assist in keeping the body of material and sealing elements together and protect the sealing composition in case of impacts such as when it encounters a bend or constriction in the vessel. Once the body of material reaches the leak site it may undergo a transformation such that a hard dome forms on the outer surface of the body of material and the inner portion of the body of material remains relatively soft.

If the body of material is highly cohesive then the body of material could go through orifices which are bigger than the sealing elements but smaller than the body of material.

As would be appreciated by the person skilled in the art, the methods and compositions of the present invention may be used to seal any leak or defect. In particular, but not exclusively, the methods and compositions of the present invention may be used to seal a leak or defect in a valve, pipe line, seal, vessel, duct, tubing and tubing joints e.g. pipe dope, and o-rings which have failed, remediation of a seal failure, a pig launcher/receiver, a hydrant, a heat exchanger or a gland.

The methods and sealing compositions of the present invention are suitable for use in a well bore. For instance, the methods and sealing mixtures of the present invention may be used to reduce fluid losses during drilling and closing water production zones.

When used to reduce drilling losses, the slug may be introduced through a drill pipe. Preferably, a range of different sized sealing elements are included to enable sealing of variable fractures and thief zones. After the fracture or defect has been sealed, hydrostatic forces exerted by the fluid filling the well can act to keep the sealing mixture in place. In this application of the methods and sealing mixtures of the present invention only a temporary seal is required as once drilling progresses, a casing may be used to seal off the fracture or defect. However, as would be appreciated by the person skilled in the art, the methods and sealing mixtures of the present invention may be used in any application to form a permanent seal if desired.

When used during water shut off procedures, the sealing compositions may include sealing elements comprised of an elastomeric material which swells in water and/or the sealing mixture may include sealing elements which dissolve in oil but are inert (i.e. do not dissolve) in water. The sealing composition of the present invention is introduced to the well bore and carried to the water shut off point or pore throat with pressure of the fluids forcing the sealing elements into the formation or pore throat.

The methods and sealing compositions of the present invention may also be used to seal leaks in an annulus or leaks between concentric annuli, e.g. A to B to C annulus leaks, or leaks in a pipe in pipe situation, leaks in sand control screens, leaks in control lines during completion of a well, and leaks in subsurface safety valves (SSSVs) and surface-controlled subsurface safety valves (SCSSVs).

The methods and sealing compositions of the present invention are also suitable for use within the water and gas industries, both in a commercial and a municipal setting. For instance, the methods and sealing compositions of the present invention could be used to seal leaks present in any part of the infrastructure associated with wastewater capture, transportation, storage and treatment, raw water capture, transportation, delivery and storage and potable water treatment, storage, capture, transportation and delivery, and brackish and desalinated water capture, treatment, transportation, delivery and storage, portable water treatment, capture, storage and transportation.

Additionally, the methods and sealing compositions of the present invention are suitable for use in sealing leaks in or at any point within the infrastructure associated with irrigation systems and the treatment, storage, capture and transportation and delivery of fluids through irrigation systems.

Furthermore, the methods and sealing compositions of the present invention are suitable for use in sealing leaks within delivery, storage, treatment and capture of gas, e.g. natural gas. The methods and sealing compositions of the present invention may also be used seal leaks in carbon capture and storage systems.

It is also to be appreciated that the methods and sealing compositions of the present invention are also suitable for use in sealing or mitigating leaks in wells, umbilicals, pipework caissons, storage fill lines, flexible pipes, tubing joints and control lines from horizontal to the vertical, downhole lost circulation, drilling losing and non-productive zones, trunk mains, distribution mains, supply pipes, joints, reservoirs, fire systems, washing systems, industrial water pipes, industrial supply pipes, all of which are considered to fall within the term "vessel".

Moreover, the delivery methods and compositions of the present invention may be used during assembly of a tool, e.g. a completion tool, to lubricate any seals or valves within the tool, thereby providing a reservoir of sealing composition within the assembled tool. Thus, if a leak occurs in the tool at the site of a seal or a valve, the sealing composition of the present invention is already in place to seal the leak.

The body of material may assist in sealing the leak in the vessel. For example, the body of material may exert a force onto the sealing elements to ensure that they enter the leak site or deform to seal the leak and also to resist micro cracks forming between the sealing elements.

The body of sealing material may, in some embodiments, change state upon contact with the leak site. For example, the body of material may strain harden or may harden through shear forces applied to the body on contact with the edges of the vessel wall surrounding the leak. In these embodiments the body of material may assist in bonding a group of sealing elements into the leak in the vessel wall.

In some embodiments the body of material and sealing elements may be deployed into the vessel in a sealed container, for example but not limited to a pipeline pig or a wireline tool. As the container approaches the leak site, or alternatively once it reaches the leak site, the body of material and sealing elements may be forced from the container onto the leak site by means generally available to the skilled person. Methods according to the present invention may include sealing the container in position within the vessel at or adjacent the leak site prior to forcing the body of material and the sealing elements from the container.

In a further embodiment, the body of material and the sealing elements of any of the embodiments described above may be injected into the vessel through a coiled tubing string which is directed at the leak site. In such an embodiment a seal may be provided between the coiled tubing and the interior wall of the vessel to hold the coiled tubing in the required position.