GB2599128A

GB2599128A - Apparatus and Method

Info

Publication number: GB2599128A
Application number: GB2015147.8A
Authority: GB
Inventors: Barnes John; Chhanabhai Patel Bhikhubhai
Original assignee: John Crane UK Ltd
Current assignee: John Crane UK Ltd
Priority date: 2020-09-24
Filing date: 2020-09-24
Publication date: 2022-03-30
Also published as: WO2022064167A1; GB202015147D0

Abstract

A washpipe cartridge for carrying drilling mud in a top drive of a drilling assembly, the washpipe cartridge comprising: a housing 104 adapted to fit between a stationary goose neck pipe of the top drive and a drill string, wherein the drill string is rotatable about a rotational axis, the housing comprising: a sleeve 102; and, a housing 104; wherein the sleeve is configured to provide the drilling mud to the drill string; and, wherein the housing is configured to receive drilling mud from the goose neck pipe. Disposed between the sleeve and the housing is a first seal 106, a second seal 108 and a first gallery 112 between the first seal and the second seal, and a second gallery 114 and wherein the cartridge further comprises: a first gallery inlet 116 for providing a first supply of barrier fluid to the first gallery; a second gallery inlet 118 for providing a second supply of barrier fluid to the second seal, wherein the second gallery inlet is separated from the first gallery by the second seal.

Description

Apparatus and Method

Field of invention

The present invention relates to the field of contacting wet seals, in particular, the 5 present invention relates to the field of contacting wet seals at very high pressures.

Background

A top drive assembly comprises: a goose neck pipe; a washpipe cartridge; and a drill string. The goose neck pipe is configured to provide drilling mud to a drill string via the washpipe. The drill string is configured to receive drilling mud from the goose neck pipe via the washpipe cartridge. The drill string is configured to rotate relative to the goose neck pipe. The washpipe cartridge comprises seals. The washpipe provides a seal between the goose neck pipe (which, in use, is stationary) and the drill string (which, in use, rotates).

Drilling mud may comprise chemical compositions which are abrasive and/or corrosive to the seals. Contact between seals in the washpipe and drilling mud may damage the seals (e.g. through abrasion and/or corrosion). Therefore, it is undesirable for drilling mud to contact seals in the washpipe.

Washpipe cartridges may leak drilling mud Drilling mud which leaks from a washpipe cartridge must be replaced. Replacing, drill mud may incur undesirable costs for a top drive operator. Therefore, it is undesirable for washpipe cartridges to leak drilling mud.

Summary

Aspects of the invention are set out in the independent claims and optional features are set out in the dependent claims. Aspects of the disclosure may be provided in conjunction with each other, and features of one aspect may be applied to other aspects.

A washpipe cartridge for carrying drilling mud in a top drive of a drilling assembly, the washpipe cartridge comprising: -2 -a housing adapted to fit between a stationary goose neck pipe of the top drive and a drill string, wherein the drill string is rotatable about a rotational axis, the housing comprising: a sleeve; and, a housing; wherein the sleeve is configured to provide the drilling mud to the drill string; and, wherein the housing is configured to receive drilling mud from the goose neck pipe; wherein disposed between the sleeve and the housing is a first seal, a second seal and a first gallery between the first seal and the second seal, and wherein the cartridge further comprises: a first gallery inlet for providing a first supply of barrier fluid to the first gallery; a second gallery inlet for providing a second supply of barrier fluid to the second seal, wherein the second gallery inlet is separated from the first gallery by the second seal.

The first seal and the second seal may comprise mechanical seals.

The first gallery may be configured to receive a first supply of barrier fluid via the first gallery inlet. The second gallery may be configured to receive a second supply of barrier 20 fluid via the second gallery inlet.

When the first supply of barrier fluid is provided to the first gallery and the second supply of barrier fluid is provided to the second gallery, drilling mud may be prevented from contacting any of the seals of the washpipe cartridge (e.g. the first seal, the second seal, and (if included) a third seal). Advantageously, corrosion and/or abrasion of components of the seals due to contact with drilling mud can be reduced or avoided. Accordingly, the expected useful lifetime of the seals (e.g. the expected useful lifetime of components of the seal) may be increased in comparison to seals in washpipe cartridges which may permit contact between the seal and drilling mud.

Increasing the expected useful lifetime of seals in the washpipe cartridge may increase the expected useful lifetime of the washpipe cartridge as a whole in comparison to other washpipe cartridges. When the seals in a washpipe assembly wear out, the washpipe -3 -must be replaced to prevent leakage of the drilling mud from the washpipe.

Increasing the expected useful lifetime of the washpipe cartridge may reduce the frequency at which the washpipe cartridge must be replaced in comparison to the 5 frequency at which other washpipe cartridges must be replaced. Reducing the frequency at which the washpipe cartridge must be replaced may reduce the total top drive downtime. Reducing the frequency at which the washpipe cartridge must be replaced may reduce the replacement costs associated with replacing a washpipe cartridge. Accordingly, using a washpipe cartridge provided by the present disclosure may reduce 10 the operational costs of an end user may be reduced.

A washpipe cartridge for carrying drilling fluid in a top drive of a drilling assembly, the washpipe cartridge comprising: a housing adapted to fit between a stationary goose neck pipe of the top drive and 15 a drill string, wherein the drill string is rotatable about a rotational axis, the housing comprising: a sleeve; and, a housing; wherein the housing is configured to provide the drilling mud to the drill string; and, 20 wherein the sleeve is configured to receive drilling mud from the goose neck pipe; wherein disposed between the sleeve and the housing is a first mechanical seal and a second mechanical seal.

The washpipe cartridge may comprise: a first gallery disposed between the first 25 mechanical seal and the second mechanical seal; and, first gallery inlet for providing a first supply of barrier fluid to the first gallery.

In some uses, washpipe cartridges may be configured to receive drilling mud, wherein the drilling mud has a pressure of up to 520 bar. Washpipe cartridges may be configured to provide a seal against high pressure drilling mud (e.g. pressures of 520 bar). In other words, the washpipe cartridges are configured to provide a high sealing pressure (e.g. pressures of at least 520 bar). -4 -

This may be better than systems which comprise a single mechanical seal or a series of lip seals (e.g. polymer lip seals). Due to the high sealing pressure of the washpipe cartridge and/or sealing friction between the seals and the drilling mud, the lip seals of the these washpipe cartridges tend to fail after a relatively short period of time. The lip seals may fail sequentially. For example, if a washpipe comprises three lip seals: a first lip seal, which in use, is closest of the lip seals to a goose neck pipe; a second lip seal; and, a third lip seal, which in use, is furthest of the lip seals from the goose neck pipe. From the time at which use of the washpipe cartridge begins, the first lip seal will fail before the second and third seals fail and the second lip seal will fail before the third lip seal fails. Once all of the lip seals have failed, the washpipe cartridge will allow drilling mud to leak from the washpipe cartridge. When the washpipe cartridge allows drilling mud to leak from the washpipe cartridge, the washpipe cartridge should be replaced. This may be better than systems which comprise a single mechanical seal and a series of five lip seals and may have an expected useful lifetime of 100 hours of continuous use of the washpipe.

The washpipe cartridge provided by the present disclosure comprises more than one mechanical seal. The washpipe cartridge of the present disclosure may not comprise a lip seal.

Advantageously, providing more than one mechanical seal may allow lip seals to be dispensed with thereby avoiding the disadvantages which come with using washpipe cartridges which comprise lip seals e.g. the short expected useful lifetime of around 100 hours of continuous use.

Advantageously, corrosion and/or abrasion of components of the seals due to contact with drilling mud can be reduced or avoided. Accordingly, the expected useful lifetime of the seals (e.g. the components of the seal) may be increased in comparison to seals in other washpipe cartridges which may permit contact between the seal and drilling mud.

Increasing the expected useful lifetime of seals in the washpipe cartridge may increase the expected useful lifetime of the washpipe cartridge as a whole in comparison to other washpipe cartridges. -5 -

Increasing the expected useful lifetime of the washpipe cartridge may reduce the frequency at which the washpipe cartridge must be replaced in comparison to other washpipe cartridges. Reducing the frequency at which the washpipe cartridge must be replaced may reduce the total top drive downtime e.g. time when drilling is suspended. Reducing the frequency at which the washpipe cartridge must be replaced may reduce the replacement costs associated with replacing a washpipe cartridge. Accordingly, using a washpipe cartridge provided by the present disclosure may reduce the operational costs of an end user.

The washpipe cartridge may comprise: a first gallery disposed between the first mechanical seal and the second mechanical seal; and, first gallery inlet for providing a first supply of barrier fluid to the first gallery.

The washpipe cartridge may comprise: a second gallery inlet for providing a second supply of barrier fluid to the second mechanical seal, wherein the second gallery inlet is separated from the first gallery by the second mechanical seal.

The housing may comprise a goose neck pipe connecting part wherein the connecting 20 part is configured to provide a coupling between the goose neck and the washpipe cartridge, wherein the first mechanical seal is disposed between the sleeve and the connecting part.

The second gallery may be disposed between the second mechanical seal and a third 25 mechanical seal.

A third mechanical seal reduces the magnitude of sealing pressure which must be provided by each seal. For example, if two mechanical seals are provided which are required to provide a sealing pressure of Pseal, the minimum pressure to be sealed by 30 each of the two mechanical seals may be P sea1/2. Whereas, if three mechanical seals are provided which are required to provide the same sealing pressure of P seal, the minimum pressure to be sealed by each of the three mechanical seals may be P /3 Therefore, seal.

for a given application, providing a third mechanical seal may allow the sealing pressure -6 -of each, the first mechanical seal, the second mechanical seal, and the third mechanical seal may be reduced in comparison to the same application wherein only the first mechanical seal and the second mechanical seal are provided.

Reducing the required sealing pressure of each mechanical seal in the washpipe cartridge (e.g. by providing a third mechanical seal) may reduce the likelihood of failure of each mechanical seal. Therefore, reducing the required sealing pressure of each mechanical seal in the washpipe cartridge may increase the expected useful lifetime of the washpipe cartridge in comparison to the expected useful lifetime of a washpipe cartridge comprising fewer mechanical seals.

The washpipe cartridge may comprise: a controller configured to: provide the first supply of barrier fluid at a first barrier fluid pressure, wherein the first barrier fluid pressure is based on the pressure of the drilling mud.

The first barrier fluid pressure may be greater than the pressure of the drilling mud.

The controller may be configured to provide the second supply of barrier fluid at a second barrier fluid pressure, wherein the second barrier fluid pressure is based on any 20 of: the pressure of the drilling mud; and, the first barrier fluid pressure.

The second barrier fluid pressure may be less than the first barrier fluid pressure, for example half the first barrier fluid pressure.

In examples wherein the drilling mud is provided at pressures of up to 520 bar, the first barrier fluid pressure may be 560 bar and the second barrier fluid pressure may be 280 bar. In such examples, the pressure of drilling mud in the drilling mud passage may be 520 bar, the pressure of the barrier fluid in the first gallery may be 560 bar, and the pressure of the barrier fluid in the second gallery may be 280 bar.

A supply of oil (e.g. such as clean oil) may be connected to at least one of: the first gallery inlet and the second gallery inlet. The supply of oil may enter the first gallery via the first gallery inlet at a first barrier fluid pressure. The supply of oil may enter the -7 -second gallery via the second gallery inlet at a second barrier fluid pressure. Oil supplied to the first gallery may lubricate any of: the first seal; and, the second seal. Oil supplied to the second gallery may lubricate any of: the second seal; and, the third seal.

Lip seals may be lubricated by drilling mud which may provide seals which exhibit a high sealing friction (e.g. seal friction in a lip seal may be defined as the friction between the static lip seal and the rotating sleeve of the washpipe assembly). High sealing friction may lead to significant heat generation and power losses in a top drive. The seals in the washpipe cartridge of the present disclosure may be lubricated by oil which may provide seals which exhibit a reduced sealing friction of the washpipe cartridge in comparison to lip seals. Accordingly, the seals of the washpipe cartridge of the present disclosure may have reduced heat generation and reduced power losses in a top drive. Therefore, the expected useful lifetime of washpipe cartridges provided by the present disclosure may be increased in comparison to other washpipe cartridges.

Seals in some washpipe cartridges (e.g. lip seals; mechanical seals) may contact drilling mud. Seals in these washpipe cartridges (e.g. mechanical seals) may be lubricated by drilling mud. Drilling mud may comprise chemical compositions which are abrasive and/or corrosive to the seals. Oil (e.g. clean oil) may comprise chemical compositions which are less abrasive and/or corrosive to seals than drilling mud. Accordingly, seals which are contacted by and/or lubricated by drilling mud may have a greater rate of wear than seals which are contacted by and/or lubricated by Oil (e.g. clean oil). Advantageously, connecting a supply of oil (e.g. clean oil) to any of: the first gallery (via the first gallery inlet); and the second gallery (via the second gallery inlet), may provide a seals with greater expected useful lifetime than other seals lubricated by drilling mud. Accordingly, a washpipe cartridge with a greater expected useful lifetime may be provided.

In examples wherein at least one of the mechanical seals comprises diamond coated 30 tungsten carbide and the supply of barrier fluid comprises oil (e.g. clean oil), the sealing friction may be reduced in comparison to providing either diamond or oil (e.g. clean oil) singly. -8 -

In examples at least one of the mechanical seals comprises tungsten carbide.

The controller comprises any of: a pneumatic system; a hydraulic system; an electromechanical system; and an electronic system.

For example, a controller may comprise: an electronic system having control logic for generating control instructions; and, any of: a pneumatic system; a hydraulic system; and, an electro-mechanical system, configured to implement the control instructions.

In examples, wherein the controller comprises an electronic system, a computer program product may be provided, the computer program produce comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method. Embodiments of the disclosure may provide tangible, non-transitory storage media comprising program instructions operable to program a processor to perform any one or more of the methods described and/or claimed herein and/or to provide data processing apparatus as described and/or claimed herein.

At least one of the mechanical seals may comprise diamond coated tungsten carbide. For example, any of the primary rings of the mechanical seals may comprise diamond coated tungsten carbide e.g. a diamond coating over a tungsten carbide core. For example, any of the mating rings of the mechanical seals may comprise diamond coated tungsten carbide e.g. a diamond coating over a tungsten carbide core.

Advantageously, providing a mechanical seal which comprises diamond coated tungsten carbide may provide a mechanical seal with a low coefficient of friction in comparison to other mechanical seals (e.g. comprising any of: silicon carbide; tungsten carbide; and carbon (graphite)). Accordingly, mechanical seal which comprises diamond coated tungsten carbide may exhibit a low sealing friction in comparison to other seals (e.g. lip seals; mechanical seals). Low sealing friction may lead to a reduction in heat generation and reduction in power losses in a top drive. Therefore, a more efficient washpipe cartridge may be provided.

Furthermore, reducing sealing friction may reduce the rate of wear on the seals, -9 -advantageously, increasing the expected useful lifetime of said seals Accordingly, the expected useful lifetime of the washpipe provided by the present disclosure may be increased.

The washpipe cartridge may comprise: at least one articulation joint, the articulation joint comprising: a top axial side; and, a bottom axial side, wherein the first articulation joint is configured to permit at least one of: longitudinal movement, parallel to the rotational axis, of the top axial side relative to the bottom axial side and,; pivoting of any of: the top axial side; and, the bottom axial side, transverse to the rotational axis.

A first articulation joint may be provided, wherein: the first seal and the second seal are disposed on the bottom axial side of the first articulation joint; and, when the washpipe cartridge is fit between the goose neck pipe and the drill string, the goose neck pipe is disposed on the top axial side of the first articulation joint.

The first articulation joint permits a variety of relative movements between a goose neck pipe and a washpipe cartridge which may advantageously reduce the likelihood of drilling mud leaking between the goose neck pipe and the washpipe cartridge (e.g. a leak from the interface between the goose neck pipe and the washpipe cartridge).

A second articulation joint may be provided, wherein: the first seal and the second seal are disposed on the top axial side of the second articulation joint; and, when the washpipe cartridge is fit between the goose neck pipe and the drill string, the drill string is disposed on the bottom axial side of the second articulation joint.

The second articulation joint permits a variety of relative movements between a drill string and a washpipe cartridge which may advantageously reduce the likelihood of drilling mud leaking between the goose neck pipe and the drill string (e.g. a leak from the interface between the drill string and the washpipe cartridge).

The disclosure provides a controller configured to perform the methods described herein. In examples, the controller may comprise any of: a pneumatic system; a hydraulic system; an electro-mechanical system; and, an electronic system.

20 25 30 -10 -The disclosure provides a method of operating a washpipe cartridge in a drilling mud system, the method comprising: providing a first supply of barrier fluid at a first barrier fluid pressure to a first gallery of a washpipe cartridge, wherein the first barrier fluid 5 pressure is based on the pressure of the drilling mud.

The method may further comprise: providing a second supply of barrier fluid at a second 10 barrier fluid pressure to a second gallery of the washpipe cartridge, wherein the second barrier fluid pressure is based on at least one of: the pressure of the drilling mud; and, the first barrier fluid pressure.

The second barrier fluid pressure may be less than the first barrier fluid pressure. For 15 example the second barrier fluid pressure is half the first barrier fluid pressure.

The first supply of barrier fluid; and/or, the second supply of barrier fluid may comprise oil. For example, the first supply of barrier fluid and/or the second supply of barrier fluid 25 may comprise a lubricant such as oil, for example, clean oil, for example oil free of particulate matter.

Seals in washpipe cartridges (e.g. mechanical seals; lip seals) which are contacted by and/or lubricated by drilling mud may lead to the seals exhibiting a high sealing friction (e.g. seal friction may be defined as the friction between seal components of a particular seal and/or friction between seal components of a particular seal and another component of the washpipe cartridge (e.g. the sleeve)). High sealing friction leads to significant heat generation and power losses in a top drive. The seals in the washpipe cartridge of the present disclosure are lubricated by oil (e.g. clean oil) which may provide a seals which exhibit a reduced sealing friction of the washpipe cartridge in comparison to other seals. Accordingly, the seals of the washpipe cartridge of the present disclosure may have reduced heat generation and reduced power losses in a top drive.

In examples wherein at least one of the seals comprises diamond coated tungsten carbide and the supply of barrier fluid comprises oil (e.g. clean oil), the sealing friction may be reduced in comparison to providing either diamond or oil singly.

Any of the washpipe cartridges described herein may be used to perform any of the methods described herein.

The disclosure provides a method of operating any of the washpipe cartridges described herein, the method comprising: providing a first supply of barrier fluid at a first barrier 15 fluid pressure to a first gallery of a washpipe cartridge, wherein the first barrier fluid pressure is based on the pressure of the drilling mud.

The method of operating any of the washpipe cartridges described herein may further comprise: providing a second supply of barrier fluid at a second barrier fluid pressure to a second gallery of the washpipe cartridge, wherein the second barrier fluid pressure is based on at least one of: the pressure of the drilling mud; and, the first barrier fluid pressure.

Herein the terms "drilling mud" and "mud" may be defined as terms that are generally synonymous with "drilling fluid" and that encompasses most fluids used in hydrocarbon drilling operations, especially fluids that contain significant amounts of suspended solids, emulsified water or oil. Mud may include all types of water-base, oil-base and synthetic-base drilling fluids. Drill-in, completion and workover fluids may sometimes be called muds, although a fluid that is essentially free of solids may not strictly considered mud. Herein the term "drilling mud" may be synonymous with "mud".

-12 -Herein the term "washpipe cartridge" may be synonymous with the term "washpipe".

Herein the term "expected useful lifetime of a washpipe cartridge" may be defined as the total period of continuous operation of the washpipe cartridge before the washpipe 5 cartridge permits leakage of drilling mud from the washpipe cartridge e.g. the total period of continuous operation of the washpipe cartridge before failure of the washpipe.

Herein the term "expected useful lifetime of a seal" may be defined as the total period of continuous operation of a washpipe cartridge comprising the seal before the seal permits 10 leakage of drilling mud therethrough e.g. the total period of continuous operation of a washpipe before failure of the seal.

Herein the term "clean oil" may refer to oil which is not contaminated by foreign particles (e.g. particulates; sand) or fluids (e.g. water) and which has not been degraded through 15 extended use..

In examples, the clean oil may comprise an oil type and/or a viscosity which is appropriate (e.g. suitable) for a given application.

Herein the term "sealing pressure" may be defined as the minimum pressure of fluid which a seal is configured to seal against. For example, a seal configured to seal a fluid with a pressure of 520 bar must have a sealing pressure of at least 520 bar.

Figures Embodiments of the disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 illustrates a perspective view of a washpipe cartridge; Figure 2 illustrates a longitudinal cross-sectional view of the washpipe cartridge Figure 3 illustrates a longitudinal cross-sectional view of the washpipe cartridge disposed between a stationary goose neck pipe and a drill string; Figure 4 shows a flowchart illustrating the steps in a method of operating a washpipe cartridge in a drilling mud system; -13 -Figure 5 illustrates a drilling assembly for hydrocarbon exploration.

In the figures, like numerals denote like elements.

Specific description

Figure 1 illustrates a perspective view of a washpipe cartridge 100. Figure 2 illustrates a longitudinal cross-sectional view of the washpipe cartridge 100.

The washpipe 100 comprises: a sleeve 102; a housing 104; a longitudinal axis 105; a 10 first seal 106; a second seal 108; a third seal 110; a first gallery 112; a second gallery 114; a first gallery inlet 116; a second gallery inlet 118; a drilling mud pressure sensor 120; a mud passage 122; and, bearings 130.

The housing 104 is a cylindrical pipe which comprises: a housing body 154; and, a goose 15 neck pipe connecting part (e.g. goose neck pipe connector). The goose neck pipe connecting part comprises: a housing collar 164; and, a first articulation joint 172.

The sleeve 102 is a cylindrical pipe which sits inside a portion of the housing 104 and comprises: a sleeve body 152; and, a drill string connecting part (e.g. drill string 20 connector). The drill string connecting part comprises: a sleeve collar 162; and, a second articulation joint 174.

The housing 104 and the sleeve 102 together define a mud passage 122 inside the housing 104 and the sleeve 102. The first seal 106 is disposed outside the sleeve 102, between the housing 104 and the sleeve 102. The second seal 108, and the third seal 110 are both also disposed between the housing 104 and the sleeve 102 spaced axially along the sleeve from the first seal 106. The second seal 108 is disposed between the first seal 106 and the third seal 110. The first gallery 112 is disposed between the first seal 106 and the second seal 108, and the second gallery 114 is separated from the first gallery 112 by the second seal 108. The second gallery 114 is disposed between the second seal 108 and the third seal 110.

The first gallery inlet 116 is in fluid communication with the first gallery 112. The second -14 -gallery inlet 118 is in fluid communication with the second gallery 114. The drilling mud pressure sensor 120 is in fluid communication with the mud passage 112. The bearings 130 are disposed between: the sleeve 102; and, the housing 104.

The first seal and the second seal are disposed on a first bottom axial side of the first articulation joint 172; and, when the washpipe cartridge 100 is fitted between the goose neck pipe and the drill string, the goose neck pipe is disposed on a first top axial side of the first articulation joint 172. The first articulation joint 172 is disposed between: the housing body 154; and, the housing collar 164. The housing body 154 is disposed on a first top axial side of the first articulation joint 172. The housing collar 164 is disposed on a first bottom axial side of the first articulation joint 172.

The first seal and the second seal are disposed on a second top axial side of the second articulation joint; and, when the washpipe cartridge 100 is fitted between the goose neck pipe and the drill string, the drill string is disposed on a second bottom axial side of the second articulation joint 174. The second articulation joint 174 is disposed between: the sleeve body 152; and, the sleeve collar 162. The sleeve collar 162 is disposed on a second top axial side of the second articulation joint 174. The sleeve body 152 is disposed on a second bottom axial side of the second articulation joint 174.

The washpipe cartridge 100 is configured to fit between a goose neck pipe and a drill string. The washpipe cartridge 100 is configured to provide a rotary coupling between a goose neck pipe and a drill string.

A portion of the housing 104 (e.g. at least part of the housing body 154) is sized to receive a portion of the sleeve 102 (e.g. at least part of the sleeve body 152). For example, a portion of the sleeve 102 is sized to fit within the housing 104.

When the portion of the housing 104 is disposed within (e.g. received by) a portion of the sleeve 102 the longitudinal axis 105 of the washpipe cartridge extends through the sleeve 102 and the longitudinal hole of the housing 104. When the portion of the housing 104 is disposed within (e.g. received by) a portion of the sleeve 102, the portion of the sleeve 102 is seated on the bearings 130. In this configuration the interior of the housing 104 and the interior of the sleeve 102 together define the mud passage 122.

The housing 104 is configured to remain rotationally stationary relative to the longitudinal axis 105 e.g. the housing 104 is not permitted to rotate about the longitudinal axis 105.

The sleeve 102 is configured to rotate about the longitudinal axis 105 relative to the housing 102. The bearings 130 between the sleeve 102 and the housing may be configured to permit relative rotation between the sleeve 102 and the housing 104.

The housing 104 is attachable (e.g. configured to be fixedly attached) to a goose neck pipe of a top drive e.g. the housing 104 is attachable to a goose neck pipe such that, in use, there is no relative rotation between the housing 104 and the goose neck pipe. The goose neck pipe connecting part of the housing 104 is be configured to connect (e.g. fixedly attach) the goose neck pipe and the housing body 154. In the example shown in Figure 2, the housing collar 164 of the housing 104 is configured to connect (e.g. fixedly attach) a goose neck pipe and the housing body 154.

The sleeve 102 is attachable (e.g. configured to be fixedly attached) to a drill string of a top drive e.g. the sleeve 102 is attachable to a drill string such that, in use, there is no relative rotation between the sleeve 102 and the drill string and such that, in use, both the sleeve 102 and the drill string rotate about the longitudinal axis 105. The drill string connecting part of the sleeve 102 is be configured to connect (e.g. fixedly attach) the drill string and the sleeve body 152. The sleeve collar 162 of the sleeve 102 may be configured to connect (e.g. fixedly attach) the drill string and the sleeve body 152.

The first seal comprises a first mechanical seal. The first mechanical seal comprises: a first primary ring; and, a first mating ring. The second seal comprises a second mechanical seal. The second mechanical seal comprises: a second primary ring; and, a second mating ring. The third seal comprises a third mechanical seal. The third mechanical seal comprises: a third primary ring; and, a third mating ring.

Each of the primary rings has a primary ring axial face and each of the mating rings has a mating ring axial face. In a mechanical seal the primary ring axial face axially opposes the mating ring axial face (e.g. an axial end of one of the rings faces an axial end of the -16 -other ring). In each of the mechanical seals the mating ring is configured to resist axial movement thereof (e.g. the first mating ring is axially stationary) and the primary ring is configured to permit axial movement thereof (e.g. the first primary ring is axially movable).

In examples, in a given mechanical seal, at least one of the primary ring and the mating ring is movable along the rotational axis; and, the first primary ring and the first mating ring are biased together e.g. such that the distance between the primary ring axial face and the mating ring axial face may be reduced.

In examples, the third seal may be omitted.

The first mechanical seal is configured to permit barrier fluid to pass between the first primary ring axial face and the first mating ring axial face. For example, if in use, the 15 barrier fluid is provided at a pressure which is greater than the drilling mud pressure, then the barrier fluid will pass between the first primary ring axial face and the first mating ring axial face from the first gallery 112 into the mud passage 122. Accordingly, contact between the first mechanical seal and the drilling mud is prevented by the barrier fluid which passes between the first primary ring axial face and the first mating ring axial face. 20 The first gallery inlet 116 is configured to permit a first supply of barrier fluid to enter the first gallery 112. The first gallery 112 is configured to receive a first supply of barrier fluid via the first gallery inlet 116. The first supply of barrier fluid may be provided by a controller (not shown in Figure 1 and Figure 2).

The second gallery inlet 118 is configured to permit a first supply of barrier fluid to enter the second gallery 114. The second gallery 114 is configured to receive a barrier fluid via the second gallery inlet 118. The second supply of barrier fluid may be provided by a controller (not shown in Figure 1 and Figure 2).

In examples, any of the: first supply of barrier fluid; and, the second supply of barrier fluid, may comprise oil (e.g. clean oil).

-17 -The mud passage 122 is configured to receive mud from a goose neck pipe. For example, when the washpipe cartridge 100 is connected to a goose neck pipe, the mud passage 122 may receive mud from the goose neck pipe. The mud passage 122 is configured to provide mud to a drill string. For example, when the washpipe cartridge 100 is connected to a drill string, the mud passage 122 may provide mud from the goose neck pipe.

The drilling mud pressure sensor 120 is configured to determine the pressure of mud in the mud passage 122 e.g. the drilling mud pressure sensor 120 is configured to 10 determine a determined drilling mud pressure. The drilling mud pressure sensor 120 may be configured to provide the determined drilling mud pressure to the controller.

For example, the drilling mud sensor 120 may be in fluid communication with the mud passage 122 so that the drilling mud sensor 120 and the mud passage are in direct 15 contact (e.g. mud touches the drilling mud sensor 120). In such examples, the drilling mud sensor 120 can directly determine the pressure of the mud in the mud passage 122.

In examples, the drilling mud sensor 120 may be in fluid communication with the mud passage so that the drilling mud sensor and the mud passage are in indirect contact (e.g. 20 mud does not touch the drilling mud sensor). In such examples, the drilling mud sensor can indirectly determine (e.g. infers) the pressure of the mud in the mud passage.

In examples, the drilling mud sensor may be omitted. In such examples, the controller may receive the drilling mud pressure from a storage location. For example, the storage location may be a storage location which is local to the controller (e.g. a local storage location) or the storage location may be a storage location which is remote to the controller (e.g. a remote storage location).

The drilling mud pressure may be determined before operation of the top drive. For example, for a given washpipe cartridge and top drive, the pressure of the drilling mud under normal operating conditions may be known. Accordingly, the drilling mud pressure (e.g. the pressure of the drilling mud under normal operating conditions) may be stored in the storage location (e.g. input by a user; received from a drilling mud pressure sensor).

-18 -The first articulation joint 172 is configured to permit: longitudinal movement, parallel to the rotational axis, of the first top axial side relative to the first bottom axial side and, pivoting of: the first top axial side; and, the first bottom axial side, transverse to the 5 rotational axis 105.

The second articulation joint 174 is configured to permit: longitudinal movement, parallel to the rotational axis, of the second top axial side relative to the second bottom axial side; and, pivoting of: the second top axial side; and, the second bottom axial 10 side, transverse to the rotational axis 105.

Figure 3 illustrates a longitudinal cross-sectional view of the washpipe cartridge 100 disposed between a stationary goose neck pipe 201 and a drill string 202.

The washpipe cartridge is connected to the goose neck pipe 201.

The washpipe cartridge is connected to the drill string 202.

A controller is provided (not shown in Figure 3). The controller is configured provide a first supply of barrier fluid a first barrier fluid pressure. The controller is configured to 20 provide the first supply of barrier fluid to the first gallery 112 e.g. via the first gallery inlet 116. The first barrier fluid pressure is based on the pressure of the drilling mud. For example, the controller may be configured to provide a first supply of barrier fluid at a first barrier fluid pressure which is greater than the pressure of the drilling mud. The first supply of barrier fluid and the second supply of barrier fluid comprise oil (e.g. clean oil). 25 The controller is configured to receive a drilling mud pressure. The controller is configured to provide a first supply of barrier fluid at a first barrier fluid pressure. The controller is configured to provide a second supply of barrier fluid at a second barrier fluid pressure.

The controller is a pneumatic system. The pneumatic system may comprise a compressed air supply configured to drive a positive displacement pump. The positive displacement pump may be configured to pressurise an oil accumulator.

-19 -Advantageously, compressed air is readily available at the site of most top drives. The positive displacement pump may be configured to stall when a maximum accumulator pressure has been reached. The positive displacement pump may be configured to restart when accumulator pressure drops below the maximum accumulator pressure. The 5 first stage barrier fluid supply may be configured such that the first stage barrier fluid pressure tracks at a set margin above the drilling mud pressure, for example it may be different from the drilling mud pressure by a constant pressure differential such as an offset or scaling (e.g. an offset of 40 bar or a doubling). One way to do this is to use a bias control valve. The hydraulic pressure in subsequent seal galleries may be set 10 similarly, for example, using valving arrangements (such as fixed valving) to set pressure based on the first stage barrier fluid.

A controller which comprises a pneumatic system may not require an electronic system. Accordingly, the controller may not comprise an electronic system. Advantageously, dispensing with an electronic system may remove potential ignition sources in the controller. Therefore, the likelihood of ignition of any flammable materials around the washpipe cartridge or controller (e.g. oil; gases) is reduced. Furthermore, providing a controller comprising a pneumatic system may allow for simpler compliance with ATEX requirements (or similar regional requirements relating to explosive atmospheres).

Furthermore, omission of an electronic system correspondingly omits the need for a complex control and/or communication wiring harnesses around the washpipe cartridge (which may be an area of restricted space).

In other examples, (not shown) the controller may comprise any of: a pneumatic system; 25 a hydraulic system, and, an electronic system.

The goose neck 201 is configured to provide drilling mud from a drilling mud reservoir (e.g. a mud pit). The goose neck 201 is fixable to the washpipe 100. The goose neck 201 is irrotationally fixable to the washpipe 100 e.g. the goose neck 201 is fixable to the washpipe 100 in a manner wherein the relative rotation between the goose neck 201 and the washpipe 100 is not permitted.

The drill string 202 is configured to receive drilling mud from the washpipe 100. The drill -20 -string 202 is fixable to the washpipe 100. The drill string 202 is rotationally fixable to the washpipe 100 e.g. the drill string 202 is fixable to the washpipe 100 in a manner wherein the relative rotation between the drill string 202 and the washpipe 100 is permitted.

In use the drill string is disposed within a drill hole formed in the surface of the Earth. Drilling mud is provided from the drilling mud reservoir (e.g. mud pit) to the goose neck 201. For example, the drilling mud may be pumped by a mud pump from a mud pit and through a discharge line to the goose neck. The drilling mud passes from the goose neck 201 to the washpipe 100. The drilling mud passes from the washpipe 100 to the drill string 202. The drilling mud exits the drill string 202 into the drill hole. The debris generated from the action of the drill string is entrained within the drilling mud. The drilling mud and the entrained debris are recovered from the drill hole. For example, the drilling mud and the entrained debris are fed through a flow-line to the mud pit. The debris is removed from the drilling mud. For example, a shale-shaker configured to remove the debris from the drilling mud, may be provided between the flow-line and the mud pit. The drilling mud is returned to the reservoir.

In use the drilling mud pressure sensor determines the pressure of the drilling mud e.g. the drilling mud pressure sensor 120 is configured to determine a drilling mud pressure. 20 The drilling mud pressure sensor 120 provides the drilling mud pressure to the controller.

In use, the first mechanical seal permits barrier fluid to pass between the first primary ring axial face and the first mating ring axial face. The barrier fluid is provided at a pressure which is greater than the drilling mud pressure. The barrier fluid passes from the first gallery 112 to the mud passage 122. Advantageously, the barrier fluid prevents the drilling mud from contacting the first mechanical seal (or the second and third mechanical seal).

The present disclosure provides a method of operating a washpipe cartridge in a drilling 30 mud system. Figure 4 shows a flowchart illustrating the steps in the method. The method may be performed by a controller. The method comprises: Providing, S401, a first supply of barrier fluid at a first barrier fluid pressure to a first -21 -gallery of a washpipe cartridge, wherein the first barrier fluid pressure is based on the pressure of the drilling mud. For example, the first barrier fluid pressure may be based on a drilling mud pressure.

The step S401 may comprise receiving, by the controller, a drilling mud pressure.

For example, a drilling mud sensor may be provided as shown in Figures 1 to 3. The drilling mud pressure sensor may be configured to determine the pressure of the drilling mud e.g. an indication such as an electrical signal which is indicative of the pressure of 10 the drilling mud.

In examples, a storage location may provide a drilling mud pressure. For example, the storage location may be a storage location which is local to the controller (e.g. a local storage location) or the storage location may be a storage location which is remote to the 15 controller (e.g. a remote storage location).

The drilling mud pressure may be a predetermined. For example, for a given washpipe cartridge and top drive, the pressure of the drilling mud under normal operating conditions may be known. Accordingly, a drilling mud pressure under normal operating conditions may be stored in the storage location (e.g. input by a user; received from a drilling mud pressure sensor).

In examples, the first barrier fluid pressure is greater than the pressure of the drilling mud. For example, a first barrier fluid pressure may be determined based on the drilling 25 mud pressure, such that the first barrier fluid pressure is greater than the pressure of the drilling mud.

The step S401 may comprise any of: determining a first barrier fluid pressure based on the drilling mud pressure; and, providing, a first supply of barrier fluid at the first barrier 30 fluid pressure to a first gallery of a washpipe cartridge.

For example, the first barrier fluid pressure may be determined by modifying the drilling mud pressure by a first barrier fluid pressure differential. For example, the first barrier -22 -fluid pressure may be determined by additively combining the drilling mud pressure and the first barrier fluid pressure differential. It will be appreciated that this can be done by any of: pneumatic; hydraulic; electromechanical; and, electrical systems.

The first barrier fluid pressure differential may not be a fixed offset for every type of washpipe cartridge. The first barrier fluid pressure differential may be determined by considering design factors of the washpipe cartridge.

The pressure differential between the drilling mud pressure and the first barrier fluid pressure may be selected based on one or more of: geometry of the seals in the washpipe cartridge; the rotational speed (e.g. angular speed) between the sleeve and the housing; the rotational speed (e.g. angular speed) between the drill string and the goose neck pipe (in examples, the rotational speed between the sleeve and the housing and the rotational speed between the drill string and the goose neck pipe may be the same); the type of barrier fluid; a determined safety margin against drilling mud pressure fluctuations.

In examples, the selected pressure differential and/or the first barrier fluid pressure may be determined at a design stage. Other minor adjustments which allow for hydraulic system variance may remain constant during operation of the washpipe cartridge. The first barrier fluid pressure and/or the first pressure fluid pressure differential may depend on the design of the seals in the washpipe cartridge and the operating requirements of the seals. In the example described below, a selected pressure differential is determined to be 40 bar.

In examples wherein the drilling mud pressure is 520 bar, the first barrier fluid pressure may be 560 bar. In such examples, the first barrier fluid pressure differential may be 14/13 (e.g. if the drilling mud pressure is scaled by the first barrier fluid pressure differential) or 40 (e.g. if the first barrier fluid pressure differential is addifively combined to the drilling mud pressure).

Advantageously, providing a first supply of barrier fluid at a first barrier fluid pressure to a first gallery of a washpipe cartridge, wherein the first barrier fluid pressure is based -23 -on the pressure of the drilling mud, wherein the first barrier fluid pressure is greater than the pressure of the drilling mud, may prevent drilling mud passing between the housing and the sleeve of the washpipe cartridge.

Providing, S402, a second supply of barrier fluid at a second barrier fluid pressure to a second gallery of a washpipe cartridge, wherein the second barrier fluid pressure is based on any of: the pressure of the drilling mud; and, the first barrier fluid pressure. For example, the second barrier fluid pressure may be based on the first barrier fluid pressure or a drilling mud pressure.

In examples, wherein the second barrier fluid pressure is based on the pressure of the drilling mud, the step S402 may comprise receiving, by the controller, a drilling mud pressure. As set out above, the drilling mud pressure may be received from any of: a drilling mud pressure sensor; a local storage location; and, a remote storage location.

In examples, the second barrier fluid pressure may be less than the first barrier fluid pressure, for example the second barrier fluid pressure may be half the first barrier fluid pressure.

In examples, wherein the second barrier fluid pressure is based on the pressure of the drilling mud, the step S402, may comprise: determining a second barrier fluid pressure based on the drilling mud pressure; and, providing, a second supply of barrier fluid at the second barrier fluid pressure to a second gallery of a washpipe cartridge.

For example, the second barrier fluid pressure may be determined by multiplying the drilling mud pressure by a constant. For example, the second barrier fluid pressure may be determined by multiplying the drilling mud pressure by 7/13. In examples wherein the drilling mud pressure is 520 bar, the second barrier fluid pressure may be 280 bar.

For example, the constant may be determined such that the second barrier fluid pressure is half of the first barrier fluid pressure.

-24 -In examples, wherein the second barrier fluid pressure is based on the first barrier fluid pressure, the step S402, may comprise: determining a second barrier fluid pressure based on the first barrier fluid pressure; and, providing, a second supply of barrier fluid at the second barrier fluid pressure to a second gallery of a washpipe cartridge.

For example, the second barrier fluid pressure may be determined by multiplying the first barrier fluid by a constant. For example, the second barrier fluid pressure may be determined by multiplying the first barrier fluid pressure by 0.5. In examples wherein the first drilling mud pressure is 560 bar, the second barrier fluid pressure may be 280 bar.

Figure 5 illustrates a drilling assembly for hydrocarbon recovery. The drilling assembly comprises; a top drive 1000; a goose neck pipe 201; a drill string 202; a flow line 502; a shale shaker 503; a mud pit (e.g. mud reservoir) 504; a mud pump 505; and, a discharge line 506. The top drive 1000 comprises a washpipe cartridge such any of the washpipe cartridges described or claimed herein.

The goose neck pipe 201 is connected to the washpipe of the top drive 1000. The washpipe cartridge of the top drive 1000 is connected to the drill string 202. The drill string 202 is disposed in a drill hole 501. The flow line 502 is in fluid communication with the hole. The flow line 502 is connected to the shale shaker 503. The shale shaker 503 is disposed between the flowline 502 and the mud pit 504. The mud pump 505 is connected to the mud pit (e.g. mud reservoir) 504. The mud pump 505 is connected to the discharge line506. The discharge line is connected to the goose neck pipe 201.

In use the drill string 201 is disposed within a drill hole formed in the surface of the Earth. Drilling mud is pumped by mud pump 505 from the mud pit 504 and through the discharge line 506 to the goose neck pipe 201. The drilling mud passes from the goose neck pipe 201 to the washpipe of the top drive 1000. The drilling mud passes from the washpipe to the drill string 202. The drilling mud exits the drill string 202 into the drill hole. Debris generated from the action of the drill string is entrained within the drilling mud. The drilling mud and the entrained debris are recovered from the drill hole via flow-line 502 to the mud pit 504. The shale shaker 503 configured to remove the debris from the drilling mud. The drilling mud is returned to the mud pit 504.

-25 -The disclosure may utilise all types of mechanical seal. For example, the invention is applicable to all types of end-face mechanical seals for use in rotating equipment. Herein the term rotating equipment may refer to any apparatus comprising a driver side and a driven side, wherein the driver side is coupled to the driven side by a coupling between two rotary shafts or between a rotary shaft and some other driven member. Examples of rotating equipment include: washpipe cartridges; compressors; and, process pumps. End-face mechanical seal may be used to prevent leakage of fluid from an inboard side to an outboard side of the mechanical seal.

End-face mechanical seals comprise a mating ring and a primary ring. Both the mating ring and the primary ring are annular circular cylinders. The mating ring is positioned so that an axial face (e.g. seal face) of the mating ring opposes an axial face of the primary ring. The mating ring is disposed on the driving side of the rotary coupling and is positioned so that an axis of rotation of the rotary coupling is coincident with the central longitudinal axis of the mating ring. The mating ring is rotatable about the axis of rotation of the rotary coupling e.g. by the shaft which drives the rotating equipment. The primary ring is disposed on the driven side of the rotary coupling and positioned so that an axis of rotation of the rotary coupling is coincident with the central longitudinal axis of the primary ring.

A seal fluid (e.g. barrier fluid such as, for example, oil (e.g. clean oil)) provides a thin film of fluid between the opposing faces of the primary ring and the mating ring. For example, the seal fluid may be fluid sealed by the mechanical seal provided by the primary ring and the mating ring. For example, the seal fluid may comprise any of the following types: process fluid; a buffer fluid; and, a barrier fluid. The type of seal fluid for a given mechanical seal may depend on the general mechanical seal arrangements as described by the API682 standard et alia. The thin film, sometimes referred to as a fluid film, generates hydrostatic forces (e.g. forces which are present regardless of whether the mating ring is stationary or rotating) and hydrodynamic forces (e.g. forces which are present only when the mating ring rotates) which are exerted on the mating ring and primary ring. Grooves may be provided on the mating ring (e.g. logarithmic spiral grooves) which are involved in generating the hydrodynamic forces, for example, when -26 -the mating ring rotates, the grooves may shear the seal fluid flow towards the central longitudinal axis of the mating ring which increases the pressure of the seal fluid flow.

In examples, the primary ring may be configured to rotate and the mating ring may be 5 configured to remain rotationally stationary.

Herein the term "ATEX requirements" may refer to the two European Directives for controlling explosive atmospheres Directive 99/92/EC and Dimctive 94/9/EC.

Claims

-27 -Claims 1. A washpipe cartridge for carrying drilling mud in a top drive of a drilling assembly, the washpipe cartridge comprising: a housing adapted to fit between a stationary goose neck pipe of the top drive and 5 a drill string, wherein the drill string is rotatable about a rotational axis, the housing comprising: a sleeve; and, a housing; wherein the sleeve is configured to provide the drilling mud to the drill string; and, 10 wherein the housing is configured to receive drilling mud from the goose neck pipe; wherein disposed between the sleeve and the housing is a first seal, a second seal and a first gallery between the first seal and the second seal, and wherein the cartridge further comprises: a first gallery inlet for providing a first supply of barrier fluid to the first gallery; a second gallery inlet for providing a second supply of barrier fluid to the second seal, wherein the second gallery inlet is separated from the first gallery by the second seal.
2. The washpipe cartridge of claim 1, wherein: the first seal and the second seal comprise mechanical seals.
3. A washpipe cartridge for carrying drilling fluid in a top drive of a drilling assembly, the washpipe cartridge comprising: a housing adapted to fit between a stationary goose neck pipe of the top drive and 25 a drill string, wherein the drill string is rotatable about a rotational axis, the housing comprising: a sleeve; and, a housing; wherein the housing is configured to provide the drilling mud to the drill string; and, 30 wherein the sleeve is configured to receive drilling mud from the goose neck pipe; wherein disposed between the sleeve and the housing is a first mechanical seal and a second mechanical seal.
-28 - 4. The washpipe cartridge of claim 3 comprising: a first gallery disposed between the first mechanical seal and the second mechanical seal; and, first gallery inlet for providing a first supply of barrier fluid to the first gallery.
5. The washpipe cartridge of claim 4 comprising: a second gallery inlet for providing a second supply of barrier fluid to the second mechanical seal, wherein the second gallery inlet is separated from the first gallery by the second mechanical seal.
6. The washpipe cartridge of any of the preceding claims, wherein: the housing comprises a goose neck pipe connecting part wherein the connecting part is configured to provide a coupling between the goose neck and the washpipe cartridge, wherein the first mechanical seal is disposed between the sleeve 15 and the connecting part.
7. The washpipe cartridge of claim 6, wherein: the second gallery is disposed between the second mechanical seal and a third mechanical seal.
8. The washpipe cartridge of any claims 1 to 2 and 4 to 7, comprising: a controller configured to: provide the first supply of barrier fluid at a first barrier fluid pressure, wherein the first barrier fluid pressure is based on the pressure of the drilling mud.
The washpipe cartridge of claim 8, wherein: the first barrier fluid pressure is greater than the pressure of the drilling mud.
10. The washpipe cartridge of any of claims 8 and 9, wherein: the controller is further configured to: provide the second supply of barrier fluid at a second barrier fluid pressure, wherein the second barrier fluid pressure is based on any of: -29 -the pressure of the drilling mud; and, the first barrier fluid pressure.
11. The washpipe cartridge of claim 10, wherein: the second barrier fluid pressure is less than the first barrier fluid pressure, for example half the first barrier fluid pressure.
12. The washpipe cartridge of any of the preceding claims, wherein a supply of oil is connected to at least one of: the first gallery inlet and the second gallery inlet.
13. The washpipe cartridge of any of claims 8 to 12, wherein: the controller comprises any of: a pneumatic system; and, a hydraulic system.
14. The washpipe cartridge of any of the preceding claims comprising: at least one articulation joint comprising: a top axial side; and, a bottom axial side, wherein the articulation joint is configured to permit at least one of: longitudinal movement, parallel to the rotational axis, of the top axial side relative to the bottom axial side; and, pivoting of any of: the top axial side; and, the bottom axial side, transverse to the rotational axis.
15. The washpipe cartridge of claim 14, comprising: a first articulation joint; wherein: the first seal and the second seal are disposed on the bottom axial side of the first articulation joint; and, when the washpipe cartridge is fit between the goose neck pipe and the drill string, the goose neck pipe is disposed on the top axial side of the first articulation joint.
16. The washpipe cartridge of any of claims 14 to 15, comprising: -30 -a second articulation joint; wherein: the first seal and the second seal are disposed on the top axial side of the second articulation joint; and, when the washpipe cartridge is fit between the goose neck pipe and the drill string, the drill string is disposed on the bottom axial side of the second articulation joint.
17. A method of operating a washpipe cartridge in a drilling mud system, the method comprising: providing a first supply of barrier fluid at a first barrier fluid pressure to a first gallery of a washpipe cartridge, wherein the first barrier fluid pressure is based on the pressure of the drilling mud; and, providing a second supply of barrier fluid at a second barrier fluid pressure to a second gallery of the washpipe cartridge, wherein the second barrier fluid pressure 15 is based on at least one of: the pressure of the drilling mud-and, the first barrier fluid pressure.
18. The method of claim 17, wherein: the first barrier fluid pressure is greater than the pressure of the drilling mud.
19. The method of any of claims 17 to 18, wherein: the second barrier fluid pressure is less than the first barrier fluid pressure, for example the second barrier fluid pressure is half the first barrier fluid pressure.
20. The method of any of claims 17 to 19, wherein any of: the first supply of barrier fluid; and, the second supply of barrier fluid comprise oil.
21. A controller configured to perform the method of any of claims 17 to 20. 30
22. A top drive comprising a goose neck pipe, a drill string connector and a washpipe, the washpipe comprising: -31 -a housing adapted to fit between the goose neck pipe the drill string connector, wherein the drill string is rotatable about a rotational axis, the housing comprising: a sleeve; and, a housing; wherein the housing is configured to provide the drilling mud to the drill string via the drill string connector; and, wherein the sleeve is configured to receive drilling mud from the goose neck pipe; the washpipe further comprising: a first seal, and, a second seal disposed between the sleeve and the housing; and, a first gallery disposed between the first seal and the second seal; and, a first gallery inlet for providing a first supply of barrier fluid to the first gallery.
23. Use of the washpipe of any of claims 1 to 16 to perform the method of any of claims 17 to 20.
24. A drilling assembly for hydrocarbon recovery comprising the washpipe of any of claims 1 to 16.