GB2529883A

GB2529883A - Filter apparatus

Info

Publication number: GB2529883A
Application number: GB1415777.0A
Authority: GB
Inventors: Jan Wojcieszyn
Original assignee: NTS HOLDING Ltd
Current assignee: NTS HOLDING Ltd
Priority date: 2014-09-05
Filing date: 2014-09-05
Publication date: 2016-03-09
Also published as: GB201415777D0

Abstract

A filter 210 including a body 214 having a plurality of apertures 220 through which fluid is able to pass wherein at least apportion of the apertures being provided in a substantially helical formation along at least a part of the length of the body. The filter may include a plurality of rows of apertures. The filter may be a mud filter for an oil well drilling string. The filter may include a fluid displacer. The at least one helical formation provided on the body of the filter may correspond with a helical formation of a or each channel of a fluid displacer. A fluid displacer for a filter, the fluid displacer includes at least one channel along which fluid is capable of passing. The channel may be provided in a helical formation. A set of channels may be provided which are connectable to a filter body and a second set of channels may be provided on a fluid transfer member. A filter sub 240 of an oil drilling string, wherein the filter sub includes a tubular body and at least one helical formation on an internal surface of the tubular body.

Description

Title: Filter apparatus

Description of Invention

The present invention relates to a filter and a filter apparatus, in particular, but not exclusively to a filter and a filter apparatus for use in filtration of oil well drilling fluids, in particular mud'.

It is known in the art of oil well technology to provide a "mud motor" as part of a drill string. The mud motor is a pump, typically a progressive cavity positive displacement pump (PCDP) and is used to provide additional power to a drill bit whilst drilling. The mud motor uses "mud", also referred to as drilling fluids, i.e. lubricants, to cool and lubricate the drill bit and other parts of a drilling assembly in the drill string, and to transmit energy to the drill bit and other tools, for example. The mud motor is used to produce rotational, eccentric or concentric motion which is transferred to the drill bit.

Typically, the mud motor includes a top sub which connects the mud motor the the drill string; a power section, which includes a rotor and stator; a transmission section where eccentric power from the rotor is transmitted as concentric power to the drill bit, typically via a constant velocity joint; a bearing assembly which protects the drilling tools; and a bottom sub, which connects the mud motor to the drill bit.

It is known in the art of oil well technology to provide a "mud filter" to filter the mud, which is typically positioned adjacent the mud motor, and above the mud motor in the drill string. Different types of mud filter are available, for example, slotted filters and bar filters. A known mud filter 10 is shown in Figure 1. The mud filter 10 is an example of a slotted filter, having a filter head 12, a body 14 and a fluid displacer 16, which is referred to herein as an internal mud displacer 16, which is known in the art as a "torpedo".

The body 14 is substantially cylindrical, and has a first end 14a, a second end 14b, and a body wall 15. The body 14 is substantially tubular, having an opening 18, which is defined by the wall 15 and extends between the first end 14a and the second end 14b. The body 14 has an external diameter of between approximately 1 inch (25.4mm) and approximately 9 5/8 inches (244 48mm), depending upon the bore size of the drill string. The wall 15 of the type of mud filter 10 shown in Figure 1 is typically manufactured from pressed metal, preferably 4mm thick 304 stainless steel, although it will be appreciated that other materials are also suitable.

A plurality of apertures 20 extend through the wall 15 of the body 14. The apertures 20 are arranged in rows along substantially the whole length of the body 14. Apertures 220 are provided around substantially the whole circumference of the body 14.

Each aperture 20 in the example of the mud filter 10 shown in Figure 1 is elongate, and has rounded ends. Alternative shaped apertures are also known, for example circular.

The filter head 12 is substantially circular and provides a cap at the first end 14a of the body 14. The filter head 12 includes an opening, through which mud may pass, into the body 14.

The internal mud displacer 16 includes a connecting formation 22 and a fluid transfer member 24. In the example shown, the connecting formation 22 is a boss 22 which has a first end and a second end, and is receivable in the second end 14b of the body 14 to at least partially close the opening 18 at the second end 14b. The boss 22 is substantially conical, and includes a plurality of elongate grooves which extend axially along an outer surface of the boss 22, over at least a part of the length of the boss 22. Each groove is parallel with a longitudinal axis of the internal mud displacer 16.

The fluid transfer member 24 is substantially circular in cross section, and has a diameter which is smaller than the bore of the drill string with which it is intended to be used. The fluid transfer member 24 also includes a plurality of elongate grooves, each of which extends axially along at least a part of the length of the fluid transfer member 24, along an outer surface thereof, parallel with the longitudinal axis of the internal mud displacer 16. Each groove of the fluid transfer member is in fluid communication with a groove of the boss 22.

The internal mud displacer 16 shown in Figure 1 also includes a plurality of fins 30, each of which is connected to the outer surface of the fluid transfer member 24, and extends radially outwardly. The maximum radial extent of each fin 30 substantially corresponds with the inner diameter of the bore with which the filter 10 is intended to be used. The purpose of the fins 30 is to inhibit bending, flexing and other deviations of the mud filter 10 when it is in use within the drill string.

An alternative type of prior art mud filter 110 is shown in Figure 2. The filter includes a filter head 112, a body 114 and an internal mud displacer 116.

The filter head 112 and the internal mud displacer 116 are similar to those described in relation to the filter 10.

The body 114 is substantially tubular, but includes a plurality of bars 115 of metal, rather than a wall of sheet metal. The body 114 includes a plurality of apertures 120, which are defined by gaps between the bars 115. Each bar extends substantially axially along the body 114. The body 114 also includes a plurality of substantially circular bands 121, which are spaced axially along the body 114, to strengthen the body 114, and to maintain its tubular shape.

In accordance with the present invention, there is provided a filter including a body having a plurality of apertures through which fluid is able to pass, to at least assist in the performance of filtration of the fluid, at least a proportion of the apertures being provided in a substantially helical formation along at least a part of the length of the body.

The filter may include a plurality of helical formations provided by the apertures.

The filter may include a plurality of rows of apertures, wherein at least one row of apertures is provided in a helical formation.

The filter may be a mud filter for an oil well drilling string.

In accordance with a second aspect of the invention, there is provided a fluid displacer for a filter, the fluid displacer including at least one channel along which fluid is capable of passing.

The fluid displacer may include at least one channel along which fluid is capable of passing, the channel being provided in a helical formation.

The fluid displacer may include a plurality of channels, at least one of which is provided in a helical formation.

The fluid displacer may include a first set of channels provided on a connecting formation which is connectable to a filter body, and a second set of channels which is provided on a fluid transfer member.

The helical formations of the first and second sets of channels may correspond with one another.

The helical formations of the first and second sets of channels may have substantially the same pitch.

At least one of the channels may be a groove in an outer surface of the fluid transfer member.

The fluid displacer may further include at least one fin extending outwardly from an outer surface of the fluid displacer.

The or each fin may extend along at least a part of the length of the fluid displacer, and may also extend at least partially around a circumference of the fluid displacer, such that the or each fin is substantially helicoidal.

According to a third aspect of the invention, there is provided a filter of the first aspect of the invention including a fluid displacer of the second aspect of the invention.

Where at least one of the channels of the fluid displacer is provided in a helical formation, the helical formation of the or each channel of the fluid displacer may correspond with at least one helical formation provided in or on the body of the filter.

The filter may be a mud filter for an oil well drilling string.

According to a fourth aspect of the invention, there is provided a filter sub of an oil well drilling string, wherein the filter sub includes a tubular body, and at least one helical formation on an internal surface of the tubular body.

According to a fifth aspect of the invention, there is provided a filter apparatus including a filter in accordance with the first or third aspect on the invention, wherein the filter is housed in a filter sub according to the fourth aspect of the invention.

The or each helical formation of the tubular body of the filter sub may correspond with at least one helical formation of apertures of the filter body.

The pitch of the or each helical formation of the body of the filter sub may be substantially the same as the pitch of at least one helical formation of apertures of the filter body.

The filter may include at least one fin to maintain the filter body in position relative to the filter sub, and to inhibit at least one of bending, flexing, twisting and other movement of the filter body relative to the filter sub.

The or each fin may be provided on a fluid displacer of the filter.

Each aspect of the invention will now be described, by way of example only, with reference to the accompanying drawings, of which: FIGURE 1 is a perspective view of a prior art filter; FIGURE 2 is a perspective view of a filter head of the filter of Figure 1 FIGURE 3 is a perspective view of an alternative prior art filter; FIGURE 4 is a perspective view of a filter in accordance with at least a first aspect of the present invention, positioned within a filter sub; FIGURE 5 is an enlarged view of a part of a wall of the filter of Figure 3; FIGURE 6 is a perspective view of a fluid transfer member, in accordance with a further aspect of the present invention; and FIGURE 7 is a perspective view of a filter in accordance with at least a first aspect of the invention, positioned within a filter sub according to the fourth aspect of the invention.

With reference to Figure 4, there is shown a filter 210, of the type suitable for use as a mud filter in an oil well drilling string. The filter 210 shares a number of features with the prior art filter 10: shown in Figure 1 and described in detail above. Where the filter 210 of the present invention includes a feature which is similar to a corresponding feature of the prior art filter 10, the same reference numeral will be used, but with the addition of a 2' prefix.

The filter 210 is a slotted filter, having a filter head 212, a body 214 and a fluid displacer 216, hereinafter referred to as an internal mud displacer 216.

The body 214 is substantially cylindrical, having a first end 214a. a second end 214b, a body wall 215, and a longitudinal axis A. The body 214 is substantially tubular, having an opening 218 which is defined by the wall 215 and extends between the first end 214a and the second end 214b. Typically, the body 214 has an external diameter of between approximately 1 inch (25.4mm) and approximately 9 5/8 inches (244.48mm), depending upon the bore size of the drill string with which the filter 210 is intended to be used. It should be appreciated that the body 214 could be manufactured to other sizes based on a customer specification, and in compliance with the American Petroleum Institute (API) recommended drill string sizes. The wall 215 of the mud filter 210 is manufactured from pressed metal, preferably 4mm thick 304 stainless steel. It is also envisaged that the wall 215 may be manufactured from 17-4 PH stainless steel. It will be appreciated that other materials may be suitable.

It will also be appreciated that the wall 215 may be manufactured in alternative manner, for example being cast, rather than pressed.

A plurality of apertures 220 extend through the wall 215 of the body 214. Each aperture 220 in the example of the mud filter 210 is elongate, and has rounded ends. It will be appreciated that each aperture 220 need not have rounded ends, and may be alternative shapes.

Each aperture 220 extends in a substantially longitudinal direction along the body 214. However, it will be seen from Figure 4, in particular, that each aperture 220 also extends circumferentially around the body 214. Preferably, each aperture 220 does not extend parallel to the longitudinal axis A of the body.

The apertures 220 are arranged along substantially the whole length of the body 214, in a plurality of sections 220a, 220b, 220c, 220d. Each section 220a-d extends around substantially the whole circumference of the body 214.

It will be appreciated that the apertures 220 may be provided in any number of sections, including one substantially continuous section which extends along substantially the whole length of the body 214.

Each section 220a-d includes a plurality of rows of apertures 220, each row extending substantially longitudinally along the body 214, and being spaced circumferentially from adjacent rows. Each row contains a plurality of apertures 220 in a substantially longitudinally extending series. Since each aperture 220 is not aligned with the axis A, each row of apertures 220 curves at least partially around the circumference of the body 214. Each row provides a substantially helical formation at least partially around the circumference of the body 214. It will be appreciated that the number of rows of apertures 220 may vary, and may for example, be dependent upon the diameter of the body 214. It will be appreciated that a single row of apertures 220 may be provided in a single helical formation. It will also be appreciated that the length of each row of apertures 220 may vary, and that each helical formation may extend around the entire circumference of the body 214, rather than only partially around the circumference of the body. Each helical formation may extend more than once around the circumference of the body. The purpose of the helical formation(s) will be discussed in more detail below, but the pitch of each helical formation may be selected dependent upon a property of the mud to be filtered, for example its viscosity.

Apertures 220 having shapes different from that shown in Figure 4 may additionally or alternatively provided, and for one or more helical formations still to be presented.

The filter head 212 is substantially circular and provides a cap at the first end 214a of the body 214. The filter head 212 includes an opening, through which mud may pass, into the body 214.

The internal mud displacer 216 includes a connecting formation 222 which is connectable to the body 214, and a fluid transfer member 224. The connecting formation 222 of the present example is a boss 222. The boss 222 has a first end 222a and a second end 222b, and is receivable in the second end 214b of the body 214 to at least partially close the opening 218 at the second end 214b. The boss 222 includes a substantially axial opening 223 through which fluid (mud) may pass. The opening 223 is positioned substantially centrally in the boss 222.

The boss 222 is substantially conical, and includes a plurality of elongate grooves 226 which extend substantially axially along an outer surface of the boss 222, over at least a part of the length of the boss 222. In the embodiment shown in Figure 6, each of the grooves 226 is provided in a helical formation, with the pitch of each substantially helical groove 226 matching the pitch of each row of apertures 220. It will be appreciated that the grooves 226 may alternatively be provided straight', i.e. substantially parallel to the axis A. The fluid transfer member 224 is substantially circular in cross section, and has a diameter which is smaller than the bore of the drill string with which it is intended to be used. The fluid transfer member 224 includes an opening 225 through which fluid (mud) may pass. The opening 225 is positioned substantially centrally in the fluid transfer member 224. The fluid transfer member 224 also includes a plurality of elongate grooves or channels 228, each of which extends substantially axially along at least a part of the length of the fluid transfer member 224, along an outer surface thereof. Each groove 228 of the fluid transfer member 224 is in fluid communication with a groove 226 of the boss 222. Each groove 228 is substantially helical, with the pitch of each helical groove 228 corresponding to the pitch of the helical grooves 226 of the boss 222 and/or the pitch of the helical formation provided by each row of apertures 220. It will be appreciated that the grooves 228 may be provided straight', i.e. substantially aligned with the longitudinal axis A, rather than helical.

The internal mud displacer 216 shown in Figure 6 also includes a plurality of fins 230, each of which is connected to the outer surface of the fluid transfer member 224, and extends radially outwardly. The maximum radial extent of each fin 230 substantially corresponds with the inner diameter of the filter sub with which the filter 210 is intended to be used. The purpose of the fins 230 is to inhibit bending, flexing and/or other deviations of the mud filter 210 when it is in use within the drill string. In the embodiment shown in Figure 6, each fin 230 is attached to the fluid transfer member 224 such that it forms a helicoid which extends at least partially around the circumference of the fluid transfer member 224. The pitch of the helicoid provided by each fin 230 corresponds with the pitch of the helix provided by each row of apertures 220, and/or the helical grooves 226 and/or the helical grooves 228.

In the embodiment shown in Figure 7, the mud filter is positioned in a filter sub 240. The filter sub 240 is substantially tubular, and includes rifling on its inner surface. The rifling is provided by a series of helical grooves 242, the pitch of each of the helices corresponding with the pitch of the helical formation(s) of the apertures 220, and/or the grooves 226 in the boss 222, and/or the grooves 228 in the fluid transfer member 224, and/or each of the fins 230.

It will be appreciated that the mud filter 210 in accordance with the present invention may be provided with one or more, or all of the helical formations described above, and that whilst they are complimentary to one another, they are not mutually dependent.

The mud filter is preferably manufactured from pressed steel, for example 304 stainless steel, the apertures 220 being pressed into a blank 232. The blank is then rolled as shown in Figure 5, applying torsion to the blank 232 such that long edges 232a, 232b of the blank 232 meet one another along a joint 232c which is helical. It will be appreciated that other materials and manufacturing methods are possible, for example the body 214 may be cast and/or may be manufactured from 17-4 PH stainless steel.

In use, mud is receivable inside the filter body 214, and enters the filter body 214, via the opening 218 in the filter head 212. The mud is filtered by passing through the apertures 220, such that the mud is then positioned between the wall 215 of the body 214 and the internal surface of the filter sub in which the filter 210 is positioned, e.g. filter sub 240. The mud which passes through the apertures 220 is guided by the helical formations of the apertures 220 into a substantially vertical flow along and around the axis A. An amount of mud is also able to be filtered by passing through the opening 223 in the boss 222, and an amount of mud is also able to pass along the grooves 226 of the boss 222.

Both mud which has passed through the apertures 220 and mud which has passed along the grooves 226 of the boss 222 is in substantially vertical motion, and is able to flow along the grooves 228 of the fluid transfer member 224. Mud which has flowed through the opening in the boss 222 is able to flow through the opening in the fluid transfer member 224. Mud is also encouraged to move in vortical motion by the fins 230.

Causing the mud to move in substantially vortical motion enables the mud motor to be driven more effectively and/or efficiently by the mud. Since the mud is already moving in a vortical manner when it reaches the mud motor, the motor is required to do less work in urging the mud into substantially vortical motion in order to drive the drill bit.

In embodiments where rifling is provided on the inner surface of the filter sub 240, the rifling, also encourages the mud to move in a vortical manner, prior to reaching the mud motor.

When used in this specification and claims, the terms "comprises" and "comprising" and variations thereof mean that the specified features, steps or integers are included. The terms are not to be interpreted to exclude the presence of other features, steps or components.

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

CLAIMS1. A filter including a body having a plurality of apertures through which fluid is able to pass, to at least assist in the performance of filtration of the fluid, at least a proportion of the apertures being provided in a substantially helical formation along at least a part of the length of the body.
2. A filter according to claim 1 including a plurality of helical formations provided by the apertures.
3. A filter according to claim 1 or claim 2 including a plurality of rows of apertures, wherein at least one row of apertures is provided in a helical formation.
4. A filter according to any of the preceding claims wherein the filter is a mud filter for an oil well drilling string.
5. A fluid displacer for a filter, the fluid displacer including at least one channel along which fluid is capable of passing.
6. A fluid displacer according to claim 5, the fluid displacer including at least one channel along which fluid is capable of passing, the channel being provided in a helical formation.
7. A fluid displacer for a filter according to claim 5 or claim 6 including a plurality of channels, at least one of which is provided in a helical formation.
5. A fluid displacer according to any one of claims 5 to 7 including a first set of channels provided on a connecting formation which is connectable to a filter body, and a second set of channels which is provided on a fluid transfer member.
9. A fluid displacer according to claim 8 wherein the helical formations of the first and second sets of channels correspond with one another.
10. A fluid displacer according to claim 8 or 9 wherein the helical formations of the first and second sets of channels have substantially the same pitch.
11. A fluid displacer according to any of claims 5 to 10 wherein at least one of the channels is a groove in an outer surface of the fluid transfer member.
12. A fluid displacer according to any of claims 5 to 11 further including at least one fin extending outwardly from an outer surface of the fluid displacer.
13. A fluid displacer according to claim 12 wherein the or each fin extends along at least a part of the length of the fluid displacer, and also extends at least partially around a circumference of the fluid displacer, such that the fin is substantially helicoidal.
14. A fluid displacer substantially as disclosed herein and/or as shown in Figures 4 to 7.
15. A filter according to any of claims 1 to 4, further including a fluid displacer according to any of claims 6 to 14.
16. A filter according to claim 15 wherein the helical formation of the or each channel of the fluid displacer corresponds with at least one helical formation provided in or on the body of the filter.
17. A filter according to any one claims 1-4, 15 and 16, wherein the filter is a mud filter for an oil well drilling string.
18. A filter substantially as described herein and/or as shown in the Figures 4toT
19. A filter sub of an oil well drilling string, wherein the filter sub includes a tubular body, and at least one helical formation on an internal surface of the tubular body.
20. A filter sub substantially as described herein and/or as shown in Figures 4 to 7.
21. A filter apparatus including a filter in accordance with any of claims 1 to 4 and 15 to 18, wherein the filter is housed in a filter sub according to claim 19 or claim 20.
22. A filter apparatus according to claim 21 wherein the or each helical formation of the tubular body of the filter sub corresponds with at least one helical formation of apertures of the filter body.
23. A filter apparatus according to claim 21 or 22 wherein the pitch of the or each helical formation of the body of the filter sub is substantially the same as the pitch of at least one helical formation of apertures of the filter body.
24. A filter apparatus according to any of claims 21 to 23, wherein the filter includes at least one fin to maintain the filter body in position relative to the filter sub, and to inhibit at least one of bending, flexing, twisting and other movement of the filter body relative to the filter sub.
25. A filter apparatus according to claim 24 wherein the or each fin is provided on a fluid displacer of the filter.
26. A filter apparatus substantially as described herein and/or with reference to Figures 4 to 7.
27. Any novel feature or any novel combination of features substantially as described herein and/or as shown in the accompanying drawings.