WO2010037185A1

WO2010037185A1 - Drilling fluid treatment

Info

Publication number: WO2010037185A1
Application number: PCT/AU2009/001321
Authority: WO
Inventors: Ross Spanbroek; Dale Mcleod; John Roach
Original assignee: Australian Mud Company Ltd
Priority date: 2008-10-03
Filing date: 2009-10-05
Publication date: 2010-04-08

Abstract

The treatment system (10) for performing a classification process on drilling mud for removal of solids therefrom, thereby a controlling the solids content of the drilling mud. The classification process includes a screw classification stage, and a cyclone separation stage. The classification process also includes a settling classification stage. A lamella separation stage is optional. The treatment system (10) is incorporated into apparatus (11) which is adapted for location at the site of a drilling operation. The apparatus (11) is configured as a unit (13) which is adapted to be transported to the site of the drilling operation. The unit (13) is adapted to be transported to the site on a load-carrying vehicle and unloaded at the site. The unit (13) is then hydraulically coupled 13 to a drilling rig operating at the site. The unit (13) treats drilling mud used by the drilling rig to control the solids content thereof and to also manage the fluid property of the drilling mud.

Description

Drllling Fluid Treatment

Field of the Invention

This invention relates to the treatment of fluids having particles suspended therein to remove solids therefrom.

Not all solids need necessarily be removed from the fluid undergoing treatment; rather, in certain applications only some of the solids may be removed so as to control the solids content of the fluid.

The invention has been devised particularly, although not solely, for treatment of drilling mud to control the content of solids therein.

Background Art

The following discussion of the background art is intended to facilitate an understanding of the present invention only. The discussion is not an acknowledgement or admission that any of the material referred to is or was part of the common general knowledge as at the priority date of the application.

In borehole drilling operations, drilling fluid (commonly referred to a drilling mud) is used for cleaning and cooling a drill bit during the drilling process and for conveying drilling cuttings to the ground surface.

A mud system is provided for circulating the drilling mud during the drilling operation and for removing drill cuttings from the drilling mud to control the solids content thereof. The mud system typically includes mud pits from which drilling mud is pumped to the drill string of a drilling rig and to which the drilling mud is returned from the drill string. Prior to returning to the mud pits, the drilling mud is filtered for the purposes of controlling the solids content thereof. Solids control is important in maintaining the drilling mud in a condition suitable for use in the drilling process. The present invention seeks to provide a system and method for controlling solids content of the drilling mud.

Disclosure of the Invention

According to a first aspect of the invention there is provided a solids control system for drilling mud comprising a fluid flow path for conveying drilling mud therealong, the fluid flow path incorporating a separation device for removal of solids from the fluid, the separation device comprising a hydrocyclone.

Preferably, the fluid flow path also incorporates a screw classifier.

The fluid flow path may also incorporate a lamella plate classifier.

Preferably the fluid flow path also incorporates a settling classifier.

Preferably, the solids control system is configured to deliver fluid from the screw classifier to a tank from which fluid is delivered to the hydrocylcone..

The tank may comprise one of a series of tanks for receiving fluid. One or more of the tanks may be configured as a settling classifier.

The underflow of the hydrocyclone may be adapted to return at least some of the extracted solids to the screw classifier.

According to a second aspect of the invention there is provided a solids control system for drilling mud comprising a screw classifier, a hydrocyclone and a tank, the screw classifier being adapted to receive the drilling mud and subject it to screw classification, the tank being adapted to receive fluid after the screw classification, and the hydrocyclone being adapted to receive fluid from the tank.

The overflow of the hydrocyclone may communicate with the tank or with another tank which is in communication with the tank.

The underflow of the hydrocyclone may communicate with the screw classifier. According to a third aspect of the invention there is provided apparatus incorporating a solids control system in accordance with the first or second aspect of the invention.

Preferably the apparatus is configured for transportation as a as a unit to the site of the drilling operation.

The unit may be adapted to be transported to the site on a load-carrying vehicle and unloaded at the site.

Preferably, the apparatus comprises a base structure and an upper structure which is mounted on the base structure and which incorporates the treatment system.

The base structure may comprise a base frame and a walkway to provide access around the upper structure.

Preferably, the base structure is constructed to facilitate the loading and unloading operations with respect to the load-carrying vehicle.

The base structure may have a collapsed condition for transportation of the unit and an erected condition when the unit is installed for operation at the site of the drilling operation.

According to a fourth aspect of the invention there is provided a method of treating drilling mud using a system in accordance with the first or second aspect of the invention.

According to a fifth aspect of the invention there is provided a method of treating a drilling mud to control the solids content thereof using apparatus in accordance with the third aspect of the invention.

According to a sixth aspect of the invention there is provided a method of treating drilling mud to remove solids therefrom, th© method comprising subjecting the drilling mud to screw classification for removal of solids therefom, transferring the drilling mud after screw classification to a tank, and extracting at least some of the drilling mud from the tank and subjecting rt to cyclonic separation.

The method may further comprise returning at least some of the solids extracted by the cyclonic separation to drilling mud undergoing screw classification.

The method may further comprise returning at least some of the drilling mud after the cyclonic separation to the tank or to another tank in communication with the tank..

According to a seventh aspect of the invention there is provided apparatus for treating a fluid to remove solids therefrom, the apparatus comprising a screw classifier, a hydrαcydone, and a tank, the screw classifier being adapted to receive the fluid and subject it to screw classification, the tank being adapted to receive fluid after the screw classification, and the hydrocyelone being adapted to receive fluid from the tank.

According to a eighth aspect of the invention there is provided a method of treating a fluid to remove solids therefrom, the method comprising subjecting the fluid to screw classification for removal of solids therefpm, transferring the fluid after screw classification to a tank, and extracting at least some of the fluid from the tank and subjecting it to cyclonic separation.

The method may further comprise returning at least some of the solids extracted by the cyclonic separation to fluid undergoing screw classification.

The method may further comprise returning at least some of the fluid after the cyclonic separation to the tank or to another tank in communication with the tank..

According to an ninth aspect of the invention there is provided a method of controlling the solids content of drilling mud, the method comprising causing the drilling mud to flow along a flow path and subjecting the drilling mud to a centrifugal separation process to remove solids therefrom.

According to a tenth aspect of the invention there is provided a treatment system comprising a fluid flow path for conveying therealong a fluid having solids suspended therein, the fluid flow path incorporating a separation device for removal of solids from the fluid, the flow path having a suction section being adapted for communication with a surplus volume of the fluid.

According to an eleventh aspect of the invention there Is provided a solids control unit for drilling mud, comprising a structure defining a treatment reservoir and a storage reservoir, an inlet line having an entry end adapted to receive drilling mud for treatment to remove solids therefrom, a fluid pump for conveying the drilling mud from the inlet line to a hydrocyclone at which the drilling mud is treated to remove solids therefrom, the hydrocyclone having an underflow for discharging solids removed from the drilling mud and an overflow from which the treated drilling mud is conveyed to the storage reservoir.

Preferably, the inlet line opens onto the interior of the treatment reservoir for communication with surplus drilling mud contained therein and the inlet line also has an entry end above the level of surplus drilling mud contained within the treatment reservoir.

Preferably, a fluid pump is incorporated in the flow path between the suction . section thereof and the separation device, the arrangement being that the fluid pump is adapted to draw fluid along the suction section of the flow path and deliver it to the separation device.

In the event that there is insufficient fluid flow along the flow path to satisfy the demand of the fluid pump, supplementary fluid can be drawn into the flow path from the surplus volume. This reduces the likelihood of the^' fluid pump being exposed to a "running dry" condition in which it could be vulnerable to damage.

Preferably, the separation device comprises a hydrocyclone. The separation device may comprise one or more further hydrocyclones.

Where there is a plurality of hydrocyclones, they may communicate with a common manifold incorporated in the fluid flow path.

Preferably, the system includes a treatment reservoir for containing the surplus volume of the fluid and the flow path includes an inlet line in communication with the interior of the reservoir to provide the communication with the surplus, fluid. The inlet line may have a port formed in the side thereof opening onto the interior of the treatment reservoir to provide said communication with the interior of the reservoir.

Preferably, the flow path further includes a delivery line for delivering the fluid to the inlet line, the inlet line having an entry end above the level of fluid contained within the reservoir.

The communication between the outlet end of the delivery line and the entry end of the inlet line may be so configured that excess fluid can spill over into the reservoir.

Preferably, the inlet line has an outlet end communicating with the fluid pump which delivers fluid from the inlet line to the separation device.

Preferably, the separation device incorporates a by-pass system whereby in an over-pressure condition some fluid can be diverted to the entry end of the inlet line.

Preferably the fluid flow path delivers the treated fluid (being the fluid after removal of solids therefrom at the separation device) to a storage reservoir from which the treated fluid can be oumped to a drill string.

The system may incorporate a replenishment reservoir containing, a supply of replenishment fluid for replenishing fluid contained in the storage reservoir as necessary.

The treatment reservoir, the storage reservoir and the replenishment reservoir may be incorporated in an integral structure. Typically, the integral structure defines an internal volume partitioned into three separate sections respectively defining the treatment, storage and replenishment reservoirs.

The integral structure may incorporate the separation device, the fluid pump,, and also associated plumbing, such that the assembly may be transported and installed as a unit According to a twelfth aspect of the invention there is provided a solids control unit for drilling mud comprising a fluid flow path for conveying drilling mud therealong, a treatment reservoir for containing a surplus volume of drilling mud, an inlet line forming part of the flow path, the inlet line opening onto the interior of the treatment reservoir for communication with surplus drilling mud contained therein and haying an entry end above the level of surplus drilling mud contained within the reservoir, and a hydrocyclone in the fluid flow path for removal of solids from the drilling mud, the hydrocyclone being adapted to receive drilling mud from the inlet line.

Preferably, the solids control further includes a storage reservoir into which the treated drilling mud is delivered.

Preferably, the solids control still further includes a replenishment reservoir containing a supply of replenishment fluid for replenishing fluid contained in the storage reservoir as necessary.

According to a thirteenth aspect of the invention there is provided a method of treating a fluid using a system in accordance with the first aspect of the invention.

According to a fourteenth aspect of the invention there is provided a method of treating a drilling mud to control the solids content thereof using a solids control unit in accordance with the second aspect of the invention.

According to a fifteenth aspect of the invention there is provided a method of treating a fluid to remove solids therefrom, the method comprising causing the fluid to flow along a flow path and delivering the fluid to a separation device at which solids are removed from the fluid, and exposing the fluid flow to surplus fluid at a suction section of the of the flow path prior to delivery to the separation device.

Preferably, the method further comprises pumping the fluid from the suction section of the flow path to the separation device, whereby the fluid is drawn along the suction section and delivered to the separation device. According to a sixteenth aspect of the invention there is provided a method of controlling the solids content of drilling mud, the method comprising causing the drilling mud to flow along a flow path, exposing the drilling mυd flowing along the flow path to surplus drilling mud at a suction section of the of the flow path, and subjecting the drilling mud to a centrifugal separation process to remove solids therefrom.

According to a seventeenth aspect of the invention there is provided a sdlids control system for drilling mud comprising a fluid flow path for conveying drilling mud therealong, the fluid flow path incorporating a separation device for removal of solids from the fluid, the separation device comprising a hydrocyclone.

According to an eighteenth aspect of the invention there is provided a method of controlling the solids content of drilling mud, the method comprising causing the drilling mud to flow along a flow path and subjecting the drilling mud to a centrifugal separation process to remove solids therefrom.

According to a nineteenth aspect of the invention there is provided a solids control unit for drilling mud, comprising a structure defining a treatment reservoir and a storage reservoir, an inlet line having an entry end adapted to receive drilling mud for treatment to remove solids therefrom, a fluid pump for conveying the drilling mud from the inlet line to a hydrocyclone at which the drilling mud is treated to remove solids therefrom, the hydrocyclone having an underflow for discharging solids removed from the drilling mud and an overflow from which the treated drilling mud is conveyed to the storage reservoir.

Preferably, the inlet line opens onto the interior of the treatment reservoir for communication- with surplus drilling mud contained therein and the inlet line also has an entry end above the level of surplus drilling mud contained within the treatment reservoir. Brl&f Description of the Drawings

The invention will be better understood by reference to the following description of one specific embodiment thereof as shown in the accompanying drawings in which:-

Figure 1 is a schematic perspective view from above of a transportable treatment unit incorporating a transport system according to a first embodiment;

Figure 2 is a further perspective view of the unit from the other side thereof;

Figure 3 is a further perspective view of the treatment unit;

Figure 4 is an elevatioπal view of one side of the treatment unit;

Figure 5 is a view of the other side of the treatment unit;

Figure 6 is a plan view of the treatment unit;

Figure 7 is an elevational view of one end of the treatment unit;

Figure S is a perspective view from the underside of the treatment unit;

Figure 9 is fragmentary perspective view illustrating a screw classifier and two hydrocyclones forming part of the treatment unit;

Figure 10 is a further fragmentary perspective view illustrating the screw classifier and the hydrocyclones;

Figure 11 is a is a further fragmentary perspective view illustrating the screw classifier and the hydrocyclones;

Figure 12 is a perspective view of a base structure forming part of the treatment unit;

Figure 13 is an end view of the base structure; Figure 14 is a perspective view of the base structure forming part of the treatment unit; with one walkway section shown in an erected condition and the other shown in a collapsed condition;

Figure 15 is a fragmentary perspective view of the base structure, shown with the deck sections removed;

Figures 16 to 22 are a series of schematic views illustrating installation of the treatment unit at a site at which a drilling operation is to be performed;

Figure 23 is a schematic perspective view of a treatment unit incorporating a treatment system according to a second embodiment; and

Figure 24 is a schematic view of a treatment system according to a third embodiment.

Best Mode(s) for Carrying Out the Invention

Referring to Figures 1 to 22 of the drawings, there is shown a treatment system 10 for treating drilling mud to control the solids content thereof and also manage the fluid property of the drilling mud to maintain the drilling mud in a condition suitable for use in a borehole drilling operation.

The treatment system 10 according to the first embodiment is incorporated into apparatus 11 which is adapted for location at the site of the drilling operation. The apparatus 11 is configured as a unit 13 which is adapted to be transported to the site of the drilling operation. In this embodiment, the unit 13 is adapted to be transported to the site on a load-carrying vehicle and unloaded at the site, as will be described in detail later. Other arrangements are, of course possible; for example, the unit 13 could be mounted on a trailer or a skid-arrangement.

The treatment system 10 performs a classification process on the drilling mud for removal of solids therefrom, thereby a controlling the solids content of the drilling mud. The classification process includes a screw classification stage and a cyclone separation stage. The classification process also includes a settling classification stage. A lamella separation stage is optional but is not included in this embodiment.

The apparatus 11 comprises a base structure 15 and ari upper structure 17 which is mounted on the base structure 15 and which incorporates the treatment system 10.

The base structure 15 comprises a base frame 21 and a walkway 23 to provide access around the upper structure 17.

The upper structure 17 comprises a screw classifier 25 for the screw classification stage, one or more hydrocyclones 27 for the cyclone separation stage and a tank structure 29 for the settling classification stage. In the arrangement shown, there are two hydrocyclones 27.

The tank structure 29 is configured to define three tank units 31 , 32 and 33 in side-by side relation. Tank units 31 and 32 are separated by a common wall 34, and tank units 32 and 33 are separated by a common wall 36. Tank units 32 and 33 each have a bottom wall 35 which tapers inwardly and downwardly to define a bottom channel 37.

Tank unit 32 has an internal wall 38, and tank unit 33 has an internal wall 39.

Tank unit 31 defines a first tank 41. Tank unit 32 is divided by internal wall 38 to define a second tank 42 and a third tank 43. The internal wall 38 is configured to provide a weir over which fluid in second tank 42 can flow into third tank 43. Similarly, tank unit 33 is divided by internal wail 39 to define a fourth tank 44 and a fifth tank 45. The internal wall 39 is configured to provide a weir over which fluid in fourth tank 44 can flow into fifth tank 45.

The screw classifier 25 is accommodated in first tank 41 and is of conventional construction, comprising an inclined trough 51 and a rotatable screw 53 within the trough 51. The screw 53 comprises a screw flight 55 mounted on a screw shaft 57 rotatably supported in bearings. The arrangement is such that the screw flight 55 is so supported that it does not contact the trough 51. A drive unit 59 is provided at one end of the screw shaft 57 for rotating the screw 53. In this embodiment, the rotational speed of the screw 53 is about 4rpm. In the arrangement illustrated, the screw flight 55 is configured as a double flightscrew.

In this embodiment, screw classification is the first stage of the classification process to control the solids content of the drilling mud. Drilling mud for treatment is delivered to the upper end of the screw classifier 25 and flows downwardly along the trough 51. Heavier solid particles within the drilling mud settle under the influence of gravity and are conveyed upwardly within the trough 51 by the screw 53 for discharge at the upper end- Typically, the separated solids am discharged from the upper end of the screw classifier 25 onto the ground or into a discharge bin..

The moving mass of solids being conveyed along the trough 51 of the screw classifier 25 also serves to capture some of the smaller solids in the fluid.

Excess fluid in first tank 41 overflows into second tank unit 42. Excess fluid in second tank 42 overflows the weir defined by internal wall 38 into third tank 43. Excess fluid in third tank 43 overflows into fourth tank unit 44. Excess fluid in fourth tank 44 overflows the weir defined by internal wall 39 into fifth tank 45.

Third tank 43 has a suction outlet pipe 61 extending to the exterior of the tank structure 29 and terminating at a valve 63. Similarly, fourth tank 44 has a suction outlet pipe 62 extending to the exterior of the tank structure 29 and terminating at a valve 63. ^"

As mentioned above, the hydrocylones 27 provide the cyclone separation stage, treating the drilling mud by removing solids therefrom through centrifugal separation. The hydrαcyclone 27 receive fluid for treatment from one or more of the tanks in the tank structure 29 and returns the treated fluid to one or more of the tanks in the tank structure. In this embodiment, the hydrocyclones 27 receive fluid pumped from the bottom of one or both of the second and third tanks 42, 43 and return the treated fluid to one or both of those tanks. Each hydrocyclone 27 has inlet 71 through which fluid is received for treatment, an underflow 73 through which separated solids are discharged, and an overflow 75 through which the treated fluid is delivered to one or more of the tanks.

The fluid for treatment is delivered to the inlet 71 by being pumped thereto by a pump 79.

The separated solids discharging from the underflow 73 can be handled in several ways. In the arrangement illustrated, the separated solids are returned to the screw classifier 25. This is achieved by positioning the underflow 73 above the trough 51 of the screw classifier 25, as best seen in Figures 9, 10 and 11. In another arrangement, the separated solids may be discarded, suoh as to ground or into a discharge bin.

As mentioned, in the arrangement illustrated, the separated solids are returned to the screw classifier 25. This is done because removal of the heavy cuttings can exhaust excess fluid which may be required to remain in the system. Positioning the underflow 73 to return the extracted solids into the treatment system 10 allows the solids to be removed as a damp substance via the screw classifier 25 rather than in a more fluid state.

Settling classification can occurs in the second tank 42 and the third tank 43.

The drilling mud is returned to the drilling rig after treatment from either or both of the fourth and fifth tanks 44, 45_» according to the specific propertiøs required of the drilling mud for the drilling operation.. Replenishment drilling fluid, and any necessary additives, can be mixed with the circulating drilling mud in the fourth and fifth tanks 44, 45, according to the specific properties required of the drilling mud for the drilling operation.

As mentioned previously, the unit 13 is adapted to be transported to the site of the drilling operation on a load-carrying vehicle and off-loaded at the site. The base structure 15 is constructed to facilitate the loading and unloading operations. Further, the base structure 15 has a collapsed condition for transportation of the unit 13 and an erected condition when the unit is installed for operation at the site of the drilling operation.

The base structure 15 comprises the base frame 21 and the walkway 23 to provide access around the upper structure 17. The base frame 21 comprises a chassis 110 having two longitudinal beams 111 and crossbeams 113 extending therebetween.

The chassis 110 is adapted for movement between raised and lowered conditions. In the raised condition, the chassis 110 is elevated in relation to the ground to allow loading and unloading of the unit with respect to a load-carrying vehicle, as will be descried in more detail later. In the lowered condition, the chassis 110 rests on the ground to support the unit 13 in a stable manner for operation at the site of the drilling operation.

A jacking system 120 is provided for raising and lowering the chassis 110. In this embodiment, the jacking system 120 comprises a plurality of jacking legs 121. In the arrangement shown there are four jacking legs 121 , two to each side of the chassis 110. Each jacking leg 121 is of telescopic construction, comprising an upper leg section 123 attached to the chassis 110 and a lower leg section 125 adapted for extension and retraction with respect to the upper leg section 123. A power device 127 (such as a hydraulic ram) is connected between the two leg sections 123, 125 for causing extension and contraction of the lower leg section. The lower leg section 125 has a pad 129 on Us lower end for engagement with the ground.

The jacking legs 121 are each also rnαveable laterally between an outwardly and inwardly disposed positions with respect to the sides of the chassis 110. In the outwardly disposed position, each jacking leg 121 is spaced from the adjacent side of the chassis 110, the purpose of which will be explained later. In the inwardly disposed position, each jacking leg 121 is located close to the adjacent side of the chassis 110. To facilitate lateral movement of the jacking legs 121 laterally between an outwardly and inwardly disposed positions with respect to the sides of the chassis 110, the upper leg section 123 of each jacking leg 121 is mounted on a lateral beam (not shown) adapted for extension and retraction with respect to the adjacent side of the^' chassis 110. A power device 133 (such as a hydraulic ram) is provided for causing extension and contraction of the lateral beam.

The walkway 23, which provides access around the upper structure 17, comprises a side walkway 141 along each side of the chassis 110. Each side walkway 141 comprises a deck 143 and handrail 145.

The side walkways 141 have collapsed and erected conditions, corresponding to the collapsed and erected conditions of the base structure 15. In this regard, each side walkway 141 is constructed in walkway sections 147 (as shown in Figures 12 to 15), there being two such sections in the arrangement disclosed. In Figures 13 and 14, walkway section 147a is depicted in the erected condition and walkway section 147b is depicted in the collapsed condition

Each walkway section 147 comprises an outer beam 151 disposed in parallel relation to the adjacent longitudinal beam 111 of the chassis 110, and a plurality of spaced swing arms 153 extending between the two beams 111,151. One end of each swing arm 153 is connected to the longitudinal beam 111 of the chassis 110 for pivotal movement about a vertical axis and the other end Is connected to the outer beam 151 for pivotal movement about a vertical axis. With this arrangement, the swing arms 153 can swing through a generally horizontal plane between retracted and extended conditions to move the outer beam 151 between outermost and innermost positions. In the innermost position, the outer beam 151 lies alongside the longitudinal beam 111 of the chassis 110.

The hand rail 145 is constructed in handrail sections 155 mounted on the outer beam 151. Additionally, the deck 143 is constructed in deck sections 157, each pivotally mounted on one of the outer beams 151 for movement between a raised position in which it is pivoted upwardly into a vertical disposition to rest alongside the handrail section 155 (as depicted by deck section 157b in Figure 14), and lowered position in which it rests on the extended swing arms 153 to provide a walkway surface (as depicted by deck section 157a in Figure 14). The walkway sections 147 have support legs 161which are operable when the walkway 23 is in the erected condition to engage the ground and provide load support.

Delivery and installation of the unit 13 at the site of the drilling operation will now be described with reference to Figures 16 to 22 of the drawings.

Referring to Figure 16, the unit 13 is delivered to the site by a vehicle 170 such as truck having a load-carrying bed 171 on which the unit is loaded. When loaded on the vehicle 170, the unit 13 is in the collapsed condition, with the side walkways 141 in the collapsed, the jacking legs 121 disposed inwardly and located close to the adjacent side of the chassis^' 110, and the lower leg sections 125 retracted. The vehicle 170 is manoeuvred to position the unit 13 at the desired location. Installation of the unit 13 can then commence.

First, the swing arms 153 are swung outward to move the outer beam 151 of each walkway section 147 to the outermost position. This is illustrated in Figure 17.

The lateral beams (not shown) are then extended to move the jacking legs 121 from their inwardly disposed positions close to the adjacent side of the chassis 110 into their outwardly disposed positions, as shown in Figure18. The reason for moving the jacking legs 121 into their outwardly disposed positions is to provide adequate clearance from the sides of the vehicle 170.

The jacking legs 121 are then actuated to extend the lower leg sections 125 and cause them to descend into engagement with the ground, also as shown in Figure 18.

Continued extension of the lower leg sections 125 then elevates the chassis 110 and raises it above the load-carrying bed 171 of the vehicle 170. At this stage, the jacking legs 121 fully support the unit 13 and thereby allow the vehicle 170 to be removed, as shown in Figure 19.

The lower leg sections 125 of the jacking legs 121 are retracted to lower the chassis 110 into engagement with the ground, as shown in Figure 20. At this stage, the load of the unit 13 is borne by the chassis 110 in engagement with the ground.

The jacking legs 121 no longer support the unit 13. The lateral beams 131 are then be retracted to move the jacking legs 121 from their outwardly disposed positions to their inwardly disposed positions close to the adjacent side of the chassis 110, as shown in Figure 21 ,

The deck sections 157 can then be folded downwardly from their raised positions to rest on the extended swing arms 153 to thereby provide the walkway deck 143. The deck sections 157 are shown partly folded down in Figure 21 and fully down in Figure 22. .

At this stage, installation of the unit 13 at the site is complete. It is then necessary to hydraulically couple the unit 13 to the drilling rig as necessary in order to perform the intended treatment process on drilling mud used by the drilling rig to control the solids content thereof and to also manage the fluid properly of the drilling mud.

Referring now to Figure 22, there is shown a unit 13 for a treatment system according to a $econd embodiment. The unit 13 is similar to unit 13 of the first embodiment and so corresponding reference numerals are used to identify corresponding parts.

In this second embodiment, the unit 13 includes lamella classification as the second stage- of the classification process to control the solids content of the drilling mud. .

The lamella classification is performed by a lamella classifier 150 incorporated in the unit 13.

The drilling mud flows from the screw classifier 25 to the lamella classifier 150 which is of conventional construction, comprising a rack of inclined settling plates 151 . which are adapted to undergo vibration. The drilling mud flows over the plates 151 and the vibration thereof causes further separation of solids from the fluid. The fluid can then be returned to the screw classifier 25 and the process repeated. Alternatively, the fluid can flow into the second tank 42.

Referring now to Figures 24, there is shown a treatment system 210 according to a third embodiment.

In this third embodiment, drilling mud is circulated through a mud system which incorporates a pit 213 to which the mud is returned after passing through the drill string of a drilling rig. The drilling mud cleans and cools the drill bit in the drilling process and carries cuttings upwardly along the annular space between the drill string and the sides of the borehole to emerge at the surface and be returned to the pit 213. From the pit 213, the drilling mud is conveyed along a flow path 215 for treatment in the treatment system 210 to. control the solids content of the drilling mud before being available for return to the drill string.

The flow path 215 includes a delivery line 219 along which the drilling mud is pumped from the pit 213 by a pump 221 within the pit. In this embodiment, the pump 221 comprises a hydraulic turbo pump.

^ The treatment system 210 further comprises an integral structure 223 defining an internal volume 225 divided into three sections which respectively define a treatment reservoir 227, a storage reservoir 229 and a replenishment reservoir (not shown). In the arrangement shown, the integral structure 223 is configured as an open-topped bin 230 having an exterior side wall 231 with internal partitions to divide the interior of the bin into the three sections. The particular internal partition 232 separating the treatment reservoir 227 and the storage reservoir 229 can be seen in the drawing.

The treatment reservoir 27 accommodates an inlet line 233 which also forms part of the flow path 213. The inlet line 233 extends through the exterior side wall 231 of the bin 230 at the lower section of the side wall. With this arrangement, the inlet line 233 comprises an inner portion 235 within the treatment reservoir 227 and an outer portion 236 on the exterior of the treatment reservoir. The inner portion 235 extends upwardly within the treatment reservoir 227 and terminates at an entry end 237 disposed above the treatment reservoir 227. With this arrangement, the entry end 237 is located above the level of surplus drilling mud contained within the treatment reservoir 227. A strainer 39 is incorporated within the inner portion 235 of the intet line 233 at a location below the entry end 237. The inner portion 235 of the inlet line 233 is configured to flare outwardly in the upward direction to present a relatively wide mouth 241 at the entry end 237, as shown in the drawings. With this arrangement, in the event that drilling mud discharges from the delivery line 219 at a rate in excess of that which can be handled in the inlet line 33, then the excess drilling mud can spill from the entry end 237 into the treatment reservoir 227. .

The delivery line 2219 extends into the mouth 241 of the inlet line 233 such that drilling mud conveyed along the delivery line discharges into the inlet line 233 at the open entry end 237. The incoming drilling mud is strained by strainer 239 before flowing further down the inner portion 235 of the inlet line 233.

The inner portion 235 of the inlet line 233 is configured to communicate with the interior of the treatment reservoir 227. In the arrangement illustrated, the inner portion 235 incorporates an annular port 243 communicating with the interior of the treatment reservoir 227. The annular port 243 is defined by a gap 245 within the inner portion 235 of the inlet line 233. The gap 245 can be created by forming the inner portion 235 into two sections, being an upper section 247 and a lower section 249 in spaced apart relationship to define the gap 245 therebetween.

The port 243 establishes a volume of surplus drilling mud within the treatment reservoir 227, the purpose of which will be explained later.

The outer portion 236 of the inlet line 233 is connected to a discharge pump 251 which is mounted on the bin 230 and which is operable to convey drilling mud along a further delivery line 53 to a treatment device 255 at which solids are removed from the drilling mud. The further delivery line 253 also forms part of the flow path 213. The treatment device 255 comprises two hydrocyclones 261 coupled to a manifold 263 having an inlet end 265 to which the further delivery line 253 is connected. The two hydrocyclones 261 each receive drilling mud from the manifold 263 and operate to treat the drilling mud by removing solids therefrom through centrifugal separation. Each hydrocyclone 261 has an underflow 271 through which separated solids are discharged into a collection device 273, and an overflow 275 through which the treated drilling mud is delivered to a return line 277 communicating with the storage reservoir 229, whereby the treated drilling mud is delivered to the storage reservoir from where it can be recirculated to the drill string as necessary. The replenishment reservoir (not shown) contains a supply of replenishment drilling mud for periodically replenishing the drilling mud supply within the storage reservoir 229 as necessary.

The manifold 263 incorporates a by-pass mechanism 281, responsive to an overpressure condition within the manifold to allow excess drilling mud to be discharged through a by-pass line 283 into the open entry end 237 of the inlet line 233 for retreatment. In this way, by-passed fluid is returned for retreatment. The manifold also incorporates a pressure gauge 289 for monitoring of the operating pressure thereof.

The treatment reservoir 227 contains a volume of drilling mud which communicates with the flow path 213 at the inlet line 233 by way of the annular port 243 therein. With this arrangement, fluid (drilling mud) within the inlet line 233 can equalise with fluid (drilling mud) contained within the treatment reservoir 227.

This feature is important in that it ensures that there is a supply of surplus drilling mud available to prevent the discharge pump 251 from running dry in circumstances where there is an inadequate or an interrupted flow of drilling mud along the flow path 213, and in particular along the inlet line 233.

The treatment system 210 according to this embodiment is of compact construction and relatively easy to install at sites where a drill rig is to operate and in so doing require a mud system offering control of the solids content of the drilling mud. The integral structure 223 in effect comprises an assembly which incorporates not only the three reservoirs but also carries the discharge pump 251 , the treatment device 255 incorporating the two hydrocyclones 261 , and associated plumbing including the inlet line 233, the further delivery line 53 and the return lines 277. With this arrangement, the assembly can be transported as a unit, All that is required to install the treatment system 210.is to locate the integral structure 223 at the desired location, establish the pit 213, install the pump 221 within the pit 213, and then install the delivery line 219 between the pump 221 and the entry end 237 of the inlet line 233- Drilling mud from the drilling operation can be pumped into the pit 213 from where it can pass through the treatment system 210

^• according to this embodiment for control of the solids content of the drilling mud.

The treated drilling mud is stored in the storage reservoir 229 within the integral structure 223 from where is can be drawn as required for recirculation to the drill string of the drilling rig.

It is believed that the hydrocyclones 261 within the treatment system should remove solids in the drilling mud of a size exceeding about 20 to 30 microns and it is envisaged that separation of solids down to about 15 microns would be achievable.

In a variation to the treatment system 210 according to the third embodiment, the drilling mud for treatment can be delivered directly to the integral structure 223 from the drilling rig, rather than via the pit 213.

From the foregoing, it is evident that the treatment system according to each embodiment provides a simple yet a highly effective arrangement for controlling the solids content of drilling mud, utilising hydrocyclones for the separation process.

While the embodiments have been described in relation to an arrangement using two hydrocyclones, it should be appreciated that other arrangements are possible, including an arrangement using only one hydrocyclone and arrangements using more than two hydrocyclones. It should also be appreciated that the treatment system and method according to the invention need not be limited to solids control in drilling mud and may find application in treatment of other liquids having solids entrained therein.

Modifications and improvements may be made without departing from the scope of the invention.

Throughout the specification and claims, unless the context requires otherwise, the word "comprise" or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

Claims

- 1 -The Claim Defining the Invention is as Follows:

1. A solids control system for drilling mud comprising . a fluid flow path for^' conveying drilling mud therealong, the fluid flow path incorporating a separation device for removal of solids from the fluid, the separation device comprising a hydrocyclone.

2. The solids control system according to claim 1 wherein the fluid flow path also . incorporates a screw classifier,

3, The solids control system according to claim 1 or 2 wherein fluid flow path also incorporates a lamella plate classifier.

4. The solids control system according to claim 1, 2 or 3 wherein the fluid flow path also incorporates a settling classifier.

5. The solids control system according to any one of the preceding claims wherein configured to deliver fluid from the screw classifier to a tank from which fluid is delivered to the hydrocylcone..

6. The solids control system according to claim 5 wherein the tank comprises one of a series of tanks for receiving fluid.

7. The solids control system according to claim 6 wherein one or more of the tanks are configured as a settling classifier.

8. The solids control system according to any one of the preceding claims wherein underflow of the hydrocyclone is adapted to return at least some of the extracted solids to the screw classifier.

9. A solids control system for drilling mud comprising a screw classifier, a hydrocyclone and a tank, the screw classifier being adapted to receive the drilling mud and subject it tp screw classification, the tank being adapted to - 2 - receive fluid after the screw classification, and the hydrocycløne being adapted to receive fluid from the tank.

10-The solids control system according to claim 9 wherein the overflow of the hydrocyclone is adapted to communicate with the tank or with another tank which is in communication with the tank.

11.The solids control system according to claim 9 or 10 wherein the underflow of the hydrocyclonβ is adapted to communicate with the screw classifier.

12. Apparatus incorporating a solids control system according to any one of the preceding claims.

13. Apparatus according to claim 12 configured for transportation as a as a unit to the site of the drilling operation.

14.Apparatus according to claim 12 or 13 wherein the unit is adapted to be transported to a site of intended use on a load-carrying vehicle and unloaded at the site.

15.Apparatus according to claim 12, 13 or 14 further comprising a base structure and an upper structure which is mounted on the base structure and which incorporates the treatment system.

16.Apparatus according to claim 15 wherein the base structure comprises a base frame and a walkway to provide access around the upper structure.

17.Apparatus according to claim 15 or 16 wherein the base structure is constructed to facilitate the loading and unloading operations with respect to the load-carrying vehicle.

18.Apparatus according to any one of claims 14 to 17 having a collapsed condition for transportation of the unit and an erected condition when the unit is installed for operation at the site. - 3 -

19.A method of treating drilling mud using a system according to any one of claims 1 to 11.

20.A method of treating a drilling mud to control the solids content thereof using apparatus according to any on© of claims 12 to 18.

21. A method of treating drilling mud to remove solids therefrom, the method comprising subjecting the drilling mud to screw classification for removal of solids therefom, transferring the drilling mud after screw classification to a tank, and extracting at least some of the drilling mud from the tank and subjecting it to cyclonic separation.

22.The method according to claim 21 further comprising returning at least some of the solids extracted by the cyclonic separation to drilling mud undergoing screw classification.

23.The method according to claim 21 or 22 further comprising returning at least some of the drilling mud after the cyclonic separation to the tank or to another tank in communication with the tank..

24-Apparatus for treating a fluid to remove solids therefrom, the apparatus comprising a screw classifier, a hydrocyclone, and a tank, the screw classifier being adapted to receive the fluid and subject it to screw classification, the tank being adapted to receive fluid after the screw classification, and the hydrocyclone being adapted to receive fluid from the tank.

25.A method of treating a fluid to remove solids therefrom, the method comprising subjecting the fluid to screw classification for removal of solids therefom, transferring the fluid after screw classification to a tank, and extracting at least some of the fluid from the tank and subjecting it to cyclonic separation.

26.The method according to claim 25 further comprising returning at least some of the solids extracted by the cyclonic separation to fluid undergoing screw classification. - 4 -

27.The method according to claim 25 or 26 further comprising returning at least some of the fluid after the cyclonic separation to the tank or to another tank in communication with the tank..

28.A method of controlling the solids content of drilling mud, the method comprising causing the drilling mud to flow along a flow path and subjecting the drilling mud to a centrifugal separation process to remove solids therefrom.

29.A treatment system comprising a fluid flow path for conveying therealong a fluid having solids suspended therein, the fluid flow path incorporating a separation device for removal of solids from the fluid, the flow path having a suction section being adapted for communication with a surplus volume of the fluid.

30.A solids control unit for drilling mud, comprising a structure defining a treatment reservoir and a storage reservoir, an inlet line having an entry end adapted to receive drilling mud for treatment to remove solids therefrom, a fluid pump for conveying the drilling mud from the inlet line to a hydrocyclonθ at which the drilling mud is treated to remove solids therefrom, the hydrocyclone having an underflow for discharging solids removed from the drilling mud and

. an overflow from which the treated drilling mud is conveyed to the storage reservoir.

31.A solids control unit for drilling mud comprising a fluid flow path for conveying drilling mud therealong, a treatment reservoir for containing a surplus volume of drilling mud, an inlet line forming part of the flow path, the inlet line opening onto the interior of the treatment reservoir for communication with surplus drilling mud contained therein and having an entry end above the level of surplus drilling mud contained within the reservoir, and a hydrocyclone in the fluid flow path for removal of solids from the drilling mud, the hydrocyclone being adapted to receive drilling mud from the inlet line.

32. A method of treating a fluid using a system according to claim 29. - 5 -

33.A method of treating a drilling mud to control the solids content thereof using a solids control unit according to claim 30 or 31.

34.A method of treating a fluid to remove solids therefrom, the method comprising causing the fluid to flow along a flow path and delivering the fluid to a separation device at which solids are removed from the fluid, and exposing the fluid flow to surplus fluid at a suction section of the of the flow path prior to delivery to the separation device.

35.A method of controlling the solids content of drilling mud, the method comprising causing the drilling mud to flow along a flow path, exposing the drilling mud flowing along the flow path to surplus drilling mud at a suction section of the of the flow path, and subjecting the drilling mud to a centrifugal separation process to remove solids therefrom.

36.A method of controlling the solids content of drilling mud, the method comprising causing the drilling mud to flow along a flow path and subjecting the drilling mud to a centrifugal separation process to remove solids therefrom.

37.A solids control unit for drilling mud, comprising a structure defining a treatment reservoir and a storage reservoir, an inlet line having an entry end adapted to receive drilling mud for treatment to remove solids therefrom, a fluid pump for conveying the drilling mud from the inlet line to a hydrocyclone at which the drilling mud is treated to remove solids therefrom, the hydrocyclone having an underflow for discharging solids removed from the drilling mud and an overflow from which the treated drilling mud is conveyed to the storage reservoir.

38.A treatment system substantially as herein described with reference to the accompanying drawings.

39.A treatment apparatus substantially as herein described with reference to the accompanying drawings. - 6 -

40.A treatment unit substantially as herein described with reference to the accompanying drawings.

41.A method of treating drilling mud substantially aβ herein described.

42.A method of treating drilling mud substantially as herein described