AU2016101445A4 - Solids Removal Unit - Google Patents

Abstract

An apparatus (11) for treating drilling fluid used in a diamond drilling operation to remove solids therefrom and thereby control the solids content of the drilling fluid. The apparatus is also arranged to introduce additives into the drilling fluid. The apparatus (11) is configured as a unit (13) which is adapted to be transported to the site of the drilling operation. The apparatus (11) has a support structure (15) which carries a tank system (33) comprising first, second and third (41, 42 and 43) and a decanting centrifuge (71) for separating drilling fluid into a solids component and a liquid component with the liquid component being discharged into the first tank (41) The apparatus (11) also has a separator (73) for performing an optional preliminary separation process on the drilling fluid and discharging the separated drilling fluid into the second tank (42). The apparatus (11) is operable in first and second modes, wherein in the first mode drilling fluid for treatment is delivered to the decanting centrifuge (71) and bypasses the mechanical separator (73), and wherein in the second mode drilling fluid for treatment is delivered to the mechanical separator (73) and discharged into the second tank (42) from where it is transferred to the decanting centrifuge (71). 92 \612

Description

Solids Removal Unit TECHNICAL FIELD

[0001] This invention relates to the treatment of drilling fluids to control the content of solids therein.

[0002] More particularly, the invention relates to a system and method for treatment of drilling fluid used in exploration diamond drilling operations to remove drilling solids from the drilling fluid.

[0003] Not all drilling solids need necessarily be removed from the drilling fluid undergoing treatment. Typically, only some of the drilling solids are removed so as to control the solids content of the drilling fluid.

BACKGROUND ART

[0004] 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.

[0005] Exploration diamond drilling is used in the mining industry to drill boreholes for geological surveying and/or geological sampling, [0006] 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, for maintaining the condition of the borehole walls and for conveying drilling cuttings to the ground surface.

[0007] It is well known to provide a mud system 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 a surface ground pit (known as a mud pit) from which drilling mud is pumped to the drill string of a drilling rig and to which the drilling mud is returned from the borehole. Prior to returning to the drill string, the drilling mud is treated 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. Typically, the treatment involves removal of solids from the circulating drilling mud, and introduction of replenishment drilling mud and additives into the circulating drilling mud as necessary.

[0008] In prior art arrangements, the drilling mud is subjected to a classification process for removal of solids therefrom, thereby a controlling the solids content of the drilling mud. in known solids control systems, the classification process typically includes using the mud pit as a gravity settling pond which may or may not be supplemented by mechanical separation processes such as, for example, lamella separation, cyclone separation, other settling systems or any combination thereof.

[0009] Diamond drilling produces smaller particle sizes (with a micron size predominantly below 30 microns and more particularly beiowlO microns) while drilling a borehole than other drilling methods, (e.g. percussive drilling or rotary tri-cone drilling). These small particles are more easily held in suspension in the drilling mud. Given that gravity settlement in a mud pit requires time, and the smaller the particle sizes to be settled out of the mud the more time is required, the use of mud pits as gravity settling ponds is very inefficient in the case of diamond drilling. Larger ponds are required and significantly more fluid than is actually required to drill the hole needs to be used. This also increases the environmental footprint of the diamond drilling operation.

[0010] In addition, the fine particles produced by diamond drilling are not efficiently removed from the drilling mud by mechanica! separation methods which work with the larger particles (typically above 10 micron and more particularly above 30 microns) produced by other drilling methods. Such methods include lamella separation, shakers and cyclones, [0011] Such arrangements can be cumbersome to transport to and install at a drilling site, and also require the establishment and use of costly and environmentally-damaging mud pits.

[0012] The solids removed by traditional mechanical separation methods have little or no value as a statistically valid sample of the geology as the methods used are so inefficient that contamination of materia! from any specific depth in the borehole by material from another depth in the borehole is certain.

[0013] The present Invention seeks to provide an alternative system for removal of solids from drilling mud addressing at least one, and preferably most (if not all), of the issues with current arrangements as described above.

SUMMARY OF INVENTION

[0014] According to a first aspect of the invention there is provided an apparatus for treating drilling fiuid used in a diamond drilling operation, the apparatus comprising a support structure, a reservoir system supported on the support structure, the reservoir system comprising first, second and third reservoirs, a decanting centrifuge for separating drilling fluid into a solids component and a liquid component with the liquid component being discharged into the first reservoir, a separator for performing an optional preliminary separation process on the drilling fluid and discharging the separated drilling fluid into the second reservoir, a fluid transfer system for transferring drilling fiuid into the third reservoir, the apparatus being operable in first and second modes, wherein in the first mode driliing fluid for treatment is delivered to the decanting centrifuge and bypasses the separator and wherein in the second mode drilling fluid for treatment is delivered to the separator and discharged into the second reservoir.

[0015] Preferably, the apparatus is configured and sized to provide a compact arrangement.

[0016] Preferably, the apparatus is configured as a transportable unit.

[0017] Preferably, the decanting centrifuge is operable to remove cutting solids of a size below about 10 microns. The decanting centrifuge can remove solids of a size as low as about 2 micron, although solids of a size as low as about 5 micron are typically removed effectively.

[0018] The decanting centrifugal separation is operable to separate the driliing fluid into a solids component and a liquid component. The liquid component Is, in fact, only predominantly liquid, as it will almost certainly still have some solids content. Trials have indicated that less than about one per cent solids remain in the fluid. Similarly, the solids component is, in fact, only predominantly solids, as it wiil almost certainly still have some liquid content Trials have indicated a liquid content of approximately 10 per cent.

[0019] Preferably, the transfer system comprises a transfer pump.

[0020] Preferably the transfer system further comprises a flow arrangement whereby drilling fiuid can flow from the first reservoir to the third reservoir. The flow arrangement mav comprise a flow path between the first and third reservoirs. The flow path may comprise a weir. The weir may be defined by an opening in a wall between the first and third reservoirs.

[0021] A valve may be provided for selectively blocking flow between the two reservoirs.

[0022] The transfer pump may be selectively operable for transferring drilling fluid from the second reservoir to the decanting centrifuge when the apparatus is configured for operation in the second mode.

[0023] The transfer pump may be selectively operable for transferring drilling fluid from the first, second and third reservoirs. For this purpose, the pump may have an inlet adapted for selective.communication the first, second and third reservoirs [0024] Typically, the transfer system further comprises a suction manifold with which the inlet of the pump is in communication, the suction manifold being adapted for selective communication the first, second and third reservoirs. The suction manifold may selectively communicate with each reservoir through a valve for controlling opening and closing of a flow path between the respective reservoir and the suction manifold.

[0025] Typically, the transfer system further comprises a discharge manifold with which the outlet of the pump is in communication, the discharge manifold having at least one outiet.

[0028] With this arrangement, the discharge manifold can be connected to the intake of the decanting centrifuge when the apparatus is configured for operation in the second mode, typically, the discharge manifold can be connected to the intake of the decanting centrifuge by way of a hose.

[0027] Preferably, the discharge manifold has a plurality of outlets each having a valve for controlling opening and closing thereof. The plurality of discharge manifold outlets provides various options for the manner in which the apparatus may be used.

[0028] One of the plurality of discharge manifold outlets is typically designated for connection to the intake of the decanting centrifuge by way of a hose, although any one of the discharge manifold outlets can typically be utilised for this purpose.

[0029] Preferably, the intake of the decanting centrifuge communicates with a feed inlet arrangement having first and second feed inlets.

[0030] The first feed inlet is provided to receive feed drilling mud which is not required to undergo preliminary treatment. Typically, feed drilling mud is delivered to the inlet directly from the borehole or from an intervening holding tank. A first feed inlet valve is associated with the first feed inlet for opening and closing the latter.

[0031] The second feed inlet is provided to receive drilling fluid from the reservoir . system by way of the transfer system. When the apparatus is configured for operation in the second mode, the arrangement is such that the second feed inlet can receive drilling fluid from the second reservoir. A second feed inlet valve is associated with the second feed inlet for opening and closing the latter. Typically, the second feed inlet is connected to the discharge manifold by way of a hose.

[0032] The separator for performing an optional preliminary separation process on the drilling fluid preferably may comprise a mechanical separator. Typically, the mechanical separator comprises a sieve. The sieve may comprise a shaker separator, commonly known as a shale shaker.

[0033] Preferably, the apparatus further comprises delivery system for delivering metered quantities of one or more additives to the third tank for mixing with the drilling fluid. The delivery system may include at least one additive chamber and a delivery pump.

[0034] Preferably, the apparatus further comprises mixing hopper for the selective introduction of dry additive materials to the drilling fluid. Typically, the mixing hopper is configured for delivery of the additives into the third reservoir.

[0035] Preferably, the reservoir system comprises a tank system. The tank system may comprise a tank structure configured to define three tanks corresponding to the first, second and third reservoirs. The three tanks may at times may hereinafter be referred to as the first, second and third tanks.

[0036] The tank structure may be configured as a single unit configured to define the first, second and tanks, [0037] The first and second tanks may be disposed in side-by-side relation and the third tank may be adjacent common ends of the first and second tanks.

[0038] The tank structure may comprise two opposed side wails tapering inwardly with respect to each other whereby a space is define below each tapering side wall on the exterior side thereof.

[0039] The arrangement whereby the tank structure is configured to define spaces on opposed exterior sides thereof below the tapering side walis is advantageous as it provided areas in which componentry of the apparatus can be accommodated, The transfer pump may, for example, be accommodated in one of the spaces. Preferably , the associated suction and discharge manifolds are also accommodated in that same space. Further, the additive chamber and a delivery pump of the additive delivery system may be accommodated in the opposed space, [0040] The tank structure may further comprise two opposed end walis, one of which constitutes a wail of the third tank and the other of which constitutes the opposed end walls of the first and second tanks.

[0041] The apparatus may be provided with a chute for receiving solids from the decanting centrifuge and discharging the solids exteriorly of the apparatus.

[0042] In one arrangement, the end wall of the tank structure in opposed relation to the third tank may be configures as the chute to receive the solids component from the decanting centrifuge and discharge it exteriorly of the apparatus.

[0043] In another arrangement, the chute may be defined by a chute structure movable between operative and collapsed conditions, whereby when in the collapsed condition the chute mechanism is retracted to provide a 'compact arrangement for transportation of the apparatus.

[0044] Preferably, the support structure comprises a base of rectangular configuration in plan.

[0045] Preferably the apparatus is adapted to assume a transport condition in which its periphery when viewed in plan is within the confines of the rectangular base. In other words, the periphery of the apparatus does not extend beyond the rectangular base when the apparatus is in the transport condition.

[0046] Preferably, the support structure comprises a frame structure which incorporates the base and which includes an upright element at each corner of· the base.

[0047] Preferably, the frame structure further includes frame elements extending between the uprights elements at or adjacent the upper ends thereof.

[0048] Preferably, the apparatus incorporates provision for lifting thereof. This may comprise anchoring elements such lugs or eyelets to which lifting devices such as hooks can be attached to lift the apparatus.

[0049] Preferably, the apparatus further comprises a skid adapted to rest on the ground and allow the unit to be moved over the ground in a skidding action. Typically, the base is configured to provide the skid, [0050] According to a second aspect of the invention there is provided a method of treating a drilling fluid using apparatus according to the first aspect of the invention.

[0051] According to third aspect of the invention there is provided a method of treating a drilling fluid used in a diamond drilling operation, characterised in that the method comprises subjecting the fluid to centrifugal separation to remove cutting solids.

[0052] Preferably, the centrifugal separation involves removal of cutting solids of a size below about 10 microns. As mentioned above, the centrifugal separation can remove solids of a size as low as about 2 micron, although solids of a size as low as about 5 micron are typically removed effectively.

[0053] Preferably the centrifugal separation comprises decanting centrifugal separation.

[0054] Typically, the decanting centrifugal separation is performed by introducing the fluid into a decanting centrifuge feed tube.

[0055] The decanting centrifugal separation separates the drilling fluid into a solids component and a liquid component which constitutes the treated drilling fluid. The treated drilling fluid is returned to the drilling site (drill-string) for re-use. The treated drilling fluid may be subjected to further treatment before being returned to the drilling site. The further treatment may be of any appropriate form, including for example addition of additives thereto.

[0056] Preferably, the method further comprises collecting the liquid component in a reservoir such as a tank from which the treated drilling fluid is returned to the drilling site string for re-use.

[0057] Preferably, the liquid component is gravity fed into the reservoir from the decanting centrifuge.

[0058] The additives may be introduced into the treated drilling fluid to control and condition the treated drilling fluid if so desired.

[0059] The drilling fluid may be subjected to a preliminary separation process for pre-treating the fluid to remove some solid content before-the fluid is subjected to the centrifugal separation. Desirably, solid content above about 10 microns would be removed, but typically solid content above about 30 microns is removed.

[0060] The preliminary separation process may comprise a mechanical separation process to remove oversize solids from the drilling fluid. In particular, the mechanical separation process may comprise sieving to screen oversize solids from the drilling fluid. The sieving separation may be performed by a shaker separator, commonly known as a shale shaker. Screening fluids for solid removal is generally ineffective for solids below 30 micron.

[0061] The additives may be introduced into the treated drilling fluid in the reservoir.

[0062] According to a fourth aspect of the invention there is provided a solids control system for treating drilling fluid used in a diamond drilling operation, the system comprising a fluid flow path for conveying the drilling fluid thereaiong, the fluid flow path incorporating a centrifuge for removal of cutting solids from the drilling fluid.

[0063] Preferably, the centrifuge is adapted to remove cutting soiids of a size below about 10 microns from the drilling fluid.

[0064] Preferably, the centrifuge comprises a decanting centrifuge.

[0065] Preferably, the decanting centrifuge, in use, exerts a G force of up to about 2800.

[0066] Preferably, the solids control system further comprises a reservoir system for receiving the drilling fluid after removal of cutting soiids therefrom by the centrifuge.

[0067] Preferably, the centrifuge is so positioned that the treated drilling fluid can gravity flow into the reservoir system, [0068] Preferably, the reservoir system comprises a tank and the decanting centrifuge is mounted above the tank, with the liquid outlet disposed above the tank so that the treated drilling fluid (which constitutes the decanted liquid) can flow directly into the tank.

[0069] Preferably, the tank has an open top.

[0070] Preferably, the decanting centrifuge is so positioned that the separated soiids are discharged exteriorly of the reservoir system. In this regard, the solids outlet of the decanting centrifuge is disposed to one side of the reservoir system.

[0071] Preferably, the solids control system comprises means for performing a preliminary separation process for pre-treating the drilling fluid to remove some solid content before the fluid is subjected to centrifugal separation by the centrifuge.

[0072] Preferably, the solids control system is adapted to permit the preliminary separation process to be optionally employed; that is, in some situations, the solids controi system may be configured to perform the preliminary separation process and in other situations the solids control system may be configured to perform the centrifugal separation without the pretreatment.

[0073] Preferably, the preliminary separation process comprises a mechanical separation process.

[0074] Preferably, means for performing a preliminary separation process comprises a sieve, [0075] Preferably, the sieve performs mechanical vibratory sieving. Typically, the sieve comprises a shaker separator, commonly known as a shale shaker.

[0076] Preferably, the tank which receives the drilling fluid after removal of cutting soiids therefrom by the centrifuge comprises a first tank.

[0077] , Preferably, the reservoir system further comprises a second tank disposed to receive pre-treated drilling fluid from the means for performing a preliminary separation process.

[0078] Preferably, the reservoir system further comprises a third tank in which an additive is introduced in the drilling fluid. Typically, various additives are introduced into the drilling fluid.

[0079] The solids control system may further comprise an agitator for agitating the fluid contents of the third tank.

[0080] Preferably, the solids control system further comprises means for delivering metered quantities of one or more additives to the third tank for mixing with the drilling fluid.

[0081] Preferably, the soiids control system further comprises means operable to selectively allow fluid flow from the first tank to the third tank. Such means may comprise an overflow weir disposed between the first and third tanks whereby fluid in the first tank can flow over the weir into the third tank, and a gate associated with the weir to close the weir against fluid flow between the first and third tanks.

[0082] According to a fifth aspect of the invention there is provided apparatus incorporating a solids control system in accordance with the second aspect of the invention.

[0083] Preferably, the apparatus is configured and sized to provide a compact arrangement.

[0084] Preferably, the apparatus is configured as a transportable unit.

[0085] Preferably, the apparatus comprises a structure supporting the solids control system. The structure may incorporate a skid adapted to rest on the ground and allow the unit to be moved over the ground in a skidding action.

[0086] Preferably, the support structure comprises a mounting frame for supporting the decanting centrifuge in an elevated condition above the tank.

[0087] Preferably, the mounting frame comprises a support portion configured to receive ,and support the decanting centrifuge and a plurality of legs configured to support portion.

[0088] Preferably, at least one of the legs is positioned in the tank or on a wall(s) of the tank.

[0089] There may be at least one leg disposed at each end of the support portion, with the leg(s) at one end positioned within the tank or on a wail(s) of the tank, and the leg(s) at the other end positioned outside of the tank or on a wall(s) of the tank.

[0090] Preferably, each leg comprises a lower leg section, an upper leg section, and a resilient connection between the two leg sections.

[0091] in one arrangement, the apparatus may be configured for operation under electrical power. This arrangement may be particularly suited to above ground operations.

[0092] in another arrangement, the apparatus may be configured for operation under hydraulic power. This arrangement may be particularly suited to below ground operations.

[0093] According to a sixth aspect of the invention there is provided a method of treating a drilling fluid used in a diamond drilling operation to control the solids content thereof, characterised in that the method uses a system in accordance with the fourth aspect of the invention.

[0094] According to a seventh aspect of the invention there is provided a method of treating a drilling fluid used in a diamond drilling operation to control the solids content thereof, characterised in that the method uses an apparatus in accordance with the fifth aspect of the invention.

[0095] According to an eighth aspect of the invention there is provided an apparatus for treating drilling fluid used in a diamond drilling operation, the apparatus comprising a support structure, a reservoir system supported on the support structure, the reservoir system comprising first, second and third reservoirs, a decanting centrifuge for separating drilling fluid into a solids component and a liquid component with the liquid component being discharged into the first reservoir, a separator for performing an optional preliminary separation process on the drilling fluid and discharging the separated drilling fluid into the second reservoir, a flow arrangement for fluid flow from first reservoir to the third reservoir, and a transfer pump for selectively transferring fluid from the second reservoir to the decanting centrifuge, the apparatus being operable in first and second modes, wherein in the first mode drilling fluid for treatment is delivered to the decanting centrifuge and bypasses the separator and wherein in the second mode drilling fluid for treatment is delivered to the separator and discharged into the second reservoir.

[0096] The flow arrangement may comprise a flow path between the first and third reservoirs. The flow path may comprise a weir. The weir may be defined by an opening in a wall between the first and third reservoirs.

[0097] The apparatus according to the eighth aspect of the invention may have any one or aii the features of the apparatus according to earlier aspects of the invention as appropriate, including in particular a configuration and size to provide a compact arrangement and also a configuration as a transportable unit.

BRIEF DESCRIPTION OF THE DRAWINGS

[0098] Further features of the present invention are more fully described in the following description of a non-limiting embodiment thereof. This description is included solely for the purposes of exemplifying the present invention. It should not be understood as a restriction on the broad summary, disclosure or description of the invention as set out above. The description will be made with reference to the accompanying drawings in which:

Figure 1 is a schematic perspective view, from above and one side, of a transportable treatment unit incorporating a solids control system according to invention;

Figure 2 is a view similar to Figure 1, except that it is a view from the other side;

Figure 3 is a view similar to Figure 1, except that it is viewed from an opposed end;

Figure 4 is a plan view of the transportable treatment unit;

Figure 5 is a schematic perspective view of the transportable treatment unit from the underside thereof;

Figure 6 is a schematic perspective view of the transportable treatment unit with certain parts removed to reveal other parts;

Figure 7 is a fragmentary view, on an enlarged scale, of a transfer system forming part of the transportable treatment unit;

Figure 8 is a fragmentary view, on an enlarged scale, of a feed inlet arrangement;

Figure 9 is a fragmentary view, on an enlarged scale, of a first additives delivery system;

Figure 10 is a fragmentary view, on an enlarged scale, of a further portion of the transportable treatment unit; and

Figure 11 is a fragmentary view, on an enlarged scale, of an agitator forming part of the transportable treatment unit..

[0099] The figures depict an embodiment of the invention. The embodiment illustrates certain configurations; however, it is to be appreciated that the invention can take the form of many configurations, as would be obvious to a person skilled in the art, whilst still embodying the present invention. These configurations are to be considered within the scope of this invention.

DESCRIPTION OF EMBODIMENTS

[00100] Referring to the drawings, there is an embodiment of a treatment system 10 for treating drilling mud used in a diamond drilling operation to control the solids content thereof and also manage the fluid properties of the drilling mud to maintain the drilling mud in a condition suitable for use in a borehole drilling operation.

[00101] The treatment system 10 performs a separation process on the drilling mud for removal of solids therefrom, thereby controlling the solids content of the drilling mud.

[00102] The treatment system 10 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. Other arrangements are, of course possible; for example, the unit 13 could be transportable in some other fashion such as being mounted on a trailer. Alternatively, the unit may be constructed as a permanent installation at the site.

[00103] The unit 13 comprises a support structure 15 which supports a separation system .17. The separation system 17 will be described in detail later, [00104] The support structure 15 incorporates a base 19 adapted to rest on the ground. The base 19 may be configured for movement over the ground in a skidding action. In particular, the base 19 comprises base members 20 and may be configured to incorporate a skid structure to facilitate the skidding action.

[00105] The support structure 15 further comprises a frame structure 25 which incorporates the base 19 and which includes an upright element 27 at each corner of the base. The frame structure 25 further includes frame elements 28 extending between the uprights elements 27 at or adjacent the upper ends thereof, and also intermediate frame elements 29. Anchoring elements 31 are fitted to the frame structure 25 to facilitate lifting of the unit 13. In the arrangement shown, the anchoring elements 31 comprise lugs or eyelets to which lifting devices such as hooks can be attached.

[00106] The separation system 17 further comprises a tank system 33 which is mounted on the support structure 15. The tank system 33 comprises a tank structure 35 which has an interior 37 and which is configured to define three tanks, being a first tank 41, a second tank 42 and a third tank 43. The tank structure 35 is configured as a single unit defining the first, second and tanks. The first and second tanks 41, 42 are disposed in side-by-side relation with a common wall 45 therebetween. The third tank 43 is disposed adjacent common ends of the first and second tanks 41, 42, with a common wall 47 therebetween. The interior 37 of the tank structure 35 is partitioned by the common wails 45, 47 to define the three tanks, [00107] The tank structure 35 comprise two opposed side walls 51, 52, two opposed end walls 53, 54, a bottom 55 and an open top 57. The two opposed side walls 51, 52 taper inwardly and downwardly from the open top 57 to the bottom 55. With this arrangement, spaces 61, 62 are defined below the tapering side walls 51, 52 on the exterior sides thereof. More particularly, the spaces 61, 62 are disposed between the . side walls 51, 52 and the base 19. .

[00108] The arrangement whereby the tank structure 35 is configured to define spaces 61, 62 on opposed exterior sides thereof below the tapering side walls 51, 52 is advantageous as it provided areas within the unit 13 in which componentry of the apparatus can be accommodated, as will become further apparent later.

[00109] The separation system 17 comprises a decanting centrifuge 71 for subjecting the drilling mud to centrifugal separation, and a mechanical separator 73 for performing a preliminary separation process for pre-treating the drilling mud to remove oversize solid content before the drilling mud is subjected to centrifugal separation in the decanting centrifuge 71.

[00110] The preliminary separation process is optional; that is, in some situations the unit 13 may be configured to perform the preliminary separation process and in other situations the unit may be configured to perform the centrifugal separation without the pre-treatment. Accordingly, the unit 13 is operable in first and second modes, wherein in the first mode drilling mud for treatment is delivered to the decanting centrifuge 71 and bypasses the mechanical separator 73, and wherein in the second mode drilling mud for treatment is delivered to the mechanical separator 73 and then later to the decanting centrifuge 71.

[00111] The decanting centrifuge 71 is of known kind and comprises a centrifuge body 75 defining a rotating assembly (not shown) incorporating a bowl and a scroll assembly which cooperate to perform centrifugal separation. The decanting centrifuge 71 has a feed intake 77 into which drilling mud is introduced, a first discharge 79 for decanted liquid (which constitutes the treated drilling mud)) and a second discharge 81 for the separated solids. A drive mechanism 83 is provided for rotating the bowl and scroll assembly in known manner to perform the separation process, in the arrangement shown, the drive mechanism 83 comprises an electric motor 85, although of course any other drive arrangement could be used such as, for example, a hydraulic motor.

[00112] The decanting centrifuge 71 is selected to suit the flow rate requirements and solid particle sizes from a diamond drilling operation. Preferably, the decanting centrifuge 71 is operable to remove cutting solids of a size below about 10 microns. The decanting centrifuge can remove solids of a size as low as about 2 micron, although solids of a size as low as about 5 micron are typically removed effectively.

[00113] The decanting centrifuge 71 is mounted above the tank structure 35 with the first discharge 79 configured as a liquid outlet 91 disposed above the open top of the first tank 41 so that the treated drilling mud (which constitutes the decanted liquid) can flow directly into the first tank 41. Further, the decanting centrifuge 71 is so positioned that the separated solids are discharged exteriorly of the tank structure 35. In particular, in the arrangement shown, the second discharge 81 is arranged to deliver the separated solids to a chute 92 configured to discharge the separated solids to an area adjacent to one side of tank 40. A receptacle (not shown) such as a collection bin may be positioned at the end of the chute 92 to receive the separated solids. In the arrangement shown, the end wall 53 of the tank structure 35 in opposed relation to the third tank 43 is configured to define a sloping exterior surface 93 which functions as the chute 92 to receive the solids component from the decanting centrifuge and discharge it exteriorly of the unit 13. Other arrangements are, of course, possible. By way of example, in another arrangement, the chute 92 may be configured separately of the tank structure 35 as a chute structure hingedly movable between operative and collapsed conditions, whereby when in the collapsed condition the chute structure is retracted into the confines of the frame structure 25 to provide a compact arrangement for transportation of the unit 13.

[00114] In this embodiment, the decanting centrifuge 71 is mounted in an elevated condition above the first tank 41 on a mounting frame 101 which forms part of the support structure 15. The mounting frame 101 comprises a support portion configured as a cradle 103 adapted to receive and support the decanting centrifuge 71 and a plurality of legs 105 configured to support the cradle 103 In the arrangement shown, there are four legs arranged in two pairs, with each pair being disposed at one end of the cradle 103. Each leg 105 comprises a lower leg section (not shown), an upper leg section 113, and a resilient connection 115 between the two leg sections. The resilient connection 115 provides a damped connection between the two leg sections to cushion vibrations arising from operation of the decanting centrifuge 71. the resilient connection may comprise a rubber mount between the two leg sections.

[00115] In the arrangement shown, the upper leg sections 111 are integral with the cradle 103 and the lower leg sections are integral with the support structure 15.

[00116] The mechanical separator 73 comprises a shaker separator 121 of known kind, commonly known as a shale shaker. The shaker separator 121 is supported on the support structure 15 above the second tank 42. Drilling mud for pre-treatment is delivered as feed material to the shaker separator 121 at which it is subjected to a vibratory sieving process. Relatively large solids (commonly known as oversize) are separated from the drilling mud by the shaker separator 121 and subsequently discarded. Desirably, the oversize represented by solid content above about 10 microns would be removed, but typically solid content above about 30 microns is removed. The remaining drilling mud (including undersize solids passing through the - shaker separator 121), which is now pre-treated, flows into the second tank 42 which is located below the shaker separator 121.

[00117] A delivery head 123 is provided for receiving and delivering drilling mud for pre-treatment to the shaker separator 121. The delivery head 123 is mounted on the frame structure 25. The delivery head 123 comprises a tubular body 125 having an inlet 127 to receive the drilling mud and an outlet 129 configured to direct the drilling mud to the shaker separator 121. The inlet 127 is configured as a coupling to which a delivery line can be connected.

[00118] A fluid transfer system 130 is provided for transferring drilling mud into the third tank 43. More particularly, in this embodiment the fluid transfer system 130 is operable to selectively transfer fluid from the three tanks 41, 42, 43 and to also transfer drilling mud to the feed intake 77 of the decanting centrifuge 71. The fluid transfer system 130 may also be used to selectively transfer fluid between the three tanks 41, 42, 43 if circumstances so require.

[00119] For this purpose, the transfer system 130 comprises a flow arrangement whereby drilling mud can flow from the first tank 41 to the third tank 43. The flow arrangement comprises a flow path between the first and third tanks 41. 42. In the arrangement shown, the flow path comprises a weir 135 defined by an opening in the common wall 47 between the first and third tanks 41, 43. A valve 136 is provided for selectively dosing the opening and thereby blocking flow between the first and third tanks 41,43.

[00120] As will become apparent iate.r, drilling mud is typically transferred to the feed intake 77 of the decanting centrifuge 71 from the second tank 42 when the unit 13 is configured for operation in the second mode involving the preliminary separation process performed by the shaker separator 121.

[00121] The transfer system 130 further comprises a transfer pump 141 operable for selectively transferring drilling mud from the first, second and third tanks 41, 42, 43. The transfer pump 141 is also selectively operable to transfer pre-treated drilling mud from the second tank 42 to the feed intake 77 of the decanting centrifuge 71 when the unit 13 is configured for operation in the second mode.

[00122] The transfer pump 141 has an inlet 143 and an outlet 145, with the inlet being adapted for selective communication the first, second and third tanks, as will be explained in further detail later. The pump 141 is driven by a motor 142, which in this embodiment is an electric motor.

[00123] The transfer system 130 further comprises a suction manifold 147 with which the inlet of the pump 141 is in communication. The suction manifold 147 is adapted for selective communication with the first, second and third tanks 41, 42, and 43, More particularly, the suction manifold 147 is adapted for selective communication with each tank 41, 42, 43 through a respective intake line 148 opening onto the bottom 55 of the respective tank, as best seen in Figure 5 A valve 149 is provided in each intake line 148 for controlling opening and closing of the flow path provided by the intake line between the respective tank and the suction manifold 147, In this embodiment, the valves 149 are manually operable.

[00124] The transfer system 130 further comprises a discharge manifold 151 with which the outlet 145 of the transfer pump 141 is in communication, as best seen in Figure 7, The discharge manifold 151 has at least one outlet and preferably a plurality of outlets, The plurality of discharge manifold outlets provides various options for the manner in which the apparatus may be used. In the arrangement shown, the discharge manifold 151 has three outlets 153, 155, 157. A valve 159 is associated with each outlet for controlling opening and closing thereof. In this embodiment, the valves 159 are manually operable.

[00125] With this arrangement, the discharge manifold 151 can be connected to the intake 77 of the decanting centrifuge 71 when the unit 13 is configured for operation in the second mode. Typically, the discharge manifold can be connected to the intake 77 of the decanting centrifuge 71 by way of a hose (not shown} provided for this purpose. Although any one of the discharge manifold outlets 153, 155, 157 can be utilised for connection to the intake 77 of the decanting centrifuge 71, one of discharge manifold outlets is typically designated for that purpose, [00126] The transfer pump 131and the associated suction and discharge manifolds 147, 151 are accommodated in space 61 alongside the tank structure 35 within the confines of the frame structure 25 to provide a compact arrangement for transportation of the unit 13.

[00127] A feed inlet arrangement 160 Is associated with the intake 77 of the decanting centrifuge 71. The feed inlet arrangement 160 comprises a first feed Inlet 161 and a second feed inlet 162. The first feed inlet 161 and a second feed inlet 162 are each configured as a coupling (such as, for example, a threaded coupling) to which a hose can be releasably connected.

[00128] The first feed inlet 161 is provided to receive feed drilling mud which is not required to undergo preliminary treatment. Typically, feed drilling mud is delivered to the first feed inlet 161 directly from the borehole or from an intervening holding tank. A first feed inlet valve 163 is associated with the first feed inlet 161 for opening and closing the latter.

[00129] -The second feed iniet 162 is provided to receive pre-treated drilling mud from the tank system 35 system by way of the transfer system 130 when the unit 13 is configured for operation in the second mode. Typically, the arrangement is such that the second feed inlet 162 receives drilling mud from the second tank 42. A second feed inlet valve 165 is associated with the second feed iniet 162 for opening and closing the latter.

[00130] Typically, the second feed inlet 162 is connected to the discharge manifold 151 by way of the hose, as previously described when, the unit is configured for operation in the second mode..

[00131] The feed inlet arrangement 160 is mounted on the frame structure 25. The feed inlet arrangement 160 is accommodated within the confines of the frame structure 25 to provide a compact arrangement for transportation of the unit 13.

[00132] The unit 13 has provision for introduction of additives to control and condition the treated drilling fluid, according to the specific properties required of the drilling mud for the drilling operation.

[00133] Specifically, the unit 13 comprises a first delivery system 170 for delivering metered quantities of one or more additives to the third tank 43 for mixing with the drilling mud. The delivery system 170 comprises at least one additive chamber 171 and a delivery pump 173. The additive chamber 171 and a delivery pump 173 are accommodated in space 62 alongside the tank structure 35 within the confines of the frame structure 25 to provide a compact arrangement for transportation of the unit 13.

[00134] The unit 13 further comprises a second delivery system 180 for selective introduction of dry additive materials to the drilling mud. The dry additives are typically in powder form, and may comprise dry chemicals such as Bentonite or dry Pac polymer powder. .

[00135] In this embodiment, the dry additive materials are introduced into the third tank 43. in the arrangement illustrated, the second delivery system 180 comprises a delivery head 181 defining a flow passage (not shown), and a mixing hopper 185. The flow passage has an inlet end 187 and an outlet end 189. The inlet end 187 is configured as a coupling (such as, for example, a threaded coupling section) to which one end of a hose can be releasably connected for delivery of drilling mud to the delivery head 181. Typically, drilling mud is delivered to the delivery head 181 from the tank system 35 by the transfer system 130, with the other end of the respective hose being connected to one of the discharge manifold outlets 153, 155, 157. In this way, drilling mud can be conveyed through the flow passage within the delivery head 181. The mixing hopper 185 cooperates with the flow passage to delivery additive materials introduced into the hopper into the fluid stream flowing along the flow passage. In this way, the additive materials are introduced into the drilling mud which is ultimately returned to the drilling site (drill-string) for re-use.

[00136] An agitator 190 is provided for agitating drilling mud in the third tank 43 to ensure proper mixing of additives introduced into the drilling mud. The agitator 190 comprises an agitator shaft assembly 191 accommodated in the third tank 43 and a drive motor 193 for rotating the agitator shaft assembly. The drive motor 193 is mounted above the third tank 43 of the frame structure 25, In this embodiment the drive motor 193 comprises an electric motor, [00137] The tank system 35 is provided with a discharge outlet 200 through which treated drilling mud can extracted for return to the drilling operation. In this embodiment, the discharge outlet 200 is associated with the third tank 43.

[00138] Drilling mud is delivered to the treatment apparatus 11, typically by being pumped along a delivery line (not shown). When the unit 13 is configured for operation in the first mode, the delivery line is typically coupled directly to the first feed inlet 161 of the feed inlet arrangement 160, with the first feed inlet valve 163 being open and the second feed inlet valve 165 being dosed. A centrifugal pump is typically used to pump the drilling mud to the first feed inlet 161 for delivery to the feed intake 77 of the decanting centrifuge 71. When the unit 13 is configured for operation in the second mode, the delivery line is connected to the delivery head 123 which is provided for receiving and delivering drilling mud for pre-treatment to the shaker separator 121. In this configuration, the first feed inlet valve 163 is closed and the second feed inlet valve 165 is open, and the second feed inlet 162 is connected by a hose to the transfer system 130 to receive drilling mud from the second tank 42.

[00139] The drilling mud is returned to the drilling rig after treatment from the third tank 43, with the discharge outlet 200 providing a suction point from which treated drilling fluid can be extracted by a pump (not shown) for delivery to the drilling rig. Replenishment drilling fluid, and any necessary additives, can be mixed with the circulating drilling mud in the tank system 35, according to the specific properties required of the drilling mud for the drilling operation.

[00140] The unit 13 is adapted to be transported to the site of the drilling operation on a load-carrying vehicle. If necessary, the unit 13 can then be moved around site into it . final position by sliding on skids. Any hose piping or other operational components can then be installed as necessary on and to the unit 13 so that it ready for operation Additionally, the unit 13 is connected to the drilling rig with suitable fluid lines to receive drilling mud for treatment and to return treated drilling mud to the drilling rig.

[00141] The unit 13 can be configured and sized to provide a compact arrangement to facilitate transportation. This is facilitated by use of the decanting centrifuge 71 and also by the manner in which the decanting centrifuge is mounted in an elevated condition above the tank system 35. Further, the configuration of the tank structure 35 with sloping side walls 51, 52 providing the spaces 61, 62 to accommodate componentry is conducive to a compact arrangement.

[00142] The decanting centrifuge 71 can perform the required solids removal process while requiring less physical space and associated infrastructure than would be required for a typical prior art solids control systems which might use a classification process using lamella separation, cyclone separation, settling or any combination thereof.

[00143] It is a particular feature of the treatment system according to embodiment that it does not require the use of surface ground pits (known as mud pits). This is because the drilling mud requiring treatment is pumped directly to the treatment unit 13 and is then returned directly to the drilling rig after undergoing the solids removal process in the treatment unit.

[00144] As described above, the treatment unit 13 has provision for optionally performing a preliminary separation process for pre-treating the drilling mud to remove some solid content before the drilling mud is subjected to centrifugal separation by the decanting centrifuge 71. The treatment unit 13 is adapted to permit the preliminary separation process to be optionally employed; that is, in some situations the solids control system may be configured to perform the preliminary separation process and in other situations the soiids control system may be configured to perform the centrifugal . separation without the pretreatment. Typically, the preliminary separation process would be employed in drilling of the top hole section of a borehole where the solids content is likely to be too much for centrifugal separation alone. Specifically, there can be a need for removal of relatively large cuttings, as well as a relatively high volume of cuttings, during drilling of the top hole section.

[00145] When preliminary separation is required, the treatment unit 13 is configured for operation in the second mode to receive drilling mud from the borehole as feed material to the shaker separator 121 at which it is subjected to a vibratory sieving process. Relatively large solids are separated from the drilling mud by the shaker separator 121 and subsequently discarded. The remaining drilling mud, which is now pre-treated, flows into the second tank 42 which is located below the shaker separator 121. The transfer system 130 conveys the pre-treated drilling mud from the second tank 42 to the feed intake 77 of the decanting centrifuge 71 at which it is subjected to decanting centrifugal separation. In this configuration, feed iniet 161 is closed and feed inlet 162 is open. The treated drilling fluid (which constitutes the decanted liquid) flows directly into the first tank 41 and the separated solids are discharged exteriorly of the unit 13 by way of the chute 92. From the first tank 41, the treated drilling mud flows into the third tank 83 via the weir 135. Any necessary additives required for the drilling mud can be introduced into the tank system. From the third tank 43, the treated driliing mud is withdrawn through suction outlet 180 and returned to the drilling rig.

[00146] When preliminary separation is not required, the treatment unit 13 is so configured that feed drilling mud is delivered to the first feed inlet 161 directly from the borehole or from an intervening holding tank (not shown), in this configuration, feed inlet 161 is open and feed inlet 162 is closed. The drilling mud flows to the feed intake 77 of the decanting centrifuge 71 at which it is subjected to decanting centrifugal separation. The treated drilling fluid (which constitutes the decanted liquid) flows directly into the first tank 41 and the separated solids are discharged exteriorly of the unit 13. From the first tank 41, the treated drilling mud flows into the third tank 83 via the weir 135. Any necessary additives required for the drilling mud can be introduced into the tank system. From the third tank 43, the treated drilling mud is withdrawn through suction outlet 180 and returned to the drilling rig.

[00147] In the embodiment described, the treatment unit 13 is configured for operation under electrical power. This arrangement may be particularly suited to above ground operations.

[00148] In another arrangement, the unit 13 may be configured for operation under hydraulic power. In such an arrangement, hydraulic motors rather than electric motors would be employed in the treatment unit 13. This arrangement may be particularly suited to belowground operations.

[00149] It is a feature of the embodiment that the treatment unit.13 has the flexibility to operate in various configurations. This arises in particular because the transfer system 130 is operable in various configurations according to: (a) the settings of the valves 149 for controlling opening and closing of a flow path between each tank 41, 42 and 43 and the suction manifold 147; and (b) the settings of the valves 159 associated with the discharge manifold outlets 153, 155, 157. Further, the plurality of discharge manifold outlets 153, 155, 157 provides various options for the manner in which the treatment unit 13 may be used. With this flexibility, the transfer system 130 can be used to not only pump fluid for the three tanks 41, 42, 43, but also to pump fluid between the three tanks and to other locations if so desired.

[00150] When the unit 13 is operating in the first mode, the second tank may be used for storage purposes to hold replenishment drilling mud or indeed may be used for any other purpose.

[00151] It should be appreciated that the scope of the invention is not limited to the scope of the embodiment described.

[00152] Modifications and improvements may be made without departing from the scope of the invention.

[00153] Reference to positional descriptions, such as lower and upper, are to be taken in context of the embodiments depicted in the figures, and are not to be taken as limiting the invention to the literal interpretation of the term but rather as would be understood by the skilled addressee.

[00154] Throughout this specification, 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 (61)

1. An apparatus for treating drilling fluid used in a diamond drilling operation, the apparatus comprising a support structure, a reservoir system supported on the support structure, the reservoir system comprising first, second and third reservoirs, a decanting centrifuge for separating drilling fluid Into a solids component and a liquid component with the liquid component being discharged into the first reservoir, a separator for performing an optional preliminary separation process on the drilling fluid and discharging the separated drilling fluid into the second reservoir, a fluid transfer system for transferring drilling fluid into the third reservoir, the apparatus being operable in first and second modes, wherein in the first mode drilling fluid for treatment is delivered to the decanting centrifuge and bypasses the mechanical separator and wherein in the second mode drilling fluid for treatment is delivered to the mechanical separator and discharged into the second reservoir.

2. The apparatus according to claim 1 characterised in that it is configured and sized to provide a compact arrangement.

3. The apparatus according to claim 1 or 2 characterised in that it is configured as a transportable unit.

4. The apparatus according to claim 1, 2 or 3 wherein the decanting centrifuge is operable to remove cutting solids of a size.below about 10 microns.

5. The apparatus according to any one of the preceding claims wherein the decanting centrifugal separation is operable separates the’ drilling fluid into a solids component and a liquid component. .

6. The apparatus according to any one of the preceding claims wherein the fluid transfer system comprises a transfer pump.

7. The apparatus according to claim 8 wherein the fluid transfer system further comprises a flow arrangement whereby drilling fluid can flow from the first reservoir to the third reservoir.

8. The apparatus according to claim 8 or 7 wherein the transfer pump is selectively operable for transferring drilling fluid from the first, second and third reservoirs.

9. The apparatus according to claim 8 wherein the transfer system further comprises a suction manifold with which the inlet of the pump is in communication, the suction manifold being adapted for selective communication the first second and third reservoirs.

10. The apparatus according to claim 9 wherein the transfer system further comprises a discharge manifold with which the outlet of the pump is in communication, the discharge manifold having at least one outlet.

11. The apparatus according to any one of the preceding claims wherein the intake of the decanting centrifuge communicates with a feed inlet arrangement having first and second feed inlets.

12. The apparatus according to claim 11 wherein the first feed inlet is provided to receive feed drilling mud which is not required to undergo preliminary treatment and wherein the second feed inlet Is provided to receive drilling fluid from the reservoir system by way of the transfer system.

13. The apparatus according to claim 12 wherein the apparatus is configured such that the second feed inlet can receive drilling fluid from the second reservoir.

14. The apparatus according to any one of the preceding claims wherein the separator for performing an optional preliminary separation process on the drilling fluid comprises a sieve.

15. The apparatus according to claim 14 wherein the sieve comprises a shaker separator.

16. The apparatus according to any one of the preceding claims further comprising a delivery system for delivering metered quantities of one or more additives to the third tank for mixing with the drilling fluid.

17. The apparatus according to any one of the preceding claims further comprising a mixing hopper for the selective introduction of dry additive materials to the drilling fluid.

18. The apparatus according to any one of the preceding claims wherein the reservoir system comprises a tank structure configured to define three tanks corresponding to the first, second and third reservoirs.

19. The apparatus according to claim 18 wherein the tank structure comprises two opposed side walls tapering inwardly with respect to each other whereby a space is define below each tapering side wall on the exterior side thereof whereby spaces are defined on opposed exterior sides thereof below the tapering side wails and wherein componentry of the apparatus is accommodated in the spaces.

20. The apparatus according to claim 19 wherein the transfer pump and the associated suction and discharge manifolds are accommodated in one of the spaces.

21. The apparatus according to claim 20 wherein the delivery system for delivering metered quantities of one or more additives to the third tank is accommodated in the other space.

22. The apparatus according to any one of the preceding claims further comprising a chute for receiving solids from the decanting centrifuge and discharging the solids exteriorly of the apparatus.

23. The apparatus according to claim 22 wherein the tank structure further comprise two opposed end walls, one of which is configured as the chute..

24. The apparatus according to any one of the preceding claims wherein the support structure comprises a base of rectangular configuration in plan.

25. The apparatus according to claim 24 characterised in that it is adapted to assume a transport condition in which its periphery when viewed in plan is within the confines of the rectangular base.

26. The apparatus .according to any one of the preceding claims further comprising provision for lifting thereof.

27. A method of treating a drilling fluid using an apparatus according to any one of the preceding claims.

28. A method of treating a drilling fluid used in a diamond drilling operation, characterised in that the method comprises subjecting the fluid to centrifugal separation to remove cutting solids. 29 The method according to claim 27 or 28 wherein the centrifugal separation comprises removal of cutting solids of a size below about 10 microns.

30. The method according to claim 28 wherein the centrifugai separation comprises decanting centrifugal separation.

31. The method according to claim 30 wherein the decanting centrifugal separation separates the drilling fluid into a solids component and a liquid component which constitutes the treated drilling fluid.

32. The method according to claim 31 further comprising collecting the liquid component in a reservoir system from which the treated drilling fluid is returned to the drilling site siring for re-use.

33. The method according to claim 32 wherein the liquid component is gravity fed into the reservoir from the decanting centrifuge,

34. The method according to any one of claims 28 to 33 further comprising introduction of one or more additives into the treated drilling fluid.

35. The method according to any one of claims 28 to 34 further comprising subjecting the drilling fluid to a preliminary mechanical separation process for pretreating the fluid to remove some solid content before the fluid is subjected to the centrifugai separation.

36. The method according to claim 35 wherein solid content above about 10 microns is removed in the preliminary mechanical separation process..

37. A solids control system for treating drilling fluid used in a diamond drilling operation, the system comprising a fluid flow path for conveying the drilling fluid thereaiong, the fluid flow path incorporating a centrifuge for removal of cutting solids from the drilling fluid,

38. The solids control system according to claim 37 wherein the centrifuge is adapted to remove cutting solids of a size below about 10 microns from the drilling fluid.

39. The solids control system according to claim 37 or 38 wherein the centrifuge comprises a decanting centrifuge.

40. The solids control system according to claim 37, 38 or 39 wherein further comprising a reservoir system for receiving the drilling fluid after removal of cutting solids therefrom by the centrifuge.

41. The solids control system according to claim 40 wherein the centrifuge is so . positioned that the treated drilling fluid 'can gravity flow into the reservoir system.

42. The solids control system according to claim 41 wherein the reservoir system comprises a tank and the decanting centrifuge is mounted above the tank, with the liquid outlet disposed above the tank so that the treated drilling fluid can flow directly into the tank.

43. The solids control system according to claim 42 wherein the decanting centrifuge is so positioned that the separated solids are discharged exteriorly of the reservoir system.

44. The solids control system according to any one of claims 37 to 43 further comprising means for performing a preliminary separation process for pre-treating the drilling fluid to remove some solid content before the fluid is subjected to centrifugal separation by the centrifuge.

45. The solids control system according to claim 44 wherein the system is arranged for the preliminary separation process to be optional.

46. The solids control system according to claim 45 wherein means for performing a preliminary separation process comprises a mechanical separator.

47. The solids control system according to any one of claims 42 to 46 wherein the tank for receiving drilling fluid after removal of cutting solids therefrom by the centrifuge comprises a first tank.

48. The solids control system according to claim 47 wherein the reservoir system further comprises a second tank disposed to receive pre-treated drilling fluid from the means for performing a preliminary separation process.

49. The solids control system according to claim 48 wherein the reservoir system further comprises a third tank for receiving fluid from the first tank.

50. The solids control system according to claim 49 further comprising means for introducing one or more additives into the third tank.

51. The solids controi system according to claim 49 or 50 further comprising a fluid transfer system for transferring drilling fluid into the third tank.

52. An apparatus incorporating a solids control system according to any one of claims 37 to 43.

53. The apparatus according to claim 52 characterised in that it is configured and sized to provide a compact arrangement.

54. The apparatus according to claim 52 or 53 characterised in that it is configured as a transportable unit.

55. The apparatus according to any one of claims 1 to 26 or claims 52 to 54 characterised in that it is configured for operation under electrical power.

56. The apparatus according to any one of claims 1 to 26 or claims 52 to 54 characterised in that it is configured for operation under hydraulic power.

57. A method of treating a drilling fluid used in a diamond drilling operation to control the solids content thereof, characterised in that the method uses a system according to any one of claims 37 to 51.

58. A method of treating a drilling fluid used in a diamond drilling operation to control the solids content thereof, characterised in that the method uses an apparatus according to claim 52, 53 or 54.

59. An apparatus for treating drilling fluid used in a diamond drilling operation, the apparatus comprising a support structure, a reservoir system supported on the support structure, the reservoir system comprising first, second and third reservoirs, a decanting centrifuge for separating drilling fluid into a solids component and. a liquid component with the liquid component being discharged into the first reservoir, a separator for performing an optional preliminary separation process on the drilling fluid and discharging the separated drilling fluid into the second reservoir, a flow arrangement for fluid flow from first reservoir to the third reservoir, and a transfer pump for selectively transferring fluid from the second reservoir to the decanting centrifuge, the apparatus being operable in first and second modes, wherein in the first mode drilling fluid for treatment is delivered to the decanting centrifuge and bypasses the separator and wherein in the second mode drilling fluid for treatment is delivered to the separator and discharged into the second reservoir.

60. The apparatus according to claim 59 wherein the flow arrangement comprises a flow path between the first and third reservoirs.

61. The apparatus according to claim 60 wherein the flow path comprises a weir,

62, A method of treating a drilling fluid using an apparatus according to claim 59, 60 or 61.