APPARATUS AND METHOD FOR PUMPING FLUID The present invention relates to an apparatus and method for pumping drilling fluid. The drilling fluid may be laden with solids. In the drilling of a borehole in the construction of an oil or gas well, a drill bit is arranged on the end of a drill string, which is rotated to bore the borehole through a formation. A drilling fluid known as ""drilling mud" is pumped through the drill string to the drill bit to lubricate the drill bit. The drilling mud is also used to carry cuttings produced by the drill bit and other solids to the surface through an annulus formed between the drill string and the borehole . The drilling mud may also be used to drive downhole drilling motors and to control down hole tools using the flow of drilling fluid and/or the pressure of the drilling fluid to power or activate the motor or dwonhole tool . The density of the drilling mud is closely controlled to inhibit the borehole from collapse and to ensure that drilling is carried out optimally. The density of the drilling mud effects the rate of penetration of the drill bit through the formation. By adjusting the density of the drilling mud, the rate of penetration changes at the possible detriment of collapsing the borehole. Commonly used drilling fluids are either water-based or oil based fluids. They can also contain a variety of additives which provide desired viscosity, lubricating characteristics, heat, anti corrosion and other performance characteristics . The drilling mud may also comprise lost circulation material. The lost circulation material is circulated in the drilling mud past any zones which are porous . Drilling fluid flows through the porous formation carrying with it lost circulation material

which blocks the porous zone . Thus , the drilling mud contains expensive synthetic oil-based lubricants and it is normal therefore to recover and re-use the used drilling mud, but this requires the solids to be removed from the drilling mud. This is achieved by processing the drilling fluid. The first part of the process is to separate the solids from the solids laden drilling mud. This is at least partly achieved with a vibratory separator, such as those shale shakers disclosed in US 5,265,730, WO 96/33792 and WO 98/16328. Further processing equipment such as centrifuges and hydrocyclones may be used to further clean the mud of solids . The solids are covered in contaminates and residues. The clean mud is then retained in a mud tank or other vessel. When required, the clean mud is drawn from the mud tank and back through the drill s tring and the loop repeated. A mud pump may be used to pump drilling mud from the surface through the drill string, out through or near the drill bit and up through the annulus back to the top of the well.

Certain prior, known mud pumps have relatively complex and relatively heavy drive systems with typical connecting rods , eccentric shafts , and multiple rotating bearings, and many of these parts require constant lubrication. Certain prior "triplex" systems have a relatively large footprint.

The prior art discloses a wide variety of drilling systems, apparatuses, and methods including, but not limited to, the disclosures in U.S. Patents 6,944,547; 6,918,453; 6,802,378; 6,050,348; 5,465,799; 4,995,465; 4,854,397; and 3,658,138, all incorporated fully herein for all purposes. The prior art discloses a wide variety of drilling fluid pumps ("mud pumps") used in drilling

operations and pump systems , for example , and not by way of limitation, those pumps and systems disclosed in U.S. Patents 6,257,354; 4,295,366; 4,527,959; 5,616,009; 4,242,057; 4,676,724; 5,823,093; 5,960,700; 5,059,101; 5,253,987; and in U.S. Application Ser. No. 10/833,921 filed April 28, 2004 (all said U.S. references incorporated fully herein for all purposes) .

Mud pumps were traditionally driven by DC motors. AC motors have become more popular in recent years due to their ability to produce extremely high torque.

According to the present invention, there is provided an apparatus for pumping fluid, the apparatus comprising a pumping section having an inlet and an outlet, a shaft of to draw fluid through the inlet and pump fluid out the outlet and a power section for moving the shaft in a reciprocating motion, characterised in that the power section comprises a permanent magnet linear motor for moving the shaft in a reciprocating motion . Preferably, the pump section is single acting. Advantageously, the pump section is double acting. Preferably, the apparatus further comprises a control system. Advantage ously, the control system maintains a flow at a constant rate from through the inlet and/or outlet. Preferably, the control system maintains a constant pressure of fluid output through the inlet and/or outlet.

Preferably, the permanent magnet linear motor is supported by a substantially flat support such that the shaft is reciprocal substantially horizontally. Advantageously, the permanent magnet linear motor is supported such that the shaft is reciprocal substantially vertically.

Preferably, the apparatus comprises at least one further pump section having a permanent magnet linear motor. Advantageously, the apparatus further comprises at least a plurality of further pump sections each having a permanent magnet linear motor. Advantageously, each permanent magnet linear motor is supported by a substantially flat support such that the shaft of each of said motors is reciprocal substantially horizontally. Preferably, each permanent magnet linear motor is supported such that the shaft of each of said motors is reciprocal substantially vertically. An apparatus in accordance with the present invention may have one, two- ten, or more pump sections, each with a permanent magnet linear motor. The present invention also provides a mud pump comprising having a pump section and a power section, the power section comprising a permanent magnet linear motor. Preferably, the mud pump is for pumping drilling fluid, which may be laden with solids , such as drill cuttings . Drilling fluid is commonly referred to as mud or drilling mud.

The present invention also provides a drilling rig comprising a mud pump having a pump section and a power section, the power section comprising a permanent magnet linear motor .

The present invention also provides a drilling system comprising a drilling rig, a borehole, a string of tubulars in the borehole and an annulus formed between the string of tubulars and the borehole, wherein in use mud is circulated through the string of tubulars and borehole back to the drilling rig, characterised in that the drilling system further comprises a mud pump comprising a mud pump having a pump section and a power

section, the power section comprising a permanent magnet linear motor for facilitating circulating mud through the string of tubulars and borehole back to the drilling rig.

Advantageously, the mud is circulated through the drill string and back through the annulus formed between the string of tubulars and the borehole. Preferably, the borehole is lined with casing, the annulus formed between the string of tubulars and the casing. Advantageously, the string of tubulars is at least one of a drill string, string of casing, string of liner and coiled tubing.

The present invention also provides a method for circulating mud, the method comprising the steps of circulating mud with an apparatus having a pump section and a power section, the power section comprising a permanent magnet linear motor.

The present invention also provides a method for pumping fluid, the method comprising the steps of drawing fluid into an inlet of a pumping section and reciprocating at least part of a shaft in and out of the pumping section driven to alternately draw fluid into the inlet and pump fluid out the outlet characterised in that the shaft is reciprocated with a permanent magnet linear motor. Preferably, the fluid is drilling fluid.

In certain aspects of systems in accordance with the present invention in which a linear motor applies power directly, increased efficiencies are possible.

For a better understanding of the present invention, reference will now be made, by way of example, to the accompanying drawings , in which:

Figure 1 is a schematic view, partially cutaway, of a drilling rig incorporating an apparatus in accordance with the present invention;

Figure 2A is a perspective view of an apparatus in accordance with the present invention;

Figure 26 is a side view of the apparatus shown in Figure 2A;

Figure 3A is a perspective view of an apparatus in accordance with the present invention;

Figure 3B is a side view of the apparatus shown in Figure 3A; Figure 4A is a perspective view of an apparatus in accordance with the present invention;

Figure 4B is a perspective view of an apparatus in accordance with the present invention;

Figure 4C is a perspective view of an apparatus in accordance with the present invention;

Figure 5A is a perspective view of an apparatus in accordance with the present invention;

Figure 5B is a top view of the apparatus shown in Figure 5A; Figure 5C is a side view of the apparatus shown in Figure 5A;

Figure 6 is a schematic cutaway side view of an apparatus in accordance with the present invention showing a step in a method in accordance with the present invention;

Figure 7A is a front schematic view of an apparatus in accordance with the present invention;

Figure 7B is a top view of the apparatus shown in

Figure 7A;

Figure 7C is a top view of an apparatus in accordance with the present invention; and

Figure 7D is a top view of an apparatus in accordance with the present invention.

A drilling rig 500 is shown in Figure 1 , which includes a derrick 502 from which extends a drillstring 504 into the earth 506. The drillstring 504, as is well known, includes drill pipes and drill collars. A drill bit 512 is at the end of the drillstring 504. A rotary system 514, top drive system 526, and/or a downhole motor 532 ("fluid motor", "mud motor") may be used to rotate the drillstring 504 and the drill bit 512. A typical drawworks 516 has a cable or rope apparatus 518 for supporting items in the derrick 502. A mud pump system 522 with one, two, three-to-ten, or more mud pumps 521 in accordance with the present invention supplies drilling fluid 524 to the drillstring 504. Drilling forms a wellbore 530 extending down into the earth 506. During drilling, the drilling fluid 524 is pumped by pump(s) 521 of the mud pump system 522 into the drillstring 504 (thereby operating a downhole motor 532 if such an optional motor is used) . Drilling fluid 524 flows to the drill bit 512, and then flows into the wellbore 530 through passages in the drill bit 512. Circulation of the drilling fluid 524 transports earth and/or rock cuttings , debris , etc. from the bottom of the wellbore 530 to the surface through an annulus 527 between a well wall of the wellbore 530 and the drillstring 504. The cuttings are removed from the drilling fluid 524 so that it may be re-circulated from a mud pit or container 528 by the pump(s) of the mud pump system 522 back to the drillstring 506.

Figures 2A and 2B show a mud pump 10 in accordance with the present invention which includes a typical single-action pump end 12 with a discharge port 14 through which drilling fluid is pumped out and a suction line 16 into which drilling fluid is sucked by action of a permanent magnet linear motor 20. A frame 21 supports the motor 20. A shaft 22 of the motor 20 reciprocates within a liner 23 and a body 24 of the pump end 12 to provide the pumping action for the drilling fluid. Appropriate check valves 15 and 17 are used for the port 14 and the line 16, respectively.

As with any permanent magnet linear motor in any apparatus in accordance with the present invention, the motor 20 may be a motor, with suitable power output as disclosed in U.S. Patents 5,910,691; 5,175,455; 6,960,858; or 6,864,647 (or any permanent magnet linear motor disclosed in any reference cited in these patents) , said patents incorporated fully herein for all purposes.

Figures 3A and 3B show a mud pump 30 in accordance with the present invention like the mud pump 10 (and like numerals indicate like parts) . A pump end 32 is a typical double-acting pump with a body 34 within which

(shown schematically) is a typical double-acting mechanism 36. Drilling fluid is sucked in through a suction inlet 33 and pumped out through a discharge port 38. Known valving and seals are used (as is the case with all pump ends disclosed herein) .

Figures 4A to 4C illustrate mud pump systems in accordance with the present invention with multiple pump apparatuses in accordance with the present invention.

Figure 4A shows a mud pump system 40 in accordance with the present invention with three mud pumps 41, 42, 43 in accordance with the present invention connected in

parallel via connections 44 , 45 with a main discharge port 47 and a common suction line 46 which provides fluid to all the mud pumps 41, 42, 43. The mud pumps 41, 42, 43 may be as any disclosed herein in accordance with the present invention .

Figure 4B shows a mud pump system 50 in accordance with the present invention with six mud pumps 51, 52, 53, 54, 55, 56 in accordance with the present invention connected in parallel via connection 59 with a main discharge port 57 and a common suction line 58 which provides fluid to all the apparatuses . The mud pumps 51 , 52, 53, 54, 55, 56 may be as any disclosed herein in accordance with the present invention.

Figure 4C shows a mud pump system 60 in accordance with the present invention with eight mud pumps 61a, 61b, 61c, 61d, 61e, 61f, 61g, 61h in accordance with the present invention connected in parallel via connections 62, 63 with a main discharge port 67 and a common suction line 66 which provides fluid to all the apparatuses . The mud pumps 61a, 61b, 61c, 61d, 61e, 61f, 61g, 61h may be as any disclosed herein in accordance with the present invention .

Figures 5A - 5C show a mud pump system 70 in accordance with the present invention which has six mud pumps 72 in accordance with the present invention (which may be any mud pump in accordance with the present invention disclosed herein). Via a suction line 71, a suction manifold 78 and individual suction lines 73, drilling fluid is sucked into each of the mud pumps 72. Via connections 74, 75 and lines 76 each mud pump 72 pumps fluid to a main discharge port 77. In certain aspects (and as compared to certain prior art systems) due to the pieces and parts of the system 70 (and systems

in accordance with the present invention with upright motors with motor shafts that reciprocate substantially veritically) which project vertically upwardly, such a system in accordance with the present invention can occupy relatively less space than certain prior art systems , i.e., with certain systems in accordance with the present invention a relatively smaller footprint is achieved.

It is within the scope of the present invention for any mud pump apparatus of the present invention to be single-acting or double-acting.

Figure 6 shows schematically a diagram of a system 100 in accordance with the present invention which includes a drillstring 115 with tubulars 116 that have a drill bit 118 at its bottom end. A drilling fluid 120 is pumped by a mud pump system 110 from a source (container or mud pit) 140 into the drillstring 115 by one or more mud pumps 110a - 110c in accordance with the present invention in the mud pump system 110. The drill bit 118 is rotated (by any system or apparatus as described herein) by rotating the drillstring 115. The drill bit 118 cuts the earth formation into fragments 124 (referred to herein as "cuttings") . The drilling fluid 120 discharges at the drill bit 118a and returns to the surface 102 via an annulus 122 carrying the cuttings 124. The returning drilling fluid 126 passes into a riser 128, and then into a return line 130. The fluid 126 returning from the wellbore may be a three phase fluid: liquid, gas and solids. Optionally, the fluid 126 from the return line 130 passes to a shaker that removes the cuttings 124. Optionally, the fluid 126 is then processed in a processor 145. The fluid 120 flows to the pit 140 for pumping down the drillstring 115.

Each of the mud pump apparatuses 110a, 110b, and 110c includes a motor 131 (like any permanent magnet linear motor disclosed herein) with a shaft 132 (like the shaft 22, Figure 2A) extending into a pump end 133 (like any pump end disclosed or referred to herein) . A control system 160 controls the operation of the pump apparatuses 110a, 110b, 110c. In one aspect, the control system automatically insures that the flow of drilling fluid into the drillstring 115 is at a constant rate (litres per minute) or (gals/min) and, in certain aspects, at a variable pressure with a constant stroke speed. Within limits pressure may be held constant by varying speed and flow rate . A typical range for certain mud system flow is between 500 and 2200 gallons per minute and typical pressures range between 1000 and 7500 psi.

The control system 160 receives flow and pressure information from sensors : sensors for position/direction/location of shaft; sensors for fluid discharge pressure; sensors for shaft velocity calculations for flow and pressure control; and sensors indicating number of strokes (in one aspect, parameters sensed by the sensors used to inhibit or eliminate pulsations) . For example, in one aspect sensors 161 sense position of the motor shafts; sensors 162 sense pressure; and sensors 163 count piston strokes.

The control system 160 has computing apparatus, e.g. computer (s) , and/or PLCs; and/or there may be a separate control system for pump(s) (e.g. for turning pumps on and off as needed) and/or which can manage the pumping system.

In one aspect with a system 100 unwanted pulsation can be inhibited or eliminated. As one piston (pump) is about to stroke out and is slowing down, another piston

(pump) increases in speed. These are controlled by controlling the linear motion speed of the pumps.

Systems in accordance with the present invention are useful for pumping, among other things, any fluid pumpable by a reciprocating pump.

Figures 7A and 7B show a system 200 in accordance with the present invention which includes a pump system 202 in accordance with the present invention which is mounted on a support 204 (e.g., but not limited to, a wall or support member of a structure or a wall, beam, or mast portion of a drilling rig) .

As shown in Figure 7B the pump system 202 is mounted flush against the support 204. As shown in Figure 7C the pump system 202 may be supported by and spaced-apart from the support 204 by members 206.

Figure 7D shows a system 220 in accordance with the present invention with multiple pump systems 222 in accordance with the present invention each secured to a support 224 (like the support 204, Figure 7A) . The pump systems 222 may be upright (as shown in Figure 7D) or they may be positioned generally horizontally. A motor of a pump in system in accordance with the present invention may be on a support that is substantially flat (e.g. frame 21, Figure 2B) or the motor may be supported upright so that the motor shaft moves up and down in a substantially vertical movement.

The present invention, therefore, provides in at least some embodiments, a system for pumping fluid having a pump apparatus with a pumping section and a motor section, the pumping section with a body with an inlet and an outlet, the motor section with a shaft for reciprocating in and out to alternately suck fluid (e.g., but not limited to, drilling fluid) into the inlet and

pump fluid out the outlet, and the motor being a permanent magnet linear motor. Such a system in accordance with the present invention may have one or some (in any possible combination) of the following: wherein the pump apparatus is single acting; wherein the pump apparatus is double acting; a control system for controlling the pump apparatus; wherein the control system maintains a flow at a constant rate from the pump apparatus; wherein the control system maintains a constant pressure of fluid output from the pump apparatus; wherein the pump apparatus includes a plurality of pump apparatuses each with a pumping section and a permanent magnet linear motor; and/or wherein the or each permanent magnet linear motor is supported by a substantially flat support so that the shaft is reciprocal substantially horizontally or the or each permanent magnet linear motor is supported so that the shaft is reciprocal substantially vertically.