MUD PIT AND PUMP APPARATUS THEREFOR

The present invention relates to a mud pit for containing drilling mud used in the construction, maintenance and repair of oil and gas wells , to pump apparatus therefore and to a method of pumping solids laden drilling fluid.

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 and is rotated to bore the borehole. 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 the 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 contains expensive synthetic oil-based or water 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. Other apparatus may be used in the processing of the solids laden drilling mud, such as centrifuges, hydrocyclones , settling tanks with weir systems, vortex dryers and heaters. In the processing of drilling mud, the drilling mud often needs to be stored temporarily in a buffer system before re-use. The buffer system comprises mud pits which may be lined holes in the ground, tanks, or any other suitable container. Pipes are arranged to flow drilling mud into the mud pits and out from the mud pits when drilling mud is required in the

construction, maintenance and repair of the well. The mud pit may also comprise a stirrer or agitator to help maintain chemicals, particles and/or lost circulation material in the drilling mud in suspension. The mud pit is preferably used to buffer processed drilling mud, but may also be used to buffer solids laden drilling fluid. Drilling mud or solids laden drilling mud is pumped from the mud pit with a pump when required. After a period of use, mud pits solids and other detritus build up on the bottom and walls of the mud pit and require cleaning.

The prior art discloses a wide variety of centrifugal pumps; systems that employ them; and systems with such pumps for pumping drilling fluid laden with drilled solids and other solid components ; for example , and not by way of limitation, see U.S. Patents 5,456,580; 5,662,807; 5,846,440; 6,096,228; 6,170,580; 6,179,071; 6,276,824; 6,345,672; 6,406,255; and 6,808,354, all of said patents incorporated fully herein for all purposes .

Pumping systems which employ centrifugal pumps are used to pump mixtures and slurries that contain solids. In certain particular aspects, such systems pump fluids used in the drilling of earth wellbores , tunnelling and excavating. Drilling fluids can contain hazardous material, oil, solids, debris, rock, and shale cuttings. The safe and efficient handling of drilling fluid and its proper disposal result in significant expense in drilling a wellbore .

There has long been a need, recognized by the present inventors, for effective and efficient systems employing centrifugal pumps for pumping mixtures with solids therein. There has long been a need, recognized by the present inventors , for effective and efficient systems for pumping solids-laden drilling fluids.

In accordance with the present invention, there is provided a mud pit for holding solids laden drilling fluid, the mud pit comprising a container and a pump apparatus having a shaft, a motor to drive the shaft and a housing enclosing at least part of the shaft characterised in that the housing comprises an enclosed unvented structure comprising a packing structure and bearing apparatus around the shaft and within the housing. Preferably, the packing structure surrounds the pump shaft and maintains the bearing apparatus in position adjacent the shaft. Advantageously, the packing structure inhibits contaminants from flowing to the bearing apparatus. The unvented structure allows fluids, such as grease and lubricants to be held within the housing at a pressure above the surrounding pressure, which inhibits ingress of contaminates, such as dirt particles, oils, muds etc..

Preferably, the pump apparatus comprises a centrifugal pump. Advantageously, the pump apparatus further comprises seal apparatus to inhibit the ingress of contaminants into the housing. Preferably, the pump apparatus further comprises a grease port for introducing grease into the housing for the at least one seal of the seal apparatus. Preferably, grease adjacent the at least one seal is under pressure to provide a positive internal pressure at a location of the packing structure. Advantageously, the seal apparatus contains at least one seal, such as a rubber o-ring seal. Preferably, the pump apparatus further comprises a lubricant port through the housing for providing lubricant to the bearing apparatus. Advantageously, lubricant is provided within the housing for lubricating

the bearing apparatus , the lubricant expandable upon heating to increase pressure within the housing. The lubricant under pressure, greater than the surrounding pressure, inhibits contaminants from entering an annulus or space between the shaft and the housing, the most vulnerable place for such entry of contaminants being the shaft-housing interface around the packing structure. Heating of the lubricant may be generated from the motor and shaft and by friction or separately by heating generating apparatus .

Preferably, the pump apparatus further comprises a retainer ring with a base and a cylindrical portion encircling a portion of the shaft and the base abutting a bottom of the packing structure. Preferably, the retainer ring inhibits contaminants from contacting the pump shaft. Preferably, the retainer supports and guides the shaft in the event of failure of the bearing apparatus . Advantageously, the cylindrical portion comprises a thread. Preferably, the thread is located on an outer surface of the cylindrical portion for threaded attachment to the housing. Advantageously, the pump apparatus further comprises a seal sealingly contacting an exterior surface of the cylinder and the housing to inhibit the ingress of contaminants. Preferably, the pump apparatus further comprises a further retainer ring. Advantageously, bases of the retainer ring and further retainer ring abut one another. Preferably, the retainer ring has an outer diameter and the further ring has an outer diameter, the outer diameter of the retainer ring larger than the outer diameter of the further retainer ring. Advantageously, the retainer ring has a ring diameter, the bearing apparatus has a bearing diameter, and the ring diameter is greater than the bearing

diameter .

Preferably, the pump apparatus further comprises an impeller apparatus on the shaft, the impeller apparatus abutting the retainer ring. Advantageously, the container is one of: a lined hole; a trough; a tank; a fluid tight container having an open or closed top.

The present invention also provides a pump apparatus for the mud pit of the invention. The present invention also provides a method for pumping solids laden drilling mud, the method comprising the steps of feeding the solids laden drilling mud from a container with a centrifugal pump apparatus comprising a shaft, a motor to drive the shaft, a housing, a packing structure around the shaft and bearing apparatus around the shaft, the housing comprising a non-vented housing, the packing structure, bearing apparatus and part of the pump shaft within the housing, and with the centrifugal pump, pumping the solids laden drilling mud from the container.

The present invention discloses , in certain aspects , systems for pumping mixtures with solids therein. In certain aspects, such systems include a container or tank for receiving and holding the mixture; apparatus for moving the mixture within and from the container; and one or more centrifugal pumps for transferring the mixture from the container to storage or disposal (and/or to mix the mixture within the container to make it homogeneous) .

In certain aspects the mixture contained within a container is a slurry which includes a fluid or fluids and solids in the fluid. In one particular aspect, the mixture is a slurry of drilling fluid from a wellbore with solids (e.g. drilled cuttings, drilled debris, etc.)

therein .

In certain particular aspects , the present invention discloses a centrifugal pump with a packing structure for a pump shaft. The packing structure includes seals that act as containment barriers to prevent outside contamination from entering a pump housing and contacting the shaft and other parts . In certain aspects , the packing structure is sealed within a non-vented space below bearings, a space in which a positive pressure is maintained. Also, with seals isolated and under pressure, and located in a non-vented space, as temperature builds up during operation, lubricant adjacent the seals expands, increasing pressure as compared to pressure external to the packing structure, which contributes to maintaining the seals in isolation and to prohibiting contaminants from entering the system and flowing to the bearings . Thus , the life of parts , e.g. shafts and bearings, can be extended.

In certain aspects , the present invention discloses pumping systems for pumping a drilling mixture containing liquid drilling fluid and solids (e.g., debris, drilled cuttings, etc.) entrained in the liquid drilling fluid, the pumping systems including: a container for receiving and holding the drilling mixture; centrifugal pump apparatus for transferring the drilling mixture from the container, the centrifugal pump apparatus including a pump shaft, a motor to drive the pump shaft, a packing structure around the pump shaft and bearing apparatus around the pump shaft, a housing, the housing comprising an enclosed non-vented structure; and the packing structure, bearing apparatus and part of the pump shaft within the housing.

The present invention discloses , in certain aspects ,

centrifugal pump apparatus including: a pump shaft; a motor to drive the pump shaft; a packing structure around the pump shaft; bearing apparatus for the pump shaft; a non-vented housing able to contain lubricant and/or grease under pressure; and the packing structure, bearing apparatus and part of the pump shaft within the housing.

Such pumping systems with a pump having an isolated packing structure with a relatively high internal pressure which effectively prevents contaminants from entering the system and flowing to items above the packing structure, e.g. preserving vital parts, e.g. bearings and shafts;

Such pumping systems and methods in which a packing structure is located in a non-vented space; and In certain aspects , such a pump in which lubricant heated during operation increases pressure on the packing structure.

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 perspective view of an apparatus in accordance with the present invention;

Figure 2 is a perspective view of the apparatus shown in Figure 1 ;

Figure 3 is a side schematic side view of part of the apparatus shown in Figure 1 , with parts cut away for clarity;

Figure 4 is a perspective view of a pump apparatus of the apparatus shown in Figure 1 ;

Figure 5 is a front view of the pump apparatus shown in Figure 4; Figure 6 is an underside view of the pump apparatus shown in Figure 4 ;

Figure 7 is a cutaway view taken along line 7-7 of Figure 5;

Figure 8 is a cross-sectional view taken along line 8-8 of Figure 6;

Figure 9A is a side view of part of an alternative pump apparatus for use in an apparatus in accordance with the present invention;

Figure 9B is a cross -sectional view taken along line 9B-9B of Figure 9A;

Figure 9C is an enlarged view of part of the pump apparatus shown in Figure 9B;

Figure 1OA is an exploded perspective view of part of the pump apparatus shown in Figure 9A; Figure 1OB is an enlarged perspective view of part of the pump apparatus shown in Figure 1OA; and

Figure 11 is a cross-sectional view of a prior art seal usable in the pump apparatus shown in Figure 9A.

Figures 1 and 2 illustrate an apparatus 10 in accordance with the present invention which has a container 8; a handling system 4; and an auger 6. Any suitable container, tank or pit of any configuration and dimensions may be used. As shown, the container 8 is an elongate tank for receiving and holding a mixture with liquid and solids . In certain particular aspects , the container 8 is designed so that it can be easily transported from location to location; e.g., land locations, on an offshore platform, or to and from other remote locations .

Optionally, the container 8 has a pair of rails 18 supported by braces 20. The handling system 4, which moves on the rails 18, is mounted on a platform or trolley 22 which has a set of wheels 24. The platform 22 has a pair of sprocket wheels 26 which are propelled by a motor and which engage the rails 18 to move the handling system 4 back and forth from one end of the container 8 to the other. The handling system 4 includes a shovel 28 for moving material within and from one end to the other end of the container .

The handling system 4 includes a pump system 30 in accordance with the present invention for pumping material from the container 8. The pump system 30 includes at least one pump in accordance with the present invention .

As shown in Figure 2, the handling system 4 and the shovel 28 have moved within the container 8, pushing material toward one end of the container 8. Here the auger 6 may be activated to move material from the container 8.

Figure 3 shows shovel 28 connected to a boom ladder

40, extending from a first extension member 42. The boom ladder 40 and the first extension member 42 are pivotally attached by a pin 44. The first extension member 42 is attached to the platform 22. A shovel blade 48 is attached to a second extension member 46. An optional detachable shovel blade 50 is attached to the boom member 40 via a third extension member 52.

The pump system 30 includes a pump motor 54 which is fixed to a pump case cylinder 56. A guard 58 is, optionally, included. A suction inlet 60 is spaced above the floor of the container to allow for the guard 58. The guard inhibits ingress of large solids entering the pump system 30 or block off the suction inlet 60. A disposal conduit 62, leading from the pump case cylinder 56, conducts material to a swivel joint conduit 64 for ultimate disposal. The swivel joint may be connected to a flexible hose or rigid pipe (not shown) . Optionally, an oscillator 70 oscillates the boom ladder 40.

Referring now to Figures 4 to 8 , the motor 54 of the pump system 30 is operatively associated with an impeller assembly 200. The pump motor 54 may be any suitable commercially available motor. The shaft from the motor extends to the pump case cylinder 56, with the impeller 200 encased within the pump case cylinder 56. A shaft cover 250 extends from the motor 54 to a top 252 of the pump case cylinder 56. The cover 250 has a top flange 254 and a bottom flange 256, with the top flange 254 connected to a motor flange 258. Lines for the motor include an input line 260 and output line 262 for hydraulic power fluid input and output.

The disposal conduit 62 leads from the pump case cylinder 56. The pump case cylinder 56 has an extension section 264 that stretches to the generally vertically

oriented disposal conduit 62. The extension section 264 also extends to a slurry gate 122 with a passage 124. Brackets 265, 266 are used for mounting the hydraulic motor and legs 58 support the pump case cylinder 56. Figure 5 depicts the impeller assembly 200 and the protrusion of blade ends from a pump case bottom 267. The slurry gate 122 provides an outlet for the system.

In Figure 6, the underside portion of the pump system 30 is illustrated and the impeller assembly 200 is shown projecting from the bottom of the pump case. The extension section 264 extends from the cylindrical pump case cylinder 56. The slurry gate 122 contains a rod 268 that is used to position the gate in an open or closed position. Alternatively, a hydraulic cylinder apparatus is used to move the gate. The pump both mixes the slurry and discharges it.

As shown in Figure 7, a plate 202 is disposed within the pump case cylinder 56. An outer periphery 270 is placed in relatively close relationship with an inner cylindrical wall 272 of the pump case cylinder 56. Material (e.g. mixture; slurry) enters the pump case cylinder 56 from a centre inlet area 208 and is directed through the impeller assembly 200 and outward towards the inner wall 272 due to the centrifugal force generated by rotation. Arrows 274 depicted the travel area of the slurry about the inner circular wall 272 to the extension section 264 which in turn allows passage to the disposal conduit 62. The extension section 264 and the disposal conduit 62 are in fluid communication with one another. The material is then lifted by the pump system 30 up into and out of the conduit 62.

Figure 8 shows the pump system 30 with a rotatable shaft 276 that extends from the motor 54. The shaft

cover 250 is generally a cylindrical member with an inner bore. The inner bore has disposed therein a first set of roller bearings 278 and second set of roller bearings 280 that are separated by a spacer 282. The shaft 276 is threadedly connected to the impeller assembly 200 so that, when the shaft 276 is rotated by the motor, the impeller assembly 200 and associated blades rotate thereby loading the pump case cylinder 56 with the material as previously described. A generally circular opening 284 is at the bottom 267 of the case 56. In one aspect, a wear plate 286 is, optionally, added which adds to the structure and reinforces the pump case 56 thereby protecting from the erosional forces produced during pumping. The slurry gate 124 provides a mixing outlet for the material.

The pump system 30 includes a packing structure 170 in accordance with the present invention which may be any packing structure in accordance with the present invention disclosed herein. The packing structure 170 surrounds the shaft 276.

Figures 9A and 9B show a pump apparatus 300 in accordance with the present invention which has a drive shaft 332 driven by a motor 334. The drive shaft 332 is connected to an impeller assembly (not shown; any suitable impeller, e.g., but not limited to, like the impeller assembly 200, Figure 7) .

The drive shaft 332 extends through a housing 336 and has a lower threaded end 338 for connection to an impeller assembly. The motor 334 is mounted on a plate 342. Flanges 344 are connected to the housing 336 and a base 346.

A bearing spacer 350 spaces-apart upper bearings 352 and lower bearings 354 which facilitate rotation of the

drive shaft 332. Lubricant is contained in a space 356 and encompasses the bearings. This lubricant (e.g. high viscosity lubricant e.g., gear oil) is introduced into the space 356 through a port 358 which is closed off with a plug 362 (e.g. once the space is devoid of air) . A removable snap ring 364 holds the bearings 352, 354 and the bearing spacer 350 in place. Lubricant can flow from the port 358 down to the lowest of the lower bearings 354. The space 356 includes the bearings 352, 354 and the open area below the bearings 352 and space above the bearings 354.

A packing structure 310 in accordance with the present invention surrounds the driving shaft 332 ; maintains the bearings in place; and prevents contaminants from entering the space 356 which could damage or erode parts of the system, e.g. the shaft 332 and/or the bearings .

Figure 9C, 1OA and 1OB show the packing structure 310 in detail. In accordance with the present invention, at least one seal can be used and at least one seal retainer ring can be used. As shown in Figure 9B and Figure 9C there are a plurality of seals 311, 312, 313, 314 held in place by retainer rings or "floor members," a top floor member 316 and a bottom floor member 318. In certain aspects the seals 311 - 314 are made of hard rubber and steel and the floor members are made of high wear resistant material such as, for example, 4140 steel. A single floor member may be used. The floor members have cutouts or recesses R for the seals. The floor members 316, 318 are exteriorly threaded and engage interior threading 337a and 337b on the housing 336. A retainer or "hat" 322 is used between the exterior of the shaft 332 and the seals 311-314. A top end of the

retainer 322 abuts a shoulder 332a of the shaft 332. The retainer has a base 322b and a cylinder 322c. The cylinder 322c encircles part of the shaft 332. The retainer 322 rotates with the shaft 332. An impeller (e.g. an impeller/assembly as in Figure 4) will abut the retainer 322, locking it in place and sealing the bearing housing. The retainer 322 acts as a barrier inhibiting or preventing contaminants and debris from contacting the pump shaft . The upper and lower floor members 316, 318 exceed the interior diameter of the bearings and provide housings for the double set of seals that isolate the bearing area. The floor members 316, 318 also act as temporary supports and guides for the shaft 332, e.g. if a bearing failure occurs . This auxiliary back-up support and guidance function allows for the pump operation to continue until a safe shut down can be made for replacement .

To pressurize the seals 311-314 against the shaft 332, grease under pressure is introduced through a grease fitting 324 into the space occupied by the seals 311-314 and the floor members 316, 318. The pressure of this grease, confined about the seals, provides a positive internal pressure at the location of the packing structure 310. This positive internal pressure is greater than atmospheric pressure external to the bearing housing and is greater than an increased external pressure, e.g. such an increased pressure caused by suction created by impeller turbulence. It is within the scope of the present invention to use one, two, three, four, five, six or more of the seals 311-314 and/or to use one, two, three or more of the floor members 316, 318. A seal hammer can be used to install the seals

evenly in the floor members .

Figure 11 shows a seal member 360 which has a body 326 with a rubber ring 364 in a recess 366. In one aspect, the seal member 360 is used with the rubber ring 364 facing upwardly. The seal 311 prevents bearing lubricant from flowing down into the packing system 300. Any suitable seal may be used instead of the seal members 360.

The present invention, therefore, provides in at least certain embodiments, a pumping system for pumping a drilling mixture containing liquid drilling fluid and solids entrained in the liquid drilling fluid, the pumping system including: a container for receiving and holding the drilling mixture; centrifugal pump apparatus for transferring the drilling mixture from the container; the centrifugal pump apparatus including a pump shaft, a motor to drive the pump shaft, a packing structure around the pump shaft and bearing apparatus around the pump shaft; a housing, the housing which is an enclosed non- vented structure; and the packing structure, bearing apparatus and part of the pump shaft within the housing. Such a system may have one or some, in any possible combination, of the following: seal apparatus for sealing the housing to prevent the ingress of contaminants into the housing; a lubricant port through the housing for providing lubricant to the bearing apparatus; lubricant within the housing for lubricating the bearing apparatus , the lubricant expandable upon heating to increase pressure within the housing to inhibit contaminants from entering the housing through the pump-shaft/housing interface; the seal apparatus containing at least one seal; the packing structure surrounding the pump shaft and maintaining the bearing apparatus in position

adjacent the pump shaft and above the packing structure; the packing structure inhibiting contaminants from flowing to the bearing apparatus ; a retainer with a base and a cylinder, the cylinder encircling a portion of the drive shaft and the base abutting a bottom of the packing structure; the retainer acting as a barrier inhibiting contaminants from contacting the pump shaft; seal apparatus for sealing the housing to prevent the ingress of contaminants into the housing, the seal apparatus including at least one seal, and the at least one seal sealingly contacting an exterior surface of the retainer ring's cylinder; the packing structure including at least one seal, and at least one retainer ring for holding the seal in a sealing position; the at least one retainer ring having a ring diameter, the bearing apparatus having a bearing diameter, and the ring diameter greater than the bearing diameter; impeller apparatus on the pump shaft, the impeller apparatus abutting the retainer; the retainer supporting and guiding the pump shaft in the event of failure of the bearing apparatus; a grease port for introducing grease into the housing for the at least one seal of the seal apparatus; and/or grease adjacent the at least one seal, the grease under pressure to provide a positive internal pressure at a location of the packing structure.