CA2229018A1

CA2229018A1 - Pump/separator apparatus for viscous liquids

Info

Publication number: CA2229018A1
Application number: CA002229018A
Authority: CA
Inventors: Peter T. Markovitch
Original assignee: BOWRIO ENERGY LTD.
Current assignee: CDM Inc
Priority date: 1998-02-03
Filing date: 1998-02-03
Publication date: 1999-08-03

Abstract

A pump/separator apparatus for pumping a viscous fluid mixture upwardly from an underground location and for carrying out at least partial separation of the mixture is described. The apparatus comprises a generally cylindrical housing having an intake at or near its lower end and an upper discharge end. One or more impellers (2) is mounted in the housing to rotate about a drive shaft 91), each impeller (2) being of upwardly diverging external shape and arranged to generate a spirally upwardly moving column of fluid which therefore induces inward flow of the mixture through the intake.

Description

This invention relates to a pump/separator apparatus for handling viscous liquids, such as heavy oil bitumen which is being extracted from an underground oil bearing stratum.
The extraction of heavy oil bitumen from an underground "reservoir" presents significant handling problems, by reason of the high viscosity of bitumen, and the presence of other liquids, gases and even solid particles in admixture with the bitumen. The pumping/separation action is presently carried out using bladed impellers or vane-type pumps, which pump the mixture to surface installations at which separation of the mixture into its constituent parts can take place.
In view of the high viscosity of bitumen, conventional pumps and separators require 1o steam injection to lower the viscosity of the bitumen and therefore make it easier to handle, and to be pumped. Then, with the aid of the lifting surfaces on the blades, the bituminous mixture can be lifted to the surface, and after evacuation to a secondary location required the separation process can take place.
These conventional pumps are subject to blade impingement of solids when abrasive materials are present in the pump fluid mixture, which is often the case. T'he resulting erosion of the impeller blades causes the blade pump to be subject to increasing inefficiencies, due to worn impellers and significant down time for repairs and replacements, resulting in high operating and maintenance costs, and incipient pump failures. There is also an additional cost by reason of double-handling of the bituminous 2o mixture, namely, first the pumping action to raise the mixture to the surface, and secondly, a subsequent separation into the component parts, namely solids, liquids and gases.

Cme of the most difficult problems facing conventionally bladed pumps is cavitation.
This phenomenon occurs when the suction pressure on the pump inlet drops below the vapour pressure at the inlet temperature of the fluid being pumped. Given the tf~,mperature and density of a typical heavy oil bitumen, this can be a common occurrence.
s T'he resulting vapour bubbles or pockets in the heavy oil bitumen are impacted by the lifting surfaces of the impeller blades, and these pockets collapse, with the result that the fluid slurry flows slowly into the void left by the collapsed pocket. The resulting implosion wears away at the surface of the impeller blade, causing rapid erosion of the impeller and significant deterioration in pump performance. It also causes severe t o discharge pressure fluctuations, which may damage sensitive downstream equipment.
Unchecked, continual cavitation can cause the pump to loose its "prime", or to trip safety sensors which shut-off the pumping action completely.
The present invention seeks to provide an improved pump/separator apparatus for handling viscous liquids, such as heavy oil bituminous fluid mixtures, and which 1 s overcomes the limitations of conventional pumps having lifting surfaces and requirement fir secondary handling to separate the constituent components.
~~ccording to the invention, there is provided a pump/separator apparatus for pumping viscous fluid mixture upwardly from an underground location and for carrying out at least partial separation of the mixture into separate component parts or phases during the 2o pumping operation, said apparatus comprising:
1. a substantial cylindrical housing having an intake at or near its lower end to receive the viscous fluid mixture, and an upper discharge end; and

2. an inner impeller rotatably mounted in the housing, said impeller rotatably mounted in the housing, said impeller having a radial event which is less than the radial extent of the internal chamber defined by the housing, and said impeller being rotatable around the axis of the housing in order to generate a spirally upwardly moving column of fluid which thereby induces inward flow of the fluid mixture through the intake; and

3. a stack of rotary disks arranged in the housing in a separation zone located above an intake chamber defined in the housing adjacent to t o the intake, said disks being spaced apart from each other with respect to the axis of the housing, and serving to guide the flow of fluid upwardly through the housing and to assist in separation of the fluid into at least some of its separate component parts or phases.
t 5 Preferably, the intake comprises a circumferential inlet formed in the wall of the housing, and a stack of inlet vanes is preferably mounted in the intake chamber of the housing.
T'he inlet vanes may comprise a set of generally planar and parallel vanes which are spaced apart from each other with respect to the axis of the housing.
T'he pump/separator apparatus according to the invention may comprise a multi-20 component assembly, including more than one pump, each having its own respective electric drive motor coupled therewith.

Preferably, a diffuser is arranged in the housing to separate the intake chamber from the separation zone. Also, the separation zone may be sub-divided by a further diffuser, and v~~ith a respective stack of rotary disks in each sub-divided portion.
Preferred embodiment of pump/separator apparatus according to the invention will now be described in detail, by way of example only, with reference to the accompanying drawings, in which:
FIGURE 1:
Is a diagrammatic illustration of a combined disk pump/separator apparatus according to the invention.
~ o FIGURE 2:
Illustrates schematically a minti-pump and drive motor assembly according to a further embodiment of the invention.
FIGURE 3:
Is an enlarged and schematic illustration of the internal components of a pump of the apparatus.
FIGURE 4:
Is a view, similar to Figure 3, and illustrating the path of flow of a viscous fluid mixture through the pump stage of the apparatus.
FIGURE 5a, b and c:
2o Show respectively a perspective view, plan view and elevational view of a further embodiment of pump for use in the apparatus.

4 FIGURE 6:
Is a schematic illustration of the path of flow of bituminous heavy oil through a disk diffuser of a pump of the apparatus.
Referring now to Figures 1 to 6 of the drawings, there will be described embodiments of pump/separator apparatus for pumping a viscous fluid mixture upwardly from an underground location and for carrying out at least partial separation of the mixture into separate component parts or phases during the pumping operation. In general terms, the apparatus comprises a cylindrical housing having an intake at or near its lower end to receive the viscous fluid mixture. and an upper discharge end to which the fluid can be pumped. There is an inner impeller rotatably mounted in the housing and which is operable to generate a spirally upwardly moving column of fluid which rotates around the axis of the housing, and thereby induces inward flow of the mixture through the intake.
?, stack of rotary disks is arranged in the housing in a separation zone which is located above an intake chamber defined by the housing adjacent to the intake, and in which the disks are spaced apart from each other with respect to the axis of the housing, and which serve to guide the flow of fluid upwardly through the housing to the discharge end, and also to assist in separation of the fluid into at least some of its separate component parts or phases.

2o Referring first to Figure 1, an apparatus according to the invention is designated generally by reference (10), and is intended to pump heavy oil bitumen upwardly from an underground stratum (2). The assembly (10) is shown in Figure 1 in enlarged view, and also located within a well casing pipe extending downwardly from a surface location and

5 throughout an overall depth shown by reference (3). At the surface, there is provided electronic control equipment ( 1 ), connected by electric cable (7) to the apparatus ( 10).
T'he apparatus (10) includes separator/pump connected by bolts to the bottom of the tubing flange at the discharge head of the pump. The tubing flange is attached to tubing which extends down the well casing pipe, and with the tubing always being of smaller diameter than l:he casing.
Figure 1 illustrates a single pump assembly (3), for ease of illustration, but in practical applications, more than one pump will be mounted in series below the highest pump at the bottom of the tubing.
?, pump intake (5) allows the bituminous heavy oil fluid mixture to be admitted to the apparatus (10), and then to be pumped upwardly via a pump and housing assembly (3).
Reference numerals (8) and (9) designate electric motors to operate the apparatus.
T'he intake (5) is mounted below the lowest pump and allows for the entry of fluid into the pump stack.. In practice, the location of the pump intake is decided by geo-technical strata being drilled, and the pumps are located above the intake (5). Mounted below the intake is a protective seal which is intended to protect the motors mounted below, while still allowing for fluctuations in motor oil volume and also to accept the pump thrust, thereby isolating the motors from this force. As indicated, the motors) is located below the protector. The motors are generally 60Hz (3) phase squirrel cage motors running at 2,S00 to 3,50() rpm. The bottom of the motor may or may not have a base or sensing device, as required.
Above the purnp(s) is the tubing which extends to the surface or well head.
This tubing may incorporate various drains and valves situated to perform obvious functions relating

6 to fluid transfer. The well head itself is intended to seal the top of the well from gas or fluid leaks, while allowing various lines to penetrate it.
Electrical energy is applied to the motors through a flat cable (7) which is attached to the motor and runs along the side of the protector, the pump and other downhole equipment, and in between the tubing and the well casing. The cable runs through the well head and into a junction box intended to safely vent stray gases in the motor cable shell. Power is connected to the junction box from a switching or motor control cabinet (1) and originates at a transformer that converts utility company voltage to that of the electrical system of the motor. Control and monitoring of motor speed and other characteristics are 1 o undertaken from the surface. Some monitoring of the pump performance also may be performed.

Figure 2 illustrates a dual pump stage and drive motor arrangement which may form a practical and preferred embodiment of the invention.

Figure 3 shows in detail one example of a turbo-disk pump/separator for use in an apparatus according to the invention, and which shows the internal pumping flow path for the high viscosity fluid through the interior of the housing of pump unit (4) shown schematically in Figure 1.
2o F;eferring to Figure 3, the pump/separator unit comprises three major separate components. First of all, the intake (2.l2) comprises a circumferential slot formed in the wall of pump housing (2.15 ), and which communicates with an intake chamber ( defined at a lower end of the casing (2.15), and which receives the incoming flow of

7 viscous fluid mixture. A stack of five planar guide disks (12) is arranged in the intake, and which are vertically spaced apart to define flow passages there between.
The disks (12) have no motion and are positioned about the general vertical axis of the housing of the apparatus, which is defined by motor drive shaft (2.0), driven via its lower end (2.18) by a motor spline connector (2.20), such as to permit fluid to flow into the intake (2.12) a:nd to screen out particles larger than can be accommodated by the pump. The disks ( 12) measured 90 rnm in diameter and are 2.5 mm in thickness, spaced vertically at 2 mm intervals.
A, second major component of the pump/separator unit comprises a central induction core t o which is formed by seven spiral slots which can be set at a variety of angles from the vertical, arranged around a hollow 20 mm drive core machined to match the motor output slhaft. This is shown by reference 2.11 in Figure 3, and which effectively forms an inner impeller rotatably mounted in the housing and which is operable to generate a spirally upwardly moving column of fluid which rotates around the axis of the housing, and thereby induces inward flow of the fluid mixture through the intake.
~~ keyway (2.1 ) is provided to lock the drive core onto the power input shaft of the electric motor. The induction core is situated about the hollow drive core and forms the central section to which the five disks (12) of the intake are attached, for rotation therewith.
2o The spiral slota (2.11 ) cut into the central induction core are angled in such a way that, the greater the viscosity of the fluid to be pumped, the flatter will be the angle which is f armed. Thus, compression separators can be constructed to incorporate a variety of spiral slots. By way of example only, in tests with a bitumen heavy oil of viscosity two H

hundred thousand times that of water, slot angles of about 60~ measured against the vertical were found to be suitable.
In a separation zone 13, 14 within the pump housing (2.15), and above the intake chamber ( 11 ), there are arranged stacks of rotary disks (2.9), and a diffuser arrangement comprising diffuser hub (2.5), diffuser vane (2.6) and diffuser plate (2.7) separate zones 13 and 14, and similarly, a diffuser arrangement separates zone 13 from the intake chamber ( 11 ). The diffuser arrangement is shown in greater detail in Figure 6.
E~y way of explanation, the head loss at an abrupt enlargement or at the exit of a pipe can be considerably reduced by the substitution of a gradual tapered enlargement, usually called a diffuser or a cooperator, the function of which is to gradually reduce the velocity of the fluid and thus eliminate, as far as is practicable, the eddies responsible for energy dissipation. According to Bernoulli's equation, in a perfect diffuser there would be an increase in pressure in the direction of flow if steady flow and uniform conditions over the inlet and outlet cross-sections are assumed. The actual pressure rise is less than the t 5 perfect model .assumed because of head loss, and the loss of head which does occur in the diffuser is dependent on inlet conditions, the angle of divergence, degree of pipe friction present and thE; eddies formed in the flow.
~~s can be seen more clearly in Figure 4, the bottom horizontal plate of the rotor {2.9) is open only in the centre thereof, in the vicinity of the rotor spiral (2.11 ).
This is the only 2o inlet into the rotor from the intake or diffuser immediately below the stage of the pump, and enables fluid to be brought up the central rotor spiral (2.11 ) to the top horizontal plate (:?.9) and to fill the spiral core. There is no outlet at the top horizontal plate (2.9) in the vicinity of the rotor spiral (2.11 ), as a result of which fluid is forced to exit radially outwardly through the spaces between the plates (2.9) as shown in greater detail in Figure 6, although the; arrangement shown in Figure 6 is upside down relative to that shown in Figures 3 and 4. Each diffuser arrangement comprises a diffuser hub (2.5) and diffuser vane (2.6), thc: function of which is to cause fluid leaving the rotor with radial and circumferential movement only to be directed upwards and back into the centre of the rotor spiral (2.11 ) of the pump stage immediately above as smoothly as possible, to enable each stage to act cumulatively. The diffuser hub (2.5) allows fluid to enter from the outside of t:he diffuser, and then the spiral arms of the diffuser vane (2.6) turn the flow direction so as to spiral inwards more than upwards.
t o T'o operate the pump, power is fed to the motor to cause rotation of motor shaft (2.0), to build up speed quickly to rotation at approximately 3,500 rpm. The rotating motor shaft is common to the pump/separator shaft which is mounted above the motor, the intake and the protector. Therefore, rotation of the motor is transferred to the pump/shaft and causes the separator/pump to rotate as well.
T'he separator/pump uses the principle exhibited by a common meteorological tornado to develop a spirally upwardly moving force which draws the heavy oil bituminous fluid upwardly, and this is a more efficient means of fluid transfer, rather than relying upon impact between the fluid components and a lifting surface (as in conventional lifting impeller pump arrangements) to impart upward movement. The lessening of particle 2o impacts, in the invention, gives greater control over the substance heating and friction and factors, which reduces motor horse power requirements.
The separatonpump incorporates flat or concave disks attached to the rotary shaft as described above. The heavy oil bitumen is introduced through the intake mounted to directly below the lowest pump at the centre of the rotating rotary where the boundary layer drag/viscosity drag on either side of the disk imparts energy to the pumped material and the fluid moves outward in a helical path to a suitable configured discharge opening aand into a diffuser where the kinetic energy of the fluid is exchanged for static pressure.
T'he size, number, spacing and speed of the disks will vary according to the ciharacteristics of the heavy bitumen being pumped and the desired performance. Since there is little relative motion between the fluid lift vortex boundary layer and the surface of the disk, thexe is little erosion or abrasion of the impeller disk even when pumping the most abrasive slurries. Further, with substantially no cavitation, the pump separator can 1 o effectively be used to pump and separate gases, liquids or solids, or any combination of the two or three phases.
This versatility allows the separator/pump to move fluid and separate materials or combinations of materials not normally associated with pumping and later separating.
T'he viscous fluid mixture which is to be handled undergoes a separation process, while the pumping operation is being carried out. The particles of the fluid have different specific gravitiies, depending on whether they tend towards solid, liquid or gaseous states.
pas the separator/pump is rotated at high speeds, the frictional drag forces that are part of the pumping process also convey energy in the form of heat to the heavy oil bitumens.
This heat improves the viscosity of the bitumen to a point where it will readily flow and 2o be capable of being pumped. The centrifugal and centripetal forces imparted to the bitumen during the fluid inter phase with the separator/pump causes heavier particles to move towards the outside of the pump housing faster than those particles of lesser specific gravity, such as liquids and gasses. This process eventually separates the fluids into distinct cross-sections, with heavier particles furthest away from the centre and lighter fluids closer to the centre, as in a conventional centrifuge.
Accordingly, the pumping surfaces of the apparatus impart energy by the principle of "lboundary layf:r drag", and separation occurs by mass mixing and subsequent centrifugal separation as an integral part to the lifting process.

Figure 4 is an illustration, similar to Figure 3, and showing the spirally upwardly moving flow of fluid tl~u-ough the interior of the apparatus.
FIGURE 5 Al'~1D FIGURE 6 Figure 5 illustrates an alternative arrangement of components of a pump/separator unit for use in the apparatus, and Figure 6 is a schematic illustration of the induced flow paths of the high viscosity fluid as it undergoes pumping and separation treatment by the apparatus.
Referring now to Figures 7 to 12 of the accompanying drawings, there will now be ~ 5 described prefi~rred embodiments of the present invention. These embodiments comprise and alternative design of pumping arrangement to carry out a generally similar type of pumping action e.g. by generation of negative pressure in a "tornado" type of simulation in the pump housing, to draw viscous fluid mixture through the housing intake, and then to spiral upwardly through the housing while undergoing at least partial separation of the 2o mixture into its component parts or phases.
FIGURES 7 7"O 12 figure 7 is .a schematic illustration of the internal pumping components of the pump/separator apparatus according to the invention, and the parts identified by reference numerals in Figure 7 are set out in the table adjoining the figure of drawings. In particular, a series of separate impeller type of pumping elements (2) is arranged one above the other within a housing, and each comprises a body having an upwardly diverging external shape, which in the illustrated embodiments comprises frusto-conical bodies of revolution mounted for rotation within generally correspondingly shaped receiving seats. The external profile of the bodies are shown in Figure 8 and 9, comprising slots (5) formed in the outer periphery of the bodies (2), and rotation of the bodies generates a spirally upwardly moving flow of the viscous fluid, which simulates the effect of a meteorological tornado, to assist in drawing in of the fluid mixture into the 1 o housing, and an upward induced flow is imparted to the viscous fluid.
F;ach impeller body effectively is located in a separate separation zone of the housing, and with respective diffusers ( 16, 17) separating successive impeller bodies.
The diffusers have the function of converting the rotary motion energy of the upwardly moving flow of fluid into negative pressure which further assists in the uplifting action, and are described in greater detail with reference to Figures 1 to 6.
T'he combined actions of the impeller bodies (2) and the diffusers ( 16, 17) also may assist in separation o~f the viscous mixture into separate component parts and phases. This may take place in generally manner to that described earlier with reference to Figures 1 to 6.
Figures 10 to 12 show further views of the component parts of the pump/separator 2o apparatus sho~,~m in Figure 7, and relevant parts are indicated by reference numerals, vrhich are designated in the tables attached to the drawings.
The frusto-conical type of rotating impeller pumping arrangements illustrated in Figures 7 to 12 are particularly suitable for uplifting heavy oil bitumen from an underground stratum, and which typically may include gases, other liquids such as water, as well as solid particles in admixture. The nature of the handling and lifting action applied by the pump arrangement provides generally the same technical advantages over conventional bladed impeller t;~pe of pumping arrangements with lifting surfaces, as in the apparatus described and illustrated in Figures 1 to 6.
It should be understood that other types of liquid/liquid, liquid/gases, liquid/solid and gas/:liquid/solid mixtures may be handled and pumped by the apparatus shown in Figures 7 to 12, e.g., in the dredging of river or estuary silts, or the pumping of raw sewage.

Claims

CLAIMS:

1. A pump/separator apparatus for pumping a viscous fluid mixture upwardly from an underground location and for carrying out at least partial separation of the mixture into separate component parts or phases during the pumping operation, said apparatus comprising:
(1) a substantially cylindrical housing having an intake at or near its lower end to receive the viscous fluid mixture, and an upper discharge end;
(2) an inner impeller rotatably mounted in the housing, said impeller having a radial extent which is less than the radial extent of the internal chamber defined by the housing, and said impeller being rotatable around the axis of the housing in order to generate a spirally upwardly moving column of fluid which thereby induces inward flow of the fluid mixture through the intake.

2. An apparatus according to Claim 1, wherein the intake comprises a circumferential inlet formed in the wall of the housing.

3. An apparatus according to Claim 2, further comprising a stack of inlet vanes mounted to rotate in an intake chamber of the housing to guide the movement of the induced inward flow of fluid.

4. An apparatus according to Claim 3, wherein the inlet vanes comprise a set of generally planar and parallel vanes which are spaced apart from each other with respect to the axis of the housing.

5. An apparatus according to any one of the preceding claims, comprising a multi-component assembly, including more than one pump, each having its own respective electric drive motor coupled therewith.

6. An apparatus according to anyone of the preceding claims, wherein more than one impeller is mounted in the housing.

7. An apparatus according to Claim 6, wherein a diffuser is arranged in the housing to separate each impeller.

8. An apparatus according to any one of the preceding claims, wherein the or each impeller comprises a frusto-conical body having grooves in its external surface which assist in directing the fluid upwardly and outwardly in a rotating vortex which creates a suction effect like a meteorological tornado, and which assists in pulling the fluid into the housing via the intake and then upwardly through the housing to the discharge end.