Submersible pump with barrier fluid isolation of motor lubricating liquid from pumped product

Abstract

An electrical submersible pump (ESP) isolates its motor lubricant from pumped product without requiring a bellows, diaphragm, bladder, or external lubricant pressurizing system. A pair of nested isolation chambers below the motor housing are filled with a barrier fluid that is non-reactive, non-miscible, and higher in density than the pumped product and the motor lubricant. As the motor lubricant expands and contracts after pump start-up and shut-down, motor lubricant and barrier fluid are exchanged between the motor housing and the isolation chambers via three interconnections, while pumped product is exchanged with the inner barrier chamber, while being isolated from the motor housing. The interconnections extend between the bottom of the motor housing and the bottom of the outer barrier chamber, between the top of the outer barrier chamber and the bottom of the inner barrier chamber, and between the top of the inner barrier chamber and the pumped product.

Claims

1. An electrical submerged pump (ESP) suitable for pumping a pumped product while isolating the pumped product from motor lubricant contained in a motor housing within the ESP, said isolating being without implementation of a bellows, diaphragm, or bladder, the ESP comprising: a pump comprising a pump impeller contained within a pump housing; an electrical motor; a motor housing surrounding the electrical motor, the motor housing containing a motor lubricant, a lower region of the motor housing extending below the electrical motor; a rotatable shaft extending from the electrical motor to the pump; a seal configured to prevent a pumped product from leaking into the motor housing along the rotatable shaft; a seal housing surrounding the seal; an outer barrier chamber located below the motor housing; an inner barrier chamber nested within the outer barrier chamber; an ESP housing surrounding the pump, the motor housing, and the barrier chambers; a first interconnection configured to enable liquid communication between the lower region of the motor housing and a lower region of the outer barrier chamber; a second interconnection configured to enable liquid communication between an upper region of the outer barrier chamber and a lower region of the inner barrier chamber; a third interconnection configured to provide liquid communication between an upper region of the inner barrier chamber and a product location within the ESP housing, the product location being filled with the pumped product; and a barrier fluid included within the outer and inner barrier chambers, the barrier fluid being immiscible and non-reactive with the motor lubricant and the pumped product, and having a barrier fluid density that is higher than a density of the motor lubricant and a density of the pumped product.

2. The ESP of claim 1, wherein the pumped product includes at least one hydrocarbon.

3. The ESP of claim 2, wherein the pumped product is crude oil.

4. The ESP of claim 1, wherein the pumped product is water.

5. The ESP of claim 4, wherein the pumped product is salt water.

6. The ESP of claim 1, wherein the seal chamber is filled with the barrier fluid, and wherein the ESP further comprises a fourth interconnection configured to provide fluid communication between the seal chamber and the lower region of the inner barrier chamber.

7. The ESP of claim 1, wherein the product location is an intake region of the pump housing.

8. The ESP of claim 1, wherein the product location is within the ESP housing, but exterior to the pump housing, seal housing, motor housing, and barrier chambers.

9. The ESP of claim 1, further comprising a first interconnection valve cooperative with the first interconnection and configured to be closed prior to installation of the ESP, and to remain open following the installation of the ESP.

10. A method of pumping a pumped product while isolating the pumped product from a motor lubricant contained in a motor housing, said isolating being without implementation of a bellows, diaphragm, or bladder, the method comprising: providing an ESP according to claim 1; filling the outer and inner barrier chambers with the barrier fluid; operating the motor, thereby causing the motor lubricant within the motor housing to expand, so that some of the motor lubricant is caused to enter the lower region of the outer barrier chamber through the first interconnection, and from thence to float to the upper region of the outer barrier chamber, said motor lubricant being further caused to enter the lower region of the inner barrier chamber through the second interconnection, and from thence to float to the upper region of the inner barrier chamber, said motor lubricant being further caused to enter the third interconnection; stopping the motor, thereby causing the motor lubricant in the motor housing to contract, so that some of the barrier fluid enters the lower region of the motor housing through the first interconnection, while at least one of motor lubricant and pumped product are caused to flow through the third interconnection and into the upper region of the inner barrier chamber; and restarting the motor, thereby causing the motor lubricant in the motor housing to expand, so that at least some of the barrier fluid that previously entered into the lower region of the motor housing is caused to flow through the first interconnection into the outer barrier chamber, while at least one of motor lubricant and barrier fluid are caused to enter the third interconnection from the inner barrier chamber.

11. The method of claim 10, wherein the ESP further includes a first interconnection valve cooperative with the first interconnection, and wherein the method further comprises: causing the first interconnection valve to be closed before filling the outer and inner buffer chambers with the barrier fluid, thereby maintaining the motor lubricant within the motor housing; and opening the first interconnection valve after filling the outer and inner buffer chambers with the barrier fluid, and before operating the motor.

12. The method of claim 10, wherein the ESP further comprises a fourth interconnection configured to provide fluid communication between the seal housing and the lower region of the inner barrier chamber, and the method further comprises filling the seal housing with the barrier fluid.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a cross-sectional side view of an oil lubricated electrical submersible pump (ESP) configured for pumping water according to the prior art;

(2) FIG. 2 is a cross-sectional side view of an ESP according to an embodiment of the present invention;

(3) FIG. 3 is a cross-sectional side view of the motor housing and barrier chambers of FIG. 2, shown before initial operation of the ESP;

(4) FIG. 4 is a cross-sectional side view of the motor housing and barrier chambers of FIG. 3, shown during initial operation of the ESP;

(5) FIG. 5 is a cross-sectional side view of the motor housing and barrier chambers of FIG. 4, shown after initial operation and shut down of the ESP;

(6) FIG. 6 is a cross-sectional side view of the motor housing and barrier chambers of FIG. 5, shown during resumed operation of the ESP;

(7) FIG. 7 is a cross-sectional side view of an ESP that includes a seal chamber filled with barrier fluid according to an embodiment of the present invention;

(8) FIG. 8A is a cross-sectional side view of the motor housing and barrier chambers of an embodiment that includes a valve coordinate with the first interconnection;

(9) FIG. 8B is a cross sectional view of the valve of FIG. 8A, shown before filling of the barrier chambers with barrier fluid; and

(10) FIG. 8C is a cross-sectional view of the valve of FIG. 8B, shown after filling of the barrier chambers with barrier fluid.

DETAILED DESCRIPTION

(11) The present invention is an electrical submerged pump (ESP) that maintains a separation between the motor lubricant and the pumped product even when the density of the pumped product is similar to or less than the density of the motor lubricant, without requiring that a bellows, diaphragm, or bladder be used to separate the motor lubricant from the pumped hydrocarbons, and without any need for an external motor lubricant pressurizing system.

(12) With reference to FIG. 2, according to the present invention a pair of nested isolation chambers 200, 202 are provided within the ESP below the motor housing 102, and are initially filled with a barrier liquid (dense cross-hatching), referred to herein as the barrier fluid. The barrier fluid does not react with, nor mix with, the pumped product 112 or motor lubricant 104, and has a significantly higher density than the pumped product 112 and the motor lubricant.

(13) Three interconnections 204, 206, 208 are provided that allow liquids to be exchanged between the motor housing 102, the two barrier chambers 200, 202, and a “product region” outside of the motor housing and barrier chambers that contains pumped product. For example, the product region can be the intake of the pump 110, a region 122 within the ESP housing 124 exterior to the pump, motor housings, and barrier chambers, or a region exterior to the ESP housing 124. As can be seen in FIG. 2, the first interconnection 204 is between the bottom of the motor housing 102 and the bottom of the outer barrier chamber 200. The second interconnection 206 is between the top of the outer barrier chamber 200 and the bottom of the inner barrier chamber 202. And the third interconnection 208 is between the top of the inner barrier chamber 202 and the intake of the pump 110. These interconnections 204, 206, 208 ensure that the pressures remain equalized between the motor lubricant 104, the two barrier chambers 200, 202, and the product region.

(14) FIG. 2 illustrates the configuration of the illustrated embodiment immediately after initial installation, and before startup of the ESP. In this configuration, both of the barrier chambers 200, 202 are filled with the barrier fluid. The third interconnection 208 is also filled with the barrier fluid up to a level that is even with the top of the outer barrier chamber 200.

(15) FIG. 3 is a close-up view of the region of FIG. 2 that is surrounded by the dashed rectangle 210. This is the region that is illustrated in all of FIGS. 3-6. The configuration of FIG. 3 is otherwise the same as in FIG. 2.

(16) With reference to FIG. 4, as the motor lubricant 104 expands after initial pump start-up, some of the motor lubricant 104 is pushed through the first interconnection 204 into a lower region of the outer barrier chamber 200. Since the motor lubricant 104 is not as dense as the barrier fluid, the motor lubricant that enters the outer barrier chamber 200 floats to the top of the outer barrier chamber 200 where it forms a first layer 400 of motor lubricant 104 on top of the barrier fluid. When the first layer 400 of motor lubricant 102 in the outer barrier chamber 200 becomes deep enough to reach the top of the second interconnection 206, it flows down the second interconnection 206 and into the inner barrier chamber 202, where it floats to the top and forms a second layer 402 of motor lubricant 104. And when the second layer 402 of motor lubricant 102 becomes deep enough to reach the top of the third interconnection 208, the motor lubricant 104 flows into the third interconnection 208.

(17) Accordingly, during this initial startup of the ESP, a small amount of the motor lubricant 102 may be brought into contact with the pumped product 112. It should be noted, however, that although different crosshatching is used in the drawings to differentiate the motor lubricant 104 from the pumped product 112, in fact in some embodiments they may be of a similar density and/or miscible with each other, such that a small amount of motor lubricant 104 entering into a flow of the pumped product 112 may be acceptable.

(18) With reference to FIG. 5, when the motor lubricant 104 within the motor housing 102 contracts after a first pump shut-down, barrier fluid is drawn from the outer barrier chamber 200 through the first interconnection 204 into the motor housing 102, where it forms a layer 500 at the bottom thereof, but remains separated from the motor 100 due to its high density. The barrier fluid that is drawn out of the outer barrier chamber 200 is replenished by barrier fluid flowing from the inner barrier chamber 202 through the second interconnection 206. At the same time, any motor lubricant 104 that remains in the third interconnection 208 is drawn back through the third interconnection 208 into the inner barrier chamber 202, possibly together with some pumped product 112 drawn from the product region, where it enters the second layer 402 at the top of the inner barrier chamber 202. The first layer 400 of motor lubricant 104 at the top of the outer barrier chamber 200 remains essentially unchanged.

(19) With reference to FIG. 6, when the ESP is re-started and the motor lubricant 104 within the motor housing 102 re-expands, the layer of barrier fluid 500 that was deposited at the bottom of the motor housing 102 is expelled back into the outer barrier chamber 200 through the first interconnection 204 and from there through the second interconnection 206 into the inner barrier chamber 202, thereby expelling through the third interconnection 208 at least some of the liquid that was previously accumulated in the second layer 502 back into the third interconnection 208 and possibly into the product region. In some cases, as illustrated in FIG. 6, a residual second layer 502 of liquid may remain at the top of the inner barrier chamber 202. Once again, the first layer 400 of motor lubricant 104 at the top of the outer barrier chamber 200 remains unchanged.

(20) Subsequent shutdowns and startups of the ESP cause the system to toggle back and forth between the configurations of FIGS. 5 and 6, whereby contraction of the motor lubricant 104 draws barrier fluid into the bottom of the motor housing 102 and pumped product into the inner barrier chamber 202, while expansion of the motor lubricant 104 expels the layer 500 of barrier fluid from the motor housing 102 back into the barrier chambers, and at least some of the liquid in the second layer 502 back into the third interconnection 208. The first layer 400 of motor lubricant 104 at the top of the outer barrier chamber 200 remains unchanged by this process.

(21) It can be seen from the drawings, and especially from FIGS. 5 and 6, that the dual nested barrier chambers 200, 202, together with the locations where the interconnections 204, 206, 208 enter the barrier chambers 200, 202, prevent any of the pumped product 502 from entering the motor housing 102. Furthermore, except for the small amount of motor lubricant 104 that may enter the third interconnection 208 during the first startup (FIG. 4), no further motor lubricant 104 is brought into contact with the pumped product 502. After initial startup, therefore, the motor lubricant 104 remains fully isolated from the pumped product 502.

(22) With reference to FIG. 7, in some embodiments the seal chamber 106 is also filled with barrier fluid, and a fourth interconnection 700 extends from the seal chamber 106 to the bottom of the inner barrier chamber 202, thereby maintaining the seal chamber 106 at the same pressure as the other chambers 102, 200, 202.

(23) With reference to FIGS. 8A, 8B, and 8C, embodiments include a first interconnection valve 800 associated with the first interconnection 204. In the embodiment of FIGS. 8A-8C, the first interconnection valve 800 includes a first interconnection valve stem 802 extending downward from a first interconnection valve plug 804 beyond the lower end of the first interconnection 204 and out of the outer barrier chamber 200 through a first interconnection valve fitting 806. In FIG. 8B, the first interconnection valve 800 is closed, with the first interconnection valve plug 804 being pressed against a first interconnection valve seat 808 formed at the end of the first interconnection 204, thereby isolating the interior of the motor housing 102, which is filled with motor lubricant 104, from the barrier chambers 200, 202, which are initially empty in FIG. 8B. In similar embodiments, the barrier chambers 200, 202 may be filled with an oil during shipment, which can be drained out of the barrier chambers 200, 202 through closable vents (not shown) before filling of the barrier chambers 200, 202 with barrier fluid.

(24) Once the barrier chambers 200, 202 have been filled with barrier fluid, the first interconnection valve 800 is opened, and remains open during operation of the ESP. In the embodiment of FIG. 8C, this is accomplished by attaching a covering cap 810 to the first interconnection valve fitting 806, which pushes the first interconnection valve stem 802 upward, and thereby maintains the first interconnection valve 800 in an open configuration, while also sealing the first interconnection valve fitting 806.

(25) In embodiments such as FIG. 7 that include a fourth interconnection 700 between the seal chamber 106 and the inner barrier chamber 202, the seal chamber 106 is filled with barrier fluid together with the barrier chambers 200, 202.

(26) It should be noted that the disclosed ESP is suitable for pumping any liquid pumped product while using any motor lubricant, so long as the barrier fluid is not miscible nor reactive with the pumped product or motor lubricant, and so long as the densities of the pumped product and of the motor lubricant are less than the density of the barrier fluid.

(27) The foregoing description of the embodiments of the invention has been presented for the purposes of illustration and description. Each and every page of this submission, and all contents thereon, however characterized, identified, or numbered, is considered a substantive part of this application for all purposes, irrespective of form or placement within the application. This specification is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of this disclosure.

(28) Although the present application is shown in a limited number of forms, the scope of the invention is not limited to just these forms, but is amenable to various changes and modifications. The disclosure presented herein does not explicitly disclose all possible combinations of features that fall within the scope of the invention. The features disclosed herein for the various embodiments can generally be interchanged and combined into any combinations that are not self-contradictory without departing from the scope of the invention. In particular, the limitations presented in dependent claims below can be combined with their corresponding independent claims in any number and in any order without departing from the scope of this disclosure, unless the dependent claims are logically incompatible with each other.