SYSTEM AND METHOD FOR A WATER COOLING PUMP
A method and a system are provided for a deep well pump system having a high volume lift of hot or very hot fluids. In an embodiment, a high volume high temperature deep well pumping system uses an external source of cooling fluid to keep one or more vulnerable pumping apparatus components at an acceptable operating temperature. In an embodiment, the cooling fluid, after cooling the component(s), is released into the production fluid flow stream from the pump and both fluids are lifted back up to the surface. In an embodiment, a return tubing, line, or pipe can bring the cooling water back to the surface or other location with or without mixing it with the production fluid.
The present invention relates to a system and method for a deep well pump. More specifically, the present invention relates to a system and method for a cooling apparatus in the deep well pump. The well pump may involve the pumping of any sort of fluid, e.g., oil, water, etc., and the cooling entity may be any sort of appropriate fluid, e.g., water, etc.
BACKGROUNDCurrent systems for deep well pumping involve electrical submersible pumps (“ESPs”) or geared centrifugal pumps (“GSPs”). Such pumps are the current, principal methods used as artificial lifts in high rate oil wells, where a multi-stage centrifugal pump is located downhole. For example, in an ESP system, a downhole electrical motor directly drives the pump, with electric power supplied to the motor via a cable extending from the surface to the motor's location downhole. For example, in a GSP system, the pump is driven via a rotating rod string extending from the surface to a speed increasing transmission system located downhole. The speed increasing transmission system is used to increase the relatively slow rotation of the rod string to a much faster rotation, as needed by the pump. In this example, the rod string is driven by an electric motor situated at the surface.
These current systems, used in the recovery of, e.g., fluids and/or quasi-fluids, experience undesired thermal effects. For example, the temperature of the produced fluid in thermally stimulated oil wells exceeds the operating temperature limits of ordinary downhole pumping systems. For low to moderate productivity wells, the GSP or sucker rod pumping system can be used, provided certain changes in the metallurgy of the downhole components are made. However, such rod pumping systems are incapable of handling highly productive wells. At present, an electric submersible pump (ESP) is the only practical option available. However, the high produced fluid temperatures are particularly severe for a pump system. Also, ESPs have a high voltage electric motor, as well as insulated cable downhole, exposed to temperatures that can exceed 500 degrees Fahrenheit. A mere change in the metallurgy does not cure the high temperature situation. Some systems have increased the operating limit of the downhole electrical components of the ESP system to about 400 degrees Fahrenheit. However, those high temperature systems are expensive and not highly reliable. Accordingly, there exists a need for a reliable, reasonable-cost high temperature system for high volume lift of fluid or quasi-fluid.
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Generally, for an electrical submersible pump to handle a high temperature or a very high temperature, significant modifications in the construction and materials used, e.g., in the motor and electrical cable, must be made. For example, the materials used in the seals and the bearings in the motor protector are specialized for high temperature service. The pressure compensators for balancing the pressure between the interior of the motor and the wellbore are made to have a much larger capacity in order to handle the large temperature variations, and are constructed of a high temperature material. Such modifications results in a much more expensive, less efficient, and possibly less reliable high temperature electrical submersible pump than a normal temperature electrical submersible pump. Presently, while the maximum operating temperature for such high temperature electrical submersible pumps is about 425° F., the recommended continuous operating temperature is significantly less.
Accordingly, a need exists for a system and method of a reliable, cost and time efficient electrical submersible pump which can handle high temperature situations.
The geared centrifugal pump (GCP), for example, as described in U.S. Pat. No. 5,573,063, is, like the ESP, a high volume deep well pumping apparatus. A schematic of a typical normal temperature installation is provided as
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Embodiments of the present invention provide for a relatively easy to install and maintain artificial lift pump for use in oil and water pump systems. More specifically, embodiments of the present invention may be used for deep well pumping of oil, water, or other fluid/quasi-fluid.
Embodiments of the present invention provide for a deep well pump system having a high volume lift of very hot fluids. Further embodiments of the present invention provide for a deep well pump system which uses some components of available normal temperature electrical submersible pumps to provide a more efficient and less expensive system than current high temperature electrical submersible pumps.
Embodiments of the present invention provide for a high volume deep well pumping system adapted to high temperature use by using an external source of cooling fluid to keep the vulnerable pumping apparatus components at an acceptable operating temperature.
Embodiments of the present invention provide a method to cool one or more vulnerable components by using a conduit from the surface carrying the cooling fluid, the fluid effectively cooling the components. In further embodiments, the fluid is ejected into the flow stream from the pump and lifted back up to the surface. In an alternative embodiment, a return line brings the cooling water back to the surface with or without mixing it with the production fluid.
In an embodiment, the tubing 506, which may be used in the normal temperature electrical submersible pump systems as the conduit for the high-pressure formation fluid to flow to the surface, is used in this high temperature electrical submersible pump system to transport cooling water from the surface to the motor 510, e.g., electric motor, and protector 508 downhole. This cooling water flows down the tubing 506 into the shroud 509 surrounding the motor 510 and protector 508, along the shroud-motor annulus, and out the cooling water outlet 511 shown. This water very effectively cools the motor 510 and protector 508, allowing the use of normal temperature components. Also, as shown in
In an embodiment of the present invention—whether an ESP, GCP, or other system—the tubing carrying the cooling water must be insulated, as it is immersed in produced water and/or oil that can have a high temperature, e.g., a temperature as high as 500° F. If the tubing is not insulated, the cooling water will reach ambient temperature, e.g., ˜500° F. if that is the temperature of the produced or formation fluid, by the time the cooling water reaches the pump and thus provide no cooling effect. For example, in an embodiment, in an about 1500 foot deep well, if the about 1500 feet of about 2⅞″ tubing is fitted with a layer of insulation of about 0.6 inch thick with an R factor of 30, then about 250 bpd of cooling water with a temperature of about 60° Fahrenheit may reach the downhole equipment at a temperature of less than about 160° F., which will very effectively cool the motor. The R factor being a known measure of an insulation's ability to keep heat in or heat out. The higher the R factor, the better it works as a barrier, and possibly the thicker the insulation. For example, if a smaller about 2⅜″ tubing is used with an about 0.8″ layer of similar insulation, the about 60° F. input water may reach the downhole motor with a temperature of about 120° F.
In an embodiment of the present invention, the amount of water required to effectively cool the motor is small compared to the amount of fluid pumped to surface by the pump and motor in a well pump system. For example, assuming the motor is putting about 100 horsepower (HP) into the pump, and the motor and power cable efficiency is about 75%, then power cable must deliver about 133 HP of electrical power to the motor. The about 33 HP that does not go into the pump as mechanical power is instead converted into heat by the motor and cable, and equals, in this example, about 2.7 million British thermal units (BTUs) per day. The about 100 HP of motor input into a pump of average efficiency lifts about 3000 barrels per day of fluid from about 1500 feet depth. The about 1500 feet depth is normal for thermal stimulated oil pools.
For example, if about 250 barrels per day (bpd) of cooling water were injected down the tubing of a pump system embodiment according to the present invention, the amount of heat generated by the motor would raise the temperature of the cooling water 31° F. In the situation discussed above, if about 250 bpd of about 60° F. water is injected down about 1500 feet of insulated about 2⅞ inch tubing, the water would reach the motor at a temperature of about 165° F. and be heated to 196° F. as it cools the motor. This temperature is a reasonable operating temperature for available ESP motors. Therefore, the cooling water needed to keep the motor and cable at temperatures within normal design range represents only about an 8% additional volume. The additional energy required to pump the cooling water is also minor. The amount of pressure drop down 1500 feet of 2⅞″ tubing is less than 5 pounds per square inch (psi), so the principal power required to inject the about 250 barrels per day (bpd) of cooling water is that needed to increase the cooling water from atmospheric pressure to that of the produced fluid flow line pressure. For example, a typical flow line pressure can be 150 psi, and the power needed to pump about 250 bpd of water at about 150 psi is less than about 1 HP, a negligible amount.
In the specific examples described herein, as well as those that can be contemplated, these apply for ESP, GCP and other pump systems including for the water cooling embodiment of the present invention. Further, different types of motors can be used in the pump systems. Electric motors and their power cables are described herein for purposes of example, but embodiments of the present invention are not limited to use of such motors.
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In an embodiment, the tubing 606 is used in this high temperature electrical submersible pump system to transport cooling water from the surface to the motor 608, e.g., electric motor, and protector 607 downhole. This cooling water flows down the, e.g., insulated, tubing 606 into the shroud 616 surrounding the motor 608 and protector 607, along the shroud-motor annulus, and out the cooling water outlet 610 shown. This water cools the motor 608 and protector 607, allowing the use of normal temperature components. Further, the power cable 604 to the motor 608 is run inside the tubing 606 and is kept at normal temperatures by the cooling water, eliminating the need for a specialized high temperature cable. The water then flows into the well annulus to join the pump outlet fluid which then all flows to the surface.
In an embodiment, tubing 706 is used in the high temperature electrical submersible pump system to transport cooling water from the surface to the motor 710, e.g., electric motor such as a 450 Series Motor, and protector 708, e.g., a 400 Series Protector, downhole. This cooling water flows down the tubing 706 into the shroud 709 surrounding the motor 710 and protector 708, along the shroud-motor annulus, and out the cooling water outlet 711. This water effectively cools the motor 710 and protector 708, allowing the use of normal temperature components. A power cable 704 to provide power to the motor 710 is run alongside the cooling water tubing rather than internally, i.e., inside the tubing 706. This configuration requires the power cable to be high temperature rated, i.e., manufactured such that it can be used in high temperature environments. For example, a flat #4 Hi-Temp armored cable could be used in an embodiment. The water then flows into the well annulus to join the pump outlet fluid and which then flows to the surface.
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Since the pressure of the hot formation fluid/quasi-fluid is increased by the pump 811, the resulting high-pressure fluid flows into the casing annulus 805 via the pump outlet 810 situated at the top of the pump 811. The packer 812 is used to isolate the perforated well bore from the high-pressure pump outlet 810. Effectively, the pressure inside the well opposite the perforations is at a much lower pressure than that at the pump outlet 812 so that the fluid will flow into the well and eventually up through the pump system. The high-pressure fluid then flows to the surface via the casing 805 and into the production flow line 803 at the wellhead, or other location desired.
It should be understood that there exist implementations of other variations and modifications of the invention and its various aspects, as may be readily apparent to those of ordinary skill in the art, and that the invention is not limited by specific embodiments described herein. Features and embodiments described above may be combined with and without each other. It is therefore contemplated to cover any and all modifications, variations, combinations or equivalents that fall within the scope of the basic underlying principals disclosed and claimed herein.
Claims
1. A fluid pump system for a well, comprising:
- a pump apparatus having a tubing extending from a cooling fluid provider to a motor apparatus, the motor apparatus having an outlet through which fluid can exit from the motor apparatus,
- wherein cooling fluid from the cooling fluid provider runs through the tubing and passes through the motor apparatus such that at least one of a temperature of any materials in the tubing and a temperature of the motor apparatus is affected.
2. The fluid pump system of claim 1, wherein the temperature of the motor apparatus is decreased by the cooling fluid.
3. The fluid pump system of claim 2, wherein the pump system is used for deep wells.
4. The fluid pump system of claim 3, wherein the pump apparatus is one of a modified electrical submersible pump and a modified geared centrifugal pump.
5. The fluid pump system of claim 3, wherein the pump apparatus has a pump driven by the motor apparatus to pressurize any well production fluid entering the pump from the well,
- wherein the resulting pressurized well production fluid is lifted up together with the cooling fluid in the well casing and outside the tubing to a top surface of the well.
6. The fluid pump system of claim 3, wherein the cooling fluid is lifted up in a separate tubing device to one of a top surface of the well and the tubing extending from the cooling fluid provider.
7. The fluid pump system of claim 5, wherein the cooling fluid is water.
8. The fluid pump system of claim 5, further comprising a power cable for providing energy to the motor apparatus is run through the tubing,
- wherein a temperature of the power cable being decreased when in contact with the cooling fluid.
9. The fluid pump system of claim 5, further comprising a power cable for providing energy to the motor apparatus is run outside of the tubing and inside the fluid pump system, wherein the power cable is made of a high temperature resistant material.
10. A fluid pump method, comprising:
- transmitting a cooling fluid through a tubing from an upper level of a deep well pumping system to a motor of the deep well pumping system;
- cooling by the cooling fluid the motor of the deep well pumping system as the cooling fluid passes through the motor;
- leaving by the cooling fluid from the motor into a well casing of the deep well pumping system;
- lifting the cooling fluid from the well casing to the upper level of the deep well pumping system,
- wherein the cooling fluid is lifted to the upper level of the deep well pumping system with any pressurized well fluid, the pressurized well fluid having been pressurized by a pump of the deep well pumping system, the pump being driven by the motor.
11. The fluid pump method of claim 10, wherein the cooling fluid cools a temperature of at least one element disposed within the tubing.
12. The fluid pump method of claim 11, wherein the at least one element disposed within the tubing is at least one of a rod string and a power cable.
13. The fluid pump method of claim 11, wherein the cooling fluid is water and the pressurized well fluid is at least one of water and oil.
14. The fluid pump method of claim 11, wherein the cooling fluid is lifted to the upper level of the deep well pumping system in a separate cavity than the pressurized well fluid.
15. The fluid pump method of claim 11, further comprising:
- separating the pressurized well fluid from the cooling fluid at the upper level of the deep well pumping system, so that any desired and undesired fluids are transported to their respective proper destinations.
16. The fluid pump method of claim 11, wherein the deep well pumping system includes components of one of a geared centrifugal pump and an electric submersible pump, and that any tubing extending from an upper surface of the deep well pumping system to the motor is used as a conduit for the cooling fluid.
Type: Application
Filed: Sep 2, 2009
Publication Date: Mar 3, 2011
Inventor: William Bruce Morrow (Santa Barbara, CA)
Application Number: 12/552,372
International Classification: F04D 29/58 (20060101); F04D 13/08 (20060101);