Patent Grant
10626709
The present disclosure relates in general to submersible pump systems for lifting fluids in a subterranean well, and more particularly to using steam to drive such submersible pump systems.
A current method of producing hydrocarbon fluid from a subterranean well that lacks sufficient internal pressure for natural production is to utilize an artificial lift method such as an electrical submersible pump (ESP). The ESP can impart a higher pressure to the production fluid to lift the fluid column in the wellbore so that the wellbore fluid rises towards the surface. An ESP can be useful, for example, in high gas/oil ratio operations and in aged fields where there is a loss of energy and the hydrocarbons can no longer reach the surface naturally.
The cause of failure of current ESPs is commonly due to short circuits of the ESP system or failure in the power cables that extend from the surface to the ESP motor to drive the pump. In addition, the operation of ESPs can be costly because they require an external electric power source for continuous operation.
Embodiments of this disclosure provide systems and methods for improving the reliability and reducing the operating costs of lifting wellbore fluids to the surface. High temperatures within the wellbore are used to produce gas from a closed fluid system with the gas in turn being used to drive a submersible pump system. The high temperatures can be generated by the heat of the motor of the submersible pump system or can be the result of geothermal energy. In embodiments where excess electrical power is generated by the systems or methods, the excess electrical power can be delivered to a power receiver outside of the subterranean well.
In an embodiment of this disclosure a method of lifting wellbore fluids in a subterranean well towards a surface includes providing a closed water system free of fluid communication with the wellbore fluids, the closed water system having a water storage tank located outside of a high temperature zone of the subterranean well. Water from the water storage tank is circulated into the high temperature zone of the subterranean well to form a steam. A downhole steam turbine is rotated with the steam to drive a submersible pump system that is in fluid communication with the wellbore fluids and the wellbore fluids are lifted towards the surface with the submersible pump system. The steam exiting from the steam turbine is directed towards the water storage tank.
In alternate embodiments, the water storage tank can be located within the subterranean well. The closed water system can be located entirely within the subterranean well. The high temperature zone can be heated with geothermal energy or alternately by the submersible pump system.
In other alternate embodiments, the steam turbine can transfer mechanical rotation of the steam turbine to a shaft of the submersible pump system. A gear assembly can be located between the steam turbine and the submersible pump system so that the rate of rotation of the shaft of the submersible pump system can be varied relative to the rate of rotation of the steam turbine.
In yet other alternate embodiments, the steam turbine can drive an electric generator to power the submersible pump system. A power assembly can be located between the steam turbine and the submersible pump system, the power assembly receiving power by way of an electrical cable for initiating operation of the submersible pump system. The power assembly can alternately operate as the electric generator to power the submersible pump system.
In an alternate embodiment of this disclosure, a method of lifting wellbore fluids in a subterranean well towards a surface includes lowering a submersible pump system into the subterranean well as part of a well completion. A closed fluid is circulated through a closed fluid system that is free of communication with the wellbore fluids. The closed fluid is a liquid within a fluid storage tank located outside of a high temperature zone of the subterranean well. The closed fluid is heated to a gas within the high temperature zone of the subterranean well. The gas is used to rotate a turbine that drives the submersible pump system to lift the wellbore fluids towards the surface. The closed fluid returns to the fluid storage tank.
In alternate embodiments, the flow of the gas into the turbine can be controlled with temperature control valves. Circulating the closed fluid can include circulating the closed fluid through the closed fluid system entirely within the subterranean well. Excess electrical power generated by the turbine can be delivered to a power receiver outside of the subterranean well. The closed fluid can return to the fluid storage tank as a liquid, the closed fluid cooling as the closed fluid exits the high temperature zone of the subterranean well.
In another alternate embodiment, a system for lifting wellbore fluids in a subterranean well towards a surface includes a closed water system that is free of fluid communication with the wellbore fluids, the closed water system having a water storage tank located outside of a high temperature zone of the subterranean well. A circulating system extends from the water storage tank into the high temperature zone of the subterranean well, the circulating system operable to absorb sufficient heat from the high temperature zone to convert water of the closed water system to steam. A downhole steam turbine is rotatable by the steam to drive a submersible pump system in fluid communication with the wellbore fluids and lift the wellbore fluids towards the surface with the submersible pump system. The circulating system extends from the steam turbine towards the water storage tank.
In alternate embodiments, the closed water system can be located entirely within the subterranean well. The steam turbine can be operable to transfer mechanical rotation of the steam turbine to a shaft of the submersible pump system.
In other alternate embodiments, a gear assembly can be located between the steam turbine and the submersible pump system, the gear assembly operable to vary the rate of rotation of the shaft of the submersible pump system relative to the rate of rotation of the steam turbine. Alternately, the system can include an electric generator operable to be driven by the steam turbine and power the submersible pump system. A power assembly can be located between the steam turbine and the submersible pump system, the power assembly operable to receive power by way of an electrical cable for initiating operation of the submersible pump system and alternately operable as the electric generator to power the submersible pump system.
So that the manner in which the above-recited features, aspects and advantages of the disclosure, as well as others that will become apparent, are attained and can be understood in detail, a more particular description of the embodiments of the disclosure briefly summarized above may be had by reference to the embodiments thereof that are illustrated in the drawings that form a part of this specification. It is to be noted, however, that the appended drawings illustrate only certain embodiments of the disclosure and are, therefore, not to be considered limiting of the disclosure's scope, for the disclosure may admit to other equally effective embodiments.
The Specification, which includes the Summary of Disclosure, Brief Description of the Drawings and the Detailed Description, and the appended Claims refer to particular features (including process or method steps) of the disclosure. Those of skill in the art understand that the disclosure includes all possible combinations and uses of particular features described in the Specification. Those of skill in the art understand that the disclosure is not limited to or by the description of embodiments given in the Specification.
Those of skill in the art also understand that the terminology used for describing particular embodiments does not limit the scope or breadth of the disclosure. In interpreting the Specification and appended Claims, all terms should be interpreted in the broadest possible manner consistent with the context of each term. All technical and scientific terms used in the Specification and appended Claims have the meaning commonly understood by one of ordinary skill in the art to which this disclosure relates unless defined otherwise.
As used in the Specification and appended Claims, the singular forms “a”, “an”, and “the” include plural references unless the context clearly indicates otherwise. As used, the words “comprise,” “has,” “includes”, and all other grammatical variations are each intended to have an open, non-limiting meaning that does not exclude additional elements, components or steps. Embodiments of the present disclosure may suitably “comprise”, “consist” or “consist essentially of” the limiting features disclosed, and may be practiced in the absence of a limiting feature not disclosed. For example, it can be recognized by those skilled in the art that certain steps can be combined into a single step.
Spatial terms describe the relative position of an object or a group of objects relative to another object or group of objects. The spatial relationships apply along vertical and horizontal axes. Orientation and relational words including “uphole” and “downhole”; “above” and “below” and other like terms are for descriptive convenience and are not limiting unless otherwise indicated.
Where the Specification or the appended Claims provide a range of values, it is understood that the interval encompasses each intervening value between the upper limit and the lower limit as well as the upper limit and the lower limit. The disclosure encompasses and bounds smaller ranges of the interval subject to any specific exclusion provided.
Where reference is made in the Specification and appended Claims to a method comprising two or more defined steps, the defined steps can be carried out in any order or simultaneously except where the context excludes that possibility.
Looking at
In the example embodiments of
An intake can direct wellbore fluids into the pump section 26. Depending on the configuration of the well completion, the wellbore fluids can pass out of a discharge of submersible pump system 20 into tubular member 22 or into production casing 18 for delivery to the surface. Submersible pump system 20 can, in certain embodiments, also include motor 28 and protector 30 that is located between pump section 26 and motor 28 (
The disclosed methods and systems for lifting wellbore fluids in subterranean well 10 includes closed fluid system 32. Closed fluid system 32 can be a closed water system that utilizes water in a liquid form and in a gas form as steam. In certain embodiments, closed fluid system 32 utilizes demineralized water. Demineralized water provides an approximate 1:1 water/steam ratio, is inexpensive and easy to find, is easy and safe to work with, and has no minerals or other elements that would have to be handled. In alternate embodiments, closed fluid system 32 can utilize an alternate fluid in both liquid and gas form that can operate within the temperature, pressure and energy requirements of the system of the embodiments of this disclosure. As used herein, the term “closed fluid” refers to the fluid used in closed fluid system 32 regardless of the type or state of such fluid.
Closed fluid system 32 is completely separated from the wellbore fluids so that the closed fluid of closed fluid system 32 is free of fluid communication with the wellbore fluids. In this way, the closed fluid of the closed fluid system 32 cannot mingle with the wellbore fluids. Closed fluid system 32 includes fluid storage tank 34 located outside of a high temperature zone of subterranean well 10. In the example embodiment of
In the alternate example of
As the closed fluid in the form of a liquid, such as water, is circulated from fluid storage tank 34 towards turbine 38 the closed fluid passes through high temperature zone 40 of subterranean well 10 to form a gas such as steam. In the example embodiment of
In the example embodiment of
The closed fluid in the form of a gas rotates turbine 38. Turbine 38 can drive submersible pump system 20 which is in fluid communication with the wellbore fluids and can then lift the wellbore fluids towards surface 12. Although turbine 38 is shown schematically at a lower end of tubular member 22, turbine 38 is not in fluid communication with wellbore fluids. It is the fluid of closed fluid system 32 only that rotate turbine 38. The wellbore fluid instead enters the intake of submersible pump system 20 which is separate from, and not in fluid communication with, turbine 38.
Looking at
In embodiments where the high temperature generated by submersible pump system 20 within the region surrounding submersible pump system 20 forms high temperature zone 40, the power assembly can receive electric power by way of source electrical cable 44 (
In alternate embodiments, such as the example embodiment of
After exiting turbine 38, the closed fluid can be directed back to fluid storage tank 34 by way of fluid return line 52. As the closed fluid returns to fluid storage tank 34, the closed fluid exits high temperature zone 40 and can cool to return to the fluid storage tank as a liquid or as a combination of liquid and gas. Temperature control valves 50 can be located between fluid storage tank 34 and turbine 38 and can be used to control the amount of vapor and water going into and out of turbine 38. Even with the temperature control valves 50, all of the steam in the system is used continuously which is more efficient than using steam partially or selectively.
In an example of operation, subterranean well 10 is completed in a traditional manner with submersible pump system 20 and closed fluid system 32 being lowered into subterranean well 10 as part of the well completion. Fluid from fluid storage tank 34 is circulated into high temperature zone 40 of subterranean well 10 to form a gas. The gas is used to rotate downhole turbine 38 with the gas to drive submersible pump system 20. Submersible pump system 20 is in fluid communication with the wellbore fluids and lifts the wellbore fluids towards surface 12 to produce the wellbore fluids. The closed fluid exiting from turbine 38 is directed back towards fluid storage tank 34. In certain embodiments, external electrical power can be used only when starting submersible pump system 20 but is not used during the continuous operation of submersible pump system 20.
Embodiments of this disclosure therefore provide systems and methods for lifting fluids within a wellbore with submersible pump systems that are more reliable and less costly to operate than some current methods and systems. Many of the failures of current electrical submersible pumps are due to short circuit and failures of the cables from the surface to the downhole location where the pump is set. Systems and methods described herein will reduce or eliminate such failures. In addition, current electrical submersible pumps consume large amounts of electrical energy for continuous operation. Systems and methods described herein will reduce operating costs associated with lifting wellbore fluids because embodiments of this disclosure do not require a continuous external electrical power supply. Certain embodiments described herein only require an external electrical power supply for initiating operation of submersible pump system 20.
Embodiments described herein, therefore, are well adapted to carry out the objects and attain the ends and advantages mentioned, as well as others inherent therein. While certain embodiments have been described for purposes of disclosure, numerous changes exist in the details of procedures for accomplishing the desired results. These and other similar modifications will readily suggest themselves to those skilled in the art, and are intended to be encompassed within the scope of the present disclosure disclosed herein and the scope of the appended claims.
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