The present application relates generally to gas well dewatering systems. More particularly, the present application relates to power and control logic configurations for positive displacement oscillating pumps used in gas well dewatering systems.
Hydrocarbons and other fluids are often contained within subterranean formations at elevated pressures. Wells drilled into these formations allow the elevated pressure within the formation to force the fluids to the surface. However, in low pressure formations, or when the formation pressure has diminished, the formation pressure may be insufficient to force the fluids to the surface. In these cases, a positive displacement pump, such as a piston pump, can be installed to provide the required pressure to produce the fluids.
The function of pumping systems in gas wells is to produce liquid, generally water, that enters the wellbore naturally with the gas. This is necessary only on low flow rate gas wells. In high flow rate gas wells, the velocity of the gas is sufficient that it carries the water to surface. In low flow rate wells, the water accumulates in the wellbore and restricts the flow of gas. By pumping out the water, the pump allows the well to flow at a higher gas rate, and this additional produced gas, which eventually is related to additional revenue, pays for the pumping unit.
The use of a retrievable pumping system in a low-flow rate gas well is subject to several economic restrictions. One principal restriction is that the pumping system must be inexpensive to replace, otherwise the cost of installing or replacing the unit overwhelms the additional revenue from an increase in the low flow rate of gas.
The present disclosure recognizes that it is desirable to provide a gas well dewatering system that is of sufficiently small size that it can be deployed and operated in a relatively crowded well environment. It is recognized as desirable to provide such a system that is durable and yet relatively inexpensive to manufacture, operate and repair.
In one example, a gas well dewatering system is configured to pump well fluid from a reservoir to an outlet for discharge from a well. The system includes a reservoir configured to contain hydraulic, lubricating fluid; an electric motor configured to receive fluid from the reservoir for lubrication; a hydraulic pump powered by the electric motor, the hydraulic pump configured to receive fluid from the reservoir and pump said fluid into a hydraulic circuit; and a positive displacement pump powered by the hydraulic pump and configured to pump fluid from the reservoir to the outlet. Advantageously, the electric motor and hydraulic pump receive the same fluid from the reservoir for lubrication and for pumping into the hydraulic circuit, respectively. According to this arrangement, it is possible for the motor and hydraulic pump to rotate in one direction while the positive displacement pump oscillates to pump fluid from the well.
In another example, a switching device is connected to the hydraulic circuit and is switchable between a first position wherein fluid pressure in the hydraulic circuit is applied to the first side of the piston pump to move the piston pump in a first direction and a second position wherein fluid pressure in the circuit is applied to the second side of the piston pump to move the piston pump in a second, opposite direction. The movement of the piston pump in the first direction causes corresponding movement of the switching device into the second position. Movement of the piston pump in the second direction causes corresponding movement of the switching device into the first position. In a preferred example, the piston pump and the switching device are coupled together.
In another example, a first hydraulic circuit is configured to convey fluid pressure from the hydraulic pump to power the piston pump and a second hydraulic circuit is configured to convey fluid pressure to a switching device switchable between a first position wherein fluid pressure in the first hydraulic circuit is applied to the first side of the piston pump to move the piston pump in the first direction and a second position wherein fluid pressure in the first hydraulic circuit is applied to the second side of the piston pump to move the piston pump in the second direction. Movement of the piston pump in the first direction causes the switching device to switch to the second position. Movement of the piston pump in the second direction causes the switching device to switch to the second position.
The best mode of practicing the invention is described hereinbelow with reference to the following drawing figures.
In the following description, certain terms have been used for brevity, clearness, and understanding. No unnecessary limitations are to be implied therefrom beyond the requirement of the prior art because such terms are used for descriptive purposes only and are intended to be broadly construed. The different systems described herein may be used alone or in combination with other systems. It is to be expected that various equivalents, alternatives, and modifications are possible within the scope of the appended claims.
A fluid reservoir 22 contains dual purpose fluid suitable for lubrication and as a hydraulic fluid. Fluid from the reservoir 22 is supplied to the motor 12 for lubrication and then via conduits 24 to the hydraulic pump 20. The hydraulic pump 20 is configured to pump the fluid into a hydraulic circuit 26 to power oscillating movement of a positive displacement pump 28. In the example shown, the positive displacement pump 28 is a dual acting piston pump and the hydraulic circuit 26 conveys fluid pressure from the hydraulic pump 20 selectively to first 30 and second 32 sides of the dual acting piston pump 28.
A switching device 34 is connected to the hydraulic circuit 26 and configured to switch between a first position, shown in
In the example shown, the switching device 34 has a switch body 40 that is coupled to an extension rod 42 extending from the dual acting piston pump 28. The switch body 40 has a first through-bore 44 configured to align with the hydraulic circuit 26 when the switching device 34 is in the first position shown in
The extension rod 42 which extends from the dual acting piston pump 28 includes a top flange 54 and a bottom flange 56 configured to engage with the top side 58 and bottom side 60 of the switch body 40, respectively. Dynamic magnets 62, 64 are coupled to the switch body 40 and stationary magnets 66, 68 are coupled to, for example, a housing associated with the system 10. The stationary magnets 66, 68 are spaced apart and respectively configured to attract at least one of the dynamic magnets 62, 64 and thereby cause the switch body 40 to firmly register into one of the first and second positions shown in
During operation, electric power is provided to motor 12, which causes rotor 16 to rotate and provide power to hydraulic pump 20. Fluid contained within reservoir 22 is conveyed to lubricate motor 12 during operation. Fluid continues through motor 12 (arrows 51) and is provided to hydraulic pump 20 wherein it is pumped into hydraulic circuit 26 (arrow 53) at a predetermined pressure sufficient to drive reciprocal motion of dual acting piston pump 28. Switching device 34 switches between the first position shown in
While in the second position, fluid pressure from the hydraulic pump 20 is applied to the second side 32 of the dual acting piston pump 28 via the hydraulic circuit 26 and specifically through the through-bore 46. Application of pressure to the second side 32 of the dual acting piston pump 28 (arrows 61, 63) causes the dual acting piston pump 28 to move in the second direction 38. During said movement, the bottom flange 56 engages with the bottom side 60 of the switch body 40 with sufficient pressure to overcome the attractive force between the magnets 64, 68, thus dislodging the switch body 40 from the second position and moving the switch body 40 in the second direction 38 such that the magnets 62, 66 are brought into proximity with each other. Attractive force between the respective magnets 62, 66 causes the switch body 40 to snap into the first position, shown in
The above process is repeated in succession and the dual acting piston pump 28 is powered to draw fluid from a well reservoir (not shown) and pump said fluid to an outlet (not shown) for discharge from the well.
In the example shown, a first switch 116 is disposed in the second hydraulic circuit 108. The first switch 116 is switchable between an open position (
In the example shown, the piston pump 100 includes upper and lower piston heads 120, 122. An upper magnet 124 is coupled to the upper piston head 120 and a lower magnet 126 is coupled to the lower piston head 122. In this example, the first switch 116 includes a first magnet 128, the second switch 118 includes a second magnet 130. The first switch 116 is biased into the closed position by an elastic element 132. The second switch 118 is also biased into the closed position by an elastic element 134. The upper magnet 124 is located proximate to the second magnet 130 when the piston moves in the first direction 102. The lower magnet 126 is located proximate the first magnet 128 when the piston moves in the second direction 104. Upper magnet 124 and second magnet 130 repulse each other. Lower magnet 126 and first magnet 128 repulse each other.
The sliding spool valve or switching device 110 has first and second passages 136, 138. The first passage 136 aligns with the first hydraulic circuit 106 to connect the hydraulic pump to the first side 112 of the piston pump 100 when the switching device 110 is in the first position (
During operation, hydraulic fluid pressure is provided to the hydraulic circuits 106, 108. When the piston pump 100 is in the first position (
The above-mentioned process occurs repeatedly allowing for oscillating movement of the piston pump 100 along directions 102 and 104.