CA2946557A1

CA2946557A1 - Pump for low pressure casing gas

Info

Publication number: CA2946557A1
Application number: CA2946557A
Authority: CA
Inventors: Wright Hal
Original assignee: Individual
Current assignee: Individual
Priority date: 2016-10-27
Filing date: 2016-10-27
Publication date: 2018-04-27

Abstract

A system for pumping oil from an oil well comprises a well casing extending from a ground surface to an oil bearing formation, the well casing containing oil and casing gas.
An oil pump is driven by an oil pump engine to pump oil from the well easing.
A gas reservoir is connected to the oil pump engine to supply easing gas to fuel the oil pump engine, and a gas pump is operative to draw casing gas from the well casing and pump the casing gas into the gas reservoir. A reservoir pressure of casing gas in the gas reservoir is greater than a casing pressure of easing gas in the well easing.

Description

PUMP FOR LOW PRESSURE CASING GAS
This disclosure relates to the field of oil wells and in particular a pump system for increasing the pressure of casing gas in an oil well to a usable pressure.
BACKGROUND
Oil wells typically comprise a well casing extending down from the surface to an oil bearing formation. In addition to oil, there is typically as well a significant amount of natural gas drawn from the formation and present in the casing. It is desirable to use this gas to operate various surface equipment, such as to drive the pump engine that draws oil from the well, to operate burners in cold weather operations, and so forth.
It is often the case that the casing gas is at a pressure that is not sufficient to satisfactorily operate the desired equipment, and so it may be necessary to bring in another fuel, such as propane, to operate the equipment, significantly increasing the cost of operating the well. Also where casing gas pressure is low, the casing gas is commonly simply vented to the atmosphere, which is a waste of resources and environmentally undesirable.
SUMMARY OF THE INVENTION
The present disclosure provides a natural gas pump system for oil well sites that overcomes problems in the prior art.
The present disclosure provides a system for pumping oil from an oil well. The system comprises a well casing extending from a ground surface to an oil bearing formation, the well casing containing oil and casing gas. An oil pump is driven by an oil pump engine and is operative to pump oil from the well casing. A gas reservoir is connected to the oil pump engine to supply casing gas to fuel the oil pump engine, and a gas pump is 1830247v1 operative to draw casing gas from the well casing and pump the casing gas into the gas reservoir. A reservoir pressure of casing gas in the gas reservoir is greater than a casing pressure of casing gas in the well casing.
Commonly in such oil wells as are contemplated for use with the system of the present disclosure while the pressure of the casing gas in the casing is too low for practical use, the volume of casing gas flowing from the formation is quite sufficient, when pressurized by the disclosed system, to operate the equipment for significant lengths of time, often as long as the oil production warrants keeping the well in production.
It is contemplated that lowering the pressure of the casing gas in the well casing by sucking the gas out may also somewhat increase the flow of oil from the formation and so may increase production from the well.
DESCRIPTION OF THE DRAWINGS
While the invention is claimed in the concluding portions hereof, preferred embodiments are provided in the accompanying detailed description which may be best understood in conjunction with the accompanying diagrams where like parts in each of the several diagrams are labeled with like numbers, and where:
Fig. 1 is a schematic side view of an embodiment of a system of the present disclosure;
Fig. 2 is a schematic cut-away side view of a gas pump apparatus for use with the embodiment of Fig. 1 showing the piston rod moving toward the left position;
Fig. 3 is a schematic cut-away side view of the gas pump apparatus of Fig. 2 showing the piston rod moving toward the right position.

2 1830247v1 DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS
Fig. 1 schematically illustrates an embodiment of a system 1 of the present disclosure for pumping oil from an oil well. The system 1 comprises a well casing 3 extending from a ground surface 5 to an oil bearing formation 7. The formation 7 contains both oil and natural gas which enter the well casing 3. The natural gas is herein referred to as casing gas, and the well casing 3 contains oil represented by the circles 9 and casing gas represented by the crosses 11. After flowing from the formation 7 the oil 9 pools in the bottom portion of the casing 3 and an oil pump 13 driven by an oil pump engine 15 is operative to pump the oil 9 from the well casing 3 into a storage container 17, or, depending on the facilities available, into a pipeline.
The casing gas 11 rises to the upper portion of the casing 3 and commonly has sufficient pressure that same can be directed from the top of the casing 3 to the oil pump engine 15 to be used as fuel to power the engine 15, and also to power burners or like surface equipment that might be required. Often the pressure of the casing gas 11 in the casing 3 drops to a level where it is not sufficient to flow properly to the engine 15 or other equipment, and a propane tank must be brought in to provide fuel.
In the present system, a gas pump 19 is operative to draw casing gas 11 from the well casing 3 and pump the casing gas 11 into a gas reservoir 21 which is connected to the oil pump engine 15 to supply casing gas 11 to fuel the oil pump engine 15. The gas pump 19 increases the pressure of the casing gas 11 in the gas reservoir 21 to a reservoir pressure that is significantly greater than the casing pressure of casing gas 11 in the well casing 3, and that is sufficient to provide pressurized fuel to the oil pump engine 15, and any other required equipment.
Figs. 2 and 3 schematically illustrate a gas pump 19 for use with the apparatus 1. The illustrated gas pump 19 comprises a barrel 23 with a substantially cylindrical barrel wall

3 1830247v1 25 and right and left end walls 27R, 27L closing corresponding right and left ends of the barrel 23. Right and left gas ports 29R, 29L are defined in corresponding right and left end portions of the barrel 23. In the illustrated gas pump 19 the right and left gas ports 29R, 29L are defined in corresponding right and left end portions of the cylindrical barrel wall 25, however same could also be defined in the right and left end walls 27R, 27L as indicated by alternate gas ports 29' in Fig. 2.
A partition wall 31 extends across a mid-point of the barrel 23 to divide the barrel into a right chamber 33R and a left chamber 33L. A piston rod 35 extends along a longitudinal axis LA of the barrel 23 through a rod hole 37 in the partition wall 31 and is sealed to the rod hole 37 such that the piston rod 35 is free to slide in the rod hole 37.
Right and left pistons 39R, 39L are attached to corresponding right and left ends of the piston rod 35 and are configured to slide in sealing engagement along inner walls 41 of the corresponding chambers 33.
A gas input conduit 43 is connected at a first end 43A thereof to an interior of the well casing 3 and a gas output conduit 45 connected at a first end 45 thereof to an interior of the gas reservoir. Right and left gas port valves 47R, 47L are connected to the corresponding right and left gas ports 29R, 29L, and each gas port valve 47 is operative in a first position to connect the corresponding gas port 29 to the gas input conduit 43 and is operative in a second position to connect the corresponding gas port 29 to the gas output conduit 45. Fig. 2 schematically illustrates the right gas port valve 47R in the first position and the left gas port valve 47L in the second position.
A piston rod drive 49 is operative to move the piston rod 35 and attached pistons 39 alternately right and left and a gas valve control 51 is operative to synchronize movement of the right and left gas port valves 47R, 47L between the first and second positions such that casing gas 11 is drawn through the gas input conduit 43 from the casing 3 and expelled through the gas output conduit 45 into the gas reservoir 21. A check valve 53 is

4 1830247v1 operative to allow gas to flow from the gas output conduit 45 into the gas reservoir 21 and operative to prevent gas from flowing out of the gas reservoir 21 through the gas output conduit 45.
The piston rod 35 is movable from a right position shown by the dotted lines in Fig. 3, where an outer face 55R of the right piston 39R is adjacent to the right gas port 29R and the right piston 39R is between the right gas port 29R and the partition wall 31, to a left position shown by the dotted lines in Fig. 2, where an outer face 55L of the left piston 39L is adjacent to the left gas port 29L and the left piston 39L is between the left gas port 29L and the partition wall 31.
The right gas valve 47R is in the first position and the left gas valve 47L is in the second position when the piston rod 35 is moving toward the left position in direction PL as illustrated in Fig. 2, and the right gas valve 47R is in the second position and the left gas valve 47L is in the first position when the piston rod 35 is moving toward the right position in direction PR as illustrated in Fig. 3.
It can be seen that as the piston rod 35 moves to the left in direction PL as shown in Fig.
2, gas is drawn from the casing 3 through the gas input conduit 43, the right gas port valve 47R, which is in the first position, and the right gas port 29R into the right chamber 33R, and any gas in the left chamber 33L is forced out through the left gas port 29L and directed by the left gas port valve 47L, which is in the second position, to the gas output conduit 45 and into the gas reservoir 21. Significant reservoir gas pressure can be attained in the gas reservoir 21, depending on the relative volume of spaces between the outer faces 55 of the pistons 39 and the end walls 27 when the pistons 39 are in the right and left positions. Typically a gas pump control 57 is connected to a pressure sensor 59 on the gas reservoir 21. The gas pump control 57 is operative to stop the gas pump 19 when the reservoir pressure reaches a selected maximum reservoir pressure, and to start

5 1830247v1 the gas pump 19 when the reservoir pressure reaches a selected minimum reservoir pressure.
In the illustrated gas pump 19, hydraulic fluid substantially fills inner portions 61R, 61L
of the right and left chambers 33R, 33L between inner faces 63R, 63L of the corresponding right and left pistons 39R, 39L and the partition wall 31. The piston rod drive 49 comprises a hydraulic fluid pump 65 connected to a right fluid port 67R defined in the cylindrical barrel wall 25 of the right chamber 33R adjacent to the partition wall 31 and to a left fluid port 67L defined in the cylindrical barrel wall 25 of the left chamber 33R adjacent to the partition wall.
The hydraulic fluid pump 65 is operative to draw hydraulic fluid from the inner portion 61L of the left chamber 33L and pump the hydraulic fluid into the inner portion 61R of the right chamber 33R to move the piston rod 35 in direction PR toward the right position, and operative to draw hydraulic fluid from the inner portion 61R of the right chamber 33R and pump the hydraulic fluid into the inner portion 61L of the left chamber 33L to move the piston rod 35 in direction PL toward the left position. A pump control 69 controls the flow of hydraulic fluid, and also is connected to the gas pump control 57 to stop and start movement of the piston rod 35 as required.
In a typical system of the present disclosure the hydraulic pump 65 is also powered by casing gas from the gas reservoir 21, and commonly by the oil pump engine 15.
Thus fuel for all equipment is derived from the casing gas.
Commonly in such oil wells as are contemplated for use with the system 1 of the present disclosure while the pressure of the casing gas 11 in the casing 3 is too low for practical use, the volume of casing gas flowing from the formation 7 is quite sufficient, when pressurized by the disclosed system 1, to operate the equipment for significant lengths of time, often as long as the oil production warrants keeping the well in production.

6 1830247v1 A further benefit of the system 1 of the present disclosure may be found where lowering the pressure of the casing gas 11 in the well casing 3 somewhat increases the flow of oil from the formation and so increases production from the well.
The foregoing is considered as illustrative only of the principles of the invention.
Further, since numerous changes and modifications will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly, all such suitable changes or modifications in structure or operation which may be resorted to are intended to fall within the scope of the claimed invention.

7 1830247v1

Claims

What is claimed is:

1. An system for pumping oil from an oil well, the system comprising:
a well casing extending from a ground surface to an oil bearing formation, the well casing containing oil and casing gas;
an oil pump driven by an oil pump engine and operative to pump oil from the well casing;
a gas reservoir connected to the oil pump engine to supply casing gas to fuel the oil pump engine;
a gas pump operative to draw casing gas from the well casing and pump the casing gas into the gas reservoir; and wherein a reservoir pressure of casing gas in the gas reservoir is greater than a casing pressure of casing gas in the well casing.

2. The system of claim 1 wherein the gas pump comprises:
a barrel with a substantially cylindrical barrel wall and right and left end walls closing corresponding right and left ends of the barrel;
right and left gas ports defined in corresponding right and left end portions of the barrel, a partition wall extending across a mid-point of the barrel to divide the ban-el into a right chamber and a left chamber;
a piston rod extending along a longitudinal axis of the barrel through a rod hole in the partition wall and sealed to the rod hole such that the piston rod is free to slide in the rod hole;
right and left pistons attached to corresponding right and left ends of the piston rod and configured to slide in sealing engagement along inner walls of the corresponding right and left chambers;
a gas input conduit connected at a first end thereof to an interior of the well casing;
a gas output conduit connected at a first end thereof to an interior of the gas reservoir;
right and left gas port valves connected to the corresponding right and left gas ports, wherein each gas port valve is operative in a first position to connect the corresponding gas port to the gas input conduit and is operative in a second position to connect the corresponding gas port to the gas output conduit;
a piston rod drive operative to move the piston rod and attached pistons alternately right and left and a gas valve control operative to synchronize movement of the right and left gas port valves between the first and second positions such that casing gas is drawn through the gas input conduit from the casing and expelled through the gas output conduit into the gas reservoir.

3. The system of claim 2 wherein the piston rod is movable from a right position, where an outer face of the right piston is adjacent to the right gas port and the right piston is between the right gas port and the partition wall, to a left position, where an outer face of the left piston is adjacent to the left gas port and the left piston is between the left gas port and the partition wall.

4. The system of claim 3 wherein the right gas valve is in the first position and the left gas valve is in the second position when the piston rod is moving toward the left position, and wherein the right gas valve is in the second position and the left gas valve is in the first position when the piston rod is moving toward the right position.

5. The system of claim 4 wherein hydraulic fluid substantially fills inner portions of the right and left chambers between inner faces of the corresponding right and left pistons and the partition wall, and wherein the piston rod drive comprises a hydraulic fluid pump operative to draw hydraulic fluid from the inner portion of the left chamber and pump the hydraulic fluid into the inner portion of the right chamber to move the piston rod toward the right position, and operative to draw hydraulic fluid from the inner portion of the right chamber and pump the hydraulic fluid into the inner portion of the left chamber to move the piston rod toward the left position.

6. The system of claim 5 wherein the hydraulic pump is connected to a right fluid port defined in the cylindrical barrel wall of the right chamber adjacent to the partition wall and to a left fluid port defined in the cylindrical barrel wall of the left chamber adjacent to the partition wall.

7 The system of claim 6 wherein the hydraulic pump is powered by casing gas from the gas reservoir.

8. The system of claim 7 wherein the hydraulic pump is driven by the oil pump engine

9. The system of any one of claims 2 ¨ 8 comprising a check valve operative to allow gas to flow from the gas output conduit into the gas reservoir and operative to prevent gas from flowing out of the gas reservoir through the gas output conduit.

10. The system of any one of claims 2 ¨ 9 wherein the right and left gas ports are defined in corresponding right and left end walls of the barrel.

11. The system of any one of claims 2 ¨ 9 wherein the right and left gas ports are defined in corresponding right and left end portions of the cylindrical barrel wall

12. The system of any one of claims 1 ¨ 11 comprising a gas pump control connected to a pressure sensor on the gas reservoir, the gas pump control operative to stop the gas pump when the reservoir pressure reaches a selected maximum reservoir pressure.

13. The system of claim 12 wherein the gas pump control is operative to start the gas pump when the reservoir pressure reaches a selected minimum reservoir pressure.