WO2001028659A1

WO2001028659A1 - Method and apparatus of removing sand from a producing gas well

Info

Publication number: WO2001028659A1
Application number: PCT/US2000/041371
Authority: WO
Inventors: James Randall Cobb; Paul L. Ammon
Original assignee: Inc TANK SYSTEMS
Current assignee: Inc TANK SYSTEMS
Priority date: 1999-10-19
Filing date: 2000-10-19
Publication date: 2001-04-26
Anticipated expiration: 2002-04-19

Abstract

The present invention provides a sand separator for use with gas wells that also produce sand, which separator removes the sand from the gas prior to delivery of the gas to a production line. The sand separator has a vertical tank with an internal cylinder forming an annulus therebetween. Sand is injected at a downward angle in the annulus to form a cyclone type of effect. At major wear points, wear plates are provided. The gas escapes from the top of the tank while the sand accumulates in the bottom thereof. A computer is provided that automatically opens a discharge valve and simultaneously lubricates the valve while the discharge valve is in the fully opened position. The discharge valve has extra power in the drive motor to provide for rapid opening or closing to minimize wear.

Description

Title: METHOD AND APPARATUS OF REMOVING SAND FROM

A PRODUCING GAS WELL

Inventors: James Randall Cobb, Paul L. Ammon

BACKGROUND OF THE INVENTION

This invention relates to the field of separators and, more particularly, to a method and apparatus for separating sand from gas being produced from a gas well prior to delivery to a pipeline.

DESCRIPTION OF THE PRIOR ART Many different types of separators have been designed in the past. However, most wells for producing hydrocarbons have a combination of oil and gas or * entirely oil . Not that many wells are strictly gas wells that also have a problem with sand being produced at the same time as the gas. In those unique circumstances, it is very important to be able to separate the sand from the high pressure gas that will be flowing from the well . In the past, various types of filter mechanisms have been used, but the filters have a tendency to clog and have to be changed periodically. The changing of the filters means the well has to be shut down and the area that contains the filter evacuated of gas prior to replacing the filter. The shutting down of the well, even for a short period of time, can be very expensive.

Another common method of separating solids from gas is to have a settling area where the solids can settle out from the gas. However, for a well that is continuously being produced, it is impractical to have a still area commonly referred to as a settling tank. There is always velocity to the gas as it flows from the producing well to the pipeline. Also a problem in the prior art is the abrasive nature of the sand flowing with the gas. Because of the Also a problem in the prior art is the abrasive nature of the sand flowing with the gas. Because of the high pressure force being exerted by the gas, the sand will, have a tendency to eat away most surfaces that it may impact against. Therefore, something has to be done to counteract the abrasive effect of the sand.

After the sand has been separated from the gas in the vessel that constitutes a portion of this invention, a further problem occurs due to the wear on the valve being actuated each time sand is removed from the vessel . In the prior art, there is not a good way to grease the valve. Also, the prior art does not show a way for rapid actuation of the valve which reduces the considerable wear during the opening and closing of the valve. SUMMARY OF THE INVENTION

It is an object of the present invention to provide a method and apparatus for separating sand from high pressure gas.

It is another object of the present invention to provide a method and apparatus for separating sand from a gas producing well prior to connection to a pipeline.

It is yet another object of the present invention to provide a separator for separating solid particles, such as sand, from a high pressure gas. It is yet another object of the present invention to provide an abrasive resistant separator that will resist wear at points of high impact during the process of separation of sand from high pressure gas.

It is yet another object of the present invention to provide a method and apparatus for periodically removing sand from a separator, which separator is located between a gas producing well and a pipeline. It is another object of the present invention to provide a method for lubrication of the valve used to remove sand from a separator.

It is still another object of the present invention to provide a method and apparatus to automatically lubricate a valve while the valve is in the open position.

It is still another object of the present invention to provide rapid actuation of a cutoff valve to minimize wear due to the flowing of sand or other abrasive particles therethrough.

It is yet another object of the present invention to provide a portable sand separator that may be used between producing gas wells and a pipeline to remove the sand from the gas.

The present invention is intended to be used on wells or fields that produce a combination of gas and sand, but very little oil or other liquids.

A self-contained sand separator may be mounted on skids. In the present embodiment, a cylindrical tank is mounted vertically with the gas from the well coming in at an upper side of the tank. Inside the upper half of the cylindrical tank is located an inner cylinder with a space or annulus being provided between the two cylinders. The combination of gas and sand is injected tangentially into the annulus formed between the two cylinders. A wear plate is provided on the outer cylinder and the inner cylinder to combat the abrasive wear of the sand. To provide some additional space for injection, an indentation is formed in the inner cylinder at the point of injection. To start a cyclone effect around the annulus between the two cylinders, the combination of gas and sand is injected at a downward angle of approximately 10°.

Once the combination of sand and gas reaches the bottom of the inner cylinder, the sand has a tendency to continue downward to the bottom of the outside cylinder with the gas rising up the middle of the inner cylinder. An outlet conduit for connecting to the gas line is at the top of the inner cylinder.

Periodically, as sand accumulates in the bottom of the outer cylinder, a valve that connects to the bottom of the tank is opened for a short period of time. The pressurized gas blows the sand out through the open valve. Typically, the gas is either discharged to atmosphere or flared off with the sand being deposited in a sand pit .

To solve problems with wear to the valve during opening or closing when discharging sand, a special motor to drive the valve has been included that opens and closes the valve very rapidly. This decreases the amount of wear on the valve. Also, to lubricate the valve, a lubricant is applied to the valve during the open cycle, which allows the lubricant to be spread over the entire mating surface of the rotating member of the valve.

By use of a computer control, the discharge valve can be periodically opened or closed based upon the amount of time it takes the particular well to produce enough sand to justify a discharge to the sand trap. It is better that the sand be discharged too often than sand flow into the main gas pipeline. The computer also controls the injection of grease on either side of the valve during the time the valve is open to ensure proper lubrication of the discharge valve. To prevent excessive wear as the sand and gas is injected into the tank, wear plates are provided on either side at the point of injection. To allow additional space, an indentation is provided in the inner annulus at the point of injection of the sand and gas. Once it is determined how much sand will be accumulated over a period of time, everything may be programmed into the computer and the system will then operate automatically. BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a pictorial perspective view of the present invention.

Fig. 2 is a vertical cross-sectional view of the upper half of the tank shown in Fig. 1. Fig. 3 is a sectional view of Fig. 2 taken along section lines 3-3.

Fig. 4 is a partial cross-sectional view of Fig. 3 taken along section lines 4-4.

Fig. 5 is a pictorial schematic of the system shown in Fig. 1.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to Fig.l of the drawings, there is shown a sand separator 10. The sand separator 10 has a generally cylindrical tank 12 arranged in a vertical position. An inlet pipe 14 connects from the wellhead (not shown) to inlet flange fitting 16 for the cylindrical tank 12. Cylindrical tank 12 has an outlet pipe 18 that connects to the gas pipeline (not shown) through gas valve 20.

At the bottom of the generally cylindrical tank 12 is a sand discharge pipe 22. Periodically, the sand discharge pipe 22 is opened by opening sand discharge valve 24. When sand discharge valve 24 is open, any sand accumulated inside of the generally cylindrical tank 12 will be discharged to a sand pit. Any gas combined with the sand at the time of discharge will be flared off or discharged to atmosphere. Referring now to Fig. 2 of the drawings, the upper half of the generally cylindrical tank 12 is shown in a vertical cross-sectional view. From the inlet flange fitting 16, a combination of gas and sand may flow through tank inlet conduit 26 into an annulus 28 formed by cylindrical tank 12 and inner cylinder 30. Inner cylinder 30 is held in position by brace bars 32 connecting between the inner cylinder 30 and the cylindrical tank 12. At the point the combination of gas and sand is injected into the annulus 28, there is a downward flare of the tank inlet conduit 26 of approximately 10°.

Referring to Figs. 3 and 4 in combination with Fig. 2, where like numerals will be used to designate like components, a better understanding of the injection of the combination of sand and gas under pressure into the annulus 28 can be understood. At the injection point 34, a wear plate 36 is located on the inside of the cylindrical tank 12 to combat the abrasive effect of sand being discharged under high pressure against the cylindrical tank 12. The wear plate 36 prevents wear of the generally cylindrical tank 12 to avoid rupture of the tank 12 under pressure. The wear plate 36 may be made from a wear resistant material, such as Stellite. Also, to accommodate the discharge of gas and sand under pressure inside of the annulus 28, the inner cylinder 30 has an inward indentation 38 to provide an enlarged annulus 28 at the injection point 34. Also, to prevent the inner cylinder 30 from wearing out due to the abrasive effect of the sand, an inner wear plate 40 covers the surface of the inward indentation 38 adjacent to the injection point 34. Again, inner wear plate 40 is made from an abrasive resistant material, such as

Stellite. In this manner, wear plate 36 and inner wear plate 40 will combat the abrasive effects of the sand as it is discharged inside of the annulus 28.

Because the sand and gas are being discharged into annulus 28 at a downward angle, they create a cyclone type of effect with the combination of gas and sand spiralmg downward m the annulus 28. As the combination of gas and sand clears the lower end 42 of the inner cylinder 30, it enters on expanded cross-sectional area. The inertia of the sand particles cause the sand particles to continue downward, but the gas slows down much more rapidly than the sand and reverses direction to go upward through the inside 44 of the inner cylinder 30 The rising gas flows out through the top of the generally cylindrical tank 12 through outlet connection 46 that connects to outlet pipe 18 through gas valve 20 (see Fig. 1) . As this process continues, sand accumulates m the bottom of cylindrical tank 12 while the gas flows through the outlet connection 46 to the gas pipeline. Referring now to Figs. 1 and 5 in combination, the operation of the present invention will be explained m further detail. Fig. 5 is a top schematic representation of what is shown m Fig. 1. A computer 48 is provided for the operation of the sand separator 10. The computer 48 controls the operation of the various valves, motors and pumps as will be described herembelow. The computer 48 also has a connection 60 to gas valve 20 that controls flow through the outlet pipe 18. By proper signal through connection 60 to gas valve 20, the gas valve 20 may be opened or closed. In normal operation, gas valve 20 is open and remains open unless there is a problem in the sand separator 10.

The computer 48 also controls the operation of sand discharge valve 24 by operating a drive motor 62 connected thereto by connection 64. The drive motor 62 (see Fig. 1) has extra power to quickly open or close valve 24. It is important that valve 24 open and close rapidly, because during the period of time the valve 24 is opening and closing, the valve has a tendency to wear excessively especially when there is a small opening so that flow is either (a) just initiated or (b) about to end. By rapidly opening or closing the valve 24, the wear during operation is minimized.

After valve 24 is fully opened, computer 48 turns ON pump 66 for a predetermined period of time through connection 68. When pump 66 is turned on for a short interval of time, pump 66 delivers grease from a grease tank 70, grease pump line 72, to grease lines 74 and 76. Simultaneously with the turning on of the pump 66, grease valves 78 and 80 are opened so that grease may be delivered to both sides of the ball (not shown) inside of sand discharge valve 24 when the ball is in the fully opened position. Operation of the grease valves 78 and 80 are provided by connections 82 and 84, respectively, to the computer 48.

A tank pressure monitor 86 is provided at the bleed valve 88 for the cylindrical tank 12. The tank pressure monitor 86 has connection 90 to the computer 48. If there is a large variation between the inlet pressure provided by pressure sensor 54 and the pressure sensed by tank pressure monitor 86, the computer 48 will know the cylindrical tank 12 is beginning to fill with sand. Hopefully, that condition would never occur, but if it does, the gas valve 20 can be shut off to avoid the danger of delivering sand to the production line.

Initially, when first utilizing the sand separator 10 for a particular well or production field, the operator would cycle the sand discharge valve 24 by pushing the manual override button 92 (see Fig. 1) . By timing how long it takes sand to accumulate inside of the cylindrical tank 12, the operator can tell how long to allow sand to accumulate inside of cylindrical tank 12 before cycling. This can be programmed into the computer 48 by any appropriate means, such as a keypad (not shown) or any other appropriate means.

During a typical cycle of the sand separator 10 after it has been set up and programmed, computer 48 will first turn ON drive motor 62, which will rapidly open sand discharge valve 24. When sand discharge valve 24 is fully opened, pump 66 will be activated for a short period of time and grease valves 78 and 80 opened. This will allow the delivery of grease from grease tank 70, grease pump line 72, and grease lines 74 and 76, to each side of the ball valve (not shown) contained inside of sand discharge valve 24 when it is in the fully opened position and has no pressure against the ball valve (not shown) . Only a short squirt of grease is necessary during each cycle. Therefore, the pump 66 is only ON for a short time interval, such as a second.

After sufficient time has passed so that the pressurized gas and sand coming into cylindrical tank 12 through inlet pipe 14 have forced the sand out through sand discharge pipe 22, sand discharge valve 24 and through sand pipe 94 to the sand pit (not shown) . The small amount of gas that escapes with the discharging of sand from sand separator 10 is either flared off or allowed to escape to atmosphere.

While it has not been stated previously, all of the controls, including the computer 48, pump 66, sand discharge valve 24, grease valve 78 and 80, and gas valve 20, are all electronically controlled through a solid state system that would have less danger of spark and hence a less chance of explosion in case there is a gas leak. Also, while the pump 66 as shown as being electrically driven to provide grease to the sand discharge valve 24, it could be driven by gas under pressure from the sand separator 10.

Although the invention has been described with reference to specific embodiments, this description is not meant to be construed in a limited sense. Various modifications of the disclosed embodiments, as well as alternative embodiments of the inventions will become apparent to persons skilled in the art upon the reference to the description of the invention. It is, therefore, contemplated that the appended claims will cover such modifications that fall within the scope of the invention.

Claims

We claim :

1. An apparatus for removing sand from a fluid stream of a gas from a producing well comprising: a vessel; a cylinder contained within said vessel; an inlet for introducing said fluid stream into said vessel; and an annulus disposed between said vessel inlet and a cylinder inlet whereby when said fluid stream is introduced through said annulus and into said cylinder a downward cyclone effect is created which causes said sand to continue downward while said gas continues to rise within said vessel thereby separating said sand from said gas.

2. The apparatus of Claim 1 further comprising a first outlet from said vessel for discharging said gas from said vessel .

3. The apparatus of Claim 2 further comprising a second outlet from said vessel for discharging said sand from said vessel .

4. The apparatus of Claim 3 further comprising a first wear plate at said inlet to combat the abrasive effect of said sand within said fluid stream.

5. The apparatus of Claim 4 wherein said introduction of said fluid stream through said annulus occurs at a downward angle.

6. The apparatus of Claim 5 wherein said cylinder inlet has an indentation to provide for enlargement of said annulus .

7. The apparatus of Claim 6 further comprising a second wear plate placed on said indentation to combat the abrasive effect of said sand within said fluid stream.

8. The apparatus of Claim 7 further comprising a computer connected to said apparatus to carry out operation of said apparatus .

9. The apparatus of Claim 8 further comprising a drive motor connected to said second outlet for opening and closing said second outlet .

10. The apparatus of Claim 9 further comprising a tank pressure monitor attached to said vessel to monitor the level of sand within said vessel .

11. The apparatus of Claim 10 further comprising a pump associated with said second outlet for delivering grease to a ball valve within said second outlet.

12. A method for removing sand from a fluid stream of a gas from a producing well utilizing the apparatus of

Claim 1 comprising the steps of : connecting said apparatus to said producing well; introducing said fluid stream of gas into a vessel of said apparatus; passing said fluid stream of gas into a cylinder of said apparatus; creating a cyclonic effect in said fluid stream; and separating said sand from said gas of said fluid stream.

13. The method of Claim 12 further comprising the step of removing said sand from said vessel following said separating step.

14. The method of Claim 13 further comprising the step of removing said gas from said vessel following said separating step.

15. The method of Claim 14 further comprising the step of greasing a motor controlling the step of removing said sand from said vessel .