Lease Pumper's Handbook Published
by the Commission on Marginally Producing
Oil and Gas Wells of Oklahoma, First
Edition 2003 Written by Leslie V. Langston
Table of Contents Introductions A. Cover
Sheet Book Title B. Publishing Information
First Edition, 2003
The Lease Pumper's Handbook
Published by the Commission on Marginally Producing Oil and Gas Wells of Oklahoma, First Edition 2003 Written by Leslie V. Langston Table of Contents Introductions A. Cover Sheet Book Title B. Publishing Information First Edition, 2003
Written by Leslie V. Langston
Publishing Information. First Edition, 2003. C. Foreword. Rick Chapman, Executive Director (1996-2000) Commission on Marginally Producing Oil and Gas Wells, State of Oklahoma. D. Dedication. John A. Taylor, Chairman (1992-1998) Commission on Marginally Producing Oil And Gas Wells, State of Oklahoma. E. Author’s Introduction. Leslie V. Langston, Author, First Edition F. Commission Introduction. Liz Fajen, Executive Director, Commission on Marginally Producing Oil and Gas Wells, State of Oklahoma.
The Lease Pumper’s Handbook
Flowing Wells and Plunger Lift
The use of plunger lifts has increased dramatically during the past decade and has led to increased oil production. Improved technology, computers, better equipment dependability, and additional services have contributed to this increased use. Plunger lift is available in complex computer controlled models and simple basic systems. This section discusses the use of plunger lift.
B-1. The Cost of Changing a Well to Mechanical Lift.
Once the bottomhole pressure in a well is no longer adequate to cause it to flow, the operator must determine if it will be worthwhile to install a lift system. The initial costs can be substantial, even with a minimum installation. The actual transition of a well from flowing to pumping requires: · A well servicing crew to rig up and remove the packer, possibly install a hold-down in the casing, reinstall the tubing string, and run the rod string. · The purchase of a downhole pump. · The purchase of a string of rods. · The purchase of a pumping unit. · Construct a base and have it set. · Install and line up the pumping unit on the base and over the hole. · Remove the Christmas tree and rebuild the wellhead (Figure 1). · Provide a source of power to run the pump either by running electricity to the location or providing an engine and a source of fuel. An electrical setup will require an automatic control and an electric motor. A engine may operate on gas from the well or from stored fuels. Figure 1. Two typical wellhead designs for wells using plunger lift.
B-2. How Plunger LiftWorks.
A wing valve control on the wellhead closes the flow line to the tank battery, and this stops the flow of fluids up through the tubing to the tank battery. The bumper housing and catcher on the wellhead release a free falling gas lift plunger, which drops by gravity from the wellhead downward through the tubing. An open valve in the plunger allows fluids from below to pass through it as it falls. Gravity continues to make the plunger fall all the way to the bottom of the well. When the gas lift plunger strikes bottom, it makes contact with a footpiece spring, closing the valve. Downhole pressure continues to build up and also allows oil and water to accumulate on top of the plunger. After a specified time or tubing pressure level, the controller causes a flow line motor valve at the surface on the wellhead to open, allowing the gas and fluids accumulated in the tubing to flow toward the tank battery. The differential pressure change across the plunger lift valve causes the plunger to travel toward the surface at a rate of 500- 1,000 feet per minute, depending on adjustable choke settings, fluid loads, and bottomhole pressure. As the plunger moves upward pushed by the built-up formation pressure below it, the fluid above the plunger is lifted to the surface. On oil wells and weak gas wells, the arrival of the plunger at the surface activates a magnetically controlled sensor that immediately closes the flow line motor valve, conserving tubing and formation gas pressure until the next cycle. The catcher in the bumper housing releases the plunger. The plunger again starts falling, and the cycle begins again, repeating itself as often as the settings and pressures allow.
Figure 2. Plunger lift system. (courtesy of Production Control Services, Inc.)
B-3. Benefits of Plunger Lift.
The benefits of converting a marginally producing flowing well to a lift system can be enormous in many situations. Some of reasons for choosing a plunger lift system over other type include:
· Reduce lifting costs.
· Conserve formation gas pressure.
· Increase production.
· Produce with a low casing pressure. · Prevent water buildup.
· Avoid gas-locked pump problems.
· Reduce gas/oil ratio.
· Scrape tubing paraffin.
· Improve ease of operation.
· Use pneumatic or electronic controllers.
· Reduce installation and operating costs.
Note: When a plunger system is installed, a gauge ring of the same size as the proposed mandrel to be used in the plunger lift system should be run down the well. This will identify any problems that could prevent the plunger from free-falling through the tubing. Reduce lifting costs. Plunger lift has a lower lifting cost than most other systems of artificial lift. The well itself supplies the gas pressure needed for operation. The more complex electrical systems require very little power and this can be supplied with a solar panel. Conserve formation gas pressure. As quickly as the plunger arrives at the bumper housing at the surface, the flow line is shut in, stopping any additional formation gas from flowing to the tank battery and into the gas system. The gas needs to remain in the formation as long as possible to drive additional oil to the well bore in the future. When the formation gas is gone, the well will stop producing. The conservation of formation gas is one of the outstanding benefits of plunger lift, and no other lift system can offer this advantage. Increase production. Through productivity testing where the well is produced under many different time limits and situations, the most productive parameters can be determined and followed to result in the highest possible production. By reducing the column of fluid lifted and lifting it more often, production can usually be increased. Produce with a low casing pressure. Plunger lift allows a well to continue to flow with less than 100 pounds of casing pressure. The plunger will stay on bottom until sufficient lifting pressure has built up. The signal to open the flow line valve will be transmitted to the surface through the casing pressure. Prevent water buildup. When a well is flowing by choke control and the lifting pressure has become so marginal that the well will barely flow, the produced water, being heavier than oil, will have a tendency to allow the oil and gas to flow with the water falling back to the bottom of the hole. This water buildup will cause the well to become waterlogged and stop flowing until the water has been blown or swabbed off. With plunger lift the water is produced along with the oil every time the plunger makes a trip to the surface, and water does not accumulate at the bottom of the well. Avoid gas-locked pump problems. When a well with high gas production is put on a mechanical pumping unit, the pump can develop a tendency to gas lock and stop the well from producing. The plunger lift system does not have this problem. Reduce gas/oil ratio. In some fields, oil production is regulated by the amount of gas that is produced with each barrel of oil. The goal is to retain as much gas in the reservoir as possible to push oil to the wellbore. Some fields have allowables adjusted to reflect the amount of gas produced daily. Plunger lift does well in reducing gas production, which results in increased oil allowables. This will dramatically extend the production life of the reservoir and the amount of oil produced. Scrape tubing paraffin. While the plunger is traveling up the tubing each cycle, it acts as an excellent wiper to remove paraffin that may cling to the tubing. Paraffin leaves the formation suspended in the oil. As the wellbore temperature drops, the paraffin comes out of solution and is deposited in the tubing. The plunger can also remove scale that is still soft. Improve ease of operation. The basic operation of plunger lift systems is simple. Even the more complex systems are becoming easier to operate with new developments in technology. Advances in personal computers and electronic miniaturization allow controllers to perform functions that were not possible a few years ago, almost to the point of making decisions. Use pneumatic or electronic controllers. Automatic controls allow the pumping time of the well to be precisely controlled to allow the most efficient use of energy and to reduce the loss of gas. Reduce installation and operating costs. Plunger systems generally cost less to install, operate, and maintain than other lift systems. B-4. Plunger Selection. There are five main types of plungers: solid, brush, metal pad, wobble washer, and flexible (Figure 3).
Figure 3. Some of the types of plungers available. (courtesy of McLean & Sons, Inc.)
Solid. The solid plunger is a solid steel cylinder with a smooth or grooved surface. Gas passing around the plunger during its trip upward must have a velocity much greater than the plunger and liquid load. The gas passing the plunger wipes the tubing clean of liquids and reduces liquid fallback. Brush. A brush plunger consists of a mandrel and a brush segment that may or may not be replaceable. The brush segment is oversized with respect to the tubing internal diameter, and this characteristic creates the sealing mechanism. Brush plungers are particularly good for wells that suffer from sand flowback or tubing imperfections. 5B-5 Metal pad. The metal pad plunger has several spring-activated metal pads that conform to the internal tubing diameter. These plungers may have one or several concentric sets of pads along the body arranged in various patterns. Pad plungers provide the highest level of mechanical seal when properly sized. Wobble washer. The wobble washer plunger is designed to keep tubing free of paraffin, salt, and scale. It is constructed of shifting steel rings or washers mounted along a solid mandrel. The washers wipe the tubing clean, removing the unwanted product before it has a chance to crystallize. Flexible. New on the market are plungers built with a flexible mandrel for deviated hole and coiled tubing applications. Articulated cup and brush plungers are available with this new design feature. These flexible plungers range in size from ¾ inch to 2-7/8 inches. Many times a flexible plunger will run in a standard tubing string that has bends or crimps, reducing the need to pull tubing. Clean-up plungers. Among the plungers pictured in Figure 3 is a clean-up free-fall plunger with a fishing neck. These are frequently used to handle formation sand, frac sand, scale, and so forth. The clean-up plunger is usually replaced with the expanding blade plunger when the well has cleaned itself. If the plunger should stick in the tubing during the clean-up procedure, the fishing neck makes it easier to retrieve.
B-5. Bumper Housings and Catcher.
The bumper housing and catcher perform several functions. The bumper provides a cushioned bumper to stop the plunger from moving as it reaches the top of its travel and enters the housing. The housing also helps provide lubrication. The arrival unit recognizes that the plunger has arrived at the top of its travel and sends a signal to the control panel, or controller, which sends a signal to the flowline valve, causing it to close. The lease pumper can engage the catcher, which will catch the plunger the next time that it arrives at the surface. This will permit the plunger to be removed, inspected, serviced, and placed back into operation at the pumper’s convenience.
Figure 4. Common components of a plunger lift system: (left to right) a controller, plunger, bumper, and housing with lubricator and electronic sensor. (courtesy of Production Control Services, Inc.)
Most controllers (Figure 5) can be operated with time control or with pressure cycles. Timers may be set for straight timed shut-in or operated with high/low pressure measurements through the use of flow line throttle pilot pressure and a differential pressure switch. With this type of flexibility available to the lease pumper, plunger lift can be an ideal method for operating wells. By reducing the loss of formation gas, a great deal of additional oil may be recovered.
Figure 5. An electronic controller. (courtesy of Production Control Services, Inc.)
B-7. Plunger Lift Configurations.
It should be evident from this section that plunger lift systems can be configured in a number of ways to meet the needs of a specific well. By matching the components and the controller settings to conditions of an individual well, the lease pumper can come close to maximizing the efficiency of the well. Note the plunger lift shown in Figure 6. A full opening gate valve is located just under the oil well bumper housing and arrival unit and catcher. This particular installation was powered by a solar panel located to the right, just out of the picture. The casing valve has a pressure gauge and connection providing pressure to the controller. Just to the right of the bumper housing is a line that controls the shut-in of the flow line.
Figure 6. A plunger lift wellhead showing the bumper housing, arrival unit, catcher, and controller. (courtesy of McLean & Sons, Inc.)
Plunger lift is one method of artificial lift. Other techniques are presented later in this handbook, but many of the objectives and considerations described here are applicable to other lift methods as well.