Ingenieria

5B-1 The Lease Pumper’s Handbook Chapter 5 Flowing Wells and Plunger Lift Section B 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 computercontrolledmodels 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 wellfrom 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 usingplunger lift.

5B-2 B-2. How Plunger Lift Works. 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 allowsfluids 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, thecontroller 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 5001,000 feet per minute, depending on adjustable choke settings, fluid loads, and bottomhole pressure. As theplunger 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 housingreleases 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

5B-3 reasons forchoosing 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....