Pumping Flumping Sucker Rod Lifted Wells
James Harris
H & H Well Services, LLC
Abstract
Flumping means that the sucker rod lifted well is flowing fluids to the surface up the casing annulus, plus at the same time fluids are being pumped to the surface up the tubing. Oil wells flump because there is either high producing bottom hole pressure or because a high rate of gas is flowing up the casing annulus and lightening the oil column above the pump intake. Once flow is stabilized by using backpressure on tubing and/maybe casing, and producing buttonhole pressure is reduced, then the casing pressure can be gradually reduced to see if the well also flow in a stabilized condition up casing while well is pumped up tubing. Often the operator must maintain high tubing pressure with a back-pressure valve or the wells will blow all of the liquid out of the tubing and stop pumping. These types of wells often continue to flump for a long time period until they are produced to a low producing bottomhole pressure or the gas rate decreases.
If no backpressure is applied to the casing, then all of the fluid in the casing annulus may unload. This type of flumping can cause the pump to be starved and may result in gas locking of the pump.
Usually the only way to preventflumping up the tubing is through use of a back-pressure valve on the tubing. The added tubing backpressure puts more delta pressure on the pump and requires more horsepower. Flumpingup the tubing can result in damage to the sucker rod equipment and results in reduced run life due to rod-on-tubing wear. A quick test to determine if a backpressure valve will help is to close the tubing flowline valve and see if the wells will pump up to approximately 500 psi on the well head, if so, then slightly crack valve and see if pumping continues for a few hours. If the well continues to pump, then the tubing can be controlled through use of a backpressure valve.
If flumping is due to free gas in the pump, then the best remedy is to try to get the gas out of the pump. If a down hole gas separator is used then the casing must be open to the flow line and the gas must be vented at the surface. If the casing valve is closed, then all gas is produced through the pump and any type of gas separation will not be effective. When gassy fluids are encountered, if possible set the pump below the perforations. Using a rat hole is the best type of downhole gas separation available. If a dead space below the bottom perforations is not available, then the pump should be set as deep in the casing as possible and an improved offset gas separator should be ran. If you have a rat hole, be sure to clean out any debris in the the well before placing the pump below the perforations. Downhole gas separators do not separate gas in solution, only separates free gas at the pump intake.
Do not run tail pipe! All tail pipe does is to guarantee that any gas in solution at the tubing intake pressure is trapped and gas evolving from solution will cause gas interference at the lower pressure at the shallower pump depth.
Production Methods used to produce flumping wells are: 1) set the pump intake as deep as possible. 2) set the pump in the rat hole, if one exist, 3) if no rat hole, run an improved gas separator 4) Use a specialty pump such as a VSP pump to handle gas. 5) Increase pump compression ratio with a longer stroke length, 6) space out the pump to minimize dead space at bottom of stroke to increase compression ratio to the maximum, 7) Use a backpressure valve on the tubing 8) sometimes a backpressure valve is required on casing to prevent the well from stopping to pump liquids to the surface. Dynamometer and fluid level data from various wells will be presented to identify and troubleshoot the many flumping symptoms listed above.