Beam Pumping Units
When energy is required to move the product to surface, the energy comes in the form of artificial lift.
Application of Mechanical Pumping.
The mechanical pumping unit remains as one of the best ways to produce artificial lift wells. It is also satisfactory for marginally producing wells, and the majority of all
artificial lift wells use mechanical lift. This system of pumping works well for
low production because the surface equipment requires very little daily attention.
Each installation is an independent system, is economical to maintain, is easily automated, and is ideal for both intermittent as well as continuous production. Other lift methods may be more appropriate for a specific situation and for higher production rates, but for many applications mechanical lift is ideal, including in shallow wells.
A standard conventional pumping system consists of 3 major components:
The beam pump
The bottom hole pump.
The sucker rod and tubing string, which connects the beam pump to the bottom hole pump.
A conventional beam-style pumping unit.
The crank of the pumping unit is driven in a circular motion by the rotation of the sheaves or pulleys, belts, and gearbox.
The gearbox is driven by the prime mover, generally a gas-powered engine or an electric motor.
The pitman arms are connected to the walking beam, and the rotary action is converted into reciprocating power to the walking beam and the horse head. A set of counterweights offsets the weight of the string of rods and part of the weight of the fluid in the tubing.
The string of rods usually extends through the tubing to the bottom of the well, and a pump is installed below the fluid level at the bottom of the hole. By using a ball-and-seat style of standing and traveling valves, the liquid—usually a combination of oil and water—is pumped from the bottom of the oil well to the surface, through the flow line, and into the tank.
As the pumping unit starts, the head of the pumping unit moves upward, lifting the
sucker rod string and the plunger in the pump. The traveling ball or valve closes so
that oil cannot pass through the plunger as it moves upward. This action lifts the fluid in the tubing string toward the surface, while also creating reduced pressure below the plunger. The standing valve in the bottom of the pump opens due to the reduced pressure, allowing additional fluid to enter the bottom of the pump.
As the rod string starts moving downward, the increased pressure from above close the standing valve in the bottom of the pump. This prevents the oil that has entered the pump barrel from flowing back into the formation and allows pressure to build up between the valves, which open the traveling valve as the pressure between the valves grows greater than the weight of the fluid in the tubing. The plunger passes down through the fluid that entered the pump barrel during the upstroke, trapping it on top of the plunger once the traveling valve closes as the next upstroke begins, and the cycle will be repeated. The time required for each cycle is determined by how the pumping unit is configured, including the speed of the prime mover, the ratio of gears in the gearbox, and the sizes of the sheaves or pulleys. This cycle time is referred to as strokes per minute (SPM) and is partially determined by the revolutions per minute (RPM) of the prime mover.