Sucker rod pumps - Sucker rod pumps remain common for shallow to medium-depth oil wells.

A sucker rod pump, also known as a beam pump or "pumpjack," is a widely used form of artificial lift in the oil and gas industry. It is a system designed to bring oil and other well fluids from the reservoir to the surface when the natural pressure of the well is no longer sufficient to do so. The system is made up of both above-ground and downhole components.

How It Works
The working principle of a sucker rod pump is a simple reciprocating motion that operates a piston pump located at the bottom of the well.

Surface Equipment: The most visible part of the system is the surface pumping unit, commonly known as a pumpjack. This unit, powered by an electric motor or a gas engine, uses a gearbox and a crank to convert the motor's rotary motion into a reciprocating (up and down) motion. A large, counterweighted walking beam is at the heart of this process.

The Sucker Rod String: A series of steel rods, known as the sucker rod string, connects the surface unit to the downhole pump. This string acts as the mechanical link that transmits the up-and-down motion from the pumpjack to the pump deep inside the well.

Downhole Pump: Located at the bottom of the well, the downhole pump consists of a stationary barrel and a moving plunger. The plunger is connected to the sucker rod string. The pump also has two ball valves: a standing valve at the bottom of the barrel and a traveling valve on the plunger.

The Pumping Cycle: The up-and-down motion of the sucker rod string drives the pumping cycle:

Upstroke: As the plunger moves upward, the pressure below it decreases. The standing valve opens, allowing fluid from the reservoir to flow into the pump barrel. At the same time, the traveling valve is held closed by the weight of the fluid column above it, lifting that fluid up the tubing.

Downstroke: As the plunger moves downward, the pressure in the pump barrel increases. This pressure closes the standing valve and opens the traveling valve. The fluid from below the plunger is then pushed into the area above the plunger, ready to be lifted on the next upstroke.

This continuous cycle of pushing and pulling effectively lifts the well fluids to the surface, where they are collected.

Advantages and Applications
Sucker rod pumps are a well-established and reliable technology, making them the most widely used artificial lift method globally, especially for low-to-medium production rate wells.

Simplicity and Reliability: The system is relatively simple to operate, and its components are rugged and widely available. This makes for easy maintenance and a long service life.

Cost-Effectiveness: The initial capital cost and operational expenses are generally low compared to other artificial lift methods.

Versatility: They are effective in a variety of well conditions and can handle fluids with some sand, gas, and other solid impurities.

High Salvage Value: The surface equipment has a long lifespan and can be moved and reused on other wells, providing a high salvage value.

Sucker rod pumps are primarily used in onshore oil fields to produce from low-pressure wells. They are particularly well-suited for shallow to moderately deep wells. While their use is limited in very deep wells or those with extremely high gas content, continuous advancements in technology have expanded their capabilities to handle more challenging conditions.