Sucker Rod Pumping Systems: Components and Operational Considerations

Mechanical Pumping System Components

Polished Rod

The polished rod bears the weight of the sucker rod string, the subsurface pump, and the fluid column within the tubing. Made of durable material, polished rods typically come in diameters of 1 1/4 and 1 1/2 inches, with lengths of 16 and 22 feet.

Subsurface Pumping System Components

Sucker Rod String

The sucker rod string transmits the reciprocating motion from the surface pumping unit to the subsurface pump. Available materials include steel, fiberglass, and continuous rods, each designed for different well depths, loads, and fluid conditions.

Subsurface Pump

The subsurface pump is a critical element in designing a mechanical pumping installation for a well. Its type, size, and placement significantly influence the selection of other system components.

Main Components of the Subsurface Pump

The primary components of a subsurface pump include:

• The cylinder or barrel
• The plunger or piston
• The traveling valve
• The standing valve

Subsurface Pump Classification

Subsurface pumps are generally classified into three main groups: pipe type, insert type, and casing pumps.

Pipe Type Pumps

Pipe type pumps are installed directly onto the tubing string, making the pump an integral part of the tubing. Their primary application is in high-productivity wells with depths less than 4,500 feet, where production conditions are not severe (e.g., low gas production and minimal abrasive or corrosive fluids).

Insert Type Pumps

Insert type pumps (also known as rod pumps) are installed in wells using the sucker rod string without requiring removal of the tubing. They are typically applied in wells with moderate to low productivity and depths up to approximately 7,000 feet.

Casing Pumps

Casing pumps are characterized by their ability to be used with the well's casing pipe. This allows for larger diameter pumps, which can accommodate higher production volumes.

Gas Anchor

A gas anchor is a slotted or perforated pipe positioned at the pump intake. Its purpose is to improve gas separation from the fluid before it enters the pump, thereby preventing a reduction in the pump's volumetric efficiency. Several types of gas anchors exist, including natural, perforated nipple, cup, and duplicator designs.

Advantages and Limitations of Mechanical Pumping

Advantages

• The design is relatively straightforward.
• Pumping units can be easily installed in other wells at minimal cost.
• The system is efficient, simple, and easy for field staff to operate.
• Applicable to both single and multiple well completions.
• Capable of pumping a well at very low pressures, depending on depth and production rate.
• The system typically includes a gas anchor and allows for fluid level surveys.
• Highly flexible, allowing the pumping rate to be matched with well capacity as production declines.
• Effective for lifting viscous fluids and operating in high-temperature environments.
• Can utilize gas or electricity as an energy source.
• Available in various diameters to suit different well conditions.

Limitations

• Deviated wells often present significant friction problems.
• Production with high solids content can lead to operational difficulties.
• Limited by well depth.
• The equipment is heavy and generally not suitable for offshore applications.
• Requires relatively high maintenance costs.