Artificial Lift Systems Overview

Artificial Lift Overview

• Artificial lift is used in mature, depleted fields
• Gas lift and pump-assisted lift are two major categories
• Plunger lift is a hybrid method, combining elements

Introduction to Artificial Lift

• Inflow Performance Relationship (IPR) defines a well's potential
• q = PI (PR - Pwf)
• q = production rate, B/D
• PI = productivity index, B/D/psi
• pR = average reservoir pressure, psi
• pwf = flowing bottomhole pressure, psi

Gas Lift

• In gas lift, high-pressure gas is injected into the producing fluid column to reduce hydrostatic pressure
• Continuous gas lift injects gas constantly
• Intermittent gas lift injects gas in "slugs" to displace fluid

Reciprocating Rod Pump Systems

• A reciprocating rod pump system lifts fluid by moving a plunger up and down
• The system includes components like surface equipment, subsurface equipment, and subsurface pump selection

Progressive Cavity Pump Systems

• A progressive cavity pump (PCP) uses a spiral rotor turning inside a stator to create a pumping action
• PCPs are useful for dewatering, production and injection

Hydraulic Pump Systems

• Hydraulic pump systems use fluid, typically oil or water, to pump fluid to the surface
• Downhole hydraulic pumps have two basic types; reciprocating pumps and jet pumps

Electrical Submersible Pump Systems

• ESPs are centrifugal pumps that are driven by submerged electric motors
• They are used for high-volume applications in deep wells

Plunger Lift Systems

• The plunger is automatically dropped to lift the fluid

Selecting an Artificial Lift Method

• Reservoir characteristics like IPR (flow rate), liquid production rate, water cut, gas-liquid ratio, viscosity, and formation volume factor influence selection
• Field and operating considerations including flow rates, well depth, completion type, and tubing/casing sizes impact lift method choice

Gas Lift Surface Facilities

• The gas lift process involves surface equipment like compressors, scrubbers, and separators

Downhole Installations

• Open, semi-closed, closed, chamber, and slim-hole are different installation types

Gas Lift Valves

• Operating valves are the deepest and are responsible for gas injection rate
• Unloading valves reduce fluid level before production restarts

ESP Power Components

• Transformers step up or down voltages for the electric motor.
• Switchboards are used to control and protect the electric motor.

ESP System Design

• ESP performance curves are used to determine pump capacity, flow rate, horsepower, and efficiency

ESP System Operation

• Pulling the tubing is a necessary procedure in ESP maintenance

Optimizing Pump Performance

• Changes to the motor and pump, including changing the pump or increasing wellhead pressure
• Reducing the pump speed or motor speed, cycling the pump, reducing the motor's speed
• Installing silicone-controlled rectifiers-soft start and soft stop
• Implementing variable frequency drive (VFD)

Rod Pumping Systems

• Reciprocating rod pump systems use a plunger to lift fluid vertically to the surface from their bottom
• Prime mover is the power source, it is either an internal combustion engine or electric motor
• Gear reducer is used to slow down the rotational speed of the prime mover and matches it to the required speed of the pumping unit, this high reduction enables higher pumping forces
• Pumping unit handles the rotational movement

Surface Equipment

• Prime mover and gear reducer are the main surface components
• Internal combustion engines or electric motors form the prime mover section
• Internal combustion engines come in slow speed and high speed types, high speed engines are generally more expensive but more effective
• Electric motors are more commonly utilized since they are more readily available and relatively low cost

Additional Subsurface Equipment

• Tubing anchors, rod rotators, and sinker bars can help prevent damage
• Tubing anchors prevent tubing from moving during the pumping cycle
• Rod rotators rotate the sucker rods in the tubing
• Sinker bars provide concentrated additional weight to stabilize and maintain straight sucker rods

Subsurface Pump Selection

• Factors that can affect selection; pump displacement, stroke length, speed and plunger diameter
• Determine if well conditions like fluid, corrosivity, rate, well depth, casing and tubing sizes are acceptable for a given pump type

Plunger Diameter

• Table 1 offers suitable plunger diameters based on production rate and well depth

Stroke Length and Pump Speed

• The optimal stroke length-pump speed combination is critical for efficient operation, avoiding excessive rod stress
• There is a maximum pump speed depending on the type of pump; it is critical to keep this speed below the maximum
• Manufacturers offer charts and considerations to assist in proper selection, including taking into account well depth, viscosity, and other considerations