06 May 2011

Electric Submersible Pump - ESP Artificial Lift Technology

The ESP unit consists of a motor, pump, protector or seal, intake or gas separator, cable, switchboard or variable speed drive, and several accessories. The ESP unit comes in a wide range of sizes and can vary from a small unit costing 15 thousand dollars to large high metallurgy units that could cost over $500k USD. 

The ESP market ranges from 120 to 35,000 barrels of fluid a day, is designed to operate in any size casing from 4.5” and larger. ESP’s horsepower range from 5 HP to 1,500 HP units. ESPs have been deployed to depths of 12,500 ft. 

There have been a lot of technology improvements over the last 25 years that allow the ESP to operate in many difficult applications.
These improvements comprise Variable Speed Drives, Gas Separation, Pressure Sensors, Automation, High Temperature technology, metallurgy in the pump that helps with sand and wear, along with high load bearings.

Variable Speed Drive; has allowed the ESP to slowed down and speed up to help keep the pump to within the recommended range.

Gas Separation;  the improvements in the gas separation has allowed more ESP’s to operate in high gas/oil ratio wells and even in dewatering of many gas wells.  

Pressure Sensors; have improved the performance so more and more customers rely on this technology. In the past sensors were not known as reliable so most customers did not install them. In many Countries of the world the pressure sensors is now considered essential to being able to monitor and improve the run life of the ESP.

Automation; with the introduction of automation the key components of the ESP can be monitored, allowing the customer to make changes to improve run life or prevent failures. With down hole pressure monitoring, vibration and monitoring motor heat, the ESP run life can be improved.

High Temperature technology; New motor technology has allowed the large manufacturers to operate in wells up to 450 F.

Pump Metallurgy; improvements in technology providing hardiness in key areas, along with bearings to prevent vibration, sand wear have improved pump life.

High Load/high temperature Bearings; new technology have improved thrust load in the protector, which has increased run life in the difficult wells for the ESP equipment.

Sucker Rod Pump - PumpJack

The Rod Pump is a traditional form of artificial lift. It is the most familiar  as a symbol of oil production, having been in use throughout the world since the pioneer oil industry days.
Rod Pumps / Pump Jacks still capture a significant percentage of the artifical lift technology utilized by oil producers.

How a Rod Pump works:

  1. A motor supplies power to a gear box. The gearbox reduces the angular velocity and increases the torque relative to this input.
  2. As shown above left, the crank turns counterclockwise and lifts the counterweight. Since the crank is connected to the walking beam via the pitman arm, the beam pivots and submerges the plunger. The illustration shows the horsehead at its lowest position. This marks the end of the down stroke. Note that the crank and the pitman arm are in-line at this position.
  3. The upstroke raises the horsehead and the plunger, along with the fluid being pumped. The upstroke begins at the point shown. At the end of the upstroke, all joints are in-line. This geometric constraint determines the length of the pitman arn.
  4. The embodiments (top right) show the plunger and ball valves in more detail. These valves are opened by fluid flow alone. On the upstroke, the riding valve is closed and the standing valve is open. Fluid above and within the plunger is lifted out of the casing while more fluid is pumped into the well. On the down stroke, the riding valve is opened and the standing valve is closed. Fluid flows into the plunger and no fluid is allowed to leave the well. 

05 May 2011

Progressive Cavity Pump - PCP

The PCP is a form of artificial lift typically utilized in pumping viscous fluids ( low API) and also tough abrasive media. Field installs and experience base are most common in Venezuela, and North America.

A progressive cavity pump is a type of positive displacement pump and is also known as a progressing cavity pump, or an eccentric screw pump. It literally pushes / squeezes / pushes fluid from one cavity to the next through the pump, from  a series of small, fixed shape cavities, as its rotor turns. This leads to the flowrate being proportional to the rotation rate (bidirectionally) and to low levels of shear force being applied to the fluid.

Weak link in application design for a particular artificial lift problem set tends to be the elastomers and related temperature constraints, together with effects from forms of abrasives such as sand, etc.

The PCP pump is used in generally lower flow oilfield applications.

Gas Lift - Processes and Tools

Gas Lift is a principal method of secondary oil recovery utilized by operators in basins throughout the world.

Gas lift does not require the tooling capital costs compared with other forms of artificial lift such as rod pumps and the electric submersible pump (esp). The gas lift process involves injecting gas through the tubing / casing annulus. The injected gas aerates the fluid to reduce its density. In this way, the formation pressure is able to lift the oil and water column and forces the fluid out of the wellbore. Gas may be injected continuously or intermittently, depending on the producing characteristics of the well and the arrangement of the gas lift equipment.

Gas lift is a form of artificial lift where gas bubbles lift the oil from from the formation strata through to the well.
The amount of gas to be injected to maximize oil production varies based on well conditions and subsurface geometries. Too much or too little injected gas will result in less than maximum production. Generally, the optimal amount of injected gas is determined by well tests, where the rate of injection is varied and liquid production (oil and many times water) is measured.
Although the gas is recovered from the oil at a later separation stage, the process requires energy to drive a compressor in order to raise the pressure of the gas to a level where it can be re-injected.

Types of tools - the gas lift mandrel is a device installed in the tubing string of a gas lift well onto which or into which a gas lift valve is fitted. There are two common types of mandrels. In a conventional gas-lift mandrel, a gas lift valve is installed as the tubing is placed in the well. Thus, to replace or repair the valve, the tubing string must be pulled. On the other hand, in the side pocket mandrel the valve is installed and removed by wireline while the mandrel is still in the well, eliminating the need to pull the tubing to repair or replace the valve.

A gas lift valve is an apparatus that is  installed on (or in) a gas-lift mandrel, which is put on the production tubing of a gas lift well. Tubing and casing pressures cause the valve to open and close, thus allowing gas to be injected into the fluid in the tubing to cause the fluid to rise to the surface.

Gas lift mandrels are "tubing retrievable" as they are deployed and retrieved attached to the production tubing.

Oil and Gas Production - Artificial Lift

Focus : Artificial Lift

Objective: Exchange opinions about processes, methods, tools, reliability, economics and performance enhancement. 

Target readership - oil & gas professionals worldwide.