In response to the boom of horizontal plays in the U.S., operators require artificial lift systems capable of providing reliable production in these wells often characterized by harsh, abrasive, and turbulent conditions. Due to the versatility and production capabilities of Electric Submersible Pumps, these systems have become widely adopted in unconventional applications. While ESPs provide several advantages in terms of flow capacity, lift efficiency, and setting depth, gas production can result in unstable pump operation and increase operating costs due to premature equipment failure.
Therefore, solutions that extend system run life and ensure efficient, uninterrupted operations are an essential part of a successful ESP strategy in unconventional applications. Luckily, achieving reliable ESP production in these high gas environments can be as simple as selecting the right technology for the job. To simplify the design process, Valiant categorizes strategies for gas management into four phases:
- Avoid
- Separate
- Process
- Control
Don’t let gas get in the way of your operations.
In this guide, you’ll learn the ins and outs of the problems that cause ESP underload alarms and motor shut-downs, and you’ll come away with a working knowledge of the specific tactics you can use to avoid, process, separate, or control gas in the wellbore while maintaining efficient, uninterrupted production.
Avoid
This phase involves using different mechanisms to prevent gas in the annulus from entering the production string. Shrouds are typically the most recognizable mechanism for Gas Avoidance. By leveraging the natural separation of gas and the production fluid, shrouds allow gas to follow the path of least resistance towards the top of the annulus while drawing fluid towards the pump intake.
Separate
Just as it sounds, Gas Separation can be employed with a device known as a gas separator, which works by isolating production fluid and directing gas bubbles to flow back out into the annulus. As part of the ESP string, the gas separator can leverage centrifugal force to separate gas from the production fluid before entering the primary production pump.
Process
Also known as gas handling, this phase is often misrepresented as referring to a single piece of equipment. In fact, gas handling and gas processing encompass a collection of distinct solutions, all designed to ease the flow of gas through the pump and reduce gas locking. This can include helico-axial stages, which are commonly referred to as “gas handlers”, as well as tapered pumps and other designs that serve to homogenize the gas-fluid mixture. So why would you choose to keep gas in the pump? When conditioned properly, gas provides natural buoyancy to the production fluid, thus allowing the operator to improve lifting efficiency and recover fluids at the surface faster. In many cases, a gas separator is placed below a set of helico-axial stages to remove larger gas bubbles, while the stages help trap the smaller bubbles in the fluid before entering the production pump.
Control
Finally, operators can manipulate ESP operation to prevent motor temperature failures due to gas locking. This can be achieved through automation with a variable speed drive or can be done manually with close monitoring and shut-off capabilities. However, when coupled with proprietary gas-lock mitigation software such as Valiant’s Pulse programming, operators can further reduce gas interference by slowing down the motor, thus allowing gas slugs to move through the system without causing a shutdown.
All of these options can be effective in the right conditions, but ensuring success in the field ultimately depends on selecting the technology best suited for your application. Taking into account wellbore diameter, depth, placement of perforations, and the severity of your gas conditions will help you narrow the selection and extend the run life of your ESP for profitable production.