Plunger lift has been around since the 1950s as a lower cost artificial lift solution for gas wells and high gas oil ratio (GOR) environments (1). This lift type was once applauded as a simple engineering fix for liquid loading and an alternative to intermitting operations, foamers, and well venting, but as we’ve seen in the last few years, operators can experience difficulties in optimizing, especially as operating conditions in the oilfield evolve, such as in the development of horizontal and deviated wells (1).

Since plunger lift's initial inception, the industry has increased its knowledge on problematic operating environments for plungers as well as on the emissions impact of venting and well blowdown activities that still occur in plunger lift systems. For both reasons, plunger optimization and control are at the forefront of many production engineers' and HSE professionals’ minds. In order to address some of these concerns, below we will summarize plunger lift challenges as well as potential innovations that can help.

Difficulties with Horizontal Well Production

Horizontal drilling has allowed operators to maximize their access to reservoirs, increasing production with a lower surface footprint, but difficulties arise once the reservoir begins to deplete and lose energy. The engineering behind how the system works relies heavily on the formation characteristics and wellbore conditions, oftentimes making each well have distinct behaviors (2).

Some of the problematic operating environments relating to these operational irregularities include:

• Extremely low-pressure wells (<100 psia)
• High liquid production (>100 B/D)
• Deep wells (16,000+ ft)
• Slimhole wells (2 7/8 to 3 ½ in casing)
• Packers
• Paraffin
• Scale
• Sand
• Hydrate production environments

The unfortunate reality of horizontally lifted wells using plunger lift is that the rules of thumbs created in vertical environments do not always transfer into horizontal or deviated wells. A deep understanding of the wellbore and reservoir is necessary to develop pattern recognition specific to the well you are optimizing. As much as operators would like to conduct simple troubleshooting, such as increasing or decreasing timers, the context of the operations needs to be taken into consideration so that a holistic solution can be implemented, such as changing the design and plunger type.

Different Plunger Types According to Flowco’s website, there are four main plunger types that are typically used under different conditions (4).

The Main Types of Plunger Lift Systems include:

• Bypass and/or Continuous Flow Plungers – used in high gas and liquid rate wells that require very little to no shut-in time (EX: 1200 mcf/day & 400 bbls/day)
• Fast Fall Plungers – used in high gas and liquid rate wells that require some shut-in time (EX: 350 mcf/day & 40 bbls/day)
• Conventional Plungers – for moderate to low-rate wells that require shut-in to allow for pressure build-up to unload liquids (EX: 100 mcf/day & 10 bbls/day)
• Multistage Plunger Lift – for lower GLR wells that do not support traditional plunger lift applications. The gas and liquids are lifted in stages throughout the tubing string which allows the system to be operated at lower GLR’s.

Nuances in understanding when to switch from one system to the next are not always apparent but are quite crucial to the success of the plunger lift system. One of the more pressing “symptoms” in a faulty plunger lift system, however, may very well be the emissions being emitted from that particular well, which brings us to the next point.

Plungers – Not Quite a Net Zero Lift Type

Removing accumulation of fluids can be done using remedial treatments such as swabbing, soaping or venting the well (aka well blowdowns), but installing a plunger lift system can also help in becoming more proactive at addressing liquid loading issues (4). Unfortunately, as time passes, a plunger lift system may lose its effectiveness in reducing emissions, especially as a byproduct of inefficient troubleshooting efforts such as long shut-in period or swabbing.

“Unloadings of wells with plunger lifts occur, on average, more than 200 times per year. Although the events are more frequent than for wells without plunger lifts (<10 events/yr), the emissions per event are lower for wells with plunger lifts” (5).

In some regions, such as New Mexico and Colorado, operators will have to virtually eliminate liquid unloading operations and pose strict exceptions and documentation requirements (6,7). However, this is just the beginning and over time, more regions will face changing regulations.

Summary and Where Innovation Fits

With respect to plunger lift systems, accommodating for horizontal wells, a greater focus on emissions and keeping operational costs low are three things that are currently being solved in industry right now. Better equipment, field visibility, better data capture, and software optimization all play a part in meeting those three criteria and improving plunger lift systems.

1. Better Equipment: These are hardware-based improvements on plunger lift systems, a big one being controllers. These controllers have given operators the ability to automate plungers based on time, pressure, or more advanced algorithms. An example innovator is Reveille Energy Innovation, who’se Gas Lift Optimization Controller (GLOC) has been utilizing a Reynold’s number calculation to optimize GAPL wells in the Barnett.

Better subcomponents and design also live in this category of better equipment. An example of such would be Flowco Production Solutions who, with their deep expertise on gas lift and plunger lift solutions, can make design recommendations and supply the equipment to see this through.

2. Field Visibility: Gaining visibility into your field’s operations through SCADA and/or SCADA alternatives is a great step into ensuring plungers are working as designed, and to quickly capture downtime. Add in a controller and you can soon make changes from the office.

Three innovators in this space include Iron-IQ, WellAware and Avenirre. Iron-IQ offers a modern, cloud-native SCADA solution to oil & gas operators that allows them to simply ingest data from the field, customize the user experience based on the role, and control operations from any chrome browser in the world. WellAware provides a full stack, edge-driven, IoT platform that can leverage their “WellAware Connect” device instead of an RTU to provide visibility as well as remote control. Avenirre is taking mature asset management to the next level by including an emissions dashboard as part of their software offering and greatly focusing on mature assets such as those operating with plunger lift.

3. Better Data Capture: Some of the innovators already mentioned can help provide better data capture through the edge hardware they’ve built, but what this category is specifically referring to is novel data capture, such as what can be captured by acoustic fluid level instruments like Echometer. There are other innovators in this acoustic downhole sensor space, such as Acoustic Data and Acoustic Wells, but Echometer has specifically published on their work in the Plunger Lift space (8).

4. Software Optimization: We’ve seen what a simple timer-based and pressure-based controller can do with regards to better running plungers, but we’ve also seen the limiting factors of delaying repairs & replacements, narrow optimization algorithms, and the importance of embedding low/zero emissions into your automation requirements. This category of software optimization refers to the software technology out there taking a data-driven approach to proactive maintenance, optimizing setpoints providing recommendations, and embedding ML / AI into their platforms.

Ambyint, for example, has brought their physics-driven models from rod pumps and is transferring similar methodology to the plunger lift space. TASQ is an innovator that has built a platform to easily capture knowledge from your operations, combined with operational data, both historical and in real time, to provide automation, recommendations and alerts in a fashion that helps field personnel conduct their job more efficiently. There’s been a couple operators, such as YPF and Ovintiv, working on developing their own optimization models in this space (9,10).

It is exciting to see the industry push the boundary on low-cost operations and tune into their excellence to improve plunger lift systems, from both an operational efficiency perspective and emissions reduction perspective. We are super excited to be covering this topic more deeply at the May 4th event and welcome any learnings or comments on this plunger lift space in the comments.

Sources

1. Defining Series: Plunger Lift

2. Plunger Lifts, Farmington 2010

3. Flowco: Plunger Lift Solutions

4. EPA on Plunger Lift

5. UT Study Unloadings

6. EMNRD 19.15.27 New Rule

7. Colorado Code Regs for Venting or Flaring

8. Echometer: "Plunger-Lift Monitoring.."

9. YPF: "Prescriptive Model for Automatic Online Plunger Lift…"

10. Encana: "Plunger Lift Optimization…"