The Role of Oilfield Chemicals in Gas Lift Systems

In the exploration and production of hydrocarbons, gas lift systems play a vital role in enhancing the recovery of oil and gas from wells. Gas lift is a widely used artificial lift method that injects compressed gas into the wellbore to reduce the hydrostatic pressure of the fluid column, thereby allowing the reservoir fluids to flow more freely to the surface. However, the effectiveness and efficiency of a gas lift system can be significantly influenced by various factors, one of the most critical being the use of specialized oilfield chemicals. This article explores the essential roles that oilfield chemicals play in optimizing gas lift operations, ensuring smooth production, and prolonging the life of the well.

1. Corrosion Inhibitors

Corrosion is a major concern in gas lift systems, primarily due to the presence of water, carbon dioxide (CO₂), and hydrogen sulfide (H₂S), which can create highly corrosive environments within the wellbore and surface facilities. Corrosion inhibitors are vital oilfield chemicals that protect metal surfaces from corrosive agents. These chemicals form a protective film over the metal surfaces, reducing the rate of corrosion and preventing damage to tubing, valves, and other critical components. By mitigating corrosion, these chemicals extend the lifespan of the equipment and reduce maintenance costs.

2. Scale Inhibitors

During gas lift operations, changes in pressure and temperature conditions can lead to the precipitation of scale-forming minerals such as calcium carbonate (CaCO₃) and barium sulfate (BaSO₄). Scale deposits can clog the gas lift valves, restrict fluid flow, and reduce the efficiency of the system. Scale inhibitors are oilfield chemicals designed to prevent the formation and deposition of these mineral scales. By dispersing and sequestering scale-forming ions, these chemicals help maintain optimal flow rates and ensure the uninterrupted operation of the gas lift system.

3. Hydrate Inhibitors

Hydrates are crystalline compounds formed when water molecules trap gas molecules, such as methane, under high-pressure and low-temperature conditions. In gas lift systems, hydrate formation can occur in the tubing or flowlines, potentially leading to blockages and reduced production rates. Hydrate inhibitors, including thermodynamic inhibitors like methanol and monoethylene glycol (MEG) or low-dosage hydrate inhibitors (LDHIs), are used to prevent hydrate formation by altering the conditions required for hydrate crystals to form. These chemicals play a crucial role in maintaining flow assurance and minimizing the risk of unplanned shutdowns.

4. Paraffin Inhibitors and Dispersants

Paraffins, or waxes, are naturally occurring hydrocarbons that can precipitate out of crude oil at lower temperatures, forming deposits on the inner walls of the tubing and flowlines. These deposits can significantly impede fluid flow and reduce the efficiency of gas lift operations. Paraffin inhibitors are oilfield chemicals that prevent the formation of wax crystals, while paraffin dispersants help break down and disperse existing wax deposits. By controlling wax deposition, these chemicals help maintain the integrity of the gas lift system and ensure stable production rates.

5. Emulsion Breakers and Demulsifiers

Gas lift systems often deal with the challenge of water-in-oil emulsions that can form during production. These emulsions increase the viscosity of the produced fluids, leading to higher pressure losses and reduced flow efficiency. Emulsion breakers or demulsifiers are oilfield chemicals that destabilize these emulsions, allowing the separation of water from the oil. The effective use of these chemicals ensures a more efficient separation process, reduces the risk of flow assurance problems, and enhances the overall performance of the gas lift system.

6. Foamers and Defoamers

Foam can be problematic in gas lift operations, particularly in wells producing gas along with liquids. Excessive foaming can hinder the accurate measurement of fluid levels and flow rates, reducing the efficiency of gas injection. Foamers are used in situations where foam can help lift fluids more effectively, while defoamers are used to break down unwanted foam. The appropriate application of these chemicals can stabilize the gas lift process and maintain optimal production levels.

7. Biocides

Microbial activity in gas lift systems can lead to a variety of issues, such as corrosion, biofouling, and the formation of hydrogen sulfide by sulfate-reducing bacteria (SRB). Biocides are oilfield chemicals that control the growth of harmful bacteria in the wellbore and surface facilities. By preventing microbial-induced corrosion (MIC) and other biological problems, biocides help maintain the integrity and safety of the gas lift system.

Oilfield chemicals play a critical role in the effective operation of gas lift systems. From corrosion and scale inhibitors to emulsion breakers and biocides, these chemicals help overcome a wide range of challenges associated with production, ensuring optimal flow rates, protecting equipment, and minimizing maintenance requirements. As the demand for hydrocarbons continues, the importance of these chemicals in maintaining the efficiency and longevity of gas lift systems cannot be overstated. Their application is not only vital for maximizing production but also for maintaining safe and sustainable oil and gas operations.

Improving the bottom-line performance of a well on gas lift is largely a balancing act between maintaining the most favorable injection rate and achieving the desired reservoir drawdown to optimize the production rate, and avoiding problems that disrupt either injection or production. Getting that balance exactly right requires cross-functional solutions, based on enhancing the interactions between the gas lift equipment, chemical program, injection controls, and completion parameters in a dynamic downhole environment that is continually changing from the moment first injection commences.  

Even the best designed gas lift system can be impacted negatively by corrosion, paraffin, scale, and organic solids. Experience shows that when a gas lift system fails, odds are it’s because a gas lift valve has failed, due to corrosion. Corrosive fluids and gases can not only damage valves, but degrade tubular integrity, allowing the influx of injected gas at points other than the valves. Additional common root causes of system failures are solids and debris, paraffin, and scale inside valves and tubulars that restrict or block flow.  

The majority of gas lift wells require chemical treatment, typically consisting of corrosion inhibitor, scale inhibitor, paraffin solvent, biocide, and flow improver applied on a continuous basis. However, because the physical downhole conditions encountered in gas lift wells are distinct from other forms of lift, it is critical to use chemical products and delivery systems suited specifically for the application.

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