Why Offshore Gas Recovery is Further Difficult

With the worldwide commitment to decarbonization, the recovery of gas offshore from oil and gas platforms has been in focus. While the recovery of associated gas (FGR) is relatively mature on land, the recovery of gas offshore from platforms is more complex from a technical and managerial perspective. This article reviews the barriers and possible solutions to offshore gas recovery in engineering, equipment, and safety.

Engineering Challenges of the Offshore Environment

Engineering challenges on land are always simpler compared to those on water and at sea. Oil and gas offshore platforms are located the furthest from the shore and in the harshest of environments. All the following difficulties are encountered in such situations:

Limited Space and Structural Deficiencies

Offshore platforms such as FPSOs, marginal well platforms, and older offshore facilities have marketplaces of gas recovery, compression, and liquefaction equipment. Space is limited in every direction which in turn obstructs the un encumbered free of internal gas compression, liquefaction, and control system condensation. Unobstructed gas recovery is crucial to the operational success of any offshore gas facility, which is why onshore space scarcity is not problematic. All engineering designs document production and focus on the space pathways created by the gas CO2 recovery control systems of condensation. Obstructed space directly increases the operational recovery efficiency of the gas.

Complex Fluid Characteristics and Fluctuating Operating Conditions

When dealing with gas offshore, you must know that the gas often comes with liquids and impurities, namely water, oil, H₂S, and CO₂. This means that the gas would either be a two-phase or three-phase combination. Given this, the compressor and condensation system will be dealing with constantly shifting conditions. Additionally, it is important to highlight that the gas captured from the wells will not be the same at all points in time, and this will be especially true for marginal wells and older gas fields. There’s a need for the recovery equipment to act swiftly, or else it will face problems with overload and drops in efficiency. When it comes to production stages, the platforms will be under conditions that may adjust to changes in the wellhead pressure, the composition of gas within, and the environmental temperature, for example, the temperature of seawater. Given all of this, recovery systems need to be able to control systems that work almost autonomously, and systems that have to adjust to shifting but in a smooth manner.

Remote Operation and Maintenance Challenges

The offshore platform is often located many miles away from supply bases and ports and since there is a lot of equipment that can malfunction and lead to high maintenance costs and extended downtimes. Weather is also a major factor in determining how quickly tasks can be completed offshore construction also has extended periods of inclement weather. Installation becomes increasingly diffcult as CAPEX becomes more hindered in construction. When there are leaks in pipelines, high pressure compressors, or liuifaction systems there is a great need for immediate action. However, there is very little personnel at the platform. As such, equipment to not break are very needed and howerver equipment for remote supervision and operation is.

Harsh Environmental Conditions

The presence of high salinity and humidity facilitates the rapid corrosion of metallic structures and piping systems. Pressure vessels, heat exchangers, and condensers must be constructed of corrosion-resistant materials and protective coatings. Continuous vibration from waves and wind exacerbates the mechanical stress on pipes, valves, pumps, and compressors. Seawater and ambient temperature changes affect the heat exchange, condenser, and liquefaction efficiencies and require redundancy or other design accommodation.

Engineering Solutions

In response to such obstacles, offshore gas recovery often employs modular skid-mounted designs and prefabs FGR and mini-LNG systems, as they simplify transport, lifting, and fast deployment. Having pre-piped and pre-wired systems mitigates the need for on-site welding and increases safety, as well as efficiency, of the installation. Gas recovery is ensured and maintained within safety ranges for multi-phased recovery sustained by online monitoring and remote control for adjusting flows, pressures, and maintaining gas security challenges. With the addition of various corrosion-resistant materials, the anti-vibration and improved design of the systems elongates life, diminishes reoccurrence of maintenance, and minimizes potential breakdowns of the systems, allowing for the collection of associated gas to be safely and efficiently operated from complex offshore locations. Therefore, offshore gas recovery is much more complex, expensive, and is supported by better technical and management capabilities compared to the onshore counterparts.

Equipment Perspective: Specialized Requirements for Offshore Gas Recovery

Compared with onshore systems, offshore gas recovery equipment faces higher demands in design and operation.

High Corrosion and Pressure Resistance

Platforms deal with high salinity and humidity every day, ensuring that metal equipment (piping, valves, compressors, heat exchangers) get corroded quicker than average. Octagonal offshore metal structures go through corrosion at an accelerated pace due to the condition. Certain metal structures are unfit for corrosion. Special materials like certain stainless steels, and nickel alloys, and due to the equipment’s corrosion, protective coatings are often necessary.

The recovery of gas that is high in pressure and the compression of that gas, in addition to the liquefaction- are processes that are often performed with specialized FGR compressors and mini-LNG units. These processes deal with high temperatures and high pressure as well. These processes are susceptible to high-severity safety incidents in the case that there is a rupture or release of gas. Because of this, protective equipment structures are often plywood. While this equipment needs to withstand corrosion and pressure at the same time, the standards for structural materials and safety valves, as well as welding, are extremely strict.

Conflicts Between Miniaturization and Efficiency

Gas compression equipment need to be compact (skid-mounted, modular), integrate compression, liquefaction, and control functions, and fit within deck space, but still must achieve around 70% to 95% gas recovery Even small devices can be difficult to designed with the high-efficiency, compact equipment gas flow and pressure fluctuations, and impurities.

The equipment needs to consistently perform within specific gas, geoemetric, and microstructure molds during operation, necessitating having flexible adjustment capabilities, and being designed for a variety of conditions. Balancing efficiency, reliability, and modularity of the equipment is the most difficult part of designing recovery devices.

Monitoring and Control Complexity

Real-time monitoring of processed associated gas is needed to control gas flow, pressure, gas composition (CH₄, CO₂, moisture), and leaks. Systems should monitor, and record, and implement Measurement, Reporting, Verification (MRV) to ensure compliance with EU Methane Regulation, US EPA, OGMP 2.0 and other regulations. Systems should include OGI cameras, FTIR, drone inspections, and the online sensor network to create an effective multi-layer monitoring OGI system. To add complexity in design and operation, include data transmission, storage, and verification by a third party.

Integrated control of monitoring, data management, and remote operation is required to maintain the control and the recovery verification to meet safety and compliance standards.

Modularity and Mobility Requirements

Modular, transportable, and easy to install or uninstall offshore equipment is needed. Modularity brings more mechanical interfaces, piping connections, and control system integrations. In the case of shifting production or rearranging the layout of the platform, equipment will need to be repositioned and require a flexible design. This design must adhere to the standards regarding pressure, sealing, and safety.

Differently from engineering, which concentrates on the layout of the platform, construction, and maintenance, from equipment perspective the foundation is the system performance, reliability, durability, and sophisticated monitoring. This is a fundamental reason that makes offshore associated gas recovery much more technically challenging compared to onshore.

Safety Perspective: Risk Management in Offshore Gas Recovery

Safety is central to platform design and operation, and associated gas recovery carries significant risks:

Flammability and Explosion Hazards

The main component of the gas we handle is methane (CH4), which is highly flammable, with explosive concentrations in air reaching 5%-15%. Any leak can potentially trigger a fire and explosion. This is particularly pronounced on offshore platforms, as wind and humidity can cause sparks in metal equipment. Even the smallest leak can lead to an accident, necessitating comprehensive risk control measures. These incidents require thorough risk management of equipment design, piping layout, and standard operating procedures to completely eliminate risks arising from inadequate control measures.

Risks Related to High-Pressure and Multiphase Flow

FGR compressors, mini-LNG liquefaction units, and gas injection systems typically work in the 30–100 bar range, and sometimes even higher. Pipeline and valve ruptures can cause gas jets. Multiphase flows, i.e., gas and liquids in the same phase, can cause water hammer and thermal stresses in the system, and other hazards in the liquefaction and separation processes. The presence of high pressure and multiphase flow greatly increases the operational risk, with a need to maintain high levels of system stability and control.

Contingency for Severe Weather Conditions

Offshore oil and gas platforms must deal with extreme weather conditions such as typhoons, winds, and high waves, and with salt spray. These factors interfere with the stability of the equipment, and as well with the sealing, and the side operations. There should be extreme contingency plans as solar, gas, flames, fire, and storms (gas, fire, storm) emergencies, and the storm shutting down the platform/seaway emergency. Critical equipment, flares, pumps, and gas sensors should have emergencies gas release systems, and flare. The overriding rationale to the unpredictable weather at sea is a need to design with redundancy, safe shut down folds, and emergency plans including the ability to maintain safe and reliable gas recovery during times of extreme conditions.

Operational and Monitoring Risks

It is mandatory for systems to monitor for flow, pressure, temperature, and leak and to safely maintain their operations. The systems must have strict running guidelines, which include regular LDAR, operating within the manuals eg. and training operators. There must be automated alarm and interlock and emergency shutdown systems. The systems must have been designed and have the engineering to allow for safe management regardless of failure to monitor their operations.

Summary of Safety Strategies

The keeping of safety protocols includes the design of equipment and its high standards (explosion-proof, resistant to pressure, corrosion resistance), the presence of multi-level monitoring systems (online sensors, OGI/FTIR, and remote monitoring), the involvement of emergency designs and redundancies (flare backup and dual redundancy), and the adherence to strict operational protocols (LDAR, training, emergency shutdowns, and alarm linking). The combination of a multi-faceted approach to safety in engineering, equipment, operation, and monitoring means that the recovery of associated gas offshore can be done safely, dependably, and stably, even in extreme oceanic conditions.

Conclusion

To sum up, offshore associated gas recovery challenges are due to concerns like limited engineering space, equipment design complexity, and safety concerns.

Potential changes are characterized by the use of module and off-site construction to facilitate fast site deployment and reduce site construction complexity of prefabricated systems, a recovery miniaturized system that is reliable and adaptable to a variety of conditions and ensures close control of recovery rates, the use of MRVs and deployment of real-time systems to obtain compliance and certifications for carbon reduction, and the use of protective systems in safety management that are explosion protection, leakage protection, and extreme environment protection systems.

With a stricter set of global regulations, recovery of offshore associated gas moved from “optional” to a “must have” in the market. It is essential for companies to cope with the technical and management challenges of engineering, equipment and safety to realize efficient emission reduction and economic benefits in compliance with offshore platform operation.