When the oil price can rise 50% in six months, as it has just done, or drop nearly $70 a barrel in the space of 18 months, as it did between July 2014 and January 2016, it’s right to regard the global market as volatile.
Given this scenario, and the possibility this will be the new normal, upstream operators would be wise to balance strategic investment with fundamental frugality. This is where effective corrosion control comes in. The cost to the oil and gas industry of untreated corrosion is considerable.
The annual cost is in the trillions of dollars across all industries globally and the cost to oil and gas pipelines alone is more than $500mn per year. But, as Dr Derek McNaughtan, principle corrosion engineer at Asset Integrity Engineering reveals, severe deterioration can occur in multiple areas at oil and gas facilities.
“The equipment susceptible to corrosion in oil and gas installations is any that experiences the presence of water with a susceptible material in that particular environment, whether externally or internally. Internally equipment such as static pressure vessels, pipework and heat exchangers can experience significant corrosion under the right conditions.
“The degree of degradation depends on the operating conditions and is the reason understanding how the process equipment operates and what materials, barriers and controls are in place is critical.”
McNaughtan also explains that some measures actually utilised for certain types of corrosion can inadvertently lead to another form of deterioration, “A good example is where a system has gone from a sweet environment to a sour environment over time. This system may have had a corrosion inhibitor to prevent carbon dioxide (CO2) corrosion but is ineffective in the presence of hydrogen sulphide (H2S), resulting in localised pitting that may not be detected.”
Typically, offshore operations have always carried a greater risk of corrosion due to the immersion of equipment in seawater. Effective cathodic protection can guard against this according to McNaughtan but other risks exist – particularly within the Middle East.
Ken Feather, chief marketing officer, TGT Oilfield Services, says that well systems are “elaborate subterranean plumbing systems” made of carbon steel and, within the region, are subject to numerous corrosive fluids, “Middle East assets are especially vulnerable because some reservoirs contain high concentrations of H2S, and region-wide aquifer systems such as the Umm er Radhuma-Dammam can eventually eat away at wells from the outside. The degradation of wellbore tubulars and metal barriers is a major threat to well integrity. This is why many Middle East operators are ramping up integrity management programmes.”
Operators across all regions were impacted by the oil price slump that commenced in 2014 and lasted for more than two years and many now recognise leaner, more price resistant business models include a strategy that seeks to optimise the life of their assets as a preferred option to making substantial investments. Effective corrosion control has to be an integral part of this for obvious reasons as Andy Duncan, lead consultant, production and integrity at Intertek explains:
“A consequence of not rigorously implementing corrosion management systems is premature failure of equipment, costly downtime, costly repairs and the likelihood of premature closure of assets which could otherwise produce hydrocarbons long into the future, thereby taking away future income from companies, states and individuals.”
But Duncan also believes the downturn could have led some firms to action cost-saving measures that potentially “compromised maintenance schedules and effective corrosion control, which may ultimately result in increased failures.”
This is a key point. Optimising the life of assets and ensuring equipment is safe and reliable is not only about deciding to incorporate a corrosion control strategy – but doing so at the right time, as McNaughtan underlines, “Corrosion control is a proactive strategy that cannot recover damage that has already been incurred.
“For this reason, it cannot be viewed as a life extension strategy, but rather as a preservation and process safety control strategy that should be applied throughout the life-of-plant. The control of corrosion threats basically translates into the control of corrosion rates and this will automatically lead to life optimisation of the plant.”
The oil and gas industry is not only about preserving the status quo but also pushing forwards with innovative solutions and techniques. Therefore, developing materials that are not as potentially corrosive as the widely used carbon steel, which is employed in many applications, including most piping systems, could potentially save vast sums across multiple industries.
Duncan suggests that as exploration and production moves forwards into new, more challenging environments, its associated equipment needs to move with it.
“Most of the world’s readily accessible hydrocarbon resources have been identified and the industry has been moving into deeper waters, harsher environments, high reservoir pressures and temperatures, higher CO2 and H2S containing hydrocarbons. These increasingly aggressive environments mean the industry has been investing in alternatives to carbon steels such as metals alloyed with chrome, nickel and molybdenum.”
But as McNaughtan points out, these corrosion resistant alloys are expensive and so enhanced, higher performance corrosion inhibitors to protect carbon steel are often still the best option.
In recent years, developments such as the supervisory control and data acquisition (SCADA) control system architecture has helped operators keep on top of the critical task of checking and monitoring their equipment for potential failings. Such tools are vital when assessing corrosion in wells, as Feather explains, “There is no doubt that continuous monitoring provides the safest mode of surveillance, but the challenge in diagnosing corrosion within well systems downhole is access and instrumentation. The concentric steel tubes, casing, cement and other components that make up the well system extend for kilometres underground and the concentric geometry means for example that corroded outer casings are masked. This is why ‘through-barrier’ diagnostic systems are so important coupled with a proactive strategy of routine diagnostic interventions.”
Further augmentations to diagnostic capabilities will offer operators tighter control over their corrosion management systems and this should help bring down the vast losses that equipment degradation causes. McNaughtan says his firm for example, is looking to exploit the benefits of real-time cloud-based solutions:
“…most facilities already have SCADA systems to which online monitoring equipment can be integrated with relative ease. Historically one of the greatest barriers to condition monitoring has arguably been security protocols of local networks. However, as SCADA integrates with the Internet of Things, real-time cloud-based monitoring will completely lift this barrier in the foreseeable future.”
