|Photo credit: Statoil|
For both operators and refiners alike, it is crucial to monitor levels of contaminants in crude oil. Residual levels of certain chemicals used during production are common. But the presence of these chemicals – such as hydrate inhibitors – can affect the quality and, crucially, the value of the crude and cause costly delays to downstream activities.
The Mongstad refinery in Norway, owned and operated by Statoil, has the capacity to process almost 12 million tonnes of crude oil per year. On arrival at the refinery, the crude is tested for the presence of such contaminants before processing. While traditionally this analysis was carried out using gas chromatography (GC), a trial of LUX Assure’s OMMICA™ MEG analysis kits led to an operational transformation and crucial time savings at Statoil’s Mongstad refinery.
One of the biggest deepwater flow assurance challenges for operators is to prevent the build-up of hydrate formations. These are ice-like solids that form when water and natural gas combine under low temperature, high pressure conditions and can plug the flow, causing a potentially hazardous build-up of pressure. They are particularly problematic when crudes are exposed to cold temperatures, as in deepwater operations.
During deepwater production it is common for operators to inject chemical hydrate inhibitors into pipelines to prevent this build-up. One chemical used for hydrate inhibition is mono-ethylene glycol (MEG). This thermodynamic hydrate inhibitor is continually dosed to compete with the hydrate structure for water molecules. This suppresses the point at which hydrates form, in a similar way to how antifreeze protects against water forming into ice.
For new installations, it is common for the flow rates of water, oil or gas to change repeatedly, requiring continuous adjustment to MEG dosages. MEG reclamation equipment can also have a ‘running in’ period before it becomes accustomed to the produced fluid and begins to operate efficiently, meaning the produced oil is likely to contain higher MEG concentrations.
For the producer, this outflow of MEG from the system comes at a high cost. For an installation producing approximately 10,000 barrels per day (bpd), losses of only 100 ppm MEG to the oil can equate to an additional cost of ca. £100,000 per year to replace.
The potential cost to refineries processing this crude can be even greater. These hydrate inhibitors, essential to keeping upstream production flowing, can stop downstream activities in their tracks. To cleanse the crude of the contaminant chemicals, the oil passes through a sensitive system of micro-organism sieve beds, which can be damaged when exposed to high levels of hydrate inhibition chemicals.
Thus, it is essential to set acceptable contamination levels for incoming crude – and ensure penalties are imposed for exceeding these – to protect the refinery from lost time and income due to damages. Often these waiver fees and penalties amount to between $2 and $5 dollars a barrel, and in the past have accrued to single individual fines of around $3.75 million. However, without an accurate, reliable and timely method for measuring the MEG content, this system can fall apart. With operators being cautiously over-charged in waiver fees and refineries unknowingly subjecting themselves to high risk shipments, there is commitment from both parties to find a technology that provides accurate and timely measurements of MEG content within every shipment.
A testing dilemma
In May 2016, Statoil’s Mongstad plant was set to receive a crude shipment from a newly commissioned oil platform on the Norwegian Continental Shelf.
The plant was committed to testing shipments for their MEG content before acceptance. The standard industry approach for testing MEG levels in oil is GC – a widely recognised chemical process which for some time had no competitive equivalent.
For many operators, GC units (GCs) are not available onsite as space comes at a premium and the highly sensitive machinery is unsuited for a rugged life offshore. Instead, arrangements must be made to transport the samples to an offsite lab. For those few that do have a GC unit onsite, often situated in onshore processing plants, the maintenance and upkeep often cause operational issues.
When the situation within the pipe can change within a matter of hours, it is important to test regularly – potentially 14 times a day at start-up. In effect, this means the results could expire before they even reach the onshore lab – let alone by the time the operators receive them three to four weeks later.
Although Statoil’s Mongstad refinery had onsite GC facilities, the GC unit was out of use whilst waiting on the arrival of a replacement component. It was crucial that analyses of multiple samples could be undertaken quickly, as until the results were received the plant was unable to accept the crude shipment for risk of damaging and contaminating its equipment.
To wait for the GC unit to be repaired would mean potential costly delays. If the oil tanker was unable to complete delivery as scheduled, thousands of dollars in demurrage fees could be incurred. With such a high potential risk to the refinery’s equipment however, accepting the crude without knowing the MEG concentration in the oil was simply not an option.
To avoid such a situation, Statoil required a testing method that could match the accuracy and confidence that GC would normally deliver, but in a timescale it could not.
A different approach
Statoil was an investor at an earlier stage of LUX Assure’s evolution. This relationship had included product demonstrations to various departments within the operator, one of which remembered LUX Assure and its unique OMMICA technology.
OMMICA is a simple, colourimetric onsite (offshore and onshore) chemical testing kit that quickly and accurately measures MEG levels in oil, condensate or water. It works by using reagents that only react with the chemical it is designed to assess – in this case MEG – and can be added directly to samples without the need for a manual water separation step. While saving time, this also preserves the integrity of testing as it prevents other chemicals from interfering with the results.
LUX Assure provides detailed instructions, training and guidance to get clients up-to-speed quickly. OMMICA enables multiple samples to be tested simultaneously and, crucially, gives accurate results in near-real time. These key features enable operators and refiners to make quick, informed decisions to benefit their operations, increase efficiency and save money.
Simple, speedy results
The speed and simplicity of the OMMICA testing meant that Monstad had the data it needed to make decisions on the processing and segregation of the cargo crude prior to entering the refinery. This resulted in demurrage and storage savings, and negated the need for additional process steps to ensure MEG in oil levels were within specification.
As this was the first time Statoil had used the OMMICA testing kits, the refinery sent additional samples to an independent GC lab in Holland to verify the results. The results showed a close correlation between OMMICA and GC – less than 20 per cent difference was found between the two methods, using non-identical samples in different labs. This accuracy validated the continued use of the OMMICA technology at Mongstad, and is considered an acceptable variance across the oil and gas industry.
For Statoil, this first use of OMMICA was a turning point. The successful correlation with the GC results, combined with the performance of OMMICa and the service provided by the LUX Assure team, gave Statoil’s Mongstad refinery the confidence to adopt OMMICA for future testing of inbound crude and move away from relying on traditional GC methods.
Taking a broader view, OMMICA technology is well placed to help both operators and refiners with a number of developing industry trends. Operators are exploring deeper waters, with even greater requirements for hydrate inhibition, whilst the industry at large continues to adjust to $50 – $60 oil.
To keep a tight handle on capex and opex, the industry must keep looking for new methods and efficiency savings wherever possible, in every area of operations. As non-specialist personnel can operate OMMICA technology, it is not only more cost-effective than a traditional GC in terms of capex, but the related manpower required to use it (opex).
It was OMMICA’s speed and accuracy that made the MEG in oil testing kit essential for Mongstad in this particular example. OMMICA technology is a rare example of a win-win solution, one that is both more cost-effective than its competition while providing an as-accurate and quicker result.