Oil giant ExxonMobil, which has for some time been plagued by issues with its flash gas compressor aboard the Liza Destiny Floating Production Storage and Offloading (FPSO) vessel, has now brought the compressor online and has been able to cut down its flaring by 96 per cent.
The Liza Destiny FPSO
This was announced by Exxon’s Production Manager Mike Ryan during an interview with the company’s Governance and Public Affairs Advisor Janelle Persaud. Ryan further explained that there are six gas compressors operational, including the flash gas compressor, two main ones and injection gas compressor.
The Production Manager said that Exxon is currently flaring approximately 6 million cubic feet per day. Ryan went on to explain why they have not been able to reduce the flaring to pilot levels yet.
“What we found with this most recent testing that we did, when we completed phase one and two testing, is that we’re still seeing some of that axial vibration in the third stage compressor. And as you recall, that axial vibration was causing some damage in the machine and that’s why we had to send it back to Germany.”
“What our focus is right now and it was through our extensive testing and modelling that we did during the phase one, phase two, is to find the right level of the operation such that we minimise the vibration, so that we can keep the machine running, while also minimising flaring,” Ryan said.
Ryan said that before the flash gas compressor came online, they were using or injecting 88 to 90 per cent of gas. He acknowledged that while they weren’t completely there, they have made significant improvements. He said the flaring of gas has been reduced by approximately 96 per cent.
The manager made it clear that Exxon takes its environmental responsibilities seriously. That being said, the Production Manager also reiterated his disappointment with the gas compressor’s malfunction.
“That’s very important to us. We work every day on all our parameters. Not just on greenhouse gas emissions, but on all our areas. On discharges, making sure we’re transferring the oil from the FPSO to the tankers efficiently. And we’ve been extremely successful on all those fronts.”
“So, it’s part of our DNA, to ensure that we protect the environment. The numbers we see here are generally in line with what we estimate in the EIA (Environmental Impact Assessment). That being said, I’m very disappointed with the performance of the flash gas compressor,” he said.
In the latter part of January 2021, Exxon’s subsidiary, Esso Exploration & Production Guyana Limited (EEPGL) had announced that it was experiencing technical problems with the seal on Liza Destiny’s flash gas compressor. The problem resulted in Exxon having to reduce its production and also conduct routine flaring.
It was subsequently revealed that Exxon had been flaring 16 million cubic feet of gas per day, an increase from the volume of flaring the company conducted last year which reportedly ranged between 12 and 15 million cubic feet. The third stage discharge silencer, a key component of the flash gas compression system for the <<<Liza Destiny>>>, was a key factor in the malfunction of the compressor.
The silencer eventually had to be upgraded. Additionally, a redesigned third stage discharge venturi had to also be manufactured. These issues had resulted in oil production on the Liza Destiny FPSO in the Stabroek Block offshore Guyana being reduced to 110,000 barrels per day (bpd) at one point.
When it comes to the future, Natural Resources Minister Vickram Bharrat has said that EEPGL will switch the manufacturer of the compressor equipment it uses, to ensure there are no malfunctions that lead to excess flaring during future projects. (G3)
