Debate rages on Atuabo gas quality
Early comments about the quality of the associated gas from the Jubilee oil field operations, which currently is piped to the Atuabo Gas Processing Plant for processing and onward delivery of dry gas to the Aboadze Thermal Plant for electricity generation, is causing some stir among industry observers.
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Some statements attributed to the Ghana National Gas Company (Ghana Gas), according to sources at the Volta River Authority (VRA) that Graphic Business spoke to, may either be misplaced or not exact in facts.
Ghana Gas reportedly claimed that gas from Jubilee, after acceptable quality assessments, is of superior quality based on the fact that natural gas around the world usually has significant amounts of acid gases such as Carbon Dioxide (CO2) and Hydrogen Sulphide (H2S) in them.
Atuabo gas, however, has very little carbon dioxide and absolutely no hydrogen sulphide, implying it will cost less to process Atuabo gas for other uses than natural gas imports from Nigeria that the country currently uses for the purpose.
Because of its quality, gas from Atuabo was not taken through all the filtration systems at Aboadze Thermal Plant before being injected into the turbines.
Ghana Gas claimed that four out of the five filtration processes that Nigeria gas goes through are skipped with Atuabo gas going to the last stage of filtration before use instead of all the five filtration systems built for WAGP gas.
Another issue attributed to Ghana Gas is about the delivering bar pressure of Atuabo gas, which it claimed is almost twice that of gas from the WAGP for similar volumes.
Yet, another issue raised by Ghana Gas is the heating value of local gas, which they claimed is superior, compared to Nigerian gas.
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VRA engineers have, however, questioned the veracity of some of these claims and their implications on perceived benefits to the country.
Natural & associated gas fields
They explained that comparing Jubilee’s associated gas to Nigeria’s dedicated natural gas field could be a case of apples and oranges, simply because the producer in the latter was able to control what was coming from the reservoir underground, while for the Jubilee operations the gas was a by-product of oil production which brought it out with many other substances; “in the case of the associated gas, as it is in the case of Ghana, whatever comes out of the well in association with the oil is what is sent to the processing plant onshore.”
It was therefore wrong to compare gas from the dedicated field in Nigeria to associated gas in Ghana, which meant different composition and have their own merits and demerits.
This also dovetails into the case of gas delivered from Atuabo, in which the heating value before use was very high compared to Nigerian gas. “In the case of the Ghana Gas after receipt of the gas, VRA has to go the extra mile to heat it to about 46 degrees Celsius before using,” a VRA engineer told Graphic Business.
“Therefore, in terms of heating value, the gas from Nigeria is always better and high in quality and the statement made by Ghana Gas that their product’s heating value was high is not entirely true. The quality of not up to standard and we have to work on the gas from Atuabo devoting extra energy to heat it to dry,” he explained.
The source explained that heating to that high level before using it meant that the gas from Ghana Gas has a low quality and contains a lot of wetness, “however in case of Nigeria gas, you don’t have to heat that much.”
The VRA engineers said it was also false, the claim that the gas from Ghana undergoes less filtration. “The filtration system at the VRA Aboadze is such that no matter the quality of any of the fuel, one cannot bypass any of the stages.”
The claim that gas from Atuabo skips all the four stages and undergoes only the final stage was not true. They said, “It must be on record that nothing is bypassed. In VRA, our checks are rigorous and we do not take anything for granted.”
Ghana’s daily gas needs
A source at VRA explained that Ghana’s daily gas requirements, if all the generating units were working, is more than 470 million standard cubic feet (mmscf) and it was a wrong time to start comparing and passing comments that were factually wrong.
It said about 60mmscf currently from Atuabo was being used to generate 185 megawatts (MW) of power at the two thermal units at Aboadze.
On a positive note it said for the first time in Aboadze’s history, its turbines, which had never generated above 70MW since their inauguration, were now generating more than 100MW.
“What we must understand here, however, is that Ghana Gas is still at the commissioning stage and is yet to attain plateau production, and therefore, as a country, we must be very cautious in our expectations.”
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Bar pressure
They said it is true that the delivering bar pressure of Atuabo gas was almost twice that of WAGP for the same volume of gas, but there were technical reasons to that which had nothing to do with quality.
They explained that the 678 kilometre West African Gas Pipeline (WAGP) links into the existing Escravos-Lagos pipeline at the Nigeria Gas Company’s Itoki Natural Gas Export Terminal in Nigeria and proceeds to a beachhead in Lagos.
And that from there it moves offshore to Takoradi, with gas delivery laterals from the main line extending to Cotonou (Benin), Lome (Togo) and Tema (Ghana).
The Escravos-Lagos pipeline system had a capacity of 800mmscfd, and the WAPCo system with initial volume of 170 mmscfd and peaks over time at a capacity of 460 mmscfd.
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This, they said, was a very huge size in terms of line pressure pack for delivery of gas to the final consumers for energy generation.
Also the size of the pipeline from Nigeria was bigger than that of Ghana Gas. Therefore, the bar pressure that Ghana Gas claimed was better than that of Nigeria was true because of distance and size of the lines.
While the Nigeria gas travels more than 678km to Ghana and starts building pressure in jumbo pipelines, gas from Ghana travels only 110km through smaller pipelines from Atuabo to Aboadze.
“The explanation is, when there is a compressor failure at Atuabo we at VRA have to shut down after an hour. However, due to the size of the gas pipeline from Nigeria, I can tell you on authority that we can depend on the pressure for more than three days before shutting down when Nigeria’s pressure goes down,” it said.
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Industry observers say what Ghana should be talking about was the extent of saving the country would be making for replacing the light crude with gas and that even though what was coming from Nigeria was not up to expectation both in terms of volumes and reliability, it should not be downplayed, since Ghana still does not have enough gas to make it self-sufficient.