> But if that is not producing methane in the reservoir then in will be producing methane elsewhere
Not necessarily. The article explains methane production as so:
[...] bacteria eating this dead organic matter to depend on other molecules containing oxygen. These include nitrate, phosphate, sulfate, and carbon dioxide. The least appealing molecule to breathe for these microbes is carbon dioxide because it requires the greatest energy to break the molecule apart to access the oxygen. When these microbes have no choice than to breathe carbon dioxide, a process called “methanogenesis” occurs.
Not necessarily. The article explains methane production as so:
[...] bacteria eating this dead organic matter to depend on other molecules containing oxygen. These include nitrate, phosphate, sulfate, and carbon dioxide. The least appealing molecule to breathe for these microbes is carbon dioxide because it requires the greatest energy to break the molecule apart to access the oxygen. When these microbes have no choice than to breathe carbon dioxide, a process called “methanogenesis” occurs.