Petroleum Engineering

Biography

Biography: Bjørn Kvamme

Abstract

The total global energy of CH₄ trapped in crystalline form as hydrates is huge and may exceed twice the amount of energy of known sources of conventional fossil fuels. Most of the natural gas hydrates found in nature are from biological degradation of organic material in the upper few hundred meters and correspondingly high purity of CH₄. These hydrates forms structure I hydrate, which contains a ratio of 1:3 of small to large cavities. The small cavity is very well stabilized by CH₄ while CO₂ fits the largest cavity better, and the water is having stronger short range interactions with CO₂ than CH₄. CO₂ gas or liquid that is brought in contact with CH₄ hydrate will therefore replace the CH₄ in most of the large cavities. This is possible through two mechanisms, a solid state direct conversion and a second mechanism in which CO₂ form a new hydrate with free pore water. The released heat from this hydrate formation assists in dissociating the in situ CH₄ hydrate. Substantial amounts of N₂ (often as high as 80% by volume) is proposed as one solution for reduced hydrate plugging and increased gas permeability. In this study we examine the minimum limits of CO₂ content for ability to form new hydrate from liquid water and injected gas, and also how this changes with small impurities of H₂S. It is found that even as small amounts of H₂S as 1% can substantially increase the ability of injection gas to form new hydrate, as compared to same mixture without H₂S.