DOWNHOLE CATALYTIC COMBUSTION- A TOOL FOR METHANE HYDRATE DISSOCIATION

William C. Pfefferle
Precision Combustion Inc., North Haven, CT

With DOE Small Business Innovation Research program support, Precision Combustion is developing a downhole catalytic combustor to generate heat for in-situ hydrate dissociation. Catalytic combustor technology provides the capability to burn fuels outside of their normal flammability limits and deliver a high heat release rate in an ultra-compact, movable device that is highly controllable and provides a high degree of operating flexibility. For Arctic locations, this approach will avoid heating permafrost.

The DOE Phase I program has confirmed the basic energy efficiency of the approach, with methane production predicted to be on the order of ten times combustion consumption assuming hydrate deposits containing at least ten volume percent hydrate. For hydrate beds of this concentration, heat losses to water and rock in downhole combustion are minimal compared to the energy required for hydrate dissociation. Even for hydrate beds with lower concentrations, net methane production can be substantial. For a required pressure of 1400 psi the typical energy requirement for gas and oxidant compression is calculated to consume about four percent of the product gas.

By injecting fluids from below the hydrate deposit all the heat must ultimately enter the deposit. Further, because the vapor pressure of water at the hydrate decomposition temperature is very low, combustion water condenses liberating the latent heat, i.e. the higher heating value of the methane fuel is captured, not just the lower heating value. In addition, since CO₂ hydrate is stable at the CH₄ hydrate dissociation temperature, the CO₂ from methane combustion can form CO₂ hydrate producing enough heat to liberate an equivalent amount of additional methane. If CO₂ is available for sequestration, use of an oxygen-CO₂ admixture for combustion greatly reduces energy requirements.

We will report on results from our DOE program and on plans for future work.