PNNL

Abstract

This study used experimental and numerical approaches to develop and demonstrate kinetic models representing the CH4/CO2/N2 hydrate-guest molecule exchange process that occurred at the Ignik Sikumi #1 Field Trial. Since the completion of the field trial, experimental and numerical investigations have sought to better understand observations in terms of CH4 production and changes to the hydrate bearing formation. Theses insights may help to effectively design CH4 production strategies from naturally occurring hydrates. This study presents results from a scoping experiment performed at conditions experienced during the trial (~1200 psi and 2°C) to collect data relating to the CH4 molecular exchange process. The experiment intentionally isolated the kinetic guest molecule exchange process from additional hydrate formation and mechanical changes to the hydrate bearing sand. Data was used to inform development of numerical models that were then used to fit key hydrate parameters (bound water saturation, kinetic formation constant, kinetic exchange constant, and preferential exchange weighting factors) and analyze experimental results. Results were in agreement with observations of preferential CO2/CH4 guest molecule exchange at Ignik Sikumi #1 and from previous experimental studies while providing quantitative estimates of changing hydrate compositions. Additionally, simulations confirmed hydrate behavior and composition profiles otherwise indirectly evidenced by experimental results.