Enhanced Hydrate Inhibition in Alberta Gas Field

Abstract

Abstract Gas wells located in Southern Alberta, Canada pose challenges for well operators. High bottomhole pressure in new wells, low bottomhole temperatures and Joule-Thompson expansion cooling effect often lowering gas stream temperatures to below brine freezing create favorable conditions for formation of gas hydrates in the wells and transportation pipelines. The problems are aggravated during cold winter months when wells and pipelines have strong tendencies to plugging with hydrates and ice. Operators experience significant monetary losses due to disrupted production and have to spend considerable amount on chemicals and time to clean up hydrates from plugged wells and pipelines. With subcooling temperatures often exceeding 14°C, kinetic hydrate inhibitors are incapable of preventing hydrates formation. A typical solution to such severe hydrate problems is pumping massive amounts of methanol or glycols to the well and production lines. Adding large amounts of thermodynamic inhibitors creates problems by itself like oxygen corrosion or solvent induced scaling. Earlier work in the field indicated a possibility of synergism between thermodynamic hydrate inhibitors and Low Dosage Hydrate Inhibitors (LDHI). Systematic laboratory work was undertaken to explore possible synergistic effects between methanol and LDHI. A strong synergistic effect was discovered at a certain ratio of methanol and low molecular weight oligomer type hydrate inhibitor. These observations allowed a formulation of a superior hydrate inhibitor. Field results show the reduction up to 80% of the original and often insufficient methanol dosages. Due to this novel approach to hydrate problems, the operator experienced more trouble-free field operation and increased gas production, improved economics with less down time, lower total cost of chemicals and delivery.