Recovering Natural Gas from Gas Hydrates using Horizontal Wellbore

Abstract

Natural gas is a fossil fuel with the lowest carbon footprint. In nature, an enormous amount of natural gas exists as natural gas hydrates (NGH) – an ice-like solid compound composed of natural gas enclosed within crystalline water cages. However, due to the complexity of physical events that occur simultaneously during hydrate dissociation in sediments (e.g. multiphase transport through porous media), the current understanding on the gas and water production behavior from hydrate bearing sediment is still limited. To better elucidate the simultaneous gas/water production from hydrates, we developed an experimental setup capable of acquiring the kinetics of gas and water production and compared the production behavior between “no-well” and “horizontal wellbore” configurations. Hydrate bearing sands of ~40% hydrate saturation and > 50% aqueous saturation were formed to mimic oceanic hydrate reservoir. Under the same production pressure (4.0 MPa) and temperature (281.5 K), significant difference were observed in gas and water production – the horizontal well prolonged gas production and reduced water production. In the end of production stage, the cumulative gas production increased by 15.7% from 23.05 standard liter (SL) to 26.66 SL; whereas water production reduced by 54.7% from 196.1 mL to 88.9 mL. Our finding presents the opportunity to improve gas production and simultaneously mitigate water production through the tuning the borehole design parameters.