Zheng Rong Chong
National University of Singapore, Singapore
Zheng Rong Chong is a PhD candidate in the Department of Chemical and Biomolecular Engineering at the National University of Singapore. His research interest is in the area of experimental investigation on energy recovery from natural gas hydrates.
Natural gas hydrates found beneath permafrost and continental margin have been regarded as a potential source of future energy. Driven by the abundance of hydrate resources (~3000 TCM), a number of scientific production tests and experimental studies have been conducted to elucidate the production behavior from hydrate bearing layers. However, due to the complexity of events that occur simultaneously during hydrate dissociation in porous media (e.g., multiphase transport across porous media of varying porosity, secondary hydrate formation, etc.), the current understanding on the gas and water production behavior from hydrate bearing sediment is still limited. Therefore, more experimental data is required to calibrate the reservoir simulators. In this study, we compared gas and water production kinetics from hydrate bearing sediments with 40% hydrate saturation between no well (N1-N3) and horizontal well (H1-H3) configuration via depressurization. A miniature horizontal production wellbore with multiple boreholes of 2 mm diameter was incorporated within the hydrate bearing sand to investigate how it would alter gas and water production. The surrounding temperature was 281.5 K, and 3 bottom hole pressures (3.5, 4.0 and 4.5 MPa) were experimented. Our experimental results clearly shown that gas and water production kinetics were significantly affected by the incorporation of wellbore: gas production was prolonged to ~10 hour at 4.5 MPa condition; whereas water production ceased within 2 hours-demonstrating that incorporation of flow conduit indeed facilitated gas to flow out of the sediment. For all experimental pressures, the incorporation of horizontal flow conduits (H1-H3) caused an increase in cumulative gas production by ~10% and a decrease in water production by ~20%. The simultaneous increase in gas production and decrease in water production is desirable as water is produced as a by-product during field exploration, consuming pumping power and requiring treatment before its discharge.