Effect of Polyethylene Glycol Aqueous Solution on Methane Production from an Artificial Hydrate Reservoir

Abstract

Abstract Natural gas hydrates have gained a huge attention as a potential future energy source. Reserches and pilot operations on methane recovery from hydrate reservoirs are going on worldwide. In the present work, an artificial hydrate reservoir has been developed in lab scale using silica sand of 0.16 mm particle size, distilled water and methane gas inside a high-pressure reactor. The effectiveness of polyethylene glycol (PEG) as an inhibitor for the dissociation of natural gas hydrate has been investigated. A porous sand bed of 70% water saturation has been prepared inside a high-pressure reactor and then charged with methane gas at 8 MPa. After the hydrate formation in the porous bed, for dissociation of the hydrate reservoir, PEG aqueous solution has been injected into the hydrate reservoir using a syringe pump. The pressure of the reactor has been maintained in between the equilibrium pressure of pure methane hydrate and methane hydrate in the presence of PEG using a back-pressure regulator. The injection of PEG aqueous solution has been performed at 0.4 mass fraction for methane recovery from the artificial hydrate reservoir. PEG-200 aqueous solution has shown a methane gas production ratio of 47.38%. This work provides a practical approach to use polymer as an effective inhibitor for the production of methane from hydrate reservoir especially for low temperature and permafrost hydrate-bearing zones. This is the first work that uses an environmental friendly polymer as inhibitor for the hydrate dissociation for methane production from a natural gas hydrate. It has been observed that PEG performs well as a thermodynamic and kinetic inhibitor. In addition, PEG is having −65oC freezing point, which is more than a commercial inhibitor, ethylene glycol (-13.4oC), therefore using PEG as an inhibitor is more beneficial for the production of gas from a low-temperature hydrate reservoirs.