Experimental study on natural gas hydrate extraction with radial well depressurization

Natural gas hydrate is a potential alternative energy source for the future, and the low mining efficiency severely restricts its commercial utilization. The technology of radial wells is a newly proposed method for increasing the productivity of natural gas hydrates. To evaluate the effectiveness of this method, experimental studies were carried out to simulate the extraction of hydrate sediments in water-rich and gas-rich environments by vertical well depressurization and radial well depressurization. Results indicate that: for the extraction of gas-rich hydrate samples by depressurization, gas production behavior of vertical well and radial well is almost the same; for the small experimental scale and relatively high permeability of samples the pressure propagation patterns are similar when vertical wells and radial wells are applied. For the extraction of water-rich hydrate samples by depressurization: compared with that of vertical wells, the cumulative gas production and cumulative water production of radial wells at the end of the production cycle were increased by 20.16% and 38.98%, respectively; as a high conductivity channel, the radial well can increase the drainage area in the hydrate sediments and promote the propagation of pressure drop to the inside of the reactor, and ultimately accelerating the decomposition rate of hydrate; besides, the temperature drop is more significant when the radial well is used, which provides more sensible heat for the decomposition of hydrates and further improves the efficiency of hydrate production.