Enhancement of gas production from low-permeability hydrate by radially branched horizontal well: Shenhu Area, South China Sea.

A high gas production rate is critical for commercial exploitation of hydrate. Most marine hydrates deposit in the silty or clay sediments with low permeability, and gas production rate is low. Herein, a novel deployment of well, radial three-branch horizontal well was numerically investigated to enhance the gas production. A 3D geological model was established based on field trial in the Shenhu Area of the South China Sea. The simulation showed similar gas and water production for single and multi-branch horizontal wells with same length of 250 m. The depth in which well deployed dramatically affects the gas and water production, and which increases with the length of multi-branch well. Meanwhile the ratio of free gas originally distributed in three-phase and gas layers also increases with the length, which is 50% for 1200 m well. The interference around the intersection of branches enhances temperature recovery and the dissociation of underlying hydrates. The standard energy return on investment analysis shows that the economic potential increases linearly with the length of multi-branch well and obviously depends on the content of initial free gas. However, the production balances investment confines only to tens or hundreds of days for all model scenarios. • A novel radial three-branch horizontal well is adopted to investigate the enhancement of gas production from hydrate. • Depth of multi-branch well (various contact formation) highly affects gas production. • The deployment of the horizontal well within three-phase layer is feasible for high gas production. • Interference of branches enhances temperature recovery rather than gas recovery. • Cost-benefit balance is analyzed and further technical improvement is needed to meet the economic criterion. [ABSTRACT FROM AUTHOR]