(685e) Gas Production Strategies and the Impact of Layers on Gas Recovery from Gas Hydrate Reservoir Using the Numerical Simulations

The gas hydrates can be the efficient alternative to replace the depleting conventional energy production method. The energy demand of a growing country like India can be alleviated by extracting the extensive methane gas present in the gas hydrate reservoirs found at multiple sites. The possibility of the gas production form methane hydrate reservoir is evident from the short-term field tests; however, the reservoir complexities still challenge the long-term production. The prognostication of the methane production from the gas hydrate reservoirs is usually done by simulation studies to address the challenges in the long-term productions. Therefore, the production analysis requires the grasp of geological, technical, and economical factors controlling the methane production potential of these reservoirs. In the present work we analyze the efficient production method as well as the gas production behavior due to different well arrangements and the well locations. We also study the impact of layering on the percent gas recovery from the gas hydrate reservoir. A 3-D, class-2 oceanic reservoir block underlain by an infinite aquifer layer is modeled in this work.

An In-house, thermal 3-D finite volume legacy simulator is used with multicomponent- water, methane, and hydrate in four phases – gas, aqueous, hydrate and ice. Energy and mass balance equations are solved in space and time domain to compute the gas recovery from the gas hydrate reservoir. The unconfined reservoir becomes less responsive to the depressurization method for both the vertical as well as horizontal wells. Therefore, the warm water injector is a must along with the depressurization method to recover methane gas from an unconfined gas hydrate reservoir. The different well arrangements and well locations are explored using numerical simulations. The wells placed horizontally are more effective where gas recovery is 48% original gas in place (OGIP) compared to the gas recovery of 22% of OGIP for vertically placed wells. The location of the horizontal injector near the aquifer makes water convection easier and the gas recovery starts from the very beginning. The location of the injector in the low permeability hydrate layer makes the gas recovery difficult for initial days. We also investigate the impact of layering on the gas recovery from the gas hydrate reservoirs. The effective permeability of the topmost layer of hydrate where producer is located plays an important role in gas recovery. The infinite aquifer layer has impact on both the gas and the water recovery because the higher effective permeability of the water layer supports the pressure drop in the gas hydrate reservoir.