Applied Energy, Vol.214, 117-130, 2018
Effect of horizontal wellbore on the production behavior from marine hydrate bearing sediment
Natural gas hydrate is a potentially vast energy resource for the future. However, the fundamental behavior of hydrate dissociation during energy recovery is not fully understood due to the complex interplay of phase change and multiphase flow within porous media. In this study, the effect of horizontal wellbore incorporation on the simultaneous gas and water production during the dissociation of methane hydrates in sandy sediment (0.1-0.5 mm) was investigated. A horizontal perforated wellbore was incorporated within water saturated hydrate bearing sediments of 40% hydrate, 55% aqueous and 5% gaseous phase saturation to mimic marine hydrate sediments, and the gas and water production behavior from horizontal wellbore (HW) was compared with the base case (without well) at 3 bottom hole pressures (BHPs) of 3.5, 4.0, and 4.5 MPa under a constant surrounding temperature of 281.5 K. The evolution of temperature across 12 measured locations within the 1 L sediment demonstrated the significant effect of horizontal wellbore incorporation on heat transfer within sediment. Through the incorporation of horizontal wellbore, a continuous production of gas was observed for an extended period of time as compared to the base cases without a well. The resulting cumulative gas production was enhanced by 5.5-10% at various BHPs; whereas the cumulative water production was significantly reduced by 30.8-36.9% at different BHPs from the base cases. By estimating the percentage of hydrate dissociated, it was found that the incorporation of horizontal wellbore in the current apparatus caused a slower hydrate dissociation, as reflected by a longer time to dissociate 50% (t(50,h)) and 90% (t(90,h)) of the hydrates. This study demonstrates the potential of horizontal wellbore incorporation to simultaneously enhance gas production and reduce water production, unveiling a future direction in optimizing gas recovery from hydrate reservoirs through innovative wellbore design, configurations and well placement strategies.