Mallik 2002 gas hydrate production research well program: Numerical simulation studies for analyzing the mechanism of gas production from methane hydrate reservoirs

The results of the thermal production test and Modular Formation Dynamics Tester (MDT) tests conducted at the Mallik 5L-38 gas hydrate production research well were analyzed, using the numerical simulator coded for gas hydrate reservoirs. The reservoir models were constructed as a series of grid blocks. In the simulation for the thermal production test, the reservoir model was tuned through history matching, by introducing the concept that part of the circulating hot water might have invaded into the reservoir, which resulted in the excellent agreement between observed and simulated performances. Using the history-matched reservoir model, sensitivity simulation and prediction of future performances were conducted to examine the effects of uncertain reservoir parameters and the gas hydrate dissociation/production methods on the recovery of gas from the Mallik reservoir. In the MDT test simulation, to investigate the applicability of conventional pressure transient test analysis methods, bottomhole pressure responses during MDT tests in hypothetical and actual gas hydrate zones were simulated and were then analyzed by the conventional analysis methods. This study revealed that conventional methods might indicate the average effective permeability over the area of gas hydrate dissociation while the estimation of the radius of gas hydrate dissociation was quite imprecise.