DESIGNING A RESERVOIR FLOW RATE EXPERIMENT FOR THE GOM HYDRATE JIP LEG II LWD DRILLING

The Deep Water Gulf of Mexico (GOM) may contain a large hydrate resource. Short term production profiles (from modeling) for a hydrate deposit that was logged in the GOM are presented along with the feasibility of using traditional well test analysis tool to obtain production parameters that can be used to further refine the reservoir model estimates. The presence of the solid hydrate phase in hydrate reservoir not only poses challenges in production but also in designing flow tests. Unlike conventional well flow tests, the time scale needed to produce methane gas from hydrate formation may take longer time. This is because the effective permeability in hydrate formation is initially very low. Hence, there is a need to establish a flow path as a result of hydrate dissociation with change in pressure and temperature. In this paper, we attempted to determine the type and duration of a well test that could provide the needed information to support and validate production modeling of gas hydrate deposits. The investigated parameters in this study included the effects of permeability and hydrate saturation as a function of the duration of the flow test. These parameters, initial hydrate saturation and absolute permeability, appear to be most influential in gas production from hydrate formation based on experimental design. The results also indicate that production using a constant bottom hole pressure is the most appropriate method to impact hydrate dissociation by depressurization for flow testing because of the relatively rapid response and early release of gas. Reasonable values for water and gas effective permeability were obtained from short term flow tests (3 to 15 days) but was not possible to recognize changes in transient pressure plots to identify regions of varying saturations in the studied system. Furthermore, it was not feasible to calculate absolute permeability values for the studied system as the range of fluid saturation was in an area of high relative permeability uncertainty. This may be due to the fact that the conventional well test analysis tool does not capture underlying physics describing hydrate systems. Hence, for proper analysis, history matching using the well test data and a proper hydrate simulator are recommended.