Production modeling and forecasting of natural gas production from Barrow methane hydrate deposits

Abstract

In this work, state-of-the-art existing simulation models of East Barrow and Walakpa natural gas fields with associated gas hydrates were rebuilt, tuned with additional data (some of the data used were from the Mt. Elbert Well, which significantly improved earlier models), and updated in terms of production data and history matching. Fluid contacts, saturations and hydrate dissociation/formation reactions were initialized for both models, actual production was matched and planned wells were placed accordingly. For each model, a gas hydrate saturation sensitivity study was performed. Simulation models were run and production forecasts for Walakpa field were made. There is a clear picture of East Barrow field behavior, but the Walakpa model still involves significant approximations. Additional log data from new wells planned in the Walakpa field will reduce reservoir properties uncertainty and make the model a more realistic reservoir management tool. A well choking study was performed on a hypothetical simplistic radial simulation grid with a vertical well. It was discovered that vertical gas wells drilled close to a hydrate zone tend to die due to hydrate blockage. Higher gas rates revealed improved production, but faster flow rate decline because of hydrate reformation. Horizontal wells could mitigate this problem due to their lower pressure drop per unit length of completed interval. They are also capable of higher production at lower drawdown. Since higher rate causes faster choking due to hydrate reformation, intermittent reduction of the flow rate is recommended for vertical wells in order to mitigate or at least delay the choking problem. Overall, both horizontal and vertical well designs are suitable for natural gas production from hydrate reservoirs.