Gas Production from Methane Hydrate Reservoirs in Different Well Configurations: A Case Study in the Conditions of the Black Sea

Gas hydrates are considered "near-future energy resources" due to their vast existence all around the world. Recently, China has tested gas production from methane hydrate-bearing clayey silts via horizontal well technology for the first time. This study aims to investigate the effect of well configuration on gas production from the Black Sea gas hydrates. Mainly, two different hydrate-bearing models (single-layer homogeneous hydrate-bearing sands and multilayer hydrate-bearing turbidite) were constructed in this study. Gas production numerical simulations were held using the TOUGH + HYDRATE simulator. Gas production via the horizontal well in single-layer homogeneous hydrate-bearing sand was higher compared to the vertical well case at early stages. However, fast depressurization via the horizontal well caused a rapid decline in reservoir temperature and hydrate dissociation rate. Then, local hydrate reformation was detected near the wellbore. In the later periods of gas production, higher gas production with the vertical well was obtained. The clay layers in the heterogeneous methane hydrate reservoirs (alternating sand and clay layers in turbidite) behave like a barrier to depressurization with a horizontal well.