Fracturing Methane Hydrate in Sand: A Review of the Current Status

Abstract Natural occurring methane hydrate (MH) is found abundantly in sediments and rocks under stable thermodynamic conditions. The majority of this resource is located under the permafrost layer and in the shallow depths of the seafloor in the deepwater regions. Over the past two decades, a variety of efforts were dedicated in laboratory researches and field production tests using different methods to examine the best production strategy that is economically viable for commercialization. In order to produce gas, the solid methane hydrate in pores of sediment or rock will need to be dissociated either by reducing the pore pressure, increasing the temperature, injection of inhibitors, or undergo gas exchange using carbon dioxide. It is possible to have a combination of these options in the gas production. Currently, the depressurization method is deemed the most efficient way to produce gas. The key controlling factor in dissociating, exchanging or producing gas from methane hydrate is the flow conductivity through the pores of the hydrate-bearing layer. Larger contact exposure area between solid methane hydrate to the fluid pore pressure enables more dissociation to occur using the methods above. In this aspect, the creation of artificial fracture in hydrate-bearing layers is thought to promote a better dissociation process. This idea has surfaced with numerous efforts from the research community to explore its feasibility. There are multiple technical challenges and uncertainties to address if methane hydrate in sand can be fractured artificially. These challenges and the recent progressions in identifying/determining its fracture properties are discussed with some future considerations required to move towards the prospect of introducing artificial fractures for gas production purposes.