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.

Experimental Study on the Propagation Characteristics of Hydraulic Fracture in Clayey-Silt Sediments

“…Hydraulic fracturing is an effective stimulation method for increasing the permeability in unconventional resources. It could create artificial fractures in gas hydrate layers, strengthen the seepage capacity between wellbore and dissociation boundary, accelerate pressure propagation, improve thermal transfer efficiency [14,26,27], and enlarge the hydrate dissociation area so as to promote gas and water to rapidly flow to the wellbore through fractures and enhance well production of low-permeability reservoirs (Figure 1).…”

Gas production from a silty hydrate reservoir in the South China Sea using hydraulic fracturing: A numerical simulation

“…In addition, these issues may not be concerns because hydrates are a self‐preserving material . As long as hydrates are under stable thermodynamic conditions, the transient endothermic dissociation of hydrates into gas will be halted . Therefore, fracturing hydrate reservoirs before gas production by depressurization may be feasible and provide an alternative approach to extract gas more effectively.…”

“…If artificial fractures can be created in gas hydrate-bearing sediments (GHBS), the surface contact area between the pores and solid hydrates will increase to accelerate the dissociation, and these fractures can provide pathways for the water and gas to enter into the wellbore. [38][39][40][41] It is well known that hydraulic fracturing technology is widely used in natural oil and gas reservoirs to stimulate production. 42 Therefore, using this method to assist the gas production from GHBS by depressurization may present an exciting opportunity.…”

“…Based on previous investigations of hydrate dissociation, the gas recovery is mainly governed by the dissociation contact area. If artificial fractures can be created in gas hydrate‐bearing sediments (GHBS), the surface contact area between the pores and solid hydrates will increase to accelerate the dissociation, and these fractures can provide pathways for the water and gas to enter into the wellbore . It is well known that hydraulic fracturing technology is widely used in natural oil and gas reservoirs to stimulate production .…”

“…They have found that hydraulic fracturing is a promising well stimulation method for low‐permeable gas hydrate reservoirs. The detailed status of fracturing methane hydrates in sands can be found in the review concluded by Too et al . Additionally, Chen et al have preliminarily reported the effect of fracturing technology on the production efficiency of natural gas hydrates by numerical simulation combined with vertical well design and fluid jet technology based on field data.…”