Abstract
The low permeability of clayey-silt hydrate reservoirs in the South China Sea affects the thermal and pressure conductivity of the reservoir, which is difficult to spread to the far end of the wellbore and achieve commercial gas production. In this respect, enhancing the permeability to assist depressurization is necessary. Hydraulic fracturing is a promising reservoir stimulation method for gas hydrate reservoirs. Up to now, majorities of research focus on the fracability of hydrate-bearing sandy sediments, but the studies rarely involved fracture propagation characteristics of clayey-silt sediments in the hydrate dissociation area. In this paper, three sets of hydraulic fracturing experiments under different confining pressure were carried out using the clayey-silt sediments in the Shenhu Area. Computed tomographic (CT) images indicated that clayey-silt sediments could be artificially fractured, and the fracturing fluid could induce tensile fractures and local shear fractures. A multimorphological fracture zone occurred near the borehole. Furthermore, the greater the confining pressure imposed, the greater the breakdown pressure was, and the microfracture arose more easily. The fractures at the top were generally wider than those at the bottom with the same confining pressure. The experimental results could reveal the fracture initiation and propagation mechanism of clayey-silt sediments and provide theoretical support for hydraulic fracture in the hydrate dissociation area.
Highlights
Natural gas hydrates are crystalline material formed by natural gas and water at high pressure and low temperature
The results provide theoretical support for the research on hydraulic fracturing in clayey-silt sediments of the hydrate dissociation area
The injection pressure rapidly increased for short injections to a peak and drop to a plateau, which indicates that hydraulic fractures and microfractures were induced
Summary
Natural gas hydrates are crystalline material formed by natural gas and water at high pressure and low temperature. Yu et al [20] adopted the special production strategies of aggressive depressurization and permeability improvement and conducted long-term numerical simulations to contrast the gas recovery enhancement with different production strategies. 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). This paper carried out hydraulic fracturing experiments to analyze the fracability of clayey-silt sediments in the hydrate dissociation area of the Shenhu Area under different confining pressure. The results provide theoretical support for the research on hydraulic fracturing in clayey-silt sediments of the hydrate dissociation area
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
