Effect of Hydrate Saturation and Pore Pressure on the Safe Exploitation of Natural Gas Hydrate Resources

¹ Ningbo Institute of Dalian University of Technology, No.26 Yucai Road, Jiangbei District, Ningbo 315016, China
² School of Civil Engineering and Mechanics, Yanshan University, Qinhuangdao 066004, China
³ State Key Laboratory of Natural Gas Hydrates, Beijing 100028, China

^* Corresponding author’s email: shenshi_nbi@dlut.edu.cn

Abstract

A comprehensive study of the mechanical behaviors of hydrate-bearing sediments (HBSs) is the key to safely exploiting hydrate resources. The mechanical behaviors of HBSs are related to many variables, among which hydrate saturation (S_h) and pore pressure (PP) are vital factors. In addition, S_h and PP are related to the location of hydrates in the subsea layer, so it is of positive significance to investigate their comprehensive influence on the mechanical behavior of HBSs. In this work, a series of triaxial tests were conducted on the HBSs synthesized in the laboratory to explore the influence of S_h and PP on the mechanical properties of the HBSs. The results show that the strength of HBSs increases with increasing PP and S_h. With increased PP and S_h, the stress-strain behaviors will shift from strain-hardening to strain-softening. Moreover, under different S_h conditions, a critical PP point of strain-hardening and softening transition exists in numerical perspective. The critical PP point will develop towards low pressure with increased S_h.