Experimental Observations of the Effect of MICP on the Deformation Mechanisms of a Layered Formation during Sand Production

Significant gas hydrate resources are located offshore in the upper sedimentary layers. At present, depressurization has yielded the highest extraction rates, although sand production has been the major ongoing challenge, terminating two of the three depressurization trials to date. In this context, microbial-induced calcium carbonate (CaCO3) precipitation (MICP) could be used to enhance soil resistance and hence reduce sand production. Here, a plane-strain sand production apparatus that incorporates particle image velocimetry (PIV) is used to examine the sand production deformation mechanisms and failures of a layered granular system treated with MICP using different bacterial strains. The different mineral phases precipitated by different bacterial strains are shown, and the importance of CaCO3 mineralogy is highlighted. PIV analyses show, for the first time, that the mechanical behavior of the formation sand is sensitive to the CaCO3 mineral phase formed, resulting in changes in failure patterns. Understanding these failure patterns potentially allows for savings to be made in sand management methods.