Hydrodynamic and thermal modeling of the Site U1517 with the matching of BSR position

Summary In the east side of the North Island of New Zealand gas hydrates are revealed by the presence of a bottom-simulating reflector (BSR) on the seismic images. The position of BSR identifies the lower limit of gas hydrate filled porosity and relates the pressure and temperature for the corresponding depth. The objective of the present study is to construct the hydrodynamic model of a geothermal reservoir and validate this model using the measured position of BSR in the vicinity of the U1517 site. The precise shape of the BSR depends on pressure and temperature fields in the studied area. Temperature distribution is governed by thermal conduction in the sediments and affected by thermal convection associated with fluid flow in the porous rocks, and focused on fluid circulation in faults, which are expected to induce important modification of the temperature field. A transient hydrodynamic 2D numerical model was constructed to simulate the position of the BSR around Site U1517, allowing to get fluid and heat flux and pressure and temperature fields. Gas hydrate phase transition are also considered. Different scenarios were tested considering a realistic range of background lateral fluid flux, and dissolved methane concentration.