Ocean Bottom Multi-Component Seismic System for Methane Hydrate Dissociation Monitoring

In Oil and Gas industry, OBC (Ocean Bottom Cable) has been used for monitoring offshore reservoirs. OBC typically consists of submarine cable with several seismic sensors with a short spacing. Time-lapse seismic survey with ·OBC is generally carried out for monitoring the reservoirs during oil or gas production. We apply this technique to the area exists methane hydrates at water depth of around 1000m. We developed a new OBC, named as `DSS' (Deep-sea Seismic System). The receiver of the DSS has the set of 3-components accelerometer unit and a hydrophone configuration that is applicable for multi-component seismic survey. A gas production test (flow test) in the 2nd offshore production test was implemented in Eastern Nankai Trough, off Japan. We carried out seismic survey three times using a DSS with seventy receivers to understand physical property change accompanying methane “hydrates dissociation by the gas production test. In 2016, we carried out the first seismic survey before flow test as a base line survey in the study area. We obtained the data after flow test in 2017, we call this as “2nd seismic survey”. We conducted a final survey, we call this as “3rd seismic survey”, and recovered the DSS in 2018. The quality of the data obtained was excellent without any system troubles. We will present the DSS advantages and report the results of the survey.