FROZEN HEAT | Volume 2

3.2 ESTABLISHING SAFE SITE CONDITIONS

Over the past several decades, industry and regulators have es- tablished procedures for evaluating site safety with regard to locating conventional oil and gas exploration and production facilities. Once a promising location has been confirmed, sur- veys and evaluations are conducted to determine the geology, geohazards, drilling hazards, and environmental conditions (Graber 2002; Kvalstad 2007; NGI 2005). Surficial surveys (primarily shallow geophysics and coring) are used to charac- terize the geology of shallow sediments and to determine their geotechnical properties. A geohazard assessment is under- taken to document active geologic processes (seabed erosion, deposition, slope instability, and unique ecological habitats), to quantify the seismic risk, and to consider the potential occur- rence of shallow gas, shallow water flows, or other anomalous subsurface conditions. In deepwater marine settings (at wa- ter depths greater than 250 metres), the possible occurrence

of shallow gas hydrates or seafloor outcrops of gas hydrates should be routinely evaluated, as they can become unstable when disturbed (Hovland and Gudmestad 2001; Peters et al. 2008; McConnell et al. , 2012) or might be associated with unique biological habitats (MacDonald et al. 1994). Normal practice has been to avoid locating wells where shal- low gas hydrate outcrops occur and to drill and case any shal- low hydrate intervals as quickly as possible. The challenge in establishing production from a gas hydrate field is that the gas hydrate interval itself cannot be avoided, as it is the target. Quantifying the geomechanical response of the gas hydrate-bearing strata during methane production will be an important consideration in establishing safe site conditions for gas hydrate production facilities (Kleinberg and Jones 2004; Yamamoto 2008; Rutqvist and Moridis 2009).

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