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FROZEN HEAT
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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).
3.2
ESTABLISHING SAFE
SITE CONDITIONS