Page 227 - Handbook Of Multiphase Flow Assurance

226 10. Research methods in flow assurance

CO 2 tanker

more than CO discharge pipe
3000 m. 2

FIG. 10.3 Conceptual view of CO 2 disposal at ocean bottom.

Hydrates as a source of hydrocarbon fuel

Hydrates of natural gas are widely spread around the globe. The techniques of gas ex-
traction from hydrate already exist (Makogon, 1981) and are being improved. Locations of
hydrates are found in all continents in the world. It can be seen that hydrates are often en-
countered in offshore regions as well as onshore.
Gas hydrates store a tremendous amount of gas. Over 170 volumes of gas at standard tem-
perature and pressure may be enclathrated by water. Fig. 10.4 demonstrates that the amount
of gas in gas hydrate is sufficient to support its own combustion while melting the hydrate
crystal. Natural gas hydrates are a potential source of fuel for the future.
One of the most recent illustrations of the influence of natural hydrates on the environ-
ment may be viewed in the several unexplained vertical near-cylindrical caverns or craters of
approx. 100 ft in size which have suddenly appeared in area of northern Russia called Yamal
(Fig. 10.5). Makogon and Makogon (in Riazi 2016, p.429) hypothesize that this may have
been brought about by warming of the upper lithological permafrost cover thus destabilizing
gas hydrate deposit trapped under the icy permafrost cover, which is impermeable to gas.
As permafrost temperature remained below ice freezing but above hydrate stability, gas re-
leased from a hydrate lens deposit accumulated under the permafrost cover. Pressure of the
gas released from hydrate built up until it equaled the geostatic overburden pressure of the
permafrost cap still frozen and impermeable and led to a pneumatic explosion. Gas would
escape to the atmosphere and the soil and still stable ice from permafrost would form edges of
crater or fall to the bottom of the crater. The lower estimate of the amount of gas released from
hydrate may be easily calculated from measuring the depth and diameter of the vertical near-
cylindrical crater by equating the pressure exerted by overburden permafrost soil column