Summary
Although significant hydrate deposits are known to exist in the Ulleung
basin of the Korean East Sea, their survey and evaluation as a possible energy
resource has not yet been completed. However, it is possible to develop
preliminary estimates of their production potential based on the limited data
that are currently available. These include the elevation and thickness of the
hydrate-bearing layer (HBL), the water depth, and the water temperature at the
seafloor. On the basis of this information, we developed estimates of the local
geothermal gradient that bracket its true value. Reasonable estimates of the
initial pressure distribution in the HBL can be obtained because it follows
closely the hydrostatic. Other critical information needs include the hydrate
saturation, and the intrinsic permeabilities of the system formations. These
are treated as variables, and sensitivity analysis provides an estimate of
their effect on production.
On the basis of the geology of similar deposits, it is unlikely that Ulleung
basin accumulations belong to Class 1 (involving a HBL underlain by a mobile
gas zone). If Class 4 (disperse, low-saturation accumulations) deposits are
involved, they are not likely to have production potential. The most likely
scenarios include Class 2 (HBL underlain by a zone of mobile water) or Class 3
(involving only an HBL) accumulations.
Assuming nearly impermeable confining boundaries, this numerical study
indicates that large production rates (several MMscf/D) are attainable from
both Class 2 and Class 3 deposits using conventional technology. The
sensitivity analysis demonstrates the dependence of production on the well
design, the production rate, the intrinsic permeability of the HBL, the initial
pressure, temperature, and hydrate saturation, as well as on the thickness of
the water zone (Class 2). The study also demonstrates that the presence of
confining boundaries is indispensable for the commercially viable production of
gas from these deposits.
© 2009. Society of Petroleum Engineers
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History
- Original manuscript received:
3 September 2007
- Meeting paper published:
30 October 2007
- Revised manuscript received:
2 July 2008
- Manuscript approved:
27 July 2008
- Published online:
23 July 2009
- Version of record:
22 December 2009
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