gas hydrate - CCOP

THE STRATEGY FOR OFFSHORE NATURAL GAS HYDRATE PRODUCTION
Production challenges
Most of offshore hydrates are located in the sediments under sea level at water depths ranging
from 300 m to 3,000 m. Some of these are located in unconsolidated silt. Exploration and
production are both difficult processes. The main challenges will have to be met in order to
exploit the natural gas hydrate are as follows:
1) Natural gas hydrate exploration and production technology: The natural gas hydrate
production process is closely related to the land and seabed stability and may affect
the global environment. Appraisal well drilling, completion, well control and dynamic
monitoring of production are all great challenges which need to be met and overcome.
2) Environment protection issue: As methane is an important greenhouse gas, it will be
imperative to protect the environment from pollution during the hydrate exploration
and production process.
3) Engineering safety: Hydrate dissociation will affect the stability of structures both up
and down the mud line, which is the one of biggest challenges that the deepwater
engineers must overcome.
The conceptual development method for offshore natural gas hydrates
Considering the storage features of the hydrate reservoir, shallow or very shallow kind of
resource, as that of shallow gases, the overall strategy for hydrate production suggested here
is to drill shallow horizontal wells and use combined hydrate production methods, including
the depressurization, thermal stimulation, chemical injection and other new kinds of methods
(see Figure 5).
The basic principle is as follows:
1) First stage: develop the free gases under the hydrate layer at first, then with the
progress of the production, the pressure of free gases decrease with the hydrate layer
pressure decrease , the natural gas hydrate begin to dissociate with the decreasing of
the reservoir pressure, the whole development process is slow natural de
depressurization;
2) Second stage: accelerate the hydrate dissociation to obtain effective development. This
time the heat stimulation and chemical injection methods are to be used, heat flux or
chemical substance is injected into the hydrate reservoir through the well to stimulate
the hydrate dissociation;
3) Drill the shallow horizontal well to enhance the gas recovery.
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New Energy Resources in the CCOP Region - Gas Hydrates and Coalbed Methane