336
Water for Energy and Fuel Production
hydrate undergoes phase transition, the release of water and methane can occur at
very high rates. The rapid release of methane gas in a closed system can result in a
rapid increase in pressure [104,105], which can be harmful to the drilling operation.
In recent years, hydrate formation during drilling operation is controlled with the
use of kinetic hydrate inhibitors [96–99,113–116], which dramatically slow the rate
of hydrate formation and anti-agglomerates, which prevent hydrates from sticking
together to block pipes and other parts of equipment.
When drilling in oil- and gas-bearing formations submerged in deep water
[55–59,84,85], the reservoir gas may flow into the well bore and form gas hydrates
owing to the low-temperature and high-pressure conditions found during deep-water
drilling. The gas hydrates may then flow upward with drilling mud or other discharged fluids. As they rise, the pressure in the annulus decreases and the hydrates
dissociate into gas and water. The rapid gas expansion ejects fluid from the well,
reducing the pressure further, which leads to more hydrate dissociation and further fluid ejection. The resulting violent expulsion of fluid from the annulus is one
potential cause or contributor to what is referred to as a “kick” [104,105], which can
cause blowouts. This can cause serious well safety and control problems and create
hazardous conditions such as flow blockage, hindrance to drill string movement,
loss of circulation, and even abandonment of the well. Since gas hydrates contain
85% water, their formation can withdraw water from drilling fluids, changing the
properties of the fluids, thus causing salt precipitation, an increase in fluid weight,
or the formation of solid plug.
The condition of the hydrate formation during kick depends on the composition
of the kick gas, temperature, and pressure. A combination of salts and chemical
inhibitors can provide a required inhibition to avoid hydrate formation, particularly
at water depths >1000 m [96–99,115–116].
12.3.2 ProduCTion By enhAnCed oil And gAS reCovery meThodS
Enhanced oil and gas recovery methods increase the risk of the gas hydrate formation. Process equipment and multiphase transfer lines from wellhead to the production platform where low-temperature and high-pressure conditions exist are prone to
hydrate formation. The following methods are generally adopted to reduce hydrate
problems in hydrocarbon transfer lines and process facilities [86–93]:
1. Use high flow rates, which limit the time for hydrate formation in a volume of fluid, thereby reducing the kick potential [104,105]. Make careful
measurement of line flow to detect incipient hydrate plugging [104,105],
particularly at low gas production rate. Also, monitor the pressure rise
in wellcasing after it is “shut in” (isolated). The hydrate formation will
decrease the rate of pressure rise [104,105].
2. Additions of energy (e.g., the energy released by setting cement used in well
completion) can raise the temperature and convert hydrates to gas, producing a “kick.”
3. For a given pressure, operate at temperatures higher than the hydrate
formation temperature. This can be done by insulation or heating of
Water for Energy and Fuel Production
hydrate undergoes phase transition, the release of water and methane can occur at
very high rates. The rapid release of methane gas in a closed system can result in a
rapid increase in pressure [104,105], which can be harmful to the drilling operation.
In recent years, hydrate formation during drilling operation is controlled with the
use of kinetic hydrate inhibitors [96–99,113–116], which dramatically slow the rate
of hydrate formation and anti-agglomerates, which prevent hydrates from sticking
together to block pipes and other parts of equipment.
When drilling in oil- and gas-bearing formations submerged in deep water
[55–59,84,85], the reservoir gas may flow into the well bore and form gas hydrates
owing to the low-temperature and high-pressure conditions found during deep-water
drilling. The gas hydrates may then flow upward with drilling mud or other discharged fluids. As they rise, the pressure in the annulus decreases and the hydrates
dissociate into gas and water. The rapid gas expansion ejects fluid from the well,
reducing the pressure further, which leads to more hydrate dissociation and further fluid ejection. The resulting violent expulsion of fluid from the annulus is one
potential cause or contributor to what is referred to as a “kick” [104,105], which can
cause blowouts. This can cause serious well safety and control problems and create
hazardous conditions such as flow blockage, hindrance to drill string movement,
loss of circulation, and even abandonment of the well. Since gas hydrates contain
85% water, their formation can withdraw water from drilling fluids, changing the
properties of the fluids, thus causing salt precipitation, an increase in fluid weight,
or the formation of solid plug.
The condition of the hydrate formation during kick depends on the composition
of the kick gas, temperature, and pressure. A combination of salts and chemical
inhibitors can provide a required inhibition to avoid hydrate formation, particularly
at water depths >1000 m [96–99,115–116].
12.3.2 ProduCTion By enhAnCed oil And gAS reCovery meThodS
Enhanced oil and gas recovery methods increase the risk of the gas hydrate formation. Process equipment and multiphase transfer lines from wellhead to the production platform where low-temperature and high-pressure conditions exist are prone to
hydrate formation. The following methods are generally adopted to reduce hydrate
problems in hydrocarbon transfer lines and process facilities [86–93]:
1. Use high flow rates, which limit the time for hydrate formation in a volume of fluid, thereby reducing the kick potential [104,105]. Make careful
measurement of line flow to detect incipient hydrate plugging [104,105],
particularly at low gas production rate. Also, monitor the pressure rise
in wellcasing after it is “shut in” (isolated). The hydrate formation will
decrease the rate of pressure rise [104,105].
2. Additions of energy (e.g., the energy released by setting cement used in well
completion) can raise the temperature and convert hydrates to gas, producing a “kick.”
3. For a given pressure, operate at temperatures higher than the hydrate
formation temperature. This can be done by insulation or heating of