Techniques in the upstream oil and gas industry

1. A method for enhancing offshore oil recovery using carbon dioxide (CO 2 ) or for enhancing offshore gas recovery using CO 2 comprising the steps of:

delivering CO 2 in a liquid state or a super-critical state by at least one carrier vessel from at least one CO 2 storage site to an offshore facility provided with at least one on-site storage unit, selected from subsea tanks or internal tanks within a hull or other floating structure of the offshore facility, and with marine transfer equipment configured to transfer CO 2 in said state from the carrier vessel to the on-site storage unit;

storing the CO 2 in said state in the on-site storage unit; and

utilizing the CO 2 from said at least one on-site storage unit for enhanced oil recovery at said offshore site or for enhanced gas recovery at said offshore site both at times when a said carrier vessel is present at said offshore facility and at times when no carrier vessel is present at said offshore facility by injecting the CO 2 into a sub-sea oil or natural gas bearing reservoir and recovering oil and/or natural gas from a resulting production stream;

wherein at least a portion of the CO 2 delivered to said facility by said at least one carrier vessel comprises CO 2 from a production stream at a second offshore facility wherein said CO 2 is stored at the second offshore facility in the liquid or super-critical state and transferred at the second offshore facility to said at least one carrier vessel.

2. A method according to claim 1 , wherein said at least one on-site storage unit comprises a separate floating storage and offloading hulled vessel without oil or natural gas production facilities that comprises said internal storage tanks.

3. A method according to claim 1 , wherein said at least one on-site storage unit comprises a separate hulled vessel that is provided with:

said internal storage tanks;

first plant and equipment configured to process CO 2 -laden hydrocarbon production streams, separate CO 2 from production fluids, and process and apply the necessary pressure and temperature regulation to CO 2 so that it reaches the said state; and

second plant and equipment to achieve the requisite CO 2 pressure and temperature for injection into the a sub-sea oil field or a sub-sea natural gas field;

whereby the said separate hulled vessel is configured to be supplied for enhanced recovery of oil using CO 2 or for enhanced recovery of gas using CO 2 at an offshore facility not otherwise equipped for enhanced recovery of oil or gas using CO 2 , and is adapted to be towed away from said facility when no longer required thereat for use at a different offshore facility.

4. A method according to claim 1 , wherein the offshore facility further comprises separation equipment configured for separating CO 2 from the production stream for direct re-injection or for storage in the at least one on-site storage unit.

5. A method according to claim 1 , wherein the at least one CO 2 storage site comprises at least one onshore site to which CO 2 is delivered by at least one of pipeline, road and rail from at least one facility in which CO 2 is produced as a waste product; and wherein the CO 2 is liquefied or rendered supercritical at one of the said facility and the onshore site.

6. A method for producing oil and or gas at an offshore facility, comprising the steps of:

separating CO 2 at said offshore facility from a production stream at said offshore facility,

storing said CO 2 in a liquid or supercritical state in at least one on-site storage unit, selected from subsea tanks or internal tanks within a hull or other floating structure of the offshore facility,

transferring CO 2 in said liquid or supercritical state from the at least one on-site storage unit to a carrier vessel using marine transfer equipment provided at the offshore facility, and

delivering the transferred CO 2 to a second facility using the carrier vessel for use in enhancing offshore oil recovery using CO 2 or for enhancing offshore gas recovery using CO 2 at the second facility.

7. An offshore oil or natural gas facility provided with:

at least one on-site storage unit, selected from subsea tanks or internal tanks within a hull or other floating structure of the offshore oil or natural gas facility, adapted to store CO 2 in a liquid or a super-critical state;

marine transfer equipment configured to transfer CO 2 in said state from said at least one on-site storage unit to a carrier vessel;

recovery equipment configured to recover oil and/or natural gas from a hydrocarbon production stream;

first plant and equipment which has the capability to process CO 2 -laden hydrocarbon production streams, separate CO 2 from production fluids, and to process and apply the necessary pressure and temperature regulation to the separated CO 2 so that it reaches said state; and

second plant and equipment coupled to the first plant and equipment and to the at least one on-site storage unit, to store the separated CO 2 in said at least one on-site storage unit.