Tidal Current Energy

324 D. Tondeur and F. Teng
3.3 .
Table 18.5 . CO 2 EOR projects worldwide.
Country Total projects Ongoing projects
USA
85 67
Canada 8
2
Hungary 3
0
Turkey 2
1
Trinidad 5
5
Brazil
1
1
China
1
0
Total 105 76
( Source : IEA [20] )
CO 2 enhanced oil and gas recovery (CO 2 EOR and CO 2 EGR)
Oil and gas fields are depleted because the pressure within the hydrocarbon formation
drops when the oil or gas is produced until the pressure is no longer
sufficient to drive fluid towards the wellbore. The injection of CO 2 into these
depleted formations can repressurize the formation. When CO 2 is injected
into an oil field, it also can mix with oil, reduce its viscosity and help the oil
flow more easily to the production well. The combination of these effects will
increase oil and gas production; this is the so-called CO 2 enhanced oil recovery
(CO 2 EOR) or CO 2 enhanced gas recovery (CO 2 EGR). In EOR or EGR, not all the
injected CO 2 remains in the oil and gas fields; part of the CO 2 will be extracted
from the produced oil and recycled, while part of it will be ‘ fixed ’ in the oil and
gas reservoir. For CO 2 EOR, up to half of the CO 2 will be stored in the reservoir
after production, while the rest will be separated and reused.
CO 2 EOR is a commercially proven technology which is already widely used
in the USA and other countries ( Table 18.5 ).
Worldwide, the potential for CO 2 EOR is limited. One reason is that CO 2 EOR is
restricted to oil fields with an API gravity between 27 and 48, equivalent to a density
between 788 and 893 kg�m � 3 , which makes this method unsuitable for heavy
oil [21] . Another reason is the uneven distribution of oil fields around the world,
and suitable point sources for CO 2 capture may be far away from the oil fields.
Moreover, CO 2 EOR has to compete with other EOR technologies like water flooding
or polymer flooding. CO 2 EOR can substantially improve the oil production
(8–15% of the total quantity of original oil in place, based on US experience).
The Weyburn CO 2 EOR project is located in Williston Basin, Saskatchewan,
Canada. The aim of this project is to assess the technical and economic feasibility
of CO 2 storage in oil reservoirs. The field covers an area of 180 km 2 with
an average crude oil production of 2900 m 3� d � 1 . The injection of CO 2 began in
2000 with a rate of 5000 t� d � 1 (about 2.69 � 10 6 m 3� d � 1 ). The CO 2 comes from
a synthetic gas facility located in North Dakota, USA, through a 325-km pipeline.
The Weyburn CO 2 EOR project is designed to accumulate CO 2 for about