Energy Technologies: How They Work and Their Induced Seismicity Potential - Induced Seismicity Potential in Energy Technologies - page 77

Sleipner

0 0.1 0.2 0.3 0.4

Porosity

Figure 2 Comparison of porosity and permeability for the CO 2 reservoirs in each of the three projects. The Utsira
Formation in the Sleipner field has an unusually high porosity and permeability. SOURCE: Eiken et al. (2011). 3- Classification: Internal 2011-08-18

The Snøhvit field offshore northern Norway is a natural gas field with an onshore liquid natural gas (LNG)
facility. Carbon dioxide separated during the LNG process was captured at the plant and piped back to the
field, where it was reinjected underground into a sandstone formation ~2,600 m (8,560 feet) below the seafloor
and below the main natural gas reservoir for the gas field; the entire offshore facility is subsea and operated
remotely from shore (Statoil, 2009). Carbon storage began in 2008, and CO 2 injection for storage was changed
from the Tubåen Formation to the gas-producing Stø Formation in March 2011. Monitoring throughout the
injection phase revealed increases in reservoir pressure beyond what had been initially anticipated, indicating
that the reservoir had a lower capacity to inject or store CO 2 than had been calculated at the start of the project
(Helgesen, 2010). Total stored CO 2 through March 2011 was about 1.1 megatons (Eiken and Ringrose, 2011).
At the In Salah field at Krechba onshore Algeria, the operators began injecting CO 2 in 2004 into a formation
located at intermediate depths between Sleipner and Snøhvit. By early 2011, nearly 4 million tons (3.6 million
metric tonnes) of CO 2 had been injected. The field has five gas production wells and three CO 2 injection wells.
The CO 2 for injection derives from both the produced gas at the field and from gas produced at other fields that
is piped to the injection well (Eiken and Ringrose, 2011).
The injection histories for all three fields are shown in Figure 3. The injection at Sleipner was very smooth
over 15 years with good injectivity and no evidence of pressure buildup. Very consistent injection pressures were
maintained at about 64-65 bars over the course of the project. The conditions at the other two fields proved
to be more challenging, with measured pressure increases and limitations on the total capacity of the storage

Box continues