Oil & Gas - Maximising Recovery Programme (formerly SHARP) IOR Views

Background

Britain has made firm commitments to reduce CO2 emissions to the atmosphere going even beyond its Kyoto protocol commitments. The rapidly increasing emissions of so called "Greenhouse" gases, which include CO2, are blamed for global warming. There are a number of initiatives underway at DTI to evaluate the capture and storage of the CO2 that is generated during industrial processes such as power generation using fossil fuels (so called anthropogenic CO2). This work is undertaken by the Clean Fossil Fuels Unit. One way of storing CO2 is in underground geological formations. These formations need to have a suitable structural or stratigraphic trap to hold the CO2 in place. Consequently, depleted oil and gas reservoirs may be suitable for the long term storage of CO2.

With oil reservoirs, there is also the potential benefit of increasing the amount of oil recovered. CO2 has the potential displace oil down to very low residual saturations. Such practice is very common and routine in onshore operations for example in the Weyburn oilfield in Canada. There is also an interesting project being proposed by an industrial consortium - the CENS project. This would provide an infrastructure which can collect CO2 from power generation and other sources in the countries around the periphery of the North Sea and deliver it to the various oil fields (see http://ior.rml.co.uk/issue7/articles/kindermorgan/ and http://ior.rml.co.uk/issue4/co2/inco2/summary.htm).

In a recent consultation exercise by the DTI, North Sea operators indicated that from a reservoir displacement point of view they understood the benefits of CO2 injection. However, one of the issues raised by operators was the cost and practicality of converting offshore wells and topside facilities for use with CO2 injection.

Presenters and Attendees

The workshop was planned and presented by John M Campbell & Company. The DTI is grateful to the presenters John Morgan, President, John M. Campbell & Company and Wes Wright, Staff Operations Engineer, Weyburn CO2 project, EnCana. There was a dinner at the end of the first day with David Coleman of Kinder Morgan talking about the CENS Project (North Sea CO2 Infrastructure Proposal) - see links above.

Workshop Presenters: John Morgan, President, John M. Campbell & Company (Right) and Wes Wright, Staff Operations Engineer, Weyburn CO2 project, EnCana (Right)

36 delegates attended; 12 of these were from major operating oil companies (ExxonMobil, Shell, BP, ConocoPhillips, Total, Talisman, CNR, EnCana, Apache), 14 from the service/consultancy company sector, 4 from universities and 6 from governmental bodies (including 2 from the Norwegian Petroleum Directorate).

The workshop was highly interactive with all delegates playing their part in discussing and weighing the issues. Syndicate sessions were held after the presentation of each main topic, and these syndicates reported back their findings. These finding were then compiled into a note which was later provided to each delegate. The full note can be downloaded from http://www.dti-sharp.co.uk/dissemination/co2/Note%20DTI%20CO2%20Workshop.pdf. A distillation of the workshop findings is presented below.

Distillation of Workshop Findings

The overall findings from the workshop (based on the feedback received) were:

• Converting offshore wells and facilities for use with CO2 flooding would be a major undertaking. The most economical development may be nearer to a green field development (with many new facilities required) than a brown field redevelopment.
• Although there are synergies with North American experience, there are many differences. For example; mainly sandstone reservoirs rather than carbonate, higher pressures and temperatures, and more capitally intensive cost environment (North Sea is high Capex relatively low Opex whereas the opposite is true in the onshore environment in North America ).
• There are areas where technological development would be beneficial - for example gas separation and dehydration technology, and in compressor technology (to deal with variable gas composition).
• The North Sea would benefit from an integrated development plan - this should cover the source and distribution of the CO2, as well as issues related to the timing and quantities of CO2 required at each converted/redeveloped field.
• Many North Sea fields have benefited from a high level of secondary recovery from water flooding - in general this augurs well for successful implementation of CO2 flooding; the amount and timing of incremental recovery is uncertain but for miscible displacement should be in the range 5-15% of oil initially-in-place with an expectation that the amount would be around 7% OIIP.
• The number of wells in a given field is limited and most likely not optimally aligned (sweep arrangement gravity stable or pattern flood?) Because of the shortage of slots, new wells would have to be sub-sea. A number of producers already use appropriate subsurface metallurgy (+13 Cr). Injectors would need to be redesigned. There is perhaps a piece of work looking at in-well, wellhead and tree design relevant to North Sea CO2 projects. All elastomer components would need to be consistent with high CO2 concentrations.
• Weight and space considerations together with the fuel and power issues are paramount in relation to topsides. Corrosion is a major issue; how much equipment can be refurbished, how much it would be more economical to replace. Separation of CO2/hydrocarbon gas from the produced stream is required (prior to reinjecting the CO2 - the presence of methane hurts miscibility but traces of ethane and above aid miscibility). Dehydration of produced CO2 is probably needed at North Sea conditions (because of lower temperatures). H2S would need to be treated and disposed.
• Compression of CO2 is a major issue. Pure CO2 can be pumped, but produced gas streams with varying proportions of CO2 and hydrocarbon gas will require reciprocating, screw or variable-speed centrifugal compressors.
• There are a range of production chemistry issues to consider: water pH, mineral scale, freezing, hydrates, emulsions, asphaltenes, wax, sand production (severe erosion of tubing etc.).
• Offshore safety procedures would need upgrading. CO2 is an asphyxiate. Because it is denser than air, evacuation procedures, and venting and flaring issues would need to be reviewed. As CO2 expands more than hydrocarbon gas over the same temperature range, it is important that it is not trapped or depressurised too quickly.
• Considerable uncertainty in the fiscal regime that would apply - EOR vs. CO2 storage. What subsidies would be available and what the situation would be post-2012 where there is no current legislative regime. Always the unknown of the oil price.

David Coleman of Kinder Morgan Discussing the CENS Project at the Workshop Dinner

Next Step

The DTI does not underestimate the scale of the issues involved in taking forward the issue of CO2 injection in UKCS fields.

Having established some momentum at the workshop, the DTI will consider the appropriate next step once the report on the consultation exercise "A Carbon Abatement Technology (CAT) Strategy for Fossil Fuel Power Generation" has been published early in 2005.