QCCSRC Research and Development

From Sandstone to Carbonate Reservoirs

More than half of the world's conventional oil resources are contained in carbonate reservoirs that are typically extensively fractured. Many of these are in the Middle East and recovery factors are often low: while the fracture network carries most of the flow, the matrix retains the vast majority of original oil in place. However, these reservoirs are much more poorly understood than the clastic (sandstone) reservoirs found, for example, in Europe and the Americas.

An essential precursor to optimizing oil and gas recovery from these carbonate reservoirs, or using them to store carbon dioxide (CO₂) to mitigate catastrophic climate change, is the understanding of their evolution combined with appropriate and detailed characterization of the reservoir and the in situ fluids. This can be used in conjunction with reservoir simulators to optimize production and recovery factors or to design CO₂ injection processes to ensure safe and effective long-term storage.

Characterization procedures, simulators and EOR processes have been much studied and applied to good effect for sandstone reservoirs over several decades, but their development is much less refined for carbonate reservoirs, where the structures and physical chemistry are quite different. Enhancing this capability and applying it to Qatar's oil and gas fields is at the heart of QCCSRC's activities.

Reducing CO₂ release

Another key issue to be addressed as we move towards cleaner production and use of oil and gas is the need to prevent release of CO₂ produced by power generation and hydrocarbon processing. CCS involves collecting CO₂ from industrial sources and injecting it underground into depleted reservoirs or saline aquifers. It is an essential technology for reducing CO₂ emissions to the atmosphere and hence to mitigate climate change. At Imperial College there is the largest CCS research programme in the UK, based within IC⁴S.

The principal concern with CCS is to ensure that the injected CO₂ does not subsequently leak back into the oceans or atmosphere. Again, most studies to date have involved sandstone reservoirs. Exploring the feasibility of using Qatar carbonate reservoirs and aquifers for carbon sequestration, based on the same characterization and reservoir modelling approaches developed to optimize oil and gas recovery, is another critical element of QCCSRC.

Optimising CCS and EOR

New procedures for optimizing CCS and EOR in fractured carbonate reservoirs and integrating them into field practice are important elements of QCCSRC's programme. They build on the Energy Future Lab's existing Clean Fossil Fuels Grand Challenge programme in collaboration with Shell on CO₂ properties and sandstone reservoir injection and storage processes. This programme involves the fundamental study of the thermophysical and multiphase flow properties of CO₂/brine/hydrocarbon mixtures, in the context of enhanced oil and gas recovery and CO₂ storage applications. QCCSRC aims to harness this research to address specific issues with Qatar's gas and oil fields, including carbon storage, enhanced hydrocarbon recovery and their possible combination.

QCCSRC incorporates Imperial's petroleum and chemical engineering expertise, from a number of different research groups and networks within two Departments in particular:

• The Department of Earth Science and Engineering focuses on describing petroleum reservoirs from the core scale upwards, traditionally for the sandstone reservoirs prevalent in the North Sea. QCCSRC is expanding this expertise to encompass carbonate fields, by applying Imperial's experience from other places to situations of specific interest in Qatar.

•  The Department of Chemical Engineering has world-class research expertise in CO₂ reservoir processes: measurement and prediction of the properties of complex fluid mixtures including reservoir fluids; process and molecular systems engineering; multiphase fluid mechanics; separation processes; and hydrocarbon processing. These are being applied, inter alia, to new carbon capture and intensified hydrocarbon conversion processes.