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

Rigorous Upscaling of Flow Properties in Fractured Media

Approximately one half of the world's hydrocarbon reserves are contained in fractured reservoirs, with large deposits in the North Sea and the Middle East. However, typically 80 - 95% of the oil in place is left underground, since most of the oil is retained in relatively low permeability rock, while the flow is confined to the fractures. In nuclear waste containment, one key issue in considering long-term underground storage is how to predict the migration of radioactive species were they to escape. In both these cases there is flow of multiple fluid phases in fractured rock: oil, water and gas in oil reservoirs; and unsaturated flows in repositories. There is huge uncertainty associated with designing improved oil recovery schemes in fractured reservoirs and nuclear waste storage for two principal reasons: first the geological description of the fracture network is highly uncertain; and second the basic physical processes and their macroscopic description, particularly when they involve multiphase flow, are still not well established. This proposal will focus on the second of these issues. We will use analytical methods to derive expressions for how fluids move in simple fracture geometries for a variety of physical situations commonly encountered in fractured systems. These expressions will be validated against direct numerical simulation and available experimental data. The analytical expressions that describe fluid transport on the centimetre to metre scale will then be used in upscaled transport equations to describe flow at the field scale (on length scales of kilometres and time scales of decades to thousands of years). Where possible, analytical expressions will be derived and compared against direct numerical simulation. The end result will be a methodology to use small-scale measurements to describe fluid flow at large scales (upscaling) allowing complex multiphase flow processes in fractured reservoirs to be modelled with confidence using mathematically consistent and physically-motivated transport equations.

The Principal Investigator is Professor M J Blunt (m.blunt@imperial.ac.uk) of the Department of Earth Sciences at Imperial College, London.  This project started in September 2004 and will run until August 2007.  The award value is £180,500.

Error Models for Sub-Grid Phenomena in Flow in Porous Media

Quantifying uncertainty in predictions about fluid flow in complex systems is an area of increasing importance. Many fields of computational fluid dynamics have unresolved features which limit our ability to predict the behaviour of the system. Applications are found in areas as diverse as predicting oil recovery from reservoirs, weather forecasting, and certification of weapons systems performance. In most of these cases, we have observed or measured data for only some of the system parameters, and have to make inferences about other system parameters from running may simulations and comparing predictions with observations. The constraints placed on the parameters by the observed data can then be used to make predictions about uncertainty in future behaviour. The accuracy with which forecasts are made depends critically on how the computer models treat unresolved features in the flow. The goal of this research is to develop a theory for the effect of unresolved features on the accuracy of fluid flow simulations. The research will be targeted at flow in porous media initially, but is likely to be applicable across a wide range of computational fluid dynamics fields.

The Principal Investigator is Professor M Christie (Mike.Christie@pet.hw.ac.uk) of the Institute of Petroleum Engineering, Heriot-Watt University, Edinburgh.  This project started in January 2005 and will run until December 2007.  The award value is £237,900.

Skeletonisation, Entropic Characterisation and Conductivity-Permeability Relationship in Porous Media

The aim of this proposal is to exploit recent progress in the fields of granular and cellular systems for (1) the development of a new characterisation method of porous media and (2) the development of fundamental relations between the characteristics of the pore scale structure and macroscopic permeability and electrical conductivity. This will be achieved by first developing a skeletonisation method combined with a new fabric tensor that describes the local pore structure, and then using it to construct an entropic description of porous systems based on the Edwards formalism and the compactivity concept. This description will then be used to relate the structure to the permeability and conductivity on the pore scale. Finally, these relations will be coarse-grained to yield a macroscopic structure-property relationship. The method proposed here is uniquely suited to relate the conductivity and the flow permeability through their derivation from the same microstructural characterisation. It also makes it possible to understand from first principles the origin of the broad permeability distribution usually measured in many porous media. The project will involve a collaboration between Imperial College and Cambridge University and will be carried out in both institutes. Some of the outcomes of this work are will be relevant to multiphase flow and therefore of great interest to oil companies. Indeed, some industrial support has been secured. The project represents good value for money in that its successful completion will result in a major progress that will benefit several communities both in science and engineering.

The Principal Investigator is Professor P R King (peter.king@imperial.ac.uk) of the Department of Earth Sciences at Imperial College, London.  This project started in January 2005 and will run until January 2008.  The award value is £293,950.