Published by the DTI Oil & Gas Directorate for the reservoir engineering and IOR community in the UK.
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Fractured Reservoirs Research Project

Gary D. Couples, from the Heriot-Watt Institute of Petroleum Engineering, outlines a new joint industry research project aimed at obtaining a new process-based understanding of the formation of structural discontinuities (fractures) and at building better models of fracture distributions for use in coupled geomechanical and flow simulation tools. (gary.couples@pet.hw.ac.uk)

A new, three-year project is planned to start in January 2003. This research will create a new process-based understanding of the formation of structural discontinuities (fractures) in reservoirs. This new understanding will allow us to build better models of fracture distributions, which will allow us to take full advantage of new, coupled, geomechanical and flow simulation tools. The work that we propose will employ new finite-element techniques - that are capable of achieving amazing realism - for simulating the creation of fractures in reservoirs. These simulations will be constrained by new outcrop-based studies involving both carbonate and clastic rocks. An important additional constraint will come from the database that we will create to relate fracture types and their properties. The practical application of the new work will be tested in a case study to be agreed with sponsors. We are seeking six sponsors at £35k per annum.

The justification for this project is our belief that developing an understanding of, and then the ability to effectively operate, structurally-complex, fractured reservoirs demands an appreciation of the processes that have been, and are, active within them. Recent developments mean that we can now develop such a process-based understanding of the geomechanical and fluid flow aspects of fractured reservoirs.

The project workplan has been formulated based on the following precursor points:

1. The majority of reservoirs are contained in layered rock sequences.
2. Each layer in a sequence will have its own mechanical properties, which means that, during deformation, quite different responses (for example, granulation seams and open fractures) can occur in adjacent layers.
   
3. Real deformations create layer-bounded "mechanical units" that initially include a significant number of individual rock layers, and which are subdivided as deformation progresses. Fractures (structural discontinuities) develop with a strong spatial and causal association with mechanical-unit boundaries (Figure 1).
   
   
   Figure 1. Fracture-layering relationships in a reservoir-scale flexure
   
   
4. New geomechanical approaches allow us to numerically simulate the development of fractures and faults in structures (Figure 2).
   
   
   Figure 2. Comparison of simulation, experiment, and outcrop for flexure case
   
   
5. Tools now exist, and will be further enhanced, which can simulate fluid flows in mechanically-active systems of matrix blocks + fractures (Figure 3).
   
   
   Figure 3. Flux "vectors" and pressure distributions for coupled, fluids and matrix+fractures models

For further information about this project, please contact:
Dr Gary D. Couples, Heriot-Watt Institute of Petroleum Engineering, Heriot-Watt University, Edinburgh EH14 4AS, Tel +44 (0)131 451 3123, Fax +44 (0)131 451 3127, gary.couples@pet.hw.ac.uk

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