On the Necessity of Computer Modelling in Designing Flowthrough Experiments to Simulate Field Scale Processes

Craig H. Moore

It is often deemed desirable to conduct experiments whose aim is to reproduce the spatial and temporal distribution of the minerals, and their textures, that occur in field scale systems. This knowledge can lead to the understanding of processes and to insights that may prove useful.

Often, the field scale system is simply reduced to a length scale allowed by laboratory apparati with concomitant adjustment of the flow velocities or fluxes. This approach is unlikely to produce the desired results because, although some length (and time) scales have been scaled appropriately, some length and time scales associated with the mineral reaction rates have not.

Mineral reaction rates depend upon fluid composition, temperature (both of which one usually does not want to change), flow rates (already scaled), and grain size. Grain size is the parameter which can be changed in the laboratory. This does not allow using the unmodified natural rock or sediment as material for the experiment. There is no simple way to determine appropriate grain sizes.

Computer modelling, using a coupled flow/reaction simulator, can be used to provide this information. Two examples, one from steam injection into the Clearwater formation and one from the natural diagenesis of an immature sediment, illustrate the techniques that need to be used to design a successful experiment as well as the inherent limitations on doing so.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995