Geological Modelling

Computer simulation of flow through porous media, as used in oil recovery, groundwater production and waste disposal risk assessment requires geological models of the geometry and properties of the rocks in the subsurface. The properties that are interpolated by these models include the porosity and the permeability.

Much of the raw data for geological models comes from seismic surveys where sound is reflected from layers at depths of up to five miles or so. This leads to a collection of points, that mark the depth of a layer, augmented from actual depth measurements in wells. It is necessary to find a surface that interpolates these points and is discontinuous at any faults. The best interpolation methods involve solving partial differential equations.

The property interpolations require a grid of 3D cells to be built. Dividing complicated shapes in 3D into small pieces with a regular pattern is made possible by, again, solving partial differential equations. The basic principle is to mimic heat conduction in the volume of interest, where we heat one part of the surface of the volume of interest, cool another part, and prohibit heat flow through the remainder of the surface. The surfaces of constant temperature then divide the volume into two. These surfaces, in combination with other surfaces constructed in a similar way can be used to build the grid of cells. Another approach to grid generation uses an analogy with fluid flow such that the streamlines of the velocity field are used to construct the grid lines.

Modeling the geometry of natural structures is challenging. There are many unsolved problems, and the solutions to these have many practical applications.

People working in this area within OCIAM are

• Dr Chris Farmer

For detailed information see

• Information about a leading geological modeling application

• General information about grid generation