Abstract: Closure Behaviour of Natural Rock Fractures

DUAN, YUTING, Imperial College

In order to investigate the closure behaviour of natural rock fractures, a surface measurement system called photoelectric surfometer has been developed. It can measure automatically the topography of rock surfaces, and is especially effective on natural rock surfaces which have large heaves compared with polished rock surfaces as widely used in previous publications. An investigation into three-dimensional topography of surfaces of natural fractures was thereby carried out. On the basis of surface topography, computer simulation is then applied to mimic the closure behaviour of natural rock fractures under stress by utilising both elastic and plastoelastic contact theory between two rough surfaces. Experimental results confirmed the computer simulation. An empirical model based on the measurement and simulation results is then obtained, which includes rock properties, initial aperture and surface topographies. This model, being different from any other models proposed in previous publications, can be used to explain the different fracture characteristics found both in laboratory experiments and in situ reservoir formations. It predicts fracture aperture, and hydraulic conductivity of natural fractures both in laboratory and in-situ reservoirs.

AAPG Search and Discovery Article #90911©2000 AAPG Pacific Section and Western Region Society of Petroleum Engineers, Long Beach, California