Particle vs. Laboratory modelling of In Situ compaction

Abstract

Physical (in particular mechanical) behaviour is altered because of the stress release occurring when a core sample is retrieved from the Earth. Numerical and experimental simulations have been performed in order to assess the main discrepancies between laboratory measured and virgin in situ rock mechanical behaviour, and in particular, the main characteristics of virgin compaction behaviour. In the laboratory, synthetic sandstones were cemented under stress, permitting virgin compaction as well as stress-released core compaction experiments. Numerically, a discrete particle model (PFC) was used to mimic closely the laboratory procedures. Cement bond breakage causes a transition from stiff to soft behaviour above a certain stress level during virgin compaction. Both techniques show that core compaction may exceed virgin compaction during initial loading.