Modelling mechanical behaviour of limestone under reservoir conditions

Abstract

High porosity and low permeability limestone has presented pore collapse. As fluid is withdrawn from these reservoirs, the effective stresses acting on the rock increase. If the strength of the rock is overcome, pore collapse may occur, leading to irreversible compaction of porous media with permeability and porosity reduction. It impacts on fluid withdrawal. Most of reservoirs have been discovered in weak formations, which are susceptible to this phenomenon. This work presents a study on the mechanical behaviour of a porous limestone from a reservoir located in Campos Basin, offshore Brazil. An experimental program was undergone in order to define its elastic plastic behaviour. The tests reproduced the loading path conditions expected in a reservoir under production. Parameters of the cap model were fitted to these tests and numerical simulations were run. The numerical simulations presented a good agreement with the experimental tests.

High-pressure compaction modelling of calcite (CaCO3) powder compact

“…They obtained an R-value of 4. Coelho et al [28] reported an R-value of 6.3 for Limestone with a porosity of 20-30%. Using a triaxial press they found an R-value of 6.3.…”

Generic strength model for dry jointed rock masses

“…3. Mowar et al (1996), Brazilian limestone data are from Coelho et al (2006), Indiana limestone data are the same as in Lomov et al (2005).…”

“…As shown in Fig (Walsh, 1965) using two different Poisson ratios, the markers are the experimental data (Baud et al, 2000a;Mowar et al, 1996;Vajdova et al, 2004;Coelho et al, 2006). …”

Advanced discrete-continuum methods for dynamic loading of tunnels by ground shocks

“…The model captures effects of shear-enhanced compaction as it is shown in Fig.1.4 where uniaxial and hydrostatic compaction of sandstones of different porosity is compared with the model. Solnhofen limestone data are from [13], Cordoba Limestone data are from [14], Brazilian limestone data are from [15], Indiana limestone data are the same as in [16] The material model used in this study is thermodynamically consistent and applicable to shock wave loading regime. It was developed to be applied not only for small scale rock samples but also for isotropic rock masses under assumptions that the joints are randomly distributed and overall response remains isotropic.…”

“…The bulking shift, µ b , is proportional to the amount of bulking porosity,φ 2 , as 15) whereγ controls the rate of compaction of porosity produced by bulking. The bulking porosity,φ 2 , is a history variable describing extra porosity produced by dilatancy using the following equation:…”