ABSTRACT:

There is still an important gap understanding the geomechanical response of subsurface formations during production/recovery processes. Triaxial test are used to find the constitutive behavior of the formations. Performing non-conventional triaxial test such as reverse triaxial compression test might describe the actual behavior of the reservoir in a more accurate manner. In this work, drained triaxial compression and reverse triaxial compression tests are performed using samples taken from heavy oil formation. The specimens show a crucial difference at the plastic region; while the compression test exhibits strain hardening, the specimens under extensional triaxial behaved perfectly plastic on extension tests leading to a simpler constitutive model.

1. INTRODUCTION

Hydrocarbon reservoirs are subjected to different stress path during its productive life (Dusseault, 2011; Uribe-Patiño, Alzate-Espinosa, & Arbeláez- Londoño, 2017). Depending of the production/injection processes the rock can be subjected to a stress state where the horizontal stresses reduce (production) or increase (injection). Besides, according the redistribution of stress around the wellbore and the pressure profile, the vertical stress might change (Ikogoll, Sibai, Skoczylas, & Herny, 1989). The mechanical behavior of a reservoir depends on the level of effective confining stress (Skomedal, Jostad, & Hettema, 2002), of the reservoir temperature (Morales-Monsalve et al., 2018) and the stress path (Skomedal, Jostad, & Hettema, 2002). The aim of this work is to study the effect of the stress path on the mechanical behavior of unconsolidated samples that represents hydrocarbon reservoirs.

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