Development of new novel constitutive model for deep reservoir sandstone rock for sand production application

Sand production in oil or gas well can cause serious havoc leading to surface and downhole equipment erosion and induced unwanted cost to fix it. Thus, for the completion selection and optimisation, it requires a proper geomechanical analysis. During this process it is very important to use an appropriate failure constitutive model where it should be able to honour the onset failure of the geomaterial and the post failure as well. Currently most of existing failure criteria do not honour full spectrum of stress and strain evolution including post failure (softening). We developed a new elastoplastic constitutive model for weak geomaterial to fill the gap by using single equation to honour both hardening and softening of the geomaterial. Triaxial test has been conducted on rock sample under different confining pressure using a servo controller. The data from lab test has been used to develop the constitutive failure model followed by a validation using the Finite Element Method. Mohr Coulomb failure which is commonly used in the industry has been compared with the new constitutive model (known as ASA model). As the results the newly developed model was able to capture better the full elasto-plastic behaviour that includes softening or post failure of the geomaterial mechanical response compared to Mohr Coulomb criterion. This is quite critical for oil and gas applications, especially in the case of sand production. In conclusion, the new constitutive model was able to honour the full spectrum of nonlinear stress strain evolution using single equation and demonstrated superior compared to the commonly used failure criteria in the industry.