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A porous shape memory polymer (SMP) product is currently deployed in oil and gas wells as a sand control system. This thermally and chemically activated polymer is emerging as a smart material due to its ability to recover to a predetermined shape following environmental manipulation, even after large wash out beyond gauge hole. The SMP is molded in a cylindrical geometry with desired inner and outer diameters for oil and gas production wells. This innovative technology has proven to be a reliable sand control media, a required step in combating sand production, protecting equipment and increasing the well lifetime [1, 2]. Material properties must be known in order to define the behavior of a SMP for evaluating its application in field application. The purpose of this paper is to establish a workflow in determining the material properties necessary to describe the behavior of SMP and study SMP integrity and performance under field conditions deployed in a wellbore during hydrocarbon production. For this purpose, a finite element model coupled with dynamic fluid lab data has been designed to estimate the material properties. Hyperelastic and viscoelastic constitutive models best describe the behavior of the SMP materials. The non-linear and non-elastic behaviors of the material makes the analytical solution approach inefficient, so a finite element modeling approach has been employed to overcome this difficulty. Several lab tests at different temperature conditions have been performed to expand the knowledge on material behavior. Results in this paper suggest the designed techniques and workflow are suitable in predicting material properties of SMP under any temperature conditions. Finally, a separate finite element analysis is formulated for assessment of geomechanical loads and deformations on the SMP. A 2D fully coupled poro-elastic finite element model including geomechanical load, depletion, and drawdown effects is utilized to quantify load, strain, and permeability changes of the SMP system during production and depletion. Impact of geomechanical load during production that may reduce the permeability of the SMP and affect production was evaluated for an offshore wellbore.

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Considerable efforts to model leak-off test (LOT) and leak-off behaviors have been carried out in the past. Altun presented a method to estimate leak-off volume by dividing the pressurized system into four sub-systems: mud compression, casing expansion, fluid leakage, and borehole expansion (Altun 2001). The volume response from each sub-system is then combined to represent the total volume pumped during a LOT. Most existing leak-off models do not account for mechanical behavior of cement and rock formations around the wellbore. While their compressibilities are small, the cement and rock formation volume changes can be significant. In this study, a mechanical expansion model has been developed, based on a linearly elastic, concentric cylinder theory developed by Norris (Norris 2003). The model is an extension of Lame' equations for multi cocentric cylinders and assumes the horizontal stresses on the system's boundary are applied equally in all directions, i.e., the horizontal, far-field stresses around the system are isotropic. The resulting model simulates the compound radial displacements of casing, cement, and formation along the cased hole, based on pressures inside the wellbore and in the far-field stress region. The volume generated from concentric cylinder expansion is then combined with Altun's mud compression volume and fluid leakage volume to simulate the total volume pumped during a LOT. One use of the model is the estimation of minimum horizontal far field stress. Since the model consists of concentric cylinders, the pressure on the outside boundary can approximate the minimum horizontal far field stress, which in turn and related to overburden pressure. The pressure inside the most inner cylinder is calculated from known mud weight. With an initial estimation for the far field stress and iterative methods, the minimum horizontal stress can be estimated. The developed models were then applied to field LOT data from the Gulf of Mexico. The results show that leak-off volume along the cased hole should be analyzed as a compound expansion of casing, cement, and formation. Since horizontal far field stresses in the GOM are almost equal (low anisotropy) (Salehi and Nygaard 2012), the Wider Windows LOT model simulates leak-off volume, leak-off behaviors, and far field stress.