Cap Rock Restoration in Plug and Abandonment Operations; Possible Utilization of Rock-based Geopolymers for Permanent Zonal Isolation and Well Plugging

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The fundamental of a plug and abandonment operation is to restore cap rock functionality for securing the well-integrity permanently. The current work reviews briefly essential characteristics of plugging materials. Besides, since geopolymers have been suggested as a possible well barrier element, rheological behavior and mechanical properties of a rock-based geopolymer is presented. The consistency and viscosity of different mix designs were investigated to study the placeability of the mixes. Although the slope of the acquired viscosity data may show a Newtonian fluid behavior, a non-Newtonian model (Herschel-Bulkley) simulated the experiments with a lesser deviation than the power-law model. Strength development of the produced geopolymers showed sufficient strength. Confined triaxial compression tests were performed to measure the Bulk modulus, Poisson's ratio, E-modulus and Young's modulus at downhole conditions. Very low Young's modulus (238 Kpsi) and Poisson's ratio (0.01) were measured. The setting time of the mixtures was delayed by using sucrose without compromising the right-angle-set. The use of sucrose as a retarder by 1.9 w% of the total solid phase did not affect the mechanical properties. SEM analysis showed some unreacted aplite particles within the geopolymers. The initial results showed that the rock-based geopolymer has the potential to be utilized as a well barrier element for permanent well plugging and zonal isolation.