Engineered Vesicles for the Controlled Release of Chemical Additives and Application for Enhanced Oil Well Cement Integrity

Abstract Encapsulation-based systems are of interest in the oil and gas industry in applications such as chemical additive preservation, small molecule release, particle delivery, and self-sealing materials. Many methods are used to encapsulate relevant chemical additives for the controlled release of contents like polymeric vesicles, inorganic shells, and mesoporous materials. Here a novel system for the controlled release of encapsulated cargo that utilizes engineered features of permeable polymeric shell walls is shown. When placing cement, a multitude of additives in large quantities are needed to meet a variety of functional needs that are suitable for the many diverse wellbore conditions. However, using large amounts of certain additives could have adverse effects which can destabilize the slurry at surface conditions. Using vesicles, cement additives are delivered without requiring modification. In this way, the possibilities of formulations comprised of a number of vesicles with various encapsulants lends to significant advancements in cementing. Applications in cement design is demonstrated from measurements obtained using the consistometer as well as testing from oilfield equipment. Experimental results show that a basic cement slurry design responds to the release of an encapsulant by the measure of change in viscosity and thickening times at two different temperatures at 3,000 psi. For example, the thickening time of a slurry can be controlled with the delayed release of an accelerant, at ambient pressure. With an increase in temperature up to 100 °F and 300 °F, the encapsulated additive is squeezed at a higher diffusion rate, resulting in a faster thickening time. In all cases, the vesicles are observed to remain intact within the set cement and contribute significantly to the mechanical properties of set cement. Vesicle dual performance stems from unique characteristics, such as an aqueous core, wall thickness and permeability, chemical composition, and mechanical integrity of the shell wall. Here, the shell walls are engineered with high molecular weight polymeric material that upon release of the encapsulated chemical additives, the emptied vesicles continue to impart beneficial mechanical properties to the set cement, such as compression strength.