Polyaramide Vesicles Prove Effective for Wellbore Integrity and CO2 Sequestration

Abstract

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 204385, “Wellbore Integrity and CO2 Sequestration Using Polyaramide Vesicles,” by Elizabeth Q. Contreras, SPE, Saudi Aramco. The paper has not been peer reviewed. The complete paper describes a cementing additive chemically engineered to react with formation fluids that act antagonistically toward cement. Engineered polymer capsules house encapsulants to react with antagonistic gases downhole, such as carbon dioxide (CO2), to form a more benign and beneficial material. Embedded in cement, the polymer capsules with semipermeable shells allow fluids to permeate and react with encapsulants to produce beneficial byproducts, such as calcite and water from CO2. Reactivity between the encapsulant and antagonist gas CO2 is demonstrated using thermal gravimetric analysis (TGA) and other tests from oilfield equipment. Cementing Applications for Polyaramide Vesicles The study presents the third and final technology for polyaramide vesicles, a novel polymeric material for cement enhancement and for multifaceted cement applications. In oil and gas wells, polyaramide vesicles have applications as a cement additive with delivery capabilities. This family of polymers also is chemically inert and stable enough to serve in various applications under extreme downhole conditions during the construction of an oil well. When incorporated into cement, the high thermomechanical stability of these vesicles serves to enhance mechanical properties of Portland cement such as elasticity while maintaining the full strength of the cement. The unique vesicular design of the polymer also serves as a delivery system for relevant cement additives and is applied in the development of right-angle-set cements. Thereafter, the robustness of the shell remains intact after chemical delivery to impart strength and flexibility to set cement for the lifetime of the well. In this study, the vesicles housing reagents are used for the sequestration of antagonistic gases, to neutralize and to produce mineral precipitate for the applicatory repairs of microannuli in the cement sheath, and for self-healing cements. During the construction process, a good cement job serves the purpose of providing a reliable infrastructure during production and for zonal isolation of the casing string from subterranean environments. Zonal isolation by cementing is important to prevent the loss of hydrocarbons during production and to prevent the influx of unwanted formation fluids into the wellbore, such as sweet and sour gases. Maintaining cement-sheath integrity helps keep the production of hydrocarbons cost-efficient and safe. However, numerous factors may cause cement to fail. Oil and gas wells generally go through stress and thermal cycles during production. Changes in downhole conditions, in terms of temperature and pressure, can induce enough destructive stress to affect the integrity of the cement sheath. Any producing oil and gas well can suffer sudden thermomechanical fatigue failure, leading to microannuli and fractures in cement sheaths. Elastomeric materials such as polyaramide vesicles can be added to make cement less brittle and reduce the development of microannuli. However, in the event of gas migration by casing/casing annulus (CCA) events, mitigation requires a solution for complete remediation and recovery of the well.