Polymer-Cement Composites with Self-Healing Ability for Geothermal and Fossil Energy Applications

Abstract

Sealing of wellbores in geothermal and tight oil/gas reservoirs by filling the annulus with cement is a well-established practice. Failure of the cement as a result of physical and/or chemical stress is a common problem with serious environmental and financial consequences. Numerous alternative cement blends have been proposed for the oil and gas industry. Most of these possess poor mechanical properties, or are not designed to work in high temperature environments. This work reports on a novel polymer-cement composite with remarkable self-healing ability that maintains the required properties of typical wellbore cements and may be stable at most geothermal temperatures. We combine for the first time experimental analysis of physical and chemical properties with density functional theory simulations to evaluate cement performance. The thermal stability and mechanical strength are attributed to the formation of a number of chemical interactions between the polymer and cement matrix including covalent bonds, hydrogen bonding, and van der Waals interactions. Self-healing was demonstrated by sealing fractures with 0.3–0.5 mm apertures, 2 orders of magnitude larger than typical wellbore fractures. This polymer-cement composite represents a major advance in wellbore cementing that could improve the environmental safety and economics of enhanced geothermal energy and tight oil/gas production.

Atomic Origins of the Self-Healing Function in Cement–Polymer Composites

“…To study the cement–polymer interface, a simplified polymer strand was used based on the polymer materials used in our recent study …”

“…The failure of the cement lining of the geothermal wells caused by the high temperature (up to 400 °C) and chemically corrosive geothermal production environments always lead to very bad environmental and economic impacts. There have been considerable attempts to tackle these problems; however, despite advancement in the development of cementitious materials for geothermal applications and self-healing cements in general, , self-healing cements with improved adhesion at both the casing and formation interfaces under geothermal conditions have only recently been developed by us . We have carried out a systematic study suggesting that the addition of select polymers, such as self-healable thermoset epoxy resins, into cements can produce a composite with self-healing and readhering abilities .…”

“…There have been considerable attempts to tackle these problems; however, despite advancement in the development of cementitious materials for geothermal applications and self-healing cements in general, , self-healing cements with improved adhesion at both the casing and formation interfaces under geothermal conditions have only recently been developed by us . We have carried out a systematic study suggesting that the addition of select polymers, such as self-healable thermoset epoxy resins, into cements can produce a composite with self-healing and readhering abilities . This novel polymer–cement composite possesses various desirable properties such as high stability at most geothermal temperatures, self-healing ability, or sealing fractures with wide apertures, and constitutes a much-improved alternative to conventional wellbore cement materials.…”

“…20 We have carried out a systematic study suggesting that the addition of select polymers, such as selfhealable thermoset epoxy resins, into cements can produce a composite with self-healing and readhering abilities. 20 This novel polymer−cement composite possesses various desirable properties such as high stability at most geothermal temperatures, self-healing ability, or sealing fractures with wide apertures, and constitutes a much-improved alternative to conventional wellbore cement materials. Motivated by these findings as well as the need to connect molecular-level information with macroscopic properties to enable a predictive design, we performed ab intio molecular dynamics (AIMD) that explicitly account for the roles of electrons and nuclei at finite temperatures.…”

Recent Advances in Intrinsic Self‐Healing Cementitious Materials

“…For autonomous healing, a specific environment is usually created in which cracks can be healed . According to the healing mechanism, there are three typical substances applied to achieve autonomous healing in cementitious materials: (1) mineral admixtures, (2) bacteria, and (3) polymeric adhesive agents . For the first two substances, the host–guest chemical reactions intrinsically occur to bridge the crack faces.…”