A Decade of Self-Sealing Cement Technology Application to Ensure Long-term Well Integrity

摘要

Recent studies have shown that more than 50% of wells that are 15 years old or older have at least one casing string with sustained casing pressure. Cement sheath failure will result in sustained casing pressure, cross flow, lost production, collapsed casing, contaminated water zones and increased workover costs. Today, US federal regulation do not allow wells with sustained annular pressure to be plugged and abandoned. Remediation in these cases is both difficult and expensive. Therefore, utilizing a cement formulation which repairs itself in case of any failure under downhole conditions would be ideal for ensuring long-term well integrity and preventing the occurrence of sustained casing pressure. The objective of this paper is to review the self-sealing cement technology presented in the literature. This study manifests the latest novel laboratory equipment which allowed the cement to cure, get cracked and then seal under downhole conditions. The hydrophilic essence of this material provides a durable cement sheath to help ensure well integrity and zonal isolation for the life of the well. Mechanical properties testing could demonstrat the improved tensile to compressive strength ratio, lower Young's modules and higher Poisson's ratio. In addition, self sealing cement could self seal multiple times and therefore deliver a durable cement sheath in a wide variety of field cases.