Volume 63

Experimental study on optical fiber monitoring of interface strain field in CCUS injection well cementing process BoJia Li , XiaoRong Li*, YunZhang Li , Yang Li , ShiYu Zhang ,RongBo Li , XueLian He , YongCun Feng

Abstract

In carbon capture, utilization, and storage (CCUS) systems, the wellbore cement sheath serves as a critical barrier to ensure the safety and effectiveness of the entire system. Its integrity is directly related to the long?term storage performance of carbon dioxide. During cementing, expansion and shrinkage resulting from cement hydration are primary causes of stress concentration, micro-fracture development, and interfacial bond failure. However, conventional cementing monitoring methods are limited to capturing the cement sheath condition at discrete measurement points or specific time instances, which falls short of the requirements for long-distance and real-time continuous monitoring. As a distributed optical fiber sensing technology, optical frequency domain reflectometry (OFDR) offers high precision, high sensitivity, and high spatial resolution, enabling accurate strain monitoring of target objects. This study employs optical frequency domain reflection technology to conduct calibration tests on both bare and tight-sheathed optical fibers, as well as strain monitoring tests at the first interface during the cement hydration process. The differences in monitoring performance between bare and tight?sheathed fibers are investigated, and the strain evolution at various locations of the first interface throughout cement hydration is elucidated. The results demonstrate that OFDR-based optical fiber monitoring technology can accurately track interfacial strain variations and cement expansion–shrinkage behavior during the cement hydration process in CCUS well cementing. The research results can provide reference and guidance for optical fiber monitoring of cement hydration and integrity evaluation of cement sheath in CCUS injection wells.

Keywords cement sheath integrity, CCUS injection wells, strain monitoring, distributed optical fiber