Cementing is a major step in the construction and sealing of hydrocarbon wells. During the life cycle of the well, cement is prone to cracking due to a change in downhole conditions. This research investigates the use of micro-sized crosslinked polymer gel as a sealant material to mitigate cracked cement sheaths. Two experimental setups were designed to investigate water leakage through cement. The impact of polymer gel strength on the gel's ability to seal cement cracks was investigated using four gel strengths, including 500 pa, 1200 pa, 1450 pa, and 2440 pa. The impact of the width of the cement crack was also investigated using 0.5, 2, 3.2, and 6.75 mm. Results showed that the polymer gel propagated across fractures like a piston with no gravity effect and with angle with gravity effect. Blocking efficiency to water flow is controllable, and it can be increased if a high strength polymer gel is selected. To the authors' knowledge, very little experimental work has been conducted to investigate the use of crosslinked micro-gel in cement zonal isolation. This study can provide the oil and gas industry with a better understanding of the materials to use in improving cement zonal isolation and thus reduce the impact of cement failure.

Remedial cementing job is an important operation conducted in the petroleum industry to restore the primary cementing integrity of oil and gas wells. The remedial job is needed when the integrity of the primary cement is compromised and the wellbore is prone to fluids migration. This work studies the behavior of several sealants that can be used in a remedial job including solids-free material, semi-solids material, and Portland cement. The focus of this study is on testing the rheological behavior, the injectivity, the effect of the size of cement's voids on the injectivity of different sealants, and the strength of the sealants. Laboratory experiments were conducted to evaluate the performance of several sealants in different cement's voids sizes. The results of this work demonstrate that solids-free materials such as epoxy resin has the highest injectivity among the tested sealants even in very small gaps. The epoxy resin develops higher compressive strength than that of the conventional Portland cement. This work points out the importance of selecting the appropriate type of sealant on the effectiveness of the remedial job.