  The possibility for hydrocarbon fluids to migrate through debonded
micro-annuli wells is a major concern in the petroleum industry. With effective
permeability of 0.1-1.0 mD, the existence of channels in a cement annulus with
apertures of 10-300 micrometer constitutes a major threat. Squeeze cement is
typically difficult to repair channels-leakage with small apertures; hence, a
low-viscosity sealer that can be inserted into these channels while producing a
long-term resilient seal is sought. A novel application using nano-silica
sealants could be the key to seal these channels. In the construction and
sealing of hydrocarbon wells, cementing is a critical phase. Cement is prone to
cracking during the life cycle of a well because of the changes in downhole
conditions. The usage of micro-sized cross-linked nano-silica gel as a sealant
material to minimize damaged cement sheaths is investigated in this study.
Fluid leakage through channels in the cement was investigated using an
experimental system. With a diameter of 0.05 inches, the impact of the cement
channel size was explored. The sealing efficiency increased from 86 percent to
95 percent when the nano-silica concentration of the sealing gel increased from
13 percent to 25 percent. This demonstrates that the concentration of
nano-silica in the sealing gel affects the gel's ability to seal against fluid
flow. This research proposes a new way for improving cement zonal isolation and
thereby lowering the impact of cement failure in the oil and gas industry.
