Abstract
This study focuses on the application of a cationic inorganic aluminum/zirconium-based polymer clay stabilizer to prevent swelling of smectite particles in a sandstone matrix. Previous work has focused on mitigating fines migration; swelling mitigation is tested here. This cationic polymer will fasten itself to negatively charged clay platelets in the matrix, preventing loss of permeability by minimizing interaction of fresh water with the clays.
Berea sandstone cores are injected with a montmorillonite slurry to supplement the very low concentration of naturally occurring swelling clays. The modified Berea cores are subjected to a coreflood consisting of a treatment of Al/Zr-based clay stabilizer prior to a potentially damaging fresh water shock. Permeability is calculated from measured pressure differential across the core; decrease in permeability indicates damage to the core. Coreflood effluent samples are analyzed with Inductively Coupled Plasma/Optical Emission Spectrometry to indicate presence of key cations evacuating the core.
Permeability loss in Al/Zr-based stabilized cores during fresh water shock was negligible when compared to that of an untreated core. The Al/Zr stabilizer performed well as an agent which prevents clay swelling and fines migration in the presence of fresh water. Performance of the stabilizer at different concentrations suggests that an increase in stabilizer concentration does not correlate directly with permeability maintenance.
Clay swelling and fines migration can damage hydrocarbon-bearing rock formations and prevent economic realization of oil/gas wells. Identification and management of clay particles in the formation is a necessary component of production and drilling engineers' responsibilities. As effective, environmentally friendly options for fines management are developed, circumstantial utilization thereof is incumbent.
