A High-performance Waterproof Lock Agent For Low Permeability Reservoir

Low permeability reservoir has the characteristics of dense rock, poor physical properties and small pore throat. External fluid can enter the pore throats of the reservoir under the action of capillary force, causing water lock damage, which seriously affects the production of low permeability reservoir. To solve this problem, a new type of fluorocarbon waterproof lock agent (FS-1) was prepared with perfluorooctanoic acid, ethanolamine and sodium chloroacetate as raw materials, and its structure was characterized by infrared spectrum, and the effect of fluorocarbon waterproof lock agent on the water-locking performance of brine solution in core pores was studied. The results showed that the waterproof lock agent can significantly reduce the surface tension of the brine solution (＜15 mN/m), and increase the contact angle of the distilled water on the sandstone surface to 85.3°, indicating that the developed waterproof lock agent can change the core surface wettability from hydrophilic to neutral wet, and effectively reduce the water locking damage to the cores. In addition, the waterproof lock agent (FS-1) contains multiple adsorption and salt-resistant groups, which can improve the adsorption ability of the molecule on the rock surface and makes its salt tolerance reach 7% (NaCl). Imbibition experiment, permeability test experiment and nuclear magnetic resonance experiment found that the waterproof lock agent (FS-1) slowed down the self-imbibition of the core, reduced the binding ability of the core pores to salt water and the water locking damage of the core, and improved the recovery rate of the core permeability.