Surfactant-Assisted Synthesis of Metal-Phosphonate Inhibitor Nanoparticles and Transport in Porous Media

A surfactant-assisted synthesis route was developed to form nanometer-size metal-phosphonate particles. The purpose is to develop a new treatment method for scale control. Aqueous solutions of calcium chloride and zinc chloride were mixed with a basic solution of either diethylenetriamine-penta (methylene phosphonate) (DTPMP) or bis-hexamethylenetriamine penta (methylene phosphonate) (BHPMP) in the presence of tetradodecylammonium bromide (TTAB) or sodium dodecyl sulfate (SDS) surfactant to form nanometer-size particles. The physical and chemical properties of the fabricated nanoparticles have been evaluated carefully. A large number of fabrication procedures are screened, and only those that yield metal-phosphonate particles of 50-200 nm in diameter are evaluated further. Furthermore, these nanoparticles should meet the criteria of forming stable suspension for more than I week at 70 C in 2% KCl solution. The nanoparticles can travel through the porous media and be deposited into the formation during a shut-in period. When production resumes, the inhibitor nanoparticles are dissolved into the produced fluid to prevent scale formation. The potential application of synthesized nanoparticles in scale treatment in oil fields has been tested by laboratory squeeze simulations, in which the nanoparticles were placed a distance away from the injection port, retained by the porous media, and returned slowly during flowback with synthetic brine. The retention and long-term-flowback performance of metal-phosphonate particles is reported.