The Synthesis and Evaluation of a High Temperature Nano Micro-Spherical Polymer Plugging Agent

A nano micro-spherical polymer plugging agent OPTB was developed to try to replace the flexible plugging agents presently in use, which have the shortage of low thermal stability. OTPB is a high temperature plugging agent and is synthesized through free radical micellar polymerization with several raw materials such as acrylamide (AM), sodium p-styrene sulfonate (SSS), sodium acrylate (AAS), 1H,1H,2H,2H-perfluorooctyl acrylate (TEAC) and 1,3,5-tris(methacrylamido) benzene (B-TMAC). The polymerization used 1-((cyano-1-methylethyl) azo) formamide as the initiator, and dodecyl mercaptan (TDDM) as the molecular weight regulator. The optimum synthesis conditions were determined through orthogonal experiment, as follows: reaction temperature = 105 ℃, reaction time = 20 h, concentration of the monomeric raw materials = 7.5%, concentration of CABN = 0.4%, and concentration of TDDM = 1.5%. The molecular structure of OPTB was characterized with ¹H-NMR. Experiment on the properties of the drilling fluid treated with OPTB showed that OPTB has little effect on the rheology of the drilling fluid, and the quality of the mud cake was significantly improved. After aging at high temperature, the particle size of OPTB is still in a monodisperse state. At a concentration of 3.0%, 90.84% of the nanometer-sized and micron-sized pores can be plugged by OPTB, and this plugging effect can effectively slow down the transmission of the pressure of the fluid column in the wellbore into the formations. The micromorphology of OPTB before and after aging at 160 ℃ for 16 h observed under SEM showed that the particles of OPTB are spherical with narrow size distribution. At elevated temperatures, part of the OPTB particles is still in monodisperse state.