The Preparation and Properties of a Gel Plugging Agent Made from Copolymerization of Modified Carbon Nanotube

Gel plugging agents usually have the characteristic of good adaptiveness, but the existing drilling fluid gel plugging agents generally suffer from poor stability at elevated temperatures and poor strength. To deal with these problems, a drilling fluid plugging agent was developed by the hybridization of high temperature carbon nanotubes and a terpolymer; the terpolymer gel is used as the matrix and the carbon nanotubes (CNTs) are used as the rigid nanoparticles to aim to solve the problems such as borehole wall instability resulted from the failure of the plugging agents at elevated temperatures in deep well drilling. A nanofiber plugging agent was synthesized by radical polymerization based on a molecular structure design in which maleic anhydride (MAH), alkenyl succinic anhydride (ASA) and styrene (St) were selected as the copolymerization monomers, benzoyl peroxide (BPO) as the initiator, and N, N-methylenebisacrylamide (MBA) as the crosslinking agent. The synthesized high temperature hybridized carbon nanotubes and terpolymer gel plugging agent was evaluated for its functional structures and plugging performance by transmission electron microscopy and sand-disc plugging experiment. The results of the evaluation show that, a drilling fluid treated with 1.0% of the synthesized product has the optimal plugging capacity. At 150℃, the drilling fluid has good rheological properties, good filtration control effect, and can effectively plug nano-micron sized pores and fractures.