Preparation And Performance Evaluation Of Modified Polyacrylamide Particle Temporary Plugging Agent

In the process of acid fracturing or repeated fracturing in oil fields,it is necessary to temporarily block the original cracks and realize the steering of acid liquid or fracturing fluid.In some high-deep wells,the formation temperature which exceeds 100 °C needs to be plugged,therefore,the temporary plugging agent is required to have high temperature resistance and high strength.However,the commonly used polymer water blocking agents have problems such as poor thermal stability,short sealing effective time,and weak pressure bearing capacity.In order to solve these problems,this paper developed a high temperature resistant water-soluble particle temporary plugging agent.Then we have discussed the suitable particle concentration of the temporary plugging agent and the matching method of different particle sizes,and investigated the breakthrough pressure gradient.The result is as follows:(1)According to the initiation mechanism and influencing factors of the high molecular polymer,the polyacrylamide is modified by using monomers with different functions,different initiators and synthesis methods.(2)Through a large number of indoor synthesis experiments and preliminary screening and evaluation,it was determined that the main components of the temporary plugging system were copolymerized by AM,MMA and AMPS.Then using N,N-methylenebisacrylamide as a crosslinking agent.The initiator,crosslinker,stabilizer,and the concentration of ingredients in the polymer system is screened and optimized.(3)Through the indoor performance study,the expansion performance in the carrier and the degradation rate in the formation environment of AM/AMPS/MMA temporary plugging agent fluid,and the core sealing ability were investigated.At 130 °C,48 h,the degradation rate of the temporary plugging agent in 20% hydrochloric acid,water,and formation water can reach more than 95%,the residue rate is less than 5%.The maximum pressure of AM/AMPS/MMA temporary plugging agent in the core experiment of 1 mm crack reached 18 MPa,and the maximum bearing pressure reached 15 MPa in the core experiment of 2 mm crack.Moreover,the plugging agent also has the characteristics of low cost,high temperature resistance,good sealing effect and low residue residual rate.A high temperature resistant polyacrylamide particle temporary plugging agent was prepared by screening monomer and optimizing reaction conditions.This temporary plugging agent is valuable of potential application in oil field acid pressure and repeated fracturing process.