Preparation And Properties Of Polymer Gel Temporary Plugging Agent Based On Layer-y-layer Assembly

Polymer gel has been developed as a new temporary plugging agent with great application potential because of its special water-plugging properties of water absorption and the adjustability of its structure and properties.It has the dual functions of water plugging and oil displacement.It is an important direction and hotspot in the study of temporary plugging agents for fracturing engineering.In this thesis,temporary plugging agent with special water shutoff properties,based on P(AA-AM)/MMT polymer composite gel,was prepared via the traditional solution polymerization by using acrylamide and acrylic acid as comonomer,it will be used as the matrix material for water plugging agent.Using multilayer assembly technology,combined with the materials with temperature-sensitive and phase change functions to form different surface layers,a temporary plugging agent deried from polymer composite gel with multi-layered structure was prepared.It can greatly improve the migration characteristics and stability of temporary plugging agents in rock core on the basis of effectively maintaining the compressive strength,plugging capacity and water plugging performance of the composite gel temporary plugging agent.The structure of temporary plugging agent is intelligent and controllable.The effect of preparation process and composition on the water absorbency of composite gel temporary plugging agent was studied.The relationship between the viscosity and aging time of polymer composite gel temporary plugging agent and the content of different components was investigated.The relationship between water absorbency of polymer composite gel temporary plugging agent and different factors(time,temperature and salinity)was analyzed.Based on the relationship between the structural composition and water plugging performanc e,two types of intelligent composite gel temporary plugging agents with good migration characteristics and stability were developed from the structure,composition and functional design of temporary plugging agents.(1)AM(AA)and montmorillonite(MMT)were used as raw materials,aluminum nitrate as ionic crosslinking agent,potassium persulfate as initiator,and P(AA-AM)/MMT polymer composite gel temporary plugging agent was successfully prepared by solution polymerization and nanocomposite technology.Takin g aging time and water absorption as the main research objects,the effects of the content of ionic crosslinking enhancer,initiator,montmorillonite,acrylamide and acrylic acid,and the ratio of acrylic acid to sodium hydroxide were systematically invest igated.The environmental conditions of reservoir formation were simulated in laboratory.The results show that the optimal conditions of influencing factors are:n(NO₃)₃/n AM=0.17%;n K₂S₂O₈/n AM=1.65×10^-4;n AA/n AM=0.825;The neutralization degree of acrylic acid is 80%,the reaction time is 3 h,and the reaction temperature is 65?.(2)Polyacrylamide based composite gel temporary plugging agent was used as the basic material for water plugging.Polycaprolactone(PCL)with temperature sensitive phase change function was used as the surface modification layer material.The self-assembly technology was adopted to modify the platform by the two stage reaction of poly(PDA).The multi-stage structure p(AA-AM)with temperature sensitive water absorption switch on the surface was successfully fabricated/MMT@PCL Polymer composite gel temporar y plugging agent.The influence of structure and composition on the water absorbency of compound gel temporary plugging agent was studied.The relationship between the viscosity and aging time of polymer composite gel temporary plugging agent and the conte nt of different components was investigated.The relationship between water absorbency of polymer composite gel temporary plugging agent and different factors(time,temperature and salinity)was analyzed.The relationship between its structure and water p lugging performance was revealed.The results showed that when the content of PCL was 2%(W),the water absorption performance was the best.Its water absorption rate is positively correlated with temperature in a certain period of time,and it has high sa lt resistance.The prepared multifunction polymer composite gel temporary plugging agent has delayed swelling property and gives intelligent control of temporary plugging agent structure and water plugging characteristics.Therefore,the temporary plugging agent has good migration characteristics and stability in the formation,and can migrate to deep or corner areas to achieve the temporary plugging function.(3)Using the two stage reaction modification platform of polydopamine(PDA),and self-assembly technology was used to assemble the hydrophobic paraffin wax(C₂₅H₅₂)on the surface of polyacrylamide based composite gel temporary plugging agent.A multi-stage structure P(AA-AM)with low temperature hydrophobicity and high temperature dissolution surface was successfully prepared.MMT@C₂₅H₅₂Polymer composite gel temporary plugging agent.The influence of structure and composition on the water absorbency of compound gel temporary plugging agent was studied.The relationship between the viscosity and aging tim e of polymer composite gel temporary plugging agent and the content of different components was investigated.The relationship between water absorbency of polymer composite gel temporary plugging agent and different factors(time,temperature and salinity)was analyzed.The relationship between its structure and water plugging performance was revealed.The results showed that when the content of paraffin is 4%(W),the water absorption performance was the best.Its water absorption rate is positively correl ated with temperature in a certain period of time,and it has high salt resistance.The multifunction polymer composite gel temporary plugging agent has low temperature hydrophobicity and high temperature ablation surface.The existence of the surface layer gives the composite gel temporary plugging agent the delayed swelling property and the controllability and stability of water absorption and water shutoff function.Therefore,the temporary plugging agent has good migration characteristics and stability in the formation,and the temporary plugging agent can migrate to deep or corner areas to achieve temporary plugging function.