The invention discloses a preparation method and application of a modified
lignin-based gel water shutoff agent, and the preparation method comprises the following preparation steps: step A, putting a
lignin raw material into a reaction container, uniformly stirring, adding a carboxymethylation modification
reagent, and reacting for a period of time at a certain temperature; step B, adding an
epoxy modification
reagent, and reacting for a period of time at a certain temperature; c, adding a
polyvinyl alcohol solution, uniformly stirring, and cooling; and D, adding a cross-linking agent to adjust the concentration, uniformly stirring, transferring into a high-temperature-resistant
pipe or a high-temperature-resistant tank, putting into an electrothermal blowing
dry box, and reacting at 100-200 DEG C to form gel, thereby obtaining the modified
lignin-based gel water plugging agent. The lignin is subjected to
chemical modification, the modified lignin contains carboxyl and
epoxy groups at the same time and then acts with the cross-linking agent and the like, the lignin is cured into gel at high temperature, the temperature-resistant and salt-resistant water shutoff agent is formed, the modified lignin is easy to cross-link, the strength after cross-linking and curing is high, and a cured product is good in
temperature resistance.