Laboratory Evaluation of a New Temporary Plugging Agent ZDJ

A new temporary plugging agent, ZDJ, was produced to overcome the deficiencies of conventional reservoir protection technology and elastic sealing agents. ZDJ has a core-shell structure, and good deformability enabling it to be adhered on to the interior surface of pore throats, thus protecting reservoir from being damaged. This technology does not necessitate the accurate compatibility of additive's particle sizes with diameters of pore throats. ZDJ is produced with AM, AMPS, DMC, N, N'-Methylene bis-acrylamide and an inorganic agent A, using radical polymerization.The black part at the center is a rigid core, and the transparent part at the brim is an elastic mass. The evaluation indicates that ZDJ shows the optimum plugging performance at 50% (mass fraction) of A. Sand beds plugged with 0.5% ZDJ have fluid invasion depths of 2.3-5.9 cm, and API filter loss of 8.5 mL. When ZDJ, sulfonated asphaltene and LV-CMC are compounded at a ratio of 4.5:1.5:1.0, the best plugging and filtration control performances can be achieved. Sand beds plugged with 1.0% of the compound have fluid invasion depths of 0.6-2.7 cm, and filter loss of 6.1 mL. In tests on artificial sand cores having permeabilities of 200×10^-3-300×10^-3 μm²,99.2% of pores are plugged with the compound, and permeability recovery reaches 99.3%, indicating that ZDJ, sulfonate asphaltene and LV-CMC have good synergistic effect in hindering the invasion of mud filtrates and solids, thus realizing the protection of oil and gas reservoirs.