where D is the plugging rate (%), Q is the permeability recovery rate (%), [K.sub.b] is the core permeability before OPPTA injection (mD), [K.sub.a] is the core permeability after OPPTA injection (mD), and [K.sub.r] is the core permeability after plugging removal (mD).
The influence of the emulsifier on the particle size of OPPTA was shown in Table 5.
The influence of emulsifier S-60 dosage on the particle size and stability time of OPPTA was shown in Figure 2.
The influence of stirring speed on the particle size of OPPTA was shown in Figure 3.
The influence of stabilizers on the particle size of OPPTA was shown in Table 6.
The influence of stabilizer A-1 dosage on the particle size and stability time of OPPTA was shown in Figure 4.
Preparing Method of OPPTA. 2 g S-60 and 38 g polyethylene wax were added to a flask and heated until polyethylene wax was completely melted.
The micromorphology of OPPTA was observed under a microscope at room temperature, as shown in Figure 5.
(1) A method for preparing OPPTA using polyethylene wax as the main raw material was put forward, which solved the problems of low plugging strength of the existing temporary plugging agent and low recovery rate of core permeability after plugging removal.
(2) Compared with the conventional oil-soluble temporary plugging agent W-11, the plugging rate and the recovery rate of core permeability after plugging removal of OPPTA were higher, which indicated that it had a better temporary plugging effect.
(3) By changing the preparation conditions, a series of OPPTA with different particle sizes could be prepared to meet the temporary plugging requirements of different reservoirs.
The authors are grateful to the Experimental Center of Drilling Technology Research Institute for assistance in temporary plugging ability evaluation experiment of OPPTA.