| Preformed particle gels (PPGs) have been developed and successfully used to improve conformance in heterogeneous reservoirs. However, no research has been reported to show their potential diverting applications in acidizing because of their unknown performance in this process. This work targets on evaluating the potential of PPGs to be used as diverting agents and factors influencing the diverting performance.;The swelling properties of three types of PPGs (PPG #1, #2, and #3) were first studied in brine and acid, including the swelling kinetics and equilibrium, PPG strength, and deswelling performance. Effects of different brine concentration, acid concentration, and temperature were also conducted. Then, coreflooding experiments were carried out to investigate their plugging, acid diversion, and permeability recovery performance in carbonate rocks. Effects of PPGs injection volume and particle size were finally investigated.;PPG #1 and #2 can swell up to about 10 times and maintain stable in acid for about one day before deswelling. Moreover, PPG #2 even swells a little more in acid at first several hours at 45 °C. PPG #3's swelling ratio ranges from 20 to 65, which is sensitive to the brine concentration and it reaches deswelling equilibrium after 20 minutes in acid. The gel strength of PPG #2 is the highest and it can be degraded in brine at 80 °C in five days. Coreflooding results show that these three PPGs have different diversion ability and can be used as diverting agents to enhance the acid stimulation. Larger injection volume and large particles are favorable by using PPGs as diverting agents in acidizing. The properties evaluation and coreflooding experiments show that PPG #2 can be the best candidate as a diverting agent. |
