Study and Application of Self-diverting Fracturing Fluid Containing Highly Deformable Temporary Plugging Agents

The natural fractures abundantly developed in the pyroclastic rocks in the Nanpu No. x structure are conducive to the construction of complex fractures and the improvement of the effect of stimulated reservoir volume fracturing. In previous self-diverting temporary plugging fracturing operation, the effect of temporary plugging has been unsatisfactory. To resolve this problem, the temporary plugging agent was optimized using silicone monomer which forms a highly deformable gel through micellar polymerization. The gel, after shearing, granulating, drying and pulverizing was turned into highly deformable expandable temporary plugging agent of different particle sizes to temporarily plug the mouth (inside) of fractures. This pulverized temporary plugging agent can automatically solidify at elevated temperatures to form a filter cake through condensation, thereby improving the effect of temporary plugging inside the fractures. The optimum ratio of different particles in the final plugging agent formulation (between two well clusters) through laboratory experiment is: deformable particle (5 – 6 mm) ∶ fiber ∶ powder (100 – 200 mesh) = 5∶1∶1, and the highest breakthrough pressure of this temporary plugging agent is 56.3 MPa. The deformable particles in the temporary plugging agent can expand after absorbing water, and has good elasticity, which greatly increase the likelihood of stress diversion. This temporary plugging agent, a nanometer powdered product, can produce a plugging barrier withstanding a pressure of up to 54 MPa. The temporary plugging agent has been used in the operation in volcanic rock reservoirs without the need of special fracturing trucks. The temporary plugging agent did not affect the pump efficiency, and pumps did not get stuck during field operation. The success rate of the temporary plugging agent was 100%. Pressure increases because of temporary plugging between two well clusters are obvious, averaged between 4 and 16 MPa. The pressure increases inside the fractures because of the temporary plugging were 2 – 4 MPa in average. Fracturing curves of field operation and micro-seismic monitoring showed that the diverting efficiency was high.