College of Chemistry and Chemical Engineering,Southwest Petroleum University,Chengdu
In order to further improve the recovery of imbibition fracturing fluid after well Shut-In, this paper studies the influence of residue content in gel breaking fluid and average molecular weight of thickener on imbibition recovery. The results show that the higher the residue content and average molecular weight in gel breaking fluid, the lower the imbibition recovery. Therefore, based on the non-crosslinked associative thickener, using its structural characteristics and viscosity increasing mechanism, aiming at a block in Xinjiang Oilfield , a set of imbibition recovery non-crosslinked associative clean fracturing fluid system with low gel breaking residue and low molecular weight was constructed by optimizing the imbibition agent and studying the interaction between the imbibition agent and the non-crosslinked associative thickener. The composition of the system is as follows: non-crosslinked associative thickener CFZ (0.3%) + imbibition agent SZX-1 (0.2%) + ammonium persulfate APS (0.06%). The results show that the viscosity of the system is 77.43 mPa.s at 90℃ and 170 s-1 for 90 min, the contact angle of the gel breaker on the wet oil surface is 31.6°, and the oil-water interfacial tension is 0.62 mN/m, the residue content is 17.2 mg/L and the average molecular weight is 1.15 × 104, the imbibition oil recovery is 14.8%. The system provides theoretical basis and technical support for the efficient development of low permeability tight reservoirs.