Oil displacement performance and mechanism of Interfacially Active polymer (IAP)-Emulsifying viscosity Reducer (EVR) supramolecular compound system in heterogenous heavy oil reservoirs

Chemical Cold Heavy Oil Production (CCHOP) represents an effective approach to exploit heavy oil by injecting Oil Viscosity Reducer (OVR). However, the challenge lies in the crossflow of traditional OVR through high permeability channels in heterogeneous heavy oil reservoirs. a supramolecular compound system comprising Interfacially Active Polymer (IAP) and Emulsifying Viscosity Reducer (EVR) were proposed as a novel CHHOP agent to address this problem. A series of experiments were conducted to investigate the heavy oil displacement performance and mechanism of the IAP-EVR compound system, including assessments of heavy oil emulsification, emulsion stability, rheological properties, single-core oil displacement, and heterogeneous microscopic oil displacement. The results demonstrate that a stable O/W emulsion can be formed with the 0.1 wt% IAP-0.3 wt% EVR compound system under a low mixing rate of 200 rpm. The emulsion exhibits only an 8.0% dewatering rate and a low TSI value of 0.8. Moreover, the compound system effectively reduces the heavy oil viscosity from 1000 mPa center dot s to 325.7 mPa center dot s, facilitating the emulsification of the remaining oil after water flooding and enhancing its flowability, thus improving oil displacement efficiency. Additionally, the 0.1 wt% IAP-0.3 wt% EVR compound system increases the solution viscosity to 600 mPa center dot s, leading to a low W/O mobility ratio, which enhances the swept volume. Supramolecular association is identified as a crucial mechanism for stabilizing the emulsion and increasing the solution viscosity, as evidenced by a high elastic modulus of 144.7 mPa and a transition area observed in the viscosity-shear rate curve. In comparison to HPAM and IAP, the 0.1 wt% IAP-0.3 wt% EVR compound system yields higher oil recoveries of 21.84 %OOIP in the single core experiment. Moreover, noticeable emulsification is observed in the produced fluid, and oil recoveries of 89.85 %OOIP and 92.98 %OOIP are achieved in high and low permeable areas, respectively, in the heterogeneous microscopic model. These results indicate a mechanism that enhances both the swept volume and oil displacement efficiency. Overall, the findings of this study provide a laboratory foundation for the promising application of the IAP-EVR compound system in heterogeneous heavy oil reservoirs.