Presently, water flooding low permeability reservoirs face severe development challenges, such as early water breakthrough, low productivity, and low recovery. In view of this, a CEOR method combined by warmlike micelle and surfactant imbibition was recommended and detailed in-lab evaluations were performed.
Warmlike micelle (WLM) made from viscoelastic surfactant (VES) has special rheological characteristics, showing great potential for swept volume increasing through viscosifying effect in low permeability reservoirs. Some surfactants can induce spontaneous imbibition through capillary force effect, wettability alteration, and oil film removal to enhance recovery. Herein, warmlike micelle and surfactant imbibition were combined to both increase swept volume and induce spontaneous imbibition.
Rheological properties, imbibition recovery, and core flooding performance were evaluated for a reservoir with average permeability of 3.51 ×10-3μm2. At shear rate of 7.34 s-1, the viscosity of 0.30% VES solution amounted to 25.4 mPa.s at 70 °C. Static imbibition test by outcrop showed imbibition recovery of 68.7% was achieved by surfactant AEC. After that, three runs of core flooding tests were conducted to evaluate the performance of prepared formulations. For VES only formulation, an incremental recovery of 8.50% was obtained after water flooding with recovery of 32.81%. For the combined VES and surfactant imbibition formulation, 14.82% incremental recovery was achieved. Synergistic effect of VES and spontaneous imbibition motivated more remaining oil because of dual effects.
The developed CEOR method takes advantages of VES and imbibition, demonstrating promising potential for further development of low permeability reservoir.