Surfactant Flooding Technology

At present, our country has been probing geologic reserves of low permeability oil field more than 50, one hundred million tons of changqing oil field but also in low permeability reservoirs, this kind of reservoir in put into development by water flooding, the oil and gas reservoir of low permeability lead to high water injection pressure, drilling is difficult. After the reservoir water is flooded, there is still a large amount of residual oil in the matrix rock mass, and the average recovery level is about 20%. Therefore, the utilization of surfactant water flooding technology to improve the recovery rate has a broad market prospect

The concentration of surfactant < CMC (critical micelle concentration) is called active water, and the active water is a dilute surfactant system. In active water flooding, the active agent is sulfonate type and sulfuric acid salt type anionic surfactant, which is permeable type non-ionic surfactant or salt-tolerant. Active water is the most simple surfactant flooding, which is called active water flooding

Technical mechanism of surfactant：

   1、Low interfacial tension mechanism (The tension decreases and the wetting Angle increases)                  

　　      ，     Ｗ ——work of adhesion；

             　　　          ——oil-water interfacial tension；

              　　　         ——Oil wetting Angle on the surface of the formation

2、Wetting reversal mechanism

The surfactant reduces the interfacial tension of the oil and water, and changes the wettability to make the contact Angle larger, the adhesion work decreases, the oil is easily pulled from the rock, and the recovery rate is increased

3、Reduce the capillary resistance of the oil-wet oil layer

 The active agent can reduce the capillary resistance of the oil-wet oil layer and the resistance of the capillary force to the water drive oil. The wetting Angle increases, the resistance of the capillary force decreases, and the active water enters the smaller radius, the original and not to go to the capillary, increases the sweep coefficient, improves the recovery rate

Pc=

     ，       Pc ——Capillary force；

                       σ  ——oil-water interfacial tension；

           R   ——Capillary radius；

                      θ ——The angle of oil moistens to the rock surface.

4、Emulsion Mechanism

Rock to wash down the oil droplets by surfactant emulsion into O/W emulsion, emulsion superposition of fluid resistance by capillary effect, increase the resistance of the high permeable interval, injected water into the low permeable interval, improve sweep efficiency.

5、Emulsion Mechanism

Rock to wash down the oil droplets by surfactant emulsion into O/W emulsion, emulsion superposition of fluid resistance by capillary effect, increase the resistance of the high permeable interval, injected water into the low permeable interval, improve sweep efficiency.