Abstract
High injection pressure and the imbalance between water injection and oil production are two of the difficulties in developing low permeability oil reservoirs. Injecting gemini surfactants is a promising technique to overcome the difficulties to enhance oil recovery from low permeability oil reservoirs. Gemini surfactants enhance oil recovery by lowering the surface tension between oil and water. Gemini surfactant A and gemini surfactant B have same hydrophilic head group and hydrophobic tail. The two surfactants have equivalent capacity of lowering the surface tension between oil and water. Gemini surfactant A enhanced oil recovery by 4%, gemini surfactant B enhanced oil recovery by more than 10%. Based on the fractal dimensions of molecular fragments, the fractal dimension of the spacer group of gemini surfactant A is different from that of gemini surfactant B. The cores of the gemini surfactants flooding formation are analyzed by the method of box counting dimension. The fractal dimension of the spacer group of a gemini surfactant is in relation to the fractal dimensions of the cores.
Gemini surfactant C is subsequently designed and the fractal dimension of its spacer group is less than gemini surfactant B. Gemini surfactant C enhanced oil recovery by more than 20%.
The fractal dimension of the spacer group of gemini surfactant A is close to 2, and the fractal dimension of the spacer of gemini surfactant B is close to 1.4. The fractal dimensions of the cores range from 1.40 to 1.84. The fractal dimension of the spacer group of a gemini surfactant should be less than the fractal dimension of the microstructure of the reservoirs. The gemini surfactants are absorbed more onto the rock surface as the spacer groups of the gemini surfactants are less complicated than the rock surface.
The fractal analyses of low permeability oil reservoirs indicate the fractal dimensions are less than 2, which means the microstructure of low permeability oil reservoirs are different from medium-high permeability oil reservoirs. The fractal analyses of molecular fragments help design more exact and efficient oilfield chemicals.
