中石化胜利油田分公司勘探开发研究院 山东 东营 257015
In order to solve the problem of high development cost of heavy oil thermal recovery in Shengli Oilfield, the viscosity reduction effect of a water-soluble viscosity reducer dispersive viscosity reducer was investigated. The changes of molecular structure and adhesion force of heavy oil before and after viscosity reduction were analyzed. The microscopic oil displacement mechanism was studied with microscopic visual oil displacement experimental model. The results show that the optimal concentration of dispersive viscosity reducer solution is 2% at formation temperature of 56 ℃. The optimal volume ratio of viscosity reducer solution to heavy oil is 1:6, and the viscosity reduction rate reaches 94.58%. The intermolecular force of dispersive viscosity reducer is mainly hydrogen bond, and its structure is stable. When the viscosity reducer is mixed with heavy oil, the heavy oil particles diffuse, and the P-OH group and carboxylic acid in the viscosity reducer intercalate into the heavy oil molecules. The complex sheet molecular structure of gum and asphaltene is broken, and the space network structure of colloidal asphaltene is destroyed. The molecular structure becomes loose and the association effect is weakened. The adhesion force decreases from 1.2×10-7N to 5.4×10-8N, with more than double drop. The viscosity of crude oil decreases due to the decline of internal friction between molecules. On the micro level, the dispersive viscosity reducer can disperse and separate the remaining oil from the blind end of the throat, parallel throat and small hole throat of the low permeability channel demonstrating the ability of oil displacement efficiency and profile control. The micro remaining oil distribution patterns are mainly surrounded cluster, parallel throat, dead corner point and circumfluent pore throat.