Study On Indoor Evaluation Of Two Element Composite Flooding Aiming At Sazhong Development Area Of The Second Type Reservoir

In this paper, aiming at the geological characteristics、development situation、current problems of the second type reservoir in Sa-Zhong development area, the issues existing in the development of the polymer and the exploitation of the three element compound flooding are analyzed. The exploitation method of polymer / surfactant two element composite system was put forward. The displacement mechanism of polymer and surfactant and the synergistic effect of the surfactant were analyzed respectively. Then draw the main micro influencing factors of the oil displacement effect of the two element composite system, including rock wettability, capillary adsorption loss and crude oil emulsification, the number of chemical agents. The performance of the two element composite system was evaluated. Different configuration modes were designed to study the change of viscosity of polymer in different concentration. The lower limit value of polymer concentration was obtained according to the viscosity constraint. According to the scope of interfacial tension, the concentration limits of surfactant were obtained. The viscosity and interfacial tension stability of the two element composite system were studied. Conclude that the lower limit of the polymer concentration is 1400 mg/L. When the surfactant concentration changes in 0.1%~0.6%, the interfacial tension range of the two compound system is kept in the order of magnitude of 10-3mN/m. It can reach the limit value of the field application; The stability of the two element composite system reflects that the viscosity and interfacial tension stability is better.Based on the second type of reservoirs in the development zone of Sa-Zhong, Indoor experimental study on the relationship between polymer molecular weight, concentration and layer permeability, the resistance coefficient and residual resistance coefficient of the two element system are calculated. Determine polymer parameters of two element system suitable for the second type reservoir injection. Considering the concrete conditions of the second type reservoir permeability, Proposed using 16 million molecular weight polymer two element composite system for injection. Through experiment of oil displacement, analyze and compare the concentrations of different surfactant, different polymer concentration, different main slug size, different front slug size and different follow-up protective slug size corresponding oil displacement effect of two element system. Summarize the influence of various factors on oil flooding efficiency. The surfactant concentration was 0.3%, the polymer concentration is 1600mg/L and the viscosity is 40mP·s, when the main slug size is 0.3PV, the lead slug size is 0.03 PV profile control of high concentration polymer, the follow-up protection section is 0.2PV, the flooding effect of the composite system is the best.