A Study On Stimulation Of Injection Well Of Low Permeability And High Temperature Reservoir By Surfactant Flooding

High injection pressure is a universal problem for low permeability reservoir. Surfactant flooding is an effective method to the problem. Liuxi oilfield is a typical low permeability and high temperature reservoir. Its average porosity and permeability are 12% and 5×10-3μm2 respectively, and the formation temperature is 120℃. This desertation analyses the causes lead to the high injection pressure through well performance, microscopic pore structure, water properties, rock sensibilities and oil properties; chooses the suitable surfactant and evaluates it through, preventing caly swelling and scale formation, sterilization and changing rock wettability; studies the fundamental rules and effects of surfactant flooding by physical modeling and numerical simulation through injection concentration, injection timing and slug length. The research results are as following:1. Poor reservoir physical properties, strong weter-sensitive and poor oil properties cause the injection pressure rises. The suitable surfactant is ZK-S, which can reduce the oil-water interfacial tension to 10-2 mN/m and make the rock more water-wet. It's good at thermal stability and compatibility and anti-clay-swelling, scale prevention and sterilization.2. Core flooding experiments and mumerical simulation both show that the preferable concentration of surfactant is 0.15%, and surfactant injection is effective at any stage of the water flooding. In the core experiments, the water and oil relative permeability both improve in surfactant flooding relative to water flooding, the water saturation at which the water and oil relative permeability are equal becomes greater, and residual oil saturation decreasesre remarkably. 3. Numerical simulation shows:①Surfactant flooding can reduce the injection pressure by 11.3% relative to water flooding, extend water-free oil production period and effective production period, improve oil recovery rate by a large scale, and reduce the saturation of residual oil. The water-oil flood front is the most important stage of surfactant flooding.②Surfactant injecting can reduce injection pressure to the same level and achieve the same ultimate recovery at any stage of the water flooding. The earlier starting injecting surfactant, the more oil recovery rate improves. "Oil-wall" is a key performance of surfactant flooding.③The drop in injection pressure is remarkable during the injecting time, and unremarkable during the follow-up water flooding. The rates of water cut increasing and daily oil production decreasing are slow down and the recovery improves as the surfactant slug lengthens, and the optimal slug length is 0.7PV. The rate of oil recovery is slightly related to surfactant slug length.