The Study And Evaluation Of The Nitrogen Foam Profile Control Agent

The main areas of Chinese oil fields have been the high water cut and natural depletion stage .Because of the function mechanism's restriction ,the effect of the general profile control technique becomes gradually bad ,the cost per ton oil rises continuously .It is hard to make larger effect in these areas.It is main problem in every oil field to improve the technique of control water breakthrough.Nitrogen foam system has the effect of selective plugging into high water cut layers and high permeable zones and can improve displacement efficiency, so it can be injected into thick reservoirs to control water breakthrough and drive the remaining oil. The profile control agent of foam have advantages of low cost , higher temperature resistance, plugging water and not plugging oil . It is a promising water plugging agent .Aimed at the increasing water cut, decreasing oil/gas ratio and the economic benefits declining of the oil reservoir in the late stage of water flooding of daqing oil field, the research of the foam-profile-control system for the reservoir is conducted. After the lab experiments,based the structure and the mechanism of foam stability, screened the blowing agents and the foam stabilizers and evaluated them we fought that the salinity can not affect the foam volume deeply but stability. The optimum concentration of the blowing agents and the foam stabilizers are 0.3%～0.5% and 0.03%～0.07%. The foam volume,half life,compatibility conditions and surface tension are concerned we elect the 3#A and WP as the optimum blowing agent and the foam stabilizers,Three excellent foaming systems were developed in this paper and they can be suitable for the geologic condition which temperature is lower 55℃, salinity is less than 7000mg/L and oil saturation is under 20%. And their properties were evaluated in different temperatures, formation water salinities and oil saturations. From the laboratory findings ,when the gas/liquid ratio is 1∶1～2∶1, the concentration of the foam system is 0.3% and the oil saturations is under 25% it has the excellent stabilities and sealing characteristics.They can fullfil the requeirment of profile control in this area and the theory of water shut off was provid.