Study On Nitrogen Foam Flooding And Displacement Technology In Heavy Oil Reservoir Of Fengcheng Oilfield

The heavy oil reservoir in Fengcheng has gone through several periods including thermal producing test,scale development using steam stimulation and steam flooding test. The steam channeling among stimulation wells and production wells happens easily because of the high viscosity of oil,the fingering phenomenon and high mobility ratio between steam and oil. Accordingly,low exploitation efficiency results in the rise of water ratio in oil wells and the decrease of periodic oil production,gas-oil ratio,thermal utilization factor. Finally it leads to the decline of natural production and worse extracting efficiency.Nitrogen foam has the feature of "plugging big holes instead of small ones, plugging water instead of oil", thus it can selectively control the mobility of fluid, and reduce the permeation rate of the injected fluid in high permeability zone. Then channeling paths will be blocked.Thereby, swept volume can be raised and oil recovery can be enhanced.The thesis is well organized based on the heavy oil condition in Fengcheng Oil field and all advanced foam theory both at home and abroad.(1) The high temperature resisted foaming agent was firstly well selected, then foam stabilizer and auxiliary with good characteristics was selected. Finally the suitable formula was developed with generalized evaluation coefficient method and unstable coefficient method through lab experiments:0.3%F4+0.3%F2+0.05%W1+0.05%Zl;100ml of the formula fluid can make865ml foam system, with the half produce time is185min;.(2) Further experiments were done in order to evaluate the properties of the formula The temperature resistance and salinity endurance are good. The formula is stable when it contains a little oil. Oil demulsification in gathering and transportation system is not much effectted.(3) Core flood experiments show that when the gas liquid ratio is1:1, there is a high plugging effet of foam system, the resistance coefficient is47.4. Resistance coefficient is larger if gas and liquid are injected mixed than that when gas and liquid are injected alternatively, and it changes greatly when oil saturation reach the25%boundary. Parallel core experiments result shows that foam have a strong profile control ability.Monotube core flood experiment indicates that foam flooding can raise8.5%oil recovery after water flooding which means foam can enhance oil recovery effectively.(4) Microscopic structure and movement mechanism of foam show that the formula is stable and good for heterogeneous reservoir;(5) Two typical steam stimulation wells have been designed and foam generation technics are all been recearched. The results achieved here have reference to Fengcheng Oil field.