The Research And Application Of Nitrogen Foam Conformance Treatments Optimal Design Method

After a long time of water flooding, most oil fields have entered into the high water cut period of development. The reservoir heterogeneity problems in vertical and horizontal resulted by long term water flooding have been increasingly serious, When high permeability zone is formed between the well pairs, a series of problems will appear, such as water breakthrough, invalid water flooding and scattered distribution of remaining oil. Because of limited by their mechanism and formation conditions, the effect of conventional water plugging and oil stabilizing is not very good, it is difficult to play a good profile control water in high water content area.Because of the high apparent viscosity, plugging high permeability reservoir of low oil saturation selectively, improving oil displacement efficiency by surfactant, and formatting nitrogen gas driving after the bubble bursting, we can improve the water injection situation by injecting nitrogen foam into reservoir, tapping the potential residual oil in the reservoir. Nitrogen foam profile control has superior characteristics of high security and maneuverability, simple process, low cost, high temperature resistance, no damage to the reservoir, water blocking and no oil blocking and other excellent properties, so it is a promising selective profile control technology.In the nitrogen foam profile control scheme implementation process, injection parameters have a direct influence on the final profile control effect and economic benefit. Therefore, effective measures should be taken to determine the injection parameters. Now the single factor analysis method is widely used in the oil field, it can quickly screen out the reasonable range of injection parameters or the best value. Without considering the interaction between various factors, the results are inconsistent with the actual situation, there are some defects in this method. Using experimental design method can fully consider the interaction among the factors, the design schemes have good operational excellency, it can achieve the desired purpose with a minimum of human, material and test times.This paper surveys the development history and present situation of the foam flooding at home and abroad, lists the typical nitrogen foam field application situation. And describes the composition of nitrogen foam, generation and burst mechanism as well as the nitrogen foam profile control mechanism detailedly.For Xidaliya reservoir contradictions of high water cut, tapping object becoming bad, increasing the difficulty of tapping the potential oil, this paper carries out the research of development effect evaluation and residual oil distribution, on this basis, choosed the reservoir and well group suitable for nitrogen foam profile control. Based on the history matching, researched the nitrogen foam injection method, injection opportunity, surfactant mass concentration, gas-liquid ratio and slug size. Determined the optimum range of injection parameters by using single factor analysis approach; Using DOE orthogonal experimental design method, obtain the regression equation of injection parameters and the cumulative oil increment, research the sensitivity of the effect of injection parameters on the cumulative oil increment by the multi factor analysis of variance.Using the response surface method get the curve relationship of injection parameters and the cumulative oil increment. According to the constraint condition of injection parameters, these parameters are reassociated to obtain the representative profile injection cases by using the orthogonal experimental design method, and the optimization method can make us achieve the best economic benefit combination of nitrogen foam profile control. Analysis the feasibility and risk resistance of the optimal combination method by the cash flow method and the uncertainty analysis method.