Study On The Law Of Foam Water Shutoff And Its Applicability

Water breakthrough in oil well is an inevitable problem in the process of oil field exploitation,it influences oil well's output.Water shutoff technology is the key of controlling water and keeping stable oil.Because foam fluid is stable when it meets water,defoam when it meets oil,it has a good select sealing characteristics for filtering layer and little harm for layer and so on,it is used into precipitation increase oil production technology in oil field more and more in recent years,and gets good application effect.However,present studies on foam sealing characteristics at home and abroad mainly focus on advocating one-dimensional core displacement and two-dimensional core displacement and other method to simulate the situation of reservoir displacement,which has some certain limitations.Therefore,it is necessary to use three-dimensional core to study on the horizontal and vertical sweep efficiency.First of all,this text made an overall evaluation on SD-type foaming properties of the oil field,the research showed that the optimum using concentration of SD-type foaming properties is 1.0%,then it made a selection of two kinds of filter foam stability of polymers,the result showed that sea-water dissolving polymers in concentration of 0.1% has better foam stability.So it selected out foam water shutoff agent system which is “SD-type foaming properties of 1.0% + sea-water dissolving polymers of 0.1%”.Then,It advocated three--dimensional non-homogeneous to suppress core to make experiment of water shutoff regulation,comprehensively considered the sweep efficiency and displacement efficiency of plane and vertical direction,it also studied technological parameter of effect of foam water shutoff.Finally,it studied on the applicability of foam water shutoff by the way of numerical simulation.The result shows: when the extreme deviation of formation permeability is smaller than 10 times,injecting foam system to shutoff water can improve recovery percentage about 22%-25%,when the extreme deviation is too big,it is easy to cause water channeling,the effect of foam water shutoff will decrease;the quality of foam from gas-liquid mixed note is better than slug injection,it has better effect on water shutoff of oil well;as the increasing of gas-liquid ratio,the sealing characteristic of foam gets stronger and stronger.For three-layer non-heterogeneity cores,the best gas-liquid ratio is 1:1-2:1,the sealing characteristic of foam increases first and then decreases with the increasing of plugging additive content.Slug volume between 0.3 and 0.5PV has a better water shutoff effect,and the using effect of uniform concentration slugs is better than non-uniform concentration slugs;when the oil well's water cut is between 80% to 90%,foam water shutoff agent can plug the water channeling and control water breakthrough from oil well;as the increasing of crude oil viscosity,crude oil's liquidity turns worse,which produces a disadvantageous influence on the effect of foam water shutoff.When the crude oil's viscosity is less than 100 mPa·s,foam water shutoff agent plugs water layer clearly,when the viscosity of crude oil is too high,we should decrease its viscosity first and then use foam water shutoff agent to shutoff water.The numerical results is same to the results of laboratory experiments,they are in line with a high degree,the paper obtained the gas-liquid chart of foam water shutoff rule and amount of nitrogen injected chart,it provides assistance to the application of oil field.