The Formation And Control Of Slug Flow In The Drainage Of Coalbed Methane

The slug flow is a common flow pattern in the gas-water two-phase flow,in recent years,more existences of the slug flow in the drainage of coalbed methane are discovered.The slug flow strongly intermittent and the pressure and instantaneous gas-liquid flow swing wildly,which can cause serious velocity sensitive damage to the reservoir,causing some coalbed methane wells of China high yielding in the preliminary stage and low yielding later or even halt production,so research about the formation and control of slug flow in the drainage of coalbed methane is of great significance.The influence factors about the formation of slug flow in the drainage of coalbed methane recovery were investigated with the laboratory experiment and the theoretical analysis.The results show that with the decrease of the surface tension of fracturing fluid,the increases of fracturing fluid viscosity,the decrease of the drawdown pressure,or the decrease of the coalbed methane reservoir permeability,the probability of slug flow are reduced and intensity weaken.And through the field application of two coalbed methane wells in some block in the central of China,it is verified that with the higher permeability,the slug flow will be stronger,The fracturing fluid with low surface tension can effectively inhibit the formation of slug flow and reduce the velocity sensitive damage.Accordingly these to put forward the control methods of the slug flow in the drainage of coalbed methane,using the triple-prevention fracturing fluid to stimulate the coalbed methane reservoir,drain more liquid in the stage of single-phase flow,reduce the initial water saturation of the gas-water two-phase flow stage.Minimize the pressure drop rate in the gas-water two-phase flow stage,reduce the rate of gas and liquid,adhere to the principle of continuous,slow and stable,so it can maximize inhibit the formation of slug flow and reduce its intensity.