Effect Of Temperature And Humidity Field On Fluid Physical Properties And Wellbore Flow In Gas Drilling

It is of great importance to study gas drilling wellbore flow for gas injection rate and pressure design,and also very important for prediction of gas carrying cuttings and formation water production during drilling process.However,the current wellbore flow calculation models were not involved with the influence of wellbore temperature and humidity on the physical properties of the circulating fluid and the flow of the wellbore,and didn't consider the interaction and influence of pressure distribution,temperature distribution and humidity distribution in the wellbore.Therefore,in order to study the effect of wellbore temperature and humidity field on fluid physical properties and wellbore flow in gas drilling,the following researches were carried out:(1)The basic theories of flow,heat transfer and humidity of wellbore in gas drilling were analyzed,the calculation methods of the physical parameters and the flow parameters of the fluid in the drill string and the annulus were defined,the analytical formulas of temperature distribution of the fluid in the drill string and annulus were deduced,and the calculation methods of temperature and humidity field in the drill string and the annulus were defined.(2)The effects of temperature and humidity on fluid physical properties and flow parameters were researched.The wellbore temperature and humidity were considered to correct the circulating fluid physical properties.The interaction and influence of pressure distribution,temperature distribution and humidity distribution in the wellbore were considered to establish a coupled model of wellbore fluid flow with temperature and humidity during gas drilling.A MathCAD program was written to solve the model,the wellbore flow calculation Visual Basic program and calculation modules were compiled.(3)Based on the MathCAD program and the VB calculation modules,wellbore flow during gas drilling was calculated and analysed.Combined with the MMWD drilling data of YL29 well,the accuracy of the model was verified.The wellbore pressure distribution,temperature distribution and humidity distribution during air,nitrogen and air mist drilling were researched,when the formation water were not produced or micro produced.(4)Based on the VB calculation modules,the influence factors of the wellbore humidity distribution in gas drilling were calculated and analysed.The influences of ambient temperature on the relative humidity and absolute humidity of the annular return gas were researched,a new idea of monitoring the formation water production was explored.The coupled model of wellbore fluid flow with temperature and humidity during air,nitrogen and air mist drilling,can be used to calculate the wellbore flow parameters,wellbore temperature and humidity distribution,when the formation water were not produced or micro produced.The presented new idea of monitoring the formation water production and the absolute humidity monitoring system,may have certain research prospect and value in the field of on-site humidity monitoring and formation water production assessment.