Research On Lag Time Of Mudlogging Based On Calcium Carbide Method

The measured lag time is the key to ensure the quality of cuttings,accurately recover the strata profile of downhole,implement the well section of oil and gas show,accurately calculate the uplifting height and uplifting velocity of oil and gas,and correct the diffusible gas formation.The calculation of the measured lag time is simple and easy to use.However,there are still several major problems.In unconventional mud logging,such as extended reach wells and horizontal wells,the representativeness of cuttings is poor and the actual lag time is not accurate.In complex drilling conditions,hesitation pumping,a number of mud pump is not synchronized circulated,the lag time can not be measured.Therefore,based on the in-depth study of two-phase flow characteristics,influencing factors,and a large number of laboratory experiments and investigations,this paper starts with changing the measured lag time markers and proposes the scheme of using calcium carbide instead of plastic beads as markers.Based on the feature of two-phase flow,this paper has established a drift-flux model for wellbores,which is easy,continuous and flow pattern included.On the basis of the force and shape analysis of the gasthe calculation formula of the measured lag time is deduced based on the data recorded by the mud logging system.After tackling the formation of technical achievements,including the following aspects:1.Describe the definition of lag time and the importance to mudlogging job,give the theoretical and practical methods of lag time,analyze the factors affecting the lag time.2.The use of logging gas chromatography data logging function,compare the advantages and disadvantages of calcium carbide and plastic pellets,so that the determination of the late time documents can be submitted as completion information.3.Through simulation experiments,the flow characteristics and influencing factors of acetylene gas in mud are analyzed,and the mathematical model of acetylene gas flow in wellbore is established.4.Briefly describe the working principle of the chromatograph and solve the problems with the actual lag time of acetylene.5 Accurately calculate the volume of the annulus and give an improved method combining the theory of late arrival time and actual measurement.