Research On The Technology Of Controlling Drilling Fluid Invasion By Downhole Fluid Spectrum

With the development of oil and gas field to deep complex stratum,the problem of complex downhole accidents caused by formation fluid intrusion becomes more and more serious in drilling construction.Because of gas compressibility,invasion of wellbore gas with the expansion of the drilling fluid migration will produce sharp,greatly increased the difficulty of control,as a result,the fluid invasion risk mainly concentrated in the gas leaking.The monitoring and control of fluid intrusion is the technical bottleneck to achieve the goal of wellbore integrity control in the whole drilling process.Downhole formation fluid near infrared spectrum monitoring technology,can provide real and effective for drilling construction of underground gas speed and amount of intrusion information,down-hole spectra can be measured gas cut situation to the pressure distribution along the wellbore,a powerful reason to control fluid invasion.Control pressure drilling technology can realize the wellbore pressure control in the process of drilling,domestic drilling in recent years made great development in the construction application,and can realize accurate control of wellhead back pressure and circulating mud displacement,has provided the safeguard for accurate control of fluid invasion.Based on the extensive investigation and research theory of formation fluid invasion monitoring and control technology at home and abroad on the basis of the use of downhole fluid spectroscopy detecting underground,gas flow analysis and calculation of multiphase flow model is established,the use of downhole measurement inversion gas wellbore pressure distribution,combining with the control pressure drilling technology theory and construction technology,the monitoring and control technology of invasion to the fluid to the research of the system.The gas intrusion measured by downhole fluid spectra is inversed to the pressure distribution along the wellbore,which provides a primary monitoring basis for the wellbore pressure control.The multiphase flow analysis model and the control parameter calculation model of safe drilling after fluid intrusion are established.Gas-bearing formation fluid invades borehole in the construction process,according to the spectral measurement of downhole fluid wellhead back pressure control model is used to calculate gas wellhead back pressure control required,under the condition of normal mud displacement,will invade the gas out of wellbore,and prevent formation gas invasion,further realizes the control pressure drilling gas cut control and safety drilling;Under the condition of the already set back pressure control,according to the spectral measurement of downhole fluid mud circulation control model is used to calculate gas circulating mud displacement,maintain the bottom hole pressure in the safe density window,and penetrated to the gas discharge within the wellbore,and prevent formation gas invasion,further realizes the control pressure drilling gas cut control and safety drilling.This paper puts forward a set of downhole drilling fluid spectrum gas-bearing formation fluid invasion in the process of monitoring and control technology,design a set of fluid invasion of real-time monitoring and control system,developed a fluid invasion of real-time monitoring and control software.The software can monitor downhole fluid intrusion,calculate relevant control parameters,and provide accurate and effective control parameters.Well application according to the experiment results show that the software can realize real time monitoring of downhole fluid invasion precise calculation of underground fluid spectra measured the required gas wellhead back pressure control and the circulating mud displacement,through accurate control wellhead back pressure and circulating mud displacement,to prevent further formation gas invading wellbore,realize the monitoring and control of the formation fluid invasion,monitoring and control situation is consistent with the actual situation,monitoring and control effect is good.The software to make up for the inadequacy of downhole fluid spectrum measuring instrument data applications,friendly interface,high precision,good stability,can better realize the gas-bearing formation fluid invasion of real-time monitoring and control.