Study On Gas Phase Measurement Methods Of Oil-Gas-Water Multiphase Flow In Petroleum Production Wells

Oil-gas-water multiphase flow is a common fluid with characteristics of multivariable random flow in the petroleum production logging.It is difficult to measure parameters of Oil-gas-water multiphase flow especially the gas holdup,but of great significance to improve oil well development efficiency,reasonably regulate oilfield development control scheme and reduce production risk.At present,probe and gas-liquid separation are common and effective methods for gas holdup measurement,but there are still some problems such as low measurement accuracy and poor real-time performance.Therefore,based on the actual development needs of Daqing,Huabei oilfields and others,this paper studies new technologies and methods of signal identifying and extracting,holdup measurement for gas phase based on probe and gas-liquid separation methods.Firstly,for the problem that current optical fiber probe sensor can not extract the gas phase signal accurately,the two-dimensional and three-dimensional theoretical analysis and Simulation of light transmission in the sensing head of optical fiber probe are carried out,and the intensity distribution law of the returned light at the bottom of the sensing head when the tip of the optical fiber sensing head contacts different media of oil,gas and water is obtained.According to this law,a New Dual-Receiving Fiber Optical Sensor(NDR-FOP)and gas holdup measurement method are proposed.The dynamic response of two receiving signals when NDR-FOP pierces the medium in oil-gas-water multiphase flow is analyzed.The sum and difference features of the two receiving signals are extracted and analyzed to verify the ability of NDR-FOP that can accurately extract the gas phase signal and holdup calculation.At the same time,aiming at the problem of low measurement efficiency of downhole probe sensor parameters,a fiber optical and conductive integrated sensor(FOCIS)is proposed.The structure and measurement principle of FOCIS are analyzed,and the simulation model is constructed.The dynamic response of FOCIS optical fiber and conductivity is analyzed.It is verified that FOCIS can realize gas phase and water phase signal acquisition at the same time.Secondly,in order to measure the gas holdup of oil-gas-water multiphase flow,a Novel Dual Receiver Fiber-optic Probe Array Multi-phase Logging Tool(NDRFOPA＿MLT)based on four NDR-FOP is designed.The measurement principle and method of local and sectional void fraction of oil-gas-water multiphase flow based on optical fiber probe method are studied.The gas phase distribution laws of oil-gas-water multiphase flow with different working conditions are simulated and analyzed.According to the law,a herringbone four NDR-FOP array structure is designed,and three-dimensional simulation model of NDRFOP＿MLT is constructed,the spatial sensitivity of NDRFOP＿MLT is discussed,the response characteristics of NDRFOP＿MLT by dynamic simulations are analyzed,and the dynamic simulation data of NDRFOPA＿MLT are calculated by k-means algorithm to verify the feasibility of measuring the gas holdup in oil-gas-water multiphase flow.In addition,based on the above analysis,a fiber conduct combined probe array multi phase logging tool(FCCPA＿MLT)with a "herringbone" four FOCIS array structure is designed.The gas and water phase signals under dynamic simulation are analyzed to verify the FCCPA＿MLT can analyze and measure gas and water content at the same time.Thirdly,to realize automatical analysis and measurement of gas phase of oil production wells and meet the requirements of digital oilfield that intelligent fluid parameters measurement at the wellhead,a new wellhead fluid parameter test equipment based on gas-liquid separation(YDJKI-1 and YDJKI-2 surface wellhead test equipment)is designed and analyzed from structure,working mode,software and hardware system.A gas phase measurement method based on gravity and liquid level monitoring is proposed,the separation principle of each phase in the gas-liquid separation process is discussed theoretically,the key parameters of the gas-liquid separation chamber are analyzed and calculated by three-dimensional simulation,and the gas-liquid separation effect is verified by comparing the water content with oil-water two phase flow.Finally,prototype development,experimental platform construction and experimental result analysis are carried out successively for NDR-FOP,FOCIS,NDRFOPA＿MLT,FCCPA＿MLT,YDJKI-1 and YDJKI-2 surface wellhead test equipment.The realization of identifing and extracting accurately the gas phase signal of oil-gas-water multiphase flow under various working conditions for NDR-FOP is analyzed and verified,FOCIS can collect gas phase and water phase signals at the same time;the realization of gas holdup measurement in oil-gas-water multiphase flow for NDRFOPA＿MLT and measurement of gas content and water content for FOCIS＿MLT are analyzed and verified;the realization of gas-liquid separation and gas metering in applicable range of working conditions is analyzed and verified for YDJKI-1 and YDJKI-2 surface wellhead test equipment...