Study On Flow Measurement Technology Of Oil-water Two-phase Flow In Downhole Producing Profile

Oil-water two-phase flow is one of the main forms of the downhole fluid field,the parameter monitoring of which is an important research method to master thedownhole fluid flow, improve the production logging technology and ensure therational development of resource. It is significant to measure the downholeproducing profile for judging the different content of each phase in oilfield,detecting oil distribution and exploring oil accurately. However, producing profileflow measurement is faced with the problem about measuring each phase inoil-water two-phase flow and distinguishing the flow distribution of different layersin hostile underground environment.Through receiving the flow signal with FBG strain and converting the signal tothe center wavelength variation of FBG, single-phase fiber optical flowmeter wasdesigned in this paper, which is based on the principle of optical fiber sensing andtarget type structure. Using the homogeneous model, the mixed flow and phaseholdup measurement theory of oil-water two-phase flow was established. In view ofthe flow measurement of downhole producing profile, the relationship betweendifferent producing layers was built up on the basis of the wellbore flowcharacteristics, which was regarded as the theoretical foundation of flowmeasurement between different producing layers.Flowmeters were designed according to single-phase and two-phase flowmeasurement theories. Single-phase optical fiber flowmeter was designed bycontrasting two different structures, FLUENT simulation was adopted to optimizestructure and analyze fluid field. Optical fiber sensitive element was designed todetermine the relationship between FBG strain and measured flow, through whichthe performance parameters of optical fiber flowmeter were analyzed. Oil-watertwo-phase combined flowmeter was designed on the basis of the structuretransformation on single-phase flowmeter and the introduction of conductancesensor, which is used to measure phase holdup. The impact on performance ofcombined flowmeter from mixed flow and phase holdup was analyzed by FLUENTsimulation. On the oilfield factual condition of producing profile logging, flowmeasurement general planning of producing profile was put forward, the spatialresolution was determined to be20m, installation program of flowmeter wereproposed, which included temperature compensation of optical fiber. Flowcirculation laboratory bench was built to establish producing profile flowmeasurement system, which was used to carry out flowmeter calibration experiment.By comparing the experimental results to simulation data, the correctness of theorymodel was verified. From the experimental analysis, within the flow range0~55m3/d, flow resolution was1.3m3/d，water holdup resolution was3.5%, whichmet the requirement of flow measurement in downhole producing profile.