Study On Oil Water Gas Phase Fraction Measurement Using Low Energy Radiation

Multiphase flows are common in the petroleum industry, and it is related to oil extraction, transportation and refining processes. It is important to measure oil water and gas volume fractons for monitoring oil well, predicating oil reserves, optimizing oil extraction methods and managing oil production. The fact is that there are many different flow regimes in the pipe flow and the mixtures's temperature and salinity are contantly change at the same time, so it's always a difficult problem to measure oil water and gas volume frations.This paper studies on the oil, water and gas volume fraction measurement based on low energy radiation which less than 100keV. The phase fraction of crude oil measured by dual energies radiation transmission methods and single energy radiation transmission and scattering methods. The flow pattern recognition of gas-liquid two-phase flow in vertical pipe was studied by measuring gamma-ray scattering spectrum. The result of the flow recognition was used to compensate the effects of the flow pattern on the gas phase volume fraction measurement of dual energies radiation method.The paper introduces the models of oil, water and gas volume phase fraction using radiation method. In order to optimize system design, the particle transport process for oil, water and gas volume phase fraction measurement were simulated by using Monte Carlo method. The sensitivity and statistical errors with radiation energies were researched by the simulation software, and it found that low energy gamma-ray has high sensitivity for oil and water medium. So the dual energies radiation source is compose of 238Pu and 241Am isotope and single energy radiation source choices 241Am isotope by taking into the source's half-life. In order to determine scattering detector position, the energies distribution of scattering ray with the scattering detector location were studied. The results show that the scattering detector can reflect the fluid state of pipeline when it located on source-transmission detector vertical position. The effects of temperature, pressure and oil contents change on water volume fraction measurement of dehydrated oil were analysed. The compensation algorithms for temperature and oil content change were found. The errors of gas volume fraction caused by the flow pattern were correctted by the scattering ray energy spectrum for the dual energies radiation. The scattering ray energy probability distribution of the homogeneous mixed flow, annular flow and slug flow in vertical pipeline were obtained by simulation method. The flow patterns were identified by RBF neural network using simulation data. The results show that the homogeneous mixing flow and annular flow can be completely seperated. The effects of annular flow on gas volume fraction can be corrected by the compensation algorithm. The phase fraction of gamma-ray tansmission and scattering method were predicted by RBF neural network. The precision of phase fraction were increased comparison with dual energies algorithm.The oil, water and gas measurement system were setup. The measuring device mechanical structure was designed according to the radiation source and detector's specifications. The pusle shaping amplifier circuit for detector output and the computer counting cards were designed. The precise timing codes were developed by using windows driver model. The efftect of timing error on phase volume fration measurement can be reduced. The computer was used for the data acquiring and processing.The experiments for the dual energies ray method, single energy gamma ray transmission and scattering method and low water content crude oil measurement were implemented in the measuring device. The experimental results show that the maxinum absolute error of water cut is less than 0.01 and the maxinum absolute error of gas volume fraction is less than 0.01 by using dual energies ray method; The maxinum absolute error of water cut is 0.04 and the maxinum absolute error of gas volume fraction is 0.02 by using the single energy gamma-ray transmission and scattering method; The precision of of water volume fraction for low water content crude oil has been improved when using dual energies ray. The effects of temperature and oil composition changing on low water content crude oil can be compensated by some algorithms and the maxinum absolute error of water volume fraction is less than 0.002.