Research Of Water Holdup Measurement Method Based On Resistance And Array Tool Development

In crude oil extraction process,the water holdup of fluid in well is an important evaluation parameter.In view of the actual situation that a large partial of oil wells have the characters of high water content,low yield and large incline in China,it is of great engineering significance to develop array logging tool based on resistance,which is suitable for water holdup measurement in high water content oil well.Aimed at the detection of water holdup in high water content and low yield oil wells,the following research works are carried out in this paper:1.According to the character of oil-water being separated in low yield oil wells,a method based on tested local fluid resistance to determine fluid properties was used,a basic scheme to detect the local water holdup was proposed,which is based on the statistical results of local fluid properties in unit time.2.In order to measure the resistance of the fluid relatively accurately and minimize the influence of the double layer capacitor and distributed capacitor,the equivalent electrical model of the resistance sensor was analyzed.The results show that for the probe resistance sensor,(1)Under the condition of bipolar pulse stimulating with 10 kHz frequency,the distributed capacitor has been charged and reachs a steady state after 10 us of the pulse jump.At the middle time of the pulse duration,the voltage on the double layer capacitor is zero,which is the best time to measure the resistance of the fluid;(2)Under the condition of sinusoidal signal stimulating with an appropriate frequency,the reactance of double layer capacitor will not affect the discrimination of the fluid properties.The impedance and phase of the sensor equivalent parallel model,which is composed of fluid resistance and distributed capacitor,can be calculated with DFT to the current flowing through the sensor,finally gets the fluid resistance value.3.The overall design scheme of the tool was proposed.The scheme adopts probe resistance sensors to form an arrayed detection structure,which can obtain the distribution information of the fluid resistance on the oil well cross section;Two sets of fluid resistance detection circuits was developed,which are respecting the bipolar pulse excitation circuit for detecting both the voltage and current of the sensor,and the sinusoidal signal excitation circuit based on the AD5933 impedance measurement chip.4.The relevant water holdup measurement experiments have been carried out on the experiment device,which simulates oil-water two phase bubbly flow well.The experiment results show that:(1)The statistical histogram of detected fluid resistance shows a polarized distribution.The higher degree of mineralization,the greater the dispersion.(2)Two kinds of fluid resistance detection schemes can well distinguish the properties of liquids.5.A method of determining the property of the fluid with double thresholds was presented.The water holdup,which is estimated by counting the proportion of water samples to the total number of oil and water samples in unit time,can well reflect the change of water content,so the method is useful to estimate water holdup,and the effect of salinity can be easily corrected by adjusting the thresholds.In conclusion,the results of this paper have an important reference value for the development of array water holdup tool based on resistance measurement.