Jin Zhenwu,Guo Hairnin and Wu Xiling
Jianghan Petroleum Institute, Jiangling, Hubei, P.R. China
ABSTRACT
Fluid capacitance instrument can be used for distinguishing water from hydrocarbon in multiphase flows of production wells. However its response is usually affected by unsteady flow pattern as well as the salinity of water, , which causes difficulties for the accurate determination of water holdup (Yw). How to accurately obtain the value of water holdup (Yw) from fluid capacitance log is a key question in the production log interpretation of multi-phase flows.
Based on the geometry and principle of the fluid capacitance instrument, a new response equation of fluid capacitance, C, to water holdup, Yw, is presented in this paper. According to this equation, we can find that the relationship of fluid capacitance, C, to water holdup, Yw, is strongly dependent on the flow pattern and salinity of water in the sample chamber of instrument. For the multiphase flow with high salinity water production, the equation shows that the instrument will miss the ability to distinguish water from oil or gas when bubble flow occurs.
Log example given from Chinese oil field and experiment data given in this paper demonstrate the dependability of the equation, and also show some questions and limitations which should be noticed when determining water holdup, Yw.