Design and optimization of the fiber-optic probe array for measuring gas holdup in oil-gas-water multiphase flow

The exploitation of the mainland oilfield has entered a middle-late stage with high water-cut currently, and oil–gas–water multiphase flow exists commonly in exploitation of oilfield, accurate measurement of gas content has become a complex problem for the actual demand of dynamic monitoring in oil and gas field exploitation. In order to solve the problem of gas holdup measurement of the oil-gas-water multiphase flow in the oil-producing wells, this paper first constructed the mechanism model of a fiber-optic probe (FOP) for gas holdup measurement, and theoretically analyzed the feasibility of FOP to measure the gas holdup; simultaneously, the distribution characteristics of gas holdup for the upward oil-gas-water multiphase flow in a vertical pipe were simulated and analyzed by the FLUENT software; then the response characteristics of FOP piercing a gas bubble at different positions and different angles were analyzed. Secondly, the optimal structure of the fiber-optic probe array (FOPA) was optimized by analyzing the performance indexes of the ability to capture the cross-section gas holdup and the effect on the fluid flow interference. Finally, we designed and developed a FOPA-based logging instrument which could be applied to the complex environment of the oil-producing wells with high temperature, high pressure and narrow space. By the dynamic experiments carried out on the experimental facility of oil-gas-water multiphase flow and the onsite experiments carried out in Daqing Oilfield, the feasibility for the FOPA-based logging instrument to measure gas holdup was analyzed and verified.