Research on the Imaging Algorithm of Oil–Water Two-Phase Interface in Horizontal Wells Based on Arrayed Electrical Resistance Probes

In horizontal well oil–water two-phase production profile logging, water holdup is one of the important parameters for inverse calculation of the flowrate of each phase. Among the flow pattern in shale oil wells, stratified flow (SF) and SF with mixing at the interface (ST&MI) play a dominant role. SF and ST&MI are classified mainly based on the quantity of bubbles in the oil–water two-phase interface. A water holdup calculation approach based on an array of electrical resistance probes is presented to distinguish between SF and ST&MI and to increase the accuracy of water holdup calculations. In addition to a flow loop simulation device as the main tool, a single-arm array imager (SAI) was used to simulate and measure the oil–water two-phase flow in horizontal wells under different conditions of well deviation (85°, 88°, and 90°), flowrate, and water cut. The oil–water phase interface mixing phenomena is shown to be more likely to occur at the well deviation of 85° and 88° based on the experimental data. The holdup imaging effect of the oil–water interface is improved by a probabilistic reconstruction approach using the measurement data from each resistive probe, and the average water holdup is computed. The absolute error between the average water holdup calculated herein and the experimental shut-in water holdup is less than 0.16. To sum up, a good effect was achieved in applying the above algorithm to oil–water two-phase horizontal well.