Local Flow Characteristics In Oil-in-water Two-phase Flow Pattern At Low Velocity

Oil-water two-phase flow widely exists in the process of oil production. The flowcharacteristics of oil-water two-phase flow are of great significance to understandingoil well production performance and optimizing oil reservoir management. However,due to the complicated flow structure as well as the complex motion in the interfacebetween the oil and water phases, it caused a certain degree of difficulty to measureflow parameters.Based on research methods of flow characteristics home and abroad, we start tomeasure the local flow characteristics of vertical oil-in-water flow pattern, optimizethe design of the5-channel conductance dual-probe array sensor and conduct adynamic experiment in oil-water two-phase flow loop test facility. The total flow raterange is from0.5m3/day to6m3/day, and the water-cut range is from80%to98%.Three typical oil-in-water flow patterns are observed including oil slug flow, bubblyflow and very fine bubbly flow. The local oil holdup, local fluid velocity and localbubble diameter at each probe are extracted. The innovative points of this study are asfollows:1. The design of conductance dual-probe array sensor is optimized from the viewsof electric field and flow field respectively. The optimal interval between left and right,and the distance between front and back for the dual-sensor are determined. Dynamicresults indicate that the sensor designed is valid for the measurement of localcharacteristics in vertical oil-in-water flows.2. Based on the fluctuating signals of conductance dual-probe array sensor, theself-adjusting double threshold method can effectively calculate the local holdup; thelocal fluid velocity of dispersed phase at each sensor is extracted by using cross-correlation velocity algorithm and then the local transient bubble diameter distributionis measured, which provides a feasible way to reveal the bubble-group structurecharacteristics of oil-in-water flow patterns.3. Local holdup at different positions in the cross-section of pipe is extracted byusing the numerical simulation of computational fluid dynamics. The calculatedholdup results relatively coincide with the local holdup measured from5-channelconductance dual-probe array sensor. It demonstrates that the numerical simulation method can provide an effective and auxiliary tool to study the flow characteristics ofoil-water two-phase flow.