Production Logging Tool Behavior in Two-Phase Inclined Flow

Abstract

Summary Production logging tools obtained from three service companies were tested in one-, two-, and three-phase flow in an inclinable flow test facility. These tests were inspired by the often confusing production logs obtained in deviated wells. The experiments have shown that two- phase flow regimes in inclined pipes differ markedly from those in vertical flow at similar flow rates and that these flow regimes adversely affect production logging tool responses. The experiments performed, the behavior of the production logging tools, and a statistical analysis of the data are discussed. Introduction Production logging tools obtained from three service companies were tested in one-, two-, and three-phase flow in an inclined flow test facility at Marathon Oil Co.'s Denver Research Center. Flow rates were chosen to simulate downhole conditions in producing wells in the McArthur River field, where production logging is used extensively. Liquid flow rates ranged from 70 to 3,400 B/D (11 to 540 m3/d) and gas rates ranged from 0 to 7.5 Mcf/D (0 to 210 m3 /d) during the tests. To simulate the wide range of well deviations in this off- shore field, the pipe angle also was varied from vertical to 60 degrees from vertical. Production logging tool responses were measured over this range of conditions to understand tool behavior and to try to correlate measurements with actual flow rates. Flow patterns observed in multiphase flow in an inclined pipe were found to affect production logging tool responses dramatically. In gas/liquid flow in a slanted pipe, slug flow was the predominant flow regime, whereas in oil/water two-phase flow. a stratified flow was common. In both cases. the lighter phase would move rapidly along the upper side of the pipe, establishing a circulating current that caused downflow along the lower side of the pipe. We repeatedly observed this pattern even though the net flow of all fluids was upward. Because of this nonuniform flow profile in multiphase flow in inclined wells, responses of production logging tools that measure localized quantities do not represent volumetric flow rates, average densities, or holdups. In this type of flow situation, spinner-type velocity tools often indicate reverse flow, especially when they are not centralized. Density and capacitance tools tend to be immersed primarily in the denser phase in a multiphase flow situation, preventing them from indicating average flow properties. Capacitance tools also exhibited nonlinear calibrations in static fluids, which makes their response suspect in a flowing stream. Flow concentrating flowmeters were the best tools tested for flow-rate measurements because they force most of the flow stream through a turbine inside the tools. A film made during the testing of production logging tools illustrates the profound effect of inclined, multiphase flow on these devices. A 5-minute videotape version of this film is available from SPE.* We used multivariate regression analysis to correlate the responses of two of the tool strings with the flow rates of each fluid and with the deviation angle. These correlations were used to predict the fluid flow rates from specific sets of tool response. Correlations obtained, however, were not sufficiently accurate for use in production logging interpretation. Improvements in tool design will be necessary before this technique can be applied to field interpretations. The technique does appear valid for tools that measure average fluid properties across the pipe. JPT P. 2432^

Investigation of Holdup and Pressure Drop Behavior for Oil-Water Flow in Vertical and Deviated Wells

“…The observations of Hill and Oolman (1982) confirmed that production logging tools usually provide accurate velocity, density, and holdup measurements at the point in the wellbore where the logging tool was placed. However, it was found that extrapolation of the measurements to the entire pipe diameter was not possible (Hill and Oolman, 1982;Flexhaug, 1983;Piers, 1987).…”

“…Several investigators (Curtis, 1967;Hill and Oolman, 1982;Flexhaug, 1983;Davarzani et al, 1985;Roesner et al, 1988;Hifl, 1990;Aguilera et al, 1991;Tabeling et al, 1991;Ding et al, 1992;and Halford et al, 1996) have reported the dominant effect of flow patterns over production logging tool responses.…”

“…However, the flow patterns observed under most two-phase flow conditions, particularly in deviated wellbores, sse, far from uniform and do not correspond to flow patterns found in vertical or horizontal flow (Hill and Oolman, 1982). If flow patterns could be predicted before running a production log, logging instruments could be selected and survey procedures could be tailored accordingly (Davarzani et al, 1985).…”

“…However, it was found that extrapolation of the measurements to the entire pipe diameter was not possible (Hill and Oolman, 1982;Flexhaug, 1983;Piers, 1987).…”

Oil/Water Flow Structure Measurements in Inclined Pipes

“…In order to compare the variations of Uwm and of the water flow-rate fraction xw with e:, we introduce a mean slip velocity: (1) where V 0 and V ware mean oil and water velocities defined by:…”