An experimental study used pulsed ultrasonic Doppler techniques to determine fluid velocities in two-phase oil-water vertical pipe flow.· The data acquisition system was based on a medical ultrasound instrument, modified as needed, and a microcomputer. Measurements were made in a pipe with an inside diameter of7.25 in. [18.4 cm], part of the Multiphase Flow Loop in the Department of Petroleum Engineering at The University of Texas at Austin. This pipe is 42 ft [12.8 m] long and can be inclined at any angle. The ultrasonic measurements gave reasonable qualitative results in all regimes of which the flow facility is capable: the Doppler frequency was generally proportional to the phase velocities. More theoretical and experimental work is needed, though, to improve the quantitative accuracy and to increase the measurement range: measured velocities were generally too low, and the range limit is estimated to be approximately 6 to 12 cm into the flow, depending on the regime. Backflow is measured on the low side when the pipe is inclined from the vertical.
This paper presents the first results of an experimental and theoretical investigation of the feasibility of using ultrasonic measurements in multiphase pipe flow. Extant downhole flow rate measurement technology used in the petroleum industry is not adequate in some multiphase flow regimes, particularly when the well is deviated from vertical. Ultrasonics offers Doppler velocity and imaging capabilities, both of which could be of great value in production logging. Some air-water measurements, both imaging and velocimetry, are presented, along with a discussion of pulsed Doppler theory.
An experimental research program has been initiated to investigate the electrical properties of swelling shales across a wide frequency ranee, 10 Hz to 1.3 GHz. This range spans the spectrum of the commonly used downhole logging, measurements, from the deep laterologs to the microwave dielectric tools. Three distinct measurement techniques have been utilized to span the range: multiple electrodes at low frequencies, two-electrode with balanced bridge for the middle frequencies, and open-ended coaxial probe with network analyzer at the high end. The probe technique is simple to use, potentially enabling, field measurements of complex permittivity to be taken, although some accuracy is sacrificed. The effects of swelling, are most pronounced at the lowest frequencies. The weight of a shale which has been exposed to a change in relative humidity reaches equilibrium long before the electrical properties do. Introduction Anomalously low resistivity-log response in certain formations has been known to yield incorrect water saturation and to sometimes mask detection of hydrocarbon-bearing intervals. Shale, which is often the cause of the problem because of its clay content, may be in the form of laminations or grains, both detrital in origin. The interpretation problem is one of choosing the appropriate mixing rule based on both the C, distribution of the shale and the volume investigated by the C, logging measurement. An understanding, of the electrical properties of the shale itself is an important element of the problem. For example, complex permittivity can be used in model based on a volumetrically weighted mixing rule to interpret microwave-frequency measurements. In a shaly formation, these complex time average models require values for the complex permittivity of the shale. High resolution dielectric logging measurements may be able to detect individual shale laminae if they are thick enough, in which case the shale's properties must be accounted for in the interpretation. The electrical properties of massive shales are also of interest to the industry. The alteration of shales, caused by adsorption of water while drilling, is a problem which has acquired a logging perspective due to the increasing use of measurement while drilling. The capability of making real time and time-lapse measurements while still drilling introduces the possibility of detecting a swelling problem while something can still be done about it. Improved interpretation in both of these cases requires an understanding of the effect of the shale's composition, texture, chemistry, and water content on tool response. In particular, the effect on electrical measurements can be quite large. The availability of tools operating over a wide range of frequencies is of possible benefit since the mechanisms affecting the propagation of an electromagnetic wave differ with frequencies. Logging measurements at frequencies from 35 Hz to 1.1 GHz are commercially available. P. 131^
ABSTRAC T The transition from stratified to slug flow in gas-liquid horizontal flow was studied in 6.35 cm and 18.4 cm ID pipes for a wide range of air and water flow rates by video-recording the flow field and by ultrasonic measurement of the location of the air-water interface. The ultrasonic imaging techniques provided an accurate means of monitoring the liquid depth and wave characteristics in stratified flows. The experimental results were checked with theoretical models of flow regime transitions, which showed that the Taitel-Dukler model1 of the stratified to intermittent flow transition gave a reasonable prediction, particularly in the small pipe. In the large pipe, stratified flow occurred for all conditions tested. INTRODUCTION We have been investigating the application of ultrasonic velocimetry to the measurement of volumetric flow rates in gas-liquid flow from deep, subsea wells. In this application, it would be advantageous to locate the measurement system in the subsea pipeline near the wellhead. Our preliminary results show that the efficacy of ultrasonic velocimetry in two-phase flow depends on the flow regime, with stratified flow being a preferred measurement environment compared with intermittent flow. Thus, we are interested in gas-liquid flow regime behavior in large pipes near the pipe entrance. This paper presents the results of a laboratory investigation of the conditions leading to the transition from stratified to slug flow in gas-liquid, horizontal flow. The results were tested with the theoretical model of Taitel and Dukler and the empirical flow regime map of Mandhane et al.2 For the 6.35 cm ID pipe, reasonable predictions of the stratified to intermittent flow transition were obtained with both of these methods. For the 18.4 cm ID pipe, both methods predicted intermittent flow to occur for some of the conditions tested, while stratified flow was observed in all cases. Previous work has demonstrated the applicability of ultrasonic imaging and velocimetry to the metering of upwards two-phase flow in vertical or inclined pipe.3 In this study we extended these techniques to horizontal gas-liquid two phase flow. It was found that the ultrasonic imaging techniques provide a means of accurately measuring the distribution of the phases in horizontal gas/liquid flow. A clear picture of the water-air interface and many of the wave characteristics, such as wave amplitude and wave frequency, can be easily obtained from the ultrasound signals. By measuring the wave velocity from the video-recordings of the flows, the wave length can also be obtained. EXPERIMENTAL APPARATUS Flow Loop Experiments were performed using a flow loop consisting of a pipeline of 6.35 cm ID and a pipeline of 18.4 cm ID (Fig. 1). Both pipes are 12.8 m long and are clear, so flow can be observed visually. Water and air are conducted to the flow loop separately through two hoses. By changing the connections between the hoses and the pipelines, either or both of the fluids can be conducted into one pipe and be exhausted from the other. In this way, flows with different flowing directions can be studied.
Muhammad Razi,* Steven L. Morriss,* and Augusto L. Podio* Abstract The flow velocity of the one dimensional, single phase flow within an individual perforation is determined using an ultrasonic Doppler technique. This new technique takes advantage of the fact that flow in an individual perforation is often single phase even when flow in the wellbore is not. Existing techniques for determining multi-phase flow rates in a well bore have many limitations, due in large part to the complexity of the many possible flow regimes. An innovative approach which partially circumvents this problem has been investigated experimentally. Work has been done using an experimental set-up simulating a well bore, with water as the fluid. Since the diameter of perforations for a known gun type and casing can be reasonably estimated, flow rate within an individual perforation can be determined from velocity. Comparison of the calculated flow rates with actual flow rates are encouraging, both in turbulent and laminar flows. It is envisioned that a televiewer-like tool could be developed to scan the entire perforated interval while logging, providing a complete description of flow entries and exits. Introduction Most oil and gas wells are completed by cementing steel casing in the well and then perforating the casing in the zones of interest, Laboratory studies indicate that crushing and compaction of rock during perforating reduce the flow capacity of the perforation. Productivity of a perforated completion may range from 5% to 90% of undamaged, open hole productivity. This results in a significant loss of production of oil and gas, and hence revenue. In injector wells, whether used for enhanced recovery or for waste disposal, poorly performing perforations are likewise undesirable. Locating the ineffective perforations requires a reliable method for determining the flow through individual perforations. Many shortcomings and operational complications are associated with the use of present production logging techniques such as spinners, and radioactive tracers. The use of ultrasound for this purpose may be a good alternative. Since the only contact between the tool and fluid is sound waves, the flow stream in a perforation or the wellbore is not disturbed during the measurement. Also shortcomings associated with the use of mechanical tools, such as threshold speeds of spinners, are not present. The research reported here proposes to measure the flow in individual perforations as suggested in Fig. 1, providing the operator with a quantitative measure of perforation performance. Since downhole ultrasonic logging tools are available commercially to scan the inner wall of the hole for imaging purpose, only additional signal processing would be required to implement Doppler velocimetry. DOPPLER THEORY The exploitation of the Doppler effect is as old as the history of bats and dolphins since they exploit this phenomenon as a basic survival skill. The early investigation of this phenomenon was done by Christian Andreas Doppler, hence the effect is named after him. The Doppler effect is commonly exploited for medical purposes where it is used to measure blood flow. In the upstream petroleum industry, production logging applications based on Doppler ultrasound are still in the research stage, with the first reported work done in 1990. P. 943
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