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ABSTRACT The objective of the present work is to describe the main features of a Multiphase Flow Meter that TEA Sistemi designed and installed in an oil field where it was required to avoid the use of radioactive sources. This meter is based on the concept of isokinetic sampling of the multiphase mixture, combined with the use of a multiphase orifice and the pressure differential in a vertical tube. The most interesting result presented in this work is a correlation which allows the liquid hold-up in a vertical pipe to be derived from a differential pressure measurement rather than using an expensive and cumbersome radioactive source. In field application, the readings of this meter were in good agreement with overall production data. INTRODUCTION Over the last 25 years, the Oil Industry strongly supported the development of Multiphase Flow Meters (MFM), with significant investments in particular oriented towards subsea applications of this technology. Notwithstanding these efforts, the accuracy of MFMs has been and still is disappointing. To some extent, this is due to the complexity of the flow system and to a number of mechanical or physicochemical effects, such as solid deposition, erosion, corrosion, that alter the flow conditions inside the meter. On the other hand, the complexity of the flow system would suggest the development of "as simple as possible" MFMs, but often this is not the case. To give an example, the use of a radioactive source to measure the mixture density, requires a careful analysis of gamma ray attenuation through the pipe wall and the multiphase stream, introduces a number of potential errors and definitely represents a cumbersome device [1]. At the same time, it only provides an indirect measurement of the no-slip liquid volume fraction, based on some type of empirical equation of limited validity. A second example is the measurement of the water-cut. Quite often, in a MFM the water-cut is determined from the electrical impedance or the dielectric constant of the multiphase mixture. The electrical properties of a multiphase stream depend on the gas volume fraction and the composition of the liquid mixture. In particular, they depend on the transition from an oil continuous to a water continuous flow pattern and, when the water is the continuous phase, on the water salinity. However, the identification of this transition and the knowledge of the water salinity may represent additional problems in this type of measurements [1].
ABSTRACT MAST [1], a multiphase flow simulator has been validated against a set of laboratory and field data collected from recent R&D activities carried out by TEA Sistemi. A new set of measurements of pressure drops and liquid hold-ups taken at TEA Sistemi Laboratory under conditions of stratified gas-liquid flow has been used to improve the closure relations adopted in MAST. To verify the overall behaviour of the code, a set of field data (mainly pressure and temperature drops) has been selected from the available database. Based on MAST peculiarities (detailed description of slug flow and thin stratified film liquid flow with relevant entrainment), long tieback pipelines, characterized by large diameters, have been considered for validation purposes. The standard version of MAST, with default settings, has been used, and sensitivity studies have been carried out with regard to the numerical discretization and the adopted closure laws. Some statistical error analyses have been performed to evaluate the overall code accuracy. The results obtained showed good agreement between predicted and measured data (with average errors below 20%), which demonstrates that MAST can be used as an alternative tool for advanced flow assurance studies. INTRODUCTION Simulation of multi-phase flow in hydrocarbon transportation flow lines is typically carried out using transient one-dimensional flow simulators, among which OLGA [2] is the most widely used by the Oil & Gas industry. In OLGA, the closure laws, required within the framework of one-dimensional simulators, have been validated against the dataset gathered at the Sintef Multiphase flow laboratory [2]. For two-phase flows, six equations are globally solved: three mass conservations equations (for gas, liquid bulk and liquid droplets), two momentum equations (liquid bulk and a mixture equation for gas and liquid droplets) and one mixture energy equation. It is important to remark that the standard OLGA code can simulate the onset of liquid surges due for instance to terrain-induced slugging, but does not predict the flow structure of hydrodynamic slugging.
- Europe (0.47)
- North America > Canada (0.28)
ABSTRACT: In the exploitation of Oil/Gas fields it is common practice to transport the produced multiphase mixture with a single pipeline. The hydraulic design of these pipelines and the related flow assurance studies are based on the use of commercial codes which, in some cases, are also able to describe transient flow conditions (start-up, shut-down, etc.). The present work presents MAST, a transient one-dimensional multi-phase flow simulator. As explained in [1] all relevant flow patterns are described (stratified, slug, bubbly, annular) and, provided that a high spatial resolution is adopted (around some pipe diameters), the transitions among the flow regimes are predicted as fully dynamic processes governed by the conservation equations. This feature allows, for instance, the computation of slug length distribution along the pipeline and of the maximum slug length at the pipeline outlet. Various examples of the application of MAST to the analysis of field data are herein presented. It is shown that MAST permits a more accurate description of the flow structure. However, due to the fine mesh adopted, the CPU time performance can be poor, when the serial version of the code is considered. Nevertheless the explicit formulation of MAST allows the code to be easily cast in parallel form. In this work we show that a GPU application of MAST still based on a low cost PC allows a speed-up of up to two orders of magnitude over the serial version. This speed-up factor makes MAST faster than any commercial tool and allows this software to be applied to real-time monitoring and control systems
- Reservoir Description and Dynamics > Reservoir Simulation (1.00)
- Production and Well Operations > Well & Reservoir Surveillance and Monitoring > Production logging (1.00)
- Data Science & Engineering Analytics > Information Management and Systems (1.00)
- Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers > Pipeline transient behavior (0.89)
- Information Technology > Hardware (0.79)
- Information Technology > Graphics (0.61)
- Information Technology > Architecture > Real Time Systems (0.57)