Objective
The project was executed from 1982 to 1985. The main object of this project was to develop a specific calculation method for gas and liquids polyphasic flows in tubing which equip crude or condensate gas wells as well as in production risers used offshore.
A new method for predicting pressure losses in these vertical or very inclined pipes seem indeed necessary, owing to :
- the lack of precision of traditional calculation methods, based mostly on correlations that cannot be extrapolated to difficult operating conditions which are more frequent.
- the need for precise evaluations, namely for offshore production, of quantities of hydrocarbons likely to be extracted from different wells within one field, whether eruptive or being pumped, so to set-up serious and credible technical and financial forecasts concerning the volume of the overall production, then to optimize the pipes and the bottom and surface equipment.
Results obtained within the scope of this project were restricted for the quantitative elements to the diphasic flows of gas and oil. They could not be applied without reserve in the very frequent case of water producing wells. The preliminary study on triphasic flows that had been carried out did not allow to conclude on the possibility of modelling in the same manner the diphasic and triphasic flows.
The results were nevertheless exploited at the end of the following study which alllowed to develop the modelling of triphasic flows and to finalize a model which represented with similar accuracy both situations. This model was incorporated in a general computing programme for polyphasic flows in eruptive wells or gas-lift wells called WELLSIM (well simulation). This programme which includes the results of the diphasic study has been tested and compared to the traditional methods of Aziz-Govier, Hagedorn-Brown, Orkizewski, Ros, on data provided by 90 eruptive or gas-lift wells, among which more than half presented a water/oil ratio that was nil.
With WELLSIM the mean error is more or less 1% and the standard deviation 12%, whereas the best traditional method provides a mean error of more than 9% with a standard deviation of 19%. The obtained accuracy was thus about two times better than that of the traditional methods.
This project followed the study on diphasic flows in horizontal or slightly inclined pipes. (Contract EEC/GERTH nr TH 03080/79), which ended in 1981 in the finalization of a calculation method called PEPITE. Thanks to this experience, the project team was able to apply the same experimental methodology and the same theoretical approach, although vertical or highly inclined diphasic flows are different and more complex to study.
The project was divided in two main phases :
- STUDY OF OIL-GAS DIPHASIC FLOWS
This most important part resided on experiments carried out under representative oil industry conditions on the vertical diphasic flow test loop of Boussens. This loop consisted of two test pipes of a diameter of 3" and 6" respectively, presenting an effective length of 25 m, and allowing to measure the main characteristics of the oil/gas diphasic flow up to velocities of about 20 m/s and a pressure of 50 bars. These pipes supported by a metallic crossbeam mobile around an axle and actuated by jack could be oriented from a horizontal position to a vertical position so the determine the slope effect. A databank of pressure gradients, liquid contents, flow patterns, etc... was thus elaborated in relation to the main parameters : phase velocities, pressure, gradient, diameter, oil nature, according to the test programme chosen for the modelization requirements.
The theory of the observed three flow patterns (bubble flow, slug flow and annular flow) and of their transitions has been developed in parallel, and led to computation models which restore with a reasonable accuracy the test data (mean error of about 10%). Last of all, these models have been tested on a small number of data relative to the exploitation of eruptive wells activated by gas-lift, and proved satisfactory.
- PRELIMINARY STUDIES ON GAS/OIL WATER TRIPHASIC FLOWS UNDER VERTICAL CONFIGURATION
A triphasic test loop of a diameter of 2" and a length of 12,5 m was built at the Institut de Mecainique des Fluides de Toulouse. This test loop allowed us to visualize the different flow patterns, particularly the slug flows and to prepare the theoretical basic elements and the instrumentation suitable for the development of a future study.
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DEM - Demonstration contractsCoordinator
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