SUBSEA WELL TESTING SYSTEM [PHASE 2]

Ziel

The SWTS (Subsea Well Testing System) is an original concept of multiphase metering system conceived to enhance the performance of present multiphase instrumentation to meet the requirements for subsea application. Following the successful completion of Phase I, in which the principles of the technology have been verified, the SWTS Phase II aims to close the gap with the subsea application by : optimising system dimensions and arrangement, improving the multiphase instrumentation, marinising the critical components in view of the subsea installation and finally fabricating a prototype and performing functional tests on a live well stream at the Agip Trecate field.
The project demonstrated the suitability of the SWTS for field well testing. During the six months trials performed at Trecate, about 130 test runs have been carried out.
Test results indicate that :
- accuracy is well within the target value of approx.10%,
- measurement dispersions around the reference values is minimal, indicating a good repeatability,
- the accuracy is good in all the range of oil and gas flow rates and is independent by the void fraction of the production stream entering the SWTS.
The system is compact and simple and although it was originally conceived for subsea installation, it is extremely interesting also for onshore or platform topsides applications.
The size of the present prototype, 2.2 x 2.2 m of plant envelope and 3 m of height clearance, is suitable to handle more than 10000 BPD of 35-40° API oil. The weight of the system is about 6 t.
The flow conditioner is a 24" diameter, 2.5 m height cylinder and can be assimilated to a standard 24" pipe.
The system does not need active control during well testing operations. For each well, once set the suitable position of the calibration valves, the system remains stable with limited variations of the level into the degasser. This behaviour, is due to the combination of the effects of the pierced tube inside the degasser and of the re-commingling point downward the metering lines.
The SWTS makes possible to :
- calibrate the multiphase instrumentation on line, by comparing gas measurements of the multiphase and gas lines obtained with different amount of separated gas,
- condition the production stream, damping flow rate fluctuation induced by the flow regime,
- maintain a defined range of void fractions through the multiphase instrumentation, optimising its accuracy.
The present prototype is suitable for a future subsea installation adapting its mechanical and electrical interfaces and changing valves actuators and the process instrumentation.
The SWTS is an integrated system to perform well testing, conceived to operate in a multiwell subsea production system downstream a test header. It is made up of :
* a multiphase flow conditioner of contained dimensions, which acts as damper for flow dynamic fluctuations and carries out partial degassing of the production stream,
* one measurement loop for the bulk of the gas flow rate with traditional venturimeters.
* one multiphase instrumentation spool to measure oil, water and gas carry under flow rates.
* a data acquisition package.
The flow conditioner and the separated measurement of the major part of the gas flow rate allow the SWTS to operate with acceptable accuracy (within 5%) in a full range of void fractions, water cuts and multiphase flow patterns without any restriction, overcoming the major limitations of the on-line mutliphase instrumentation available to date.
In Phase I of the project the principles of the technology have been verified. During Phase II a new prototype will be designed and constructed, in order to :
* optimise the control architecture and in particular to eliminate the active control chains of the pressure and liquid level in the flow conditioner. Control will be carried out by using static devices (already conceived in the phase I of the project). Calibration valves (or choke valves) will be present on the liquid and gas lines to calibrate the system adapting it to wide production variations.
* optimise the system dimensions and arrangement.
* improve of the multiphase instrumentation on the liquid stream in order to allow measurements of void fraction up to the 50%.
* marinise the system, which will be functionally and dimensionally similar to a subsea unit even if some elements, as the calibration valves and the pressure and temperature instruments, will be land field components. Functional field dry tests will be carried out on the SWTS Phase II prototype on a land production plant (Trecate) to verify the functionality of the whole system.
The main technical and economic advantage of the SWTS is the removal of the dedicated test line and riser used to connect any multiwell subsea installation with manifolding to the surface facilities. This advantage is common to all the subsea meterings, whereas other benefits can be obtained only with the SWTS such as :
* the possibility to tailor the system both in size and arrangement to cope with specific field requirements as very wide ranges of flow rate, gas oil ratio, flow patterns.
* the simplification, in a multiwell production system with more than 3 wells, in respect to on-line instruments installed on each well (less hydraulic operated valves and more simple control system).
* the presence of the flow conditioner, that allows multiphase instrumentation to work in a less severe conditions, allowing more measurement accuracy in particular when high void fractions and fluctuations affect the production stream.

Programm/Programme

ENG-THERMIE 1 - Programme (EEC) for the promotion of energy technology in Europe (THERMIE), 1990-1994

Thema/Themen

5.9 - PRODUCTION SYSTEMS

Aufforderung zur Vorschlagseinreichung

Data not available

Finanzierungsplan

DEM - Demonstration contracts

Koordinator

TECNOMARE SPA - SOCIETA PER LO SVILUPPO DELLE TECNOLOGIE MARINE

EU-Beitrag

Keine Daten

Adresse

SAN MARCO 3584
30124 VENEZIA
Italien

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