Using multiphase flowmeters in field operations has now become a widely accepted practice especially in the range of Gas Volume Fraction (GVF) of 0 to 85%. There is still some doubt about the performance of this type of device especially in the High (92–96%) or Very High GVF (96–98%) ranges. Most of the purchasers put a cut off in the GVF range of 85–92% following the type of technology. These criteria are often based on past experience or special cases, which could be several years old. A split in terms of naming is even commonly accepted in the multiphase business between Multiphase Flow Meter and Wet Gas Meter. With the recent dedicated Gas Mode developed by Schlumberger, it is now possible to test both gas and oil wells with the same hardware. The focus put in the past few years on a combination of robust and simple measurements (Venturi and gamma ray) in multiphase flow-metering solutions for any type of well based on the advantages and benefits of the industry recognized Vx* Technology. In this paper, we will review the benefit of the combination of Venturi and gamma ray fraction meter and its application to gas well testing. Today, the use of the entire information of a gamma ray spectrum gamma ray (more than 2 rays) allows a real-time or an a posteriori quality control and improvement of the overall performance of the meter in any type of conditions. This statement will be presented through a campaign of tests done in South America. First of all, we will show how the entire information of a gamma ray spectrum permits a quality control in real time, and allows tracking of fluid composition change over time. Then we will focus on high producing gas wells clean-up that have been successfully tested using the Vx technology in Gas Mode in 2005. Exceptional results against conventional test separator have been presented in previous paper (Ref [10]) with a maximum error of 2–3% for the gas. The current paper will also put a special emphasis on the salinity change. Introduction A 3 phase flow measurement requires as minimum information the velocity for each phase (i.e. 3 velocity measurements) and 2 holdups (i.e. fractions) knowing that the sum of the 3 holdups is equal to 1. Numerous techniques exist to try to achieve these 5 measurements ([Ref [1, 2, and 9]). Meanwhile, a multiphase flowmeter is measuring at line conditions the different flowrates; therefore it is necessary to associate two other measurements for PVT Conversion from line to standard conditions (i.e. Pressure and Temperature Sensors). The most common technique used in the industry to measure flowrates is the Venturi (or differential measurements); all manufacturers are using one or several Venturi and most of the time coupled with a density nuclear measurement. The fraction measurement techniques are more versatile and we could split them between low energy gamma ray measurement, the most common one, and electromagnetic measurement. The former is the simplest option to get the multiphase meter as less complex as possible. Indeed, the high energy gamma ray being already present for density measurement, the addition of a second radionuclide or an appropriate chemical source could provide the two energy levels required to do the fraction measurement [Ref 2]. This leads to a compact and efficient solution.

The OBAGI Field is situated onshore NIGERIA. Among the numerous productive layers, one is a thin 36 ft thick disk-shaped oil column. This unconsolidated deltaic sand is produced, making the best possible use of the natural geological features to limit gas and water coning. Permeability is 2 darcys and bottom hole oil viscosity 0.8 cp.In 6 fact, ELF NIGERIA has already recovered 21 x 10 bbl of oil (that is 19 % of the original oil in place), and expects to obtain a final recovery of 30 %.

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To achieve A.L.S. expected performances an excellent bunching was indispensable. The adjonction of a chopper and a prebunching cavityto buncher gives results conform to those given by computers. Slight modifications in RF structures and magnetic focusing were succesful as tests showed no trace of BBU.PART I -BUNCHERIn order to obtain 50 % of current in an 1 % energy spread, elementary bu4ch phase extension must be less than 5°at first section end. The chopper gives 900 phase width bunches. After prebunching cavity phase extension is reduced to 200 and at first section end the bunch is only 50 wide. A low voltage injector was chosen solution, already selected by CSF for its previous constructions. A.L.S. buncher main parts are -a 2.998 Mcs chopper. -a prebunching cavity and -A.L.S. first section. - ChopperTwo RF cavities are powered at accelerator frequency. They are oscillating in phase opposition on TM 011 mode. The chopper is put in the accelerator magnetic field B. An electron entering first cavity sees RF electric field E and magnetic field B ; under their action he is going through a cyclotron resonance. In the XY plane equations of motion are the same as for the cyclotron. Along Z axis there is no force applied and velocity remains constant. Calculation shows that impact trajectory of electrons on median wall is nearly a circle. If an aperture of angle f is cut in this wall only electrons with right phase shall go in the second cavity where due to the opposite electric field they will enter the prebunching cavity on Z axis. Relation between RF pulsation and cyclotron pulsation at resonance is as follows : (I) it QIt -__ n 8T _~x U y,F Q = e B Im C) = RF pulsation ; = electron charge 1r). = electron mass; velocitytu , A= RF wave length in chopper guide, B = magnetic field ; ', IL odd or even numbers. Cavity dimensions were the following: 155 mm x 20 mm x 70,5 mm with a Q. = 1600Computed resonances were in accordances with those observed. ALS operating values were : injection THT 33,5 KV, magnetic field : 1200 G. RF peak power 2,5 KW.Section S 1 only It was tested in function of RF frequency at different power levels. For each parameters values a spectrum was measured with a 10-3 width slit. Energy variation from 5,25 MeV to 6,25 MeV was obtained with a RF peak power varying between 700 KW and 1,45 MW. It was observed that spectrum is nearly independant of power level and injection tension as computer calculations showed it. Measured mean spectrum was about 1,6 % with a 1,4 % minimum at 6MeV -Section S 1 with chopper and prebunching cavity Without chopper spectrum shows that 10 % -20 % of electrons are not in the main bunch and have a wide energy spread. In the same conditions but with chopper operating these electrons are wiped out and spectrum bettered. The best energy spectrum thus measured with a 10