This paper presents an alternative methodology for the determination of 3 phase fluid saturation behind casing. The case study refers to the Algyo Field in Hungary, which has the largest hydrocarbon accumulations in the Pannonian basin and is characterised by more than 70 oil and gas reservoirs in a mature state of exploitation. The production is primarily from more than 800 vertical wells. Recently several horizontal wells have been drilled, on the basis of this 3 phases evaluation, to extend the existing producing levels, to target new hydrocarbon zones and to convert some good porous reservoir units to gas storage. The monitoring of the fluid contacts in the multi-level sandstone reservoirs of the Upper Pannonian basin is a key component in the evaluation of the field production status. However, since the formation water in this field has very low and variable salinity and as some areas have been subjected to fresh water injection, the standard SIGMA measurement from a Pulsed Neutron Capture method is not capable of differentiating oil from water and can provide only a qualitative indication of gas saturation. An alternative methodology was required which would provide sufficiently high fidelity 3 phase saturation measurements to compare directly to simulator history matching results and allow a more accurate assessment of the development projects.To distinguish and quantify saturations of three separate phases, the Reservoir Performance Monitor (RPM-C) tool, a pulsed neutron instrument capable of acquiring data in several modes, has been employed. This tool acquires high-resolution measurements through casing, producing an exceptionally clear and accurate picture of the gas volume in place using the GasViewSM analysis technique. This new Baker Atlas product is based on the confluence of three new-technologies: new design, new response characterization, and a gas saturation analysis algorithm. While the data acquired using the Carbon/Oxygen mode can distinguish between oil and water, the GasViewSM data can distinguish between gas and liquid and the integration of both provides a true three phase saturation analysis solution. To prove its extreme reliability, GasViewSM has recently won two important technology awards from ICoTa (Intervention and Coil Tubing Association) in November 2007 and April 2008. This makes now GasViewSM as a patented product from BakerAtla

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