Fluids analysis system designed for deepwater environments

A new fluid logging and real-time analysis service developed for conditions encountered in deepwater exploration and development projects provides a new dimension in real-time formation eval-uation. By using a fluids analysis chain that includes a mass spectrometer coupled to a gas chromatograph, the service continuously measures the hydrocarbons (C1-C8), particularly marker components such as benzene, toluene, and xylene, as well as the non-hydrocarbon or sour gases such as N2, CO2, and H2S. According to its developer, Geoservices, the service has been successfully tested in wells in various geological environments since 2001 and impro-ved the reservoir evaluation process when tested in deep offshore wells drilled with oil-based mud (OBM).

Central to the service's deepwater capabilities is a heated fluids extractor. Field tests have shown that the extractor improves the quality of sampling from drilling fluids that is necessary for precise formation evaluation and data interpretation. The extraction efficiency in low temperature OBM (15-20° C) has been demonstrated, the company says, not only for the heavier components, but also for the complete analysis range.

The Flair service measures an increased range of components due to the coupling of its innovative fluids extractor with a new field chromatograph/mass spectrometer analyzer. Although high-speed gas analysis systems today can detect C1 to C5 in just under a minute, the heavier hydrocarbons, C6-C8, are not extracted from the drilling fluid using current sampling technology. In addition to extending the range to the heavier hydrocarbons, the Flair service provides real-time quantities of components such as benzene and toluene that are significant indicators for reservoir evaluation. The analyzer overcomes other limitations of conventional techniques and can differentiate co-eluting peaks, e.g., C1, C2, CO2, because they correspond to different ion currents in the mass spectrometer.

In a field test conducted while drilling the 12.25-in. phase of a pilot hole in a deep offshore well (water depth 1,400 m), Flair results were compared to those from a volumetric gas trap coupled with a field chromatograph. The mud was a low toxicity synthetic OBM 1.15-1.20 SG with temperatures of 16° to 20° C at the shakers. With the Flex fluids extractor continuously heating the sample, the results from Flair were more representative of the actual quantities of hydrocarbons contained in the drilled formation than the results from the traditional system, according to Geoservices. The company says the difference is evident when drilling deepwater wells where gases heavier than C2 or C3 are often poorly extracted because of the very low mud temperature at surface. Extraction of heavy components (above nC4) is far better with Flair than with a classical system.

For more information, contact Geoservices. Email: [email protected].