Schlumberger

InSitu Composition Reservoir Fluid Composition Sensor

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Dual-spectrometer downhole analysis of hydrocarbons, GOR, CO2, water content, and filtrate contamination

The Vis-NIR spectrum measured by the two InSitu Composition spectrometers is used for the analysis of fluid hydrocarbon composition, GOR, CO2, water content, and mud filtrate contamination. In addition to the improved measurement capabilities of the dual spectrometers, the compositional analysis is refined with an algorithm developed from Beer-Lambert’s law, which indicates that the optical absorption of a component is proportional to its concentration. Thus the spectrum of a live oil is a weighted sum of the absorptions of its individual components.

Accounting for light and heavy ends

The significant variation of the C6+ group in live oil is also accounted for in the algorithm. The C6+ group is the main component of stock-tank oil, and the detailed spectrum of the grating spectrometer in the 1,600- to 1,800-nm range was used to characterize stock-tank oil on the basis of wax and branched-alkane content. From this data, the fluid composition analysis corrects for spectrum variation. An independent determination of ethane (C2) is now possible for the first time owing to the increased resolution of the grating spectrometer together with advanced deconvolution. This extra detail in analyzing light-end hydrocarbon components is critical for productivity analysis and economic assessment.

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Downhole Fluid Analysis: No More Waiting for the Lab

This graph demonstrates excellent agreement between InSItu Fluid Analyzer and laboratory composition measurement data.
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