Technical Paper: Quantification of Carbon Dioxide Using Downhole Wireline Formation Tester Measurements

Society: SPE
Paper Number: 100739
Presentation Date: 2006
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Carbon dioxide (CO2) occurrence in hydrocarbon bearing formations presents a challenge to the valuation and subsequent prospect development of the hydrocarbons. Corrosion is a major concern effecting capital and operational expenditures since the presence of CO2 can cause corrosion failures. Carbon dioxide also denotes an issue for health, safety and the environment (HSE) and is readily absorbed by elastomer seals, weakening the resistance of those seals and compromising the integrity of the fluid samples and the safety of equipment and personnel.

The conventional procedure to evaluate the CO2 content in a hydrocarbon bearing formation is to take fluid samples downhole or on surface during a well test and send the fluids to the laboratory for analysis. Both methods are compromised by the reactive nature of CO2, whose concentration can change significantly by reaction with formation waters, mud filtrates, etc. before reaching an analysis facility. Optimizing the fluid sample acquisition program to match existing fluid complexities is impossible without real-time analysis.

Recently, NIR (near-infrared) spectroscopy has enabled the real time analysis of the CO2 content in downhole fluid samples. This paper describes a new method for using DFA (Downhole Fluid Analysis) in the real-time determination of the CO2 amount in the MDT (Modular Dynamic Formation Tester) flow line. Extensive laboratory data from a research grade spectrometer and shop data with the downhole tool support the new methodology. Multiple interpretation algorithms have been developed for CO2 quantification and verified in the laboratory. Several log examples are given demonstrating successful CO2 detection and subsequent confirmation of the measured concentrations by the laboratory data

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