Conventional Probe Tool Acceptable sample Time Acceptable sample Time
Quicksilver Probe Tool
Main probe Guard probe
> Quicksilver Probe focused-sampling tool. Concentric intake flow areas of the Quicksilver Probe tool are connected to independent pumps in the MDT tool (right). The outer, or guard, probe extracts filtrate and continues to pump during sampling to keep contaminated fluids from migrating to the main probe. In addition to lower levels of sample contamination (graph, right), this assembly can produce acceptable samples more quickly than conventional probe assemblies (left).
to the point that fluid properties can be recorded and evaluated while the tool is still in the well. Because of this, sample recovery to the surface is not always necessary. In addition, engineers can create a Fluid Profiling log throughout the reser- voir interval from laboratory-quality measure- ments acquired at downhole conditions.
The Downhole Laboratory Most major service companies have some form of downhole fluid analysis service. Each company has chosen specific methods to analyze the fluids, including optical absorption and magnetic reso- nance. The InSitu Family sensors in the MDT tool provide the following measurements: • hydrocarbon fluid composition (C1, C2, C3-5 and C6+)
• gas/oil ratio • CO2 concentration • color (and relative asphaltene content) • fluorescence • pH (for water samples) • live-fluid density and viscosity • oil-base mud (OBM) contamination • resistivity • pressure and temperature (at sample depth). However, the basic method for fluid analysis
is optical spectroscopy from the InSitu Fluid Analyzer module (bottom right).17
Optical spec-
trometers measure light absorption at different wavelengths for fluids passing through the sensor
Light source
Fluorescence detector
Pressure and temperature sensor
density sensor Live-fluid
Fluid flow
Resistivity sensor
Filter array spectrometer
> Downhole fluids laboratory. As fluid moves through the MDT tool, the InSitu Fluid Analyzer service acts as a portable fluids laboratory. Two spectrometers measure light-absorption properties of the fluid as well as its color. Fluorescence sensors provide retrograde condensation detection and can differentiate oil type when the fluids are in an emulsion. The pH of water samples is measured by injecting a pH-sensitive dye into the flow stream (not shown) and detecting the color change. Pressure, temperature and resistivity sensors acquire data as fluid flows through the tool. A live-fluid density sensor is located in the flowline, and a second sensor can be placed in the probe assembly as well.
Oilfield Review Autumn 09 FluidsLab Fig.5
ORWIN09/10-FluidsLab Fig.5
12. Connan J: “Biodegradation of Crude Oils in Reservoirs,” in Brooks J and Welte DH (eds): Advances in Petroleum Geochemistry, vol. 1. London: Academic Press (1984): 299–335.
13. Mullins, reference 4: 26.
14. Biogenic methane can be differentiated from thermogenic methane by stable carbon isotope ratios.
15. Mullins, reference 4: 52.
16. For more on focused-probe sampling: Akkurt R, Bowcock M, Davies J, Del Campo C, Hill B, Joshi S, Kundu D, Kumar S, O’Keefe M, Samir M, Tarvin J, Weinheber P, Williams S and Zeybek M: “Focusing on Downhole Fluid Sampling and Analysis,” Oilfield Review 18, no. 4 (Winter 2006/2007): 4–19.
17. For more on optical spectroscopy: Crombie A, Halford F, Hashem M, McNeil R, Thomas EC, Melbourne G and Mullins OC: “Innovations in Wireline Fluid Sampling,” Oilfield Review 10, no. 3 (Autumn 1998): 26–41.
Betancourt et al, reference 1. spectrometer Grating
Space for future sensor
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Contamination level
Contamination level
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