InSitu pH Reservoir Fluid pH Sensor | Schlumberger

InSitu pH

Reservoir fluid fluorescence sensor

Measure formation water pH without contamination effects

Water pH is measured with the InSitu pH reservoir fluid pH sensor by injecting dye into the formation fluid being pumped through the flowline of the InSitu Fluid Analyzer system. The pH is calculated with 0.1-unit accuracy from the relevant visible wavelengths of the dye signal measured by an optical fluid analyzer.

Making the measurement at reservoir conditions avoids irreversible pH changes that occur when samples are brought to the surface, as acid gases and salts come out of solution with reduced temperature and pressure and routine laboratory flashing of the sample.

InSitu pH sensor measures the fluid pH across the entire flowline cross section, making it more robust than potentiometric methods of measurement, which are compromised when oil and mud foul electrode surfaces. Direct pH measurements with dye also avoid the limitations of resistivity measurement in monitoring contamination, which requires a sufficient resistivity contrast between the filtrate and formation water.

InSitu pH  sensor graph
InSitu pH  sensor graph
InSitu pH sensor

Why you need pH measurement

The InSitu Fluid Analyzer system relies on the InSitu pH sensor for tracking mud filtrate contamination by distinguishing between formation water and mud filtrate in real time.

The formation water pH is a key parameter in water chemistry, used for calculating the corrosion and scaling potential of the water, understanding reservoir connectivity and transition zones, determining the compatibility of injection water and formation water, and designating optimal salinity and pH windows for polymer and gel injections.

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