Representation of fluid sampling at the reservoir

InSitu CO₂

Reservoir fluid CO₂ sensor

The important consideration of CO₂ content

Carbon dioxide is soluble in crude oils, swells net oil volume, and reduces oil viscosity even before it achieves miscibility. The amount of CO₂ must be accurately accounted for when developing your hydrocarbon reserves.

However, reliable quantification of CO₂ from reservoir fluid samples can be difficult, especially if there is water in the collected samples, because CO₂ easily reacts with water, whether from mud filtrate contamination or formation water.

The filter array and grating optical spectrometers of the InSitu Fluid Analyzer real-time downhole fluid analysis system have the ideal wavelength range for the detection and analysis of both hydrocarbons and CO₂. A dedicated channel on the filter array spectrometer to the CO₂ absorption peak is complemented with dual baseline channels above and below that subtract out the overlapping spectrum of hydrocarbon and small amounts of water.

The resulting CO₂ content is delivered in real time with the upper and lower accuracy tolerances on the measurement to give you increased confidence in the measurement accuracy for different environments.

The wavelength ranges of the filter array and grating optical spectrometers are optimized for the detection and analysis of hydrocarbon and CO₂ components in crude oil and natural gas, as well as for the determination of water content and pH. The measurement of optical density (OD) is simply the base-10 logarithm of the ratio of incident light to the transmitted light through a cross-section of reservoir fluid in the flowline. OD is presented as a dimensionless unit, whereby one OD absorbance unit implies a 10-fold reduction in light intensity. For example, OD = 0 means 100% of light is transmitted, OD = 1 indicates 10% light is transmitted, and OD = 2 means 1% light is transmitted. The measurements are conducted across the entire frequency spectrum of light in the Vis-NIR range.