Evaluating Formation-Fluid Properties During Sampling-While-Drilling Operations

Recent experience with a newly introduced sampling-while-drilling service has shown that it is possible to make reliable downhole formation-fluid-property estimates during sampling-while-drilling operations. These property and contamination estimates facilitate the management of the entire while-drilling sampling process by aiding sample-capture decisions and allowing the best possible use of the sample bottles currently available on a drilling bottomhole assembly. Moreover, the contamination estimates, together with the real-time fluid-property estimates, enable prediction of the uncontaminated-fluid properties.


If performed during drilling (when filtrate invasion is not fully developed), fluid scanning—where formation fluid is pumped and analyzed within the sampling-while-drilling tool without taking a sample—affords the opportunity to characterize the formation fluid at potential sampling depths before committing sample chambers. The success of such an approach depends on how completely the in-situ fluid can be characterized and how free of contamination the assessed properties are.

By use of downhole optical spectrometry, it has been shown recently that it is possible to estimate in real time at least the following formation-fluid properties: fluid color and type, hydrocarbon composition at various levels, carbon dioxide (CO2) content, gas/oil ratio (GOR), formation volume factor (FVF), and asphaltene content. Other measurements such as pressure, temperature, pressure gradients, and fluid density and viscosity enhance the characterization. Although not replacing pressure/volume/temperature (PVT) laboratory measurement of fluid properties, this list allows the fluid to be characterized sufficiently well to determine the fluid type and to differentiate between fluids at different spatial locations. This capability becomes important when deciding which fluid to sample, whether to recover a fluid sample, and whether another sampling run should be undertaken.

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 173152, “Evaluating Formation-Fluid Properties During Sampling-While-Drilling Operations,” by K. Indo, J. Pop, K. Hsu, and S. Ossia, Schlumberger; G.-L. Atzeni and A. Malossi, Eni; and V. Agarwal, A. Garcia-Mayans, S. Paul, J. Varughese, and S. Haq, Schlumberger, prepared for the 2015 SPE Drilling Conference and Exhibition, London, 17–19 March. The paper has not been peer reviewed.
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Evaluating Formation-Fluid Properties During Sampling-While-Drilling Operations

01 August 2015

Volume: 67 | Issue: 8


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