Measuring the hydrocarbon content of oil and gas reservoirs is a real choke point in our industry’s reservoir evaluation process. In fact, the current industry standard — the porous plate technique — suffers from a major drawback: it’s slow. A complete interpretation takes almost a year, despite the fact that resistivity logging is done during drilling. Our teams therefore developed a disruptive solution that can deliver capillary pressure curves and electrical log (resistivity) data for a complete drainage-imbibition cycle simultaneously and with a high degree of confidence.
Water Saturation, a Tough Indicator to Measure
Water saturation is a vital parameter that must be monitored throughout a reservoir’s life. It helps engineers estimate the reserves in place, while providing invaluable information about the water level's rise or the quality of the flushing process when water is injected.
Currently, water saturation is calculated using electrical logs. Taken during drilling, they’re interpreted using default parameters. At the same time, the core samples are analyzed in the lab to measure capillary pressure curves and resistivity indexes. This step can take a full year.
Actually, the real resistivity parameters come in after the fact and are only very rarely used to update the initial well log evaluation. The reservoir’s saturation model is then deduced solely from the capillary pressure data, without any chance to align it with the resistivity logs. This situation can result in significant revisions in some cases of the volumes in place.
The year-long time horizon also makes it impossible to monitor saturation levels using logging once a reservoir has begun producing.
Ultra-Fast PcRI, an Innovative World First
To resolve this bottleneck, we created a technological innovation project in 2015 to find a method able to measure capillary pressure curves and resistivity indexes simultaneously. After two years of research, Ultra-Fast PcRI is a now patented invention that exemplifies our cutting-edge technical expertise. It employs a combination of a centrifuge to generate a capillary pressure gradient; saturation imaging using nuclear magnetic resonance (NMR) to measure saturation; and resistivity imaging using electrodes developed at Total.
Ultra-Fast PcRI has several advantages:
- Reliable results can now be obtained in just a few weeks. Shortening the time involved makes the measurements compatible with well log interpretation during operational phases.
- The process requires less handling, increasing measurement safety.
- Ultra-fast PcRI works equally well on homogeneous and heterogeneous samples, because of the NMR imaging. This makes more data available.
- Easily transferrable, the method significantly lowers the costs of acquiring such measurements in the laboratory.
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