Guest Editorial: The Promise of New Reservoir- Monitoring Technologies
- Norm Warpinski (Pinnacle Technologies)
- Document ID
- Society of Petroleum Engineers
- Journal of Petroleum Technology
- Publication Date
- September 2007
- Document Type
- Journal Paper
- 14 - 16
- 2007. Copyright is retained by the author. This document is distributed by SPE with the permission of the author. Contact the author for permission to use material from this document.
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Reservoir monitoring is a fast-developing area of production technology that has the objectives of measuring, controlling, and predicting the performance of the reservoir. From the measurement perspective, reservoir monitoring may include temperature, pressure, flow rate, composition measurements, periodic logging, 4D seismic, microseismic, deformation measurements, and a host of other possibilities. Most of the measurements made in reservoir monitoring today are wellbore-specific, targeting the conditions in a production or injection wellbore. On the other hand, technologies such as 4D seismic, microseismic, and surface deformation have the potential to image a volume of the reservoir away from wellbores, providing an understanding of how the reservoir is performing as a complete system. It is these imaging technologies that hold great promise for the future improvements in the understanding of overall reservoir performance. It is my opinion that as surface-deformation monitoring is better understood by the industry, there will be a trend toward its use over 4D seismic on many onshore fields because of its low cost, fast turnaround, and wide areal interrogation of the reservoir.
The first recorded instance of surface-deformation monitoring that I am aware of was associated with the disposal of low-level radioactive waste in cement fractures at Oak Ridge in the 1960s. The leveling-type measurements were relatively crude, but the fractures were shallow and wide, and the results were reasonably good. Today, surface-deformation measurements are quite sophisticated, using tiltmeters for precision measurements, interferometric synthetic aperture radar (InSAR) for large-scale reconnaissance, and global positioning systems (GPS) for a host of intermediate and combined applications. Currently, these types of measurements are limited to onshore applications, but subsea measurements are possible in some cases.
Tiltmeters measure the horizontal gradient of the vertical displacement with great precision (up to one nanoradian), and an array of tiltmeters properly situated over a reservoir can be used to extract the surface deformation that is taking place because of processes occurring deep underground. These tools are sensitive enough to pick up Earth tides caused by the moon’s pull on the Earth’s crust over time. Results can be processed to calculate reservoir-level volumetric changes. GPS and InSAR, on the other hand, measure the actual displacement of the surface, but with considerably less precision. InSAR has the least resolution of the techniques, but it has great appeal for the large areal extent that can be covered and minimal (often zero) ground equipment. Being able to identify subcentimeter ground deformation over hundreds of square kilometers for a few thousand dollars has great appeal.
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