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DAS Microseismic Monitoring and Integration With Strain Measurements in Hydraulic Fracture Profiling
- Tuesday July 25
- 2:40 pm – 3:05 pm
- Room 16AB
A fiber-optic cable was installed in a treatment well in the Meramec Shale covering the entire length of the well from surface to target depth, resulting in approximately 1000 recorded channels. The large number of channels, combined with the wide aperture, allowed us to record and locate microseismic events and compare them to traditional DAS measurements such as crosswell strain.
During the treatment of two wells, temperature, strain, and microseismic activity were measured. During treatment of the well containing the fiber, three stages were recorded, and despite significant treatment-related noise, hundreds of events were detected and mapped. While treating a nearby well, 30 stages were recorded, resulting in over 4000 detected and mapped events due to the increased signal to noise ratio.
For a few stages, an independent standard borehole seismic multi-well microseismic monitoring program detected common events. These common events were typically in the magnitude range of -0.4 to -2. The DAS events showed highly complex wave forms within the frac zone indicating the temporal evolution of the rupturing process. The mapped locations of DAS events extended to a maximum of about 1500 feet from observation well, although the majority of DAS events were detected in the inter-well space and close to the treatment well due to the lower sensitivity of the fiber recording.
While we used a standard range of frequencies for microseismic analysis, at a lower frequency range we could measure crosswell strain, though temperature and strain effects can be intermingled. Specialized data processing was applied to remove temperature effects as much as possible and enhance the strain signatures. After obtaining differential strain estimates, we successfully correlated those signatures to the evolution of microseismic events in time and space.
The analysis of this DAS data set demonstrates that current fiber-optic technology can provide enough sensitivity to detect a significant number of microseismic events which we can integrate with temperature and strain data for an improved reservoir description.