Date/Time
Date(s) - 01/09/2020
11:30 am - 1:00 pm
Location
Wynkoop Brewery
Categories No Categories
Monthly Luncheon January 9, 2020
Wynkoop Brewery
11:30-1pm
Seismic Reflection Imaging with DAS Data for Reservoir Management
Brian Fuller, Jeff Omvig, and Rich Van Dok Sterling Seismic & Reservoir Services
Tom Bratton, Tom Bratton LLC and APEX Petroleum Engineering
David Langton, Devon
Distributed Acoustic Sensing (DAS) systems are fiber optic borehole seismic recording systems. Development of DAS technology has been rapid and fruitful during the past three to four years. During that time DAS recording systems have gone from being an interesting R & D project to being an important tool for reservoir geophysics. The primary positive attributes of DAS systems are: receiver station spacing of 3-15 ft, repeatable broad bandwidth recording, and simultaneous recording of thousands of data channels over the entire vertical and horizontal length of a borehole. DAS systems can be used both in passive mode for microseismic, low-frequency strain, and acoustic emissions analysis and with active seismic sources including Vibroseis, dynamite, and borehole seismic sources.
A straightforward example of active-source DAS data is shown in the zero-offset VSP in Figure 1. The figure shows a relatively unprocessed zero-offset VSP shot recorded on DAS fiber in the vertical section of a borehole. The down-going first arrivals are easily seen as the first significant waveform sloping downward and to the right. Up-going reflections originate at the line of first arrivals and slope downward and to the left. By any measure this is high quality zero-offset VSP data and was recorded with a single surface seismic shot. The data produced a high quality corridor stack that tied well with surface seismic data. Figure 2 shows a seismic reflection image generated from data recorded with surface Vibroseis sources and a DAS fiber deployed on the outside of casing in a horizontal borehole. The reflection image shows reflectors directly below the horizontal well in which a DAS fiber was deployed outside the well casing.
Trace spacing of the image is 6.6 ft and has a maximum usable frequency above 100 Hz. The data in Figure 2 was recorded prior to fracing and production of the horizontal well. A second repeated survey produced a time lapse reflection image that showed significant changes in reflection coefficients and interval velocities as a result of fracing and production.
Rock mechanics analysis is crucial to understanding the dynamic response of rock properties to fracturing, stress, and pore pressure changes related to production. Time lapse DAS reflection images show more detailed changes in reservoir properties than are generally seen in surface seismic data due to the high spatial resolution of DAS images and generally higher frequency than surface seismic data. Combining rock mechanics analysis with time lapse DAS images can provide reservoir production details to engineers that may not be available from other cost-effective sources. Relatively inexpensive DAS data acquisition makes time lapse imaging a viable method of reservoir surveillance for the lifetime of a field.
About The Author:
Brian holds BS (Western Washington University), MS (U of Wyoming), and PhD (U of Wyoming) degrees in Geophysics. He has over 30 years’ experience in the oil and gas industry including successful oil exploration, software and technology development, and service company work. He has a long term professional interest in borehole seismology and is currently focused on further developing and commercializing seismic reflection imaging using horizontal DAS cables to measure reservoir properties for reservoir and frac engineering uses. Brian has been part of two SEG Best Paper awards, both related to microseismic technology. He currently holds the position of Vice President of Reservoir Geoscience at Sterling Seismic & Reservoir Services in Littleton, Colorado and lives in the Denver area.
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