Newfield's Williston Buried Array Microseismic; Pushing the Envelope and Integrating Data
Newfield installed a buried array in the Williston basin to monitor microseismic events during hydraulic fracturing of the Bakken and Three Forks formations in 10,000-foot laterals. The seismic array covers 58 square miles with 229 stations spaced at approximately 3000 feet, with 3 geophones buried at 300, 250, and 200-foot depths. The array has proved to be useful in mapping microseismicity during hydraulic fracturing with 300 to 400 microseismic events per well. Approximately 10% of the events are clearly visible in the NMO traces, with high signal to noise ratios. The array microseismic has also been useful in determining fracture geometry and variability in induced fracture half length from well to well. We are confident in the XY resolution but working to better understand the Z (vertical) resolution on the array. We extended the microseimsic analysis in three key pilot areas by integrating microseismic data with other diagnostic completion, pressure, and temperature data. In one area we combined microseismic monitoring with chemical and radioactive proppant tracers. In another area we monitored downhole pressure in a offset well to determine induced fracture pressure interference. The data integration from these pilots demonstrates that the microseismic events are imaging the hydraulically disturbed volume. We see good correlation of event density populations with chemical and radioactive tracer data in offset wells, along with excellent correlation of microseimsic events intersecting offset wells with timing of pressure and temperature anomalies observed from downhole gauges. We also designed the pilots to test frac order vertically and laterally and were able to use the microseismic data to see frac shadowing and depletion sinks from existing wells.
AAPG Datapages/Search and Discovery Article #90193 © 2014 Rocky Mountain Section AAPG Annual Meeting, Denver, Colorado, July 20-22, 2014