Pinnacle, a Halliburton service, provided FracSeisSM microseismic mapping services to Enerplus in the Williston Basin in Montana in March of 2010. Pinnacle utilized two 18-tool stacked microseismic arrays to map a total of 16 fracture treatment stages in two Bakken horizontal laterals.
Tom Riebel, BD Manager for Pinnacle in the Rockies, stated, "Fracture mapping with downhole geophones is becoming easier in the Bakken. Pinnacle's stacked microseismic toolstring has helped to expand typical hearing distances to average-sized microseismic events to about 3,000 ft, while more infill drilling in the basin has helped to reduce well-to-well distances. In this particular project, Pinnacle used the vertical sections of three existing horizontals to map fracture growth along two horizontal laterals."
Downhole microseismic mapping generally results in excellent event location accuracy, with average Bakken lateral event location uncertainties of ±50 ft and depth event location uncertainties of ±30 ft. This is far superior to surface microseismic, where fracture height is not reported due to its uncertainty of many hundreds of feet at best. Downhole microseismic technology is the only viable technology to identify out-of-zone fracture growth from the thin Bakken pay interval, providing knowledge regarding possible growth into the Three Forks and Lodgepole formations. Darien O'Brien, Senior Reservoir Engineer at Enerplus in Denver, indicated that "Mapping the data in this manner provided Enerplus with valuable insight into questions about fracture orientation and height growth. Until this point, we had only speculation to go on, so this added to our project knowledge base."
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