ABSTRACT
The researchers have recently conducted a series of hydraulic fracturing stress measurements in the Sioux Quartzite Ridge, near Sioux Falls, S. Dakota. The results of these tests were surprising in view of the perceived state of stress in the Midcontinent. This chapter describes these measurements, and other evidence supporting the suggestion that the stress condition in the western Midcontinent may be different than previously assumed. It considers potential causes of the change in stress characteristics west of Illinois-Wisconsin. The researchers conducted nine hydraulic fracturing tests in a 30 m borehole near Corson, South Dakota, roughly 15 km northeast of Sioux Falls. The hydraulic fracturing tests were conducted following procedures recently adopted by ASTM. Stress calculations followed the conventional approach. The experience with hydraulic fracturing has been that when an overwhelming number of tests yield a consistent fracture orientation, it has never been determined to be in contradiction with any other reliable indicator of the stress direction.
