| 摘要 |
A subsurface formation having original in-situ stresses that favor the propagation of a horizontal fracture is penetrated by a cased borehole which is perforated at a pair of spaced-apart intervals to form a pair of sets of perforations. Fracturing fluid is initially pumped down said cased borehole and out one of said sets of perforations to form the originally favored horizontal fracture. The propagation of this horizontal fracture changes the in-situ stresses so as to favor the propagation of a vertical fracture. Thereafter, while maintaining pressure on said horizontal fracture, fracturing fluid is pumped down said cased borehole and out of the other of said sets of perforations to form the newly favored vertical fracture.
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