SPE Drilling & Completion
Although unstimulated horizontal wells have been successful in naturally
fractured reservoirs and in reservoirs with gas- or water-coning problems,
fracturing a horizontal well may be a viable option in certain situations.
Because of the dependence of fracture orientation on well direction with
respect to the stress field, the possibility of fracturing a horizontal well
must be considered before the well is drilled. The appropriate contingency
plans should be made to anticipate the possible low production from an
unstimulated well. It should be remembered that fracturing a horizontal well
may also dictate how the wellbore may be completed or oriented. Fracturing a
horizontal well may take place in one of the following situations:
- Restricted vertical flow caused by low vertical permeability or the
presence of shale streaks.
- Low formation productivity because of low formation permeability.
- The presence of natural fractures in a direction different from that of
induced fractures. Thus, induced fractures have a high chance of intercepting
the natural fractures.
- Low stress contrast between the pay zone and the surrounding layers. In
this case, a large fracturing treatment of a vertical well would not be an
acceptable option because the fracture would grow in height as well as length.
Drilling a horizontal well and creating either several transverse or
longitudinal fractures would allow rapid depletion of the reservoir through the
Although fundamentally similar to fracturing vertical wells, fracturing
horizontal wells has its unique aspects that require special attention to
secure successful treatment. Differences between horizontal and vertical wells
exist in areas of rock mechanics, reservoir engineering, and operational
aspects. To start with, the basic rock-mechanics aspects are examined.
© 2008. Society of Petroleum Engineers
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- Original manuscript received:
15 June 2004
- Meeting paper published:
16 March 2004
- Revised manuscript received:
11 February 2008
- Manuscript approved:
22 February 2008
- Version of record:
15 September 2008