Summary
This paper provides an overview of design and life-cycle considerations for
certain unconventional-reservoir wells. An overview of unconventional-reservoir
definitions is provided. Well design and life-cycle considerations are
addressed from three aspects: upfront reservoir development, initial well
completion, and well-life and long-term considerations.
Upfront-reservoir-development issues discussed include well spacing, well
orientation, reservoir stress orientations, and tubular metallurgy.
Initial-well-completion issues include maximum treatment pressures and rates,
treatment diversion, treatment staging, flowback and cleanup, and dewatering
needs. Well-life and long-term discussions include liquid loading, corrosion,
refracturing and associated fracture reorientation, and the cost of
abandonment.
These design considerations are evaluated with case studies for five
unconventional-reservoir types: shale gas (Barnett shale), tight gas (Jonah
feld), tight oil (Bakken play), coalbed methane (CBM) (San Juan basin), and
tight heavy oil (Lost Hills field). In evaluating the life cycle and design of
unconventional-reservoir wells, "one size" does not fit all and
valuable knowledge and a shortening of the learning curve can be achieved for
new developments by studying similar, more-mature fields.
Introduction
The emergence of unconventional reservoirs as critical sources of oil and
natural-gas production has forced engineers and geoscientists to view field
development in new ways. One of these areas is the life cycle and design of the
individual wells and the upfront considerations that must be taken into account
for long-term development. Unconventional reservoirs bring unique problems to
design topics that range from well-spacing considerations to wellbore
orientation, most of which need to be considered before the well is drilled and
should be addressed as part of an overall reservoir-management plan.
When considering the choice of a well type for an unconventional reservoir,
one type is not appropriate for all situations. For instance, the need for a
single, small-diameter wellbore in a tight gas field is dramatically different
from the need for a horizontal wellbore in a shale-gas or naturally fractured
oil system. Additionally, not only do the constraints of the initial completion
need to be considered, but so does the length of the life of the well, which
can be considerable in unconventional reservoirs.
This paper discusses the design and life-cycle considerations for certain
unconventional reservoirs. It defines the types of unconventional reservoirs
that are addressed and discusses the specific situations that should be
considered for such reservoirs. Certain case studies that demonstrate the need
for such considerations are presented.
© 2009. Society of Petroleum Engineers
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History
- Original manuscript received:
2 January 2008
- Meeting paper published:
10 February 2008
- Revised manuscript received:
24 June 2008
- Manuscript approved:
8 August 2008
- Published online:
1 May 2009
- Version of record:
1 May 2009
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