Summary
The exploitation of unconventional gas reservoirs has become an ever
increasing component of the North American gas supply. The economic viability
of many unconventional gas developments hinges on effective stimulation of
extremely low-permeability rock by creating very complex fracture networks that
connect huge reservoir surface area to the wellbore. In addition, gas
desorption may be a significant component of overall gas recovery in many
shale-gas reservoirs. The widespread application of microseismic (MS) mapping
has significantly improved our understanding of hydraulic fracture growth in
unconventional gas reservoirs (primarily shale) and has led to better
stimulation designs. However, the overall effectiveness of stimulation
treatments is difficult to determine from MS mapping because the location of
proppant and the distribution of conductivity in the fracture network cannot be
measured (and are critical parameters that control well performance).
Therefore, it is important to develop reservoir-modeling approaches that
properly characterize fluid flow in and the properties of a complex fracture
network, tight matrix, and primary hydraulic fracture (if present) to evaluate
well performance and understand critical parameters that affect gas
recovery.
This paper illustrates the impact of gas desorption on production profile
and ultimate gas recovery in shale reservoirs, showing that in some shale-gas
reservoirs desorption may be a minor component of gas recovery. In addition,
the paper details the impact of changing closure stress distribution in the
fracture network on well productivity and gas recovery. In shale-gas reservoirs
with lower Young's modulus rock, stress-dependent network-fracture conductivity
may reduce ultimate gas recovery significantly. The paper includes an example
that contrasts the application of numerical reservoir simulation and advanced
decline-curve analyses to illustrate issues associated with conventional
production-data-analysis techniques when applied to unconventional
reservoirs.
Selected examples from the Barnett shale are included that incorporate MS
fracture mapping and production data to illustrate the application of
production modeling to evaluate well performance in unconventional gas
reservoirs. This paper highlights production modeling and analysis techniques
that aid in evaluating stimulation and completion strategies in unconventional
gas reservoirs.
© 2010. Society of Petroleum Engineers
View full textPDF
(
2,308 KB
)
History
- Original manuscript received:
22 July 2009
- Meeting paper published:
24 September 2009
- Revised manuscript received:
30 December 2009
- Manuscript approved:
2 March 2010
- Published online:
19 August 2010
- Version of record:
24 August 2010
View Cart
