Summary
Recent advances in hydraulic-fracture-mapping technologies have provided a
wealth of information on the created fracture length in numerous geologic
settings. Before having such measurements, fracture length was estimated using
"uncalibrated" fracture-propagation models, but there was significant
uncertainty in the results that cascaded into subsequent production analyses.
However, we also need to understand how the created fracture length relates to
the location of proppant in the fracture and to the producing or effective
length to evaluate well performance and improve stimulation designs.
Unfortunately, the advanced fracture-mapping technologies that provide accurate
measurements of the created fracture length cannot provide any insights (yet)
into the propped and effective fracture lengths. Advanced production-data
analyses (PDAs), pressure-transient testing, and/or numerical reservoir
modeling are required to determine the effective fracture length.
This paper begins with a comparison of the strengths, weaknesses, and
limitations of fracture modeling, PDA, pressure-transient analysis (PTA), and
numerical reservoir modeling to estimate effective fracture length and
conductivity. This work also evaluates how the complexities (in the hydraulic
fracture) associated with non-Darcy flow, multiphase flow, and complex fracture
geometries affect the results from the various techniques. This work documents
the significant differences in "effective" fracture length that, in
many cases, can result from each technique and how these uncertainties can
impact fracture treatment designs and field-development decisions.
The paper concludes with several field case histories that illustrate the
integration of multiple technologies to determine the created, propped, and
effective fracture length. The case histories illustrate the dramatic
differences in created and effective fracture length that can occur in some
reservoirs, while also showing that in some cases, effective fracture lengths
can be very similar to the created length (and quite long). Integrating the
results from multiple diagnostic techniques in a consistent and coherent manner
can provide significant insights into created, propped, and effective fracture
length that are otherwise unattainable from each technique alone.
© 2009. Society of Petroleum Engineers
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History
- Original manuscript received:
1 August 2008
- Meeting paper published:
3 December 2008
- Revised manuscript received:
10 March 2009
- Manuscript approved:
23 March 2009
- Published online:
22 October 2009
- Version of record:
25 November 2009
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