Summary
This paper assesses critically the importance of various inputs that are
used for a common method to develop a simulator model of hydraulic fractures
(HFs) in geologically complex, fluvial, tight gas reservoirs. A planar 3D
fracture simulator is used with a fully coupled fluid-/solids-transport
simulator. The geomechanical rock properties from logs (Young’s modulus,
Poisson’s ratio, and Biot’s constant) and diagnostic minifracture injection
tests of individual sandstone reservoirs were investigated to assess their
importance in developing a valid stress model.
This paper describes the investigations by use of a model matched previously
with both net surface pressure and microseismic/tiltmeter data. From these
results, it is possible to obtain a better understanding of how fractures grow
and interact with complex fluvial reservoirs, allowing operators to optimize
field-well performance and completion methods better in these geologic
settings. Additionally, the minimum critical data recommendations necessary to
develop such a model have been identified and will aid operators in developing
their data-acquisition programs. Although developed in the Rocky Mountain
region, the presented technique can be extended to other similar geologically
complex reservoirs worldwide.
Introduction
Currently, engineers have to undertake an ever-more complete HF evaluation
to evaluate fully the well potential and the effectiveness of the treatment
design for creating the desired fracture. Geologically complex reservoirs
require in-depth knowledge of both fluid mechanics and the reservoir-rock
mechanics. It is only recently that the HF engineer has acquired the tools
available to model reservoirs effectively by use of fully 3D models, coupled
with improvements in reservoir analytical techniques.
The overall objective of this study is to undertake sensitivity analyses of
a model matched previously with a method that practitioners consider to be
accurate for developing a 3D HF simulation of a geologically complex reservoir.
Previous work has been carried out in the Piceance basin (Ely et al. 1995) and
other geologically similar tight gas reservoirs (Craig et al. 2000), but the
techniques used in this study are those applied currently to generate input
data for an accurate model of HFs in complex, fluvial, tight gas reservoirs.
The simulator outputs were matched initially with direct diagnostic results
from fracture mapping to help constrain the model and aid in the
simulator-output matching process (Green et al. 2007). In that model, six
different intervals containing several production zones each were hydraulically
fractured and analyzed. This work is part of ongoing research to help operators
and researchers identify the minimum data necessary to model and optimize
effectively the HF treatments in geologically complex reservoirs.
The US Department of Energy/National Energy Technology Laboratory sponsored
a number of projects during the 1980s, and a significant amount of the research
work was undertaken at the Multi-Well Experiment site near Rifle, Colorado
(Settari and Cleary 1986). This multidisciplinary research carried out in the
Piceance basin has gone a long way in helping the stimulation-technology
development in tight gas reservoirs. However, further development of
stimulation technology requires models that can be used to analyze, target, and
optimize HF treatments and to predict well production. This study assesses the
inputs required to model a well in these complex geological systems and makes a
recommendation for the minimum data necessary to develop a fully 3D model of a
hydraulically fractured well.
© 2009. Society of Petroleum Engineers
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History
- Original manuscript received:
2 February 2007
- Meeting paper published:
31 March 2007
- Revised manuscript received:
16 September 2008
- Manuscript approved:
26 September 2008
- Published online:
2 March 2009
- Version of record:
26 February 2009
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