Summary
Hydraulic fracturing is an important well stimulation technique that has
been widely used in the oil and gas industry. Most of the pressure transient
analysis techniques to analyze pressure responses of fractured wells are based
on the assumption that the fracture is either vertical or horizontal. However,
a hydraulic fracture could be inclined with a non-zero angle with respect to
the vertical direction. Field studies have shown that most hydraulic fractures
are not perfectly vertical. Thus, for an inclined hydraulic fracture, the
vertical orientation assumption may lead to erroneous results in well test
analysis especially when the inclination angle is significant. However, there
are very few studies concerning pressure transient analysis of inclined
hydraulic fracture and there is no applicable well test analysis procedure
available for inclined fractures.
The purpose of this study is to develop a technique, based on the pressure
derivative concept, for interpreting pressure transient tests in wells with an
inclined hydraulic fracture. Detailed analysis of unsteady-state pressure
behavior of fully penetrating inclined fracture in an infinite slab reservoir
was provided. Both uniform flux and infinite conductivity models were
considered. The study has shown that inclined fracture pressure data exhibit
similar flow regimes as for vertical fracture counterpart. Those flow regimes
are linear and pseudo-radial flow for both uniform flux and infinite
conductivity models. However, for infinite conductivity model, a bi-radial (or
elliptical) flow regime is also observed. In the case of high formation
thickness to fracture half length ratio and high angle of inclination, both
uniform flux and infinite conductivity inclined fracture model exhibit an
additional flow regime called here early radial flow. This early radial flow
regimes for inclined hydraulic fracture has not been mentioned in the
literature before.
A type curve matching technique was developed in this study using both
pressure and pressure derivative curves. This type curve matching procedures
can be used to obtain the following parameters: fracture half length,
inclination angle, formation permeability and the pseudo-skin factor. The
results should be verified with other pressure plots such as semi-log plot of
Δp vs. t and Δp vs. t1/2 plot. A set of
type curves with associated data was also provided for uniform flux and
infinite conductivity inclined fracture models. Detailed explanations, tables,
figures and a numerical example are included in this paper.
© 2010. Society of Petroleum Engineers
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History
- Original manuscript received:
21 January 2009
- Meeting paper published:
5 April 2009
- Revised manuscript received:
5 January 2010
- Manuscript approved:
12 March 2010
- Published online:
2 September 2010
- Version of record:
9 December 2010
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