SPE Journal
Volume 17,
Number 3,
September 2012,
pp. 752-767
Summary
Tight gas plays often have multiple lenses of producing formations.
Multizone fracturing or limited-entry fracturing is a cost-effective method to
complete and produce tight gas wells in these layered reservoirs. The rate and
volume of fracturing fluid injected into the different layers have an important
role in determining the fracture characteristics. However, because of the
spatial restriction of downhole conditions, it is very challenging to obtain a
specific injection rate for each perforated zone. Temperature variations in the
wellbore, outside of the casing, are available with new technology such as
distributed-temperature-sensor (DTS) fiber-optic cables. The main objective of
this study is to relate the wellbore-temperature changes as measured by DTS
data to the wellbore and fractured-interval injection rates during a multizone
fracturing process.
We develop a forward simulation model on the basis of mass and energy
conservation for calculating the temperature profile and temperature history in
the wellbore and in the rock surrounding the wellbore. The model allows for
liquid flow into the fractured interval. Subsequently, the model is integrated
with an inverse-estimation algorithm, which is used to estimate flow rates both
in the wellbore and into the fractured interval. The estimation algorithm is
based on a gradient search method. A distinguishing feature of this work is the
development of a radial model used to represent the temperature evolution in
the near-wellbore region. The higher order allows accurate calculation of the
temperature in the wellbore while still capturing the fluid-flow and
heat-transport aspects of the hydraulic-fracture propagation.
Our estimation results show a good comparison between the calculated
temperature profiles and those observed in the field with DTS. Also, the model
is able to estimate a flow-rate history consistent with total field-injection
volume. This work enables an accurate and quick interpretation of the wellbore
DTS data to determine the interval injection rates during a
hydraulic-fracturing process. Knowledge of accurate interval injection rates
and the corresponding fracture characteristics can be useful in designing a
better limited-entry completion that can optimize the fracture length by use of
rate control and/or fluid diversion.
© 2012. Society of Petroleum Engineers
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History
- Original manuscript received:
13 November 2010
- Meeting paper published:
25 January 2011
- Revised manuscript received:
19 December 2011
- Manuscript approved:
17 January 2012
- Published online:
19 July 2012
- Version of record:
12 September 2012
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