Estimating in-place volume associated with each well, leading to estimation
of total reservoir in-place volume, is the cornerstone to any
reservoir-management practice. Yet, conventional methods do not always lend
themselves to routine applications, particularly when used in singular fashion.
However, combining these methods on the same plot has considerable merit in
that they converge to the same solution when material-balance (MB) -derived
average-reservoir pressure is used in a volumetric system.
This study presents a systematic procedure for estimating the
gas-initially-in-place (GIIP) volume when real-time surveillance data of
pressure, rate, and temperature are available at the wellhead. Specifically, we
show that log-log diagnosis, followed by combined static- and dynamic-MB
analysis and transient-productivity-index (PI) analysis, leads to consistent
solutions. Thermodynamic behavior of fluids is also explored to ensure that
converted pressures at the bottomhole and measured rates have consistency and
accuracy for reservoir-engineering calculations.
Layered systems were selected for this study because they represent most
situations. Two synthetic cases probed issues pertaining to
average-reservoir-pressure computation with the pseudosteady-state (PSS)
approach, and two field examples validated the approach presented here.
© 2012. Society of Petroleum Engineers
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- Original manuscript received:
10 June 2011
- Meeting paper published:
21 September 2011
- Revised manuscript received:
8 February 2012
- Manuscript approved:
1 March 2012
- Published online:
10 May 2012
- Version of record:
12 June 2012