SPE Reservoir Evaluation & Engineering
Volume 13,
Number 6,
December 2010,
pp. 906-913
Summary
The possible influence of the well casing in reservoir-deformation
measurements by the radioactive-marker technique (RMT) is investigated. The
issue is quite important because RMT data may be used for a most-representative
estimate of the in-situ vertical rock compressibility
cM (i.e., a basic parameter to predict the land
settlement caused by gas-/oilfield development or the land uplift caused by
underground fluid injection). A geomechanical finite-element (FE) model is
implemented to evaluate the disturbance caused by the stiffness of the steel
casing and the surrounding cement on the amount of deformation around the
borehole as detected by RMT. The FE model is integrated by a class of
elastoplastic interface FEs (IFE) specifically designed to account for the
potential sliding of the different materials (i.e., along the contact surfaces
between the steel casing and the cement, and the cement and the exploited
formation). The numerical simulations make use of real casing data and
geomechanical information from the Northern Adriatic basin, Italy. The results
show that sliding is not likely to occur along the contact surfaces and that
RMT appears to be a reliable tool for assessing the actual geomechanical
properties of the depleted formation at a depth larger than 1000 m, where the
in-situ deformation is negligibly affected by the casing stiffness. In shallow
softer units, the compaction as measured by RMT is influenced progressively by
casing, with a corresponding likely underestimate of cM.
© 2010. Society of Petroleum Engineers
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History
- Original manuscript received:
25 June 2009
- Revised manuscript received:
6 December 2008
- Manuscript approved:
28 January 2010
- Published online:
23 August 2010
- Version of record:
9 December 2010
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