Summary
A review of the tidal response in petroleum reservoirs is given. Tidal
response is caused by periodic changes in overburden stress induced by the
ocean tide; the “tidal efficiency factor” is derived by two different
approaches and is in line with a recent well test in the Ormen Lange gas
field.
For small geomechanical pertubations like the tidal effect, we show that a
simplified coupling of geomechanics and fluid flow is possible. The coupling is
easy to implement in a standard reservoir simulator by introducing a porosity
varying in phase with the tide. Simulations show very good agreement with the
theory.
The observation of the tidal response in petroleum reservoirs is an
independent information provider [i.e., it provides information in addition to
the (average) pressure and its derivative from a well test]. The implementation
of the tidal effect in a normal reservoir simulator gives us the opportunity to
study complex multiphase situations and to evaluate the potential of the tidal
response as a reservoir-surveillance method. The case studies presented here
focus on the possibility of observing water in the near-well region of a gas
well.
Introduction
The main objective of this work is to investigate whether the tidal pressure
response in petroleum reservoirs can be used for reservoir surveillance, in
particular to detect saturation changes in the near-well region (e.g., to
detect water encroachment toward a gas well). The literature seems sparse in
this area. Also, our approach of simplified coupling of geomechanics and fluid
flow for small geomechanical effects, and the possibility to implement this in
a normal reservoir simulator, has not (to our knowledge) been discussed in the
literature. Several authors have derived a tidal efficiency factor, but a
review and comparison study seems to be missing.
© 2006. Society of Petroleum Engineers
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History
- Original manuscript received:
9 July 2005
- Revised manuscript received:
29 May 2006
- Manuscript approved:
12 June 2006
- Version of record:
20 August 2006
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