Leak-Off Test Analysis to Evaluate Seal
: Examples from the Central North
Sea
Najwa Yassir1, Peter Winefield2, and Amgad
Younes1
1 Shell International Exploration and Production, 2288 GS Rijswijk, Netherlands
2 Shell International E&P - Technology Development
& Research, Houston, TX
The main control on seal
integrity in an overpressured environment is the
minimum principal stress, usually the minimum horizontal stress. This is
generally defined on a regional basis by using leak-off test data. Methodologies
vary, but the lower bound of leak-off test data is commonly used is risking
analysis; this is backed by data from rare extended leak-off tests, which plot
on the lower bound of a LOT data set. Where overpressures are compartmentalized,
however, the minimum bound LOT approach can give inaccurate estimates of minimum
stress, leading to under-estimates in risking. The use of leak-off data is
reviewed in this paper. Examples of the effects of compartmentalization on pore
pressure-minimum stress relationships and
seal
integrity are given from the
Central North Sea.
AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005