Pressure Cell
Mapping as a Tool for Evaluating Remaining Exploration Potential:
Example
from
the Pre-Cretaceous Series in the
Central
Graben
,
Point, Olivier1, Thierry Dugoujard2, Neville Taylor2, Thierry Rives3, Michel Sacleux4 (1) Total E&P Norge AS, Stavanger, Norway (2) Total E&P UK PLC, Aberdeen, United Kingdom (3) TOTAL SA, Pau, France (4) Total SA, Paris La Defense, France
In the
Central
Graben
area of the
top
seal
integrity is overcome.
Top
seal
breaching results in
partial leakage, known in some fields of the area, but can also lead to
complete emptying for other structures.
The purchase of the 3D PGS seismic Megasurvey
allowed TOTAL E&P
Central
Graben
province, which aimed at identifying
the remaining exploration potential and assessing the value of undeveloped
discoveries. In the process of assessing risks of identified leads and
prospects, particular attention was given to pressure analysis. Mesozoic
reservoirs are frequently overpressured with a
pressure transition zone commencing in the Chalk. Fracture gradients were
determined at a regional
top
seal
breaching. A comprehensive pressure database was also used to build a pressure
cell map. Pressure cells are bounded by major structural features (basement
faults, salt ridges,…) which result from the rift
history of the
Central
Graben
province.
Practical
examples of use of this method include evaluation of remaining potential updip of a dry Fulmar well and assessment of
top
seal
capacity for a variety of Mesozoic prospects. In addition to
top
seal
retention
capacity, lateral and vertical compartmentalisation
risks were also investigated using pressure analysis. Pressure cell mapping
proved to be a very useful tool for residual exploration in a highly mature
area.