Page 53 - Reservoir Geomechanics

37 Pore pressure at depth in sedimentary basins

a.
6000 OVERBURDEN SAND 1
psi
5000
INITIAL
CONDITIONS
4000
A-7
Pp
3000 Hydrostat. B-4
A-8
2000 A-10 A-12
A-6

1000
1970 1972 1974 1976 1978 1980 1982 1984 1986 1988 1990 1992

Production year

b.
OVERBURDEN SAND 2
6000
psi INITIAL A-4 A-8
CONDITIONS
A-1
5000 A-1ST

4000 A-10

3000 Pp Hydrostat.

2000
1984 1986 1988 1990 1992 1994
Production year

Figure 2.9. Production-induced pore pressure variations within two reservoirs in the South Eugene
Island field, Gulf of Mexico (modified after Finkbeiner 1998). (a) Sand 1 appears to behave as a
fully interconnected reservoir. Production from the first wells in the field causes pressure to drop
from moderately overpressure values to sub-hydrostatic. (b) Production from Sand 2 demonstrates
that this reservoir appears to be compartmentalized. The pressure decline associated with
production from well A-1 was not sensed in the sections of the reservoir penetrated by the other
wells. Instead, A-4, A-8 and A-1ST appear to have penetrated essentially undepleted sections of the
reservoir.