Page 46 - Reservoir Geomechanics

30 Reservoir geomechanics

0

2000

4000

0.46 PSI/FT
PRESSURE
6000 ZONE
ONE

Depth (feet) 8000 PRESSURE 1.23 PSI/FT

ZONE
TWO
10000
PRESSURE
ZONE 3.71 PSI/FT
THREE

12000 S v

PRESSURE
ZONE 0.71 PSI/FT
FOUR
14000

l p = 0.91

16000
0 2000 4000 6000 8000 10000 12000 14000
Pressure (psi)

Figure 2.2. Pore pressure measurements in the Monte Cristo field, located onshore near the Gulf of
Mexico in south Texas (after Engelder and Leftwich 1997). Such data are typical of many
sedimentary basins in which overpressure is encountered at depth. Hydrostatic pore pressures is
observed to a certain depth (in this case ∼8300 ft), a transition zone is then encountered in which
pore pressure increases rapidly with depth (in this case at an apparent gradient of 3.7 psi/ft) and
extremely high pore pressures are observed at depths greater than ∼11,000 ft. AAPG C 1997
reprinted by permission of the AAPG whose permission is required for futher use.