reservoir geomecanics

218 Reservoir geomechanics
a.
-400 0 400 0 50 100 15.5 16 16.5
b.
Figure 7.6. Pressure-while-drilling (PWD) records reconstructed from a well in the Gulf of
Mexico. (a) A conventional pressure record indicating an abrupt decrease in pressure when
pumping is stopped to make a connection while adding a new piece of pipe while drilling. (b) An
example of wellbore ballooning where there is a gradual decrease in pressure when pumping is
stopped and a corresponding gradual increase in pressure when pumping resumes (see text).