Page 78 - Drilling Technology in Nontechnical Language
P. 78
Chapter 3 – DRILLING A LAND EXPLORATION WELL 69
the hydrostatic pressure exerted at the bottom of the well is 0.5 psi/
ft × 1,000 ft = 500 psi (11.3 kPa/m × 305 m = 3,446 kPa). If the final
surface pressure was 230 psi (1,586 kPa), the total pressure on the formation
downhole is 730 psi (5,032 kPa). This pressure must not be exceeded (and
preferably not even approached closely) because if the formation fractures
under pressure, fluids might travel outside the casing to the surface. If the
load-bearing capacity of the surface soil is reduced, it could cause the rig
to collapse, endangering lives.
Fig. 3–18. Drilling out to test formation strength
_Devereux_Book.indb 69 1/16/12 2:07 PM
