Patent ID: 6823950
Filing Date: 2004-11-30
Classification: E21B

Abstract:
A method for controlling pressures during subsea well drilling operations in an earth formation, the steps comprising:(a) providing a weighted drilling fluid system, said fluid being pumped through a drilling string in the earth formation, the drilling fluid providing a hydrostatic pressure on the earth formation and returning to up an annulus between a borehole created by the drilling string and the drilling, as well as a drilling riser, the drilling fluid being returned to atmospheric pressure, cleaned, measured and reused; (b) performing a first leak off test by increasing pump pressure to determine a fracture opening pressure (FOP), an unstable fracture propagation pressure(UGP), a fracture propagation pressure (FPP), and a fracture closure pressure for the earth formation (FCP); (c) performing a second leak off test by increasing pump pressure to determine a fracture reopen pressure; and (d) performing drilling operations while maintaining pressure exerted by said drilling fluid on the earth formation in a range between said fracture reopen pressure and said fracture propagation pressure.