Patent ID: 7836973

Claim:
A method for drilling a wellbore, comprising acts of: drilling the wellbore by injecting drilling fluid through a tubular string disposed in the wellbore, the tubular string comprising a drill bit disposed on a bottom thereof, wherein: the drilling fluid exits the drill bit and carries cuttings from the drill bit, and the drilling fluid and cuttings (returns) flow to a surface of the wellbore via an annulus defined by an outer surface of the tubular string and an inner surface of the wellbore; and while drilling the wellbore: measuring a first annulus pressure (FAP) using a pressure sensor attached to a casing string hung from a wellhead of the wellbore; continuously transmitting the FAP measurement to the surface using a high-bandwidth medium; continuously selecting at least a portion of a formation exposed to the annulus having a minimum fracture gradient relative to fracture gradients of other exposed portions or formations; continuously calculating a second annulus pressure (SAP) exerted on the portion; continuously comparing the SAP to a fracture pressure of the portion; and controlling the SAP to be less than the fracture pressure of the portion.