Patent ID: 7407019

Claim:
A method of dynamically controlling open hole pressure within a wellbore having a drill string positioned therein, the method comprising the steps of: (i) pumping a fluid down the drill string, into an annulus formed by the drill string and the interior of the wellbore, and then subsequently up the annulus to the surface of the ground, said fluid exiting said annulus and directed through a drilling rig choke to control the flow of fluid from the wellbore; (ii) selectively applying wellhead pressure to the annulus through selectively pumping an additional quantity of the fluid or a quantity of a secondary fluid across the annulus; and, (iii) controlling the application of wellhead pressure applied to the annulus by controlling the operation of a wellhead pressure control choke, said wellhead pressure control choke operated and connected to said annulus independent from said drilling rig choke, to thereby maintain open hole pressure within a desired range without adjusting said drilling rig choke.