Title:
METHOD AND APPARATUS FOR CONTROLLING BOTTOM-HOLE PRESSURE DURING DUAL-GRADIENT DRILLING
Document Type and Number:
WIPO Patent Application WO2002068787
Kind Code:
A3
Abstract:
A method for controlling wellbore pressure in a wellbore during drilling. The method includes operating a drilling system to have a first fluid pressure gradient inside a drillstring (2) extending from the earth's surface to a drill bit (4) at the bottom of the wellbore. The drilling system has a second fluid pressure gradient lower than the first fluid pressure gradient in an annular space between the drillstring (2) and the wellbore from a selected depth in the wellbore to the earth's surface. Introduction of drilling fluid to the inside of the drillstring is stopped, and fluid flow in the annular space from a point below the selected depth to a point above the selected depth is selectively controlled (44) to cause a substantially constant fluid pressure at a predertermined depth in the wellbore.
Inventors:
MAUS L DONALD
Application Number:
PCT/US2002/004890
Publication Date:
February 20, 2003
Filing Date:
February 20, 2002
Export Citation:
Assignee:
EXXONMOBIL UPSTREAM RES CO (US)
International Classes:
E21B21/08; E21B21/10; E21B21/00; (IPC1-7): E21B43/01; E21B7/12
Foreign References:
| US4046191A | 1977-09-06 | |||
| US4813495A | 1989-03-21 | |||
| US3815673A | 1974-06-11 | |||
| US6328107B1 | 2001-12-11 |
Download PDF: