Pressure Safety System for Use With a Dynamic Annular Pressure Control System

• US 20070246263A1
• Filed: 04/19/2007
• Published: 10/25/2007
• Est. Priority Date: 04/20/2006
• Status: Abandoned Application

• Current Assignee: At-Balance Americas LLC (SLB)
• Original Assignee: At-Balance Americas LLC (SLB)
• Inventors: Reitsma, Donald G.
• Application Number:
  US11/737,163
• Publication Number:
  US 20070246263A1
• Time in Patent Office: Days
• US Class Current: 175/38
• CPC Class Codes: E21B 21/06 Arrangements for treating drilling fluids outside the borehole
• CPC Class Codes: E21B 21/08 Controlling or monitoring pressure or flow of drilling fluid, e.g. automatic filling of boreholes, automatic control of bottom pressure valve arrangements therefor E21B21/10
• CPC Class Codes: E21B 21/10 Valve arrangements in drilling-fluid circulation systems

Abstract

A method for controlling formation pressure during the drilling of a borehole through a subterranean formation includes selectively pumping a drilling fluid through a drill string extended into a borehole, out a drill bit at the bottom end of the drill string, and into an annular space between drill string and the borehole. The drilling fluid is discharged to a reservoir to clean the drilling fluid for reuse. Annular space fluid pressure is selectively increased to maintain a selected fluid pressure proximate the bottom of the borehole by applying fluid pressure to the annular space. The selective increasing includes controlling an aperture of an orifice operatively coupled between the annular space and the reservoir. Fluid from the annular space is discharged other than through the orifice when the annular space fluid pressure exceeds a selected value, or drops below a selected value.

Claims

1. A method for controlling formation pressure during the drilling of a borehole through a subterranean formation, comprising:

selectively pumping a drilling fluid through a drill string extended into a borehole, out a drill bit at the bottom end of the drill string, and into an annular space between drill string and the borehole;

discharging the drilling fluid to a reservoir to clean the drilling fluid for reuse;

selectively increasing annular space fluid pressure to maintain a selected fluid pressure proximate the bottom of the borehole by applying fluid pressure to the annular space, the selective increasing including controlling an aperture of an orifice operatively coupled between the annular space and the reservoir; and

discharging fluid from the annular space other than through the orifice when the annular space fluid pressure exceeds a selected value or drops below a selected value.

2. The method of claim 1 wherein the discharging comprises opening a pressure relief valve when the fluid pressure in the annular space exceeds a preselected fraction of a formation integrity test pressure.

3. The method of claim 2 wherein the preselected fraction is between about 80 to 90 percent of the formation integrity test pressure.

4. The method of claim 1 further comprising operating a safety valve if the fluid pressure in the annular space falls below a selected value.

5. The method of claim 4 wherein the operating the safety valve comprises stopping fluid flow to the orifice.

6. The method of claim 4 wherein the operating the safety valve comprises diverting fluid flow from the orifice to a backup selectively controllable orifice.

7. A method for controlling formation pressure during the drilling of a borehole through a subterranean formation, comprising:

selectively pumping a drilling fluid through a drill string extended into a borehole, out a drill bit at the bottom end of the drill string, and into an annular space between drill string and the borehole;

discharging the drilling fluid to a reservoir to clean the drilling fluid for reuse;

selectively increasing annular space fluid pressure to maintain a selected fluid pressure proximate the bottom of the borehole by applying fluid pressure to the annular space, the selective increasing including controlling an aperture of an orifice operatively coupled between the annular space and the reservoir; and

operating a safety valve if the fluid pressure in the annular space falls below a selected value.

8. The method of claim 7 wherein the operating the safety valve comprises stopping fluid flow to the orifice.

9. The method of claim 7 wherein the operating the safety valve comprises diverting fluid flow from the orifice to a backup selectively controllable orifice.

10. The method of claim 7 further comprising causing fluid to flow other than through the orifice if the fluid pressure in the annular space increases above a selected value.

11. The method of claim 10 wherein the causing fluid flow comprises opening a pressure relief valve.

12. The method of claim 11 wherein the pressure relief valve is caused to operate when the fluid pressure reaches a preselected fraction of a formation integrity test pressure.

13. The method of claim 12 wherein the preselected fraction is between about 80 to 90 percent of the formation integrity test pressure.