METHOD AND SYSTEM FOR IDENTIFYING A SELF-SUSTAINED INFLUX OF FORMATION FLUIDS INTO A WELLBORE

• US 20140110169A1
• Filed: 10/22/2013
• Published: 04/24/2014
• Est. Priority Date: 10/22/2012
• Status: Active Grant

• Current Assignee: Safekick Limited (Santos Vision Ltd.)
• Original Assignee: Helio Santos, Paul L. Sonnemann, Safekick Limited (Santos Vision Ltd.)
• Inventors: SANTOS, Helio, SONNEMANN, Paul L.
• Granted Patent: US 9,175,531 B2
• Time in Patent Office: Days
• US Class Current: 175/25
• 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 of identifying a self-sustained influx of formation fluids into a wellbore includes the steps of closing an annular shut-off device and diverting an annular return flow from the wellbore through a first flow rate measurement device, measuring a flow rate of said annular return flow, measuring an inlet flow rate of fluids entering the well through a second flow rate measurement device in a fluid injection line, and identifying a self-sustained influx of formation fluids if a non-decreasing measured annular return flow rate is greater than said measured inlet flow rate.

Claims

1. A method of identifying a self-sustained influx of formation fluids into a wellbore (12) being drilled in a formation (14), the method comprising the steps of:

closing an annular shut-off device (31) and diverting an annular return flow from the wellbore through a first flow rate measurement device (50, 58);

measuring a flow rate of said annular return flow;

measuring an inlet flow rate of fluids entering the well through a second flow rate measurement device (52) in a fluid injection line (48); and

identifying a self-sustained influx of formation fluids if a non-decreasing measured annular return flow rate is greater than said measured inlet flow rate.

2. The method of claim 1, further comprising reducing said inlet flow rate, and identifying a self-sustained influx of formation fluids if a non-decreasing measured annular return flow rate remains greater than said reduced inlet flow rate.

3. The method of claim 2, further comprising the steps of:

fully reducing said inlet flow rate to substantially zero, and identifying a self-sustained influx of formation fluids if a non-decreasing measured annular return flow rate remains greater than said fully reduced inlet flow rate.

4. The method of claim 3, further comprising the step of:

ruling out the presence of a self-sustained influx of formation fluids if said measured annular return flow rate decreases to substantially zero.

5. The method of claim 1, further comprising:

generating a signal F_out(t) representative of said annular return flow rate;

generating a signal F_in(t) representative of said inlet flow rate; and

transmitting said signals F_in(t) and F_out(t) to a central control unit, which receives said signals F_in(t) and F_out(t) and computes a delta between said signals F_in(t) and F_out(t).

6. The method of claim 5, further comprising the step of increasing back pressure on said annular return flow using a flow control device when a self-sustained influx is identified.

7. The method of claim 6, further comprising the step of increasing back pressure on said annular return flow by an amount required to decrease said annular return flow indicated by signal F_out(t) to substantially the same as said inlet flow rate indicated by signal F_in(t).

8. The method of claim 7, further comprising the step of automatically increasing back pressure on said annular return flow by said central control unit.

9. The method of claim 4, further comprising the step of reopening the annular shut-off device after ruling out the presence of a self-sustained influx of formation fluids into the wellbore.

10. The method of claim 1, further comprising the step of stopping rotation of a drillstring (20) and lifting said drillstring off a well bottom.

11. In a well monitoring system (10) comprising:

an annular shut-off device (31) arranged to close a wellbore annulus (18) of the well (12) from atmosphere;

a flow control device line (56) coupled between said wellbore annulus and a surface fluid reservoir (42), said flow control device line including a flow control device (70);

a fluid injection line (48) in fluid communication with an upper end (24) of the drillstring;

an inlet flow rate measurement device (52) disposed in said fluid injection line, said inlet flow rate measurement device arranged to measure a flow rate in said fluid injection line and to generate a signal F_in(t) representative of actual fluid injection line flow rate as a function of time (t);

a flow check line (57) disposed downhole from said annular shut-off device and coupled between said wellbore annulus and said surface fluid reservoir; and

an outlet flow rate measurement device (58) disposed in said flow check line, said outlet flow rate measurement device arranged to measure flow rate in said flow check line and to generate a signal F_out(t) representative of actual flow check line flow rate as a function of time (t),

a well monitoring method comprising the steps of,

closing said annular shut-off device and diverting an annular return flow from the wellbore through said flow check line and outlet flow rate measurement device;

measuring a flow rate of said annular return flow with said outlet flow rate measurement device;

measuring an inlet flow rate of fluids entering the well with said inlet flow rate measurement device; and

identifying a self-sustained influx of formation fluids if a non-decreasing measured annular return flow rate is greater than said measured inlet flow rate.

12. The method of claim 11, further comprising the steps of reducing said inlet flow rate, and identifying a self-sustained influx of formation fluids if a non-decreasing measured annular return flow rate remains greater than said reduced inlet flow rate.

13. The method of claim 12, further comprising the steps of:

fully reducing said inlet flow rate to substantially zero, and identifying a self-sustained influx of formation fluids if said measured annular return flow rate remains greater than said fully reduced inlet flow rate.

14. The method of claim 13, further comprising the step of:

ruling out the presence of a self-sustained influx of formation fluids if said measured annular return flow rate decreases to substantially zero.

15. The method of claim 11, further comprising:

generating a signal F_out(t) representative of said annular return flow rate;

generating a signal F_in(t) representative of said inlet flow rate; and

transmitting said signals F_in(t) and F_out(t) to a central control unit, which receives said signals F_in(t) and F_out(t) and computes a delta between said signals F_in(t) and F_out(t).

16. The method of claim 15, further comprising the step of increasing back pressure on said annular return flow using a flow control device disposed in said flow check line when a self-sustained influx is identified.

17. The method of claim 16, further comprising the step of increasing back pressure on said annular return flow by an amount required to decrease said annular return flow indicated by signal F_out(t) to substantially the same as said inlet flow rate indicated by signal F_in(t).

18. The method of claim 17, further comprising the step of automatically increasing back pressure on said annular return flow by said central control unit.

19. The method of claim 14, further comprising the step of reopening the annular shut-off device after ruling out the presence of a self-sustained influx of formation fluids into the wellbore.

20. The method of claim 11, further comprising the step of stopping rotation of a drillstring (20) and lifting said drillstring off a well bottom.

21. A well monitoring system (10) comprising:

an annular shut-off device (31) arranged to close a wellbore annulus (18) of the well (12) from atmosphere;

a flow control device line (56) coupled between said wellbore annulus and a surface fluid reservoir (42), said flow control device line including a flow control device (70);

a fluid injection line (48) in fluid communication with an upper end (24) of the drillstring (20);

an inlet flow rate measurement device (52) disposed in said fluid injection line, said inlet flow rate measurement device arranged to measure a flow rate in said fluid injection line and to generate a signal F_in(t) representative of actual fluid injection line flow rate as a function of time (t);

a flow check line (57) disposed downhole from said annular shut-off device and coupled between said wellbore annulus and said surface fluid reservoir;

an outlet flow rate measurement device (58) disposed in said flow check line, said outlet flow rate measurement device arranged to measure flow rate in said flow check line and to generate a signal F_out(t) representative of actual flow check line flow rate as a function of time (t);

a central control unit arranged to receive said signals F_out(t) and F_in(t) and compute a delta between said signals F_out(t) and F_in(t); and

a graphical user interface displaying said signals F_out(t) and F_in(t),

wherein a self-sustained influx is identifiable on said graphical user interface to an operator if said displayed non-decreasing signal F_out(t) remains greater than said displayed signal F_in(t).

22. The system of claim 21, further comprising a flow control device (59) in said flow check line, said flow control device arranged to increase back pressure on said annular return flow.