METHODS FOR EVALUATING INFLOW AND OUTFLOW IN A SUBTERRAEAN WELLBORE

• US 20160376886A1
• Filed: 06/22/2016
• Published: 12/29/2016
• Est. Priority Date: 08/26/2011
• Status: Active Grant

• Current Assignee: Schlumberger Technology Corporation (Schlumberger NV)
• Original Assignee: Schlumberger Technology Corporation (Schlumberger NV)
• Inventors: Rasmus, John, Lesso, William, James, John
• Granted Patent: US 10,190,407 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• 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 34/06 in wells
• CPC Class Codes: E21B 43/12 Methods or apparatus for controlling the flow of the obtained fluid to or in wells E21B43/25 takes precedence; valve arrangements E21B34/00
• CPC Class Codes: E21B 47/04 Measuring depth or liquid level
• CPC Class Codes: E21B 47/06 Measuring temperature or pressure
• CPC Class Codes: E21B 47/10 Locating fluid leaks, intrusions or movements
• CPC Class Codes: E21B 49/003 by analysing drilling variables or conditions E21B49/005 takes precedence; systems specially adapted for monitoring a plurality of drilling variables or conditions E21B44/00
• CPC Class Codes: E21B 49/0875 determining specific fluid parameters
• CPC Class Codes: G01V 3/38 Processing data, e.g. for analysis, for interpretation, for correction

Abstract

A method for evaluating inflow or outflow in a subterranean wellbore includes acquiring first and second axially spaced pressure measurements in the wellbore. The pressure measurements may then be processed to obtain an interval density of drilling fluid between the measurement locations. A tool string including a large number of axially spaced pressure sensors (e.g., four or more or even six or more) electronically coupled with a surface processor via wired drill pipe may be used to obtain a plurality of interval densities corresponding to various wellbore intervals. The interval density may be measured during static conditions or while drilling and may be further processed to compute a density of an inflow constituent in the annulus. Changes in the computed interval density with time may be used as an indicator of either an inflow event or an outflow event.

Claims

1. A method for identifying an inflow event in a subterranean wellbore, the method comprising:

(a) processing a plurality of axially spaced annular pressure measurements to compute a plurality of annular interval densities;

(b) monitoring the computed annular interval densities with time; and

(c) evaluating a decrease in at least one of the annular interval densities or an increase in a differential flow rate as an indicator of an inflow event.

2. The method according to claim 1, wherein the annular interval densities comprise a measured annular interval circulating density and a measured annular interval static density.

3. The method according to claim 2, wherein:

the measured annular interval circulating density decreases below a modeled annular interval circulating density in (c); and

the measured annular interval static density decreases below a modeled annular interval static density in (c).

4. The method of claim 2, wherein (c) further comprises evaluating a decrease in at least one of the annular interval densities moving up the wellbore with time as a further indicator of an inflow event.

5. The method of claim 2, further comprising:

(d) processing the measured annular interval static density and the differential flow rate to compute a density of an inflow constituent.

6. The method according to claim 2, wherein:

(a) further comprises processing the plurality of annular pressure measurements to compute a plurality of equivalent top of fluid levels;

(b) further comprises monitoring the equivalent top of fluid levels with time; and

(c) further comprises evaluating a negative equivalent top of fluid level as a further indicator of the inflow event.

7. The method according to claim 2, wherein:

(a) further comprises processing the plurality of annular pressure measurements to compute a plurality of annular surface back pressures;

(b) further comprises monitoring the annular surface back pressures with time; and

(c) further comprises evaluating a positive annular surface back pressure as a further indicator of the inflow event.

14. The method according to claim 1, wherein when an inflow event is indicated, an annular choke is employed to keep the pressure within a set range.

15. The method according to claim 1, wherein when an inflow event is indicated, heavy mud is pumped downhole.

16. The method according to claim 15, further comprising evaluating an increase in at least one of the annular interval densities or a decrease in a differential flow rate as an indicator that the inflow event has stopped.

17. The method according to claim 16, wherein when the inflow event has stopped, pumping of heavy mud downhole is stopped.

18. The method according to claim 1, wherein a decrease of interval static density as a function of time and decreasing depth is an indicator of an inflow event.

19. The method according to claim 2, wherein a decrease of the equivalent top fluid level as a function of time is an indicator of an inflow event.

20. The method according to claim 1, wherein an increase of the computed back pressure as a function of time is an indicator of an inflow event or the decrease of the annular pressure as a function of time is an indicator of an inflow event.

8. A method for identifying an outflow event in a subterranean wellbore, the method comprising:

(a) processing a plurality of axially spaced annular pressure measurements to compute a plurality of annular interval densities;

(b) monitoring the computed annular interval densities with time; and

(c) evaluating a decrease in at least one of the annular interval densities or a decrease in a differential flow rate as an indicator of an outflow event.

9. The method according to claim 8, wherein the annular interval densities comprise a measured annular interval circulating density and a measured annular interval static density.

10. The method according to claim 9, wherein:

the measured annular interval circulating density decreases below a modeled annular interval circulating density in an interval including a liquid level; and

the measured annular interval static density decreases below a modeled annular interval static density in an interval including the liquid level.

11. The method of claim 9, wherein (c) further comprises evaluating a decrease in at least one of the annular interval densities moving down the wellbore with time as a further indicator of the outflow event.

12. The method according to claim 9, wherein:

(a) further comprises processing the plurality of annular pressure measurements to compute a plurality of equivalent top of fluid levels;

(b) further comprises monitoring the equivalent top of fluid levels with time; and

(c) further comprises evaluating an increase in the equivalent top of fluid levels below a liquid level as a further indicator of the outflow event.

13. The method according to claim 9, wherein:

(a) further comprises processing the plurality of annular pressure measurements to compute a plurality of annular surface back pressures;

(b) further comprises monitoring the annular surface back pressures with time; and

(c) further comprises evaluating an increase in the annular surface back pressures below a liquid level as a further indicator of the outflow event.