METHODS FOR EVALUATING INFLOW AND OUTFLOW IN A SUBTERRAEAN WELLBORE

• US 20130090855A1
• Filed: 08/14/2012
• Published: 04/11/2013
• 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 9,394,783 B2
• Time in Patent Office: Days
• US Class Current: 702/9
• 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 computing a density of an inflow constituent in a subterranean wellbore, the method comprising:

(a) acquiring first and second subsurface annular pressure measurements at corresponding first and second measured depths in the wellbore;

(b) causing a processor to process the first and second annular pressure measurements to compute an annular interval density between the first and second measured depths in the wellbore; and

(c) causing the processor to process the annular interval density and a differential flow rate to compute the density of the inflow constituent.

2. The method according to claim 1, wherein:

(a) further comprises acquiring first, second, and third annular pressure measurements at corresponding first, second, and third measured depths in the wellbore;

(b) further comprises causing the processor to process the first, second, and third annular pressure measurements to compute first and second annular interval densities, the first annular interval density between the first and second measured depths and the second annular interval density between the second and third measured depths; and

(c) further comprises causing the processor to process the first and second annular interval densities and the differential flow rate to compute first and second densities of the inflow constituent, the first density of the inflow constituent between the first and second measured depths and the second density of the inflow constituent between the second and third measured depths.

3. The method according to claim 1, wherein the first and second annular pressure measurements are acquired in (a) while drilling the subterranean wellbore.

4. The method according to claim 1, wherein the annular pressure measurements are acquired at a surface processor in (a) via a wired drill pipe communications channel.

5. The method of claim 1, wherein the differential flow rate is a difference between a flow rate out of an annular region of the wellbore and a flow rate into a tool string deployed in the wellbore.

6. The method according to claim 1, wherein (c) further comprises processing the annular interval density, the differential flow rate, a volume fraction of drilling fluid in the annular region, a density of the drilling fluid in an annular region of the wellbore, a volume fraction of cuttings in the annular region, and a density of cuttings in the annular region to compute the density of the inflow constituent.

7. The method according to claim 6, wherein the density of the inflow constituent is computed according to the following mathematical equation:

8. The method according to claim 6, wherein the density of the drilling fluid in the annular region is acquired from a hydraulics model.

9. The method according to claim 6, wherein the volume fraction of drilling fluid, the volume fraction of cuttings, and volume fraction of the inflow constituent in the annular region are estimated from a drilling fluid flow rate, a rate of penetration of drilling, and the differential flow rate.

10. The method according to claim 1, further comprising:

(d) evaluating the density of the inflow constituent computed in (c) to identify the inflow constituent.

11. The method according to claim 10, wherein a density of the inflow constituent less than about 0.6 indicates a gaseous inflow constituent, a density of the inflow constituent in a range from about 0.6 to about 0.8 indicates an oil inflow constituent, and a density of the inflow constituent greater than about 1 indicates a connate water inflow constituent.

12. 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 and an increase in a differential flow rate as an indicator of an inflow event.

13. The method according to claim 12, wherein the annular interval densities comprise a measured annular interval circulating density and a measured annular interval static density.

14. The method according to claim 13, 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).

15. The method of claim 13, 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.

16. The method of claim 13, further comprising:

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

17. The method according to claim 13, 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.

18. The method according to claim 13, 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.

19. 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 and a decrease in a differential flow rate as an indicator of an outflow event.

20. The method according to claim 19, wherein the annular interval densities comprise a measured annular interval circulating density and a measured annular interval static density.

21. The method according to claim 20, 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.

22. The method of claim 20, 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.

23. The method according to claim 20, 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.

24. The method according to claim 20, 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.