Interval density pressure management methods

• US 9,765,583 B2
• Filed: 08/06/2015
• Issued: 09/19/2017
• 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
• Primary Examiner(s): Larkin, Daniel S
• Assistant Examiner(s): Megna Fuentes, Anthony W
• Application Number:
  US14/819,810
• Publication Number:
  US 20160002991A1
• Time in Patent Office: 775 Days
• Field of Search: 367 81- 86, 7315221-15222, 7315227, 7315251, 7315201
• 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 47/06 Measuring temperature or pressure
• CPC Class Codes: E21B 47/10 Locating fluid leaks, intrusions or movements
• CPC Class Codes: E21B 49/005 Testing the nature of borehole walls or the formation by using drilling mud or cutting data
• CPC Class Codes: E21B 7/00 Special methods or apparatus for drilling
• CPC Class Codes: G01V 9/00 Prospecting or detecting by methods not provided for in groups G01V1/00 - G01V8/00
• CPC Class Codes: G06F 15/00 Digital computers in general details G06F1/00 – G06F13/00; Data processing equipment in general

Abstract

A method for estimating equivalent top of fluid level or a theoretical surface annular back pressure in a subterranean wellbore includes acquiring first and second axially spaced pressure measurements in the wellbore. The pressure measurements may then be processed to compute the equivalent top of fluid level and/or theoretical surface annular back pressure 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 values corresponding to various wellbore intervals. The equivalent top of fluid level and/or theoretical surface annular back pressures may be used in automated managed pressure drilling operations.

Claims

1. A method for computing a theoretical surface annular back pressure in a subterranean wellbore during a managed pressure drilling operation, the method comprising:

(a) deploying a tool string in the wellbore, the tool string including first and second subsurface longitudinally spaced pressure sensors deployed at corresponding first and second measured depths in the wellbore;

(b) causing the first and second pressure sensors to acquire first and second annular drilling fluid pressure measurements at the first and second measured depths; and

(c) causing a processor to process the first and second pressure measurements to compute the theoretical surface annular back pressure for a wellbore interval between the first and second measured depths, wherein the theoretical surface annular back pressure is computed according to the following equation;

2. The method according to claim 1, wherein:

the tool string includes first, second, and third subsurface longitudinally spaced pressure sensors at corresponding first, second, and third measured depths;

(b) comprises causing the first, second, and third pressure sensors to acquire first, second, and third annular drilling fluid pressure measurements; and

(c) comprises processing the first, second, and third pressure measurements to compute a first theoretical surface annular back pressure for a wellbore interval between the first and second measured depths and a second theoretical surface annular back pressure for a wellbore interval between the second and third measured depths.

3. The method according to claim 1, wherein drilling fluid is being circulated in the tool string and the wellbore is being drilled in (b).

4. The method according to claim 1, wherein drilling fluid is static in the tool string in (b).

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

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

(d) acquiring a surface annular back pressure measurement; and

(e) adjusting a surface annular back pressure of the wellbore such that the measured surface annular backpressure in (d) is substantially equal to the theoretical surface annular back pressure computed in (c).

7. The method according to claim 6, wherein the surface annular back pressure is automatically adjusted in (e) via incrementally adjusting a choke position.

8. The method according to claim 6, further comprising:

(f) repeating (b), (c), (d), and (e) in a control loop such that surface annular back pressure is automatically adjusted in (e) in response to changes in the theoretical surface annular back pressure computed in (c).

9. The method according to claim 6, wherein:

the surface annular backpressure is automatically increased in response to an increase in the theoretical surface annular back pressure; and

the surface annular backpressure is automatically decreased in response to a decrease in the theoretical surface annular back pressure.

10. The method according to claim 9, wherein the surface annular backpressure is automatically increased in response to at least one of (i) a decrease in cuttings density while drilling, (ii) borehole washout, (iii) formation fluid flowing into the wellbore, and (iv) drilling fluid changes resulting in a decreased interval density.

11. The method according to claim 9, wherein the surface annular backpressure is automatically decreased in response to at least one of (i) an increase in cuttings density while drilling, (ii) a wellbore pack-off, (iii) lost circulation, and (iv) drilling fluid changes resulting in an increased interval density.