Methods for evaluating borehole volume changes while drilling

Patent metadata

Field	Value
Publication number	US-9404327-B2
Application number	US-201213585601-A
Country	US
Kind code	B2
Filing date	Aug 14, 2012
Priority date	Aug 26, 2011
Publication date	Aug 2, 2016
Grant date	Aug 2, 2016

Abstract

A method identifying a wellbore volume change while drilling a subterranean wellbore includes acquiring first and second axially spaced pressure measurements in the wellbore. The wellbore volume change may include, for example, a borehole washout or a borehole pack-off. 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 densities may be measured while drilling and may be further evaluated as an indicator of a wellbore volume change.

First claim

What is claimed is:

1. A method for identifying a borehole washout event while drilling a subterranean wellbore, the method comprising:
(a) pumping drilling fluid through a drill string located in a subterranean wellbore, the drill string including a plurality of axially spaced along string pressure sensors, said pumping operative to create a downstream flow rate in the drill string and an upstream flow rate in an annulus external to the drill string;
(b) rotating a drill bit deployed on an end of the drill string, said rotating operative to drill the subterranean wellbore;
(c) using the plurality of along string pressure sensors to make a corresponding plurality of subsurface annular pressure measurements at a corresponding plurality of measured depths while drilling in (a) and (b);
(d) transmitting the plurality of pressure measurements to a processor;
(e) causing the processor to process the plurality of measurements made in (c) to compute a plurality of annular interval densities;
(f) monitoring the plurality of annular interval densities computed in (e) with time while drilling in (a) and (b); and
(g) evaluating (i) a decrease in at least one of the annular interval densities and a substantially constant differential flow rate between the downstream and upstream flow rates as an indicator of the borehole washout and (ii) evaluating a decrease in a measured annular interval static density obtained by removing annular friction effects from the measured annular interval circulating density below a modeled annular interval static density as a further indicator of the borehole washout.

2. The method of claim 1 , further comprising:
(h) computing a new borehole diameter in the at least one depth interval such that the modeled annular interval circulating density is substantially equal to the measured annular interval circulating density.

3. The method according to claim 1 , wherein (g) further comprises evaluating a measured annular interval static density being substantially equal to a modeled annular interval static density as a further indicator of the borehole washout.

4. The method according to claim 1 , wherein:
(e) further comprises causing the processor to process the plurality of annular pressure measurements to compute a plurality of equivalent top of fluid levels;
(f) further comprises monitoring the equivalent top of fluid levels with time; and
(g) further comprises evaluating a decreasing circulating equivalent top of fluid level as a further indicator of the borehole washout.

5. The method according to claim 1 , wherein:
(e) further comprises causing the processor to process the plurality of annular pressure measurements to compute a plurality of annular surface back pressures;
(f) further comprises monitoring the annular surface back pressures with time; and
(g) further comprises evaluating an increasing circulating annular surface back pressure as a further indicator of the borehole washout.

6. A method for identifying a borehole pack-off while drilling a subterranean wellbore, the method comprising:
(a) pumping drilling fluid through a drill string located in a subterranean wellbore, the drill string including a plurality of axially spaced along string pressure sensors, said pumping operative to create a downstream flow rate in the drill string and an upstream flow rate in an annulus external to the drill string;
(b) rotating a drill bit deployed on an end of the drill string, said rotating operative to drill the subterranean wellbore;
(c) using the plurality of along string pressure sensors to make a corresponding plurality of subsurface annular pressure measurements at a corresponding plurality of measured depths while drilling in (a) and (b);
(d) transmitting the plurality of pressure measurements to a processor;
(e) causing the processor to process the plurality of measurements made in (c) to compute a plurality of annular interval densities;
(f) monitoring the plurality of annular interval densities computed in (e) with time while drilling in (a) and (b); and
(g) evaluating (i) an increase in at least one of the annular interval densities and a substantially constant differential flow rate between the downstream and upstream flow rates as an indicator of the borehole pack-off and (ii) evaluating an increase in a measured annular interval static density obtained by removing annular friction effects from the measured annular interval circulating density above a modeled annular interval static density as a further indicator of the borehole pack-off.

7. The method according to claim 6 , wherein (g) further comprises evaluating a measured annular interval static density being substantially equal to a modeled annular interval static density as a further indicator of the borehole pack-off.

8. The method according to claim 6 , wherein:
(e) further comprises causing the processor to process the plurality of annular pressure measurements to compute a plurality of equivalent top of fluid levels;
(f) further comprises monitoring the equivalent top of fluid levels with time; and
(g) further comprises evaluating an increasing circulating equivalent top of fluid level as a further indicator of the borehole pack-off.

9. The method according to claim 6 , wherein:
(e) further comprises causing the processor to process the plurality of annular pressure measurements to compute a plurality of annular surface back pressures;
(f) further comprises monitoring the annular surface back pressures with time; and
(g) further comprises evaluating a decreasing circulating annular surface back pressure as a further indicator of the borehole pack-off.

10. The method of claim 6 , further comprising:
(h) evaluating a change in a measured annular interval circulating density to estimate an axial location of the borehole pack-off, the measured annular interval circulating density increasing above a modeled annular interval circulating density below the pack-off and being substantially equal to the modeled annular interval circulating density above the pack-off.

11. A method for identifying annular cuttings drop out while drilling a subterranean wellbore, the method comprising:
(a) pumping drilling fluid through a drill string located in a subterranean wellbore, the drill string including a plurality of axially spaced along string pressure sensors, said pumping operative to create a downstream flow rate in the drill string and an upstream flow rate in an annulus external to the drill string;
(b) rotating a drill bit deployed on an end of the drill string, said rotating operative to drill the subterranean wellbore;
(c) using the plurality of along string pressure sensors to make a corresponding plurality of subsurface annular pressure measurements at a corresponding plurality of measured depths while drilling in (a) and (b);
(d) transmitting the plurality of pressure measurements to a processor;
(e) causing the processor to process the plurality of measurements made in (c) to compute a plurality of measured annular interval densities and a plurality of measured annular interval circulating densities;
(f) monitoring the plurality of measured annular interval static densities and the measured annular interval circulating densities computed in (e) with time while drilling in (a) and (b);
(g) evaluating (i) a decrease in at least one of the measured annular interval static densities below a modeled annular interval static density, (ii) a decrease in at least one of the measured annular interval circulating densities below a modeled annular interval circulating density, and (iii) a substantially constant differential flow rate between the downstream flow rate and the upstream f

Assignees

• Rasmus John
• Lesso William
• James John
• Schlumberger Technology Corp

Inventors

• Rasmus John
• Lesso William
• James John

Classifications

• E21B7/00

  Special methods or apparatus for drilling · CPC title

• G06F15/00

  Digital computers in general (details G06F1/00 – G06F13/00); Data processing equipment in general · CPC title

• E21B47/10

  Locating fluid leaks, intrusions or movements · CPC title

• G01V9/00

  Prospecting or detecting by methods not provided for in groups G01V1/00 - G01V8/00 · CPC title

• E21B21/08 Primary

  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 title