Underbalanced drilling through formations with varying lithologies

Patent metadata

Field	Value
Publication number	US-9784088-B2
Application number	US-201515035449-A
Country	US
Kind code	B2
Filing date	Jul 13, 2015
Priority date	Jul 13, 2015
Publication date	Oct 10, 2017
Grant date	Oct 10, 2017

Abstract

Bottom-hole pressure operating envelops for underbalanced drilling take into account the lithologies of the formations being drilled through.

First claim

What is claimed is:

1. A method comprising:
preparing a model to drill a borehole with a bottom hole assembly (“BHA”) through a plurality of formations comprising a first formation and a second formation;
defining:
a first-formation formation top to be a depth at which the BHA will enter the first formation,
a second-formation formation top to be a depth at which the BHA will enter the second formation, wherein the first-formation formation top is at a shallower depth than the second-formation formation top,
a first-formation lithography for the first formation, and
a second-formation lithography for the second formation;

computing with a processor a first-formation operating envelop at the first-formation top within which a first-formation-bottom-hole pressure (FFBHP) in a first-formation annular volume within the borehole adjacent to the BHA as the BHA passes through the first-formation top is in an underbalanced condition, wherein the first-formation operating envelop is computed as a function of the lithography of the first formation;
computing with the processor a second-formation operating envelop at the second-formation top within which a second-formation-bottom-hole pressure (SFBHP) in a second-formation annular volume within the borehole adjacent to the BHA as the BHA passes through the second-formation top is in an underbalanced condition, wherein the second-formation operating envelop is computed as a function of the lithography of the second formation;
drilling the borehole according to the model; and
adjusting drilling parameters:
to keep the FFBHP within the first-formation operating envelop when drilling through the first formation, and
to keep the SFBHP within the second-formation operating envelop when drilling through the second formation.

2. The method of claim 1 wherein FFBHP is a function of a plurality of drilling parameters and a slip velocity of first-formation cuttings produced by the BHA from the first formation as it passes through the first formation.

3. The method of claim 2 wherein the slip velocity of first-formation cuttings produced by the BHA from the first formation as it passes through the first-formation top is computed as a function of:
the dimensions of first-formation cuttings;
the particle apparent velocity of first-formation cuttings;
the shape, size, and sphericity of first-formation cuttings; and
the particle flow regime of first-formation cuttings.

4. The method of claim 2 wherein the plurality of drilling parameters comprises:
a liquid injection rate at which drilling fluids are injected into the well; and
a gas injection rate at which gas is injected into the well.

5. The method of claim 1 wherein SFBHP is a function of a plurality of drilling parameters and a slip velocity of second-formation cuttings produced by the BHA from the second formation as it passes through the second formation.

6. The method of claim 5 wherein the slip velocity of second-formation cuttings produced by the BHA from the second formation as it passes through the second-formation top is computed as a function of:
the dimensions of second-formation cuttings;
the particle apparent velocity of second-formation cuttings;
the shape, size, and sphericity of second-formation cuttings; and
the particle flow regime of second-formation cuttings.

7. The method of claim 6 wherein the particle flow regime of second-formation cuttings is selected from the group consisting of laminar flow and turbulent flow.

8. The method of claim 5 wherein the plurality of drilling parameters comprises:
a liquid injection rate at which drilling fluids are injected into the well; and
a gas injection rate at which gas is injected into the well.

9. A method comprising:
preparing a model to drill a borehole with a bottom hole assembly (“BHA”) through a plurality of formations comprising a first formation and a second formation;
defining:
a first depth to be a depth at which the BHA is passing through the first formation,
a second depth to be a depth at which the BHA is passing through the second formation, wherein the first depth is at a shallower depth than the second depth,
a first-formation lithography for the first formation, and
a second-formation lithography for the second formation;

computing with a processor a first-formation operating envelop within which a first-formation bottom hole pressure (“FFBHP”) in a first-formation annular volume within the well adjacent to the BHA as the BHA passes through the first formation in an underbalanced condition, wherein the first-formation operating envelop is computed as a function of the lithography of the first formation;
computing with the processor a second-formation operating envelop within which a second-formation bottom hole pressure (“SFBHP”) in a second-formation annular volume within the well adjacent to the BHA as the BHA passes through the second formation is in an underbalanced condition, wherein the second-formation operating envelop is computed as a function of the lithography of the second formation;
drilling the well according to the well-drilling plan; and
adjusting drilling parameters:
to keep the well within the first-formation operating envelop when drilling through the first formation, and
to keep the well within the second-formation operating envelop when drilling through the second formation.

10. The method of claim 9 wherein FFBHP is a function of a plurality of drilling parameters and a slip velocity of first-formation cuttings produced by the BHA from the first formation as it passes through the first formation.

11. The method of claim 10 wherein the slip velocity of first-formation cuttings produced by the BHA from the first formation as it passes through the first depth is computed as a function of:
the dimensions of first-formation cuttings;
the particle apparent velocity of first-formation cuttings;
the shape, size, and sphericity of first-formation cuttings; and
the particle flow regime of first-formation cuttings.

12. The method of claim 10 wherein the plurality of drilling parameters comprises:
a liquid injection rate at which drilling fluids are injected into the well; and
a gas injection rate at which gas is injected into the well.

13. The method of claim 9 wherein SFBHP is a function of a plurality of drilling parameters and a slip velocity of second-formation cuttings produced by the BHA from the second formation as it passes through the second formation.

14. The method of claim 13 wherein the slip velocity of second-formation cuttings produced by the BHA from the second formation as it passes through the second depth is computed as a function of:
the dimensions of second-formation cuttings;
the particle apparent velocity of second-formation cuttings;
the shape, size, and sphericity of second-formation cuttings; and
the particle flow regime of second-formation cuttings.

15. The method of claim 14 wherein the particle flow regime of second-formation cuttings is selected from the group consisting of laminar flow and turbulent flow.

16. The method of claim 13 wherein the plurality of drilling parameters comprises:
a liquid injection rate at which drilling fluids are injected into the well; and
a gas injection rate at which gas is injected into the well.

17. A non-transitory computer-readable medium, on which is recorded a computer program that, when executed, performs a method comprising:
preparing a model to drill a borehole with a bottom hole assembly (“BHA”) through a plurality of formations comprising a first for

Assignees

• Landmark Graphics Corp

Inventors

• Samuel Robello
• Morales-Ocando Gabriela M
• Aniket Aniket

Classifications

• E21B44/00 Primary

  Automatic control systems specially adapted for drilling operations, i.e. self-operating systems which function to carry out or modify a drilling operation without intervention of a human operator, e.g. computer-controlled drilling systems; Systems specially adapted for monitoring a plurality of drilling variables or conditions · CPC title

• E21B41/00

  Equipment or details not covered by groups E21B15/00 - E21B40/00 · CPC title

• E21B21/085 Primary

  Underbalanced techniques, i.e. where borehole fluid pressure is below formation pressure · CPC title

• E21B21/08

  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 title

• E21B41/0092

  Fixed Constructions · mapped topic