Method and apparatus for determining potential interfacial severity for a formation

• US 6,353,799 B1
• Filed: 02/23/2000
• Issued: 03/05/2002
• Est. Priority Date: 02/24/1999
• Status: Expired due to Term

• Current Assignee: Baker Hughes Incorporated (Baker Hughes Company)
• Original Assignee: Baker Hughes Incorporated (Baker Hughes Company)
• Inventors: Cooley, Craig Hodges, Curry, David Alexander, Ledgerwood, Leroy William III, Meany, Nigel Charles
• Primary Examiner(s): McElheny, Jr., Donald E.
• Application Number:
  US09/511,618
• Time in Patent Office: 741 Days
• Field of Search: 702/9, 702/11, 702/12, 702/13, 702/16, 702/7, 702/8, 173/6, 703/10, 367/73, 731/520.3, 731/520.5, 175/24, 175/26, 175/50, 175/48
• US Class Current: 702/9
• CPC Class Codes: E21B 2200/22 Fuzzy logic, artificial intelligence, neural networks or the like
• CPC Class Codes: E21B 44/00 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 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

Abstract

A method and apparatus are provided for generating an indicator of potential for abrupt changes in rock strength in a particular wellbore. Forensic wellbore data is obtained from at least one previously drilled wellbore which is determined to be comparable to the target wellbore. An interfacial severity computer program is provided. The program consists of executable program instructions. It is adapted to utilize a plurality of wellbore parameters, including at least one forensic wellbore data element. The interfacial severity computer program is loaded onto a data processing system. At least the forensic wellbore data, and possibly other wellbore parameter data elements, are supplied as an input to the interfacial severity computer program. The data processing system is utilized to execute program instructions of the interfacial severity computer program. This applies the inputs to the interfacial severity computer program which produces an output and indicator of the potential for abrupt changes in rock strength in the particular target wellbore.

Claims

1. A method of providing an indicator of potential for abrupt changes in rock strength in a particular wellbore, comprising:

(a) obtaining forensic wellbore data from at least one previously drilled wellbore which is determined to be comparable to said particular wellbore;

(b) providing an interfacial severity computer program consisting of executable program instructions, and adapted to utilize said forensic wellbore data;

(c) loading said interfacial severity computer program on to a data processing system;

(d) supplying as an input to said interfacial severity computer program said forensic wellbore data; and

(e) utilizing said data processing system to execute program instructions of said interfacial severity computer program to apply said input to said interfacial severity computer program and to produce as an output for a particular predefined interval an indicator of potential for abrupt changes in rock strength in said particular wellbore which utilizes at least one of the following types of measures of rock strength;

(1) a measure of relative magnitudes of changes in rock strength over said predefined interval;

(2) a measure of rock strength for each rock forming an interface of differing rocks over said predefined interval; and

(3) a measure of frequency of changes of rock strength over said predefined interval.

2. The method of providing an indicator of potential for abrupt changes in rock strength according to claim 1, further comprising:

(f) obtaining empirical wellbore data from said particular wellbore during drilling operations; and

(g) additionally supplying said empirical wellbore data as an input to said interfacial severity computer program.

3. The method of providing an indicator of potential for abrupt changes in rock strength according to claim 1, wherein said forensic wellbore data includes at least log data relating to formation strength.

4. The method of providing an indicator of potential for abrupt changes in rock strength according to claim 3, wherein said log data relating to formation strength comprises log data relating to unconfined compressive strength.

5. The method of providing an indicator of potential for abrupt changes in rock strength according to claim 2, wherein said empirical wellbore data comprises at least one of:

(a) unconfined compressive strength;

(b) confined compressive strength;

(c) porosity;

(d) lithologies; and

(e) sonic velocities.

6. The method of providing an indicator of potential for abrupt changes in rock strength according to claim 1, wherein said forensic wellbore data includes at least one of:

(a) unconfined compressive strength;

(b) confined compressive strength;

(c) porosity;

(d) lithologies; and

(e) sonic velocities.

7. The method of providing an indicator of potential for abrupt changes in rock strength according to claim 1, wherein said indicator of potential for abrupt changes in rock strength comprises a numerical indicator of potential for abrupt changes in rock strength.

8. The method of providing an indicator of potential for abrupt changes in rock strength according to claim 1, wherein said numerical indicator comprises a numerical value in the range between an upper boundary value and a lower boundary value.

9. The method of providing an indicator of potential for abrupt changes in rock strength according to claim 2:

(h) wherein said indicator of potential for abrupt changes in rock strength is generated repeatedly during drilling operations; and

(i) wherein said indicator provides an indication of potential for abrupt changes in rock strength before drilling occurs.

10. The method of providing an indicator of potential for abrupt changes in rock strength according to claim 1 further comprising:

(f) altering at least one drilling condition in response to said indicator in order to improve drilling operations.

11. The method of providing an indicator of potential for abrupt changes in rock strength according to claim 10, wherein said at least one drilling condition includes at least one of:

(1) bit type;

(2) rotary speed; and

(3) weight on bit.

12. The method of providing an indicator of potential for abrupt changes in rock strength according to claim 11, wherein said interfacial severity computer program establishes correspondence between a plurality of abrupt changes in rock strength and said indicator.

13. The method of providing an indicator of potential for abrupt changes in rock strength according to claim 12, wherein said plurality of measures of rock strength include a plurality of the following:

(a) average unconfined compressive strength;

(b) the root-mean-square value of the unconfined compressive strength;

(c) frequency of change in unconfined compressive strength.

14. An apparatus for providing an indicator of potential for abrupt changes in rock strength in a particular wellbore, comprising:

(a) a data processing system adapted for execution of program instructions;

(b) an interfacial severity computer program composed of executable program instructions, and including;

(1) an input program module for receiving forensic data corresponding to at least one of the following distinct wellbore parameters for a predefined interval;

(a) average unconfined compressive strength;

(b) the root-mean-square value of the unconfined compressive strength;

(c) frequency of change in unconfined compressive strength;

(2) an calculation program module which includes an algorithm which establishes correspondence between said distinct wellbore parameters and an indicator of potential for abrupt changes in rock strength and which combines the effects of at least two of said distinct wellbore parameters utilizing said algorithm in order to produce as an output an indicator of potential for abrupt changes in rock strength.

15. The apparatus for providing an indicator of potential for abrupt changes in rock strength according to claim 14, wherein said interfacial severity computer program further includes:

(3) an output program which provides in a human-readable format said indicator of potential for abrupt changes in rock strength.

16. The apparatus for providing an indicator of potential for abrupt changes in rock strength according to claim 15, wherein said indicator for potential abrupt changes in rock strength is presented in human-readable format of a single numeric value from a range of available numeric values between an upper numeric limit and a lower numeric limit.

17. The apparatus for providing an indicator of potential for abrupt changes in rock strength according to claim 14, wherein said interfacial severity computer program further includes:

(3) program instructions for recursively computing said indicator of potential for abrupt changes in rock strength during drilling operations.