Methods for characterization of formations, navigating drill paths, and placing wells in earth boreholes

1. A method for directing borehole drilling in a target earth formation, comprising the steps of:

providing drilling equipment having a bottom hole assembly that includes a controllable directional drilling subsystem, and a logging-while-drilling directional measurement tool with a look-around and look-ahead capability, wherein the look-around capability comprises registering a direction from which maximum conductivity can be measured;

determining the presence of a predetermined type of formation characteristic in the target formation; and

navigating a drill path in the target formation with said drilling equipment, including receiving measurement signals from said directional measurement tool, obtaining, from the received measurement signals, indications of formation parameters with respect to said formation characteristic in the target formation, and controlling said directional drilling subsystem to drill in a direction determined as a function of said obtained indication of formation parameters.

2. The method as defined by claim 1 , wherein said step of providing a logging-while-drilling directional measurement tool comprises providing a logging-while-drilling directional resistivity measurement tool with a look-around or look-ahead capability.

3. The method as defined by claim 2 , wherein said step of determining the presence of a predetermined type of formation characteristic in the target formation, comprises:

storing, in a memory, a knowledge base comprising several representations of exemplary earth formation characteristic models;

providing initial parameter data for said target formation; and

comparing said initial parameter data with the models in said knowledge base to select a formation characteristic model, said predetermined type of formation characteristic in the target formation being derived from the selected formation characteristic model.

4. The method as defined by claim 3 , wherein said step of storing, in a memory, a knowledge base comprising several representations of exemplary earth formation characteristic models comprises storing models that comprise sets of formation geometries and formation physical parameters.

5. The method as defined by claim 3 , wherein said step of comparing said initial parameter data with said models comprises forward modeling said formation characteristic models, and comparing the results of said forward modelings with said initial parameter data.

6. The method as defined by claim 2 , wherein said step of obtaining, from the received measurement signals, indications of formation parameters with respect to said formation characteristic in the target formation, comprises inverting said received measurement signals to obtain said indications of formation parameters with respect to said formation characteristic in the target formation.

7. The method as defined by claim 3 , further comprising modifying the selected formation characteristic model in accordance with measurements received from said directional resistivity measurement tool.

8. A method for dynamically characterizing a target earth formation, comprising the steps of:

providing drilling equipment having a bottom hole assembly that includes a controllable directional drilling subsystem, and a logging-while-drilling directional measurement tool with a look-around or look-ahead capability, wherein the look-around capability comprises registering a direction from which maximum conductivity can be measured;

determining the presence of a predetermined type of formation characteristic in the target formation; and

drilling in the target formation with said drilling equipment, receiving measurement signals from said directional measurement tool, and further characterizing the predetermined type of formation characteristic in the target formation based on the received measurement signals.

9. The method as defined by claim 8 , wherein said step of providing a logging-while-drilling directional measurement tool comprises providing a logging-while-drilling directional resistivity measurement tool with a look-around and or look-ahead capability, and

wherein said step of determining the presence of a predetermined type of formation characteristic in the target formation, comprises:

storing, in a memory, a knowledge base comprising several representations of exemplary earth formation characteristic models;

providing initial parameter data for said target formation; and

comparing said initial parameter data with the models in said knowledge base to select a formation characteristic model, said predetermined type of formation characteristic in the target formation being derived from the selected formation characteristic model.

10. The method as defined by claim 9 , wherein said step of storing, in a memory, a knowledge base comprising several representations of exemplary earth formation characteristic models comprises storing models that comprise sets of formation geometries and formation physical parameters.

11. The method as defined by claim 9 , wherein said step of comparing said initial parameter data with said models comprises inverting the initial parameter data and comparing the results of said inversion with said models.

12. The method as defined by claim 9 , wherein said step of comparing said initial parameter data with said models comprises forward modeling said formation characteristic models, and comparing the results of said forward modelings with said initial parameter data.

13. The method as defined by claim 8 , wherein said step of providing a logging-while-drilling directional measurement tool comprises providing a logging-while-drilling directional resistivity measurement tool with a look-around and or look-ahead capability, and wherein said step of obtaining, from the received measurement signals, indications of formation parameters with respect to said formation characteristic in the target formation, comprises inverting said received measurement signals to obtain said indications of formation parameters with respect to said formation characteristic in the target formation.

14. A method for producing a borehole drilling plan in a target earth formation, comprising the steps of:

providing a memory;

storing, in said memory, a knowledge base comprising several representations of exemplary earth formation characteristic models;

providing initial parameter data for said target earth formation;

comparing said initial parameter data with the models in said knowledge base and selecting a model from said comparison; and

deriving a borehole drilling plan as a function of the selected model.

15. The method as defined by claim 14 , wherein said step of deriving a borehole drilling plan comprises deriving a plot as a function of the selected model and of said initial parameter data.

16. The method as defined by claim 15 , further comprising initiating borehole drilling in said target earth formation in accordance with said derived drilling plot.

17. The method as defined by claim 14 , wherein said exemplary earth formation models comprise sets of formation parameters and wherein said step of comparing said initial parameter data with said models comprises forward modeling said sets of formation parameters, and comparing the results of said forward modelings with said initial parameter data.

18. The method as defined by claim 16 , further comprising configuring a bottom hole assembly to include a directional drilling subsystem and a logging while drilling subsystem, and drilling in said target formation with a drill string having said configured bottom hole assembly.

19. The method as defined by claim 18 , further comprising controlling drilling in said target formation as a function of said derived drilling plan and also as a function of parameters determined from LWD measurements.

20. The method as defined by claim 19 , wherein said logging while drilling subsystem includes a directional resistivity measurement tool with a look-around or look-ahead capability.