METHOD FOR DRILLING WITH PROJECTIONS BASED ON ADJUSTED KALMAN FILTERS

Abstract

The method for drilling includes extending a borehole from a surface location to a borehole end with a drill string having a bottom hole assembly with a drill bit. A surface sensor and a downhole sensor take measurements used to project borehole features, like the borehole end. The measurements are used to project the borehole end so that the drill bit can be steered through the rock formation. The downhole sensor is separated from the bit location by a plurality of segments. The method includes corrections when the measurements at the downhole location are not the measurements at the bit location. As the drill bit travels, the types of corrections change, including applying an initial Kalman filter, a first adjusted Kalman filter, a second adjusted Kalman filter, and a third adjusted Kalman filter, according to the plurality of segments between the downhole sensor and the bit location.

Claims

1. A method for drilling, comprising the steps of: extending a borehole from a surface location to a borehole end with a drill string being comprised of a bottom hole assembly with a drill bit, wherein the drill bit is positioned on the bottom hole assembly at said borehole end so as to set a bit location, wherein said surface location is comprised of a surface sensor, wherein said bottom hole assembly is comprised of a downhole sensor at a downhole location, wherein said downhole sensor is separated by a plurality of segments from said bit location, wherein said plurality of said segments has a plurality length S, said bit location and said downhole locations being separated by said plurality length S, wherein each segment has a segment length s less than said plurality length, and wherein the step of extending is comprised of the following steps: Step A: setting said drill bit at an initial location (K), said bit location being at said initial location K, said downhole location being at a K-S location; Step B: measuring with said surface sensor at said surface location for said bit location at said initial location (K) so as to determine an initial location (K) surface sensor measurement; Step C: measuring with said downhole sensor at said downhole location for said bit location at said initial location (K) so as to determine a location (K-S) downhole sensor measurement; Step D: applying an initial Kalman filter to said initial location (K) surface sensor measurement and said location (K-S) downhole sensor measurement, so as to generate a projection of said borehole end for steering said drill bit, wherein said initial Kalman filter is comprised of an initial error correction based on said initial location (K) surface sensor measurement and said location (K-S) downhole sensor measurement; Step E: moving said drill bit to a location (K+ (n)s), said bit location being at said location (K + (n)s), said downhole location being at a (K-S+(n)s) location, wherein n is a positive integer; Step F: measuring with said surface location sensor at said surface location for said bit location at said location (K+(n)s) so as to determine a location (K+(n)s) surface sensor measurement; Step G: measuring with said downhole sensor at said downhole location for said bit location at said location (K+ (n)s) so as to determine a location (K-S +(n)s) downhole sensor measurement; Step H: applying a first adjusted Kalman filter to said location (K+ (n)s) surface sensor measurement and said location (K-S +(n)s) downhole sensor measurement, so as to generate a first adjusted projection of said borehole end for steering said drill bit, wherein said first level adjusted Kalman filter is comprised of a first level adjusted error correction based on said initial location (K) surface sensor measurement, said location (K+ (n)s) surface sensor measurement, and said location (K-S) downhole sensor measurement; Step I: repeating the Steps E-H until n(s) is equal to S; Step J: moving said drill bit to said location (K+ (n)s) when (K+(n)s) is equal to (K+S), said bit location being at said location (K + (n)s), said downhole location being at said (K-S+(n)s) location when (K-S+(n)s) is equal to (K); Step K: measuring with said surface location sensor at said surface location for said bit location at said location (K+S) so as to determine a location (K+S) surface sensor measurement; Step L: measuring with said downhole sensor at said downhole location for said bit location at said location (K) so as to determine a location (K) downhole sensor measurement; Step M: applying a second level adjusted Kalman filter to said location (K+ S) surface sensor measurement and said location (K) downhole sensor measurement, so as to generate a second level adjusted projection of said borehole end for steering said drill bit, wherein said second level adjusted Kalman filter is comprised of a second level adjusted error correction based on said initial location (K) surface sensor measurement, said location (K+ (n)s) surface sensor measurement, said location (K+S) surface sensor measurement, said location (K-S) downhole sensor measurement and said location (K) downhole sensor measurement; Step N: moving said drill bit to a location (K+S+(z)s), said bit location being at said location (K+S+(z)s), said downhole location being at said (K+(z)s) location, wherein z is a positive integer; Step O: measuring with said surface location sensor at said surface location for said bit location 26 at said location (K+S+(z)s) so as to determine a location (K+S+(z)s) surface sensor measurement; Step P: measuring with said downhole sensor at said downhole location for said bit location 26 at said location (K+(z)s) so as to determine a location (K+(z)s) downhole sensor measurement; Step Q: applying a third level adjusted Kalman filter to said location (K+S+(z)s) surface sensor measurement and said location (K+(z)s) downhole sensor measurement, when z is equal to n, so as to generate a third level adjusted projection of said borehole end for steering said drill bit, wherein said third level adjusted Kalman filter is comprised of a third level adjusted error correction based on said initial location (K) surface sensor measurement, said location (K+ (n)s) surface sensor measurement, said location (K+S) surface sensor measurement, said location (K+S+(z)s) surface sensor measurement, said location (K-S) downhole sensor measurement, said location (K-S+(n)s) downhole sensor measurement, said location (K) downhole sensor measurement, and said location (K+(z)s) downhole sensor measurement; repeating the Steps N-Q for completing a wellbore.

2. The method for drilling, according to claim 1, wherein said plurality length S is equally divided by said segments between said bit location and said downhole location.

3. The method for drilling, according to claim 2, wherein each segment length is equal to another segment length for said plurality of said segments.

4. The method for drilling, according to claim 1, wherein each segment length s is an amount of length determined by a distance traveled by said drill bit for a predetermined time interval.

5. The method for drilling, according to claim 1, wherein said surface sensor is comprised of at least one of a group consisting of: a sensor for Rate of Penetration (ROP), sensor for Weight On Bit (WOP), sensor for Differential Pressure across the Drill Bit (DIFP), a depth sensor, and a second for Rotary Speed of the Drill Pipe (RPM).

6. The method for drilling, according to claim 1, wherein said downhole sensor is comprised of at least one of a group consisting of: a sensor for Gravity Toolface (GTF), a pressure sensor, a temperature sensor, a sensor for Inclination (INC), and a sensor for Azimuth (AZI).

7. The method for drilling, according to claim 1, wherein said plurality of segments is comprised of two segments.

8. The method for drilling, according to claim 1, wherein said plurality of segments is comprised of more than two segments.

9. A method for drilling, comprising the steps of: extending a borehole from a surface location to a borehole end with a drill string being comprised of a bottom hole assembly with a drill bit, wherein the drill bit is positioned on the bottom hole assembly at said borehole end so as to set a bit location, wherein said surface location is comprised of a surface sensor at said surface location, wherein said bottom hole assembly is comprised of a downhole sensor at a downhole location, wherein said downhole sensor is separated by a plurality of segments from said bit location, wherein said plurality of said segments has a plurality length, said bit location and said downhole locations being separated by said plurality length S, wherein each segment has a segment length s less than said plurality length, wherein said plurality of segments is comprised of a first segment having a first segment length and a second segment having a second segment length, and wherein the step of extending is comprised of the following steps: Step A1: setting said drill bit at an initial location (K), said bit location being at said initial location K, said downhole location being at a K-S location; Step B1: measuring with said surface sensor at said surface location for said bit location at said initial location (K) so as to determine an initial location (K) surface sensor measurement; Step C1: measuring with said downhole sensor at said downhole location for said bit location at said initial location (K) so as to determine a location (K-S) downhole sensor measurement; Step D1: applying an initial Kalman filter to said initial location (K) surface sensor measurement and said location (K-S) downhole sensor measurement, so as to generate a projection of said borehole end for steering said drill bit, wherein said initial Kalman filter is comprised of an initial error correction based on said initial location (K) surface sensor measurement and said location (K-S) downhole sensor measurement; Step E1: moving said drill bit to a location (K+ said first segment length), said bit location being at said location (K+ said first segment length), said downhole location being at a (K-S+said first segment length) location, Step F1: measuring with said surface location sensor at said surface location for said bit location at said location (K+ said first segment length) so as to determine a location (K+ said first segment length) surface sensor measurement; Step G1: measuring with said downhole sensor at said downhole location for said bit location at said location (K+ said first segment length) so as to determine a location (K-S +said first segment length) downhole sensor measurement; Step H1: applying a first adjusted Kalman filter to said location (K+ said first segment length) surface sensor measurement and said location (K-S +said first segment length) downhole sensor measurement, so as to generate a first adjusted projection of said borehole end for steering said drill bit, wherein said first level adjusted Kalman filter is comprised of a first level adjusted error correction based on said initial location (K) surface sensor measurement, said location (K+ said first segment length) surface sensor measurement, and said location (K-S) downhole sensor measurement; Step 11: moving said drill bit to said location (K+ said first segment length + said second segment length) when (K+ said first segment length + said second segment length) is equal to (K+S), said bit location being at said location (K+ said first segment length + said second segment length), said downhole location being at said (K) location when (K+ said first segment length + said second segment length) is equal to (K+S); Step J1: measuring with said surface location sensor at said surface location for said bit location at said location (K+S) so as to determine a location (K+S) surface sensor measurement; Step K1: measuring with said downhole sensor at said downhole location for said bit location at said location (K) so as to determine a location (K) downhole sensor measurement; Step L1: applying a second level adjusted Kalman filter to said location (K+ S) surface sensor measurement and said location (K) downhole sensor measurement, so as to generate a second level adjusted projection of said borehole end for steering said drill bit, wherein said second level adjusted Kalman filter is comprised of a second level adjusted error correction based on said initial location (K) surface sensor measurement, said location (K+ said first segment length) surface sensor measurement, said location (K+S) surface sensor measurement, said location (K-S) downhole sensor measurement and said location (K) downhole sensor measurement; Step M1: moving said drill bit to a location (K+S+said first segment length), said bit location being at said location (K+S+said first segment length), said downhole location being at said (K+said first segment length) location, Step N1: measuring with said surface location sensor at said surface location for said bit location at said location (K+S+ said first segment length) so as to determine a location (K+S+ said first segment length) surface sensor measurement; Step 01: measuring with said downhole sensor at said downhole location for said bit location at said location (K+ said first segment length) so as to determine a location (K+ said first segment length) downhole sensor measurement; and Step P1: applying a third level adjusted Kalman filter to said location (K+S+ said first segment length) surface sensor measurement and said location (K+ said first segment length) downhole sensor measurement, so as to generate a third level adjusted projection of said borehole end for steering said drill bit, wherein said third level adjusted Kalman filter is comprised of a third level adjusted error correction based on said initial location (K) surface sensor measurement, said location (K+ said first segment length) surface sensor measurement, said location (K+S) surface sensor measurement, said location (K+S+ said first segment length) surface sensor measurement, said location (K-S) downhole sensor measurement, said location (K) downhole sensor measurement, and said location (K+ said first segment length) downhole sensor measurement.

10. The method for drilling, according to claim 9, further comprising the steps of: Step M2: moving said drill bit to a location (K+S+said first segment length+said second segment length), said bit location being at said location (K+S+said first segment length+said second segment length), said downhole location being at said (K+S) location, Step N2: measuring with said surface location sensor at said surface location for said bit location at said location (K+S+ said first segment length+said second segment length) so as to determine a location (K+S+ said first segment length+said second segment length) surface sensor measurement; Step O2: measuring with said downhole sensor at said downhole location for said bit location at said location (K+ said first segment length+said second segment length) so as to determine a location (K+S) downhole sensor measurement; and Step P2: applying another third level adjusted Kalman filter to said location (K+S+ said first segment length+said second segment length) surface sensor measurement and said location (K+S) downhole sensor measurement, so as to generate another third level adjusted projection of said borehole end for steering said drill bit, wherein said another third level adjusted Kalman filter is comprised of a third level adjusted error correction based on said initial location (K) surface sensor measurement, said location (K+ said first segment length) surface sensor measurement, said location (K+S) surface sensor measurement, said location (K+S+ said first segment length) surface sensor measurement, said location (K+S+ said first segment length+said second segment length) surface sensor measurement, said location (K-S) downhole sensor measurement, said location (K) downhole sensor measurement, said location (K+ said first segment length) downhole sensor measurement, and said location (K+S) downhole sensor measurement;.

11. The method for drilling, according to claim 10, further comprising the steps of: repeating the Steps M1-P1 for moving said drill bit another first segment length and repeating the Steps M2-P2 for moving said drill bit another second segment length so as to complete a wellbore.

12. The method for drilling, according to claim 9, wherein said plurality length S is equally divided by said segments between said bit location and said downhole location.

13. The method for drilling, according to claim 12, wherein said first segment length is equal to said second segment length.

14. The method for drilling, according to claim 9, wherein each segment length s is an amount of length determined by a distance traveled by said drill bit for a predetermined time interval.

15. The method for drilling, according to claim 9, wherein said surface sensor is comprised of at least one of a group consisting of: a sensor for Rate of Penetration (ROP), sensor for Weight On Bit (WOP), sensor for Differential Pressure across the Drill Bit (DIFP), a depth sensor, and a second for Rotary Speed of the Drill Pipe (RPM).

16. The method for drilling, according to claim 9, wherein said downhole sensor is comprised of at least one of a group consisting of: a sensor for Gravity Toolface (GTF), a pressure sensor, a temperature sensor, a sensor for Inclination (INC), and a sensor for Azimuth (AZI).

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0024] FIG. 1 is a schematic view of the method for drilling according to the present invention, showing the drill bit with the bit location at location (K).

[0025] FIG. 2 is a schematic view of the method for drilling according to the present invention, showing the drill bit with the bit location at location (K+(n)s).

[0026] FIG. 3 is a schematic view of the method for drilling according to the present invention, showing the drill bit with the bit location at location (K+(n)s), when (n)s is equal to S.

[0027] FIG. 4 is a schematic view of the method for drilling according to the present invention, showing the drill bit with the bit location at location (K+S+(z)s).

[0028] FIG. 5 is a schematic view of the method for drilling according to the present invention, showing the drill bit with the bit location at location (K+S+(z)s), when (z)s is equal to S.

DETAILED DESCRIPTION OF THE INVENTION

[0029] Referring to FIGS. 1-5, the present invention includes a borehole 10 extending from a surface location 12 to a borehole end 14 with a drill string 20 being comprised of a bottom hole assembly 24 with a drill bit 22. The bottom hole assembly 24 has a proximal end toward the surface location 12 and a distal end toward the borehole end 14. The drill bit 22 at the distal end of the bottom hole assembly 24 moves further into the rock formation as guided by projections to reach certain depths and inclinations as need to target hydrocarbons for discovery and production. The bottom hole assembly 24 can further include additional tool body sections between the proximal end and the drill bit 22 for logging, other sensors for additional measurements, and other components to actuate the drill bit. Other downhole tools on the drill string 20, such as reamers and stabilizers may also include sensors that may be compatible with the present invention. The downhole location of the downhole sensor can be on other tools, like logging tools, instead of the bottom hole assembly 24. Notably, the drill bit 22 in the bottom of the borehole sets the bit location 26 at or near the borehole end.

[0030] The surface location 12 is comprised of a surface sensor 30. The bottom hole assembly 24 is comprised of a downhole sensor 32 at a downhole location 34. The bit location 26 is separate from the downhole location 34. The drill bit 22 is at the distal end of the bottom hole assembly 24 and at the bit location 26, and the downhole sensor 32 is placed between the drill bit 22 and the proximal end of the bottom hole assembly 24. The downhole sensor 32 is away from the distal end of the bottom hole assembly 24 and at the downhole location 34. The downhole sensor 32 may also be on another downhole tool so that the downhole location 34 is not on the bottom hole assembly 24, but there is still the equivalent separation between the downhole location 34 and the bit location 26. The downhole sensor 32 is separated from the bit location 26 by a plurality 36 of segments 38. Thus, the separation between the downhole location 34 and the bit location 24 is a distance that corresponds to the plurality 36 of segments 36. The plurality 36 has a plurality length S, and each segment 38 has a respective segment length s. Each segment length s is always less than the plurality length S.

[0031] In some embodiments, the plurality length S is equally divided by the segments 38. The segment lengths s between the bit location 26 and the downhole location 34 are equal. Each segment length s is the same or equal to any segment length s for the plurality length S. Other embodiments include unequal segment lengths s for the plurality length S. The segments 38 are not required to be equal for the entire plurality 36 of segments 38. Embodiments also include each segment length s being an amount of length determined by a distance traveled by said drill bit for a predetermined time interval. In this example, the time interval may be the time needed to reset a sensor. If sensors are not streaming data, the drill bit is still moving, and a gap is created. The present invention still allows the advanced modification of the Kalman filter, even when the drill bit has traveled a gap based on distance or distance based on a time interval.

[0032] In the present invention, the surface sensor 30 is any sensor located at the surface location 12. There can also be a plurality of surface sensors with their respective surface sensor measurements, and each surface sensor measurement can be used to modify the Kalman filter according to the present invention. Additional surface sensors can be cumulative to further improve the accuracy of the projections. The surface sensor 30 can be a sensor for Rate of Penetration (ROP), sensor for Weight On Bit (WOP), sensor for Differential Pressure across the Drill Bit (DIFP), a depth sensor, a second for Rotary Speed of the Drill Pipe (RPM), or other sensor for measuring borehole and drill string features. A plurality of surface sensors can be a mix of these various sensors, but each of the plurality of surface sensors must still be determining surface sensor measurements at the surface location 12 for the bit location 26.

[0033] In the present invention, the downhole sensor 32 is any sensor located at the downhole location 34. There can also be a plurality of downhole sensors with their respective downhole sensor measurements, and each downhole sensor measurement can be used to modify the Kalman filter according to the present invention. Additional downhole sensors can be cumulative to further improve the accuracy of the projections. The downhole sensor 32 can be a sensor for Gravity Toolface (GTF), a pressure sensor, a temperature sensor, a sensor for Inclination (INC), a sensor for Azimuth (AZI), or other sensor for measuring borehole and drill string features. A plurality of downhole sensors can be a mix of these various sensors, but each of the plurality of downhole sensors must still be determining downhole sensor measurements at the downhole location 34 for the bit location 26.

[0034] As shown in FIGS. 1-5, the method of the present invention includes extending the borehole 10 from the surface location 12 to the borehole end 14. The step of extending is comprised of the following steps:

[0035] Step A: setting the drill bit at an initial location (K). The bit location 26 is at the initial location K, and the downhole location is at a K-S location.

[0036] Step B: measuring with the surface sensor at the surface location for the bit location 26 at the initial location (K) so as to determine an initial location (K) surface sensor measurement.

[0037] Step C: measuring with the downhole sensor at the downhole location for the bit location 26 at the initial location (K) so as to determine a location (K-S) downhole sensor measurement.

[0038] Step D: applying an initial Kalman filter to the initial location (K) surface sensor measurement and the location (K-S) downhole sensor measurement, so as to generate a projection of the borehole end for steering the drill bit. The initial Kalman filter is comprised of an initial error correction based on the initial location (K) surface sensor measurement and the location (K-S) downhole sensor measurement. This level of correction by the initial Kalman filter is based on the properties of the sensors themselves. There is no historical data yet, and there is no basis for further modification of the initial Kalman filter yet.

[0039] Step E: moving the drill bit to a location (K+ (n)s). The bit location 26 is at the location (K + (n)s), and the downhole location is at a (K-S+(n)s) location. “n” is a positive integer, and “s” is a segment length. The drill bit 22 has moved less than the plurality length S, and the location (K-S) downhole sensor measurement has not additional use yet.

[0040] Step F: measuring with the surface location sensor at the surface location for the bit location 26 at the location (K+(n)s) so as to determine a location (K+(n)s) surface sensor measurement.

[0041] Step G: measuring with the downhole sensor at the downhole location for the bit location 26 at the location (K+ (n)s) so as to determine a location (K-S +(n)s) downhole sensor measurement.

[0042] Step H: applying a first adjusted Kalman filter to the location (K+ (n)s) surface sensor measurement and the location (K-S+(n)s) downhole sensor measurement, so as to generate a first adjusted projection of the borehole end for steering the drill bit. The first level adjusted Kalman filter is comprised of a first level adjusted error correction based on the initial location (K) surface sensor measurement, the location (K+ (n)s) surface sensor measurement, and the location (K-S) downhole sensor measurement. As the drill bit 22 travels through the gap (plurality length S corresponding to the plurality 36 of segments 38), the surface sensor measurements for the bit location 26 can be used to adjust the initial Kalman filter for increased accuracy and precision. The downhole sensor measurements are taken, even though such measurements within the gap are not yet useful for further modifying the Kalman filter.

[0043] Step I: repeating the Steps E-H until n(s) is equal to S. The drill bit 22 through the gap generates the first adjusted projections, and the location (K-S +(n)s) downhole sensor measurements are still taken and can be used for the first adjusted projections. However, the first level adjusted error correction is made without the location (K-S +(n)s) downhole sensor measurements.

[0044] Step J: moving the drill bit to the location (K+ (n)s) when (K+(n)s) is equal to (K+S). The bit location 26 is at the location (K + (n)s), and the downhole location is at the (K-S+(n)s) location when (K-S+(n)s) is equal to (K). The drill bit 22 has moved the plurality length S, and the location (K-S) downhole sensor measurement can now be used to confirm the location (K-S +(n)s) downhole sensor measurement, which is now the location (K) downhole sensor measurement, since (n)s is equal to S at this location.

[0045] Step K: measuring with the surface location sensor at the surface location for the bit location 26 at the location (K+S) so as to determine a location (K+S) surface sensor measurement.

[0046] Step L: measuring with the downhole sensor at the downhole location for the bit location 26 at the location (K) so as to determine a location (K) downhole sensor measurement.

[0047] Step M: applying a second level adjusted Kalman filter to the location (K+ S) surface sensor measurement and the location (K) downhole sensor measurement, so as to generate a second level adjusted projection of the borehole end for steering the drill bit. The second level adjusted Kalman filter is comprised of a second level adjusted error correction based on the initial location (K) surface sensor measurement, the location (K+ (n)s) surface sensor measurement, the location (K+S) surface sensor measurement, the location (K-S) downhole sensor measurement and the location (K) downhole sensor measurement. The drill bit 22 has now traveled the gap (plurality length S corresponding to the plurality 36 of segments 38), and now both the surface sensor measurements for the bit location 26 and the downhole sensor measurements for the bit location 26 can be used to adjust the first level adjusted Kalman filter. The measurements previously unused due to the gap (separation between the downhole sensor 32 and bit location 26 or separation by a time interval) are now part of the method of the present invention. The downhole sensor measurements are not able to be used in the modification of the Kalman filter for a second level adjusted Kalman filter.

[0048] Step N: moving the drill bit to a location (K+S+(z)s). The bit location 26 is at the location (K+S+(z)s), and the downhole location is at the (K+(z)s) location. “z” is a positive integer, and “s” is still a segment length. The drill bit 22 has now moved more than the plurality length S, and the second level adjusted Kalman filter is based on the location (K) downhole sensor measurement. There is a now a location (K+(z)s) downhole sensor measurement, and the present invention includes a method to now use this location (K+(z)s) downhole sensor measurement, even though the drill bit 22 has traveled into the next gap. That is, the drill bit 22 traveled the plurality length S and has now moved an additional (z) segment lengths s. The drill bit 22 has not yet moved another plurality length S for another second level adjusted Kalman filter.

[0049] Step O: measuring with the surface location sensor at the surface location for the bit location 26 at the location (K+S+(z)s) so as to determine a location (K+S+(z)s) surface sensor measurement.

[0050] Step P: measuring with the downhole sensor at the downhole location for the bit location 26 at the location (K+(z)s) so as to determine a location (K+(z)s) downhole sensor measurement.

[0051] Step Q: applying a third level adjusted Kalman filter to the location (K+S+(z)s) surface sensor measurement and the location (K+(z)s) downhole sensor measurement, when z is equal to n, so as to generate a third level adjusted projection of the borehole end for steering the drill bit. The third level adjusted Kalman filter is comprised of a third level adjusted error correction based on the initial location (K) surface sensor measurement, the location (K+ (n)s) surface sensor measurement, the location (K+S) surface sensor measurement, the location (K+S+(z)s) surface sensor measurement, the location (K-S) downhole sensor measurement, the location (K) downhole sensor measurement, the location (K-S+(n)s) downhole sensor measurement, and the location (K+(z)s) downhole sensor measurement. With the drill bit 22 moving beyond the plurality length S, the location (K-S+(n)s) downhole sensor measurement is now recited in the method for applying the third level adjusted Kalman filter. The third level adjusted error correction is now based on the location (K-S+(n)s) downhole sensor measurement. The location (K-S+(n)s) downhole sensor measurement was previously unusable for the modification of the Kalman filter, and the present invention now incorporates the location (K-S+(n)s) downhole sensor measurement for the third level adjusted Kalman filter. This third level adjusted projection of the borehole end has a correction beyond any of the prior art methods, when there is the plurality 36 of segments 38 between the downhole sensor 32 and the bit location 26. The gap of this separation allows the location (K-S+(n)s) downhole sensor measurement to be applied to the further modification of the Kalman filter, even when drill bit 32 has not traveled a full plurality length S. There is increased accuracy due to the additional modifications to the adjusted Kalman filter.

[0052] The method further includes repeating the Steps N-Q for completing a wellbore. Once the drill bit 22 has traveled past a plurality length S, Steps N-Q can be repeated for the third level adjusted projections to complete the borehole. The method further includes stopping and restarting so that the initial location can be reset. Again, there are different gaps or separations that can occur when drilling the borehole. Whether the drill bit 22 travels without data between certain distances for time, distance, communication delays, or other reasons, the present invention enables the measurements from the gaps to further modify the adjusted Kalman filters. The embodiments of the present invention include the plurality 36 of segments 38 being comprised of two segments, 38A, 38C. In most embodiments, there are more than two segments 38A, 38C.

[0053] In an exemplary embodiment of the plurality 36 of segments 38 being comprised of a first segment 38A with a first segment length 38B and a second segment 38C with a second segment length 38D, the plurality 36 of segments 38 still has a plurality length S. The downhole sensor 32 is still separated from the bit location 26 by the plurality 36 of segments 38. The first segment length 38B and the second segment lengths 38D can be equal. The first segment length 38B and the second segment lengths 38D can also be determined by a distance traveled by the drill bit 22 for a predetermined time interval.

[0054] This alternative embodiment includes the method for drilling, comprising the step of extending a borehole 10 from a surface location 12 to a borehole end 14 with a drill string 20 being comprised of a bottom hole assembly 24 with a drill bit 22. The step of extending includes:

[0055] Step A1: setting the drill bit at an initial location (K). The bit location 26 is at the initial location K, and the downhole location being at a K-S location.

[0056] Step B1: measuring with the surface sensor at the surface location for the bit location 26 at the initial location (K) so as to determine an initial location (K) surface sensor measurement.

[0057] Step C1: measuring with the downhole sensor at the downhole location for the bit location 26 at the initial location (K) so as to determine a location (K-S) downhole sensor measurement.

[0058] Step D1: applying an initial Kalman filter to the initial location (K) surface sensor measurement and the location (K-S) downhole sensor measurement, so as to generate a projection of the borehole end for steering the drill bit. The initial Kalman filter is comprised of an initial error correction based on the initial location (K) surface sensor measurement and the location (K-S) downhole sensor measurement. Again, the initial Kalman filter is based on the sensors themselves.

[0059] Step E1: moving the drill bit to a location (K+ the first segment length). The bit location 26 is at the location (K+ the first segment length), and the downhole location being at a (K-S+the first segment length) location.

[0060] Step F1: measuring with the surface location sensor at the surface location for the bit location 26 at the location (K+ the first segment length) so as to determine a location (K+ the first segment length) surface sensor measurement.

[0061] Step G1: measuring with the downhole sensor at the downhole location for the bit location 26 at the location (K+ the first segment length) so as to determine a location (K-S +the first segment length) downhole sensor measurement.

[0062] Step H1: applying a first adjusted Kalman filter to the location (K+ the first segment length) surface sensor measurement and the location (K-S +the first segment length) downhole sensor measurement, so as to generate a first adjusted projection of the borehole end for steering the drill bit. The first level adjusted Kalman filter is comprised of a first level adjusted error correction based on the initial location (K) surface sensor measurement, the location (K+ the first segment length) surface sensor measurement, and the location (K-S) downhole sensor measurement. The location (K-S +the first segment length) downhole sensor measurement is not used to modify the initial Kalman filter into the first adjusted Kalman filter.

[0063] Step l1: moving the drill bit to the location (K+ the first segment length + the second segment length) when (K+ the first segment length + the second segment length) is equal to (K+S). The bit location 26 is at the location (K+ the first segment length + the second segment length). The downhole location is at the (K) location because (K+ the first segment length + the second segment length) is equal to (K+S). The drill bit 22 has now traveled the gap (the plurality length S).

[0064] Step J1: measuring with the surface location sensor at the surface location for the bit location 26 at the location (K+S) so as to determine a location (K+S) surface sensor measurement.

[0065] Step K1: measuring with the downhole sensor at the downhole location for the bit location 26 at the location (K) so as to determine a location (K) downhole sensor measurement.

[0066] Step L1: applying a second level adjusted Kalman filter to the location (K+ S) surface sensor measurement and the location (K) downhole sensor measurement, so as to generate a second level adjusted projection of the borehole end for steering the drill bit. The second level adjusted Kalman filter is comprised of a second level adjusted error correction based on the initial location (K) surface sensor measurement, the location (K+ the first segment length) surface sensor measurement, the location (K+S) surface sensor measurement, the location (K-S) downhole sensor measurement and the location (K) downhole sensor measurement. The location (K-S +the first segment length) downhole sensor measurement is still not used to modify the first adjusted Kalman filter into the second adjusted Kalman filter.

[0067] Step M1: moving the drill bit to a location (K+S+the first segment length). The bit location 26 is at the location (K+S+the first segment length), and the downhole location is at the (K+the first segment length) location.

[0068] Step N1: measuring with the surface location sensor at the surface location for the bit location 26 at the location (K+S+ the first segment length) so as to determine a location (K+S+ the first segment length) surface sensor measurement.

[0069] Step O1: measuring with the downhole sensor at the downhole location for the bit location 26 at the location (K+ the first segment length) so as to determine a location (K+ the first segment length) downhole sensor measurement.

[0070] Step P1: applying a third level adjusted Kalman filter to the location (K+S+ the first segment length) surface sensor measurement and the location (K+ the first segment length) downhole sensor measurement, so as to generate a third level adjusted projection of the borehole end for steering the drill bit. The third level adjusted Kalman filter is comprised of a third level adjusted error correction based on the initial location (K) surface sensor measurement, the location (K+ the first segment length) surface sensor measurement, the location (K+S) surface sensor measurement, the location (K+S+ the first segment length) surface sensor measurement, the location (K-S) downhole sensor measurement, the location (K) downhole sensor measurement, and the location (K+ the first segment length) downhole sensor measurement. The location (K-S +the first segment length) downhole sensor measurement is finally used to modify the second adjusted Kalman filter into the third adjusted Kalman filter.

[0071] In this embodiment, the drill bit 22 reaches another plurality length S in only two segments. The method can further include:

[0072] Step M2: moving the drill bit to a location (K+S+the first segment length+the second segment length). The bit location 26 is at the location (K+S+the first segment length+the second segment length), and the downhole location is at the (K+S) location.

[0073] Step N2: measuring with the surface location sensor at the surface location for the bit location 26 at the location (K+S+ the first segment length+the second segment length) so as to determine a location (K+S+ the first segment length+the second segment length) surface sensor measurement.

[0074] Step O2: measuring with the downhole sensor at the downhole location for the bit location 26 at the location (K+ the first segment length+the second segment length) so as to determine a location (K+S) downhole sensor measurement.

[0075] Step P2: applying another third level adjusted Kalman filter to the location (K+S+ the first segment length+the second segment length) surface sensor measurement and the location (K+S) downhole sensor measurement, so as to generate another third level adjusted projection of the borehole end for steering the drill bit. The another third level adjusted Kalman filter is comprised of a third level adjusted error correction based on the initial location (K) surface sensor measurement, the location (K+the first segment length) surface sensor measurement, the location (K+S) surface sensor measurement, the location (K+S+the first segment length) surface sensor measurement, the location (K+S+the first segment length+the second segment length) surface sensor measurement, the location (K-S) downhole sensor measurement, the location (K) downhole sensor measurement, the location (K+the first segment length) downhole sensor measurement, and the location (K+S) downhole sensor measurement.

[0076] To complete the wellbore, this method further includes repeating Steps M1-P1 for moving the drill bit another first segment length and the Steps M2-P2 for moving the drill bit another second segment length.

[0077] The present invention provides a method for drilling based on measurements from at least one sensor at a surface location for a bit location measurement and at least one sensor at a downhole location separated from the drill bit by a plurality of segments and adjusted Kalman filters, according to the separation or gaps in measurements between the bit location and downhole location. The adjusted Kalman filters are applied to raw measurements for projections to steer a drill bit. The projection can be a Projection to Bit (PTB) for the bottom of the borehole. The borehole features, like depth, inclination, and diameter, are needed for determination of subsequent installations and interventions to produce oil and gas from the geological or rock formation. The production zones crossed and the angle of crossing the production zones are important information. While drilling, the drill bit should be steered so that the borehole features are as close as possible to the calculations and studies of the geological formation. A Kalman filter is helpful to increase accuracy of the projection based on multiple measurements, but the Kalman filter can also require modification so that the accuracy of the projection is even more improved.

[0078] In the present invention, there is a complication based on gaps. There is a practical separation of the downhole sensors from the bit location. This distance gap can be several feet, and waiting several feet, like 50 feet, to adjust a correction may not be sufficient for the active steering of a drill bit. Data is not always streaming either. There can be gaps in distance traveled by the drill bit caused by time intervals between taking measurements or transmitting measurements. There can be further adjustment of the Kalman filter at different levels relative to the downhole sensor being at a downhole location separated by a plurality of segments from a bit location of the drill bit. The further adjustment is no longer limited to the plurality length between the downhole sensor and bit location.

[0079] The foregoing disclosure and description of the invention is illustrative and explanatory thereof. Various changes in the details of the illustrated structures, construction and method can be made without departing from the true spirit of the invention.