Wellbore data depth matching using change point algorithms

1 . A method, comprising:

receiving a first well log comprising a first signal and a second well log comprising a second signal;

identifying in the first signal a first change point that demarcates a first signal region and a second signal region;

determining that the first signal region of the first signal is inconsistent in comparison to the second signal region;

producing a derivative signal by calculating a derivative of at least a portion of the first signal;

identifying in the derivative signal a second change point that demarcates a third signal region and a fourth signal region;

determining that the third signal region of the derivative signal has a value that is substantially zero;

producing a modified first well log by removing the first signal region from the first signal in response to determining that the first signal region of the first signal is inconsistent in comparison to the second signal region, and by removing the third signal region from the first signal in response to determining that the third signal region of the derivative signal has the value that is substantially zero;

selecting a third change point in the modified first well log and a fourth change point in the second well log;

positioning a first window within the modified first well log based at least in part on the third change point;

positioning a second window at a first location within the second well log based at least in part on the fourth change point;

determining a first similarity value between the first signal in the first window and the second signal in the second window at the first location;

repositioning the second window at a second location within the second well log based at least in part on the fourth change point;

determining a second similarity value between the first signal in the first window and the second signal in the second window at the second location;

selecting the first location or the second location of the second window based at least partially upon the first and second similarity values; and

producing a modified second well log based at least partially upon the selected first location or second location of the second window.

2 . The method of claim 1 , wherein determining that the first signal region of the first signal is inconsistent in comparison to the second signal region comprises determining that a mean of the first signal region is less than a mean of the second signal region minus a product, wherein the product comprises a predetermined input multiplied by an empirical standard deviation of the second signal region.

3 . The method of claim 1 , wherein determining that the first signal region of the first signal is inconsistent in comparison to the second signal region comprises determining that a mean of the first signal region is greater than a mean of the second signal region plus a product, wherein the product comprises a predetermined input multiplied by an empirical standard deviation of the second signal region.

4 . The method of claim 1 , further comprising determining a modified fourth change point based at least partially upon the selected first location or second location of the second window, and wherein the modified second well log is produced based at least partially upon the modified fourth change point.

5 . A method, comprising:

receiving a well log comprising a signal;

identifying in the signal a first change point that demarcates a first signal region and a second signal region;

determining that the first signal region is inconsistent in comparison to the second signal region;

producing a modified well log by removing the first signal region from the signal in response to determining that the first signal region is inconsistent in comparison to the second signal region;

producing a derivative signal by calculating a derivative of at least a portion of the signal;

identifying in the derivative signal a second change point that demarcates a third signal region and a fourth signal region;

determining that the third signal region of the derivative signal has a value that is substantially zero; and

adjusting the modified well log by removing the third signal region from the signal in response to determining that the third signal region of the derivative signal has the value that is substantially zero.

6 . The method of claim 5 , wherein determining that the first signal region is inconsistent in comparison to the second signal region comprises:

determining an upper bound and a lower bound based at least partially upon the second signal region; and

determining that a mean of the first signal region is not between the upper and lower bounds.

7 . The method of claim 6 , further comprising determining an empirical standard deviation of the second signal region, wherein the upper and lower bounds are based upon the empirical standard deviation of the second signal region.

8 . The method of claim 5 , wherein determining that the first signal region is inconsistent in comparison to the second signal region comprises comparing a mean of the first signal region to a mean of the second signal region in combination with a product, wherein the product comprises a predetermined input multiplied by an empirical standard deviation of the second signal region.

9 . The method of claim 5 , wherein determining that the first signal region is inconsistent in comparison to the second signal region comprises determining that a mean of the first signal region is less than a mean of the second signal region minus a product, wherein the product comprises a predetermined input multiplied by an empirical standard deviation of the second signal region.

10 . The method of claim 5 , wherein determining that the first signal region is inconsistent in comparison to the second signal region comprises determining that a mean of the first signal region is greater than a mean of the second signal region plus a product, wherein the product comprises a predetermined input multiplied by an empirical standard deviation of the second signal region.

11 . The method of claim 5 , wherein the first change point is identified in a predetermined portion of the signal using a change point detection algorithm, wherein the second change point is identified in a predetermined portion of the derivative signal using the change point detection algorithm, wherein the predetermined portion of the signal at least partially overlaps with the predetermined portion of the derivative signal, and wherein the change point detection algorithm is selected from the group consisting of a binary segmentation algorithm, a segment neighborhood algorithm, and a pruned exact linear time (PELT) algorithm.

12 . The method of claim 5 , wherein the second signal region represents a depth that at least partially overlaps with depths represented by the third signal region, the fourth signal region, or both.

13 . The method of claim 5 , further comprising removing the first signal region from the signal prior to producing the derivative signal such that the derivative signal does not include the first signal region.

14 . The method of claim 5 , further comprising removing the first signal region from the signal prior to determining the second change point such that the second change point is not located within the first signal region.

15 . The method of claim 5 , wherein the first change point, the first signal region, and the second signal region are in a first portion of the signal, wherein the second change point, the third signal region, and the fourth signal region are in a first portion of the derivative signal, the method further comprising:

identifying in a second portion of the signal a third change point that demarcates a fifth signal region and a sixth signal region;

determining that the sixth signal region of the signal is inconsistent in comparison to the fifth signal region; and

adjusting the modified well log by removing the sixth signal region from the signal in response to determining that the sixth signal region of the signal is inconsistent in comparison to the fifth signal region.

16 . The method of claim 15 , further comprising:

identifying in a second portion of the derivative signal a fourth change point that demarcates a seventh signal region and an eighth signal region;

determining that the eighth signal region of the derivative signal has a value that is substantially zero; and

adjusting the modified well log by removing the eighth signal region from the signal in response to determining that the eighth signal region of the derivative signal has the value that is substantially zero.

17 . The method of claim 5 , further comprising:

receiving a second well log comprising a second signal;

positioning a first window within the modified well log;

positioning a second window at a first location within the second well log;

determining a first similarity value between the signal in the first window and the second signal in the second window at the first location;

repositioning the second window at a second location within the second well log;

determining a second similarity value between the signal in the first window and the second signal in the second window at the second location;

selecting the first location or the second location of the second window based at least partially upon the first and second similarity values; and

producing a modified second well log based at least partially upon the selected first location or second location of the second window.

18 . A computing system comprising:

one or more processors; and

a memory system comprising one or more non-transitory computer-readable media storing instructions that, when executed by at least one of the one or more processors, cause the computing system to perform operations, the operations comprising:

receiving a first well log comprising a first signal and a second well log comprising a second signal;

identifying in the first signal a first change point that demarcates a first signal region and a second signal region;

determining that the first signal region of the first signal is inconsistent in comparison to the second signal region;

producing a derivative signal by calculating a derivative of at least a portion of the first signal;

identifying in the derivative signal a second change point that demarcates a third signal region and a fourth signal region;

determining that the third signal region of the derivative signal has a value that is substantially zero;

producing a modified first well log by removing the first signal region from the first signal in response to determining that the first signal region of the first signal is inconsistent in comparison to the second signal region, and by removing the third signal region from the first signal in response to determining that the third signal region of the derivative signal has the value that is substantially zero;

selecting a third change point in the modified first well log and a fourth change point in the second well log;

positioning a first window within the modified first well log based at least in part on the third change point;

positioning a second window at a first location within the second well log based at least in part on the fourth change point;

determining a first similarity value between the first signal in the first window and the second signal in the second window at the first location;

repositioning the second window at a second location within the second well log based at least in part on the fourth change point;

determining a second similarity value between the first signal in the first window and the second signal in the second window at the second location;

selecting the first location or the second location of the second window based at least partially upon the first and second similarity values; and

producing a modified second well log based at least partially upon the selected first location or second location of the second window.

19 . A computing system comprising:

one or more processors; and

a memory system comprising one or more non-transitory computer-readable media storing instructions that, when executed by at least one of the one or more processors, cause the computing system to perform operations, the operations comprising:

receiving a well log comprising a signal;

identifying in the signal a first change point that demarcates a first signal region and a second signal region;

determining that the first signal region is inconsistent in comparison to the second signal region;

producing a modified well log by removing the first signal region from the signal in response to determining that the first signal region is inconsistent in comparison to the second signal region;

producing a derivative signal by calculating a derivative of at least a portion of the signal;

identifying in the derivative signal a second change point that demarcates a third signal region and a fourth signal region;

determining that the third signal region of the derivative signal has a value that is substantially zero; and

adjusting the modified well log by removing the third signal region from the signal in response to determining that the third signal region of the derivative signal has the value that is substantially zero.