Fractures

This document details Datarock’s products Fracture Frequency and Spacing.

Contents

Dependent Models

The outputs of the following models are used to determine Fracture Frequency and Spacing:

Model Name

Model Type

Fracture Detection and Classification

Object Detection

Drillers Break

Object Detection

Data Processing

The outputs of the Fracture Detection & Classification and Drillers Break models are combined to create an understanding of natural fractures, allowing fracture frequency to be calculated. 

Detection of Fractures and Mechanical Breaks

Several fracture types are detected by the Fracture Detection and Classification model, and are summarised in the table below.

In addition, drillers break marks are detected by the Drillers Break model to differentiate between natural and mechanical breaks. If a drillers break mark is located within 5cm of a fracture detection, the fracture will be flagged as mechanical.

The following images show example detection and classifications of fractures. In the second row, first fracture from the left, it can be seen that no fracture shown due to the presence of the drillers break marks.

 

Fracture Counts

To calculate the fracture frequency, Datarock calculates an Equivalent Fracture Count for a given interval using the equivalent counts shown below. In addition to counting each fracture detection, the equivalent fracture counts are applied to incoherent zones.

Fracture Type

Description

Equivalent Fracture Count

Measurable

A fracture, with single interface and clear shadow line that allows structural measurements automatically approximated.

1

Displaced

A fracture, with single interface, however either one or both pieces of core have dislodged/ rotated from their original position creating a physical gap between fracture edges.

1

Jigsaw

Multiple fractures that intersect each other with pieces well fitted together or slightly displaced

2 fractures / 100mm

Broken

Multiple fractures that intersect each other that do not fit together well with larger spaces between them between them

4 fractures / 100mm

Rubble

Multiple pieces of small rocks, pebbles, fine rubble and/or powder between two pieces of core

5 fractures / 100mm

The resultant equivalent fracture count is then used to calculate the fracture frequency and spacing for given intervals.

Product Configuration Options

The equivalent fracture counts can be configured via the Fracture detection tab access via the settings cog next to the name of your project page.

Once in this tab, you can then edit the equivalent fracture counts for Jigsaw, Broken and/or Rubble to better match your own equivalent fracture counts (see below). These are preset to the default counts Datarock uses as described above.

Note: you will need to click Submit to save the edits and then re-run the Fractures product to process the results using the new equivalent fracture counts.

Output Intervals

Default interval length: 1.0m

Customisable interval available: Yes, via uploading sample table to platform (see User Data below)

User Data

User data may be uploaded to the platform via csv in the following format:

·       HoleID_sampling_intervals_fractures.csv

CSV file to contain the following headers:

File Header

Description

depth_from

Start of interval

depth_to

End of interval

fractures

Number of natural fractures counted on site

Data Output

Results from this class of models can be obtained using the Download artefacts option from the Actions button in the Model Review tab of Datarock. The available CSV files include the following:

·       ProjectID_HoleID_fracture_frequency_by_metre.csv

·       ProjectID_HoleID_fracture_frequency_by_user_intervals.csv

·       ProjectID_HoleID_fracture_location.csv

 

The first two CSV files contain the following headers:

File Header

Description

hole_id

Customer’s Hole ID

depth_from_m

Start of interval (metres)

depth_to_m

End of interval (metres)

depth_from_ft*

Start of interval (feet)

depth_to_ft*

End of interval (feet)

interval_metres

Length of interval in metres

fracture_count

Number of simple fractures detected

equivalent_fracture_count

Fracture_count plus equivalent fracture count for jigsaw, broken and rubble zones

mechanical_fracture_count

Number of detected fractures within threshold distance from detected drillers break marks

driller_break_mark_count

Number of drillers break marks detected

fractures_per_metre

Calculation of fracture_count divided by interval_metres

equivalent_fractures_per_metre

Calculation of equivalent_fracture_count divided by interval_metres

timestamp

Time of model prediction

fracture_spacing

Inverse of equivalent_fractures_per_metre

fracture_spacing_category

Categorised description of the fracture spacing

version

A model version identifier

*Only included if project depths are in feet.

 

  • ProjectID_HoleID_fracture_location.csv provides data for each individual fracture and contains the following headers

File Header

Description

hole_id

Customer’s Hole ID

fracture_uuid

Universally unique identifier for the fracture

depth_from_m

Start depth of the fracture bounding box (metres)

depth_to_m

End depth of the fracture bounding box (metres)

depth_from_ft*

Start depth of the fracture bounding box (feet)

depth_to_ft*

End depth of the fracture bounding box (feet)

depth_centre

Centre depth of the fracture bounding box. This is used as the actual depth of the fracture

fracture_class

The class of fracture as predicted by the object detection model

probability

The probability, or model’s confidence, of the fracture detection

type

Natural or mechanical fracture

row_uuid

Universally unique identifier for the row that contains the fracture

row_url

Datarock URL that contains the fracture

bounding_box_scaled

Coordinates in the image of the depth registered fracture bounding box

inference_timestamp

Time of model prediction

version

A model version identifier

*Only included if project depths are in feet.

Product Limitations

Limitations

Comments

Fracture count based on assumed equivalent fracture count in broken zones

This method is based on counting individual simple, single interface fractures, and assumed equivalent fracture counts for broken zones. It is recommended that these assumptions be verified based on customer’s logging schema.

Reliance on drillers break mark detection 

Mechanical breaks are very difficult to classify from a photo, therefore Datarock’s Fracture analysis relies on these breaks being visually identified, usually with a cross adjacent to the break.

If mechanical breaks are not identified, the resulting fracture counts will generally be higher than the site logging.

Document Version

Version

Date

Author

Rationale

1

6 October 2022

S Johnson

Initial release

2

25 January 2023

S Johnson

Update mechanical break description

3

29 January 2024

S Johnson

Update to include depths in feet

4

02 May 2024

N Pittaway

Update to include editing equivalent fracture counts

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