Fast and objective detection and analysis of structures in downhole images

Transcription

1 Fast and objective detection and analysis of structures in downhole images Daniel Wedge Eun-Jung Holden, Mike Dentith, Nick Spadaccini Centre for Exploration Targeting The University of Western Australia

2 Background Borehole structure analysis is important in many applications: Petroleum: understanding fluid flow Mineral exploration: mineralisation Mine site design: structural integrity Manually picking structures is: Subjective Time consuming

3 Background Rio Tinto Iron Ore funded this project from Hundreds of kilometres of logs collected annually Structure picking is a significant bottleneck in processing Need for automated analysis Geologists don t trust a black box Interactive workflow for rapidly processing logs Provide feedback to user Harness geologists experience

4 Why sinusoids? Malcolm Rider, The Geological Interpretation of Well Logs.

5 Optical televiewer image (OTV) Types of logs Acoustic televiewer image (ATV) Formation micro imager (FMI) Data courtesy of Advanced Logic Technology

6 Why is this difficult? Optical televiewer image (OTV) Acoustic televiewer image (ATV) Formation micro imager (FMI) Complex geology Indistinct structure Missing data (gaps between pads) Data courtesy of Advanced Logic Technology Only partial structures shown

7 Our approach Analyse the image as a whole, not just the structures Provide user with feedback on suitability of zones for automated processing Automatically detect planar structures in downhole images and provide confidence values for results Interactive geologist retains control Various features for optimising processing Utilising structure confidence values Rapidly detect further structures Process using structure orientation information as well as depth information

8 Drill and log Zonation Structures Analyse structure confidence Assisted rapid detection Represent. picks Flow / block model Stability analysis Workflow Automatically detect geological zones Detect structures for each zone Structure confidence apply confidence threshold for each zone Structure hints rapidly see new structures just by moving mouse Automatically select representative picks for a zone Use structures for modelling etc.

9 Drill and log Zonation Structures Analyse structure confidence Assisted rapid detection Represent. picks Automatic zone detection Image quality varies due to geology (complexity of structures) and imaging conditions No one-size-fits-all algorithm for detecting structures Image confidence indicates which areas are best for automated processing Based on texture characteristics Used for finding zone boundaries Flow / block model Stability analysis

10 Drill and log Image confidence Zonation Structures Analyse structure confidence Assisted rapid detection Represent. picks Flow / block model Stability analysis

11 Drill and log Zonation Structures Analyse structure confidence Structure detection Detect various types of sinusoids Each detected structure has a structure confidence. Confidence value displayed graphically Visual feedback on algorithm s performance Confidence used for interactively selecting structures ATV image Structures Structure conf Tadpole plot Assisted rapid detection Represent. picks Flow / block model Stability analysis

12 Drill and log Structure detection Zonation Structures Analyse structure confidence Assisted rapid detection Represent. picks Flow / block model Stability analysis

13 Drill and log Zonation Structures Rapid detection of similar structures Copy one structure to fit nearby image features to form sets Analyse structure confidence Assisted rapid detection Represent. picks Flow / block model Stability analysis Detected structures also have structure confidence which can be used for thresholding etc.

14 Sets

15 Drill and log Zonation Structures Analyse structure confidence Assisted rapid detection View structures: By structure type By depth By orientation Stereonet Interact with structures Adjust structure confidence threshold Change structure classification Toggle visibility of structure types Represent. picks Flow / block model Stability analysis

16 Stepping through zones

17 Stepping through zones

18 Stepping through zones

19 Stepping through zones

20 Stepping through zones

21 Drill and log Zonation Structures Analyse structure confidence Assisted rapid detection Representative picks Different teams may have different objectives e.g. structure orientations vs density of structures Representative picks are a subset of alreadypicked structures Based on orientation, depth separation and structure confidence values Avoid duplicating structures Objective and rapid Represent. picks Flow / block model Stability analysis

22 All structures

23 Representative picks

24 Drill and log Zonation Structures Analyse structure confidence Assisted rapid detection Summary We have developed a system and workflow for assisting geologists to rapidly detect and analyse planar structures in downhole image logs. Interactive approach empowers geologists to make more effective use of their time and skills. Fast, objective and repeatable. Represent. picks Flow / block model Stability analysis

25 Future development We are currently working with Advanced Logic Technology to integrate this work into the release of WellCAD v5.1. New ISIS (Image & Structure Interpretation System) module will incorporate this workflow. Expected release: Late fall 2014.