3D Quantitative Characterization of Fractures and Cavities in Digital Outcrop Texture Model Based on Lidar

Bo Liang,Yanlin Shao,Yuangang Liu,Qing Wang,Shaohua Li,Naidan Zhang

doi:10.3390/en15051627

Abstract

The combination of lidar and digital photography provides a new technology for creating a high-resolution 3D digital outcrop model. The digital outcrop model can accurately and conveniently depict the surface 3D properties of an outcrop profile, making up for the shortcomings of traditional outcrop research techniques. However, the advent of digital outcrop poses additional challenges to the 3D spatial analysis of virtual outcrop models, particularly in the interpretation of geological characteristics. In this study, the detailed workflow of automated interpretation of geological characteristics of fractures and cavities on a 3D digital outcrop texture model is described. Firstly, advanced automatic image analysis technology is used to detect the 2D contour of the fractures and cavities in the picture. Then, to obtain an accurate representation of the 3D structure of the fractures and cavities on the digital outcrop model, a projection method for converting 2D coordinates to 3D space based on geometric transformations such as affine transformation and linear interpolation is proposed. Quantitative data on the size, shape, and distribution of geological features are calculated using this information. Finally, a novel and comprehensive automated 3D quantitative characterization technique for fractures and cavities on the 3D digital outcrop texture model is developed. The proposed technology has been applied to the 3D mapping and quantitative characterization of fractures and cavities on the outcrop profile for the Dengying Formation (second member), providing a foundation for profile reservoir appraisal in the research region. Furthermore, this approach may be extended to the 3D characterization and analysis of any point, line, and surface objects derived from outcrop photos, hence increasing the application value of the 3D digital outcrop model.

Highlights

Field outcrop is an essential research object in geological work and plays a crucial part in the process of oil and gas geological exploration and development [1,2,3]
There are on digital outcrop model (DOM), fractures lines closely attached to the triangular surface
This research proposes a scheme for 3D quantitative characterization of fractures and cavities in the digital outcrop texture model based on lidar

Summary

Introduction

Field outcrop is an essential research object in geological work and plays a crucial part in the process of oil and gas geological exploration and development [1,2,3]. Geologists used photos to depict outcrops by hand drawing and physically measured outcrops using conventional equipment such as a geological compass and ruler. This traditional approach of outcrop study has two obvious disadvantages: (1) operation: based on traditional methods, field mapping in high slopes or unstable areas (desert, arctic, etc.) is very timeconsuming and dangerous [4,5]; (2) application: traditional methods represent a much more varied approach and analysis (e.g., measurements, stereograms, and cross-sections are used when the geometry is important). Traditional methods for interpreting geological features only use Geologists are frequently interested in multiscale geological features of the outcrop surface in the process of interpreting digital outcrops, such as fractures, bedding, cavities, etc. There are three different types of digital outcrop interpretation methods: (1) manual interpretation: researchers manually draw the target object on the digital outcrop surface; (2) automatic interpretation: researchers use computer programs to extract relevant geological features automatically; (3) semiautomatic interpretation: researchers used the method of integrating manual and automatic interpretation

Methods

Results

Conclusion