Generating a Cylindrical Panorama from a Forward-Looking Borehole Video for Borehole Condition Analysis

Abstract

Geological exploration plays a fundamental and crucial role in geological engineering. The most frequently used method is to obtain borehole videos using an axial view borehole camera system (AVBCS) in a pre-drilled borehole. This approach to surveying the internal structure of a borehole is based on the video playback and video screenshot analysis. One of the drawbacks of AVBCS is that it provides only a qualitative description of borehole information with a forward-looking borehole video, but quantitative analysis of the borehole data, such as the width and dip angle of fracture, are unavailable. In this paper, we proposed a new approach to create a whole borehole-wall cylindrical panorama from the borehole video acquired by AVBCS, which provides a possibility for further analysis of borehole information. Firstly, based on the Otsu and region labeling algorithms, a borehole center location algorithm is proposed to extract the borehole center of each video image automatically. Afterwards, based on coordinate mapping (CM), a virtual coordinate graph (VCG) is designed in the unwrapping process of the front view borehole-wall image sequence, generating the corresponding unfolded image sequence and reducing the computational cost. Subsequently, based on the sum of absolute difference (SAD), a projection transformation SAD (PTSAD), which considers the gray level similarity of candidate images, is proposed to achieve the matching of the unfolded image sequence. Finally, an image filtering module is introduced to filter the invalid frames and the remaining frames are stitched into a complete cylindrical panorama. Experiments on two real-world borehole videos demonstrate that the proposed method can generate panoramic borehole-wall unfolded images from videos with satisfying visual effect for follow up geological condition analysis. From the resulting image, borehole information, including the rock mechanical properties, distribution and width of fracture, fault distribution and seam thickness, can be further obtained and analyzed.

An image-capturing system to generate 3D borehole models using multiple fiberscope cameras

“…However, the introscopic camera may lose texture information and sharpness due to the unevenness of the borehole. Deng et al [4] introduced a forward-looking borehole camera system to observe cyclic annular images. Even though one can observe the whole borehole at once through a conical mirror, the captured images tend to lose resolution which will significantly affect the following geological inspection.…”

Research on the processing algorithm of drilling image

“…Setp 2: Generate feature descriptor Only using key points as features can not ensure the consistency of the neighborhood, so the feature descriptor is introduced. Take 16 as the center × The neighborhood of 16 pixels generates feature descriptors, and then divides them into 4 × 16 sub-areas of 4, at 4 × Calculate the cumulative value of 8 gradient modulus values and directions on the subregion of 4, and then get a sub-region, as shown in Figure 6 (a) [11]. Step 3 Feature matching…”

Geological Borehole Video Image Stitching Method Based on Local Homography Matrix Offset Optimization

“…It has become one of the important methods in geological exploration [ 2 ]. The borehole video captured using the axial view panoramic borehole camera system (APBCS) can be converted into a borehole wall unfolded image sequence, and a complete borehole panorama that intuitively reflects the characteristics of the borehole wall’s structural plane can be constructed by using image stitching method [ 3 ]. Using the panorama, the trend, crack width, rock mass interface and other information about the rock mass structural plane can be analyzed from the macro perspective, which provides a research basis for further qualitative analyses of borehole data.…”