What are the best practices for quality control and interpretation of borehole images?

1 Data acquisition

The first step in obtaining borehole images is to select the appropriate logging tool for the objectives, formation, and well conditions. Different tools have different advantages and limitations in terms of resolution, coverage, depth of investigation, and environmental effects. For example, acoustic tools can image the entire borehole wall and penetrate beyond the invaded zone, but they are sensitive to mud noise and borehole rugosity. Electrical tools can measure the microresistivity of the formation and detect fractures and bedding, but they require good contact with the borehole wall and are affected by mud properties. Optical tools can capture the color and texture of the rock, but they need a clear borehole fluid and a smooth wall. Therefore, you should consider the trade-offs between these factors and choose the tool that best suits your needs.

2 Data processing

The next step in working with borehole images is to process the raw data and correct for any errors or artifacts that may affect the quality and interpretation of the images. Data processing involves several steps, such as depth matching, borehole shape correction, image calibration, filtering, normalization, and stitching. These steps aim to align the images with other logs, remove the effects of borehole geometry and tool motion, adjust the image contrast and brightness, enhance the image features, and combine the images from different sensors or passes. Data processing requires a good understanding of the tool response and the formation characteristics, as well as the use of specialized software and algorithms.

3 Image visualization

The third step in using borehole images is to visualize them in a way that facilitates the identification and analysis of the image features. Image visualization involves displaying the images in different formats, such as unwrapped, cross-sectional, or three-dimensional views, and using different color scales, contrast levels, or enhancement techniques. Image visualization also involves overlaying the images with other logs, such as gamma ray, resistivity, or porosity, to correlate the image features with the petrophysical properties. Image visualization helps to highlight the spatial distribution and orientation of the image features, such as fractures, bedding, faults, vugs, or borehole breakouts.

4 Image interpretation

The fourth step in applying borehole images is to interpret them in terms of the geological and geomechanical aspects of the formation. Image interpretation involves classifying and quantifying the image features, such as lithology, texture, mineralogy, facies, dip, fracture density, fracture aperture, fracture fill, stress direction, or borehole stability. Image interpretation also involves integrating the image data with other sources of information, such as core samples, seismic data, well tests, or reservoir models, to validate and refine the interpretation. Image interpretation requires a combination of expert knowledge, analytical skills, and software tools.

5 Image analysis

The fifth step in deriving value from borehole images is to analyze them for various purposes, such as reservoir characterization, geosteering, completion design, or production optimization. Image analysis involves extracting and applying the information from the image interpretation to address specific questions or challenges related to the reservoir performance and management. For example, image analysis can help to estimate the porosity, permeability, or fluid saturation of the formation, to identify the optimal well trajectory or landing zone, to select the best completion strategy or stimulation technique, or to monitor the reservoir changes or well integrity.

6 Best practices

To ensure the quality and usefulness of borehole images, it is essential to follow best practices throughout the process, from data acquisition to image analysis. This includes planning ahead and defining objectives, choosing the right tool and optimizing logging parameters, performing regular quality control checks and documenting any issues, using appropriate software and algorithms for data processing and image visualization, applying consistent criteria for interpretation and analysis, comparing and integrating the image data with other sources, and communicating and reporting the results effectively. By adhering to these best practices, you can maximize the potential of borehole images for your petrophysical projects.

7 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?