Applications of Borehole Imaging to Hydrocarbon Exploration & Production

Introduction to borehole imaging technology

We review the different principles of measurement and applications of wireline and logging while drilling imaging tools. Through exercises based on various geological environments, logging conditions and logging objectives the participants learn to determine the most relevant imaging tool for each scenario. We go through the different steps of the image processing chain that converts raw data into images suitable for geological interpretation.

Wellsite inclinometry and image quality control

Geological analysis of borehole images is performed on images that have been properly quality controlled and processed in a computing center. However, logging operations sometimes require that well site images are interpreted for quick decision making. Quality control of well site inclinometry and image data is of upper most importance. Through exercises based on well site data of resistivity and acoustic imaging tools participants learn how to identify common inclinometry and image acquisition problems and to interpret well site images.

Dipmeter computation and interpretation principles

Before the introduction of image logs in the early eighties the only dips available for geologists were computed from mathematical correlations of resistivity curves derived from dipmeter tools. We will look at the basic dip algorithms that were specifically developed for dipmeter tools and that are still applicable to dips derived from image logs. Through simples exercises involving structural and sedimentary dips we review the interpretation rules that were developed solely from dip data for structural applications (structural dip, faults, unconformities) and sedimentary applications (identification of sedimentary structures and heterogeneities).

Structural Interpretation of borehole images

Structural analysis consists in identifying and characterizing structural features such as structural dip, unconformities, faults and stress. After an introduction to the general workflow for structural analysis we go through the different statistical tools allowing structural delineation from dips AND image logs. We review the principle of dip stereonet diagrams and see how Schmidt stereonets can be used to extract structural parameters from dip data such as fold axis, axial plane or the relationship between fractures and bedding

Structural Interpretation of borehole images (cont. d)

Advanced stereonet techniques for 2D and 3D structural modeling from dips are introduced. We see how dip derived structure models can be integrated into structural models derived from 3D seismic data in Petrel.

Fracture, fault and stress characterization from borehole images

After an introduction on the basics on rock mechanics, the mechanism of rock failure leading to fractures or faults is illustrated with core and outcrop examples. Through examples and exercises participants learn how fractures and faults can be characterized from image logs both in vertical wells and horizontal wells.

Fracture, fault and stress characterization from borehole images (cont. d)

We review the different types of stress related features that can be identified on image logs and the information they provide on the stress direction and intensity. We see how fracture contribution to the reservoir permeability can be better characterize after fractures, faults and stress related features are integrated with sonic and dynamic data.

Sedimentary interpretation of borehole images

We go through the general workflow for sedimentary analysis from image logs and review the scales and definitions of sedimentary structures. We see how image logs can be used to identify and characterize sedimentary structures of various depositional environments, which include continental fluvial, deltaic, shallow marine, deep marine, eolian, carbonate build-up and glacial environments. We see how textural information extracted from image logs can be combined with open-hole data to derived electro-facies in carbonate and clastic reservoirs. Finally, after a brief introduction to the principles of sequence stratigraphy, participants see through selected examples how small scale resolution images can be used to generate more robust sequence stratigraphy models that are usually based on much larger scale seismic and open-hole log data.