Abstract

Fractures have always been a controversy whether they are open or healed, continuous or discontinuous; they are usually in the subsurface and they always have a big impact on the reservoir. This impact can be sweet or sour. It all depends how these fractures connect within the reservoir as open fractures are considered to be open conduits. So fractures can connect to get a better hydrocarbon flow or they can end up connecting the reservoir to water. Therefore the more we know about fractures, the easier would be to understand their behavior. Particularly, presence of natural fractures can indicate potentially better reservoir quality (RQ) as well as provide information for better completion quality (CQ).

This study covers the implementation of a new integrated workflow using high-definition LWD Imaging for fracture identification and analysis. Borehole Imaging tools have a long history in the identification and more important quantification of fractures in boreholes when using water base mud. This approach has been revisited when using wireline imaging tools and then was extended to LWD tools.

The enhancements in LWD resistivity images are changing the approach to lateral well borehole geological interpretation especially for horizontal wells where Wireline acquisition can be an issue. LWD borehole images can now give more useful information about fractures. This includes their orientation, density of fractures per unit length of borehole, the aperture of these fractures and fracture porosity. When picking the fractures manually, fractures can be classified in different fracture sets depending on their type and orientation. However when we are dealing with small fracture segments, we can easily miss many of those and therefore not accurately evaluate the reservoir.

The new workflow demonstrated in this study is used to identify continuous and discontinuous fracture segments by a fast automatic extraction. Fracture segments are then filtered based on different criteria (including length and orientation). After computing fracture aperture, fracture density and porosity are then accurately calculated along the well. This enabled quantification and characterization of the fracture network, including a fast and easy recognition of intervals with specific aperture or porosity ranges. This study will show different examples using high definition LWD resistivity images and the impact of this workflow on the processing time but also on the reservoir completion design.