Fracture Detection from Geothermal Well Logs

Abstract

Most of the geothermal systems in the world are fractured. In many systems, fractures provide the only pore spaces, serving both storage and flow capacities, while in others fractures may provide a large flow capacity but not contribute significantly to storage capacity. In either case, fracture detection becomes an indispensible step in the development of a well.

There are several ways of detecting fractures: from drilling and workover information, from well logs and flow tests of wells.This paper will discuss the state-of-the-art of fracture detection from geothermal well logs and provide a case history.

Assessment of a fractured reservoir requires not only detection of depth of occurence), orientation (whether horizontal, vertical or inclined; angle and direction of dip), aperture (width), extent of filling (open, filled, or partially filled), and habit (single fracture, set of parallel fractures, cross joints, or rubble-like geometry).