Tracer technology plays an important role in oilfield development and operation. Interwell tracer testing is an important reservoir engineering tool for the secondary and tertiary recovery of oil. Most of the oilfields in many developing countries are in the stage of secondary recovery. Moreover, the oil industry remains a priority in these countries. Interwell tracer testing is also used in geothermal reservoirs to gain better understanding of reservoir geology and to optimize production and re-injection programmes. Today, the use of tracers for interwell communication studies is an established technique.

The IAEA facilitates the transfer of technology, and an important part of this process is the provision of relevant literature that may be used for reference purposes or as an aid to teaching. This publication aims to provide not only an extensive description of what can be achieved by the application of radiotracer techniques in interwell investigations in onshore and offshore fields, but also sound and experience based guidance on all aspects of the design and implementation of experiments and the interpretation of results. It describes the principles and the state of the art of radiotracer techniques for interwell investigations.

The publication contains guidance on the technical steps of interwell tracer testing, as well as input from participants of the coordinated research project (CRP) on Validation of Tracers and Software for Interwell Investigations. The major achievements of the CRP and novel developments in tracer methodologies and technologies as applied to interwell investigations are also included. The unedited reports of the CRP participants, as presented at the final research coordination meeting, and software for interwell data interpretation are included as support materials on the accompanying CD-ROM. The publication has been prepared with contributions from all CRP participants. The IAEA gratefully acknowledges all contributors to this publication, especially T. Bjornstad for compiling and reviewing it.

The IAEA officer responsible for this publication was Joon-Ha Jin of the Division of Physical and Chemical Sciences.