Some Recent Applications Of Radioactive Tracers In Determining Subsurface Flow Behavior
Authors: Champion C.A. , Schaller H.E. , Jackson B.R. 
Published: December 2007

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This paper was to be presented at the 40th Annual Fall Meeting of the Society of Petroleum Engineers of AIME, to be held in Denver, Colorado, October 3–6, 1965, and is considered to an abstract of not more than 300 words, with no illustrations, unless the paper is specifically released to the press by the Editor of the Journal of Petroleum Technology or the Executive Secretary. Such abstract elsewhere after publication in the Journal of Petroleum Technology or Society of Petroleum Engineers Journal is granted on request, providing proper credit is given that publication and the original presentation of the paper.
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Abstract
The use of radioactive isotopes as tracers provides a rapid, generally quantitative and economically feasible means of determining movements of fluids in and adjacent to a wellbore Special wireline equipment permits storing and transporting the tracer material, releasing it in variable quantities at depths and times desired" and transmitting the detected information to surface recorders. Radioactive tracers have been successfully used to determine water entry and migrations, to control selective placement of plugging materials, to test zone segregation and water shutoff, to determine injection profiles, to prove effectiveness of packer seals, and to augment other surveys.

Introduction
Secondary-recovery projects often have multiplied producing problems and consequent remedial operations. Knowledge of the wellbore-flow behavior of injection and producing wells is often necessary to effectively perform these remedial jobs. This is particularly true in thick-sectioned reservoirs with numerous independent oil-bearing strata open to a common wellbore.
For several decades, surveys such as "water witching" have been used as a means of determining points of fluid entry into a wellbore. Also, continuous surface-recording spinner surveys have provided reliable injectivity profiles of wells except when there are such special conditions as very low injection rates, high-angle holes or short injection intervals.
The availability of a variety of radioactive isotopes, together with the development of suitable equipment and techniques, has provided the industry with an additional valuable tool for determining wellbore flow behavior. The application of radioactive isotopes to the solution of many remedial, drilling, and completion problems appears to be limited only by the imagination of the petroleum engineer faced with these problems. This paper presents some current applications of radioactive tracers in the determination of wellbore flow behavior, particularly in fluid injection projects. Some of these, such as the determination of water entry, water migration, and injection profiles, have been applied extensively and have become routine operations.