The Design and Implementation of Multiple Tracer Program for Multifluid, Multiwell Injection Projects
Authors: Wagner O.R. , Baker L.E. , Scott Gordon R. 
Published: December 2007

The Design and Implementation of Multiple Tracer Program for Multifluid, Multiwell Program for Multifluid, Multiwell Injection Projects
American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc.
This paper was prepared for the 49th Annual Fall Meeting of the Society of Petroleum Engineers of AIME, to be held in Houston, Texas, Oct. 6–9, 1974. Permission to copy is restricted to an abstract of not more than 300 words. illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor of the appropriate journal provided agreement to give proper credit is made. provided agreement to give proper credit is made. Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussions may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines.

Abstract
A tracer program utilizing both radioactive and chemical tracers was designed to trace the interwell movement of injected hydrocarbon solvent and water in the South Swan Hills Unit, Alberta, Canada. Fourteen solvent injection wells and 14 water injection wells were involved. An analytical solution to the diffusivity equation was developed to predict the tracer performance. Calculations were made using this analytical solution to determine the quantity of tracer to inject to produce a safe, detectable concentration, to predict the peak tracer concentrations in the produced stream over a broad range of breakthrough times, and to determine the required range of analytical sensitivity for monitoring samples of the produced stream. Other calculations made produced stream. Other calculations made indicate that it makes little difference, in the peak tracer concentration produced, whether a given amount of tracer is injected as a "spike" or is spread out over several days injection.
Critical factors tending to dilute the gas tracers were found to be diffusion, well pattern effects, dilution of gas tracers by pattern effects, dilution of gas tracers by solution gas in the separators, and the reduction in specific radioactivity due to expansion of the gas from reservoir pressure to surface pressure.

Introduction
A miscible displacement process was initiated in the South Swan Hills Unit, South Swan Hills Field, Alberta, Canada in July, 1973. This unit produces from the Beaverhill Lake formation. It was developed on 160-acre well spacing and comprises 221 wells, 21 of which are injectors. In this miscible flood operation rich hydrocarbon gas (solvent) is being injected alternately with water in approximately 30-day cycles. To gain information early in the life of this project about the interwell reservoir characteristics, relative fluid velocities, and volumetric sweep efficiency it was desirable to trace the interwell movement of both the injected solvent and water. Such information would be valuable in controlling the project performance through alterations in injection and withdrawal rates and through changes in the relative amounts of solvent and water injected at certain wells. Also, the tracer information will be a valuable aid in interpreting the project performance.
The radioactive tracers tritium, tritiated ethane, and krypton 85 were individually used in the first injected solvent cycle.