A New Generation of Single Well Chemical Tracer Tests – Tracers and Methodologies
O. Huseby, C. Galdiga, S. Hartvig, G. Zarruk and Ø. Dugstad
Event name: IOR 2019 – 20th European Symposium on Improved Oil Recovery
Publication date: 08 April 2019
Info: Extended abstract, PDF ( 743.54Kb )
Price: € 20
The single well chemical tracer test (SWCTT) was introduced in the 1970ies by Deans and coworkers, and is commonly used to assess oil saturation in flooded reservoirs and to identify reduction in oil saturation after EOR. Reactive tracers are injected in a cylindrical volume in push-and-pull tests and the tracer hydrolyze in-situ to generate a secondary tracer. New SWCTT chemicals were piloted in a carbonate reservoir by Al Abbad et al. (2016), to overcome challenges such as flammability and the requirement for large amounts of chemicals associated with commonly used tracers, such as Ethyl Acetate. About 0.1 kg of the new tracers is sufficient, which should be compared to injected amounts up to several hundreds of kg for the traditional tracers. The reduced tracer amount opens for injection of a cocktail of tracers with different affinity to oil and the individual tracers will explore cylindrical volumes of different radii. This can be exploited to assess gradients in the oil saturation or the fractional flow of oil and water. The new tracers also opens for new and improved operational methodologies (in addition to the obvious related to reducing injection amount). Such improvements include adding tracers in the well using a simple injection system. The chemicals are designed to enable off-site analysis, thus removing the requirement to mobilize a chemical lab to the field. The injection of a cocktail of tracers gives tracer curve pairs of injected and in-situ generated tracers. This abundance of data required implementation of effective interpretation schemes that are also presented. In this paper, we summarize results findings from tests using the three new sets of tracer in sandstone and carbonate reservoirs. The paper summarizes design considerations and implementation of the tests, highlights operational improvements and demonstrate methods for interpretation of the results. The tracers are all shown to perform successfully at temperatures ranging from 50 – 100 C. They can all be injected simultaneously in a short pulse, and off-site analysis is shown to be a valid alternative to on-site analysis.