Unconventional Use of Tracer Technology Provides Flow Insights for EOR, IOR
Authors: Carpenter Chris 
Published: September 2023

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This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 207431, “Advanced Research and Development in Unconventional Use of Tracer Technology for EOR and IOR: What Lies Beyond?” by Monalisa Chatterjee and Sean Toh, Tracerco, and Ahmed Alshmakhy, SPE, ADNOC, et al. The paper has not been peer reviewed.

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In recent decades, tracers have provided crucial insight into fluid-flow behavior in assessing reservoir connectivity. While advancements in versatility of tracer molecules have been published before in the literature, to the best of the authors’ knowledge, no work has been published to date that discusses the latest advances in unconventional uses of tracer molecules aiding enhanced oil recovery (EOR) and improved oil recovery (IOR) processes. This work is meant to address that gap by exploring four unconventional uses of tracers that hold significant potential.

Microencapsulation of Solid Tracers: Enhancing Intelligent Tracers
Previous research specified that factors affecting the current technology of solid tracers include physical space restrictions, temperature, tracer-loading capacity, initial surge, release of the tracer into fluid, and target-tracer concentrations.
While the first two factors often are dictated by project conditions, advances in the other factors have been largely attributed to the tracer-polymer composition. For the tracers to be released in a controlled manner across a designated period, polymer structure plays a pivotal role in achieving longevity.
The complete paper discusses a technique that is an application revolving around microencapsulation of chemical tracers in a solid shell before the addition of polymer material.
Encapsulation vs. Microencapsulation. The encapsulation technique is a complex process involving selection of compatible molecular carriers, understanding their effects, and building the appropriate encapsulation (usually molecular encapsulation) to ensure that the capsules meet the desired outcome of each study. In this paper, an advanced subset of encapsulation—microencapsulation—is presented and its applications in inflow chemical tracing are discussed.
Microencapsulation involves a particle, usually of micrometer dimensions, comprising a core material surrounded by a wall material significantly different from that of the core. The difference between them mainly arises from the morphology and the internal structure.
The process allows the active ingredient to be protected from adverse external environmental conditions by the encapsulating coating agent.
By applying the microencapsulation technique, the release profiles of tracers can be further controlled by changing the thickness, material, and morphology of the encapsulating agent. When applied onto tracers, this changes the tracer-release mechanism to a two-step, instead of the typical one-step, process. Oil tracers that generally are oleophilic will be released when in contact with oil; similarly, water tracers that are hydrophilic will be released when in contact with water. The tracers will remain dormant until the phase of interest encounters the polymer bars, and the two-step process allows the encapsulating agent to further improve the longevity of the tracers.