A Step Change for Single-Well Chemical-Tracer Tests: Field Pilot Testing of New Sets of Novel Tracers

Abstract

Summary The single-well chemical-tracer test (SWCTT) is an in-situ test to measure oil saturation, and has been used extensively to assess the potential for enhanced oil recovery (EOR) or to qualify particular EOR chemicals and methods. An SWCTT requires that a primary tracer be injected and that a secondary tracer be generated from the primary tracer in situ. Typically, a few hundred liters of ester is injected as primary tracer, and the secondary tracer is formed through hydrolysis in the formations. The ester is an oil/water-partitioning tracer, whereas the in-situ-generated alcohol is a water tracer. During production, these tracers separate and the time lag of the ester vs. the alcohol is used to estimate oil saturation in the near-well region. In this paper, we report a field test of a class of new reacting tracers for SWCTTs. In the test, approximately 100 cm3 of each of the new tracers was injected and used to assess oil saturation. In the test, ethyl acetate (EtAc) was used as a benchmark to verify the new tracers. This paper reviews the design and implementation of the test, highlights operational issues, provides a summary of the analyzed tracer curves, and gives a summary of the interpretation methodology used to find oil saturations from the tracer curves. Briefly summarized, we find the Sor measured by each of the novel tracers to compare with that from a conventional SWCTT. To validate stability and detectability of the tracers, a mass-balance assessment for the new tracers is compared with that of the conventional tracers. A benefit of the new tracers is the small amount needed. Methodological advantages resulting from using small amounts include the possibility to inject a mix of several tracers. Using several tracers with different partitioning coefficients enables probing of different depths of the reservoir. In addition, the robustness of SWCTTs can be increased by using several tracers, with different reaction rates and temperature sensitivity. The field trial also demonstrated that the new tracers have operational advantages. One benefit is the possibility to inject the new tracers as a short pulse of 10 minutes. Other benefits are that the small amounts needed reduce operational hazards and ease logistical handling.

Development of new oil/water partitioning tracers for the determination of residual oil saturation in the inter-well region of water-flooded reservoirs

“…It was necessary to identify and quantify these compounds in produced waters from oilfield in concentrations of low µg/L, or, ideally, even lower. The lowest possible LOQs are desirable to increase the accuracy of the recorded tracer production curves while simultaneously reducing the amount of chemicals used in the test (AlAbbad et al, 2018;. This is particularly an important factor in offshore operations due to HSE and logistic issues and large well distances.…”

Design, synthesis and performance of novel fluorescent polymer microspheres tracers based on aggregation induced emission

“…The fluorescent polymer microspheres tracers prepared as 0.2 mg/L fracturing fluid suspension and heated at different temperatures (25,50,80,110, and 140 C) for 1 h, then the fluorescence emission spectra of the mixture were tested after it cooled down to room temperature. The pH of the aqueous solution was adjusted by sodium hydroxide and hydrochloric acid, and then a 0.2 mg/mL suspension of the fluorescent polymer microspheres was prepared to test the fluorescence emission spectra at different pH (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14). The suspension of fluorescent polymer microspheres was also left under natural conditions for 30 days and their fluorescence emission spectra were S C H E M E 1 Synthesis route of fluorescent microspheres tested every 5 days.…”

“…[7][8][9] The tracers can return the underground situation to the ground through signals, which can better assist in the field survey of oil reservoirs (including inter-well connections, inter-layer connections and heterogeneity). [10][11][12] Many tracers have been used in dynamic monitoring, evaluation of oilfield production, 13,14 improving recovery measures and so on.…”

Detailed numerical evaluation of diffusion convection equation in layered reservoirs during tracer injection

“…Kumar et al reported that the combination of tracer data, completion data and also stimulation data in a machine-learning framework could show better dynamic behavior in a fracture network system 29 . Also a brief history of activities performed in the analysis of tracers is presented in Appendix C 11 , 12 , 16 , 18 , 24 , 30 – 57 .…”