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A New Frontier Technique for Nano-analysis on Flooded Chalk - TERS (Tip Enhanced Raman Spectroscopy)
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, IOR 2017 - 19th European Symposium on Improved Oil Recovery, Apr 2017, Volume 2017, p.1 - 10
Abstract
Understanding the chalk-fluid interactions at the sub-micron scale is one of the most challenging goals in Enhanced Oil Recovery. The grain size of newly grown minerals far below 1 micron asks for a high performing imaging: we present a new methodology using the TERS (Tip Enhanced Raman Spectroscopy), a new frontier technique that combines Raman Spectroscopy with Atomic Force Microscopy, allowing impressively high-resolution chemical analyses down to an outstanding spatial resolution (~ 20 nm). TERS permits the recognition of minerals thanks to the vibrational mode peaks that are diagnostic of composition and structure. Carbonate-group minerals are easily identified by Raman spectroscopy. First analyses allow us to state that magnesite and calcite could be identified in, respectively, ultra-long-term flooding experiments of chalk at reservoir conditions and in unflooded samples; no dolomite or high Mg-calcite have been found. Few microns squared areas have been imaged by AFM using ultra polished thin sections with a 50 nanometers step.
Transmission electron microscopy has been employed to confirm the results of TERS and add dark and bright field grain-imaging to the investigations.
This confirms the need for high-resolution methodology such as TERS and TEM to fully understand EOR effects at sub-micron scale.