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Elastic and Plastic Behavior of Chalks at Deviatoric Stress Condition: Experiments Performed with Four Different Brines
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, IOR 2017 - 19th European Symposium on Improved Oil Recovery, Apr 2017, Volume 2017, p.1 - 14
Abstract
This paper deals with exploring elastic (bulk modulus and Young’s modulus) and plastic parameters (yield stress, creep and rebound) during deviatoric loading and time-dependent deformation. A series of experiments were carried out at Ekofisk reservoir temperature (130°C) to study the effect of four different fluids, viz., distilled water (DW), NaCl-brine, MgCl2-brine and seawater (SSW), on Mons outcrop chalk. The cores were deviatorically loaded and left to creep at a constant value of 69–73% of the axial yield stress obtained from reference tests with the same brine. Variations in the bulk modulus and Young’s modulus were observed as function of saturation fluid, although the significance of these observations require more data. SSW had the lowest yield stress followed by NaCl and MgCl2, and highest for DW, which conforms the results from earlier studies. The final creep strain was highest for SSW and was 1.3–1.5 times higher than for other brines. The core initially saturated by SSW showed the highest plastic component of the total strain inferring that the ions in SSW does play an important role in inducing permanent damage.