1887

Abstract

Summary

To understand the alterations in geomechanical and mineralogical properties of reservoir chalk injected with seawater, countless experiments have been carried out through decades of research at UiS. Several parameters are varied to understand how these parameters impact fluid-flow, rock-fluid interaction and compaction, which is an important drive mechanism for Enhanced Oil Recovery (EOR). Identification of mineralogical alterations is crucial input to modelling and simulation of EOR methods.

We present the results from flow through experiments on Liège chalk from three ultra-long-term tests. The core were flooded with MgCl2 at reservoir temperature (130°C) and hydrostatic stresses above yield (9.5, 10.4 and 12.6 MPa), with one core was flooded for a short period with a mixture of MgCl2 and CaCl2, and with MgCl2 brines at different pH, ~2.7, ~5.7 and ~9.

The studies based on Mineral Liberation Analyzer and Transmission Electron Microscopy show two fronts moving through the cores at different velocities. The first alterations are partial dissolution of calcite with precipitation of secondary minerals like high-magnesium carbonate and clays, followed by fronts of complete transformation to the Mg-rich mineral. Random calcium impurities (<4wt%) are present in all analysed magnesite crystals. In addition, precipitation of Si-Mg-bearing clays is observed throughout all flooded cores.

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/content/papers/10.3997/2214-4609.201700308
2017-04-24
2020-04-09
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