Evaluation of the compositional changes during flooding of reactive fluids using scanning electron microscopy, nano-secondary ion mass spectrometry, x-ray diffraction and whole rock geochemistryBulletin

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Authors
Udo Zimmerman, Merte Vadla Madland, Anders Nermoen, Tania Hildebrand-Habel, Silvana A. R. Bertolino, Aksel Hiorth, Reidar I. Korsnes, Jean-Nicolas Audinot, Patrick Grysan
Year
2015
DOI
10.1306/12221412196
Subject
Earth and Planetary Sciences (miscellaneous) / Geochemistry and Petrology / Geology / Energy Engineering and Power Technology / Fuel Technology

Text

GEOHORIZON

Evaluation of the compositional changes during flooding of reactive fluids using scanning electron microscopy, nano-secondary ion mass spectrometry, x-ray diffraction, and whole-rock geochemistry

Udo Zimmermann, Merete Vadla Madland,

Anders Nermoen, Tania Hildebrand-Habel,

Silvana A. R. Bertolino, Aksel Hiorth, Reidar

I. Korsnes, Jean-Nicolas Audinot, and Patrick Grysan

ABSTRACT

Outcrop chalk of late Campanian age (Gulpen Formation) from

Liège (Belgium) was flooded with MgCl2 in a triaxial cell for 516 days under reservoir conditions to understand how the nonequilibrium nature of the fluids altered the chalks. The study is motivated by enhanced oil recovery (EOR) processes because dissolution and precipitation change the way in which oils are trapped in chalk reservoirs. Relative to initial composition, the first centimeter of the flooded chalk sample shows an increase in

MgO by approximately 100, from a weight percent of 0.33% to 33.03% and a corresponding depletion of CaO by more than 70% from 52.22 to 14.43 wt.%. Except for Sr, other major or trace elements do not show a significant change in concentration.

Magnesite was identified as the major newly grown mineral phase. At the same time, porosity was reduced by approximately 20%. The amount of Cl− in the effluent brine remained unchanged, whereas Mg2+ was depleted and Ca2+ enriched. The loss of Ca2+ and gain in Mg2+ are attributed to precipitation of

Copyright ©2015. The American Association of Petroleum Geologists. All rights reserved.

Manuscript received November 15, 2012; provisional acceptance March 6, 2013; revised manuscript received November 27, 2013; revised manuscript provisional acceptance April 1, 2014; 2nd revised manuscript received May 23, 2014; final acceptance December 22, 2014.

DOI: 10.1306/12221412196

AUTHORS

Udo Zimmermann ∼ Department of Petroleum

Engineering, University of Stavanger, 4036

Stavanger, Norway; The National IOR Centre of

Norway, University of Stavanger, 4036

Stavanger, Norway; udo.zimmermann@uis.no

Udo Zimmermann is an associate professor at the

Department of Petroleum Engineering, University of Stavanger. Since his Ph.D. in geology, his research focus has concentrated on provenance studies and reservoir characterization using heavy minerals, and geochemical and isotope geochemical methods in clastic and chemical sedimentary rocks of Archean and

Phanerozoic ages.

Merete Vadla Madland ∼ Department of

Petroleum Engineering, University of Stavanger, 4036 Stavanger, Norway; The National IOR

Centre of Norway, University of Stavanger, 4036

Stavanger, Norway; merete.v.madland@uis.no

Merete Vadla Madland is an associate professor of reservoir engineering at the University of

Stavanger. For the last 17 years, she has worked on how to most effectively extract oil from reservoir rocks, and in the autumn 2013, she became the director of the national research center for improved oil recovery on the

Norwegian Continental Shelf.

Anders Nermoen ∼ The National IOR Centre of

Norway, University of Stavanger, 4036

Stavanger, Norway; International Research

Institute of Stavanger (IRIS), P.O. Box 8046, 4068

Stavanger, Norway; anders.nermoen@iris.no

Anders Nermoen is a senior research scientist at

IRIS. He holds a Ph.D. in physics from the

University of Oslo (Norway) and worked as a postdoctoral researcher at University of Ås (Norway) before starting a second postdoctoral research position at IRIS. His current research focuses on chemo-mechanical interplay across rock-fluid interfaces.

Tania Hildebrand-Habel ∼ The National IOR

Centre of Norway, University of Stavanger, 4036

Stavanger, Norway; International Research

Institute of Stavanger (IRIS), P.O. Box 8046, 4068

Stavanger, Norway; tania.hildebrand-habel@ iris.no

Tania Hildebrand-Habel is a senior research scientist at IRIS. She was awarded a Ph.D. in geology by the University of Bremen, Germany, and has experience from the Universities of Oslo and Stavanger, Norway. Her current research

AAPG Bulletin, v. 99, no. 5 (May 2015), pp. 791–805 791 new minerals and leaching the tested core by approximately 20%, respectively. Dramatic mineralogical and geochemical changes are observed with scanning electron microscopy– energy-dispersive x-ray spectroscopy, nano secondary ion mass spectrometry, x-ray diffraction, and whole-rock geochemistry techniques. The understanding of how fluids interact with rocks is important to, for example, EOR, because textural changes in the pore space affect how water will imbibe and expel oil from the rock. The mechanisms of dissolution and mineralization of fine-grained chalk can be described and quantified and, when understood, offer numerous possibilities in the engineering of carbonate reservoirs.

INTRODUCTION

The use of fluid injection for improved or enhanced oil recovery (EOR) is a commonly studied subject (e.g., Thomas et al., 1987;

Hermansen et al., 2000; Strand et al., 2007 and references cited therein), and results have been used in the production of hydrocarbons (Hermansen et al., 2000). Laboratory results from the last decades have demonstrated that lowering the salinity of the injection water increases the recovery from sandstones. This has led to studies to investigate the possibility of applying this mechanism on field scale and was followed by several field tests and now a full field injection of low salinity water flooding, the BP Clair

Ridge project, has been initiated (BP, 2014). In chalk, the concentration of divalent ions, and in particular magnesium, is an important factor. Several studies have been performed to find the composition of the optimal injection fluid for chalk (Strand et al., 2003; Austad and Standnes, 2003; Madland et al., 2006, 2008;

Zangiabadi et al., 2009). The cost of changing injection fluid versus the additional recovery must be addressed for each field specifically, and it is not the scope of this work. However, if the additional recovery is large enough, any type of fluid chemistry could be injected.