Comparative Studies of Mineralogical Alterations of Three Ultra-long-term Tests of Onshore Chalk at Reservoir Conditions

Minde, Mona Wetrhus; Haser, S.; Korsnes, Reidar Inge; Zimmermann, Udo; Madland, Merete Vadla

doi:10.3997/2214-4609.201700308

Cited by 6 publications

(20 citation statements)

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“…Various high-resolution methods were used to study mineralogical alteration in flooded chalk: field emission gun scanning electron microscopy, energy-dispersive X-ray spectroscopy (FEG-SEM-EDS) [3,5,8,14,36,37,53], nano secondary ion mass spectrometry (NanoSIMS) [36,47,54], X-ray diffraction (XRD) [36], whole-rock geochemistry techniques [21,36]. Tip-Enhanced Raman Spectroscopy-Atomic Force Microscopy (TERS-AFM) [55,56], Transmission Electron Microscopy (TEM) [53,57], and Mineral Liberation Analysis (MLA) [53]. The authors (Zimmermann et al, 2015 for the LTT, and Nermoen et al, 2015 for the ULTT) determined a loss of Ca 2+ and a gain in Mg 2+ , demonstrating a precipitation of new Mg-minerals in the core.…”

Section: Earlier Studies and Characterisation Of The Sample Materialsmentioning

confidence: 99%

“…The authors (Zimmermann et al, 2015 for the LTT, and Nermoen et al, 2015 for the ULTT) determined a loss of Ca 2+ and a gain in Mg 2+ , demonstrating a precipitation of new Mg-minerals in the core. FEG-SEM and TEM images have shown magnesite crystals with a grain size between 100 nm and 1 μm [53,57].…”

Section: Earlier Studies and Characterisation Of The Sample Materialsmentioning

confidence: 99%

“…NanoSIMS 50 was the only analytical method that could detect positively with an image proof magnesite and very tiny new grown quartz of micron-and sub-micron sizes [36]. When analyzed by MLA, the shorter of the two tests, LTT, displayed a rather sharp (~1.5 mm) transition between two areas with different mineralogy [53]. Closest to the inlet of the core, the rock material is completely altered into magnesite with minor contents of calcium along with clay minerals.…”

Section: Earlier Studies and Characterisation Of The Sample Materialsmentioning

confidence: 99%

“…The composition of the two cores after flooding has been affected by the nature of the fluid flow paths. This is often only visible at microscale, has a specific geometric form, and is composed of several compositional trends [53], and therefore awaits a detailed study and is not of relevance here. Hence, a quick and thorough investigation of the mineralogical composition prior to detailed FEG-SEM-EDS studies or further meticulous electron-and ion-beam-based analyses would be helpful.…”

Section: Feg-sem-edsmentioning

confidence: 99%

“…The grains are no longer rounded, but show a rhombic crystal shape, with grain-size mostly below 1 µm. In the completely altered areas, coccoliths and other micro/nano-fossils are no longer observed, while in parts where the calcite is still present, clear signs of dissolution is visible [36,53]. Additionally, significant amounts of clay-minerals are present, with main constituents being Mg and Si, which could be interpreted to be talc.…”

Section: Feg-sem-edsmentioning

confidence: 99%

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Quick, Easy, and Economic Mineralogical Studies of Flooded Chalk for EOR Experiments Using Raman Spectroscopy

et al. 2018

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Understanding the chalk-fluid interactions and the associated mineralogical and mechanical alterations on a sub-micron scale are major goals in Enhanced Oil Recovery. Mechanical strength, porosity, and permeability of chalk are linked to mineral dissolution that occurs during brine injections, and affect the reservoir potential. This paper presents a novel "single grain" methodology to recognize the varieties of carbonates in rocks and loose sediments: Raman spectroscopy is a non-destructive, quick, and user-friendly technique representing a powerful tool to identify minerals down to 1 µm. An innovative working technique for oil exploration is proposed, as the mineralogy of micron-sized crystals grown in two flooded chalk samples (Liége, Belgium) was successfully investigated by Raman spectroscopy. The drilled chalk cores were flooded with MgCl 2 for ca. 1.5 (Long Term Test) and 3 years (Ultra Long Term Test) under North Sea reservoir conditions (Long Term Test: 130 • C, 1 PV/day, 9.3 MPa effective stress; Ultra Long Term Test: 130 • C, varying between 1-3 PV/day, 10.4 MPa effective stress). Raman spectroscopy was able to identify the presence of recrystallized magnesite along the core of the Long Term Test up to 4 cm from the injection surface, down to the crystal size of 1-2 µm. In the Ultra Long Term Test core, the growth of MgCO 3 affected nearly the entire core (7 cm). In both samples, no dolomite or high-magnesium calcite secondary growth could be detected when analysing 557 and 90 Raman spectra on the Long and Ultra Long Term Test, respectively. This study can offer Raman spectroscopy as a breakthrough tool in petroleum exploration of unconventional reservoirs, due to its quickness, spatial resolution, and non-destructive acquisition of data. These characteristics would encourage its use coupled with electron microscopes and energy dispersive systems or even electron microprobe studies.

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Section: Earlier Studies and Characterisation Of The Sample Materialsmentioning

confidence: 99%

Section: Earlier Studies and Characterisation Of The Sample Materialsmentioning

confidence: 99%

Section: Earlier Studies and Characterisation Of The Sample Materialsmentioning

confidence: 99%

Section: Feg-sem-edsmentioning

confidence: 99%

Section: Feg-sem-edsmentioning

confidence: 99%

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Quick, Easy, and Economic Mineralogical Studies of Flooded Chalk for EOR Experiments Using Raman Spectroscopy

et al. 2018

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Impact of Initial Wettability and Injection Brine Chemistry on Mechanical Behaviour of Kansas Chalk

et al. 2019

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Effect of Initial Wettability on Rock Mechanics and Oil Recovery: Comparative Study on Outcrop Chalks

et al. 2020

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Brines containing surface-active divalent ions such as Ca 2+ , Mg 2+ and SO 4 2− impact the stiffness, strength and time-dependent deformation of water wet Mons outcrop chalk. This study documents how stiffness and strength of wettability-altered oil and water-saturated (mixed wet) Mons chalk compare to water-saturated and water wet samples during hydrostatic loading and creep. During hydrostatic creep, the strain rate response to magnesium chloride (MgCl 2 ) brine injection is compared for water wet and mixed wet samples. For the mixed wet samples, the oil production was estimated during compaction and non-equilibrium MgCl 2 flow. The results presented here were then compared to a similar test series on Kansas outcrop chalk. The differences were interpreted in terms of difference in physical parameters such as porosity and pore size. Two Mons samples were wettability-altered and tested in parallel to two completely water wet samples from the same chalk block at hydrostatic conditions and 130 °C. It was found that beyond the experimental uncertainty, the stiffness and yield strength measurements showed insignificant differences for water wet and mixed wet Mons samples. This is contrary to Kansas chalk where mixed wet samples were systematically stronger and stiffer than water wet samples. In the following creep phase, both water wet and wettability-altered Mons chalk samples gave trends comparable to each other during a stagnant phase and a following MgCl 2 injection phase at varying flow rates. Similar observations were reported for water wet and wettability-altered Kansas chalks as well. Further, the same chemical reactions were observed for Kansas and Mons chalks and were found to be insensitive to the initial wettability and oil/water saturations. The oil production observations from Mons chalk showed that 43% of the total oil was recovered during early-stage compaction with no flow, whereas Kansas chalk did not produce any oil at no-flow conditions. After the oil recovery from the first 2-3 pore volumes of brine flow, no further oil production was observed due to compaction or non-equilibrium brine flow in any of the two chalk types.

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Comparative Studies of Mineralogical Alterations of Three Ultra-long-term Tests of Onshore Chalk at Reservoir Conditions

Cited by 6 publications

References 0 publications

Quick, Easy, and Economic Mineralogical Studies of Flooded Chalk for EOR Experiments Using Raman Spectroscopy

Quick, Easy, and Economic Mineralogical Studies of Flooded Chalk for EOR Experiments Using Raman Spectroscopy

Impact of Initial Wettability and Injection Brine Chemistry on Mechanical Behaviour of Kansas Chalk

Effect of Initial Wettability on Rock Mechanics and Oil Recovery: Comparative Study on Outcrop Chalks

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