EOR by Smart Water Flooding in Sandstone Reservoirs - Effect of Sandstone Mineralogy on Initial Wetting and Oil Recovery

Mamonov, Aleksandr; Puntervold, Tina; Strand, Skule

doi:10.2118/187839-ms

Cited by 14 publications

(10 citation statements)

References 23 publications

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“…The rise in pH indicates that the outcrop cores may have reached alkaline conditions. When the pH increases to alkalinity, the adsorption of organic molecules by feldspar and other clay minerals is reduced (Mamonov et al, 2017). However, increasing flooding temperatures, particularly above 100 °C, were observed as the cause of reduced pH during water flooding in the current study.…”

Section: Ph Determinationcontrasting

confidence: 51%

Effect of temperature on the pH of water flood effluents and irreducible water saturation: A study with reference to the Barail sandstone outcrop of the upper Assam Basin

Neog

2021

J Petrol Explor Prod Technol

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Low salinity water flooding (LSWF) is a promising strategy for improving oil recovery in sandstone reservoirs, and recent studies have shown that the recovery with low salinity water injection is a function of not only the salinity and ionic composition but also of the pH of injected brine, temperature, and the combined effect of both on the wetting properties of the clay mineral surfaces. Following brine flooding, the initial wettability of sandstone rock surfaces existed when crude oil, formation water (FW), and rock surface interaction were in chemical equilibrium at reservoir condition changes based on brine pH, salinity, temperature, and clay mineralogy. This study proposes pH, core flood temperature, and irreducible water saturation as key parameters in inducing wettability changes in the sandstone porous media. In the present work, the sandstone cores were subjected to flooding at temperatures of 70 °C, 85 °C, and 105 °C and measured the pH of the discharge effluents and initial or irreducible water saturation with respect to varying temperatures. This paper investigates the rise of the pH gradient and irreducible water saturation, Swir with respect to LS flooding, at increasing temperatures using a Barail sandstone core. The key results include the following: The pH of the flood effluents increases with increasing core flood temperature, which indicates a shifting of the existing wetting state of the rock. The combined effects of increasing pH and initial or irreducible water saturation pertaining to low salinity flooding at progressively increasing temperatures result in increasing water wettability of the sandstone rock. Increasing flooding temperatures cause an increase in Swir, which follows a linear relationship. The findings of the paper highlight the link of increasing pH and irreducible water saturation with the water wetting properties of the sandstone reservoir rock and hence the fluid flow or the oil–water relative permeability behaviour. This paper proposes that increased irreducible water saturation and pH of water flood effluents are connected to increasing water wetness in a sandstone rock as a function of elevated temperatures. As adequate work and consensus on the potential effects of temperature on wettability alteration under low salinity water flooding is still lacking, the current work in relation to the Barail sandstone of the upper Assam basin could be a novel reference for understanding of the importance of temperature dependent wettability alteration behaviour in sandstone cores. The findings of this study can assist in the formation of a novel approach towards considering the increasing irreducible water saturation and pH of the brine effluent as an effect of alternatively injection of low salinity water at elevated temperatures on sandstone porous rock.

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Section: Ph Determinationcontrasting

confidence: 51%

Effect of temperature on the pH of water flood effluents and irreducible water saturation: A study with reference to the Barail sandstone outcrop of the upper Assam Basin

Neog

2021

J Petrol Explor Prod Technol

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“…Previously published adsorption studies by Reed showed that nitrogenous bases were retained on clay-containing reservoir sandstones after crude oil flooding. Other studies have confirmed the high affinity of the basic crude oil components for adsorption on silicate minerals using quinoline (C 9 H 7 N) as a model basic component in static adsorption experiments. ,− The main observation from the static tests is that the adsorption processes are largely dependent on the pH of the surrounding water phase. Acidic pH conditions promote the adsorption of protonated quinoline molecules (C 9 H 7 NH + ) onto negatively charged silicate minerals with maximum adsorption at pH ≈ p K a ≈ 5.…”

Section: Introductionmentioning

confidence: 95%

Adsorption of Polar Organic Components onto Sandstone Rock Minerals and Its Effect on Wettability and Enhanced Oil Recovery Potential by Smart Water

et al. 2019

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It is generally accepted that reservoir wettability is one of the most important parameters in oil recovery processes. In the published literature, it is believed that the state of reservoir wettability mainly depends on the adsorption or precipitation of oxygen and nitrogen compounds present in the heavy-end fractions of crude oil. However, the establishment of reservoir wetting is a more complex process that involves chemical interactions between all phases of the reservoir: rock mineral surfaces, formation water, and surface-active components in the crude oil. In this study, dynamic adsorption tests were performed by flooding modified crude oils with a low asphaltene content through outcrop sandstone cores. Adsorption of crude oil components was analyzed by comparing base number (BN) and acid number (AN) of the effluent oil samples with the known initial BN and AN of the crude oil. The experimental results showed that crude oil bases are more active than acids toward the silicate rock mineral surfaces. Within the pore volumes flooded, it was not possible to achieve equilibrium BN values because of the continuous adsorption of basic components. Spontaneous imbibition (SI) tests showed that the core sample behaved slightly water-wet after crude oil flooding. Ion-modified smart water as an imbibition fluid in tertiary mode has previously shown potential for wettability alteration and improved oil recovery. With an increase in the amount of injected crude oil through the core, a decrease in oil recovery and a decrease in smart water-enhanced oil recovery (EOR) potential were observed. SI oil recovery results indicate reduced positive capillary forces and a change in wetting toward a less water-wet state. Thus, the chemical composition of crude oil should be considered as an important parameter for a reliable estimation of the reservoir wettability state and EOR potential by smart water injection.

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“…29,30 Sandstone formations mainly consist of silica, feldspar, clay minerals (usually illite, kaolinite, montmorillonite, and chlorite), carbonates as cementing materials, and iron oxides. 28,31 Silica (SiO 2 ) minerals are not the preferential adsorption sites for the anionic surfactants because of two main reasons: they are negatively charged for pH values above 3 and have a low surface area. Conversely, finely dispersed clay minerals have a much larger surface area and can be positively charged on the edges, which make them potential adsorption sites for the anionic surfactants.…”

Section: ■ Introductionmentioning

confidence: 99%

Role of Wettability on the Adsorption of an Anionic Surfactant on Sandstone Cores

et al. 2020

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We investigate the dynamic adsorption of anionic surfactant C 14 − 16 alpha olefin sulfonate on Berea sandstone cores with different surface wettability and redox states under high temperature that represents reservoir conditions. Surfactant adsorption levels are determined by analyzing the effluent history data with a dynamic adsorption model assuming Langmuir isotherm. A variety of analyses, including surface chemistry, ionic composition, and chromatography, is performed. It is found that the surfactant breakthrough in the neutral-wet core is delayed more compared to that in the water-wet core because the deposited crude oil components on the rock surface increase the surfactant adsorption via hydrophobic interactions. As the surfactant adsorption is satisfied, the crude oil components are solubilized by surfactant micelles and some of the adsorbed surfactants are released from the rock surface. The released surfactant dissolves in the flowing surfactant solution, thereby resulting in an overshoot of the produced surfactant concentration with respect to the injection value. Furthermore, under water-wet conditions, changing the surface redox potential from an oxidized to a reduced state decreases the surfactant adsorption level by 40%. We find that the decrease in surfactant adsorption is caused not only by removing the iron oxide but also by changing the calcium concentration after the core restoration process (calcite dissolution and ion exchange as a result of using EDTA). Findings from this study suggest that laboratory surfactant adsorption tests need to be conducted by considering the wettability and redox state of the rock surface while recognizing how core restoration methods could significantly alter the ionic composition during surfactant flooding.

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EOR by Smart Water Flooding in Sandstone Reservoirs - Effect of Sandstone Mineralogy on Initial Wetting and Oil Recovery

Cited by 14 publications

References 23 publications

Effect of temperature on the pH of water flood effluents and irreducible water saturation: A study with reference to the Barail sandstone outcrop of the upper Assam Basin

Effect of temperature on the pH of water flood effluents and irreducible water saturation: A study with reference to the Barail sandstone outcrop of the upper Assam Basin

Adsorption of Polar Organic Components onto Sandstone Rock Minerals and Its Effect on Wettability and Enhanced Oil Recovery Potential by Smart Water

Role of Wettability on the Adsorption of an Anionic Surfactant on Sandstone Cores

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