Showing papers on "Brine published in 2011"

Dissolution Trapping of Carbon Dioxide in Reservoir Formation Brine – A Carbon Storage Mechanism

Abstract: Carbon Capture and Storage (CCS) is a method to reduce anthropogenic greenhouse gas emissions thereby mitigating global warming. In CCS, carbon dioxide (CO2) is captured from fossil fuel-fired power plants or other large point-source emitters, purified, compressed and injected deep underground into subsurface formations at depths of or greater than 800m. At such depths CO2 is in a supercritical (sc) state increasing storage capacity (IPCC 2005). In CCS, there are four main mechanisms which keep the buoyant CO2 underground: 1. Structural/stratigraphic trapping – here an impermeable caprock prevents the CO2 from flowing upwards, 2. Capillary trapping, where micrometer-sized disconnected CO2 bubbles are formed and held in place by local capillary forces in the rock pore-network, 3. Dissolution trapping, where CO2 dissolves in the formation brine and sinks in the reservoir as the CO2-enriched brine has an increased density, 4. Mineral trapping, where the dissolved CO2 reacts with the formation brine, forms carbonic acid which dissociates generating protons, 3 HCO − and 3 CO − ions; these species subsequently react with the formation brine and/or host rock to form solid minerals which trap the CO2 very safely. The focus of this text is on dissolution trapping; how much CO2 dissolves under which geothermal conditions and what happens to the CO2-enriched brine, which is slightly denser than the original formation brine, in the formation. Important open questions in this context are: How fast are these mass transfer processes in real geological porous media under realistic CCS conditions? Are there means of accelerating CO2 dissolution? How do separate gas and/or oil phases (oil and/or gas reservoirs) in the reservoir affect CO2 dissolution processes and reservoir fluid dynamics? How does the pressure drop due to CO2 dissolution affect injectivity and storage capacity of CO2?

Separation of Produced Emulsions from Surfactant Enhanced Oil Recovery Processes

Abstract: Selected cationic and amphoteric surfactants were effective in separating oil-in-water emulsions representative of produced emulsions expected during a surfactant/polymer (SP) process for enhanced oil recovery. The aqueous phase of the emulsion contained an anionic surfactant blend, alcohol, and partially hydrolyzed polyacrylamide. Brine composition was a suitable mixture of formation brine with brines from the surfactant slug and polymer drive. The crude oil had an American Petroleum Institute (API) gravity of 31°. Bottle tests were conducted at ambient temperature, which is near the reservoir temperature. Conventional non-ionic demulsifier resins and polymeric cationic flocculants were not effective in removing oil from the aqueous phase. The water content of the oil phase was still well above specification upon heating the emulsions to 50−60 °C. However, both oil and water phases of acceptable quality were obtained after 6 h of settling upon the addition of 200 ppm of octyltrimethylammonium bromide (C8...

Chemical Alterations Induced by Rock–Fluid Interactions When Injecting Brines in High Porosity Chalks

Abstract: Effect of the aqueous chemistry on the mechanical strength of chalk has extensively been studied during the last decade. At high temperatures (~130°C), chalk exposed to seawater is significantly weaker compared to chalk exposed to distilled water when considering the hydrostatic yield strength and the following creep phase. The explanation of these experimental results must be of a chemical nature, as the density and viscosity of the aqueous phase vary little among these different brines. We present the results from simplified aqueous chemistry using MgCl2 brines, and compare these results with seawater. Previous studies show that different ions, e.g. Ca2+, Mg2+, $${{\rm SO}{_{4}}^{2-}}$$ in the injected brine, as well as the chalk mineralogy have an impact on the stability of the rock. We performed mechanical tests on chalk cores from Liege and Stevns Klint; it was found that these two outcrop chalks exhibit an unexpected difference in their mechanical responses when comparing cores flooded with NaCl and MgCl2 at 130°C. The results of this study show that the effects of magnesium seem to be governed not only by the differences in mineralogy, but also a time dependency on chalk deformation is additionally observed. Independent of the chalk type tested, the chemical analyses performed show that when MgCl2 is flooded through the core, a significant loss of magnesium and a considerable additional amount of calcium are detected in the effluent. The experimental observations fit very well with the time-dependent chemical changes gained from the mathematical model of this study that accounts for transport effects (convection and molecular diffusion) as well as chemical processes such as precipitation/dissolution. Based on the calculations and chemical analyses, we argue that the loss of magnesium and the production of calcium cannot solely be a consequence of a substitution process. The calculations rather indicate that magnesium is precipitated forming new mineral phases and in this process not only calcite, but also silicates are dissolved. The amount of dissolved calcium and silicon from the rock matrix is significant and could thus cause an additional deformation to take place. Both the retention of magnesium in the chalk core and the formation of newly precipitated magnesium-bearing carbonates and/or magnesium-bearing clay-like minerals after flooding with MgCl2 brine were demonstrated using scanning electron microscopic methods. In addition, precipitation of anhydrite as a result of flooding with seawater-like brine was proven. The water-induced strain not only depends on the ion composition of the injected brine; moreover, the presence of non-carbonate minerals will most likely also have a significant influence on the mechanical behaviour of chalk.

Effect of sodium chloride on corrosion of mild steel in CO2-saturated brines

Abstract: Corrosion rates of mild steel were measured in oxygen-free, CO2-saturated brines as a function of NaCl concentration employing electrochemical techniques. Decreased corrosion rates were observed as salt concentration increased. However, at high salt concentration (≥20 wt% NaCl), corrosion rates were independent of the flow rate of CO2-saturated brine. To understand this phenomenon, corrosion surfaces were analyzed by scanning electron microscopy and X-ray diffraction and showed only residual iron carbide for salt concentrations of 0.5–5 wt%. However, at 20 wt% NaCl, a porous corrosion scale with embedded crystals, possibly magnetite, was observed. No iron carbonate was observed and water chemistry showed it was 10,000 times below saturation. A numerical model of corrosion in CO2–NaCl systems was able to predict the reduced corrosion rates with salt concentration increase as a consequence of reduced solubility of CO2 (“salting-out”). However, the model did not predict that corrosion rates were flow-independent at high salt concentration. These results demonstrate that flow-independent corrosion is a consequence of a diffusion barrier created by magnetite scale, present only at high salt concentrations.

Role of partial miscibility on pressure buildup due to constant rate injection of CO2 into closed and open brine aquifers

Abstract: [1] This work extends an existing analytical solution for pressure buildup because of CO2 injection in brine aquifers by incorporating effects associated with partial miscibility. These include evaporation of water into the CO2 rich phase and dissolution of CO2 into brine and salt precipitation. The resulting equations are closed-form, including the locations of the associated leading and trailing shock fronts. Derivation of the analytical solution involves making a number of simplifying assumptions including: vertical pressure equilibrium, negligible capillary pressure, and constant fluid properties. The analytical solution is compared to results from TOUGH2 and found to accurately approximate the extent of the dry-out zone around the well, the resulting permeability enhancement due to residual brine evaporation, the volumetric saturation of precipitated salt, and the vertically averaged pressure distribution in both space and time for the four scenarios studied. While brine evaporation is found to have a considerable effect on pressure, the effect of CO2 dissolution is found to be small. The resulting equations remain simple to evaluate in spreadsheet software and represent a significant improvement on current methods for estimating pressure-limited CO2 storage capacity.

Brine fluxes from growing sea ice

Abstract: It is well known that brine drainage from growing sea ice has a controlling influence on its mechanical, electromagnetic, biological and transport properties, and hence upon the buoyancy forcing and ecology in the polar oceans. When the ice has exceeded a critical thickness the drainage process is dominated by brine channels: liquid conduits extending through the ice. We describe a theoretical model for the drainage process using mushy layer theory which demonstrates that the brine channel spacing is governed by a selection mechanism that maximizes the rate of removal of stored potential energy, and hence the brine flux from the system. The fluid transport through the sea ice and hence the scaling laws for brine fluxes and brine channel spacings are predicted. Importantly, the resulting brine flux scaling is consistent with experimental data for growth from a fixed temperature surface, allowing all parameters in the scaling law to be determined. This provides an experimentally tested first principles derivation of a parameterization for brine fluxes from growing sea ice.

Synthesis of hydroxy sodalite from coal fly ash using waste industrial brine solution.

Abstract: The effect of using industrial waste brine solution instead of ultra pure water was investigated during the synthesis of zeolites using three South African coal fly ashes as Si feedstock. The high halide brine was obtained from the retentate effluent of a reverse osmosis mine water treatment plant. Synthesis conditions applied were; ageing of fly ash was at 47 ° C for 48 hours, and while the hydrothermal treatment temperature was set at 140 ° C for 48 hours. The use of brine as a solvent resulted in the formation of hydroxy sodalite zeolite although unconverted mullite and hematite from the fly ash feedstock was also found in the synthesis product.

Viscosity and yield stresses of ice slurries formed in water-in-oil emulsions

Abstract: Molecular inclusion compounds called clathrate hydrates are a common concern in oil and gas pipelines, as they cause disruption to production. These crystalline compounds are over 80 mol% water and are often only stable at high pressures and low temperatures. As a means to understand the rheology of clathrate hydrates, we investigated ice slurries, in crude oil, as a simple analogy to clathrate hydrates. A series of water-in-oil emulsions were prepared at different volume fractions of water, ranging from 0.10 to 0.70. Water used in the samples was deionized watger or a 3.5 wt% NaCl brine solution. The emulsions were cooled to - 10 ° C and the viscosity and yield stress were analyzed as a function of time after nucleation. No yield stresses were observed at volume fractions below 0.2 for fresh water and 0.3 for brine solution. In the fresh water system, the yield stress varied with increasing volume fraction. Between volume fractions of 0.25–0.55, yield stresses were on the order of 300 Pa, and at larger volumer fractions (0.6–0.7) yield stress quickly increased to an unmeasurable value (greater than 3000 Pa, the instrument’s limit). In the brine system, yield stress increased with volume fraction of water. After formation of ice, flow was stopped and the system was “annealed”. During the “annealing” period, the magnitude of complex viscosity of the fresh water system reached a peak value after two hours, decreased for approximately four hours, and then changed little for the next forty hours. The yield stress during “annealing” mimicked the trend of the magnitude of complex viscosity. In the brine system, the magnitude of complex viscosity increased over the first three hours, then changed little. However, the yield stress decreased as the “annealing” time increased. Following the measurements of yield stress, the slurry was conditioned at 500 s - 1 and the apparent viscosity was analyzed as a function of shear rate. At volume fractions greater than 0.10 the slurry was found to be shear thinning and exhibited a viscosity increase compared to the initial emulsion.

Modeling interfacial liquid layers on environmental ices

Abstract: . Interfacial layers on ice significantly influence air-ice chemical interactions. In solute-containing aqueous systems, a liquid brine may form upon freezing due to the exclusion of impurities from the ice crystal lattice coupled with freezing point depression in the concentrated brine. The brine may be segregated to the air-ice interface where it creates a surface layer, in micropockets, or at grain boundaries or triple junctions. We present a model for brines and their associated liquid layers in environmental ice systems that is valid over a wide range of temperatures and solute concentrations. The model is derived from fundamental equlibrium thermodynamics and takes into account nonideal solution behavior in the brine, partitioning of the solute into the ice matrix, and equilibration between the brine and the gas phase for volatile solutes. We find that these phenomena are important to consider when modeling brines in environmental ices, especially at low temperatures. We demonstrate its application for environmentally important volatile and nonvolatile solutes including NaCl, HCl, and HNO 3 . The model is compared to existing models and experimental data from literature where available. We also identify environmentally relevant regimes where brine is not predicted to exist, but the QLL may significantly impact air-ice chemical interactions. This model can be used to improve the representation of air-ice chemical interactions in polar atmospheric chemistry models.

Parameters affecting mineral trapping of CO2 sequestration in brines

Abstract: Carbon dioxide sequestration using brines has emerged as a promising technology to mitigate the adverse impacts of climate change due to its large storage capacity and favorable chemistries. However, the permanent storage of CO2 in brines takes significantly long periods of time as the formation of carbonates is very slow. This review focuses on the four main parameters (brine composition, brine pH, system temperature, and pressure) that have been reported to have a major effect on mineral trapping of CO2 sequestration in brines. These parameters are difficult to control for in situ underground CO2 sequestration. However, understanding the effects of these main parameters is useful for both aboveground and underground carbonation reactions. Brine pH is the most important parameter. The precipitation of carbonate minerals is favored over a basic pH of 9.0. In order to promote the formation of carbonates, brine pH could be enhanced by using additives. System temperature has a greater effect than pressure. © 2011 Society of Chemical Industry and John Wiley & Sons, Ltd

Treatment of gas well production wastewaters

Abstract: A method of treating a wastewater is provided and can be used, for example, to treat a gas well production wastewater to form a wastewater brine. The method can involve crystallizing sodium chloride by evaporation of the wastewater brine with concurrent production of a liquor comprising calcium chloride solution. Bromine and lithium can also be recovered from the liquor in accordance with the teachings of the present invention. Various metal sulfates, such as barium sulfate and strontium sulfate, can be removed from the wastewater in the production of the wastewater brine. Sources of wastewater can include gas well production wastewater and hydrofracture flowback wastewater.