Gravimetric Monitoring Research Articles

Gravimetric Monitoring of Confined and Unconfined Geological CO2 Reservoirs

The surface gravity effect of the injected CO2 into geological reservoirs has always been assumed to be a negative signal, and to be dependent on the injected CO2 mass and the reservoir depth. Nonetheless, certain geological CO2 reservoirs with specific characteristics experience porosity changes and exhibit large ground surface deformation. The gravimetric effect as a result of mass balance changes in such reservoirs is modeled as a positive signal. Our investigations on the geomechanical properties of the two different types of reservoirs demonstrate the indirect dependency of gravity signal on a few other characteristics, like reservoir size, porosity, and permeability.

20 Years of Monitoring CO2-injection at Sleipner

The Sleipner CO2 injection project was the world's first industrial offshore CO2 Capture and Storage (CCS) project with more than 16 Mt CO2 injected since 1996. Key monitoring insights from Sleipner are the dual interpretation of seismic and gravimetric monitoring surveys to quantify the free CO2 mass changes and plume geometry development as a function of time. The learnings from Sleipner have contributed to making guidelines for monitoring future CCS injection projects, showing that selection of monitoring technology and the timing and extent of monitoring surveys should be case specific and risk based, while also taking into account the long term nature of CCS projects.

Atomic layer deposition on porous powders with in situ gravimetric monitoring in a modular fixed bed reactor setup.

A modular setup for Atomic Layer Deposition (ALD) on high-surface powder substrates in fixed bed reactors with a gravimetric in situ monitoring was developed. The design and operation are described in detail. An integrated magnetically suspended balance records mass changes during ALD. The highly versatile setup consists of three modular main units: a dosing unit, a reactor unit, and a downstream unit. The reactor unit includes the balance, a large fixed bed reactor, and a quartz crystal microbalance. The dosing unit is equipped with a complex manifold to deliver gases and gaseous reagents including three different ALD precursors, five oxidizing or reducing agents, and two purge gas lines. The system employs reactor temperatures and pressures in the range of 25-600 °C and 10-3 to 1 bar, respectively. Typically, powder batches between 100 mg and 50 g can be coated. The capabilities of the setup are demonstrated by coating mesoporous SiO2 powder with a thin AlOx (submono) layer using three cycles with trimethylaluminium and H2O. The self-limiting nature of the deposition has been verified with the in situ gravimetric monitoring and full saturation curves are presented. The process parameters were used for a scale-up in a large fixed bed reactor. The samples were analyzed with established analytics such as X-ray diffraction, N2 adsorption, transmission electron microscopy, and inductively coupled plasma optical emission spectrometry.

Patterns of domestic exposure to carbon monoxide and particulate matter in households using biomass fuel in Janakpur, Nepal

Household Air Pollution (HAP) from biomass cooking fuels is a major cause of morbidity and mortality in low-income settings worldwide. In Nepal the use of open stoves with solid biomass fuels is the primary method of domestic cooking. To assess patterns of domestic air pollution we performed continuous measurement of carbon monoxide (CO) and particulate Matter (PM2.5) in 12 biomass fuel households in Janakpur, Nepal. We measured kitchen PM2.5 and CO concentrations at one-minute intervals for an approximately 48-h period using the TSI DustTrak II 8530/SidePak AM510 (TSI Inc, St. Paul MN, USA) or EL-USB-CO data logger (Lascar Electronics, Erie PA, USA) respectively. We also obtained information regarding fuel, stove and kitchen characteristics and cooking activity patterns. Household cooking was performed in two daily sessions (median total duration 4 h) with diurnal variability in pollutant concentrations reflecting morning and evening cooking sessions and peak concentrations associated with fire-lighting. We observed a strong linear relationship between PM2.5 measurements obtained by co-located photometric and gravimetric monitoring devices, providing local calibration factors of 4.9 (DustTrak) and 2.7 (SidePak). Overall 48-h average CO and PM2.5 concentrations were 5.4 (SD 4.3) ppm (12 households) and 417.6 (SD 686.4) μg/m3 (8 households), respectively, with higher average concentrations associated with cooking and heating activities. Overall average PM2.5 concentrations and peak 1-h CO concentrations exceeded WHO Indoor Air Quality Guidelines. Average hourly PM2.5 and CO concentrations were moderately correlated (r = 0.52), suggesting that CO has limited utility as a proxy measure for PM2.5 exposure assessment in this setting. Domestic indoor air quality levels associated with biomass fuel combustion in this region exceed WHO Indoor Air Quality standards and are in the hazardous range for human health.

Bayesian inversion of gravimetric data and assessment of CO2 dissolution in the Utsira Formation

Offshore gravimetric monitoring has been introduced as a complement to seismic monitoring of fields with moving fluids. The Sleipner field in the North Sea is a fully operational carbon capture and storage facility, where [Formula: see text] is injected for storage. Gravimetric measurements are one of the geophysical monitoring methods applied, and the data have been used to estimate the in situ density and dissolution of the [Formula: see text]. We defined a Bayesian inversion of gravimetric data, and we used this to analyze gravimetric data at Sleipner field. In our approach, we included spatial uncertainty in the model and performed a Bayesian analysis of the in situ [Formula: see text] density and dissolution. We also analyzed the impact of mass changes due to gas production from the Ty Formation. Our estimates were comparable with published results.

Gravimetric monitoring of the first field‐wide steam injection in a fractured carbonate field in Oman – a feasibility study

ABSTRACTGas‐Oil Gravity Drainage is to be enhanced by steam injection in a highly fractured, low permeability carbonate field in Oman. Following a successful pilot, field‐wide steam injection is being implemented, first of this type in the world. A dedicated monitoring program has been designed to track changes in the reservoir. Various observations are to be acquired, including, surface deformation, temperature measurements, microseismic, well logs, pressure and saturation measurements to monitor the reservoir. Because significant changes in the reservoir density are expected, time‐lapse gravimetry is also being considered. In this paper we investigate the feasibility of gravimetric monitoring of the thermally enhanced gravity drainage process at the carbonate field in Oman. For this purpose, forward gravity modelling is performed. Based on field groundwater measurements, the estimates of the hydrological signal are considered and it is investigated under what conditions the groundwater influences can be minimized. Using regularized inversion of synthetic gravity data, we analyse the achievable accuracy of heat‐front position estimates. In case of large groundwater variations at the field, the gravity observations can be significantly affected and, consequently, the accuracy of heat‐front monitoring can be deteriorated. We show that, by applying gravity corrections based on local observations of groundwater, the hydrological influences can to a large extent be reduced and the accuracy of estimates can be improved. We conclude that gravimetric monitoring of the heat‐front evolution has a great potential.

Study of the carbonaceous aerosol and morphological analysis of fine particles along with their mixing state in Delhi, India: a case study.

Because of high emissions of anthropogenic as well as natural particles over the Indo-Gangetic Plains (IGP), it is important to study the characteristics of fine (PM2.5) and inhalable particles (PM10), including their morphology, physical and chemical characteristics, etc., in Delhi during winter 2013. The mean mass concentrations of fine (PM2.5) and inhalable (PM10) (continuous) was 117.6 ± 79.1 and 191.0 ± 127.6 μg m(-3), respectively, whereas the coarse mode (PM10-2.5) particle PM mass was 73.38 ± 28.5 μg m(-3). During the same period, offline gravimetric monitoring of PM2.5 was conducted for morphological analysis, and its concentration was ~37 % higher compared to the continuous measurement. Carbonaceous PM such as organic carbon (OC) and elemental carbon (EC) were analyzed on the collected filters, and their mean concentration was respectively 33.8 and 4.0 μg m(-3) during the daytime, while at night it was 41.2 and 10.1 μg m(-3), respectively. The average OC/EC ratio was 8.97 and 3.96 during the day and night, respectively, indicating the formation of secondary organic aerosols during daytime. Effective carbon ratio was studied to see the effect of aerosols on climate, and its mean value was 0.52 and 1.79 during night and day, indicating the dominance of absorbing and scattering types of aerosols respectively into the atmosphere over the study region. Elemental analysis of individual particles indicates that Si is the most abundant element (~37-90 %), followed by O (oxide) and Al. Circularity and aspect ratio was studied, which indicates that particles are not perfectly spherical and not elongated in any direction. Trajectory analysis indicated that in the months of February and March, air masses appear to be transported from the Middle Eastern part along with neighboring countries and over Thar Desert region, while in January it was from the northeast direction which resulted in high concentrations of fine particles.

Mass balance monitoring of geological CO2 storage with a superconducting gravimeter — A case study

Although monitoring of geological carbon dioxide (CO2) storage is possible with a number of geophysical and geodetic techniques (e.g., seismic survey), gravimetric monitoring is known to be the most accurate method for measuring total mass changes. Therefore, it can be used for detection of storage pore space content changes and migration of CO2 plumes. A superconducting gravimeter (SG) installed on the Earth's surface provides precise and continuous records of gravity variations over time for periods from minutes to decades, which are required for monitoring subsurface CO2 storage. Due to the fact that gravimeter records combine the gravity effects of surface displacement and subsurface mass change, these two effects must be separated properly for observing CO2 mass balance. The Newtonian attraction gravity effect of stored CO2 is modeled as a function of reservoir depth and CO2 mass for different locations of the gravimeter over the reservoir. The gravity effect of the surface deformation is considered according to the modeled and measured displacement above the CO2 reservoir at the gravimeter's position. For estimation of the detection threshold, an assessment is carried out for the gravity corrections, which must be subtracted from the raw gravity data before obtaining the gravity signal of the stored CO2. A CO2 signal larger than about 0.5μGal can be detected with an SG's continuous recordings. A measured gravity profile along the reservoir can support the continuous measurements. For providing objective evidence of a CO2 stored gravity signal, real measured raw SG gravity data of the MunGyung site in Korea were superimposed with an artificial uniformly continuous gravity signal up to 1.7μGal, representing a gravity signal from a CO2 storage site with increasing injections up to about 105kt at a depth of 600m. These data were analyzed, and the CO2 storage signal could be clearly identified.

A new self-assembled layer-by-layer glucose biosensor based on chitosan biopolymer entrapped enzyme with nitrogen doped graphene

The layer-by-layer (LbL) technique has been used for the construction of a new enzyme biosensor. Multilayer films containing glucose oxidase, GOx, and nitrogen-doped graphene (NG) dispersed in the biocompatible positively-charged polymer chitosan (chit+(NG+GOx)), together with the negatively charged polymer poly(styrene sulfonate), PSS−, were assembled by alternately immersing a gold electrode substrate in chit+(NG+GOx) and PSS− solutions. Gravimetric monitoring during LbL assembly by an electrochemical quartz microbalance enabled investigation of the adsorption mechanism and deposited mass for each monolayer. Cyclic voltammetry and electrochemical impedance spectroscopy were used to characterize the LbL modified electrodes, in order to establish the contribution of each monolayer to the overall electrochemical properties of the biosensor. The importance of NG in the biosensor architecture was evaluated by undertaking a comparative study without NG in the chit layer. The GOx biosensor's analytical properties were evaluated by fixed potential chronoamperometry and compared with similar reported biosensors. The biosensor operates at a low potential of −0.2V vs., Ag/AgCl, exhibiting a high sensitivity of 10.5μAcm−2mM−1, and a detection limit of 64μM. This study shows a simple approach in developing new biosensor architectures, combining the advantages of nitrogen-doped graphene with the LbL technique for enzyme immobilization.

The Sleipner storage site: Capillary flow modeling of a layered CO2 plume requires fractured shale barriers within the Utsira Formation

To prevent ocean acidification and mitigate greenhouse gas emissions, it is necessary to capture and store carbon dioxide. The Sleipner storage site, offshore Norway, is the world's first and largest engineered waste repository for a greenhouse gas. CO2 is separated from the Sleipner gas condensate field and stored in the pore space of the Utsira Formation, a saline aquifer approximately 1km below the surface and 200km from the coast. Statoil, the field operator, has injected almost 1Mt/yr of captured CO2 into the storage site since 1996. The buoyant CO2 plume ascended rapidly through eight thin shale barriers within the aquifer to reach the top seal in less than three years. The plume's progress has been monitored by eight seismic surveys, as well as gravimetric and electromagnetic monitoring, which record the spreading of nine thin CO2 layers. This paper presents a capillary flow model using invasion percolation physics that accurately matches the plume's geometry. The approach differs from standard Darcy flow simulations, which fail to match the plume geometry. The calibrated capillary flow simulation indicates that a mass balance for the plume is likely, but can only replicate the plume geometry if the thin intra-formational shale barriers are fractured. The model enables an estimate of the shale barrier behavior and caprock performance. The fractures are very unlikely to have been caused by CO2 injection given the confining stress of the rock and weak overpressure of the plume, and so fracturing must pre-date injection. A novel mechanism is suggested: the deglaciation of regional ice sheets that have rapidly and repeatedly unloaded approximately 1km of ice. The induced transient pore pressures are sufficient to hydro-fracture thin shales. The fractures enable fast CO2 ascent, resulting in a multi-layered plume. Shallow CO2 storage sites in the Northern North Sea and other regions that have been loaded by Quaternary ice sheets are likely to behave in a similar manner.

Evaporation triggered self-assembly in aqueous fragrance–ethanol mixtures and its impact on fragrance performance

The present study demonstrates how the evaporation of a ternary ethanol–water–fragrance solution leads to a transition from an unstructured ternary ethanol-rich solution, to a structured water-rich solution by crossing the so-called pre-ouzo region of its phase diagram. The exothermal nature of this self-assembly revealed by calorimetry suggests that it is coupled to molecular transfer between coexisting micro-domains.Surprisingly, fragrance evaporation is first accelerated in the pre-ouzo region as evidenced unambiguously by simultaneous on-line gravimetric, calorimetric and gas chromatographic monitoring during drying. Upon further drying, a transition from the pre-ouzo to the two-phase turbid region of the phase diagram is observed as the loss of water becomes more important that of ethanol. At this stage, the size of the fragrance-rich domain increases by three orders of magnitude as fragrance droplets surrounded by ethanol molecules are entrapped in water-rich external media and the fragrance evaporation is depressed.This initial acceleration and subsequent retardation of the evaporation kinetics of fragrance molecules are general for all perfumery ingredients. The path of the compositional change in the phase diagram during evaporation is investigated under strong inert gas flux for the first time to our knowledge by two combining on-line methods.

Monitoring Current Vertical Movements of the Northern Caucasus by Absolute and Relative Gravimetry

Measurements of the absolute acceleration of gravity g at seven sites in the Northern Caucasus region which form a reference network for gravimetric monitoring of vertical movements of the region are reported. A method based on measuring Δg between new and the reference sites with a high-precision relative gravimeter has been developed for extending this network to other parts of the region.

In Situ Electrochemical Quartz Crystal Admittance Methodology for Tracking Compositional and Mechanical Changes in Porous Carbon Electrodes

The state-of-the-art in supercapacitors and capacitive deionization technology utilizes high surface area carbons which store energy in electric double layers (EDLs) at the carbon surface/electrolyte solution interface. To reach high energy density, a fundamental understanding of the nature of ion and solvent adsorption into their porous volume is required. We review herein a novel approach to in situ gravimetric monitoring of the compositional changes in porous carbon electrodes during their charging using the electrochemical quartz crystal admittance (EQCA) method. In addition to gravimetric sensing, mechanical changes in the electrode coating under different charge/discharge/storage regimes can be monitored with high precision and sensitivity. Adsorption of ions in charged meso- and microporous carbons studied by EQCA was interpreted by linking them to the classical EDL models and capacitive deionization theory. Focus is provided for application of EQCA in characterizing adsorption of different series of ions, including determination of the number of solvent molecules accompanying ions during their adsorption and monitoring the molecular interactions between the adsorbed ions and bulk water.

History Matching Time-Lapse Surface-Gravity and Well-Pressure Data With Ensemble Smoother for Estimating Gas Field Aquifer Support—A 3D Numerical Study

Summary Water influx is an important factor influencing production of gas reservoirs with an active aquifer. However, aquifer properties such as size, porosity, and permeability are typically uncertain and make predictions of field performance challenging. The observed pressure decline is inherently nonunique with respect to water influx, and large uncertainties in the actual reservoir state are common. Time-lapse (4D) gravimetry, which is a direct measure of a subsurface mass redistribution, has the potential to provide valuable information in this context. Recent improvements in instrumentation and data-acquisition and -processing procedures have made time-lapse gravimetry a mature monitoring technique, both for land and offshore applications. However, despite an increasing number of gas fields in which gravimetric monitoring has been applied, little has been published on the added value of gravity data in a broader context of modern reservoir management on the basis of the closed-loop concept. The way in which gravity data can contribute to improved reservoir characterization, production-forecast accuracy, and hydrocarbon-reserves estimation is still to be addressed in many respects. In this paper, we investigate the added value of gravimetric observations for gas-field-production monitoring and aquifer-support estimation. We perform a numerical study with a realistic 3D gas field model that contains a large and complex aquifer system. The aquifer support and other reservoir parameters (i.e., porosity, permeability, reservoir top and bottom horizons) are estimated simultaneously using the ensemble smoother (ES). We consider three cases in which gravity only is assimilated, pressure only is assimilated, and gravity and pressure data are assimilated jointly. We show that a combined estimation of the aquifer support with the permeability field, porosity field, and reservoir structure is a very challenging and nonunique history-matching problem, in which gravity certainly has an added value. Pressure data alone may not discriminate between different reservoir scenarios. Combining pressure and gravity data may help to reduce the nonuniqueness problem and provide not only an improved gas- and water-production forecast and gas-in-place evaluation, but also a more-accurate reservoir-state description.

72 A plasma etching and gravimetric monitoring system (PEGMS) for lipid and protein location studies

Purpose: In the tear film lysozyme makes up approximately 35% of the total protein detected and is widely implicated in contact lens spoilation. It functions primarily as a bacteriolytic enzyme in the innate defense of the ocular surfaces. Recently interest in this protein has focused on its ability to function effectively in the presence of contact lens and care solution products. Method: The classic methods based on its interaction with, and the lysis of, the Grampositive bacterial strainMicrococcus lysodeicticus,measured by turbidity at 450nm, were used to investigate lysozyme antimicrobial activity. In addition a fluorescence-based assay which measures the digestion products from a DQTM lysozyme substrate, with excitation maxima at 494nm and fluorescence emission maxima at 518nm, was assessed. Results: Disadvantages of turbidity based assayswere apparent. Additionally many studies use egg white lysozymes as a cheaper assay alternative to human sourced protein, but in addition to compositional variation, human and chicken lysozymes differ in enzymatic activity with a 4:1 ratio respectively. Batch to batch variation in lysozyme preparations was also observed. The kinetic fluorescencebased assaywhich was able to detect activity down to 20U/ml was established and was used to assess the effects that extraction techniques and sample preparation have on the outcome of the activity data. Conclusions: An investigation into the true nature and extent of lysozyme denaturation, which is essential to determine the importance of this phenomenon and its impact on tear film anti-microbial function, was facilitated by more sensitive and varied analytical techniques.

The Effects of Near-zero Leachate Irrigation on Growth and Water Use Efficiency and Nutrient Uptake of Container Grown Baldcypress (Taxodium distichum (L.) Rich.) Plants

Abstract Fertilization and irrigation practices affect water-and nutrient use-efficiencies in container-produced nursery crops. This study was conducted to determine if gravimetric monitoring of a plant-substrate-container unit could manage real-time irrigation volume to achieve a near zero leachate fraction and to study baldcypress (Taxodium distichum (L.) Rich.) growth, nutrient accumulation and water-use efficiency under a factorial combination of two irrigation leachate fractions and two controlled release fertilizer (CFR) rates. Baldcypress plants were grown at either 45 or 90 g of 15N–3.1P-12.5K (15-7-15 Multicote, six-month controlled release fertilizer top dressed on each container), and two irrigation rates, near-zero or 0.2 leachate fraction. Height growth, whole plant dry mass and shoot: root dry mass ratios, and water-use efficiency were not affected by a fertilizer and irrigation interaction. The higher fertilizer rate increased the whole plant N and K concentrations. Relative to a 20% leachate fraction irrigation regime, a near-zero leachate fraction decreased leachate volume and root, shoot and whole plant dry mass, while leachate electrical conductivity (EC), plant tissue mineral nutrient concentrations and water use efficiency increased. Although baldcypress whole plant dry mass was reduced under the near-zero leachate irrigation regime (presumably due to high soluble salt levels) there was no difference in height and stem diameter at the higher fertilizer rate between the two irrigation regimes. The near-zero leachate irrigation regime applied approximately one-half the irrigation volume of the 0.2 LF irrigation regime.

In situ Gravimetric Monitoring of Thermal Decomposition and Hydrogen Etching Rates of 6H-SiC(0001) Si Face

The thermal decomposition and hydrogen etching of a 6H-SiC(0001) Si-face were directly monitored using an in situ gravimetric monitoring system. The monitoring of the weight change of the 6H-SiC Si-face using this system clarified the dependences of the thermal decomposition and hydrogen etching rates on the substrate temperature. Although the thermal decomposition of the 6H-SiC Si-face above 1400 °C generated a graphite layer since only the Si atom directly desorbs from the surface, the etching of the 6H-SiC Si-face by hydrogen did not form this layer, and both Si and C atoms react with hydrogen. Moreover, the surface reaction of the 6H-SiC Si face with H2 and the resultant surface morphology were found to change at approximately 1250 °C.

Love wave immunosensor for antibody recognition using an innovative semicarbazide surface functionalization

A new novel and easy functionalization route of a Love wave acoustic sensor based on the α-oxo-semicarbazone bond is described. The interest is firstly to observe in real-time the immobilization of the peptide on the semicarbazide surface of the transducer and secondly to monitor the specific binding of antibodies. Site-specific immobilization of antigenic-peptides as well as binding of murine monoclonal antibodies has been shown by gravimetric measurements. A tetramethylrhodamine-labeled goat antibody directed against murine antibodies was used to further characterize the biomolecular interactions by fluorescence microscopy and surface analysis (by AFM). Our data show that the gravimetric monitoring developed from the prepared Love wave immunosensor is a promising alternative route to characterize chemical and biomolecular events.

In situ gravimetric monitoring of surface reactions between sapphire and NH 3

Surface reactions between a (0 0 0 1) C-plane sapphire and NH 3, with He as an inert carrier gas, were investigated at high temperatures over 1200 °C using the in situ gravimetric monitoring method. Although the sapphire substrate was stable up to 1400 °C under a He atmosphere, decomposition started to occur at 1300 °C under a 0.1 atm NH 3+He and the decomposition rates were found to be lower than those in 0.1 atm H 2+He at each temperature. These results imply that sapphire can be decomposed by NH 3 and/or hydrogen generated by the decomposition of NH 3 over 1300 °C. The decomposition rate in NH 3+He was decreased with increase in NH 3 flow time, and the decomposition rate became constant after 60 min of NH 3 flow. Moreover, the activation energy for sapphire decomposition before 60 min of NH 3 flow was different from that after 60 min of NH 3 flow time, which indicates that the surface reaction between sapphire and NH 3 and/or hydrogen generated from NH 3 changes depending on the time of NH 3 flow. The dependence of the surface reactions and rate-limiting reactions between sapphire and NH 3 on the time of NH 3 flow is discussed.

Gravimetric monitoring of gas-reservoir water influx — A combined flow- and gravity-modeling approach

Knowledge of the magnitude and distribution of water influx can be essential for managing water-drive gas fields. Geophysical fieldwide monitoring can give valuable information, particularly offshore where well control is sparse and observation wells are expensive. Advances in the accuracy of seafloor time-lapse gravimetry have made this method feasible. It can quantify which areas are flooded, providing information complementary to well-monitoring, production, and 4D seismic data. Gravimetric monitoring may aid material-balance calculations, which are vital for assessing reservoir-drive mechanism and estimating initial and remaining gas volumes. In addition, it can constrain reservoir simulation models. Our goal is to produce better physical insight into typical density changes occurring in water-drive gas fields and their associated surface-gravity response. It is feasible to monitor displacement of gas by water in reservoirs that are only a few meters thick. Gravimetric monitoring can detect edgewater encroachment in early stages. With current accuracy, the method is applicable for gas reservoirs of modest size ([Formula: see text] in situ gas volume) at medium depths [Formula: see text].