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A silica gel was applied in a porous gas reservoir, with the purpose of testing mitigation and remediation of CO 2 leakage from geological storage reservoirs. The gel has a high strength and a very low water-like viscosity, that extends its applicability to small pore diameters and low permeability media. The gel was prepared and applied on-site with oilfield equipment. Mixing was upscaled from laboratory- to field-scale, including one unsuccessful attempt. Environmental concerns and additional health and safety requirements were modest as the formulation was composed only of the non-toxic commercial silica-based product Betol K28 T, acetic acid and fresh water. A well was selected and prepared in the Becej natural CO 2 field in Serbia, the well and reservoir were prepared and the gel was placed into a 600 m deep CO 2 - and CH 4 -bearing sandstone layer. The reservoir was selectively sealed to the gas cap through a fast, CO 2 -selective gelation, while the hydraulic pathways of the liquid-filled part of the reservoir remained open. In the regions where no CO 2 was present the gelation reaction was slower and the kinetic was temperature-accelerated. A numerical model was used to simulate the impact of the pre-injection operational procedures and to quantify the impact on the temperature-dependent gelation time. The workflow aligns the needs of a research project with the interests and practical priorities of an operating company. A© 2019 Elsevier Ltd

In 2003 the mature gas field K12-B was selected as a demonstration site for offshore injection of CO2. The initial project was aimed at investigating the feasibility of CO2 injection and storage in depleted natural gas fields on the Dutch continental shelf, with the objective to realize a permanent CO2 injection facility. Over the years many different aspects related to CO2 storage at K12-B have been researched, most of them widely applicable to other CO2 storage sites as well. CO2 injection and related research projects involving K12-B have continued until 2017, completing a period of almost 15 years of CO2 injection. This paper presents an overview of the most relevant and memorable research topics, their related activities and results. The K12-B gas field, is located in the Dutch sector of the North Sea, some 150 km northwest of Amsterdam. It was developed and operated by predecessors of the current operator, which since 2017, is Neptune Energy Netherlands B.V. K12-B has been producing natural gas from the Permian age, Upper Slochteren Member (Rotliegend) since 1987. The natural gas produced has a relatively high CO2 content (13%) and the CO2 is separated from the production stream on site, prior to gas transport to shore. The CO2 used to be vented into the atmosphere but from 2004 on it has been injected into the gas field above the gas-water contact; at a depth of approximately 4000 m. K12-B was the first site in the world where CO2 has been re-injected into the same reservoir from which it originated. The average CO2 injection rate could reach 30,000 Nm3 CO2 per day, which is approximately 20 kt per year. This paper presents an overview of the results and lessons learned of the multiple measurements campaigns and numerous research projects related to the CO2 injection at K12-B since 2004, performed by the operator and TNO. The research ranged from the investigation of top side and well equipment to the behavior of the gas field to social, environmental and risk assessment aspects. This paper will take you through our journey where we encountered anomalous tubing thicknesses, abnormal downhole injection pressures and surprising chemical evaluations. The paper will present how we learned more and more about the reservoir itself through the analysis of tracer chemicals breaking through, continuous extensive reservoir modelling, geomechanical modelling and even the actual back production of re-injected CO2. This paper shows what valuable knowledge and information the CO2 injection project at K12-B has produced over the years. CO2 injection at K12-B was stopped when end 2017 the separation of CO2 at K12-B itself came to a halt. Without the active separation of CO2 on site there was no supply of CO2 anymore, which could be injected into the reservoir.

Greenhouses in The Netherlands use elevated CO2 levels to enhance crop growth. Currently, they obtain most of their CO2 through combustion of natural gas in combined heat and power installations. An increasing number of greenhouses is moving away from natural gas, switching to geothermal energy as a heat source and using CO2 from industrial sources. Supporting this transition to sustainable energy for greenhouses would require an increase in and secure supply of external CO2. This could be achieved via seasonal buffering of CO2 in a sandstone reservoir to match supply and demand, and provide security of supply during periods of maintenance at the industrial supply sites. This paper explores the potential of the depleted gas and condensate field Q16-Maas as a seasonal CO2 buffer, by estimating the maximum feasible injection and production rates and cumulative seasonal buffered volumes. With a CO2 storage capacity of about 2 Mt, the gas field would require two 6-months injection periods, before commencing regular production – injection cycles. Both injection and production of CO2 occur at a rate of 20 kg/s. This would lead to an additional CO2 supply to the greenhouses of 315 ktonne in summertime, increasing current offtake by about 60%, leading to a correspondingly decreasing use of natural gas. The back-produced CO2 will be contaminated with hydrocarbons, primarily CH4, with a concentration as high as 20% in the first injection cycle, decreasing with each consecutive cycle. The hydrocarbons can however easily be separated from the CO2 by the use of a condenser and flash separator. The primary constraint on the buffer potential comes from the back-production conditions in the production well. Well dynamics simulations show that the pressure and temperature decrease of the CO2 during its ascend from bottom hole to wellhead is higher when the production volume increases. The conditions of the CO2 during production should remain above both two-phase and hydrate formation conditions. Optimal conditions within the reservoir and well constraints are obtained when the bottom-hole CO2 temperature is at the reservoir value of 105 °C. This requires significant compression during injection to wellhead conditions of 80 °C and 147-159 bar, but maximises the back-production rate at 20 kg/s. Rough cost estimates for the wellhead facilities and separation technologies show that seasonal buffering could be economically attractive.

This paper explores the concept of combining a geothermal energy system with CO2¬ storage. Introducing CO2 in dissolved form into the cold return stream of a geothermal doublet would lead to inherently safe CO2 storage, while generating the possibility of an additional revenue stream for the a geothermal operator. Moreover this concept could also provide a solution for smaller emitters, located far from storage sites or transportation facilities, but close to (potential) geothermal systems. It uses a low-cost CO2 capture technology. Storing CO2 in dissolved phase by co-injection with the geothermal water, increases storage security and safety compared to supercritical storage. The absence of buoyancy as an upward migration force removes the risk of leakage. Because of this, a caprock is not required and therefore more storage sites become available. This is only true if degassing, both on the short- and the long-term, can be excluded. The design of the entire chain therefore takes into account the solubility limit of CO2 in the geothermal water at all conditions which occur during the operational phase and beyond. Reservoir simulations were performed on a existing geothermal reservoir in the greenhouse area in The Netherlands to investigate the feasibility of CO2 co-injection and potential impacts on the geothermal operations and the business case. Results show that, for the conditions considered, no (significant) breakthrough of either the cold front or the dissolved CO2 are predicted to occur within 30 years of continuous operations. Also, the simulations show that all CO2 remains dissolved and hence no degassing takes place. An initial cost estimate indicates that with current emission reduction credits the return on investment of the CO2-Dissolved concept can be achieved within a few years, and is therefore an economically attractive addition for a geothermal operator.

Since 2004 the feasibility of CO2 injection and storage in depleted natural gas fields has been researched and demonstrated at K12-B, a gas field on the Dutch continental shelf. In total over 100 Kton of CO2 was injected. The entire operation at the K12-B field was completed without any major complications. It can therefore be stated that safe and uneventful underground storage in depleted gas fields is possible. During the many activities taking place at K12-B, numerous techniques were tested and enhanced and many processes, including corrosion tests, investigated. This has helped in assessing other projected CCS projects, such as P18. There is now a proven track record of over a decade of continuous CO2 injection, supported by many risk assessment studies. The findings of this extensive scientific CO2 re-injection research can be showcased and applied to other Carbon Capture and Storage Projects in the world. One year ago the project came to an end. In this abstract we present some of the highlights.

International audience; In this paper, we present an overview of the SiteChar workflow model for sitecharacterisation and assessment for CO2 storage. Site characterisation and assessment is requiredwhen permits are requested from the legal authorities in the process of starting a CO2 storageprocess at a given site. The goal is to assess whether a proposed CO2 storage site can indeed beused for permanent storage while meeting the safety requirements demanded by the EuropeanCommission (EC) Storage Directive (EU, 2009, Storage Directive 2009/31/EC). Many issueshave to be scrutinised, and the workflow presented here is put forward to help efficiently organisethis complex task.Three issues are highlighted: communication within the working team and with the authorities;interdependencies in the workflow and feedback loops; and the risk-based character of theworkflow. A general overview (helicopter view) of the workflow is given; the issues involved incommunication and the risk assessment process are described in more detail. The workflow asdescribed has been tested within the SiteChar project on five potential storage sites throughoutEurope. This resulted in a list of key aspects of site characterisation which can help prepare andfocus new site characterisation studies.

This paper reports modeling of gas field production and CO2 injection in a theoretical reservoir based on characteristics of the P18 gas field in the Dutch offshore, which consists of four geological deposits with different petrophysical properties. We especially focus on the brine flow during and after exploitation of the reservoir, which affects salt precipitation and dissolution in the near-well area. We first computed the water saturation with depth, in static equilibrium with a free water level at the bottom of the reservoir. We then computed production from the gas field, predicting very low brine production and mobility, without salt precipitation. Subsequently, injection of dry CO2 leads to dry-out and salt precipitation in the near-well bore area, resulting in a maximum permeability reduction of 23%. After abandonment, brine flows toward the well, resulting in redissolution of precipitated salt, leading to salt saturated brine in the near-well bore area. After 1,000 years, it is predicted that supersaturated brine is concentrated in the lower part of the reservoir, where solid salt still remains. The computed long-term effects of brine mobility could influence predictions of well-cement degradation and well-abandonment strategies like intentional clogging

This paper presents the results from an assessment of high-capacity storage options in the offshore area of The Netherlands. For deep saline formations, available regional geological maps were combined with fault structures derived from seismic data to reveal the compartmentalization of prospective reservoir formations. Adding knowledge concerning these formations from offshore oil and gas activities and concerning the behavior of gas fields located in these formations, resulted in a shortlist of lowest-risk, potential storage locations with a total theoretical capacity of about 1.5 GtCO2. A high-level risk analysis was performed for offshore gas fields. The largest offshore gas fields add another 350 MtCO2. The development of saline formations and gas fields is outlined; while a gas field can be converted from production to storage in 5-6 yrs, it takes at least 7 yrs to develop CO2 storage in a saline formation that has not been accessed before for hydrocarbon production.

Near the coast of Rotterdam CO 2 storage in the depleted P18-4 gas field is planned to start in 2015 as one of the six selected European demonstration projects under the European Energy Programme for Recovery (EEPR). This project is referred to as the ROAD project. ROAD (a Dutch acronym for Rotterdam Capture and Storage Demonstration project) is a joint project by E.ON Benelux and Electrabel Nederland/GDF SUEZ Group and is financially supported by the European Commission and the Dutch state.A post-combustion carbon capture unit will be retrofitted to EONs' Maasvlakte Power Plant 3 (MPP3), a new 1100MWe coal-fired power plant in the port of Rotterdam. The capture unit has a capacity of 250MWe equivalent and aims to capture 1.1million tonnes of CO 2 per year. A 20km long insulated pipeline will be constructed to the existing offshore platform operated by TAQA and an existing well will be worked over and re-used for injection. Natural gas production in the P18-4 field is projected to end just before the start of the CO 2 injection. In this first phase a total storage of around 5Mt CO 2 is envisaged with an injection timeframe of 5 years. This paper gives a description of the field and of the studies carried out to investigate the suitability of the field for CO 2 storage. © 2012.

Dynamic reservoir simulation models have become an essential tool in oil field management. They can be used to explore the impact of alternative development and operating strategies, and can even be used to search for strategies that are optimal in some desired sense. Robust strategies can be obtained by use of an ensemble of models that are all consistent with available data but that adequately represent the uncertainty. In this paper we demonstrate an application of a workflow to obtain multiple models that are all consistent with historic time-lapse seismic data. We show how these models can subsequently be used to obtain optimal recovery strategies, and discuss how this approach can be extended to optimization under uncertainty. The history matching step is performed using an ensemble-based methodology and an efficient parameterization of the time-lapse seismic data. The optimization step takes the history matched model (or model ensemble to account for all uncertainty) as input. An approximate gradient computation provides improved strategies. The history matching workflow is demonstrated on a representative sector of a field that is developed with both vertical and horizontal wells and is produced with simultaneous injection of water and CO2. Evaluation of the history matching step indicates a good match with the seismic data, indicating the power of the parameterization method for handling very large numbers of seismic data. It is discussed that production data can be matched simultaneously, given proper characterization of measurement errors. The optimization step is performed assuming an oil recovery scenario based on alternating water and CO2 injection. Appropriate cost models may be employed to arrive at operating scenarios that result in the maximum expected economic value. Results will depend on, amongst other aspects, the chosen economic model, indicating that best operating practices will be region specific. The combination of advanced yet practical workflows for assisted history matching and recovery optimization is the result of many developments over the past 10 years. We argue that the cumulative result of these efforts provides significant value to field developments by enabling consistency with measurements, reduction of uncertainties and improved optimization of operational strategies.

An intermediate-scale experiment in a 1.02-m-long, 0.75-m-high, and 0.05-m-wide flow cell was conducted to investigate the behavior of a viscous LNAPL under variable water table conditions. Two viscous LNAPL volumes (0.4 L) were released, one week apart, from a small source zone on top of the flow cell into a partly saturated, homogenously packed porous medium. Following a redistribution period of 30 days after the second release, the water table was increased 0.5 m in 50 minutes. After the water table rise, viscous LNAPL behavior was monitored for an additional 45 days. Fluid saturation scans were obtained periodically with a fully automated dual-energy gamma radiation system. Results show that both spills follow similar paths downwards. Within two hours after the first LNAPL arrival, the capillary fringe was reduced across the cell by approximately 0.04 m (22%). This reduction is directly related to the decrease in the air-water surface tension from 0.072 to 0.057 N/m. LNAPL drainage from the unsaturate...

Geological storage of CO2 in large, saline aquifers needs to be monitored for safety purposes. In particular the observation of the pressure behavior of a storage site is relevant for the indication of CO2 leakage. However, interpretation of observed pressure is not straightforward in these systems, due to the large number of natural processes that affects the pressure. These processes include pressure dissipation across aquifer boundaries for which both location and transmissibility are uncertain, pressure dissipation in low-permeable deposits surrounding the aquifer, dissolution of CO2 into the brine and chemical reactions. In this paper we will focus on the aquifer pressure effects of dissolution of CO2 in brine which can be significantly enhanced by density-driven convective mixing. The convective mixing occurs because the density of brine increases due to the dissolution of CO2, creating an unstable layer of dense brine below the CO2 plume. This layer may induce vertical, density-driven convective flow in so-called fingers. We have studied the effect of convectively-enhanced CO2 dissolution on the pressure in a CO2 storage site for 50 years using a volume balance model. This showed that only for reservoirs with very high permeability (>500mD in vertical direction) and a thin CO2 layer (0.05bar/yr). For most examples simulated here, the effect of CO2 dissolution on the pressure was minor (

An intermediate-scale flow cell experiment was conducted to remove a liquid trichloroethylene (TCE) spill from a saturated, heterogeneous porous medium using pump-and-treat (P&T) as well as surfactant flushing (SF) techniques. Dissolved TCE concentrations were measured at 20 locations, while fluid saturations were obtained with a dual-energy gamma scanner. The behavior of the TCE spill has been described by Oostrom et al. (1998b) [Oostrom, M., Hofstee, C., Walker, R.C., Dane, J.H., 1998b. Movement and remediation of TCE in a saturated heterogeneous porous medium: 1. Spill behavior and initial dissolution, this issue.]. A total of six alternating P&T and SF periods were used to remediate the flow cell. A two-well system, consisting of an injection and an extraction well, was used during the first five remediation periods. For the last SF period, a three-well system was employed with two injection wells and one extraction well. During the first P&T period, most entrapped TCE was removed, but TCE saturations in a substantial pool on top of a fine-grained sand layer were largely unaffected. During the first SF period, a dense plume was formed containing solubilized TCE which partially sank into the fine-grained sand. In addition, unstable fingers developed below the liquid TCE in the pool. In several samples, small TCE droplets were found, indicating mobilization of TCE. Most of the samples with concentrations larger than 5000 ppm had a milky, emulsion-like appearance. The SF considerably reduced the amount of TCE in the pool on top of the fine-grained sand. During the second P&T period, plume sinking and instabilities were not observed. After starting the second SF period, some unstable fingering and plume sinking resumed, starting at the upstream end of the TCE in the pool. The saturation distribution obtained after the second SF period was quite similar to the one obtained after the first SF period, indicating that additional removal of TCE through SF was difficult as a result of the limited accessibility of the TCE in the pool. A gamma scan, obtained after three weeks of pumping using the three-well configuration, shows that all the liquid TCE had been removed from the coarse-grained sand. Computations based on extraction rates and measured TCE concentrations show that only about 60% of the injected TCE was removed from the cell during the experiment. Part of the missing 40% might have moved downwards into the fine-grained sand as a result of pure phase mobilization. The experimental results suggest that besides the positive effects of solubilization, possible detrimental processes such as pure phase mobilization and dense aqueous-phase plume behavior should be considered during SF.

In many studies involving a liquid and air, the effective permeability of the wetting phase (kw) is determined from the capillary pressure (Pc)–saturation (S) relation and a corresponding, measured kw value. The movement, and therefore the effective permeability, knw, of air in an air-liquid system is often ignored, especially by those who consider only the flow of water in soils. However, if a wetting and a nonwetting liquid coexist (two immiscible liquids), the effective permeability function of the nonwetting liquid must be determined as well. Rather than using some indirect method to determine the knw (Pc) or knw (S) relationship of the nonwetting liquid, we propose a direct measurement technique by using a permeameter which allows for steady state flow of the nonwetting liquid over a range of Pc and S values. During each steady state flow condition of the nonwetting liquid, Pc and S are constant and uniform throughout the permeameter, while the wetting liquid is at rest. The nonwetting liquid can either be a dense non–aqueous phase liquid (DNAPL) or a light non–aqueous phase liquid (LNAPL). The knw values are calculated as a function of Pc and S from the measured flow rates and the density difference between the wetting and nonwetting liquid. The proposed technique can be applied during drainage as well as imbibition. The S values are determined by recording the amount of water being displaced from the cell each time the Pc is changed. Results are discussed for the DNAPL perchloroethylene (PCE) and the LNAPL Soltrol.

Contamination of the subsurface by nonaqueous phase liquids (NAPLs) is a widespread problem. To investigate the behavior of a nonspreading, dense NAPL (DNAPL) in the vadose zone, we conducted perchloroethylene (PCE) infiltration experiments in nominally 1- and 2-dimensional (D), stratified porous media. In addition, the usefulness and limitations of a multifluid flow simulator to describe PCE infiltration and redistribution under the experimental conditions were tested. The physical simulations were conducted in a column (1-D) and a flow container (2-D) which were packed with two distinct layers of coarse-grained sand and a fine-grained sand layer in between. Volumetric water and PCE contents were determined with a fully automated dual-energy gamma radiation system. While migrating through the drier parts of the coarse-grained sand layers, PCE appeared to wet the water–air interface rather than displacing any water. In the wetter parts of the porous medium, PCE displaced water and behaved as a true nonwetting fluid. PCE showed a limited response to gradients in capillary pressure and rather high values for the volumetric PCE content were measured in the fine-grained sand layers. This was attributed to the nonspreading nature of PCE. The multifluid flow simulator appeared to predict the initial PCE movement in the vadose zone reasonably well. However, the model was not capable of predicting the final amounts of PCE retained in either the unsaturated or saturated part of the flow domain, mainly because the simulator does not consider the nonspreading flow behavior of NAPLs.

Dense nonaqueous phase liquids (DNAPLs), such as perchloroethylene (PCE), pose a significant threat to the environment, specifically to our drinking water present in aquifers. In many instances, a DNAPL will become trapped and form pools on top of confining layers while migrating through the vadose zone. Residual DNAPL and DNAPL pools form sources of long term contamination, which are difficult to remove by classical pump-and-treat remediation. A physically simulated PCE spill into a large, two-dimensional flow container, packed with a fine sand layer surrounded by coarse sand, was therefore studied in this work. A water table was maintained near the bottom of the flow container, such that the coarse sand just below the fine layer was unsaturated, but the bottom of the fine sand layer was at or near saturation. A PCE spill was applied at the center of the porous medium's surface and allowed to redistribute until static equilibrium was reached. The porous medium was then flushed with a surfactant solution (Triton X-100, 4.0% by volume), using the same application configuration as for the spill, while simultaneously extracting solution at one or more locations at the bottom of the porous medium. Effluent samples were analyzed for PCE concentrations. Volumetric water and PCE content values were determined several times at a number of locations by means of dual-energy gamma radiation measurements. The coarse sand in the upper portion of the porous medium was cleaned rapidly by the surfactant flushing. Removal of PCE from the fine sand layer, however, proved to be more difficult because most of the surfactant solution bypassed the PCE. Lateral spreading of the surfactant plume occurred near the saturated/nearly saturated zones in the fine and coarse sand. This lateral spreading, unfortunately, allowed for solubilized PCE, the concentration of which was enhanced by micelle formation, to move into regions previously uncontaminated. The pumping configuration was subsequently changed in an attempt to force the surfactant solution through the entire fine layer, i.e., to hydraulically control the surfactant flushing, while simultaneously increasing the amount of solubilized PCE.

Although surfactant enhanced remediation of nonaqueous phase liquids (NAPLs) by pump-and-treat technology has been studied extensively in the laboratory with one-dimensional columns, very few multi-dimensional investigations have been reported. In this study we focus on the removal of perchloroethylene (PCE) from a two-dimensional, saturated porous medium containing a low permeability sand layer situated in an otherwise high permeability sand. A PCE spill was applied at the surface of the porous medium and allowed to redistribute until static equilibrium was achieved. The porous medium was then flushed with various surfactant and co-solvent formulations injected at the PCE source location and extracted at the bottom of the porous medium using a configuration similar to that of Abdul and Ang [Abdul, S.A., Ang, C.C., 1994. In situ surfactant washing of polychlorinated biphenyls and oils from a contaminated field site: Phase II. Pilot study. Ground Water 32, 727–734]. Effluent samples were analyzed for dissolved PCE concentrations. Volumetric water and PCE content values were determined at a number of locations by means of dual-energy gamma radiation measurements. Once surfactant flushing had started, PCE moved as a distinct separate phase ahead of the surfactant front. Most of this downward moving PCE accumulated on top of the low permeability sand layer. Some PCE, however, passed quickly through this layer and subsequently through the high permeability sand below it. Movement of some of the PCE into and through the low permeability sand layer was attributed to local heterogeneities combined with reduced interfacial tensions associated with the surfactant formulation. Clean-up of PCE in most of the high permeability sand was considered to be effective. PCE accumulated on top of the fine layer, however, posed a significant challenge to remediation and required several pumping configurations and surfactant/co-solvent formulations before most of it was removed.

When dual-energy gamma radiation systems are employed for measurements in porous media, count rates from both sources are often used to compute parameter values. However, for several applications, the count rates of just one source are insufficient. These applications include the determination of volumetric liquid content values in two-liquid systems and salt concentration values in water-saturated porous media. Single-energy gamma radiation procedures for three applications are described in this paper. Through an error analysis, single-source procedures are shown to reduce the probable error in the determinations considerably. Example calculations and simple column experiments were conducted for each application to compare the performance of the new single-source and standard dual-source methods. In all cases, the single-source methods provided more reliable data than the traditional dual-source methods. In addition, a single-source calibration procedure is proposed to determine incident count rates indirectly. This procedure, which requires packing under saturated conditions, can be used in all single- and dual-source applications and yields accurate porosity and dry bulk density values.

Although infiltration, redistribution, and drainage of dense non-aqueous-phase liquids (DNAPLs) in water-saturated soils and aquifers are known to be sensitive to stratifications of the solid phases of the porous media, little experimental evidence is available to explain the behavior of DNAPL movement. To improve our understanding of I)NAPL movement under these conditions, physical simulations were conducted with various perchloroethylene (PCE) spills in initially water-saturated, stratified porous media in nominally one-dimensional glass columns and in an intermediate scale, nominally two-dimensional laboratory flow container. The columns and flow container were packed with two distinct layers of coarse sand, with a fine sand layer in between. Volumetric water and DNAPL contents, as well as bulk densities, were determined with a dual-energy, gamma radiation system. To obtain additional information required for the explanation of the displacement processes, in- and outflow rates of water and PCE were measured during each experiment. In the sand columns, PCE accumulated on top of the fine layer, while in the flow container, considerable lateral movement was observed just above the fine sand layer. In general, these phenomena were attributed to the small conductivity values of the fine layers relative to those of the coarse layers rather than to displacement pressures not being exceeded. Overall our results suggest that in field situations, continuous PCE spills are more likely to penetrate horizontal fine layers than short intermittent spills.

The IMPACTS project has a stated broad objective to develop the knowledge base of CO2 quality required for establishing norms and regulations to ensure safe and reliable design, construction and operation of CO2 pipelines and injection equipment, and safe long-term geological storage of CO2. More specifically for this paper, the project sets out to reveal the impacts of relevant impurities in the CO2 stream on the design, operation and costs of the capture, transport and storage infrastructure and to provide recommendations for optimized CO2 quality through techno-economic assessments (amongst other considerations). This paper gives an overview of the work being carried out to investigate the impact of CO2 quality in various areas including corrosion, water content in the CO2 stream and the injection and storage processes. The paper reports on the derived impacts of the above mentioned aspects of CO2 quality. These impacts are combined with estimates of the cost of measures to mitigate or prevent these impacts from affecting the operation of the CCS system, or of adapting of CCS system design. Thus, the impacts can be set out as a set of cost functions relating to Capex and Opex and including the effects of overall availability and process efficiency changes. A specifically designed CCS chain model is used to assess the impacts on a number of reference CCS chains, carrying out comparative economic trade-offs to both understand the full- chain whole-life economics of certain CO2 impurities at different levels and then to potentially optimize a purity specification for various sets of circumstances.

Numerical simulations with the multifluid flow simulator STOMP are compared with quantitative results of a detailed lighter-than-water nonaqueous-phase liquid (LNAPL) infiltration and redistribution experiment in a 1.67-m-long, 1-m-high, and 0.05-m-wide flow cell. The experiment was performed to test the ability of commonly used nonhysteretic and hysteretic constitutive relations between relative permeability (k), fluid saturation (S), and capillary pressure head (h) to describe multifluid flow in two dimensions. The fluid and sand parameters necessary to apply the constitutive relations were obtained independently. The flow cell was filled with a homogeneous sand mixture under saturated conditions. After partial drainage of the sand, the LNAPL was slowly injected for 12 h from a small source area located at the surface. A dual-energy gamma radiation system was used to determine LNAPL and water saturations at 255 locations during infiltration and redistribution. The results show a reasonable match between the experimental and numerical data, indicating that the constitutive relations used are adequate to describe relatively slow LNAPL infiltration and redistribution. The differences between the nonhysteretic and hysteretic simulations are small. This implies that hysteresis, a result of nonwetting fluid entrapment and pore geometry, was not important in this experiment.

A classical way to obtain three-fluid retention curves in porous media from measured two-fluid retention curves is based on the Leverett concept, which states that the total volumetric liquid content in a water-wet porous medium, containing water, a nonaqueous-phase liquid (NAPL) and air, is a function of the capillary pressure across the interface between the continuous NAPL and air. This functional relationship results from the assumed condition that in a three-fluid porous medium, the intermediate wetting fluid spreads over the water-air interface. Application of Leverett's concept may not be valid, however, for nonspreading NAPLs like perchloroethylene (PCE). This paper discusses measurements of both PCE-air and water-PCE-air retention curves using a long vertical column in conjunction with a dual-energy gamma radiation system. The data indicate that the Leverett concept was applicable only until a critical PCE saturation had been reached.

Quadricyclane, a highly strained hydrocarbon, is currently being evaluated by the U.S. Air Force as a possible high-performance aviation fuel. It is therefore important to discover how it would interact with the environment in the event of a spill. The reactions of quadricyclane were investigated in water, 50/50 wt % water/2-propanol and pure 2-propanol, and in abiotic aqueous soil environments consisting of four different naturally occurring soils. The reaction products were exo-5-norbornen-2-ol and nortricyclyl alcohol. The reactions in the three solvent systems were pseudo-first-order in quadricyclane. Second-order rate constants were determined from plots of the pseudo-first-order rate constants versus [H+] and were found to be 26.0 L mol-1 min-1 in water, 0.195 L mol-1min-1 in 50/50 water/2-propanol, and 0.099 L mol-1min-1 in 2-propanol, all at 25 °C. The soil experiments were run for periods of up to 9 months. The most important factor affecting the reactivity of quadricyclane in the soils was pH, w...

The P18-4 compartment (operated by TAQA Energy B.V.) would be injected by CO2 at a minimum temperature of 12 degrees C. At these temperatures, the CO2 phase will either be a gas or a liquid. As the initial temperature of the reservoir is 120 oC, the CO2 will eventually be the gaseous or (at higher pressures), the supercritical phase. An outstanding issue was the simulation of the fate and transport of the injected liquid CO2, with emphasis on the temperature effects. In this presentation, we will present results of our latest research efforts.

Carbon Capture and Storage (CCS) is one of the solutions that can significantly reduce CO 2 during the transition from fossil fuel-based energy to an energy system based on renewable energy sources. Recent studies point out that sufficient storage capacity in saline aquifers and depleted gas fields is available to permanently store several decades worth of current CO 2 emissions. Nevertheless, a significant hurdle for the post-demonstration phase of CCS development is the lack of proven and tested storage reservoirs. One of the goals of the EU FP7 SiteChar project is to develop an efficient site characterisation workflow, to support the development of the numerous storage sites that will be needed for large-scale deployment of CCS. The workflow is designed to address all aspects of safe and secure storage required by the EU Storage Directive. The links between the Storage Directive requirements and the site characterisation workflow are described in detail. The workflow is currently being applied to five sites suitable for CCS across Europe. A final version of the workflow will be published early 2014.

Based on a first phase, regional screening, the P18 cluster was selected as a logical first candidate for development of offshore CO2 storage in the Netherlands.A detailled feasibility study is described, with special focus on the complex history matching

In support of the early deployment of CCS in Rotterdam (Netherlands) and the development of a Rotterdam CCS Network by 2015, this paper presents the results of a first screening assessment in the P and Q blocks in the offshore area, which is the area clos

The K12-B gas field is located in the Dutch sector of the North Sea. The top of the reservoir lies approximately 3800 meters below sea level, and the ambient temperature of the reservoir is over 127 °C. The K12-B gas field has been producing natural gas from 1987 onwards and is currently operated by GDF SUEZ E&P Nederland B.V. The natural gas has an initial CO2 content of 13%, which is relatively high. Since the start of the gas production the CO2 component has been separated from the natural gas stream on-site and since 2004 part of the separated CO2 is re-injected into the gas field. In 2004 a demonstration project commenced where CO2 was re-injected into K12-B. The goal was to investigate the feasibility of CO2 injection and storage in depleted natural gas fields. More than 6 years later CO2 injection is still taking place and numerous monitoring techniques have been applied in order to get a better understanding of various aspects of underground CO2 storage in nearly depleted gas fields. Over the years monitoring activities have mainly focused on the well integrity and on the behavior of the CO2 in the well and reservoir. The cap rock present at K12-B consists of hundreds of meters of rock salts from the Zechstein Super Group. The most likely migration pathway for any gas, should migration occur at all is therefore along the well bores. Establishing the conditions of wells is of great importance for safety issues. Some of the tools which have been used will be discussed. Another goal for the various monitoring activities is to gain a better understanding of the behavior of the CO 2 in the injection wells and the migration of the CO2 in the reservoir. How the CO2 migrates in the reservoir is important as regards the assessment of the potential for enhanced gas recovery (EGR) by CO2 injection. © 2011 Published by Elsevier Ltd.

K12-B is the first site in the world where CO2 is being injected into the same reservoir from which it was produced as part of the natural gas. The K12-B gas field is located in the Dutch sector of the North Sea and was discovered in 1982. The gas is prod

The minimum injection depth for the storage of CO2 is normally set at 800 metres. At and beyond this depth in the subsurface conditions exist where CO2 is in a so-called critical state. The supercritical CO2 has a viscosity comparable to that of a normal gas and a liquid-like density, Due to the high density of the supercritical CO2, storing the CO2 in the supercritical state is the most efficient geological storage. The CO2 will therefore be injected below the transition zone between subcritical and supercritical conditions. In the case of CO2 storage in large aquifers, some part of the storage formation may lie at shallower depths where CO2 occurs in gas phase. The CO2 will also occur in the subcritical state (gas phase) in the case of an unintentional CO2 leak from an existing storage site. In both cases it is crucial to understand how the CO2 will behave when it reaches and passes this transition zone. In the case of intentional CO2 injection in a shallow aquifer this knowledge is important to determine both the injection strategy and the available storage capacity of the aquifer; in the case of leakage, safety and risk assessment. In this paper we present the results of a reservoir simulation study, supported by a literature study, that considers the principles of CO2 phase behaviour in the subsurface, and the implications for the injection strategy and storage volumes. © 2009 Elsevier Ltd. All rights reserved.

The Nederlandse Aardolie Maatschappij (NAM) is looking into the feasibility of a CO2 injection and storage demonstration project near the Shell refineries in the Port of Rotterdam. As a first storage option the abandoned De Lier gas reservoir was identified and an extensive feasibility study concerning this specific site was conducted. This investigation was performed by teams from both the operator and the research institute. The main objective of the study was to assess the safe and effective containment of CO2 to be injected in the Holland Greensand gas reservoir in the De Lier field.

The project Offshore Re-injection of CO2 (ORC) aims to investigate the feasibility of CO2 injection and storage in depleted natural gas fields in the Netherlands. The objective is to realize a permanent CO2 injection facility in the near future. The mature gas field K12-B was selected as demonstration site for the ORC project. The project is subsidized by the CRUST subsidy arrangement of the Dutch Ministry of Economic Affairs. K12-B is the first test site in the world where CO2 is injected into the same reservoir from which it originated. A unique measurement program is being executed including the use of tracers and the monitoring of pressure and temperature at various locations. This paper presents the preliminary results of the second test in K12-B which commenced in February 2005 and, in case of sufficient CO2 supply, will continue at least until the second half of 2006. The measurements of this test are difficult to interpret as a result of unexpected features in the pressure data. The use of tracers has contributed to an improved understanding of how these data should be interpreted. The storage potential and potential for enhanced gas recovery are currently under investigation.

A common aspect of innovative remediation techniques is that they tend to reduce the interfacial tension between the aqueous and non-aqueous phase liquids, resulting in mobilization of the organic contaminant. This complicates the remediation of aquifers, contaminated with Dense Non-Aqueous Phase Liquids (DNAPLs), as they are likely to migrate downwards, deeper into the aquifer and into finer layers. A possible solution is the use of swelling alcohols, which tend to reduce the density difference between the aqueous phase and the DNAPL. To avoid premature mobilization upon the initial contact between the DNAPL and the alcohol, several researchers have proposed the use of vertical upward flow of the alcohol. In this paper, we present an equation, which describes the upward mobilization of both continuous and discontinuous DNAPLs and so the important parameters governing the upward controlled mobilization of the DNAPL. The need and required magnitude of this specific discharge was investigated by conducting four column experiments in which the initial density of the DNAPL and the permeability was varied. It was shown that the required flow velocities increase with the permeability of the porous medium and the initial density difference between the aqueous phase and the DNAPL. Whenever the specific discharge falls below the critical value, the DNAPL moves downward. A second set of column experiments looked at the impact of permeability of porous medium on the solubilization and mobilization of DNAPL during alcohol flooding. Columns, packed with coarse or fine sand, containing a residual trichloroethylene (TCE) or perchloroethylene (PCE) saturation were flushed with the alcohol mixture at a fixed specific discharge rate. The induced pressure gradients in the aqueous phase, which were higher in the fine sand, resulted for this porous medium in extensive mobilization of the DNAPL against the direction of the buoyancy force. The density of the first NAPL coming out of the top of the fine sand was close to that of the pure DNAPL. In the coarser sand, the pressure gradients were sufficient to prevent downward migration of the DNAPL, but upward mobilization was minimal. The predominant removal mechanism in this case was the much slower solubilization.

A side effect of in situ groundwater remediation techniques that operate by establishing reducing conditions within an aquifer is that anoxic water exits these zones, posing a potential risk to aquatic organisms inhabiting areas of groundwater discharge downgradient from the site. A number of processes have been identified that can attenuate an anoxic plume in an unconfined aquifer with a fluctuating water table. The hypothesis that water table fluctuations increase oxygen transfer from air to water, through enhanced exchange from entrapped air, is tested in an intermediate-scale, fluctuating water table experiment. A dual-energy gamma radiation system was used to measure water saturations while dissolved oxygen (DO) concentrations were measured with flow-through oxygen microelectrodes. A hysteretic multifluid simulator was used to test whether the experimentally obtained water and entrapped air saturations, as well as DO concentrations, could be predicted using the assumptions of two- phase flow and equilibrium partitioning between the gas and the aqueous phases. The experimental results show that zones with entrapped air, formed during the imbibition portions of the experiment, were instrumental in re-oxygenation of the water in the zone of fluctuation. The fluctuating water table system also caused significant amounts of dissolved oxygen to be transported deepermore » into the flow cell. The simulator was able to predict water saturations, entrapped air saturations, and dissolved oxygen concentrations reasonably well.« less

The formation of residual, discontinuous nonaqueous phase liquids (NAPLs) in the vadose zone is a process that is not well understood. The simulators have conveniently implemented the Leverett concept (Leverett and Lewis, 1941) which states that in a water-wet porous media, when fluid wettabilities follow the order water-NAPL-air, the water content is a function of the NAPL-aqueous phase capillary pressure and the total liquid content is a function of the gas-NAPL capillary pressure. This concept assumes that when liquid NAPL is present in three-phase systems, the NAPL is spreading and completely covers the water phase. Nonspreading behavior, leading to residual saturations, is not addressed by the Leverett concept. To obtain data that can be used to study the development of a residual NAPL saturation in the vadose zone and to test current numerical models, detailed transient experiments were conducted. Simulations with an established multifluid flow simulator show the shortcomings of a constitutive model based on the Leverett concept. © 2002 Elsevier B.V. All rights reserved.

This interim report provides a description of the work done at Auburn University during the first year of the research project 'Subsurface Transport of Hydrocarbon Fuel Additives and a Chlorinated Solvent', supported by Armstrong Laboratory, Headquarters Air Force Civil Engineering Support Agency, Environics Directorate, under contract F08635-93-C-0071. The project is focused on the subsurface environmental behavior of quadricyclane, which is a light nonaqueous phase liquid (LNAPL) cyclic hydrocarbon fuel additive, and on the behavior of tetrachloroethylene (or, perchloroethylene), which is a dense nonaqueous phase liquid (DNAPL) chlorinated hydrocarbon solvent.

Most of the gas fields in The Netherlands are approaching the end of their production. Within two decades, the production in the majority of offshore gas fields will have ceased. The preparation of the fields for any end-of-field-life measures to extend their lifetime and increase production needs to start as soon as possible. One such measure is Enhanced Gas Recovery (EGR), which consists of injecting gas (CO2 or N2) to drive out the gas that remains after conventional production. This paper presents the results of a first study into the feasibility of EGR for two Dutch offshore fields. Injection scenarios (volumes, choice of injection wells, timing of the start of injection) were defined in close cooperation with the operators of these fields. The results suggest that the potential for EGR in these two fields is limited to about 1% of additional gas and condensate production. The highest recovery increases were obtained for EGR scenarios in which gas injection started after the end of regular production. The results strongly depend on the drive gas concentration limits in the produced gas, with higher tolerances leading to higher recoveries. Furthermore, detailed analysis of the EGR simulations suggest that some optimization of choice of injection wells, or even infill well placement, may lead to further increases. This will have to be further investigated. For the two cases considered, the additional gas production amounts to about 50% to 60% of the injected drive gas volume with little or no difference between the use of N2 or CO2. The amount of stored CO2 at end of life of the two studied fields is about 0.4 Mt. The rather modest increase in ultimate recovery may be too little to justify investment costs for most of the smaller fields, but may be economically interesting for some of the larger fields.

Depleted gas fields are seen as promising options for geological storage of CO2. The advantage of hydrocarbon fields are that the characteristics, such as the storage capacity and the proven sealing capacity are known. This means that only limited uncertainty remains after a technical feasibility study. One important issue with depleted gas reservoirs is the low pressure, at the onset of injection. This may lead to adiabatic cooling (Joule-Thomson cooling or JTC). The temperature reduction associated with this JTC can lead to hydrate formation and freezing of the residual pore water, especially the injected fluid also has a low temperature. In a related paper, we report on the development of a simulator, which is capable of predicting the fate of transport of a CO2 in either the liquid gaseous and supercritical phase. The model only contains CO2 besides the aqueous phase. One of the remaining challenges is to predict the impact of the methane, which is still present in a depleted gas reservoir, on the phase behavior of CO2 and the thermal aspects. In this study simulations were performed on the P18-4 depleted gas field. The CO2 was injected at a minimum temperature of 12 °C into the reservoir formation with a temperature of 120 °C. The average injection rate during the demonstration phase was modelled with 1.1 Mton/yr over a period of 5 year. The injection of cold CO2 into P18-4 was modelled in TOUGH2 and a new module, which can handle not only the behaviour of CO2 but also of CH4. The original ECO2M module was initially designed for CO2 behaviour in gas reservoir and aquifers for brine-CO2 mixtures, including all possible phase transitions, in the absence of any other gas. The new TOUGH2 module, which we gave the name ECO2MG module, was extended in such a way that compositional flow simulations of two different gases can be modelled, namely CO2 and CH4. The ECOMG module can not only model the behaviour brine CO2 mixtures but also the behaviour of brine-CO2-CH4 mixtures including phase changes from gas to liquid and from super- And sub-critical conditions. Density, viscosity and enthalpy of the CO2-CH4 mixture is based on NIST data. The new TOUGH2 module was used to model the thermal aspects of CO2 injection including the presence of brine and CH4 initially in the reservoir. The reservoir model was initialized with a brine-methane mixture at 20 bar, which is the expected abandonment pressure of the reservoir. The prediction of thermal effects of this new tool were compared with those of the earlier version (CO2 only) for several times during the projected 5 year injection period. The thermal effects investigated in this study were the JTC and also the effect of evaporation of the aqueous phase. The heat of evaporation of the brine is very significant and cools down the near well area significantly depending on the initial water saturation and the injection temperature of the CO2 itself. In the new module we saw that after the CO2 injection was started at first instance an uniform front of CO2/CH4 was formed. After a few years gravity underride of the still gaseous CO2 becomes visible, which became stronger after the phase transition to liquid CO2. A free CH4 phase moved during the simulation in front of the CO2 plume.

With the implementation of smart fields where sensors play a major role for measurement and control of the production process, continuous monitoring becomes increasingly important. In wells it is common practice to constantly monitor parameters like flow, pressure, and temperature. For imaging techniques like (active) seismics so far monitoring has only been applied in a time lapse manner with a repetition interval generally in the order of a year, not in a continuous way. The Vallhall field probably comes closest to continuous monitoring with permanently installed ocean bottom cables (OBC) and repeated surveys in the order of months. The main challenge with permanent seismic monitoring is not so much the technical feasibility, but more the data transfer and processing of the vast amounts of acquired data. TNO together with the TU-Delft, KNMI and ASTRON have started to implement a seismic monitoring network in the Netherlands using an ultra-fast digital optical fibre network linked to one of the most powerful computers in the world, the IBM BlueGene/L system. Data can be sent to this computer at speeds up to 20 Tera-bits/second. Currently passive seismic data is constantly acquired at Exloo, the first out of 50 test fields to be installed in the next year. Besides seismics, the network and the ICT infrastructure make it possible to combine all sorts of observations from the natural environment, infrastructure and processes anywhere and any time. This paper will give an overview of the first results of the incoming data and a description of the ICT infrastructure and network. Furthermore a view will be given on future applications.