An Investigation of Partitioning Tracers for Characterizing Geothermal Reservoirs and Predicting Enthalpy Production PDF Download
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Author: Xingru Wu
Publisher:
ISBN:
Category : Enthalpy
Languages : en
Pages : 304
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Book Description
A tracer selection protocol was developed after reviewing related literature of tracer applications and doing systematic simulations of tracer injection. An important conclusion is that for superheated geothermal reservoir, the partition coefficient (the K value) of the geothermal tracer should be high in order to get early information about reservoir characterization and liquid breakthrough.
Author: Xingru Wu
Publisher:
ISBN:
Category : Enthalpy
Languages : en
Pages : 304
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Book Description
A tracer selection protocol was developed after reviewing related literature of tracer applications and doing systematic simulations of tracer injection. An important conclusion is that for superheated geothermal reservoir, the partition coefficient (the K value) of the geothermal tracer should be high in order to get early information about reservoir characterization and liquid breakthrough.
Author: Younes Noorollahi
Publisher: Academic Press
ISBN: 0323908306
Category : Science
Languages : en
Pages : 484
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Book Description
Utilization of Thermal Potential of Abandoned Wells: Fundamentals, Applications and Research is a lucid treatment of the fundamental concepts related to the energy harvesting of abandoned wells. The book provides a journey through recent technological developments to harvest energy from abandoned geothermal wells and allows the reader to view the process from a thermodynamic and numerical modeling perspective. Various applications and future prospects are also discussed to help inform reader's future work and research. Students, researchers and engineers will gain a thorough understanding on how to harvest energy from abandoned geothermal wells, particularly to make sound thermodynamic and economic evaluations. System designers and others engaged in the energy sector will understand how to design and choose the most appropriate technology, how to determine its efficiency, monitor the facility, and how to make informed physical and economical decisions for necessary improvements and environmental assessments. - Logically works through fundamentals, with various examples throughout - Provides instruction to simulate thermodynamic models and design efficient systems - Presents feasibility studies and applications
Author: Morgan F. Ames
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
One of the most significant open problems in geothermal reservoir engineering is the development of a reliable and accurate method to predict thermal breakthrough. Such a method would enable more informed decisions to be made regarding reservoir management. Methods developed at present include analytical models and solute tracers, both of which have limitations. The use of particles as temperature-sensitive tracers is a promising approach due to the high degree of control of the physical and chemical properties of nanomaterials and micromaterials. Additionally, particles experience less matrix diffusion than solute tracers and tend to stay in high velocity fluid streamlines, which results in earlier particle breakthrough in the absence of significant particle deposition. These properties could potentially be exploited to infer temperature and measurement location, which could in turn provide useful information about thermal breakthrough. In order to assess whether particle tracers can provide more useful information about future thermal behavior of reservoirs than existing solute tracers, models were developed for both solute tracers and particle tracers. Three existing solute tracer types were modeled: conservative solute tracers (CSTs), reactive solute tracers with temperature-dependent reaction kinetics (RSTs), and sorbing solute tracers that sorb reversibly to fracture walls (SSTs). Additionally, three particle tracers which have not been developed in practice were modeled: dye-releasing tracers (DRTs) that release a solute dye at a specified temperature threshold, threshold nanoreactor tracers (TNRTs) with an encapsulated reaction that does not begin until a specified temperature threshold is reached, and temperature-time tracers (TTTs) capable of recording detailed temperature-time histories of each particle. In this study, TTTs represent the most informative tracer with respect to thermal breakthrough. These models were used in the context of an inverse problem in which synthetic tracer data were calculated for several "true" discrete fracture networks. Next, computational optimization was used to match these data by adjusting fracture location, length, and orientation for a variable number of fractures. Finally, the thermal behaviors of the fracture networks with the best fits to the data were compared to those of the true fracture networks, and the tracers were ranked according to their forecasting ability. Overall, thermal breakthrough forecast error was found to increase with fracture network complexity. However, in all cases, all tracers forecasted thermal breakthrough with unrealistic accuracy. This is partly due to neglecting thermal interference between closely spaced fractures in the thermal model. In all three cases, CSTs were found to be the least informative tracer type because they are insensitive to temperature. SSTs were also modeled as insensitive to temperature in this work, but they performed better than CSTs because sorption is sensitive to surface area, which is also closely related to a reservoir's thermal performance. In order to fully understand the relative informativity of these solute and particle tracers, a second study was performed using a uniform parallel fracture reservoir model that accounts for interference between fractures in both thermal and tracer transport. In this study, a seventh type of tracer test was also considered in which all three solute tracer types (CSTs, RSTs, and SSTs) were used simultaneously to gain the benefits of all three tracer types. This tracer type was designated ALLSOL, which is short for "all solutes." As with the discrete fracture network modeling study, synthetic data were generated and matched using optimization, after which thermal breakthrough forecasts were calculated. The decision variables used in optimization were the number of fractures and fracture length, width, aperture, and spacing. Two inverse problem scenarios with different fracture spacings were examined: 15 meter spacing and 5 meter spacing. In both scenarios, all individual solute tracers had significant error, particle tracers and ALLSOL forecasted thermal breakthrough more accurately than individual solute tracers, and ALLSOL had slightly more accurate forecasts than particle tracers. In the 15 meter spacing scenario, both RST and TNRT had very inaccurate forecasts because the temperature distribution is somewhat insensitive to fracture spacing at early time when fracture spacing is sufficiently large. This resulted in good matches and small objective function values for inaccurate estimates of fracture spacing. In order to determine if other tracers besides RST and TNRT are insensitive to spacing at early time when spacing is sufficiently large, the objective function values of all tracer types were evaluated using the optimal solution for TNRT in the 15 meter spacing scenario. Low objective function values and good fits to the data were observed for every tracer type except for TTT, indicating that TTT is the only tracer type considered that is capable of detecting differences in spacing at early time when the true fracture spacing is large. This is because the temperature is measured directly by the TTT rather than inferring the temperature from the return curve, as is the case for all other tracer types. In the 5 meter spacing case, the RST had a very inaccurate thermal breakthrough forecast because its return curve has a nonunique relationship with the temperature distribution (i.e. the RST return curve was matched by a reservoir with a significantly different temperature distribution from the true reservoir, which happened to result in the same amount of reaction). Forecast error was generally larger in the uniform parallel fracture modeling scenarios than in the discrete fracture network modeling scenarios. This demonstrates the importance of accounting for thermal interference in temperature-sensitive tracer modeling.
Author: Shyamal Karmakar
Publisher:
ISBN:
Category :
Languages : en
Pages : 132
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Book Description
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
The injection of cold fluids into engineered geothermal system (EGS) and conventional geothermal reservoirs may be done to help extract heat from the subsurface or to maintain pressures within the reservoir (e.g., Rose et al., 2001). As these injected fluids move along fractures, they acquire heat from the rock matrix and remove it from the reservoir as they are extracted to the surface. A consequence of such injection is the migration of a cold-fluid front through the reservoir (Figure 1) that could eventually reach the production well and result in the lowering of the temperature of the produced fluids (thermal breakthrough). Efficient operation of an EGS as well as conventional geothermal systems involving cold-fluid injection requires accurate and timely information about thermal depletion of the reservoir in response to operation. In particular, accurate predictions of the time to thermal breakthrough and subsequent rate of thermal drawdown are necessary for reservoir management, design of fracture stimulation and well drilling programs, and forecasting of economic return. A potential method for estimating migration of a cold front between an injection well and a production well is through application of reactive tracer tests, using chemical whose rate of degradation is dependent on the reservoir temperature between the two wells (e.g., Robinson 1985). With repeated tests, the rate of migration of the thermal front can be determined, and the time to thermal breakthrough calculated. While the basic theory behind the concept of thermal tracers has been understood for some time, effective application of the method has yet to be demonstrated. This report describes results of a study that used several methods to investigate application of reactive tracers to monitoring the thermal evolution of a geothermal reservoir. These methods included (1) mathematical investigation of the sensitivity of known and hypothetical reactive tracers, (2) laboratory testing of novel tracers that would improve method sensitivity, (3) development of a software tool for design and interpretation of reactive tracer tests and (4) field testing of the reactive tracer temperature monitoring concept.
Author:
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Category :
Languages : en
Pages :
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Book Description
Information about the times of thermal breakthrough and subsequent rates of thermal drawdown in enhanced geothermal systems (EGS) is necessary for reservoir management, designing fracture stimulation and well drilling programs, and forecasting economic return. Thermal breakthrough in heterogeneous porous media can be estimated using conservative tracers and assumptions about heat transfer rates; however, tracers that undergo temperature-dependent changes can provide more detailed information about the thermal profile along the flow path through the reservoir. To be effectively applied, the thermal reaction rates of such temperature sensitive traces must be well characterized for the range of conditions that exist in geothermal systems. Reactive tracers proposed in the literature include benzoic and carboxylic acids (Adams) and organic esters and amides (Robinson et al.); however, the practical temperature range over which these tracers can be applied (100-275°C) is somewhat limited. Further, for organic esters and amides, little is known about their sorption to the reservoir matrix and how such reactions impact data interpretation. Another approach involves tracers where the reference condition is internal to the tracer itself. Two examples are: 1) racemization of polymeric amino acids, and 2) mineral thermoluminescence. In these cases internal ratios of states are measured rather than extents of degradation and mass loss. Racemization of poly-L-lactic acid (for example) is temperature sensitive and therefore can be used as a temperature-recording tracer depending on the rates of racemization and stability of the amino acids. Heat-induced quenching of thermoluminescence of pre-irradiated LiF can also be used. To protect the tracers from alterations (extraneous reactions, dissolution) in geothermal environments we are encapsulating the tracers in core-shell colloidal structures that will subsequently be tested for their ability to be transported and to protect the tracers from incidental reactions. We review the criteria for practical reactive tracers, which serves as the basis for experimental testing and characterization and can be used to identify other potential candidate tracers. We will also discuss the information obtainable from individual tracers, which has implications for using multiple tracers to obtain information about the thermal history of a reservoir. We will provide an update on our progress for conducting proof-of-principle tests for reactive tracers in the Raft River geothermal system.
Author: Alejandro García Gil
Publisher: Springer Nature
ISBN: 3030922588
Category : Science
Languages : en
Pages : 362
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Book Description
This book is the outcome of more than a decade of research and technical development activities at Spain’s Geological Survey (IGME) concerning shallow geothermal energy, which were pursued in collaboration with other public bodies and European entities. It presents a compilation of papers on the theoretical foundations of, and practical aspects needed to understand the thermal regime of the topmost subsoil, up to 400 m deep, and the exceptional properties that this underground environment offers, which make it the ideal thermal reservoir for heating, ventilation, and air conditioning (HVAC). In the book’s first section, the basic theory of thermodynamics as applied to shallow geothermal energy, heat transfer and fluid mechanics in the geological porous medium is developed. The nature of the subsoil’s thermal regime in general and in the urban environment in particular is described. The second section introduces readers to the fundamental aspects of thermal installations equipped with geothermal heat pumps, describes the types of geothermal exchangers most commonly used, and reviews the techniques used to obtain the thermal parameters of the terrain. It also discusses the potential environmental impacts of shallow geothermal activity and corresponding management strategies, as well as the legal aspects of its regulation for the governance of shallow geothermal resources in the EU in general and Spain in particular. In closing, the book highlights examples of the methodologies’ applications, developed by IGME in the city of Zaragoza and the Canary Islands. The theoretical foundations, systematics and concrete applications make the book a valuable reference source for hydrogeologists, engineers and specialized technicians alike.
Author:
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Category :
Languages : en
Pages :
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The theory behind how chemically reactive tracers are used to characterize the velocity and temperature distribution in steady flowing systems is reviewed. Ranges of kinetic parameters are established as a function of reservoir temperatures and fluid residence times for selecting appropriate reacting systems. Reactive tracer techniques are applied to characterize the temperature distribution in a laminar-flow heat exchanger. Models are developed to predict reactive tracer behavior in fractured geothermal reservoirs of fixed and increasing size. 5 figs., 11 refs.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 72
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The prediction of the geothermal system efficiency is strong linked to the character of the flow system that connects injector and producer wells. If water flow develops channels or "short circuiting" between injection and extraction wells thermal sweep is poor and much of the reservoir is left untapped. The purpose of this project was to understand how channelized flow develops in fracture geothermal reservoirs and how it can be measured in the field. We explored two methods of assessing channelization: hydraulic connectivity tests and tracer tests. These methods were tested at a field site using two verification methods: ground penetrating radar (GPR) images of saline tracer and heat transfer measurements using distributed temperature sensing (DTS). The field site for these studies was the Altona Flat Fractured Rock Research Site located in northeastern New York State. Altona Flat Rock is an experimental site considered a geologic analog for some geothermal reservoirs given its low matrix porosity. Because soil overburden is thin, it provided unique access to saturated bedrock fractures and the ability image using GPR which does not effectively penetrate most soils. Five boreholes were drilled in a "five spot" pattern covering 100 m2 and hydraulically isolated in a single bedding plane fracture. This simple system allowed a complete characterization of the fracture. Nine small diameter boreholes were drilled from the surface to just above the fracture to allow the measurement of heat transfer between the fracture and the rock matrix. The focus of the hydraulic investigation was periodic hydraulic testing. In such tests, rather than pumping or injection in a well at a constant rate, flow is varied to produce an oscillating pressure signal. This pressure signal is sensed in other wells and the attenuation and phase lag between the source and receptor is an indication of hydraulic connection. We found that these tests were much more effective than constant pumping tests in identifying a poorly connected well. As a result, we were able to predict which well pairs would demonstrate channelized flow. The focus of the tracer investigation was multi-ionic tests. In multi-ionic tests several ionic tracers are injected simultaneously and the detected in a nearby pumping well. The time history of concentration, or breakthrough curve, will show a separation of the tracers. Anionic tracers travel with the water but cationic tracer undergo chemical exchange with cations on the surface of the rock. The degree of separation is indicative of the surface area exposed to the tracer. Consequently, flow channelization will tend to decrease the separation in the breakthrough. Estimation of specific surface area (the ration of fracture surface area to formation volume) is performed through matching the breakthrough curve with a transport model. We found that the tracer estimates of surface area were confirmed the prediction of channelized flow between well pairs produced by the periodic hydraulic tests. To confirm that the hydraulic and tracer tests were correctly predicting channelize flow, we imaged the flow field using surface GPR. Saline water was injected between the well pairs which produced a change in the amplitude and phase of the reflected radar signal. A map was produced of the migration of saline tracer from these tests which qualitatively confirmed the flow channelization predicted by the hydraulic and tracer tests. The resolution of the GPR was insufficient to quantitatively estimate swept surface area, however. Surface GPR is not applicable in typical geothermal fields because the penetration depths do not exceed 10's of meters. Nevertheless, the method of using of phase to measure electrical conductivity and the assessment of antennae polarization represent a significant advancement in the field of surface GPR. The effect of flow character on fracture / rock thermal exchange was evaluated using heated water as a tracer. Water el ...
Author: Yuran Zhang
Publisher:
ISBN:
Category :
Languages : en
Pages :
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A thorough understanding of the subsurface fracture network is crucial for the effective exploitation and management of geothermal energy, unconventional hydrocarbon resources, groundwater reservoirs, etc. While conventional tracer technology is a useful tool to characterize the complex network of flowpaths in geologic reservoirs, tracers are limited in unique variations and hence insufficient for characterizing reservoirs with a large number of wells. In addition, conventional tracer testing only provides a "snapshot" of the flowpath properties which may be inadequate for reservoirs that are subjected to changes. This research sought to resolve the limitations of conventional tracer testing by exploring novel, DNA-based tracer candidates. DNA's infinite number of unique sequences and hence great degree of specificity makes it a promising tracer candidate for improved subsurface characterization. We first investigated the use of uniquely designed, synthetic DNA fragments as injected tracers. The method to measure target-specific DNA tracer concentration is described. The effect of DNA sequence, fragment length and porous medium on DNA transport was studied to provide guidance to potential field applications and data interpretation. It was found that DNA transport was not affected by DNA sequence (i.e. the arrangement of nucleotides). The length of DNA fragments does not affect the shape of the tracer return curve, but does affect tracer mass recovery. Shorter DNA appeared to be more prone to adsorption, while longer DNA appeared to be more prone to size exclusion effect. We then extended the concept of DNA-based tracers towards the genomic DNA of fluid-associated microorganisms that naturally colonize a geologic reservoir. Instead of targeting just a few microbes, we proposed taking advantage of the entire microbial community population in a reservoir fluid sample as unique signatures pinpointing the origins of fluids. We tested this method at a mesoscale enhanced geothermal system (EGS) testbed at Sanford Underground Research Facility (SURF) by sampling indigenous fluids produced from separate fractures and analyzing their microbial community structure via high-throughput 16S rRNA gene amplicon sequencing. We found that hydraulically isolated fractures at our field site hosted distinct microbial community populations, demonstrating substantial microbial heterogeneity across fractures. However, locally within a fracture, the microbial community were relatively homogenized, serving as a unique natural tracer or "fingerprint" of the fracture. We demonstrated at our field site that sampling indigenous fluids from an undisturbed, newly developed reservoir could help us identify natural interwell connectivity when more than one well were drilled into the same natural fracture. Finally, building upon the idea of reservoir indigenous microbial populations as natural tracers, we investigated the potential of this novel data source in an actively circulating, dynamic reservoir. Again using the EGS testbed at SURF, we sampled the produced fluids from the reservoir that underwent long-term flow circulation. Sampling was conducted regularly in a 5-month time series and the microbial populations in the fluids were sequenced. We found that although the whole circulating reservoir were connected hydraulically, the difference in relative connectivity among fractures still allowed different flowing fractures to have different microbial community signatures. The long-term microbial monitoring at our site identified the switch of production zone of a borehole likely due to major changes in the fracture network. Changes in fracture network were also observed from microbial time-series data after a week-long injection halt, likely due to the reopened hydraulic fracture not restoring to its initial state. We thereby demonstrated that long-term microbial community monitoring in an active reservoir may effectively enable the direct observation of fracture network evolution. Such information is difficult to achieve via other reservoir diagnostic methods.
