Temperature Sensitive Tracers For Fractured Geothermal Reservoir Characterization
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Temperature Sensitive Tracers For Fractured Geothermal Reservoir Characterization
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Author : Morgan F. Ames
language : en
Publisher:
Release Date : 2016
Temperature Sensitive Tracers For Fractured Geothermal Reservoir Characterization written by Morgan F. Ames and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016 with categories.
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.
An Investigation Of Partitioning Tracers For Characterizing Geothermal Reservoirs And Predicting Enthalpy Production
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Author : Xingru Wu
language : en
Publisher:
Release Date : 2006
An Investigation Of Partitioning Tracers For Characterizing Geothermal Reservoirs And Predicting Enthalpy Production written by Xingru Wu and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2006 with Enthalpy categories.
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.
Tracers For Characterizing Enhanced Geothermal Systems
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Author :
language : en
Publisher:
Release Date : 2010
Tracers For Characterizing Enhanced Geothermal Systems written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010 with categories.
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.
Analysis Of Injection Backflow Tracer Tests In Fractured Geothermal Reservoirs
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Author :
language : en
Publisher:
Release Date : 1987
Analysis Of Injection Backflow Tracer Tests In Fractured Geothermal Reservoirs written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1987 with categories.
Tracer tests have been an important technique for determining the flow and reservoir characteristics in various rock matrix systems. While the interwell tracer tests are aimed at the characterization of the regions between the wells, single-well injection-backflow tracer tests may be useful tools of preliminary evaluation, before implementing long term interwell tracer tests. This work is concerned with the quantitative evaluation of the tracer return profiles obtained from single well injection-backflow tracer tests. First, two mathematical models of tracer transport through fractures, have been reviewed. These two models are based on two different principles: Taylor Dispersion along the fracture and simultaneous diffusion in and out of the adjacent matrix. Then the governing equations for the transport during the injection-backflow tests have been solved. Finally the results were applied to field data obtained from Raft River and East Mesa geothermal fields. In order to determine the values of the parameters of the models that define the transport mechanisms through fractures a non-linear optimization technique was employed. 26 refs., 10 figs.
Characterization Of Fractured Geothermal Reservoirs Based On Production Data
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Author : Egill Júlíusson
language : en
Publisher:
Release Date : 2012
Characterization Of Fractured Geothermal Reservoirs Based On Production Data written by Egill Júlíusson and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012 with categories.
Reservoir characterization is one of the most important and challenging parts of running a successful geothermal operation. Characterization requires thorough understanding of the physics that govern the flow of mass and energy through the reservoir. As for most subsurface modeling endeavors, the inability to measure the actual value of properties in the geothermal system make it necessary to strike a balance between what is included in the reservoir model and what is known about the physical processes that might take place in the subsurface. This balance should reflect the decisions that need to be made based on the model, and the data available for model calibration. In this work, a number of methods were developed for characterizing well-to-well connections in fractured geothermal reservoirs. These methods were based on production data that are commonly recorded in geothermal fields, i.e. pressure, flow rate, tracer and temperature. A key aspect in the developing this work, for multiwell applications, was to find the link between the various types of models, and understand how they could be combined to estimate well-to-well properties. The estimation of these properties relied on regression analysis, where an effort was made to balance the complexity of the regression model with the information required from the given data source. The combined characterization defined a work flow that would be well-suited to characterize fractured geothermal systems, with low compressibility characteristics. An effort was made to illustrate the usefulness of the characterization method to tackle important reservoir engineering problems. This was done by formulating and solving a flow rate scheduling problem for a geothermal field. The results showed that considerable gains in efficiency could be made, given a set of well-calibrated interwell relationships.
Tracer Analysis In A Fractured Geothermal Reservoir Field Results From Wairakei New Zealand
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Author : Martin Peter Fossum
language : en
Publisher:
Release Date : 1982
Tracer Analysis In A Fractured Geothermal Reservoir Field Results From Wairakei New Zealand written by Martin Peter Fossum and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1982 with categories.
Tracking Thermal Fronts With Temperature Sensitive Chemically Reactive Tracers
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Author :
language : en
Publisher:
Release Date : 1987
Tracking Thermal Fronts With Temperature Sensitive Chemically Reactive Tracers written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1987 with categories.
Los Alamos is developing tracer techniques using reactive chemicals to track thermal fronts in fractured geothermal reservoirs. If a nonadsorbing tracer flowing from the injection to production well chemically reacts, its reaction rate will be a strong function of temperature. Thus the extent of chemical reaction will be greatest early in the lifetime of the system, and less as the thermal front progresses from the injection to production well. Early laboratory experiments identified tracers with chemical kinetics suitable for reservoirs in the temperature range of 75 to 100°C. Recent kinetics studies have focused on the kinetics of hydrolysis of derivatives of bromobenzene. This class of reactions can be used in reservoirs ranging in temperature from 150 to 275°C, which is of greater interest to the geothermal industry. Future studies will include laboratory adsorption experiments to identify possibly unwanted adsorption on granite, development of sensitive analytical techniques, and a field demonstration of the reactive tracer concept.
Using Chemically Reactive Tracers To Determine Temperature Characteristics Of Geothermal Reservoirs
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Author :
language : en
Publisher:
Release Date : 1984
Using Chemically Reactive Tracers To Determine Temperature Characteristics Of Geothermal Reservoirs written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1984 with categories.
The rates of most chemical reactions are very sensitive to temperature, and this property can be used to measure temperature patterns in geothermal reservoirs. Two approaches are considered: reverse-flush and flow-through. Both of these can indicate thermal drawdown faster than the measurement of produced-fluid temperature. The reverse-flush approach is more difficult to carry out and interferes more with normal operation, but it gives the earlier indication of thermal drawdown and yields more information when using a single reaction. In both approaches, injecting a suite of reactants can yield bivariate time-temperature distributions which give temperature distributions as functions of fluid residence time. Applications to Hot Dry Rock systems are considered throughout the paper. Results of early kinetics studies of candidate tracer reactions also are reported.
Tracking Thermal Fronts With Temperature Sensitive Chemically Reactive Tracers
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Author : Bruce A. Robinson
language : en
Publisher:
Release Date : 1987
Tracking Thermal Fronts With Temperature Sensitive Chemically Reactive Tracers written by Bruce A. Robinson and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1987 with Geothermal reservoirs categories.
The Theory And Selection Of Chemically Reactive Tracers For Reservoir Thermal Capacity Production
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Author :
language : en
Publisher:
Release Date : 1987
The Theory And Selection Of Chemically Reactive Tracers For Reservoir Thermal Capacity Production written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1987 with categories.
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.