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Fracture Characterization In Geothermal Reservoirs Using Time Lapse Electric Potential Data
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Book Synopsis Fracture Characterization in Geothermal Reservoirs Using Time-lapse Electric Potential Data by : Lilja Magnúsdóttir
Download or read book Fracture Characterization in Geothermal Reservoirs Using Time-lapse Electric Potential Data written by Lilja Magnúsdóttir and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The configuration of fractures in a geothermal reservoir is central to the performance of the system. The interconnected fractures control the heat and mass transport in the reservoir and if the fluid reaches production wells before it is fully heated, unfavorable effects on energy production may result due to decreasing fluid enthalpies. Consequently, inappropriate placing of injection or production wells can lead to premature thermal breakthrough. Thus, fracture characterization in geothermal reservoirs is an important task in order to design the recovery strategy appropriately and increase the overall efficiency of the power production. This is true both in naturally fractured geothermal systems as well as in Enhanced Geothermal Systems (EGS) with man-made fractures produced by hydraulic stimulation. In this study, the aim was to estimate fracture connectivity in geothermal reservoirs using a conductive fluid injection and an inversion of time-lapse electric potential data. Discrete fracture networks were modeled and a flow simulator was used first to simulate the flow of a conductive tracer through the reservoirs. Then, the simulator was applied to solve the electric fields at each time step by utilizing the analogy between Ohm's law and Darcy's law. The electric potential difference between well-pairs drops as a conductive fluid fills fracture paths from the injector towards the producer. Therefore, the time-lapse electric potential data can be representative of the connectivity of the fracture network. Flow and electric simulations were performed on models of various fracture networks and inverse modeling was used to match reservoir models to other fracture networks in a library of networks by comparing the time-histories of the electric potential. Two fracture characterization indices were investigated for describing the character of the fractured reservoirs; the fractional connected area and the spatial fractal dimension. In most cases, the electrical potential approach was used successfully to estimate both the fractional connected area of the reservoirs and the spatial fractal dimension. The locations of the linked fracture sets were also predicted correctly. Next, the electric method was compared to using only the simple tracer return curves at the producers in the inverse analysis. The study showed that the fracture characterization indices were estimated somewhat better using the electric approach. The locations of connected areas in the predicted network were also in many cases incorrect when only the tracer return curves were used. The use of the electric approach to predict thermal return was investigated and compared to using just the simple tracer return curves. The electric approach predicted the thermal return curves relatively accurately. However, in some cases the tracer return gave a better estimation of the thermal behavior. The electric measurements are affected by both the time it takes for the conductive tracer to reach the production well, as well as the overall location of the connected areas. When only the tracer return curves are used in the inverse analysis, only the concentration of tracer at the producer is measured but there is a good correlation between the tracer breakthrough time and the thermal breakthrough times. Thus, the tracer return curves can predict the thermal return accurately but the overall location of fractures might not be predicted correctly. The electric data and the tracer return data were also used together in an inverse analysis to predict the thermal returns. The results were in some cases somewhat better than using only the tracer return curves or only the electric data. A different injection scheme was also tested for both approaches. The electric data characterized the overall fracture network better than the tracer return curves so when the well pattern was changed from what was used during the tracer and electric measurements, the electric approach predicted the new thermal return better. In addition, the thermal return was predicted considerably better using the electric approach when measurements over a shorter period of time were used in the inverse analysis. In addition to characterizing the fracture distribution better, the electric approach can give information about the conductive fluid flowing through the fracture network even before it has reached the production wells.
Book Synopsis Fracture Characterization in Enhanced Geothermal Systems by Wellbore and Reservoir Analysis by :
Download or read book Fracture Characterization in Enhanced Geothermal Systems by Wellbore and Reservoir Analysis written by and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This report highlights the work that was done to characterize fractured geothermal reservoirs using production data. That includes methods that were developed to infer characteristic functions from production data and models that were designed to optimize reinjection scheduling into geothermal reservoirs, based on these characteristic functions. The characterization method provides a robust way of interpreting tracer and flow rate data from fractured reservoirs. The flow-rate data are used to infer the interwell connectivity, which describes how injected fluids are divided between producers in the reservoir. The tracer data are used to find the tracer kernel for each injector-producer connection. The tracer kernel describes the volume and dispersive properties of the interwell flow path. A combination of parametric and nonparametric regression methods were developed to estimate the tracer kernels for situations where data is collected at variable flow-rate or variable injected concentration conditions. The characteristic functions can be used to calibrate thermal transport models, which can in turn be used to predict the productivity of geothermal systems. This predictive model can be used to optimize injection scheduling in a geothermal reservoir, as is illustrated in this report.
Book Synopsis Anisotropic Elastic-Waveform Modeling for Fracture Characterization in EGS Reservoirs by :
Download or read book Anisotropic Elastic-Waveform Modeling for Fracture Characterization in EGS Reservoirs written by and published by . This book was released on 2015 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: Enhanced geothermal systems (EGS) contain newly created fractures in addition to possible existing fractures. Accurate characterization and monitoring of EGS reservoirs are crucial for optimal placement of new wells and effective extraction of geothermal heat. The fractured reservoirs behave as anisotropic media where seismic waves propagate with different velocities along different directions. In addition, the anisotropic properties of fluid-filled fracture zones could be different from those of dry fracture zones. We develop an optimized rotated staggered-grid elastic-wave finite-difference method for simulating seismic-wave propagation in heterogeneous, anisotropic media. Our new method uses a few extra grid points and optimized finite-difference coefficients based on the space-time dispersion relation, and reduce numerical dispersion of the conventional rotated staggered-grid finite-difference scheme. We validate our new method using synthetic vertical-seismic-profiling (VSP) data for an anisotropic geophysical model built with geologic features found at the Raft River EGS reservoir. This improved and optimized rotated staggered-grid finite-difference method provides an essential tool for analyzing VSP data, reverse-time migration, and elastic-waveform inversion in anisotropic, fractured reservoirs.
Book Synopsis Detection and Characterization of Natural and Induced Fractures for the Development of Enhanced Geothermal Systems by :
Download or read book Detection and Characterization of Natural and Induced Fractures for the Development of Enhanced Geothermal Systems written by and published by . This book was released on 2013 with total page 35 pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of this 3-year project is to use various geophysical methods for reservoir and fracture characterization. The targeted field is the Cove Fort-Sulphurdale Geothermal Field in Utah operated by ENEL North America (ENA). Our effort has been focused on 1) understanding the regional and local geological settings around the geothermal field; 2) collecting and assembling various geophysical data sets including heat flow, gravity, magnetotelluric (MT) and seismic surface and body wave data; 3) installing the local temporary seismic network around the geothermal site; 4) imaging the regional and local seismic velocity structure around the geothermal field using seismic travel time tomography; and (5) determining the fracture direction using the shear-wave splitting analysis and focal mechanism analysis. Various geophysical data sets indicate that beneath the Cove Fort-Sulphurdale Geothermal Field, there is a strong anomaly of low seismic velocity, low gravity, high heat flow and high electrical conductivity. These suggest that there is a heat source in the crust beneath the geothermal field. The high-temperature body is on average 150 °C - 200 °C hotter than the surrounding rock. The local seismic velocity and attenuation tomography gives a detailed velocity and attenuation model around the geothermal site, which shows that the major geothermal development target is a high velocity body near surface, composed mainly of monzonite. The major fracture direction points to NNE. The detailed velocity model along with the fracture direction will be helpful for guiding the geothermal development in the Cove Fort area.
Book Synopsis Real-time and Post-frac' 3-D Analysis of Hydraulic Fracture Treatments in Geothermal Reservoirs by :
Download or read book Real-time and Post-frac' 3-D Analysis of Hydraulic Fracture Treatments in Geothermal Reservoirs written by and published by . This book was released on 1994 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Economic power production from Hot Dry Rock (HDR) requires the establishment of an efficient circulation system between wellbores in reservoir rock with extremely low matrix permeability. Hydraulic fracturing is employed to establish the necessary circulation system. Hydraulic fracturing has also been performed to increase production from hydrothermal reservoirs by enhancing the communication with the reservoir's natural fracture system. Optimal implementation of these hydraulic fracturing applications, as with any engineering application, requires the use of credible physical models and the reconciliation of the physical models with treatment data gathered in the field. Analysis of the collected data has shown that 2-D models and 'conventional' 3-D models of the hydraulic fracturing process apply very poorly to hydraulic fracturing in geothermal reservoirs. Engineering decisions based on these more 'conventional' fracture modeling techniques lead to serious errors in predicting the performance of hydraulic fracture treatments. These errors can lead to inappropriate fracture treatment design as well as grave errors in well placement for hydrothermal reservoirs or HDR reservoirs. This paper outlines the reasons why conventional modeling approaches fall short, and what types of physical models are needed to credibly estimate created hydraulic fracture geometry. The methodology of analyzing actual measured fracture treatment data and matching the observed net fracturing pressure (in realtime as well as after the treatment) is demonstrated at two separate field sites. Results from an extensive Acoustic Emission (AE) fracture diagnostic survey are also presented for the first case study aS an independent measure of the actual created hydraulic fracture geometry.
Book Synopsis Fracture Characterization from Seismic Measurements in a Borehole by : Sudhish Kumar Bakku
Download or read book Fracture Characterization from Seismic Measurements in a Borehole written by Sudhish Kumar Bakku and published by . This book was released on 2015 with total page 227 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fracture characterization is important for optimal recovery of hydrocarbons. In this thesis, we develop techniques to characterize natural and hydraulic fractures using seismic measurements in a borehole. We first develop methods to characterize a fracture intersecting an open borehole by studying tubewave generation and attenuation at the fracture. By numerically studying the dispersion relation for fluid pressure in the fracture, we show that the tubewave measurements made in the transition regime from low to high frequency can constrain fracture compliance, aperture and length, while measurements made in the high-frequency regime can place a lower bound on fracture compliance. Analysis of field data suggest a large compliance value (10- 0m/Pa) for a meter-scale fracture and supports scaling of fracture compliance and applicability of scattering based methods for fracture characterization on a reservoir scale. We next study Distributed Acoustic Sensing (DAS), a novel Fiber Optic (FO) cable based seismic acquisition technology. We relate DAS measurements to traditional geophone measurements and make a comprehensive study of factors that influence DAS measurements. Using a layered borehole model, we analytically compare the sensitivity of DAS measurements to P- and S-wave incidence at arbitrary angles for the cases when the FO cable is installed in the borehole fluid or when cemented outside the casing. In addition, we study the azimuthal placement of the cable, the effect of cable design, and the effect of environmental conditions on time-lapse measurements. We show that DAS is a reliable tool for time-lapse monitoring. Finally, we analyze time-lapse DAS Vertical Seismic Profiling (VSP) data collected during a multi-stage hydraulic fracture treatment of a well drilled into a tight gas sandstone reservoir. We develop a processing workflow to mitigate the unique challenges posed by DAS data and propose methods for DAS depth calibration. We observe systematic and long-lived (over 10 days) time-lapse changes in the amplitudes of direct P-waves and nearly no phase changes due to stimulation. We argue that the time-lapse changes cannot be explained by measurement factors alone and that they may be correlated to the stimulated volume. Though the current geometry is not ideal, DAS is promising for hydraulic fracture monitoring.
Book Synopsis Emerging Advances in Petrophysics by : Jianchao Cai
Download or read book Emerging Advances in Petrophysics written by Jianchao Cai and published by MDPI. This book was released on 2019-04-18 with total page 258 pages. Available in PDF, EPUB and Kindle. Book excerpt: Due to the influence of pore-throat size distribution, pore connectivity, and microscale fractures, the transport, distribution, and residual saturation of fluids in porous media are difficult to characterize. Petrophysical methods in natural porous media have attracted great attention in a variety of fields, especially in the oil and gas industry. A wide range of research studies have been conducted on the characterization of porous media covers and multiphase flow therein. Reliable approaches for characterizing microstructure and multiphase flow in porous media are crucial in many fields, including the characterization of residual water or oil in hydrocarbon reservoirs and the long-term storage of supercritical CO2 in geological formations. This book gathers together 15 recent works to emphasize fundamental innovations in the field and novel applications of petrophysics in unconventional reservoirs, including experimental studies, numerical modeling (fractal approach), and multiphase flow modeling/simulations. The relevant stakeholders of this book are authorities and service companies working in the petroleum, subsurface water resources, air and water pollution, environmental, and biomaterial sectors.
Book Synopsis Fractal Characterization of Subsurface Fracture Network for Geothermal Energy Extraction System by :
Download or read book Fractal Characterization of Subsurface Fracture Network for Geothermal Energy Extraction System written by and published by . This book was released on 1993 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: As a new modeling procedure of geothermal energy extraction systems, the authors present two dimensional and three dimensional modeling techniques of subsurface fracture network, based on fractal geometry. Fluid flow in fractured rock occurs primarily through a connected network of discrete fractures. The fracture network approach, therefore, seeks to model fluid flow and heat transfer through such rocks directly. Recent geophysical investigations have revealed that subsurface fracture networks can be described by "fractal geometry". In this paper, a modeling procedure of subsurface fracture network is proposed based on fractal geometry. Models of fracture networks are generated by distributing fractures randomly, following the fractal relation between fracture length r and the number of fractures N expressed with fractal dimension D as N =C·r-D, where C is a constant to signify the fracture density of the rock mass. This procedure makes it possible to characterize geothermal reservoirs by the parameters measured from field data, such as core sampling. In this characterization, the fractal dimension D and the fracture density parameter C of a geothermal reservoir are used as parameters to model the subsurface fracture network. Using this model, the transmissivities between boreholes are also obtained as a function of the fracture density parameter C, and a parameter study of system performances, such as heat extraction, is performed. The results show the dependence of thermal recovery of geothermal reservoir on fracture density parameter C.
Book Synopsis Geophysical Characterization of the Effects of Fractures and Stress on Subsurface Reservoirs by : Xinding Fang (Ph. D.)
Download or read book Geophysical Characterization of the Effects of Fractures and Stress on Subsurface Reservoirs written by Xinding Fang (Ph. D.) and published by . This book was released on 2013 with total page 271 pages. Available in PDF, EPUB and Kindle. Book excerpt: We study the effect of fractures on reservoir characterization and subsurface rock property measurements using seismic data. Based on the scale of a fracture relative to seismic wavelength, we divide the dissertation into two parts: larger scale fractures and microcracks. In the first part, we study the sensitivity of seismic waves and their time-lapse changes in hydraulic fracturing to the geometrical and mechanical properties of fractures that have dimensions comparable to the seismic wavelength. Through our analysis, we give the general seismic response of a fracture with a linear slip boundary and introduce the fracture sensitivity wave equation for optimal time-lapse survey design. Based on the characteristics of scattering from fractures, we develop an approach to determine the fracture properties using scattered seismic waves. The applicability and accuracy of our method is validated through both numerical simulations and laboratory experiments. Application of our approach to the Emilio Field shows that two orthogonal fracture systems exist and the field data results are consistent with well data. In the second part, we study the effects of microcracks and in situ stress on the formation properties measured from borehole sonic logging. Formation property measurements in a borehole could be biased by the borehole stress concentration, which alters the near wellbore formation properties from their original state. To study this problem, we first develop an iterative approach, which combines a rock physics model and a finite-element method, to calculate the stress-dependent elastic properties of the rock around a borehole when it is subjected to an anisotropic stress loading. The validity of this approach is demonstrated through a laboratory experiment on a Berea sandstone sample. We then use the model obtained from the first step and a finite-difference method to simulate the acoustic response in a borehole. We compare our numerical results with published laboratory acoustic wave measurements of the azimuthal velocity variations along a borehole under uniaxial loading and find very good agreement. Our results show that the variation of P-wave velocity versus azimuth is different from the presumed cosine behavior due to the preference of the wavefield to propagate through a higher velocity region.
Book Synopsis Thermal Modeling of Fractured Reservoir-wellbore Coupled System for Fracture Diagnosis and Geothermal Applications by : He Sun (Ph. D.)
Download or read book Thermal Modeling of Fractured Reservoir-wellbore Coupled System for Fracture Diagnosis and Geothermal Applications written by He Sun (Ph. D.) and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Distributed temperature sensing (DTS) is an enabling technology for fracture diagnosis and multiphase flow measurement in unconventional areas. Fracture characterization and flow profiling are crucial to evaluate the performance of hydraulic fractures. Enhanced Geothermal Systems (EGS) have gained great attention since they promise to deliver geographically disperse, carbon-free energy with minimal environmental impact. The objective of our DTS data analysis workflow is to provide a high-resolution quantitative diagnosis of hydraulic and natural fractures, which will benefit the fracturing operation design and decision-making process in the unconventional reservoir. Natural fracture networks have a major impact on EGS heat extraction. The objective of our model is to evaluate the impact of natural fracture networks on EGS producing temperature profiles. In this work, we developed a comprehensive numerical forward model for DTS data analysis and EGS economic evaluation. Our model includes reservoir and wellbore models. Also, the flow and thermal models are fully coupled. A thermal embedded discrete fracture model (Thermal EDFM) is developed to handle the thermal modeling of complex fracture networks. Subsequently, we implemented an ensemble smoother with multiple data assimilation (ESMDA) as the inverse model to match DTS data and characterize fractures. The DTS analysis with our model provides a high-resolution solution since the fracture diagnosis and flow profiling are performed for each fracture. The hydraulic and natural fracture properties and geometry such as fracture half-length, height, and fracture conductivity are evaluated. Our EGS model provides a comprehensive economic evaluation since we consider the flow and temperature behavior in each fracture without any upscaling. Although numerous simulators are developed for DTS data analysis and EGS economic evaluation, relatively few existing models can handle the full-physics such as complex fracture geometry and multiphase flow. Our models are more rigorous than the prior models to simulate and match the field DTS and EGS data
Book Synopsis Fractures in Geothermal Reservoirs by : Geothermal Resources Council
Download or read book Fractures in Geothermal Reservoirs written by Geothermal Resources Council and published by . This book was released on 1982 with total page 352 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Joint Inversion of Electrical and Seismic Data for Fracture Characterization and Imaging of Fluid Flow in Geothermal Systems by :
Download or read book Joint Inversion of Electrical and Seismic Data for Fracture Characterization and Imaging of Fluid Flow in Geothermal Systems written by and published by . This book was released on 2012 with total page 127 pages. Available in PDF, EPUB and Kindle. Book excerpt: Joint inversion of electrical and seismic data for Fracture characterization and Imaging of Fluid Flow in Geothermal Systems.
Book Synopsis Hydraulic fracture geometry characterization based on distributed fiber optic strain measurements by : Kan Wu
Download or read book Hydraulic fracture geometry characterization based on distributed fiber optic strain measurements written by Kan Wu and published by Elsevier. This book was released on 2024-08-01 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Distributed fiber optic strain measurements, revolutionizing subsurface monitoring and hydraulic fracture characterization, offers a pivotal resource for geophysicists, reservoir engineers, and completion engineers. This cutting-edge technology leads the way in innovation with its ability to detect rock deformation and changes in strain along optical fibers, providing exceptional spatial resolution and measurement sensitivity. Its applications are broad and impactful, ranging from monitoring subsurface carbon storage and enhancing geothermal systems to advancing unconventional reservoir development. Despite the technology's advancements, accurately interpreting data of strain measurement from the hydraulic fracturing process poses a significant challenge due to the complex conditions in the Earth's surface. This book presents a comprehensive approach for analyzing strain responses from both horizontal and vertical monitoring wells to quantify hydraulic fracture propagation and the evolution of fracture geometry. The development of a forward geomechanics model significantly enhance the understanding of the field data. The introduction of a groundbreaking inversion model allows for in-depth data analysis and maximizes the dataset's value. Moreover, this book applies its findings through two field studies in typical unconventional reservoirs, illustrating the practical application of the technology. These case studies highlight effective field data interpretation and the critical insights that can be obtained. This book aims to elucidate data interpretation and analysis of complex subsurface measurements related to hydraulic fracture propagation, providing engineers with a novel perspective on subsurface exploration.
Book Synopsis Quantitative Data Integration for Fracture Characterization Using Statistical Rock Physics by : Diana Sava
Download or read book Quantitative Data Integration for Fracture Characterization Using Statistical Rock Physics written by Diana Sava and published by . This book was released on 2004 with total page 406 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Characterization of Fracture Patterns in the Geysers Geothermal Field by :
Download or read book Characterization of Fracture Patterns in the Geysers Geothermal Field written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: On the basis of shear wave splitting data recorded and processed from the Geysers and Coso geothermal fields, this project aims at developing a computer-based methodology to produce 3D maps of crack distribution, crack geometry, as well as crack density in fractured reservoirs. Such maps are crucial in identifying zones of high permeability in reservoirs as well as in determining fluid flow directions. The raw data for the project consists of seismographic recordings of microearthquakes (MEQ) detected over many years by arrays of sensors at both The Geysers and Coso reservoirs. With the experience acquired in the processing and interpretation of these data, we are developing a novel computer-based technology for the exploration of fractured reservoirs, which consists of the following software packages (three modules written in Matlab-compatible language): (1) Module one: Data processing package. (2) Module two: Forward modeling package. (3) Module three: Inverse modeling package.
Book Synopsis Fracture Characterization Study by :
Download or read book Fracture Characterization Study written by and published by . This book was released on 1978 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The origin, nature and significance of fractures in general are discussed. Some typical fracture measurement techniques are discussed. Finally, geothermal fracture systems are investigated and correlations made to determine which fracture technologies from oil field work are applicable to geothermal systems. (MHR).
Book Synopsis Fracture Detection and Characterization for Geothermal Reservoir Definition by :
Download or read book Fracture Detection and Characterization for Geothermal Reservoir Definition written by and published by . This book was released on 1984 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Fracture detection and mapping techniques are discussed as follows: remote-sensing, surface, borehold (including borehold-to-borehole), and surface-to-borehole. Other experimental techniques and research needs are described. (MHR).
