Characterization of Retention Processes and Their Effect on the Analysis of Tracer Tests in Fractured Reservoirs PDF Download
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Languages : en
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Retention processes such as adsorption and diffusion into an immobile region can effect tracer movement through a fractured reservoir. This study has conducted experimental work and has developed a two-dimensional model to characterize retention processes. A method to directly determine some important flow parameters, such as the fracture aperture, from the analysis of tracer tests has been developed as a result of the new two-dimensional model. The experimental work consisted of batch experiments designed to both reproduce earlier work and to determine the magnitude of the retention effects. Negligible retention was observed from which it was concluded that the batch experiments were not sensitive enough and that more sensitive flowing tests were needed. A two-dimensional model that represents a fractured medium by a mobile region, in which convention, diffusion, and adsorption are allowed, and an immobile region in which only diffusion and adsorption are allowed has been developed. It was possible to demonstrate how each of the mass-transfer processes included in the model affect tracer return curves by producing return curves for any set of the defining variables. Field data from the New Zealand was numerically fit with the model. The optimum values of the parameters determined from curve fitting provided a direct estimate of the fracture width and could be used to estimate other important flow parameters if experimentally determinable values were known. 25 refs., 22 figs., 6 tabs.
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Languages : en
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Retention processes such as adsorption and diffusion into an immobile region can effect tracer movement through a fractured reservoir. This study has conducted experimental work and has developed a two-dimensional model to characterize retention processes. A method to directly determine some important flow parameters, such as the fracture aperture, from the analysis of tracer tests has been developed as a result of the new two-dimensional model. The experimental work consisted of batch experiments designed to both reproduce earlier work and to determine the magnitude of the retention effects. Negligible retention was observed from which it was concluded that the batch experiments were not sensitive enough and that more sensitive flowing tests were needed. A two-dimensional model that represents a fractured medium by a mobile region, in which convention, diffusion, and adsorption are allowed, and an immobile region in which only diffusion and adsorption are allowed has been developed. It was possible to demonstrate how each of the mass-transfer processes included in the model affect tracer return curves by producing return curves for any set of the defining variables. Field data from the New Zealand was numerically fit with the model. The optimum values of the parameters determined from curve fitting provided a direct estimate of the fracture width and could be used to estimate other important flow parameters if experimentally determinable values were known. 25 refs., 22 figs., 6 tabs.
Author: Gardner William Walkup (jr)
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Languages : en
Pages : 202
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Category : Power resources
Languages : en
Pages : 1032
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Semiannual, with semiannual and annual indexes. References to all scientific and technical literature coming from DOE, its laboratories, energy centers, and contractors. Includes all works deriving from DOE, other related government-sponsored information, and foreign nonnuclear information. Arranged under 39 categories, e.g., Biomedical sciences, basic studies; Biomedical sciences, applied studies; Health and safety; and Fusion energy. Entry gives bibliographical information and abstract. Corporate, author, subject, report number indexes.
Author: Ufuk Kilicaslan
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Languages : en
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After field redevelopment in the Sherrod Unit of the Spraberry Trend Area, an inter-well tracer test was conducted at the field scale in order to understand the fracture system, which forms preferential flow paths for better management of waterflooding. The test consisted of 13 injection wells and more than 110 producing wells that were sampled, with each injector having its own unique tracer. A wide range of tracer responses was observed in terms of tracer recovery, breakthrough time, and tracer velocity. Additional noise on tracer data was noticed due to reinjection of produced water. In this study, a comprehensive workflow is presented for dynamic reservoir characterization of naturally fractured reservoirs from an inter-well tracer test by incorporation of analytical interpretation, streamline simulation, and streamline-based optimization techniques. Categorized tracer responses were mapped according to analytical analysis, and dominating flow trends were detected in E-W and NE-SW directions before the simulation study. The constructed three-phase, dual-porosity model was simulated by a streamline simulator. Certain parameters in the model were modified based on high tracer response until a reasonable match was obtained for an inverted nine-spot pattern and breakthrough time of the injected tracer. Once the model became capable of matching historical field production, a 1-year prediction run was conducted for optimization. Cumulative oil production was increased by 8,000 bbl by allocating more water toward efficient producers, and 10,000 bbl less water was produced for the optimized case. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/151965
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Category : Geothermal engineering
Languages : en
Pages : 214
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Category : Power resources
Languages : en
Pages : 900
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Book Description
Semiannual, with semiannual and annual indexes. References to all scientific and technical literature coming from DOE, its laboratories, energy centers, and contractors. Includes all works deriving from DOE, other related government-sponsored information, and foreign nonnuclear information. Arranged under 39 categories, e.g., Biomedical sciences, basic studies; Biomedical sciences, applied studies; Health and safety; and Fusion energy. Entry gives bibliographical information and abstract. Corporate, author, subject, report number indexes.
Author: Aymen Abduljalil Alramadhan
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Languages : en
Pages : 311
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In order to understand the complex fracture network that controls water movement in Sherrod Area of Spraberry Field in West Texas and to better manage the on-going waterflood performance, a field scale inter-well tracer test was implemented. This test presents the largest inter-well tracer test in naturally fractured reservoirs reported in the industry and includes the injection of 13 different tracers and sampling of 110 producers in an area covering 6533 acres. Sherrod tracer test generated a total of 598 tracer responses from 51 out of the 110 sampled producers. Tracer responses showed a wide range of velocities from 14 ft/day to ultra-high velocities exceeding 10,000 ft/day with same-day tracer breakthrough. Re-injection of produced water has caused the tracers to be re-injected and added an additional challenge to diagnose and distinguish tracer responses affected by water recycling. Historical performance of the field showed simultaneous water breakthrough of a large number of wells covering entire Sherrod area. This research investigate analytical, numerical, and inversion modeling approaches in order to categorize, history match, and connect tracer responses with water-cut responses with the objective to construct multiple fracture realizations based entirely on water-cut and tracers' profiles. In addition, the research highlight best practices in the design of inter-well tracer tests in naturally fractured reservoirs through lessons learned from Sherrod Area. The large number of tracer responses from Sherrod case presents a case of naturally fractured reservoir characterization entirely based on dynamic data. Results indicates that tracer responses could be categorized based on statistical analysis of tracer recoveries of all pairs of injectors and producers with each category showing distinguishing behavior in tracers' movement and breakthrough time. In addition, it showed that tracer and water-cut responses in the field are dominantly controlled by the fracture system revealing minimum information about the matrix system. Numerical simulation studies showed limitation in dual porosity formulation/solvers to model tracer velocities exceeding 2200 ft/day. Inversion modeling using Gradzone Analysis showed that east and north-west of Sherrod have significantly lower pore volume compared to south-west. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/151192
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Category : Geothermal engineering
Languages : en
Pages : 296
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Category : Petroleum
Languages : en
Pages : 1416
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Author: Yuran Zhang
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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.
