[PDF] Dna Encapsulated Silica Nanoparticle Tracers For Fractured Reservoir Characterization eBook

Author : Yuran Zhang
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File Size : 44,41 MB
Release : 2020
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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.

Author : Mohammed Alaskar
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File Size : 24,65 MB
Release : 2013
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The goal of this research was to develop methods for acquiring reservoir temperature data within the formation and to correlate such information to fracture connectivity and geometry. Existing reservoir-characterization tools allow temperature to be measured only at the wellbore. Temperature-sensitive nanosensors will enable in-situ measurements within the reservoir. Such detailed temperature information enhances the ability to infer reservoir and fracture properties and inform reservoir engineering decisions. This thesis provides the details of the experimental work performed in the process of developing temperature nanosensors. Several potential nanosensor candidates were investigated for their temperature-sensitivity. Particle mobility through porous and fractured media was investigated. In order for temperature nanosensors to map the reservoir temperature distribution and ultimately to characterize the fracture network, they must be transported through typical porous and fractured formation rocks without significant retention within the formation pores and/or fractures. To investigate retention mechanisms, various laboratory-scaled core-flooding and micromodel transport experiments were conducted. The results showed that the size and/or size distribution, shape, and surface charge of the particles were influential parameters governing the transport of particles through porous and fractured media. There was an optimum particle size relative to the pore size distribution of the tested rock, at which the particles experience the least retention. Pore-scale observations showed that polydisperse particle size distribution affected the particle transport adversely. Experiments also indicated that elongated or nonspherical particles exhibited greater retention within the porous medium, primarily because of their shape. Compatibility of the particle surface characteristics (surface charge) with the rock material was found to be crucial for particle transport. The transport of particles, particularly silica particles, through fractured rock was investigated. Experimental results showed that the recovery of the particles was dependent on the particle size, concentration and flow rate. The controlling transport mechanisms of silica particles were also identified. Results showed that the existence of fractures facilitated the particle transport. Particles were found to flow with the fast-moving streamlines that exist within the fracture. Pore-scale experiments confirmed by visual observation that fractures are favorable conduits for particle transport. Particle tracking showed particles were flowing with velocities comparable to maximum velocity of bulk fluid assuming a parallel-plate fracture model. The concept of using particles as a fracture caliper mechanism to estimate the fracture aperture was addressed. The feasibility of estimating the fracture aperture by correlating the size of the largest recovered particles to the fracture opening was verified by injecting a wide size distribution of particles through a fracture of predetermined hydraulic aperture. Experimental results showed that the size of the largest recovered particle was similar to the estimated aperture. Visual observations using micromodels were consistent with the results of the core-scale experiments. Temperature sensing mechanisms of potential candidates were investigated. Temperature-sensitive particles investigated in this study include the irreversible thermochromic, dye-attached silica and tin-bismuth particles. A combined heat and flow test confirmed the temperature-sensitivity of the irreversible thermochromic particles by observing the color change. A detectable change in the fluorescent emission spectrum of the dye-attached silica particles upon heating was observed. A simple sensing mechanism of melting and growth in particle size of tin-bismuth particles was demonstrated. The processing and detection of silica-encapsulated DNA particles with hydrofluoric acid chemistry was tested. A protocol to release the DNA by dissolving the silica layer without completely destroying the DNA was established. The silica-encapsulated DNA particles were flowed through a porous medium at high temperature. Some dissolution of silica particles was observed, leading to a reduction in their size. This research study showed that synthesizing particles to respond to a specific reservoir property such as temperature is feasible. Using particles to measure reservoir properties is advantageous because particles can be transported to areas in the reservoir that would not be accessible by other means and therefore provide measurements deep within the formation.

Author : Morgan F. Ames
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Page : pages
File Size : 28,63 MB
Release : 2016
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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.

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File Size : 31,43 MB
Release : 2005
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The transport of chemicals or heat in fractured reservoirs is strongly affected by the fracture-matrix interfacial area. In a vapor-dominated geothermal reservoir, this area can be estimated by inert gas tracer tests, where gas diffusion between the fracture and matrix causes the tracer breakthrough curve (BTC) to have a long tail determined by the interfacial area. For water-saturated conditions, recent studies suggest that sorbing solute tracers can also generate strong tails in BTCs that may allow a determination of the fracture-matrix interfacial area. To theoretically explore such a useful phenomenon, this paper develops an analytical solution for BTCs in slug-tracer tests in a water-saturated fractured reservoir. The solution shows that increased sorption should have the same effect on BTCs as an increase of the diffusion coefficient. The solution is useful for understanding transport mechanisms, verifying numerical codes, and for identifying appropriate chemicals as tracers for the characterization of fractured reservoirs.

Author : Vinicius Bueno
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Page : pages
File Size : 46,39 MB
Release : 2022
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"Agriculture is under heavy pressure to innovate due to the needs of feeding a rapidly growing global population while agricultural productivity has largely plateaued in recent decades. It is estimated that the world population will reach 9.1 billion by 2050 and the yearly demand for cereals, for instance, will increase by 43%, from 2.1 to 3 billion tonnes. Optimizing crop productivity and addressing current process inefficiencies are critical to meeting the increased demand without creating excessive energy and materials resource demands. Pesticide application, for example, is a highly inefficient process and it is estimated 2.45 billion kg of pesticides are wasted every year because of current application practices. That corresponds to 90% of the total pesticide applied, which end up contaminating the soil, water bodies, and impacting a range of living organisms, including humans. Nanotechnology is viewed as a promising technology to improve pesticide application. Nanocarriers, a class of nanomaterials, can be used as delivery agents for pesticides to provide slow and targeted release in the plant, and protect them against premature degradation and uptake in plants. Therefore, the use encapsulated pesticides within nanocarriers, have the potential to reduce wastage during application. The objective of the thesis is to explore the feasibility and efficacy of deploying silica nanoparticles as pesticide nanocarriers for agriculture. The scope includes the synthesis, characterization, and application of silica nanocarriers and assessing their mobility in the subsurface. The first objective was to develop a reproducible method to synthesize porous hollow silica nanoparticles (PHSN) through soft templating. In summary, when combined in the right ratio, two surfactants, cetyltrimethylammonium bromide and Pluronic P123, self-assemble forming the template onto which the SiO2 precursor can anchor to grow the SiO2 shell. The resulting PHSN population was monodisperse with diameter of 258 nm, specific surface area of 287 m2 g-1 and pore size ranging from 1.5 to 2 nm. The characterization was performed using a suite of techniques, including solid-state nuclear magnetic resonance, Fourier-transform infrared spectroscopy, transmission electronic microscopy and light scattering. It was also the first imaging demonstration of nanoencapsulation where iron (Fe) and borohydride ions diffused in the pores to reach the hollow cavity and reacted forming entrapped Fe nanoparticles. The second objective was to investigate the impacts of particle architecture and surface properties on transport in saturated porous media. Solid SiO2 nanoparticles and PHSN were tested under varying experimental conditions of pH and ionic strength. Retention of PHSN was significantly higher across the board, which was not captured by modeling. This suggests that particle architecture and surface properties play a role in the transport profile. The third objective was to investigate the impacts of nanoencapsulated azoxystrobin added to soils on plant growth and soil microbial community and how these compare with non-encapsulated formulations. Not only did the nanocarriers mitigate the toxicity of the pesticide, they also did not interfere with the soil and plant health. The fourth objective was to explore the uptake and translocation of the nanoencapsulated azoxystrobin in tomato plants following foliar application. It was demonstrated that both the nanocarrier and the pesticide were taken up and distributed throughout the plant, even though the particle size exceeded the size excluding limits discussed in the literature"--