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At least 289 records · Page 16

The Application of Hydraulic and Thermal Stimulation Techniques to Create Enhanced Geothermal Systems

Geothermal energy production requires temperature at depth, a working fluid to transport heat to the surface, and a network of fluid pathways connecting injection and production wells. These requirements constrain the availability of geothermal energy resources. Enhanced Geothermal System (EGS) development expands geothermal resource availability by artificially generating networks of fluid pathways in the reservoir. This is accomplished through hydraulic and thermal stimulation of the geothermal reservoir. Hydraulic and thermal techniques were applied at the Raft River geothermal field as part of a Department of Energy (DOE) EGS development project. The test well RRG-9 ST1 was hydraulically stimulated three times between February 2012 and April 2014. Since June, 2013 continuous injection of sub-reservoir temperature plant water has been used to thermally stimulate the well. The stimulation program has resulted in a large increase in the injectivity of the well, an increase from less than 20 gpm in June 2013 to nearly 1,000 gpm in April 2016. Wellbore imaging and temperature analysis identified a northeast striking fracture zone intersecting the well between 5,640 and 5,660 ft. measured depth (MD) has nominally accepted all of the injected fluid. Microseismic activity, related to stimulation program and plant activity was used to track possible fluid pathways within the reservoir. The microseismic data indicates that the injected fluid moves primarily to the northeast through the Narrows Zone, a northeast striking fault structure that bisects the field. Tracers injected into RRG-9 ST1 and recovered at the production wells RRG-2 and RRG-4, located to the northeast of RRG-9 ST1, support this theory. It is hypothesized that water injected into RRG-9 ST1 moves through the intersecting fracture zone which connects into the Narrows Zone, and then moves along the Narrows Zone to the northeast. This conceptual model was numerical simulated using FALCON a finite element reservoir simulation code developed by Idaho National Laboratory. The modeling suggests that both thermal and hydraulic fracturing mechanisms played an important role in improving the injectivity at RRG-9 ST1. The stimulation program at Raft River has successfully demonstrated the effectiveness of hydraulic and thermal stimulation techniques. RRG-9 ST1 is now in commercial use.

15 GEOTHERMAL ENERGY↗

Advancing Reactive Tracer Methods for Measurement of Thermal Evolution in Geothermal Reservoirs (Final Report)

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.

15 GEOTHERMAL ENERGY↗

Electroconvection of a poorly conducting fluid under unipolar charge injection in a steady electric field

We study the stability of equilibrium and nonlinear regimes of a nonuniformly heated poorly conducting fluid in a horizontal capacitor in the gravity field and in a dc electric field under a unipolar charge injection. A model in which the density of charges injected from the cathode is proportional to the electric field strength in the capacitor is considered. The dependences of critical parameters on the degree of heating and charge injection are determined. The effect of the Prandtl number on the equilibrium instability boundary and on the frequency of neutral vibrations is analyzed. Nonlinear regimes of electroconvection are studied for heating from below.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

Radial particle-based terrestrial thermocline for high temperature thermal storage

A system or method for thermal storage includes a recess or containment unit having a first storage layer and a second storage layer comprising a permeable filler material. An intermediate layer is disposed between the storage layers. A primary well traverses the layer in the recess. The primary well is in thermal communication with the first permeable filler material and the second permeable filler material. A heat source is provided for heating an inlet fluid. An input pump is in fluid communication with the primary well and the heat source. The primary well receives heated inlet fluid from the inlet pump and injects the fluid into the second layers. The heated inlet fluid transfers heat to the respective permeable filler material radially from the primary well toward an outer periphery of the thermocline recess.

Ho, Clifford K.↗

Investigation of representing hysteresis in macroscopic models of two-phase flow in porous media using intermediate scale experimental data

Incorporating hysteresis into models is important to accurately capture the two phase flow behavior when porous media systems undergo cycles of drainage and imbibition such as in the cases of injection and post-injection redistribution of CO 2 during geological CO 2 storage (GCS). In the traditional model of two-phase flow, existing constitutive models that parameterize the hysteresis associated with these processes are generally based on the empirical relationships. This manuscript presents development and testing of mathematical hysteretic capillary pressure—saturation—relative permeability models with the objective of more accurately representing the redistribution of the fluids after injection. The constitutive models are developed by relating macroscopic variables to basic physics of two-phase capillary displacements at pore-scale and void space distribution properties. The modeling approach with the developed constitutive models with and without hysteresis as input is tested against some intermediate-scale flow cell experiments to test the ability of the models to represent movement and capillary trapping of immiscible fluids under macroscopically homogeneous and heterogeneous conditions. The hysteretic two-phase flow model predicted the overall plume migration and distribution during and post injection reasonably well and represented the postinjection behavior of the plume more accurately than the nonhysteretic models. In conclusion, based on the results in this study, neglecting hysteresis in the constitutive models of the traditional two-phase flow theory can seriously overpredict or underpredict the injected fluid distribution during post-injection under both homogeneous and heterogeneous conditions, depending on the selected value of the residual saturation in the nonhysteretic models.

58 GEOSCIENCES↗

Gas Injection Apparatus for Vacuum Chamber

We present in this article a gas injection apparatus which comprises the gas injector and its electronic command for vacuum chamber applications. Some of these applications are thin-film deposition by a pulsed laser deposition (PLD) or a cathodic arc deposition (arc-PVD) and the plasma generation. The electronic part has been developed to adjust the flow of the gas inside the vacuum chamber by controlling both of the injector's opening time and the repetition frequency to allow a better gas flow. In this case, the system works either on a pulsed mode or a continuous mode for some applications. In addition, the repetition frequency can be synchronised with a pulsed laser by an external signal coming from the laser, which is considered as an advantage for users. Good results have been obtained using the apparatus and testing with Argon and Nitrogen gases.

36 MATERIALS SCIENCE↗

Fluid migration in low-permeability faults driven by decoupling of fault slip and opening

Understanding the response of faults to the injection of high-pressure fluids is important for several subsurface applications, for example, geologic carbon sequestration or energy storage. Lab-based experiments suggest that fluid injection can activate fault slip and that this slip can lead to increased fluid transmission along low-permeability faults. Here we present in situ observations from a cross-borehole fluid-injection experiment in a low-permeability shale-bearing fault, which show fault displacement occurring before fluid-pressure build-up. Comparing these observations with numerical models with differing permeability evolution histories, we find that the observed variation in fluid pressure is best explained by a change in permeability only after the fault fails and slips beyond the pressurized area. Once fluid migration occurs along the fault as a result of slip-induced permeability increase, the fault experiences further opening due to a decrease in the effective normal stress. We then suggest that decoupling of fault slip and opening, leading to a rapid increase in fluid pressurization following the initial fault slip, could be an efficient driver for fluid migration in low-permeability faults.

58 GEOSCIENCES↗

High-Fidelity Simulation of the Light-to-Dense Stratification Transient in the HiRJET Facility

Density stratification in a large enclosure is a crucial phenomenon to heat transfer and sustainable passive heat removal of a sodium fast reactor during reactivity transients. However, engineering turbulence models were identified to have unsatisfactory performance in predicting propagation of a stratified front. Yet, the scarcity of high-resolution data for stratification hampers the development of models. To explor e applications of leveraging direct numerical simulation (DNS) data to support turbulence model development, this work conducted DNS using NekRS to study a long stratification transient in the High-Resolution Jet (HiRJET) experimental facility. Here, this work considers an experiment run where light fluid is injected into a tank containing a denser fluid with a relative density difference of 1.5%. Formation of the stratified layer is identified as impingement of the buoyant jet promoting mixing of the two fluids. Based on the transient statistics, transport of the concentration can be characterized by regions with dominating effects of turbulent mixing, buoyant dissipation, and molecular diffusion, respectively, as moving away from the elevation of jet impingement. Concentration near the stratified front also exhibits oscillation at Brunt-Väisälä frequency. Preliminary validation of the simulation showed encouraging agreement of the concentration distribution with the reference experiment.

buoyant mixing↗

Geochemical Impact of Acid Spearhead and Slickwater Stimulation on Wolfcamp Shale from the Hydraulic Fracturing Test Site

The Hydraulic Fracturing Test Site 1 (HFTS-1) was a field study performed in the Wolfcamp Formation in the West Texas Permian (Midland) Basin, USA, with a focus on improving the efficiency of hydraulic fracturing. Investigating site-specific rock-fluid geochemical interactions during hydraulic fracturing is an important step to understanding the impact on formation shale porosity, permeability, and long-term shale gas production. During field operations in this region, hydraulic fracturing fluid (HFF) injection usually starts with a concentrated acid spearhead for rapid rock dissolution, followed by the injection of near-neutral pH slickwater containing chemicals and proppants. A multistep sequential injection approach was used to investigate different stages of rock-fluid interactions. The carbonate content in the host rock is important when acid spearhead is considered, as carbonate mineral dissolution is rapid and can result in porosity and permeability changes in the shale matrix. Here, in this study, we designed flow-through experiments using fractured carbonate-rich and clay-rich Wolfcamp shale cores with (1) a short-time acid soaking step and (2) a long-term slickwater flow-through step to simulate the injection method used at HFTS-1. The fluid chemistry was analyzed. A thorough mineralogical progression [e.g., Calcium (Ca) dissolution and iron (Fe) redox progression] in the cores during HFF injection was also characterized and imaged by synchrotron microprobe. Reactive transport modeling was performed based on the experimental setup. The results showed that the acid spearhead is a crucial step in creating a reaction front by mineral dissolution, especially in carbonate-rich shales. A slight layer of ferrihydrite precipitated during the slickwater flow-through period. This study provides insights into potential geochemical impact due to hydraulic fracturing operations in the Permian Basin.

clastic rock↗

Endwall Treatment and Method for Gas Turbine

An endwall treatment for a gas turbine engine having at least one rotor blade extending from a rotatable hub and a casing circumferentially surrounding the rotor and the hub, the endwall treatment including, an inlet formed in an endwall of the gas turbine engine adapted to ingest fluid from a region of a higher-pressure fluid, an outlet formed in the endwall and located in a region of lower pressure than the inlet, wherein the inlet and the outlet are in a fluid communication with each other, the outlet being adapted to inject the fluid from the inlet in the region of lower pressure, and wherein the outlet is at least partially circumferentially offset relative to the inlet.

Hathaway, Michael D.↗

System and Method for Traversing Pipes

A system and method is provided for traversing inside one or more pipes. In an embodiment, a fluid is injected into the one or more pipes thereby promoting a fluid flow. An inspection device is deployed into the one or more pipes at least partially filled with a flowing fluid. The inspection device comprises a housing wherein the housing is designed to exploit the hydrokinetic effects associated with a fluid flow in one or more pipes as well as maneuver past a variety of pipe configurations. The inspection device may contain one or more sensors capable of performing a variety of inspection tasks.

Azimi, Shaun↗

Causal mechanism of injection-induced earthquakes through the M w 5.5 Pohang earthquake case study

Causal mechanisms for fluid injection-induced earthquakes remain a challenge to identify. Past studies largely established spatiotemporal correlations. Here, we propose a multi-process causal mechanism for injection-induced earthquakes through a case study of the 2017 M w 5.5 induced earthquake near Pohang Enhanced Geothermal System, Korea, where detailed hydraulic stimulation and on-site seismicity monitoring data provide an unprecedented opportunity. Pore pressure modeling reveals that pore pressure changes initiate seismicity on critically stressed faults and Coulomb static stress transfer modeling reveals that earthquake interactions promote continued seismicity, leading to larger events. On the basis of these results, we propose the following causal mechanism for induced seismicity: pore pressure increase and earthquake interactions lead to fault weakening and ultimately triggering larger earthquakes later in the process. We suggest that it is prudent that pore pressure change, initial seismicity locations, and Coulomb static stress transfer from seismicity earlier in the sequence are assessed in real-time.

58 GEOSCIENCES↗

Assessing the combined influence of fluid-rock interactions on reservoir properties and injectivity during CO 2 storage in saline aquifers

Complex fluid-rock interactions can occur during the injection of carbon dioxide (CO 2 ) into saline aquifers for sequestration, which may affect CO 2 injectivity and storage capacity. A comprehensive reactive transport model is established to analyze salt precipitation, CO 2 -water-rock geochemical reactions, and their effects on reservoir physical properties and injectivity. In addition, sensitivity analyses are conducted to investigate the main factors that affect fluid-rock interactions and injectivity with relevance for site selection for CO 2 storage. Results show that the back flow of formation water not only affects the salt precipitation but also affects the CO 2 -water-rock geochemical reactions, resulting in salt and calcite precipitations mainly occurring in the dry-out zone. However, most of the mineral dissolution/precipitation caused by CO 2 -water-rock reaction occurs in the two-phase and aqueous-phase zones, and their effect on reservoir porosity and permeability are small. A considerable amount of sodium chloride precipitates in the dry-out zone as brine is drawn by capillary action into this zone, with significant consequences for porosity, permeability and injectivity. The injection rate, salinity, capillary pressure–saturation relationships, and reservoir permeability strongly affect the distribution of salt precipitation. Finally, moderate injection rates, salinities, capillary pressures, and permeabilities all lead to favorable CO 2 injectivity.

54 ENVIRONMENTAL SCIENCES↗

Stabilising falling liquid film flows using feedback control

Falling liquid films become unstable due to inertial effects when the fluid layer is sufficiently thick or the slope sufficiently steep. This free surface flow of a single fluid layer has industrial applications including coating and heat transfer, which benefit from smooth and wavy interfaces, respectively. Here, we discuss how the dynamics of the system are altered by feedback controls based on observations of the interface height, and supplied to the system via the perpendicular injection and suction of fluid through the wall. In this study, we model the system using both Benney and weighted-residual models that account for the fluid injection through the wall. We find that feedback using injection and suction is a remarkably effective control mechanism: the controls can be used to drive the system towards arbitrary steady states and travelling waves, and the qualitative effects are independent of the details of the flow modelling. Furthermore, we show that the system can still be successfully controlled when the feedback is applied via a set of localised actuators and only a small number of system observations are available, and that this is possible using both static (where the controls are based on only the most recent set of observations) and dynamic (where the controls are based on an approximation of the system which evolves over time) control schemes. This study thus provides a solid theoretical foundation for future experimental realisations of the active feedback control of falling liquid films.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

Three-dimensional fracture continuum characterization aided by surface time-domain electromagnetics and hydrogeophysical joint inversion—proof-of-concept

Efficient and safe production of hydraulically fractured reservoirs benefits from the prediction of their geometrical attributes. Geophysical methods have the potential to provide data that are sensitive to fracture geometries, alleviating the typically sparse nature of in situ reservoir observations. Moreover, surface-based methods can be logistically and economically attractive since they avoid operational interference with the injection well infrastructure. Here, we investigate the potential of the surface-based time-domain electromagnetic (EM) method. EM methods can play an important role owing to their sensitivity to injection-induced fluid property changes. Two other advantageous factors are the EM signal-enhancing effect of vertical steel-cased wells and the fact that injected proppants can be enhanced to produce a stronger electrical conductivity contrast with the reservoir’s connate fluid. Nevertheless, an optimal fracture characterization will no doubt require the integration of EM and reservoir injection and production data. We hence carry out our investigations within a hydrogeophysical parameter estimation framework where EM data and injection flow rates are combined in a fully coupled way. Given the interdisciplinary nature of coupled hydrogeophysical inverse modeling, we dedicate one section to laying out key aspects in a didactic manner.

58 GEOSCIENCES↗

Microbe Detector

Under NASA contracts, McDonnell Douglas developed a microbial load monitor to detect bacterial contamination. Vitek Systems, Inc., a subsidiary, was created to commercialize the product for analyzing body fluids. With the AutoMicrobic System, infections may be treated more quickly. The process involves injecting the fluid into identification cards and screening the reaction. Antibiotic treatments are also suggested. Time in hospital and human error is reduced. There are also possible industrial and environmental applications.

Source record↗

Bubble Generation in a Continuous Liquid Flow Under Reduced Gravity Conditions

The present work reports a study of bubble generation under reduced gravity conditions for both co-flow and cross-flow configurations. Experiments were performed aboard the DC-9 Reduced Gravity Aircraft at NASA Glenn Research Center, using an air-water system. Three different flow tube diameters were used: 1.27, 1.9, and 2.54 cm. Two different ratios of air injection nozzle to tube diameters were considered: 0.1 and 0.2. Gas and liquid volumetric flow rates were varied from 10 to 200 ml/s. It was experimentally observed that with increasing superficial liquid velocity, the bubbles generated decreased in size. The bubble diameter was shown to increase with increasing air injection nozzle diameters. As the tube diameter was increased, the size of the detached bubbles increased. Likewise, as the superficial liquid velocity was increased, the frequency of bubble formation increased and thus the time to detach forming bubbles decreased. Independent of the flow configuration (for either single nozzle or multiple nozzle gas injection), void fraction and hence flow regime transition can be controlled in a somewhat precise manner by solely varying the gas and liquid volumetric flow rates. On the other hand, it is observed that uniformity of bubble size can be controlled more accurately by using single nozzle gas injection than by using multiple port injection, since this latter system gives rise to unpredictable coalescence of adjacent bubbles. A theoretical model, based on an overall force balance, is employed to study single bubble generation in the dynamic and bubbly flow regime. Under conditions of reduced gravity, the gas momentum flux enhances bubble detachment; however, the surface tension forces at the nozzle tip inhibits bubble detachment. Liquid drag and inertia can act either as attaching or detaching force, depending on the relative velocity of the bubble with respect to the surrounding liquid. Predictions of the theoretical model compare well with performed experiments. However, at higher superficial,liquid velocities, the bubble neck length begins to significantly deviate from the value of the air injection nozzle diameter and thus the theory no longer predicts the experiment behavior. Effects of fluid properties, injection geometry and flow conditions on generated bubble size are investigated using the theoretical model. It is shown that bubble diameter is larger in a reduced gravity environment than in a normal gravity environment at similar flow condition and flow geometry.

Pais, Salvatore Cezar↗

Foam rigidized inflatable structural assemblies

An inflatable and rigidizable structure for use as a habitat or a load bearing structure is disclosed. The structure consists of an outer wall and an inner wall defining a containment member and a bladder. The bladder is pressurized to erect the structure from an initially collapsed state. The containment member is subsequently injected with rigidizable fluid through an arrangement of injection ports. Exhaust gases from the curing rigidizable fluid are vented through an arrangement of exhaust ports. The rate of erection can be controlled by frictional engagement with a container or by using a tether. A method for fabricating a tubular structure is disclosed.

Tinker, Michael L.↗