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Stresses and fractures in the Frontier Formation, Green River Basin, predicted from basin-margin tectonic element interactions

Description: Natural fractures and in situ stresses commonly dictate subsurface reservoir permeability and permeability anisotropy, as well as the effectiveness of stimulation techniques in low-permeability, natural gas reservoirs. This paper offers an initial prediction for the orientations of the fracture and stress systems in the tight gas reservoirs of the Frontier Formation, in the Green River basin of southwestern Wyoming. It builds on a previous report that addressed fractures and stresses in the western part of the basin and on ideas developed for the rest of the basin, using the principle that thrust faults are capable of affecting the stress magnitudes and orientations in little-deformed strata several hundreds of kilometers in front of a thrust. The prediction of subsurface stresses and natural fracture orientations is an undertaking that requires the willingness to revise models as definitive data are acquired during drilling. The predictions made in this paper are offered with the caveat that geology in the subsurface is always full of surprises.
Date: January 1, 1996
Creator: Lorenz, J.C.
Partner: UNT Libraries Government Documents Department

Evaluation of high-efficiency gas liquid contactors for natural gas processing

Description: The objectives of this program are to develop and evaluate advanced processing technologies that can reduce the cost of upgrading sub quality natural gas to pipeline standards. The successful application of cost-effective, new technologies will facilitate the production of sub quality natural gas that otherwise would be too expensive to produce. The overall program is focused on the following activities: evaluation of the potential of structured packing for the removal of acid gases from natural gases, and expansion of the currently available database of the fluid dynamics of rotating gas liquid contactors. The natural gas sweetening, structured packing field tests are scheduled to be conducted in calendar year 1995. Design, procurement and construction of the field test unit. Expansion of the available data base on the hydraulic characteristics of a rotating gas-liquid contactor is being pursued through a series of laboratory experiments. A 100 GPM, low pressure rotary contactor system has been assembled at IGT`s Energy Development Center to examine the fluid dynamic behavior of this type of contactor. The studies are determining the effects of liquid viscosity, liquid surface tension and operating conditions on liquid residence times and flooding limits.
Date: June 1, 1995
Creator: Palla, N. & Lee, A.L.
Partner: UNT Libraries Government Documents Department

Tubular solid oxide fuel cell developments

Description: An overview of the tubular solid oxide fuel cell (SOFC) development at Westinghouse is presented in this paper. The basic operating principles of SOFCs, evolution in tubular cell design and performance improvement, selection criteria for cell component materials, and cell processing techniques are discussed. The commercial goal is to develop a cell that can operate for 5 to 10 years. Results of cell test operated for more than 50,000 hours are presented. Since 1986, significant progress has been made in the evolution of cells with higher power, lower cost and improved thermal cyclic capability. Also in this period, successively larger multi-kilowatt electrical generators systems have been built and successfully operated for more than 7000 hours.
Date: August 1, 1995
Creator: Bratton, R.J. & Singh, P.
Partner: UNT Libraries Government Documents Department

Microbially-enhanced redox solution reoxidation for sweetening sour natural gas

Description: About twenty five percent of natural gas produced in the United States is sour containing significant volumes of hydrogen sulfide and other contaminants. Liquid redox processes remove hydrogen sulfide from natural gas. Aqueous solution of chelated ferric ions oxidize the hydrogen sulfide to elemental sulfur. The reduced iron chelate is then oxidized by contact with air and recycled. This requires expensive equipment for regeneration, costly chemicals and the process is usually energy intensive. Recent studies show that the ferric ion regeneration rates are substantially enhanced in presence of acidophilic bacteria. The specific objectives of this project are to advance the technology and improve the economics of the commercial iron-based chelate processes utilizing biologically-enhanced reoxidation of the redox solutions used in these processes, such as LO-CAT II and SulFerox.
Date: June 1995
Creator: Rai, C.
Partner: UNT Libraries Government Documents Department

Development of polymer concrete for dike insulation at LNG facilities: Phase 4, Low cost materials

Description: Earlier GRI-sponsored work at Brookhaven National Laboratory has resulted in the development and utilization of insulating polymer concrete composites (IPC) as a means of reducing the evaporation rate of liquified natural gas in the event of a spill into a containment dike, thereby improving the safety at these sites. Although all of the required properties can be attained with the IPC, it was estimated that a low-cost replacement for the expensive organic binder would be necessary before use of the material would be cost-effective. In the current program, several latex modified cement formulations were evaluated and the most promising one identified. A mixture of two carboxylated styrene-butadiene latexes was selected for use in detailed laboratory property characterizations and a subsequent field evaluation. When compared to the properties of IPC, the latex-modified insulating materials display somewhat higher thermal conductivities, greater permeability to water, and reduced strength. However, these properties still meet most of the performance criteria, and the unit cost of the material is less than one-fifth that of IPC made with epoxy binders. When installed as a 0.75-in. thick overlay, material costs are estimated to be $1.00/ft{sup 2}.
Date: January 1, 1991
Creator: Kukacka, L.E.
Partner: UNT Libraries Government Documents Department

Analysis of the impacts of energy conservation codes in new single-family homes

Description: Within the 50 states some form of federal code or standard for energy conservation in new building construction is typically incorporated into state and local codes. Two of these codes, the Model Energy Code (MEC) and the proposed ASHRAE standard 90.2P are of special importance to the residential data base developed by the Gas Research Institute (GRI) because they influence thermal requirements and have either been recently updated or will be revised in 1992. In this study, we evaluate the impacts of these two thermal codes on the energy performance and energy consumption of prototypical new single-family buildings. Base case buildings, with characteristics typical of current building practices, are modified to meet the thermal envelope standards and are simulated with the DOE-2.1D building energy simulation program. In addition, we also model the effects of appliance and heating and cooling equipment efficiencies promulgated under the National Appliance Energy Conservation Act (NAECA) of 1987 and of the NAECA Amendments of 1988. We compare heating and cooling loads and energy use for the prototypical house for several cases: the base case, with 1980s vintage thermal envelope and appliance and equipment efficiencies; with ASHRAE 90 thermal requirements; with Model Energy Code thermal requirements; with NAECA appliance and HVAC efficiencies; and with combinations of the ASHRAE 90 Standard or Model Energy Code and the NAECA appliance and equipment efficiency improvements. The results provide a glimpse of how these standards will affect future end-use energy consumption in new single-family buildings.
Date: December 1, 1992
Creator: Ritschard, R.L.; Hanford, J.W. & Sezgen, A.O.
Partner: UNT Libraries Government Documents Department

Permeability reduction by pyrobitumen, mineralization, and stress along large natural fractures in sandstones at 18,300 ft. depth: Destruction of a reservoir

Description: Production of gas from the Frontier Formation at 18,300 R depth in the Frewen No. 4 Deep well, eastern Green River basin (Wyoming), was uneconomic despite the presence of numerous open natural fractures. Initial production tested at 500 MCFD, but dropped from 360 MCFD to 140 MCFD during a 10-day production test, and the well was abandoned. Examination of the fractures in the core suggests several probable reasons for this poor production. One factor is the presence of a hydrocarbon residue (carbon) which filled much of the porosity left in the smaller fractures after mineralization. An equally important factor is probably the reorientation of the in situ horizontal compressive stress to a trend normal to the main fractures, and which now acts to close fracture apertures rapidly during reservoir drawdown. This data set has unpleasant implications for the search for similar, deep fractured reservoirs.
Date: November 1, 1996
Creator: Lorenz, J.C.; Billingsley, R.L. & Evans, L.W.
Partner: UNT Libraries Government Documents Department

Enhancing the use of coals by gas reburning-sorbent injection: Volume 3 -- Gas reburning-sorbent injection at Edwards Unit 1, Central Illinois Light Company. Final report

Description: Design work has been completed for a Gas Reburning-Sorbent Injection (GR-SI) system to reduce emissions of NO{sub x} and SO{sub 2} from a wall fired unit at Central Illinois Light Company`s Edwards Station Unit 1, located in Bartonville, Illinois. The goal of the project was to reduce emissions of NO{sub x} by 60%, from the as found baseline of 0.98 lb/MBtu and to reduce emissions of SO{sub 2} by 50%. Since the unit currently fires a blend of high sulfur Illinois coal and low sulfur Kentucky coal to meet an SO{sub 2} limit of 1.8 lb/MBtu, the goal at this site was amended to meeting this limit while increasing the fraction of high sulfur coal to 57% from the current 15% level. GR-SI requires injection of natural gas into the furnace at the level of the top burner row, creating a fuel-rich zone in which NO{sub x} formed in the coal zone is reduced to N{sub 2}. Recycled flue gas is used to increase the reburning fuel jet momentum, resulting in enhanced mixing. Recycled flue gas is also used to cool the top row of burners which would not be in service during GR operation. Dry hydrated lime sorbent is injected into the upper furnace to react with SO{sub 2}, forming solid CaSO{sub 4} and CaSO{sub 3}, which are collected by the ESP. The system was designed to inject sorbent at a rate corresponding to a calcium (sorbent) to sulfur (coal) molar ratio of 2.0. The SI system design was optimized with respect to gas temperature, injection air flow rate, and sorbent dispersion. Sorbent injection air flow is equal to 3% of the combustion air. The design includes modifications of the ESP, sootblowing, and ash handling systems.
Date: March 1, 1996
Partner: UNT Libraries Government Documents Department

Biotreatment of produced waters for volume reduction and contaminant removal

Description: Produced water is wastewater that is brought to the surface from natural gas wells during natural gas production. Its constituents, mostly salt, with traces of hydrocarbons and heavy metals, are a significant disposal problem. Argonne National Laboratory (ANL), in partnership with the Gas Research Institute (GRI), has developed a low-cost, low-tech method, in which green plants are used to reduce the volume of produced water. The authors have designed an engineered bioreactor system, which is modeled after natural saline wetland ecosystems. The plant bioreactor system maximizes plant evapotranspiration to reduce wastewater volume and, concurrently, may function as a biological filter to enhance contaminant degradation and immobilization in the root/rhizosphere zone. Halophyte plant species having high salt tolerance and high transpiration rates were selected after they tested them in greenhouse experiments. Models obtained by using their greenhouse findings reduced the volume of the wastewater (up to 6% salt) by 75% in about 8 days. A field demonstration of the bioreactor, designed on the basis of the results from the greenhouse study, is successfully under way at a natural gas well site in Oklahoma. The process could offer the petroleum industry a low-cost biological alternative to existing expensive options.
Date: October 1, 1997
Creator: Negri, M.C.; Hinchman, R.R. & Mollock, J.
Partner: UNT Libraries Government Documents Department

Enhancing the use of coals by gas reburning-sorbent injection. Volume 3, Gas reburning-sorbent injection at Edwards Unit 1, Central Illinois Light Company

Description: Design work has been completed for a Gas Reburning-Sorbent Injection (GR-SI) system to reduce emissions of NO{sub x}, and SO{sub 2} from a wall fired unit. A GR-SI system was designed for Central Illinois Light Company`s Edwards Station Unit 1, located in Bartonville, Illinois. The unit is rated at 117 MW(e) (net) and is front wall fired with a pulverized bituminous coal blend. The goal of the project was to reduce emissions of NO{sub x} by 60%, from the ``as found`` baseline of 0.98 lb/MBtu (420 mg/MJ), and to reduce emissions of S0{sub 2} by 50%. Since the unit currently fires a blend of high sulfur Illinois coal and low sulfur Kentucky coal to meet an S0{sub 2} limit Of 1.8 lb/MBtu (770 mg/MJ), the goal at this site was amended to meeting this limit while increasing the fraction of high sulfur coal to 57% from the current 15% level. GR-SI requires injection of natural gas into the furnace at the level of the top burner row, creating a fuel-rich zone in which NO{sub x} formed in the coal zone is reduced to N{sub 2}. The design natural gas input corresponds to 18% of the total heat input. Burnout (overfire) air is injected at a higher elevation to burn out fuel combustible matter at a normal excess air level of 18%. Recycled flue gas is used to increase the reburning fuel jet momentum, resulting in enhanced mixing. Recycled flue gas is also used to cool the top row of burners which would not be in service during GR operation. Dry hydrated lime sorbent is injected into the upper furnace to react with S0{sub 2}, forming solid CaSO{sub 4} and CaSO{sub 3}, which are collected by the ESP. The SI system design was optimized with respect to gas temperature, injection air ...
Date: October 1, 1994
Partner: UNT Libraries Government Documents Department

Enhancing the use of coals by gas reburning-sorbent injection: Volume 4 -- Gas reburning-sorbent injection at Lakeside Unit 7, City Water, Light and Power, Springfield, Illinois. Final report

Description: A demonstration of Gas Reburning-Sorbent Injection (GR-SI) has been completed at a cyclone-fired utility boiler. The Energy and Environmental Research Corporation (EER) has designed, retrofitted and tested a GR-SI system at City Water Light and Power`s 33 MWe Lakeside Station Unit 7. The program goals of 60% NO{sub x} emissions reduction and 50% SO{sub 2} emissions reduction were exceeded over the long-term testing period; the NO{sub x} reduction averaged 63% and the SO{sub 2} reduction averaged 58%. These were achieved with an average gas heat input of 22% and a calcium (sorbent) to sulfur (coal) molar ratio of 1.8. GR-SI resulted in a reduction in thermal efficiency of approximately 1% at full load due to firing natural gas which forms more moisture in flue gas than coal and also results in a slight increase in air heater exit gas temperature. Minor impacts on other areas of unit performance were measured and are detailed in this report. The project at Lakeside was carried out in three phases, in which EER designed the GR-SI system (Phase 1), completed construction and start-up activities (Phase 2), and evaluated its performance with both short parametric tests and a long-term demonstration (Phase 3). This report contains design and technical performance data; the economics data for all sites are presented in Volume 5.
Date: March 1, 1996
Partner: UNT Libraries Government Documents Department

SPCDC: A user-friendly computational tool for the design and refinement of practical pulse combustion systems

Description: This paper reports on the development and use of a user-friendly, PC-executable computer code that can assist engineers in designing pulse combustors for specific applications and in refining existing units. This code represents the culmination of over 10 years of research and development in the field of pulse combustion. The Sandia Pulse Combustor Design Code, or SPCDC, couples both the fuel-air injection and the energy release to the time-varying pressure wave. Because the injection and combustion processes both drive and are driven by the wave dynamics, this model couples the major processes that occur in a pulse combustor. SPCDC can supplement the time-proven method of actually building and testing a prototype unit, and significantly reduce the number of units that must be tested. It will help produce a superior pulse combustion system tailored to a specific application and should help widen the range of successful applications.
Date: July 1, 1995
Creator: Barr, P. K.; Keller, J. O. & Kezerle, J. A.
Partner: UNT Libraries Government Documents Department

Ecological effects of pipeline construction through deciduous forested wetlands, Midland County, Michigan. Topical report, October 1990--August 1992

Description: This study is designed to record vegetational changes induced by the construction of a large-diameter gas pipeline through deciduous forested wetlands. Two second-growth wetland sites mapped Lenawee soils were selected in Midland County, Michigan: Site 1, a younger stand subjected to recent selective logging, and Site 2, a more mature stand. The collection of ecological data to analyze plant succession on the right-of-way (ROW) and the effects of the developing ROW plant communities on adjacent forest communities was initiated in 1989. Cover class estimates were made for understory and ROW plant species on the basis of 1 {times} 1{minus}m quadrats. Individual stem diameters and species counts were recorded for overstory plants in 10{minus}m quadrats. Although long-term studies have not been completed, firm baseline data were established for comparative analyses with future sampling. Current data indicate that vegetation became well-established on the ROW within one year and subsequently increased in coverage. About 65% of the species were wetland indicators, and the dominants included seeded and natural invading species; nevertheless, some elements of the original flora regenerated and persist. The plants of the ecotone understories of both sites changed from their original composition as a result of the installation of the gas pipeline. Although some forest species persist at both sites, the ecotone of Site I was influenced more by the seeded species, whereas the natural invaders were more important at Site 2.
Date: April 1, 1995
Creator: Rastorfer, J.R.; Van Dyke, G.D.; Zellmer, S.D. & Wilkey, P.L.
Partner: UNT Libraries Government Documents Department

Use of GRASS for routing gas pipeline rights-of-way

Description: This study, sponsored by the Gas Research Institute (GRI), was conducted to illustrate how a GIS (Geographic Information System) can be used to assess alternative routes for new gas pipeline rights-of-way (ROWs). The results show that a least-cost analysis using GRASS (Geographic Resources Analysis and Support System) is a good method for siting new gas pipeline ROWs on the basis of environmental and engineering constraints to pipeline construction and maintenance. The cost and time needed to use this least-cost approach compare favorably with the current methods used by gas pipeline company planners and engineers. The types of criteria used, as well as the costs or weights given to the criteria, can be changed easily. This provides the flexibility to assess several alternatives quickly and easily.
Date: January 1, 1992
Creator: Sydelko, P.J.
Partner: UNT Libraries Government Documents Department

Evaluation of gas-reburning and low NO sub x burners on a wall fired boiler

Description: Low NO{sub x} burners operate on the principle of delayed mixing between the coal fuel and burner air, so that less NO{sub x} is formed. Gas reburning is a combustion modification technique that consists of firing 80--85 percent of the fuel corresponding to the total heat release in the lower furnace. Reduction of NO{sub x} to molecular nitrogen (N{sub 2}) is accomplished via the downstream injection of the remaining fuel requirement in the form of natural gas (which also reduces the total SO{sub x} emissions). In a third stage, burnout air is injected at the lower temperatures in the upper furnace to complete the combustion process without generating significant additional NO{sub x}. The specific goal of this project is to demonstrate NO{sub x} emission reductions of 75 percent or more as a result of combing Low NO{sub x} Burners and Gas Reburning on a utility boiler having the design characteristics mentioned above. A Host Site Agreement has been signed by EER and a utility company in the State of Colorado: Public Service Company of Colorado (Cherokee Unit No. 3, 172 MW{sub e}) front wall fired boiler near Denver.
Date: January 15, 1992
Partner: UNT Libraries Government Documents Department

Experimental study of a high-efficiency low-emission surface combustor-heater

Description: The surface combustor-heater is a combined combustion/heat-transfer device in which the heat-exchange surfaces are embedded in a stationary bed of refractory material where gaseous fuel is burned. Because of intensive heat radiation from the hot solid particles and enhanced heat convection from the gas flow to the heat-exchange tubes, heat transfer is significantly intensified. Removing heat simultaneously with the combustion process has the benefit of reducing the combustion temperature, which suppresses NO{sub x} formation. A basic experimental study was conducted on a 60-kW bench-scale surface combustor-heater with two rows of water-cooled tube coils to evaluate its performance and explore the mechanism of combined convective-radiative heat transfer and its interaction with combustion in the porous matrix. Combustion stability in the porous matrix, heat-transfer rates, emissions, and pressure drop through the unit have been investigated for the variable parameters of operation and unit configurations. Experimental results have demonstrated that high combustion intensity (up to 2.5 MW/m{sup 2}), high heat-transfer rates (up to 310 kW/m{sup 2}), high density of energy conversion (up to 8 MW/m{sup 3}), as well as ultra-low emissions (NO{sub x} and CO as low as 15 vppm*) have been achieved. The excellent performance of the test unit and the extensive data obtained from the present experimental study provide the basis for further development of high-efficiency and ultra low-emission water heaters, boilers, and process heaters based on the surface combustor-heater concept. 4 refs., 16 figs.
Date: January 1, 1991
Creator: Xiong, Tian-yu; Khinkis, M.J. (Institute of Gas Technology, Chicago, IL (United States)) & Fish, F.F. (Gas Research Inst., Chicago, IL (United States))
Partner: UNT Libraries Government Documents Department

The minimum pore size obtainable in a silica gel during drying

Description: The pore size r{sub p} in a gel is determined by the extent of shrinkage of the gel network during drying. Shrinkage is driven by the collapse of the gel network in response to the capillary pressure P{sub c} exerted by the pore fluid. The extent of shrinkage depends on the balance between the capillary pressure P{sub c} in the pore fluid and the bulk modulus K{sub p} of the gel. The hydraulic pore radius, r{sub H} = 2V{sub p}/S{sub a}, where V{sub p} is the pore volume and S{sub a} is the apparent N{sub 2} BET surface area, is often used to characterize the pore size of a gel. A series of acid catalyzed silica gels dried in pore fluids with different {gamma}{sub lv}, showed that there is a limit to the minimum apparent r{sub H} obtainable in a gel, and when the volume fraction of porosity {phi} {le} 0.37, r{sub H} becomes constant and {approximately}0.8 nm. In contrast, experimental data show that the true pore size r{sub p} of gels continues to decrease when {phi} {le} 0.37. Analysis of their adsorption isotherms show that while r{sub H} apparently stays constant: (a) the BET C constant continues to increase, (b) the width and average of their pore size distributions continue to decrease, and (c) as shrinkage continues the gels eventually become non-porous to N{sub 2} at 77K but are still porous to CO{sub 2} at 273K. This paper reviews these results and addresses micropore formation in silica gels with the goal of determining how P{sub c} influences the final r{sub p}, and why r{sub p} and r{sub H} diverge when {phi} {le} 0.37.
Date: December 1994
Creator: Wallace, S.; Brinker, C. J. & Smith, D. M.
Partner: UNT Libraries Government Documents Department

A hybrid ED/RO process for TDS reduction of produced waters

Description: Large volumes of produced waters are generated from natural gas production. In the United States the prevailing management practice for produced waters is deep well injection, but this practice is costly. Therefore minimizing the need for deep well injection is desirable. A major treatment issue for produced waters is the reduction of total dissolved solids (TDS), which consist mostly of inorganic salts. A hybrid electrodialysis/reverse-osmosis (ED/RO) treatment process is being developed to concentrate the salts in produced waters and thereby reduce the volume of brine that needs to be managed for disposal. The desalted water can be used beneficially or discharged. In this study, laboratory feasibility experiments were conducted by using produced waters from multiple sites. A novel-membrane configuration approach to prevent fouling and scale formation was developed and demonstrated. Results of laboratory experiments and plans for field demonstration are discussed.
Date: December 31, 1995
Creator: Tsai, S.P.; Datta, R. & Frank, J.R.
Partner: UNT Libraries Government Documents Department

Evaluation of a downhole tiltmeter array for monitoring hydraulic fractures

Description: A series of hydraulic-fracture experiments using a downhole tiltmeter array, called an inclinometer array, was conducted at the Department of Energy (DOE)/Gas Research Institute (GRI) Multi-Site facility in Colorado. The inclinometer array was used to measure the deformation of the reservoir rock in response to hydraulic fracture opening and confirm microseismically measured results. In addition, the inclinometer array was found to be a useful tool for accurately measuring closure stress, measuring residual widths of both propped and unpropped fractures, estimating proppant distribution, and evaluating values of in situ moduli.
Date: March 1, 1997
Creator: Warpinski, N.R.; Engler, B.P.; Branagan, P.T.; Wilmer, R. & Wolhart, S.L.
Partner: UNT Libraries Government Documents Department

Catalytic dehydrogenation of propane and isobutane in hydrogen permselective membrane reactors

Description: The dehydrogenation of propane and isobutane was studied in hydrogen permselective packed bed membrane reactors and conventional packed bed reactors. Two different types of developmental membranes were investigated: sol-gel derived silica-based membranes and a pure palladium thin film supported by a porous ceramic substrate. The palladium membranes deactivated and eventually failed when exposed to both isobutane and propane dehydrogenation temperatures above 773 K. Moderate improvements in propylene and isobutylene yields were obtained with the silica-based membrane reactors. An isobutylene yield of 48 mole percent was obtained at a liquid hourly space velocity (LHSV) of 1.8 and temperature of 798 K compared to a yield of 39 percent in a conventional reactor operated with the same flow rate. Similar improvements in propylene yield were obtained when the silica-based membranes were tested in propane dehydrogenation experiments. There was no significant difference in the reaction selectivities for the desired olefin products when the membrane and conventional reactors were operated with the scone LHSV However, for a constant value of the olefin yield, the membrane reactors had a higher reaction selectivity since the desired yield was achieved at a higher LHSV where there was less time for side products to form. Catalyst deactivation rates were generally greater in the membrane reactors, especially when the reactors were operated with high hydrogen removal rates at temperatures of 773 K and above.
Date: September 1996
Creator: Collins, J. P.; Schwartz, R. W.; Sehgal, R. & Ward, T. L.
Partner: UNT Libraries Government Documents Department

Microseismic monitoring of the B-sand hydraulic fracture experiment at the DOE/GRI multi-site project

Description: Six hydraulic-fracture injections into a fluvial sandstone at a depth of 4500 ft were monitored with multi-level triaxial seismic receivers in two wells, resulting in maps of the growth and final geometry of each fracture based upon microseismic activity. These diagnostic images show that the hydraulic fractures are highly contained for smaller-volume KCl-water injections, but height growth is significant for the larger-volume, higher-rate, higher-viscosity treatments. Fracture lengths for most injections are similar. Final results are also compared with fracture models.
Date: November 1996
Creator: Warpinski, N. R.; Wright, T. B.; Peterson, R. E. & Branagan, P. T.
Partner: UNT Libraries Government Documents Department

Compatibility of selected ceramics with steam-methane reformer environments

Description: Conventional steam reforming of methane to synthesis gas (CO and H{sub 2}) hasa conversion efficiency of about 85%. Replacement of metal tubes in the reformer with ceramic tubes offers the potential for operation at temperatures high enough to increase the efficiency to 98-99%. However, the two candidate ceramic materials being given strongest consideration, sintered alpha Si carbide and Si carbide particulate-strengthened alumina, have been shown to react with components of the reformer environment. Extent of degradation as a function of steam partial pressure and exposure time has been studied, and results suggest limits under which these structural ceramics can be used in advanced steam-methane reformers.
Date: April 1996
Creator: Keiser, J. R.; Howell, M.; Williams, J. J. & Rosenberg, R. A.
Partner: UNT Libraries Government Documents Department

Review of hydraulic fracture mapping using advanced accelerometer-based receiver systems

Description: Hydraulic fracturing is an important tool for natural gas and oil exploitation, but its optimization has been impeded by an inability to observe how the fracture propagates and what its overall dimensions are. The few experiments in which fractures have been exposed through coring or mineback have shown that hydraulic fractures are complicated multi-stranded structures that may behave much differently than currently predicted by models. It is clear that model validation, fracture optimization, problem identification and solution, and field development have all been encumbered by the absence of any ground truth information on fracture behavior in field applications. The solution to this problem is to develop techniques to image the hydraulic fracture in situ from either the surface, the treatment well, or offset wells. Several diagnostic techniques have been available to assess individual elements of the fracture geometry, but most of these techniques have limitations on their usefulness. For example, tracers and temperature logs can only measure fracture height at the wellbore, well testing and production history matching provide a productive length which may or may not be different from the true fracture length, and tiltmeters can provide accurate information on azimuth and type of fracture (horizontal or vertical), but length and height can only be extracted from a non-unique inversion of the data. However, there is a method, the microseismic technique, which possesses the potential for imaging the entire hydraulic fracture and, more importantly, its growth history. This paper discusses application of advanced technology to the microseismic method in order to provide detailed accurate images of fractures and their growth processes.
Date: March 1, 1997
Creator: Warpinski, N.R.; Uhl, J.E. & Engler, B.P.
Partner: UNT Libraries Government Documents Department

Recent progress in tubular solid oxide fuel cell technology

Description: The tubular design of solid oxide fuel cells (SOFCs) and the materials used therein have been validated by successful, continuous electrical testing over 69,000 h of early technology cells built on a calcia-stabilized zirconia porous support tube (PST). In the latest technology cells, the PST has been eliminated and replaced by a doped lanthanum manganite air electrode tube. These air electrode supported (AES) cells have shown a power density increase of about 33% with a significantly improved performance stability over the previously used PST type cells. These cells have also demonstrated the ability to thermally cycle over 100 times without any mechanical damage or performance loss. In addition, recent changes in processes used to fabricate these cells have resulted in significant cost reduction. This paper reviews the fabrication and performance of the state-of-the-art AES tubular cells. It also describes the materials and processing studies that are underway to further reduce the cell cost, and summarizes the recently built power generation systems that employed state-of-the-art AES cells.
Date: December 31, 1997
Creator: Singhal, S.C.
Partner: UNT Libraries Government Documents Department