Long-term Flow Test Research Articles

Preparing porous Cu/Pd electrode on nickel foam using hydrogen bubbles dynamic template for high-efficiency and high-stability removal of nitrate from water.

Electrochemical reduction is a promising technology to remove nitrate from water. The metallic composition and geometry of electrodes usually dominate the nitrate removal property. Based on nickel foam (NF), we prepared Cu/Pd bimetallic electrode using hydrogen bubbles dynamic template according to a two-step electrodeposition method (Pd after Cu). The micromorphology, crystal structure, and metallic composition were analyzed by using the field emission scanning electron microscope with energy dispersive spectroscopy (FESEM-EDS), powder X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) instruments, respectively. 4.4mg of Cu and 1.4mg of Pd were detected on the prepared Cu/Pd electrode. The micromorphology of prepared Cu/Pd electrode showed a grape-bunch look with porous structure of two stage sizes (100-500nm and 200-300μm). 98% of the initial NO3--N (100mg/L) was removed under the potential of - 1.6V vs. Ag/AgCl saturated KCl after 24h of reaction when using 0.05mol/L of Na2SO4 or NaCl as electrolyte. But the concentration of produced NH4+-N was higher than 80mg/L when using Na2SO4 as electrolyte, which was close to 0mg/L when using NaCl as electrolyte. The cyclic voltammetry curves of 1000 cycles and the long-term continuous flow test of about 200h suggested that the prepared Cu/Pd electrode showed high stability for nitrate removal from water.

The bioturbation effect of the snail Bellamya aeruginosa on phosphorus immobilisation by drinking water treatment residue in sediment: A long-term continuous flow test

This study used a relatively long-term (350 d) continuous flow test to determine the bioturbation effect of a benthic macroinvertebrate (the snail Bellamya aeruginosa) on sediment internal phosphorus (P) pollution control by in-situ immobilisation using drinking water treatment residue (DWTR) as the inactivating agent. The results showed that DWTR substantially reduced P concentration in overlying water, had a limited effect on other overlying water properties, and tended to reduce nitrogen release from the sediment. Variations in overlying water properties induced by DWTR were generally not associated with snail activity or population density. However, the snails were found to promote DWTR burial and induce DWTR mixing within the sediment, indicating that bioturbation could change the distribution of P inactivating agents in sediment. The mobility of P was closely related to oxalate extractable aluminium, iron, and P (Alox, Feox, and Pox, respectively) in sediments at different depths. Typically, mobile P was stable at a relatively low level when the total content of Alox and Feox was >0.750 mmol g−1 or when the ratio of Pox to (Alox + Feox) was <0.05. Given these results, recommended practices include repeated dosing of the immobilising agents at intervals determined by the relationships among mobile P, Pox, Alox, and Feox in the sediment, especially for Al- and Fe-based agents such as DWTR. Overall, the effect of bioturbation on the stability of in-situ P immobilisation in sediment should be fully considered during long-term pollution control.

The EGS Collab Project: An intermediate-scale field test to address enhanced geothermal system challenges

Three components are typically needed to extract geothermal energy from the subsurface: 1. hot rock, 2. a heat transfer fluid, and 3. flow pathways contacting the fluid and the rock. These naturally occur in many locations resulting in hydrothermal systems, however there are enormous regions containing hot rock that do not naturally have adequate fluid, and/or appropriate fluid permeability to allow hot fluid extraction. Some type of engineering or enhancement of these systems would be required to extract the energy. These enormous regions provide the possibility of long-term extraction of significant quantities of energy. Enhanced (or engineered) Geothermal Systems (EGS) are engineered reservoirs created to extract economical amounts of heat from low permeability and/or porosity geothermal resources. There are technological challenges that must be addressed in order to extract the heat. These include proper stimulation, effective monitoring, reservoir control, and reservoir sustainability. The US DOE Geothermal Technologies Office and geothermal agencies from other countries have supported field tests over a range of scales and conditions. A current US field project, the EGS Collab Project, is working nearly a mile deep in crystalline rock at the Sanford Underground Research Facility (SURF) to study rock stimulation under EGS stress conditions. We are creating intermediate-scale (tens of meters) test beds via hydraulic stimulation and are circulating chilled water to model the injection of cooler water into a hot rock which would occur in an EGS, gathering high resolution data to constrain and validate thermal-hydrological-mechanical-chemical (THMC) modeling approaches. These validated approaches would then be used in the DOE’s flagship EGS field laboratory, Frontier Observatory for Research in Geothermal Energy (FORGE) underway in Milford, Utah and in commercial EGS. In the EGS Collab project, numerous stimulations have been performed, characterized, and simulated and long-term flow tests have been completed.

Hydrodeoxygenation of water-insoluble bio-oil to alkanes using a highly dispersed Pd\u2013Mo catalyst

Bio-oil, produced by the destructive distillation of cheap and renewable lignocellulosic biomass, contains high energy density oligomers in the water-insoluble fraction that can be utilized for diesel and valuable fine chemicals productions. Here, we show an efficient hydrodeoxygenation catalyst that combines highly dispersed palladium and ultrafine molybdenum phosphate nanoparticles on silica. Using phenol as a model substrate this catalyst is 100% effective and 97.5% selective for hydrodeoxygenation to cyclohexane under mild conditions in a batch reaction; this catalyst also demonstrates regeneration ability in long-term continuous flow tests. Detailed investigations into the nature of the catalyst show that it combines hydrogenation activity of Pd and high density of both Brønsted and Lewis acid sites; we believe these are key features for efficient catalytic hydrodeoxygenation behavior. Using a wood and bark-derived feedstock, this catalyst performs hydrodeoxygenation of lignin, cellulose, and hemicellulose-derived oligomers into liquid alkanes with high efficiency and yield.

유용미생물을 이용한 포러스 콘크리트의 장기간 연속흐름 실험을 통한 수질정화 효과 검토

이 연구는 생물의 서식기반 제공 효과가 있는 다공질의 부석 및 포러스 콘크리트와 대사 작용 및 항산화작용에 의해 유기?오염물질을 분해시켜 오염된 하천수의 수질정화 효과가 있는 유용미생물을 동시에 이용하여 장기간 연속흐름시험을 통한 수질정화 특성을 검토하고자 하였다. 특히 기존의 미생물 탈리 등의 문제점을 해결하기 위하여 이 연구에서는 16S rDNA 염기서열 분석법에 의해 동정된 유용 미생물을 포러스 콘크리트 제조과정에서 각 단계별로 3차 처리하였으며, 최적의 연속흐름 실험을 위한 농도 및 체류시간별에 따른 기초실험을 통하여 운전조건을 검토하였다. 실험 결과 유용미생물을 적용한 포러스 콘크리트는 수질 및 생물에 대한 독성이 없는 것으로 나타났다. 그리고 일반 포러스 콘크리트 보다 유용미생물을 적용한 포러스 콘크리트가 우수한 제거효율을 나타내었으며, 150일 이상 큰 변화를 나타내지 않아 장기간 운전이 가능할 것으로 판단된다. 이와 같이 유용미생물을 적용한 포러스 콘크리트의 장기간 연속흐름 실험으로 오염물질 처리성능에 대한 검토를 통하여 오염된 수질을 향상시킬 수 있을 것이라고 판단되며, 실험과정 중 나타난 문제점들이 보완된다면 하천에 적용하여 유입되는 비점오염원을 저감시킬 수 있을 것으로 기대된다.

Modelling of temperature conditions near the bottom of well IDDP-1 in Krafla, Northeast Iceland

The transient temperature conditions near the bottom of well IDDP-1 in Krafla, which was drilled into a magma intrusion, have been simulated by some simple models of: (i) evolution of temperature conditions at the magma intrusion, (ii) cooling of the producing zone, a permeable layer above the intrusion, due to circulation losses during drilling and subsequent injection, (iii) reheating of the permeable layer after drilling and (iv) temperature evolution during the early phases of discharge testing in 2010. The modelling is not definitive, and does not consider later, more long-term flow testing (2011–2012), because the necessary down-hole data are lacking. However, results indicate that the evolution of the temperature conditions can be explained by these models. If the magma was emplaced during the most recent Krafla volcanic episode 25–35 years ago, the intrusion must have a thickness of at least 50–100m. The effective thickness of the permeable layer is estimated to be about 45m and its equilibrium temperature to be 390–400°C. No direct contact of the fluid with the magma is needed to explain the superheated steam discharged by the well. The situation near the bottom of the well clearly warrants further study, both through more advanced modelling and input of further data. The IDDP-1 well had to be quenched in July 2012. Whether it can maintain in the long-term the high energy output (15–40MWe), achieved during discharge testing, depends on sufficient recharge and efficient heat-exchange, if it can be rehabilitated. Carefully executed reinjection may be the solution if long-term recharge is not sufficient.

Precipitation of Hydrated Silica From Spent Hydrofluoric Acid: How Much of a Problem Is It? (includes associated papers 16441 and 16444 )

Summary Recent studies have shown that the reaction of clay withhydrofluoric (HF) acid is more complex than was earlier believed. It hasbeen found that fluosilicic acid, generated during initial dissolution ofclay, reacts with additional clay, extracting aluminum and depositing hydrated silica. It has been suggested that this silica precipitation may result in significant formation damage. The paper describes studies designed to investigate further the silicadeposition phenomenon as it relates to potential formation damage. Possible beneficial effects resulting from clay stabilization also areexplored. Long core tests show that in spite of extensive silica precipitation, there is little evidence of actual formation damage. Scanning electronmicroscope (SEM) examination of clays situated beyond the zone ofpermeability improvement shows major modification of clay surfaces as aresult of secondary reactions. Sand grains appear clean, however, withsilica deposition apparently confined to the clays. Energy-dispersive X-ray (EDX) analysis of modified clays indicates complete loss of alumin. Bulk analysis of core material, however, reveals that much undissolved aluminum remains through the entire length of the acidized core. Water-sensitivity testing of acidized cores shows almost completestabilization of clays both in the zone of permeability improvement and fora considerable distance beyond. Long-term flow testing reveals no increasein the migration tendency of fines as a result of the acid treatment. Introduction Precipitation of insoluble reaction products from spent HFacid has long been recognized as a major problem insandstone-matrix acidizing. The reaction of HF acidwith clays, feldspars, and other minerals can result in theformation of various insoluble precipitates. Failure toconsider this problem can lead to poor treatment results and, in some cases, severe formation damage. HF acid is usually used in sandstone-matrix acidizing because of its ability to dissolve a variety of siliceousminerals, including quartz, clay, and feldspar. Althoughquartz (SiO2) constitutes the bulk of most sandstoneformations, the greatest portion of the HF acid is consumed by reaction with clays and feldspars because of their muchfaster reaction rate. It has been estimated that thereaction rate of HF acid with clay is 100 to 200 times fasterthan with quartz. As a result, the reaction with quartzis so limited that it is usually ignored, and thegeneralized initial reaction of HF acid with clays in theformation is expelled as Actually, this is only the initial stage of a complexreaction sequence. Depending on free fluorideconcentration, silicon fluorides can exist as SiF4, SiF5 -, andSiF6 --, while the aluminum fluorides are present as Al+++, AlF++, AIF2+... AlF6. Because aluminumhas a greater affinity for fluorine than silicon, the siliconfluorides and more-fluoride-rich aluminum species reactwith undissolved clays, extracting aluminum andprecipitating hydrated silica. Thus the aluminumconcentration in the acid increases with a corresponding decreasein silicon content. As a result, most of the silicon initially dissolved by the HF acid precipitates within the matrixof the rock. That this can be a major cause of formationdamage has been suggested. In addition to Si(OH)4 Precipitation, other insolublereaction products can also form. Among these areNa2SiF6, K2SiF6, and CaF2. All these materials arerelatively insoluble. Damage resulting from theirprecipitation, however, can be minimized by use of an HClpreflush, ahead of the HF acid, to remove any CaCO3present and by avoidance of brines containing Ca, Na, or K during the treatment. However, there is no knownway to prevent precipitation of Si(OH)4, exceptpossibly by returning the spent acid before precipitation occurs. The main purpose of this study was to investigate thedegree of damage caused by Si(OH)4 precipitation and, if necessary, to propose methods of minimizing thisdamage. Formation Damage FromSilica Precipitation Precipitation of hydrated silica from spent HF acid hasbeen the subject of extensive investigation. Theconditions under which Si(OH)4 precipitation occurs havebeen established, and there is little doubt that most of the silicon dissolved by HF acid during acidizing ofargillaceous sandstone is precipitated as hydrated silica beforethe spent acid can be recovered from the formation. Themanner in which the precipitate forms and the magnitude of the resulting formation damage, however, have notbeen thoroughly investigated. JPT P. 1234^

Rapid, High-Temperature, Field Test Method for Evaluation of Geothermal Calcium Carbonate Scale Inhibitors

Summary A new test method is described that allows the rapid field testing of calcium carbonate scale inhibitors at 500° F [260 °C]. The method evolved from use of a full-flow test loop on a well with a mass flow rate of about 1×106 lbm/hr [126 kg/s]. It is a simple, effective way to evaluate the effectiveness of inhibitors under field conditions. Five commercial formulations were chosen for field evaluation on the basis of nonflowing, laboratory screening tests at 500°F [260°C]. Four of these formulations from different suppliers controlled calcium carbonate scale deposition as measured by the test method. Two of these could dislodge recently deposited scale that had not age-hardened. Performance-profile diagrams, which were measured for these four effective inhibitors, show the concentration interrelationship between brine calcium and inhibitor concentrations at which the formulations will and will not stop scale formation in the test apparatus. With these diagrams, one formulation was chosen for testing on the full-flow brine line. The composition was tested for 6 weeks and showed a dramatic decrease in the sealing occurring at the flow-control valve. This scaling was about to force a shutdown of a major, long-term flow test being done for reservoir economic evaluations. The inhibitor stopped the scaling, and the test was performed without interruption.

MASSIVE HYDRAULIC FRACTURE STIMULATION OF EARLY PERMIAN GAS RESERVOIRS, BIG LAKE FIELD, COOPER BASIN

In 1981, South Australian Oil and Gas Corporation Pty Ltd commenced a project to apply Massive Hydraulic Fracture (MHF) technology to the tight gas reservoirs of the Tirrawarra and Patchawarra Formations of the Big Lake Field. Four wells had defined the potential at depths of 8500-10 000 ft (2500-3000 m) in the early 1970s but early attempts to stimulate gas production were unsuccessful.The Tirrawarra Sandstone, as a massive unit of 120-200 ft (35-60 m) thickness, was a prime candidate. The Patchawarra sandstones, ranging up to 40 ft (12 m) thick and interbedded with shales and coals, presented a more difficult problem.Petrologic analysis disclosed quartz sandstones in which the pore system consists mainly of large irregularly shaped dissolution pores. Diagenesis has destroyed primary porosity and precipitated authigenic illite, illite-smectite, kaolinite and siderite. The gas contains 32 per cent CO2 and is very dry. Temperatures are close to 400°F (200°C). The formations are overpressured.The project has drilled two wells, Big Lake 26 and 27, and applied two MHF treatments in Big Lake 26. One further MHF remains to be done in Big Lake 27. Each MHF treatment has been tailored to the particular petrologic, reservoir, stratigraphic, pressure and temperature conditions of that zone. The tailoring of MHF design has been further refined by running a 'mini-frac' with 10 000 gal (45 000 L) of fluid. MHF designs have involved up to 620 000 lb (280 000 kg) of sand, 60 000 lb (27 000 kg) of sintered bauxite and 300 000 gal (1350 kL) of gel. Having management on-site to react to aberrations and vary the design has been important in operations.One Tlrrawarra Sandstone MHF has been unsuccessful (as predicted) and the other, on initial results, appears highly successful. The Patchawarra Formation MHF speared off into a coal but appears moderately successful. Long-term flow tests will provide definitive results.Encouraged by these initial results, the Joint Venture Partners have drilled two further wells in the Big Lake Field which await MHF treatment. The gas-in-place is estimated at about 1.5 trillion cubic feet (42.5 billion cubic metres). Three other tight gas prospects of similar size, Burley, McLeod and Kirby, have been identified. The size of this potential resource provides a strong incentive to attempt to make MHF treatments economically viable in the Cooper Basin.

A Short Cut to Stabilized Gas Well Productivity

Here are simplified correlations that quickly provide correction factors for obtaining stabilized productivity from short-term flow tests. The only data needed to use the correlations are reservoir pressure, duration of test, and estimated permeability. Introduction For most studies involving gas wells and gas reservoirs, a very important consideration is the stabilized productivity or the ability to deliver gas for a productivity or the ability to deliver gas for a considerable time against a given backpressure. This knowledge is usually most needed in the early stages of development of an area, before extensive well test data or production information can be collected. Even in fields with considerable history, an engineer may frequently need a long-range performance prediction without having access to any data except the short-term test data normally required by state regulatory bodies. Short-term test data typified by a four-point back pressure with only 1 or 2 hours' flow on a point, or pressure with only 1 or 2 hours' flow on a point, or even a one-point 24-hour test may be grossly in error in low permeability reservoirs. Much of our nation's gas reserves is contained in the San Juan, Anadarko and Arkoma basins, which have the common characteristic of low permeability. In these areas it is not at all unusual for a well to require 30 days' flowing time to reach stabilization. Use of short-term test data for such wells would obviously lead to poor-quality estimates of either producing rates or reserves. The long-term flow test, to actually achieve stable flow, may be impractical for any of several reasons. The next best alternative would probably be two-rate flow tests. These require collection of detailed and closely controlled test data and can be costly even though much less time-consuming than the long-term flow to stable conditions. Another possible approach would be to determine interwell permeability and a skin factor from a pressure buildup test. Substitution of these factors with estimates of other reservoir parameters in the Darcy steady-state flow equation parameters in the Darcy steady-state flow equation would provide a reasonable estimate of stable flow capacity. In the absence of adequate field test data to define stabilized producing capacity, a stabilization factor to apply to short-term flow data would be useful; and that is the subject of this paper. For a stabilization factor to be most useful, it should be determinable with a minimum of field test data and calculation and still retain a reasonable degree of accuracy. Correlations have been developed that fulfill the requirement of minimum data and calculation. A check of the correlations with test data from several fields indicates a fair degree of accuracy. Basis for Correlations The well known Darcy steady-state flow equation neglecting turbulence may be written for gas wells as follows: (1) This equation and all others here are in practical field units and the terms are in the nomenclature. In the equation s is the skin factor defined by van Everdingen. JPT P. 537