Low Pumping Rates Research Articles

Stochastic Assessment of Nonpoint Source Contamination: Joint Impact of Aquifer Heterogeneity and Well Characteristics on Management Metrics

AbstractNonpoint source (NPS) groundwater contamination in sedimentary basin aquifers with overlying agricultural activities increasingly threatens groundwater supplies. The role of aquifer heterogeneity has not been well understood in the assessment of NPS and in linking pollution sources to impacts in water supply wells. A typical well taps into and mixes groundwater varying in age by decades or even centuries. This study investigates the joint impact of aquifer heterogeneity and pumping well characteristics (well depth, pumping rate, and screen length) on expected values of and uncertainty about key management metrics: (1) travel time of a NPS contaminant to a production well, (2) spatiotemporal characteristics of the source area, and (3) contaminant compliance at production wells. A stochastic approach is employed using Monte Carlo simulation of flow and nonreactive transport in 3‐D highly heterogeneous alluvial aquifer systems. Well design is shown to dominate the distribution of travel time mixing and the overall location and spread of the source area. Larger extraction intensity and closer proximity to the land surface are shown to significantly suppress effects of large aquifer heterogeneity on uncertainty on all metrics. Deep wells and wells with lower pumping rates have more uncertain source areas. Long‐term NPS contaminants with high source concentration (>10 times compliance level) will be exceeded in most wells within decades, while low‐intensity source concentrations (2–4 times compliance level, typical for nitrate and salinity) have large uncertainty about time to exceedance suggesting wide variability among a set of wells with similar well design subject to the same NPS pollution.

Insufficient slow-flow suppression mimicking aneurysm wall enhancement in magnetic resonance vessel wall imaging: a phantom study.

MR vessel wall imaging (VWI) is increasingly performed in clinical settings to support treatment decision-making regarding intracranial aneurysms. Aneurysm wall enhancement after contrast agent injection is expected to be related to aneurysm instability and rupture status. However, the authors hypothesize that slow-flow artifacts mimic aneurysm wall enhancement. Therefore, in this phantom study they assess the effect of slow flow on wall-like enhancement by using different MR VWI techniques. The authors developed an MR-compatible aneurysm phantom model, which was connected to a pump to enable pulsatile inflow conditions. For VWI, 3D turbo spin echo sequences-both with and without motion-sensitized driven equilibrium (MSDE) and delay alternating with nutation for tailored excitation (DANTE) preparation pulses-were performed using a 3-T MR scanner. VWI was acquired both before and after Gd contrast agent administration by using two different pulsatile inflow conditions (2.5 ml/sec peak flow at 77 and 48 beats per minute). The intraluminal signal intensity along the aneurysm wall was analyzed to assess the performance of slow-flow suppression. The authors observed wall-like enhancement after contrast agent injection, especially in low pump rate settings. Preparation pulses, in particular the DANTE technique, improved the performance of slow-flow suppression. Near-wall slow flow mimics wall enhancement in VWI protocols. Therefore, VWI should be carefully interpreted. Preparation pulses improve slow-flow suppression, and therefore the authors encourage further development and clinical implementation of these techniques.

Proof‐of‐Concept Modeling of a New Groundwater Sampling Approach

AbstractThis note provides a proof‐of‐concept modeling study to examine the theoretical feasibility of a new groundwater sampling approach, the high‐stress low‐flow approach, for improving the representativeness of groundwater samples and shortening the sampling duration. The approach consists of two‐phase pumping: an initial high pumping rate followed by low‐flow purging and sampling. We conceptualize the sampling process by pumping in a fully penetrating, large‐diameter well in a confined aquifer and mixing within the well screened zone, which are characterized by the aquifer‐responding time scale for aquifer water dominating the inflow ratio and the well‐mixing time scale, respectively. We derive an analytical solution to evaluate the sample concentration and representativeness. Results show that higher pumping rates in phase 1 create larger drawdowns and overstressed flow fields when switching to lower pumping rates in phase 2, thereby slowing down the drawdown within the well and preventing downward movement of the well casing water. As a result, the ratio of aquifer water into the well screened zone and in water pumped can rise sharply at the pumping‐switch moment, and the aquifer‐responding time scale and groundwater sampling duration can be significantly shortened. The proposed high‐stress low‐flow approach is particularly effective in systems limited by long aquifer‐responding time scales, which are typically encountered in low‐permeability aquifers. Based on the analytical solution, we also provide preliminary guidelines and graphic tools to select the pumping rate ratio and the switching time. Our proof‐of‐concept modeling study demonstrates great potential of the new groundwater sampling approach in field applications.

On collective Rabi splitting in nanolasers and nano-LEDs.

We analytically calculate the optical emission spectrum of nanolasers and nano-LEDs based on a model of many incoherently pumped two-level emitters in a cavity. At low pump rates, we find two peaks in the spectrum for large coupling strengths and numbers of emitters. We interpret the double-peaked spectrum as a signature of collective Rabi splitting, and discuss the difference between the splitting of the spectrum and the existence of two eigenmodes. We show that an LED will never exhibit a split spectrum, even though it can have distinct eigenmodes. For systems where the splitting is possible, we show that the two peaks merge into a single one when the pump rate is increased. Finally, we compute the linewidth of the systems, and discuss the influence of inter-emitter correlations on the lineshape.

Significance of the nonlocal optical response of metal nanoparticles in describing the operation of plasmonic lasers

A metal nanoparticle (MNP) coupled to a quantum emitter (QE) is a versatile composite nanostructure with unique chemical and physical properties which has been studied intensively, owing to its vast range of promising applications in nanoscience and nanotechnology. When pumped into a higher gain level, an MNP-QE composite nanostructure functions as a nanoplasmonic counterpart of a conventional laser, which is capable of operating at subwavelengths. The theory of plasmonic lasers is hitherto developed on the local optical response of the MNP, disregarding the nanoscale effects of its free electrons. In this paper, we perform a comprehensive quantum mechanical analysis of a complex MNP-QE composite nanostructure, capturing the size-dependent nonclassical effects through the nonlocal optical response of the MNP. Our study reveals that the nonlocal correction introduces significant deviations to the plasmon statistics of the hybrid particle suggested by the local calculations, becoming more prominent when the number of QEs coupled to the MNP increases. Furthermore, for the typical material parameter values used in the literature, we observed the initiation of quenching effects at lower pumping rates than suggested by the local response formalism. In essence, nonlocally assessed plasmon statistics of MNP-QE composite nanostructures demand the concerted coupling of an even higher number of QEs to compensate the deterioration in coherence and to sustain lasing.

Suction caissons in dense sand, part I: installation, limiting capacity and drainage

Suction caissons are a promising foundation concept for supporting offshore wind turbines. Compared to applications in the oil and gas industry, where most practical experience exists, significant differences arise in terms of load paths and magnitudes, soil type and caisson aspect ratio (skirt length to diameter). In a set of two companion papers, this contribution investigates the response of suction caissons in dense sand through a series of centrifuge experiments. The caisson was installed using suction, followed by sequences of cyclic loading and then extraction, all steps completed continuously in-flight. This first paper discusses installation, limiting capacities and drainage, whereas the second paper focuses on vertical cyclic loading into tension. The work demonstrates that suction caisson installation behaviour is well described by existing calculation methods. Tests performed at different installation rates demonstrate that careful assessment of the pumping rate is needed to ensure successful installation, with low pumping rates resulting in premature refusal. In the centrifuge tests, full skirt penetration was achieved without apparent loosening of the soil plug. The limiting capacity in tension, measured during the testing at both fast and slow uplift rates, was also well described by existing calculation methods.

Characteristics of fracture propagation in compact limestone formation by hydraulic fracturing in central Sichuan, China

Compact limestone formations are significant and serve as enrichment petroleum sources in the central Sichuan basin. However, they are difficult to stimulate by hydraulic fracturing owing to their low porosity, low permeability, and high density. The fracture geometry is neither a bi-wing fracture found in a homogeneous sandstone formation nor a complex fracture network occurring in a shale formation with well-developed discontinuities and high brittleness. In this study, a series of laboratory stimulated experiments were conducted to investigate the fracture initiation and propagation behavior in compact limestone formation. Concurrently, the effects of the horizontal stress difference, pump rate, fracturing fluid viscosity, and completion method were also studied. The results revealed that a complex fracture network was formed with difficultly in a compact limestone formation. The fractures initiated from open-hole section or perforations to propagate in four forms, resulting in three categories of the main fracture geometry: transverse fracture, longitudinal fracture, and complex fracture. Complex fracture formations occurred under a small horizontal stress difference, whereas a simple fracture was induced by a large horizontal stress difference, similar to a transverse or longitudinal fracture. Moreover, the cement strength, development degree, and distribution position of the discontinuities had a significant effect on the fracture geometry. A low fluid viscosity or low pump rate was demonstrated to be an effective method for activating and opening the discontinuities, forming complex fractures under a small horizontal stress difference rather than under a large horizontal stress difference. However, the variable pump rate fracturing with a low-viscosity fluid could promote the interaction of the induced fracture and discontinuities, leading to a large stimulated reservoir volume under the large horizontal stress difference. In addition, perforated fracturing generated a more complex fracture at a higher fracture pressure than an open-hole fracturing. Furthermore, an acid fluid should be injected into limestone formation before the fracturing operation to reduce the rock strength, resulting in a low fracture pressure of limestone formation.

Coupling of Gain Medium and Extraordinary Optical Transmission for Effective Loss Compensation

Gain mediums attract much attention due to their excellent amplification characteristics. However, the potential applications of gain mediums are severely limited because of the requirement of a high external energy to excite the media, thereby compensating for the ohmic loss. In this paper, we developed a theoretical model by numerically solving the coupled Maxwell’s equations and semiclassical electronic rate equations using the finite-difference time-domain method. In the model, the active gain medium is represented by a four-level atomic system, and the atoms are pumped with a homogeneous pumping rate. Then, we investigated the loss compensation with the synergetic effects of gain mediums and extraordinary optical transmission (EOT) phenomena caused by the excitation of the surface plasmon polariton. With the proposal of a novel gain/metal/gain structure that is patterned to be a periodic subwavelength hole array, the self-consistent process of EOT phenomena coupled to the gain medium enables full compensation of the ohmic loss under a much lower pumping rate. This paper not only presents a novel structure but also provides deep insight into the interaction between nanostructures and gain mediums.

Enhancing the spatial coverage of a regional high-quality hydraulic conductivity dataset with estimates made from domestic water-well specific-capacity tests

The spatial coverage of hydraulic conductivity (K) values for large-scale groundwater investigations is often poor because of the high costs associated with hydraulic testing and the large areas under investigation. Domestic water wells are ubiquitous and their well logs represent an untapped resource of information that includes mandatory specific-capacity tests, from which K can be estimated. These specific-capacity tests are routinely conducted at such low pumping rates that well losses are normally insignificant. In this study, a simple and practical approach to augmenting high-quality K values with reconnaissance-level K values from water-well specific-capacity tests is assessed. The integration of lesser quality K values from specific-capacity tests with a high-quality K data set is assessed through comparisons at two different scales: study-area-wide (a 600-km2 area in Ontario, Canada) and in a single geological formation within a portion of the broader study area (200 km2). Results of the comparisons demonstrate that reconnaissance-level K estimates from specific-capacity tests approximate the ranges and distributions of the high-quality K values. Sufficient detail about the physical basis and assumptions that are invoked in the development of the approach are presented here so that it can be applied with confidence by practitioners seeking to enhance their spatial coverage of K values with specific-capacity tests.

Intensified antibunching via feedback-induced quantum interference

We numerically show that time delayed coherent feedback controls the statistical output characteristics of driven quantum emitters. Quantum feedback allows to enhance or suppress a wide range of classical and nonclassical features of the emitted quantum light. As exemplary quantum system, we use a pumped cavity containing two emitters. By applying phase-selective feedback, we demonstrate that photon antibunching and bunching can be increased in orders of magnitude due to intrinsically and externally controllabe quantum interferences. Our modelling is based on a fully non-Markovian quantum simulation of a structured photon continuum. We show that an approximative method in the Schr\"odinger picture allows a very good estimate for quantum feedback induced features for low pump rates.

Hydrogeology of the Judith River Formation in southwestern Saskatchewan, Canada

The Judith River Formation forms an important regional aquifer in southwestern Saskatchewan, Canada. This aquifer is used for domestic and agricultural purposes in some areas and supports oil and gas production in other areas. As a result, the available data come from a range of sources and integration is required to provide an overview of aquifer characteristics. Here, data from oil and gas databases are combined with data from groundwater resource assessments. Analysis of cores, drill-stem tests and pumping tests provide a good overview of the physical hydrogeology of the Judith River Aquifer. Water chemistry data from oil and gas databases were less helpful in understanding the chemical hydrogeology due contamination of samples and unreliable laboratory analyses. Analytical modeling of past pumping in the aquifer indicates that decreases in hydraulic head exceeding 2 m are possible over distances of 10s of kilometers. Similar decreases in head should be expected for additional large withdrawals of groundwater from the Judith River Aquifer. Long-term groundwater abstraction should be limited by low pumping rates. Higher pumping rates appear to be possible for short-term uses, such as those required by the oil and gas industry.

Hydraulic Fracture Growth in a Layered Formation based on Fracturing Experiments and Discrete Element Modeling

Hydraulic fracture (HF) height containment tends to occur in layered formations, and it significantly influences the entire HF geometry or the stimulated reservoir volume. This study aims to explore the influence of preexisting bedding planes (BPs) on the HF height growth in layered formations. Laboratory fracturing experiments were performed to confirm the occurrence of HF height containment in natural shale that contains multiple weak and high-permeability BPs under triaxial stresses. Numerical simulations were then conducted to further illustrate the manner in which vertical stress, BP permeability, BP density(or spacing), pump rate, and fluid viscosity control HF height growth using a 3D discrete element method-based fracturing model. In this model, the rock matrix was considered transversely isotropic and multiple BPs can be explicitly represented. Experimental and numerical results show that the vertically growing HF tends to be limited by multi-high-permeability BPs, even under higher vertical stress. When the vertically growing HF intersects with the multi-high-permeability BPs, the injection pressure will be sharply reduced. If a low pumping rate or a low-viscosity fluid is used, the excess fracturing fluid leak-off into the BPs obviously decreases the rate of pressure build up, which will then limit the growth of HF. Otherwise, a higher pumping rate and/or a higher viscosity will reduce the leak-off time and fluid volume, but increase the injection pressure to drive the HF to grow and to penetrate through the BPs.

In-well time-of-travel approach to evaluate optimal purge duration during low-flow sampling of monitoring wells

A common assumption with groundwater sampling is that low (<0.5 L/min) pumping rates during well purging and sampling captures primarily lateral flow from the formation through the well-screened interval at a depth coincident with the pump intake. However, if the intake is adjacent to a low hydraulic conductivity part of the screened formation, this scenario will induce vertical groundwater flow to the pump intake from parts of the screened interval with high hydraulic conductivity. Because less formation water will initially be captured during pumping, a substantial volume of water already in the well (preexisting screen water or screen storage) will be captured during this initial time until inflow from the high hydraulic conductivity part of the screened formation can travel vertically in the well to the pump intake. Therefore, the length of the time needed for adequate purging prior to sample collection (called optimal purge duration) is controlled by the in-well, vertical travel times. A preliminary, simple analytical model was used to provide information on the relation between purge duration and capture of formation water for different gross levels of heterogeneity (contrast between low and high hydraulic conductivity layers). The model was then used to compare these time–volume relations to purge data (pumping rates and drawdown) collected at several representative monitoring wells from multiple sites. Results showed that computation of time-dependent capture of formation water (as opposed to capture of preexisting screen water), which were based on vertical travel times in the well, compares favorably with the time required to achieve field parameter stabilization. If field parameter stabilization is an indicator of arrival time of formation water, which has been postulated, then in-well, vertical flow may be an important factor at wells where low-flow sampling is the sample method of choice.

Numerical study on upconversion random lasing in strong scattering disordered medium

The upconversion random lasing properties in two-dimensional (2D) disordered medium was studied. Based on the time-dependent theory, a model for upconversion random laser was established. The Maxwell equations and rate equations were combined and solved by using the finite different time domain (FDTD) method. Results show that the emission at 381nm is determined by the pumping intensity. For low pumping rates, the 381nm signal is mainly contributed from the transition 4D3/2→4I11/2 while the transition 4D7/2→4I13/2 is negligible. When the pumping rate increases to a certain value, the intensity of these two upconversion signals are comparable. The duration of the pulse from the transition 4D7/2→4I13/2 is short while the emission from 4D3/2→4I11/2 has a long fall time. As the pumping rate increases, the width and the peak interval of two pulses will decrease simultaneously. The simulation results may provide a control method of upconversion random lasers.

English

Pumping of 82 MCM/yr from Mujib Basin (Eastern Dead Sea), coupled with the 54 MCM/yr recharge rate, has led to diminished groundwater levels and dramatically affects ecosystem services. Climate change compounds these issues by reducing recharge and increasing the ecosystem&rsquo;s hydrological demand. This paper investigates groundwater resilience to climatic changes in Mujib Basin by modeling resilience for the years 2014 and 2050. Resilience of groundwater was modeled to long term changes as &ldquo;low&rdquo; in the central parts of the study area due to low saturated thickness and high pumping rates. Resilience was modeled as &ldquo;high&rdquo; to &ldquo;very high&rdquo; in areas with high saturated thickness and higher replenishment rates. Water budget components were modeled through the J2000 hydrological model, giving a groundwater recharge of 54 MCM/yr. Statistical downscaling of global circulation models indicated a 21% decline in precipitation by the year 2080 with 2 and 3&deg; increases in maximum and minimum temperature respectively. Recharge for the year 2050 was recalculated based on the downscaling and prediction results to be 30% less than current recharge. Continuous over-pumping with recharge reduction will cause a 30-70% reduction in saturated thickness by the same year. Modeling groundwater resilience under the new conditions showed a severe impact on the study area especially the central parts which are expected to comprise a semi dry aquifer by 2050. &nbsp; Key words: Jordan, Dead Sea, groundwater resilience, climate change.

Multilayer stress field interference in sandstone and mudstone thin interbed reservoir

General fracturing and separate layer fracturing play an important role in sandstone and mudstone thin interbed (SMTI) reservoirs, where one of the main issues is to control the excessive height growth of fracturing. The fracture propagation at the interface depends on the induced stress produced by the hydraulic fracturing construction. This paper employed a poroelastic coupled damage element with the cohesive zone method (CZM) to establish a 2D fracture quasi-static propagation model. A parametric study was performed under different fracture height, fracture width, pumping rate, fluid viscosity, in situ stress, elastic modulus and tensile strength with this model. General fracturing and separate layer fracturing are compared with each other through fracture morphology and induced stress. The simulation results show that the absolute value of induced stress increases with the decrease in matrix stress near the fracture tip. As a result, the propagation of the fractures is much easier due to the weakened degree of compression. The growth of fracture height and width, the increase in pumping rate and the excessively large or small value of fluid viscosity lead to larger induced stress on the interface. Higher in situ stress, lower elastic modulus, and higher tensile strength of the interlayers can control the excessive height growth of fracturing. The simulated results also show that the fractures are more likely to be overlapped with each other in general fracturing compared to that in separate-layer fracturing. Results of the simulations suggest that lower pumping rates, the proper value of fluid viscosity, separate layer fracturing and interlayers with higher in situ stress, lower elastic modulus and higher tensile strength tend to limit fracture height. Finally, the proposed model was applied to a practical oil field case to verify its effectiveness.

EVALUATION ON THE APPLICATIONS OF SMALL SIZE COILED TUBING IN WELL SERVICES

Today, one of the most important key for hydrocarbon production in the oil &amp; gas industry is economic justification. In the later state of the well’s production, the aging wells may introduce many problems such as scale, sand and liquid load-up. These impede the hydrocarbon production, preventing all the reserve to be fully produced. In order to fight this impedance, the use of small size coiled tubing is a promising practice, although has its own limit. The objective of this paper is to evaluate the limit of well services applications of small size Coiled Tubing (1" and 1.25") in various oil &amp; gas well scenarios. The evaluation utilizes the computer modeling which is used to determine the hydraulic and mechanic operating conditions. Our study found the viability of 1” CT in the low inclination well scenarios with the lower pumping rate requirement, while 1.25” CT can be used in all of well services applications and scenarios.

Entanglement properties of quantum polaritons

Exciton polaritons are coupled states of matter and light, originated by the strong interaction between an optical mode and semiconductor excitons. This interaction can be obtained also at a single-particle level, in which case it has been shown that a quantum treatment is mandatory. In this work we study the light-matter entanglement of polaritons from a fully quantum formalism including pumping and dissipation. We find that the entanglement is completely destroyed if the exciton and photon are tuned at the resonance condition, even under very low pumping rates. Instead, the best condition for maximizing entanglement and purity of the steady state is when the exciton and photon are out of resonance and when incoherent pumping exactly compensates the dissipation rate. In the presence of multiple quantum dots coupled to the light mode, matter-light entanglement survives only at larger detuning for a higher number of quantum dots considered.

A new approach in skin effect and storativity estimation from pumping test data with low pumping rates [abstract

A new approach in skin effect and storativity estimation from pumping test data with low pumping rates [abstract

Shortcomings of the RBF Pilot Site in Dishna, Egypt

AbstractThis work describes the reasons and circumstances concerning why researchers came up short at the Dishna riverbank filtration (RBF) pilot site in Egypt, which—1.5 years after construction—has yet to deliver at least 40% of the bank filtrate. Limited site investigation, intermittent well operation, low pumping rates, and Egyptian drinking water well design regulations have been identified as main reasons for less than 10% bank filtrate. The authors draw on experience and lessons learned to develop recommendations for RBF site investigations and implementation on a limited budget. The investigations require a minimum investment of 20,000 Egyptian pounds and at least 1.5 years’ time per site. A generalized RBF well design is proposed for sites with scarce data or areas where groundwater is of low quality and unsuitable for potable supply.