Pumping Rate Research Articles

Experimental Research on the Proppant Settling and Transport Characteristics of Silica Gel-Based Fracturing Fluid

Summary Hydraulic fracturing is an effective stimulation method to establish high-conductivity channels in tight reservoirs, and the effectiveness of man-made fractures largely depends on the proppant-carrying capacity of the fracturing fluids used. As a novel completion fluid, silica gel-based fracturing fluids have shown desirable stimulation effect in application cases, but a comprehensive evaluation of their proppant settling and transport behaviors in the laboratory remains lacking. In this paper, a silica gel-based fracturing fluid was prepared first, and then the rheological properties, including shear thinning, recovery behavior, and viscoelasticity of the fluid system, were measured. Afterward, the settling velocity of single-particle proppant and the settling rate of multiparticle proppant under various experimental conditions were investigated in the static fluid system; in addition, the dynamic proppant-carrying performance was evaluated using a visualized rough fracture model to study different factors on the dune distribution inside the fractures. Lastly, the proppant-carrying mechanism of silica gel-based fracturing fluid was revealed in three aspects. The rheological test result showed that the shear viscosity of silica gel-based fracturing fluid increased as the SiO2 concentration increased. Furthermore, all tested fluid samples exhibited an elastic modulus that is consistently greater than the viscous modulus, indicating that the silica gel-based fracturing fluid system has a dominant elastic response behavior. In the single-particle static settling test, there was a significant increase in the settling velocities as the particle diameter increased and as the temperature increased. Meanwhile, the settling rate of multiparticles showed a decreasing trend with the increase in mesh size, while the proppant settling rate gradually increased as the proppant concentration rose. The results of dynamic proppant-carrying experiments demonstrate that a higher pumping rate leads to an extended migration distance for proppant, resulting in formed sand dunes with reduced height within fractures. Conversely, an increase in proppant concentration and a reduction in mesh size tend to form higher sand dunes. The proppant-carrying mechanisms of the silica gel-based fracturing fluid relate to the self-polymerization and syneresis of silica gel, the noticeable elasticity characteristics, and the structural encapsulation effect formed between silica gel and proppant. A better understanding of the proppant settling and transport behaviors of silica gel-based fracturing fluid can be helpful in optimizing the hydraulic fracturing design and promoting field application.

Modeling the Pumping Behavior of Macroscopic Lead Structures on Shaft Counterfaces of Rotary Shaft Seals

The leak tightness of the sealing system rotary shaft seal is based on the formation of an active back-pumping effect of the sealing ring. Here, the sealing ring pumps the fluid in the sealing gap back into the housing. However, this active sealing mechanism is disturbed by so-called “lead structures”. Lead structures include all types of directional structures on the sealing counterface which create rotation-dependent axial fluid pumping. Lead-affected sealing counterfaces can thus cause leakage or insufficient lubrication of the sealing contact. To ensure leak tightness, lead must be avoided or tolerated. This article investigates how different structural characteristics of lead affect the amount of fluid pumped by the shaft surface. For this purpose, 26 shafts are subjected to surface analyzing methods and an experimental pumping rate test. The interaction of various geometric features of the lead structures and their combined effect on the pumping capacity is modeled based on the measured data. Appropriated correlation models are discussed and relationships between shaft lead and its pumping effect are shown. The aim is to estimate shaft pumping rates based on surface measurements in future. The results contribute to the derivation of measurable tolerance values for lead and to the prevention of leakage.

A construction strategy of Kriging surrogate model based on Rosenblatt transformation of associated random variables and its application in groundwater remediation

When using simulation-optimization models for optimizing the design of groundwater pumping-treatment plans for pollution, building a surrogate model for the numerical simulation model has become an effective means of overcoming the computational load of such models. However, previous studies often treated pumping time as a single optimization variable, leading to unnecessary excessive pumping. This paper considers the location, pumping rate, start time, and end time of each candidate pumping well as optimization variables, and proposes a Rosenblatt-transform-based optimal Latin hypercube sampling method for the associated random variables to ensure that the start time is less than or equal to the end time. This method is coupled with an adaptive sampling method based on batch local optimal solutions to construct a dynamic adaptive Kriging surrogate model for the numerical model, ensuring that the true value of the optimal remediation scheme is not lost. The results show that, at the final stage of remediation, the pollutant concentration in the 4 scenarios achieves comprehensive compliance. However, when considering the minimization of remediation costs as the evaluation criterion, the remediation scheme in scenario 1 (the pumping start and end times are independent optimization variables for all candidate pumping wells) is optimal. In the optimization design of groundwater pumping-treatment plans, the pumping wells should be arranged in the midstream and downstream regions of the contaminant plume and parallel to the regional flow direction. This paper provides a method reference for the construction and adaptive updating of surrogate models involving associated random variables, as well as guidance for the dynamic optimization of groundwater pumping and treatment at contaminated sites.

Optimization of pumping and injection regimes for mitigation of seawater intrusion

Seawater intrusion (SWI) stands as a significant challenge impacting coastal aquifers worldwide. The emergence of SWI is a natural phenomenon owing to the density difference between seawater and freshwater. Even without any pumping, the seawater naturally advances inland until a hydrostatic equilibrium between the two water sources is reached. However, human interventions, such as excessive groundwater extraction, coastal developments, and land use as well as climate change intensify the SWI predicament. Efficient solutions to counteract the SWI problem involve the implementation of hydraulic barriers. By employing the Henry problem as a benchmark, the Finite Element Simulator (FEFLOW), which is a numerical modeling software, was used for simulating the flow and transport processes. An integrated FEFLOW-Python code was developed to optimize hydraulic barriers for mitigating SWI. The methodology aims to achieve the maximum possible reduction in SWI by iteratively adjusting the locations and rates of pumping and injection wells. Unlike other investigations, this study explores the utilization of negative SWI barriers to extract brackish water from the dispersion zone and potentially offer a cost-effective alternative water source for desalination plants’ intakes. For the Henry Problem, to maximize the reduction in of SWI, brackish water extraction wells should be situated near the center-bottom of the intrusion zone, with a pumping rate of 2.5 m3/day. For injection wells, the optimal location varies depending on the injection rate (I). Achieving the highest retardation (61%) occurs when the injection rate is 1 m3/day, positioned at the aquifer’s bottom and close to the coastal boundary. However, for injection rates below 0.7 m3/day, the injection well’s optimal location shifts towards the seawater intrusion toe. This study presents a novel approach by establishing explicit correlations for optimizing hydraulic barriers to effectively manage and mitigate SWI.

Early-life caffeine exposure induces morphological changes and altered physiology in Caenorhabditiselegans

Caffeine, a widely consumed stimulant, is known for its effects on alertness and fatigue reduction by blockade of adenosine receptors. While it holds therapeutic potential, its diverse impacts pose risks, particularly in early development. This study explores the developmental effects of caffeine exposure using Caenorhabditis elegans (C. elegans) as a model organism. We investigated morphological and behavioral changes induced by caffeine exposure at the L1 stage and assessed their impact at the L4 stage, which roughly corresponds to human infancy and adolescence, respectively. Caffeine-exposed worms displayed increased body length, body bends, and pharyngeal pumping rates compared to control worms. These findings indicate heightened food-seeking behavior and greater food intake, leading to the observed morphological changes. While caffeine did not affect other locomotor behaviors, its stimulatory effect on growth and development highlights its significance. This study provides insights into the potential impact of early-life caffeine exposure on long-term health and development, offering a foundation for future research in vertebrates to uncover its implications on metabolism and other metrics of health.

Sitagliptin Extends Lifespan of Caenorhabditis elegans by Inhibiting Insulin/Insulin-Like Signaling and Activating Dietary Restriction-Like Signaling Pathways

Introduction: The discovery of longevity molecules that delay aging and prolong lifespan has always been a dream of humanity. Sitagliptin phosphate (SIT), an oral dipeptidyl peptidase-4 (DPP-4) inhibitor, is an oral drug commonly used in the treatment of type 2 diabetes (T2D). In addition to being antidiabetic, previous studies have reported that SIT has shown potential to improve health. However, whether SIT plays a role in the amelioration of aging and the underlying molecular mechanism remain undetermined. Methods: Caenorhabditis elegans (C. elegans) was used as a model of aging. Lifespan assays were performed with adult-stage worms on nematode growth medium plates containing FUdR with or without the specific concentration of SIT. The period of fast body movement, body bending rates, and pharyngeal pumping rates were recorded to assess the healthspan of C. elegans. Gene expression was confirmed by GFP fluorescence signal of transgenic worms and qPCR. In addition, the intracellular reactive oxygen species levels were measured using a free radical sensor H2DCF-DA. Results: We found that SIT significantly extended lifespan and healthspan of C. elegans. Mechanistically, we found that several age-related pathways and genes were involved in SIT-induced lifespan extension. The transcription factors DAF-16/FOXO, SKN-1/NRF2, and HSF-1 played important roles in SIT-induced longevity. Moreover, our findings illustrated that SIT-induced survival benefits by inhibiting the insulin/insulin-like signaling pathway and activating the dietary restriction-related and mitochondrial function-related signaling pathways. Conclusion: Our work may provide a theoretical basis for the development of anti-T2D drugs as antiaging drugs, especially for the treatment of age-related disease in diabetic patients.

Comparison of the Shutdown Transitions of the Full-Flow Pump and Axial-Flow Pump

In this study, a comparative analysis of the shutdown transitions of a full-flow pump and an axial-flow pump was carried out through numerical simulation and model tests. The UDF method was used to achieve control of the impeller rotational speed during shutdown. The results show that during the shutdown transition, the rate of decline of rotational speed, flow rate, and torque of the axial-flow pump are greater than those of the full-flow pump, so the axial-flow pump stops faster than the full-flow pump. The axial force of the axial-flow pump is significantly lower than that of the full-flow pump, and the maximum value of the radial force of the axial-flow pump is approximately 1.14 times that of the full-flow pump. Due to the influence of the clearance backflow vortex, the impeller inlet and outlet of the full-flow pump generate clearance backflow vortices in the near-wall area, resulting in the overall flow pattern of the impeller chamber being worse than that of the axial-flow pump and the hydraulic loss being greater than that of the axial-flow pump. The runaway speed and flow rate of the axial-flow pump are higher than those of the full-flow pump. Due to the influence of the clearance backflow, the range of the high entropy production rate at the suction side of the impeller of the full-flow pump is always larger than that of the axial-flow pump. The research results in this paper can provide theoretical support for the selection and operation of pumps in large low-head pumping stations.

Novel Environmentally Friendly Nanomaterials for Drag Reduction of the Emulsified Acid System.

Matrix acidizing is a technique that is widely used in the petroleum industry to remove scales and create channels in the rock. Removal of scales and creation of channels (wormhole) enhance productivity. Conventional acidizing fluids, such as hydrochloric acid (HCl) for carbonate and a mixture of hydrofluoric acid (HF) and HCl acid, are used for the matrix acidizing process. However, these fluids have some drawbacks, including strong acid strength, corrosion at high temperatures, and quick reactions with scale and particles. Emulsified acid systems (EASs) are used to address these drawbacks. EASs can create deeper and narrower wormholes by reducing the reaction rate of the acid due to the external oil phase. However, EASs have a much higher viscosity compared to conventional acidizing fluids. The high viscosity of EASs leads to a high drag that restricts pumping rates and consumes energy. This study aims to utilize environmentally friendly and widely available nanomaterials as drag-reducing agents (DRAs) of the EAS. The nanomaterials used in this study are carbon nanodots (CNDs). CNDs have unique properties and are used in diverse applications in different industries. The size of these CNDs is usually smaller than 10 nm. CNDs are characterized by their biocompatibility and chemical stability. This study investigates the use of CNDs as DRAs for EAS. Several experiments have been conducted to investigate the CNDs as a DRA for the EAS. The developed EAS was initially tested for conductivity and drop-test analysis to ensure the formation of an inverted emulsion. Thereafter, the thermal stability for the range of temperatures and the rheological properties of the EAS were evaluated to meet the criteria of field operation. Then flow experiments with EASs were conducted before and after adding the CNDs to investigate the efficacy of drag reduction of EASs. The results revealed that CNDs can be used as viscosity reducers for the EAS, where adding the CNDs to the EAS reduces the viscosity at two different HCl concentrations (15 and 20%). It reduces the viscosity of the EAS in the presence of corrosion inhibitors as well as other additives to the EAS, showing its compatibility with the field formulation. The drag reduction was observed at the range of temperatures investigated in the study. The conductivity, stability, and rheology experiments for the sample taken after the flow experiment are consistent, ensuring CNDs work as a DRA. The developed EAS with CNDs is robust in terms of field mixing procedures and thermally stable. The CNDs can be used as a DRA with EAS, which will reduce drag in pipes, increasing pumping rates and saving energy.

Analysis of Steady Groundwater Flow in Confined Aquifer Due to Long-Strip Pit Dewatering with Suspended Cut-Off Wall

This study investigates the steady flow resulting from dewatering by a partially penetrating well in a confined aquifer with a cut-off barrier. By considering flow in both horizontal and vertical directions and incorporating the barrier and pumping well as flow boundary conditions, separate mathematical models are established for the inside and outside of the cut-off barrier. The interaction between these zones is ensured through continuous conditions along the opening of the two zones. A semi-analytical solution is derived for the problem using the finite Fourier cosine transform and boundary transformation methods. The effectiveness of the method is verified by comparing it with the finite element numerical results and pumping test data respectively. Based on the proposed solutions, we proceed to analyze the influence of some relevant factors: the extent to which the cut-off wall is embedded within the confined aquifer, the depth of the partially penetrating well, and the distance to the lateral head boundary. Results indicate that a greater depth of the cut-off wall leads to a reduced pumping rate requirement for achieving a desired drawdown of the confined water level within the excavation. According to the presented solution, placing pumping wells near the top of the confined aquifer in excavation dewatering projects can facilitate a faster reduction of the confined water head at the excavation bottom. Additionally, proximity of lateral head boundary could significantly impact dewatering, with closer boundaries reducing dewatering effectiveness due to improved aquifer recharge. Finally, the use of the Fourier method showcases impressive convergence properties in the approach presented in this study. The computed results maintain a high level of approximation quality, even with extremely coarse discretization.

Visual Laboratory Tests: Effect of Operational Parameters on Proppant Transport in a 3D Printed Vertical Hydraulic Fracture with Two-Sided Rough Surfaces

Summary Hydraulic fracturing technology is an effective measure that can improve oil and gas production and achieve enormous economic benefits owing to it phenomenally increasing the oil recovery from the low intrinsic permeability of the compact rock. Good placement and distribution of the proppant in the hydraulic fractures can provide successful stimulation for a well, which is essential for applying the hydraulic fracturing process. Previous studies extensively explored proppant placement, distribution, and operational factors in simplified smooth surface fracture models. However, the operational factors such as pump rate, proppant concentration, proppant size, fluid viscosity, and inlet condition (pulse time) involved in proppant placement and distribution in realistic rough surfaces of fractures are not clearly understood. In particular, the law of proppant transport in a two-sided rough surface of fracture with changes in the aforementioned operational factors was unclear. Hence, in this study, we investigated the effect of these operational factors on proppant placement and transport in both the smooth surface fracture model and the two-sided rough surface fracture model. The results suggested that the traditional law of proppant transport drawn on the smooth surface fracture model did not apply to the two-sided rough surface model. It is suggested that selecting corresponding variables was needed to reduce the risk of proppant bridging and offer a better channel ratio.

Research on renewable energy coupling system based on medium-deep ground temperature attenuation

Medium-deep geothermal has large reserves, a high temperature, a high heat flow density, and other characteristics, but the traditional medium-deep ground heat pump system have long relied on heating from the ground, and soil temperature decreases annually. Using a community building heating system as an example, from a point of view of heat accumulation or not, this article examines the design of a photovoltaic photothermal coupled medium-deep ground source heat pump system (PV/T-GSHP) and a photovoltaic-assisted medium-deep ground source heat pump coupled air source heat pump system (PVGSHP-ASHP). First, the operational performance of a typical GSHP system was compared to that of the PV/T-GSHP and PVGSHP-ASHP systems, both of which were built using TRNSYS. Second, the energy balance and electrical consumption of each system were compared. Finally, the effect of the PV/T-GSHP system’s key parameters and the different ASHP load ratios in the PVGSHP-ASHP system on soil temperature were analyzed. The results showed that after 20 years of operation, the average soil temperature decreased from 38.29 °C to 36.89 °C for the GSHP system, resulting in a decrease in the performance coefficient of the ground source heat pump and the system performance coefficient. The PV/T-GSHP system can address the issue of declining soil temperature with an increase in soil temperature of 0.09 °C. The PVGSHP-ASHP system can mitigate the issue of decreasing soil temperature. The PVGSHP-ASHP system is better than the PV/T-GSHP system in terms of electricity economy. In the PV/T-GSHP system, the larger PV/T component area of similar structures, the smaller flow rate of the heat collector pump, and the volume, inclination, and set temperature of the heat storage tank that are more suitable for the system can achieve higher soil temperatures. As the air-source load ratio increases, the rate at which the soil temperature in the PVGSHP-ASHP system decreases progressively decelerates.

New formulations and experimental validation of non-stationary convolutions for the fast simulation of time-variant flowrates in ground heat exchangers

Flowrate control can have a significant positive impact on the thermal performance and economic profitability of ground-source heat pump systems. Including dynamic advective processes in the design phase, however, remains a challenging task, as few computationally efficient modeling tools allow for their adequate and accurate representation. The present work addresses this issue by presenting new formulations of non-stationary convolutions, an efficient simulation algorithm that relies on the theory of linear time-variant systems for predicting the thermal response of a ground heat exchanger to both dynamic heat loads and flow rates. First, the new original formulations are presented, which include (1) a simple time-domain expression and (2) a fast frequency-domain expression. Then, the efficiency and validity of the new formulations are verified using experimental multi-flowrate thermal response tests involving dynamic circulation, pumping and bleed flow rates in closed-loop and standing column well ground heat exchangers. Results show that the new formulations can reproduce the outlet fluid temperature of both experimental test cases with good accuracy ( MAE = 0.06 ∘ C and 0.26 ∘ C , respectively). At last, the high efficiency of the new frequency-domain expression is demonstrated, with the computing times ( 0.04 s and 0.01 s ) being 100 and 8 times faster than the original formulation in both scenarios.

Lab Experiments for Abrasive Waterjet Perforation and Fracturing in Offshore Unconsolidated Sandstones

Multistage hydraulic fracturing has been proven to be an effective stimulation method to extract more oil from the depleted unconsolidated sandstone reservoirs in Bohai Bay, China. The offshore wellbores in this area were completed with a gravel pack screen that is much too difficult to be mechanically isolated in several stages. Hydra-jet fracturing technology has the advantages of multistage fracturing by one trip, waterjet perforation, and hydraulic isolation. The challenges of hydraulic-jet fracturing in offshore unconsolidated sandstone reservoir can be summarized as follows: the long jet distance, high filtration loss, and large pumping rate. This paper proposes full-scale experiments on the waterjet perforation of unconsolidated sandstone, waterjet penetration of screen liners and casing, and pumping pressure prediction. The results verified that multistage hydra-jet fracturing is a robust technology that can create multiple fractures in offshore unconsolidated sandstone. Lab experiments indicate that the abrasive water jet is capable to perforate the screen-casing in less than one minute with an over 10 mm diameter hole. The water jet perforates a deep and slim hole in unconsolidated sandstone by using less than 20 MPa pumping pressure. Recommended perforating parameters: maintain 7% sand concentration and perforate for 3.0 min. Reduce sand ratio to 5%, maintain 3.0 m3/min flow rate, and continue perforating for 7.0 min. The injection drop of the nozzle accounts for more than 62% of the tubing pump pressure. The recommended nozzle combinations for different fracturing flow rates are 8 × ø6 mm or 6 × ø7 mm for 2.5 m3/min and 3.0 m3/min, and 8 × ø7 mm for 3.5 m3/min and 4.0 m3/min. A one-trip-multistage hydra-jet fracturing process is recommended to be used for horizontal wells in offshore unconsolidated sandstone reservoirs.

Catalytic wet air oxidation of phenol over nano mesoporous lanthanum oxide synthesized by chitosan template method

The study investigates the effectiveness of nano mesoporous lanthanum oxide (La2O3), synthesized by the chitosan template method, as a catalyst for the wet air oxidation of phenol (WAO). To relate the performance of the synthesized La2O3 to its chemical and textural characteristics, it was subjected to a thorough characterization using various analytical techniques, including TG-DTG, XRD, FTIR, BET, TEM, TPD-CO2, TPD-NH3, and H2-TPR. Nanomesoporous La2O3 displayed remarkable efficiency in removing phenol and total organic carbon (TOC) while exhibiting a greater preference towards non-organic compounds. Significant improvement in removal efficiency and selectivity when compared to non-catalytic wet air oxidation is observed for the catalyst. The study investigated the impact of temperature, catalyst dosage, airflow, and phenol pumping rate on the catalytic wet air oxidation (CWAO) of phenol. Even after 6 h of continuous reaction, La2O3 exhibited exceptional catalytic stability. The mesoporous nature and presence of Lewis basic sites in nano-La2O3 may be crucial in facilitating the degradation of phenol and enhancing the efficiency of TOC removal. The study concludes that the chitosan template method is an effective approach for synthesizing nano mesoporous lanthanum oxide, which could be used as a promising catalyst for the treatment of phenol-containing wastewater.

Dimensionless Thermal Efficiency Analysis for Aquifer Thermal Energy Storage

AbstractSeasonal warm and cold water storage in groundwater aquifers is a cost‐effective renewable energy technology for indoor heating and cooling. Simple dimensionless analytical solutions for the thermal recovery efficiency of Aquifer Thermal Energy Storage (ATES) systems are derived, subject to heat losses caused by thermal diffusion and mechanical dispersion. The analytical solutions pertain to transient pumping rates and storage durations, and multiple cycles of operation, and are applicable to various well configurations and thermal plume geometries. Heat losses to confining layers, its implications for optimizing plume geometries and aspect ratios, and heat spreading due to free convection are also discussed. This provides a general tool for broad and rapid assessment of aquifers and ATES systems. We show that if heat exchange with the confining layers is negligible, the thermal recovery efficiency of thermal plumes with cylindrical geometry is independent of the aquifer porosity and heat capacity C0. Therefore, if mechanical dispersion is negligible as is often the case, the only aquifer property that affects the recovery efficiency is the aquifer thermal conductivity. The field‐scale aquifer thermal conductivity λ can therefore be inferred from the recovery efficiency of a push‐pull heat recovery test. Remarkably, an increase in C0 could either increase, decrease, or not affect the recovery efficiency, depending on the thermal plume geometry. Hence, the analytical solutions reveal that the recovery efficiency is affected by complex interactions between the thermal plume geometry and aquifer properties. Approximate analytical solutions for subsurface temperature profiles over an entire ATES cycle are also derived.

Choanocyte dimensions and pumping rates in the demosponge Halichondria panicea

The individual choanocyte pumping rate in choanocyte chambers (CCs) is important for understanding the hydrodynamics in sponges and has hitherto been based on measured volume-specific filtration rate and estimated CC density. However, the CC density may vary in different regions of the sponge and to circumvent this uncertainty and to get precise measurements of the individual choanocyte pumping rate, a new experimental approach was developed. Here the aim was to measure the individual pumping rate of choanocytes based on live dimensions of CC elements and particle tracking to measure the speed of small particles entering into the CCs. This was done by using combined live-cell imaging in sandwich cultures of the marine demosponge Halichondria panicea and video-tracking of particles. Small 2 μm-beads and cyanobacteria (Cyanobium bacillare) in the incurrent canal enter the CCs via a 3.3 ± 0.9 μm diameter prosopyle to be subsequently captured by the choanocytes whereas larger algal cells (Rhodomonas salina) and 10 μm-beads are captured in the incurrent canals. CC diameters were positively correlated to the diameter of choanocytes, indicating a total of 84 choanocytes per CC with mean diameter 22.9 ± 6.2 μm. The pumping rate per choanocyte (Qc) was estimated to be between 54 and 68 μm3 s−1. Regardless of demosponge species and based on data in the literature, a choanocyte is suggested to pump between 50 and 100 μm3 s−1.

Technical note: Testing the effect of different pumping rates on pore-water sampling for ions, stable isotopes, and gas concentrations in the hyporheic zone

Abstract. The hyporheic zone (HZ) is of major importance for carbon and nutrient cycling as well as for the ecological health of stream ecosystems, but it is also a hot spot of greenhouse gas production. Biogeochemical observations in this ecotone are complicated by a very high spatial heterogeneity and temporal dynamics. It is especially difficult to monitor changes in gas concentrations over time because this requires pore-water extraction, which may negatively affect the quality of gas analyses through gas losses or other sampling artifacts. In this field study, we wanted to test the effect of different pumping rates on gas measurements and installed Rhizon samplers for repeated pore-water extraction in the HZ of a small stream. Pore-water sampling at different pumping rates was combined with an optical sensor unit for in situ measurements of dissolved oxygen and a depth-resolved temperature monitoring system. While Rhizon samplers were found to be highly suitable for pore-water sampling of dissolved solutes, measured gas concentrations, here CH4, showed a strong dependency of the pumping rate during sample extraction, and an isotopic shift in gas samples became evident. This was presumably caused by a different behavior of water and gas phase in the pore space. The manufactured oxygen sensor could locate the oxic–anoxic interface with very high precision. This is ecologically important and allows us to distinguish between aerobic and anaerobic processes. Temperature data could not only be used to estimate vertical hyporheic exchange but also depicted sedimentation and erosion processes. Overall, the combined approach was found to be a promising and effective tool to acquire time-resolved data for the quantification of biogeochemical processes in the HZ with high spatial resolution.

Analysis of seepage and temperature fields and their influence on collapse pressure while drilling in shale oil reservoirs

Shale wellbore instability poses a considerable challenge in terms of drilling efficiency. However, previous studies typically assumed single-phase flow in the seepage field, neglecting the influences of water saturation and temperature on rock mechanical properties. Furthermore, there has been a lack of quantitative analysis on the degree of correlation between various factors and collapse pressure. To address these gaps, this research introduces an oil–water two-phase seepage model to describe the water saturation distribution surrounding the wellbore,and also constructed a wellbore temperature field model that accounts for mechanical and hydraulic heat sources and validated its accuracy. Furthermore, this paper examines the effects of temperature and seepage on shale mechanical parameters. By incorporating a rock failure criterion that accounts for water saturation, a shale collapse model in thermal-seepage coupling is established, which has also been validated. Finally, this paper utilises the grey relational analysis to quantitatively assess the correlation between different variables and collapse pressure. The results indicate that the temperature field and collapse models are consistent with field data. As drilling time increases, water saturation and invasion distance grow, while the seepage radius hardly increases anymore. When porosity exceeds 0.05, its influence on water saturation weakens. Under unbalanced conditions, capillary force drives drilling fluid into the formation. The maximum wellbore temperature is found near the drill bit and exceeds the formation temperature. The bottom-hole temperature difference increases with the increase in well depth and drilling time, sometimes exceeding 20 °C. Among drilling engineering parameters, pump rate has greater influence on bottomhole temperature than WOB, RPM and ROP. Regarding drilling fluid property parameters, density, flow index and consistency coefficient considerably influence bottom-hole temperature. The influence of seepage on collapse pressure is greater than that of the temperature field. Grey relational analysis reveals that pump rate and water saturation have the highest correlation with collapse pressure. As drilling time increases, the correlation degree of pressure difference, horizontal section length and weight on bit gradually increase, while that of the mud behaviour index, consistency coefficient, rock thermal conductivity and mud yield stress slightly decreases.

Metastability exchange optical pumping of 3He at low pressure and high magnetic field

Systematic studies on metastability exchange optical pumping of 3He nuclei have been performed at Jefferson Lab using a 1-torr sealed cell at magnetic fields from 2 to 4T. The effects of the discharge intensity, pump laser power and pumping transition schemes on achievable nuclear polarization and pumping rate have been investigated. A maximum steady-state nuclear polarization of about 75% has been obtained. This work provides a baseline for the development of the novel polarized 3He target for CLAS12 at Jefferson Lab.

Photon pumping, photodissociation and dissipation at interplay for the fluorescence of a molecule in a cavity

We introduce a model description of a diatomic molecule in an optical cavity, with pump and fluorescent fields, and electron and nuclear motion are treated on equal footing and exactly. The model accounts for several optical response temporal scenarios: A Mollow spectrum hindered by electron correlations, a competition of harmonic generation and molecular dissociation, a dependence of fluorescence on photon pumping rate and dissipation. It is thus a general and flexible template for insight into experiments where quantum photon confinement, leakage, nuclear motion and electronic correlations are at interplay.