Medium Reservoir Research Articles

Ichthyofaunal Diversity and Seasonal Harvest Patterns in Dudhawa Reservoir, Chhattisgarh, India

This study seeks to examine the status and biodiversity of fishes in medium reservoir known as Dudhawa of Chhattisgarh. The major objectives were to collect the primary data on fisheries of Dudhawa reservoir, collection, preservation and identification of fish species, to enlist the fish fauna and to study the seasonal variations in fish harvest of Dudhawa reservoir. For this study, fish specimens were collected during August 2022 to February 2024 from the reservoir and primary data pertaining to species abundance, yield and production of the reservoir were collected from the Matsya Mahasangh Raipur. The results of empirical study revealed that the list of 43 species were classified under 5 orders, 13 families and 28 genera. Analysis of different species reveals that 69.76% of them belong to a single order, Cypriniformes. The analysis of the fishes listed show that 6.97 % species belong to order Mastacembeliformes, 11.62% belong to order Perciformes, 4.65% belong to order Channiformes and 2.32% species belong to order Cluipeiformes. Statistical analysis of data reveals no correlation between stocking and yield of the reservoir. Fish species in the Dudhawa reservoir were broadly categorized into four group i.e. major carps, catfishes, minor fish and minnow’s fish. Critical observation of data shows that major carp’s fishery dominated the catch during August, 2022 to February, 2024. A high yield of major carp’s fishery (26728 kg) was obtained in November. However, catfish fishery fluctuated between 2400.5 kg in August to 9063 kg in March. Bulk of minnows fishes (23.33%-56.6%) were recorded in drag netting may be due to reduced water level during summer (February to May, 2023). This data will definitely help the fishermen and as well as fisheries officials for better stock and harvest management of this type of small reservoir of Chhattisgarh.

Preparation and Characterization of Temperature-Sensitive Gel Plugging Agent.

In order to use intelligent gel systems to realize deep source water control in medium and high water cut reservoirs, and also to solve the shortcomings of conventional gels, such as the high chemical dose required, large profile control radius, poor temperature resistance, shear resistance, and plugging performance, a temperature-sensitive gel based on natural cellulose was developed, and the temperature resistance, rheological performance, and plugging performance of the temperature-sensitive gel were tested and evaluated. The results show that the system can maintain a viscosity retention rate of up to 95% after high-temperature aging at 90-120 °C for 50 days. When using medium- to low-salinity calcium chloride formation water for preparation, the gelation effect is good. The rheometer oscillation frequency scanning test shows that the system gel is a strong elastic body dominated by elasticity. The core displacement experiment shows that the highest sealing rate of the system is 97%, and the breakthrough pressure can reach 2.5 MPa at this time. The microstructure of the gel system was tested by infrared, and it was found that the gel system had strong hydrogen bonding and the gel had good stability. The research results contribute to improving the recovery rate of high water cut oil reservoirs.

Bacillus subtilis-mediated synthesis of ZnO and Ag-ZnO nanoparticles for eco-friendly displacement agents: Enhancing oil recovery in middle/low permeability reservoirs with nanofluid

Microorganisms, known for their widespread distribution and nonpolluting nature, are extensively used as raw materials. In this study, ZnO nanoparticles (ZnO NPs) and Ag-ZnO nanoparticles (Ag-ZnO NPs) were synthesized using Bacillus subtilis, and their efficacy as nano-displacement agents for enhancing oil recovery in medium and low permeability reservoirs was investigated. The morphology, structure, and properties of these nanomaterials were analyzed using various characterization methods. The results indicated that ZnO NPs are irregularly blocky with an average particle size of 44.7 nm, while Ag-ZnO NPs are approximately spherical with an average particle size of 35.5 nm, both exhibiting high purity and stability. These two nanoparticles can effectively reduce oil–water interfacial tension and improve rock wettability, with Ag-ZnO NPs showing superior performance. In core displacement tests at 60 °C, the recovery rates for intermediate permeability cores (30–40 mD) were 12.43% for ZnO nanofluids and 14.10% for Ag-ZnO nanofluids. For low-permeability cores (<10 mD), the recovery rates were 8.63% and 10.26%, respectively. Microscopic oil displacement experiments revealed that the mechanism of oil displacement by nano-displacement agents includes altering rock surface wettability, penetrating narrow pores, emulsifying crude oil, and exerting viscoelastic effects. In summary, these two nanomaterials significantly improve oil recovery in reservoirs, offering an important reference for their application in the oilfield and pointing toward a new direction for developing green and efficient alternatives to chemical flooding agents.

Numerical simulation of two-phase oil–water flow in fractured-vuggy reservoirs based on the coefficient of porous medium proportion and coupled regions

Based on the flow characteristics of fluids in various reservoir media, fractured-vuggy oil reservoirs can be classified into seepage zones and conduit flow zones. An interface exists between these two regions, where the movement of formation fluid near this interface is characterized by a coupling or transitional phenomenon between seepage and conduit flow. However, the complexity of this coupling interface poses challenges for traditional numerical simulations in accurately representing the intricate fluid dynamics within fractured-vuggy oil reservoirs. This limitation impacts the development planning and production adjustment strategies for fractured-vuggy oil reservoirs. Consequently, achieving accurate characterization and numerical simulation of these systems remains a critical challenge that requires urgent attention. A new mathematical model for oil-water two-phase flow in fractured-vuggy oil reservoirs is presented, which developed based on a novel coupling method. The model introduces the concept of the proportion coefficient of porous media within unit grids and defines a coupling region. It employs an enhanced Stokes–Brinkman equation to address the coupling issue by incorporating the proportion coefficient of porous media, thereby facilitating a more accurate description of the coupling interface through the use of the coupling region. Additionally, this proportion coefficient characterizes the unfilled cave boundary, simplifying the representation of model boundary conditions. The secondary development on the open-source fluid dynamics software is conducted by using matrix & laboratory (MATLAB). The governing equations of the mathematical model are discretized utilizing finite volume methods and applying staggered grid techniques along with a semi-implicit calculation format for pressure coupling—the Semi-Implicit Method for Pressure Linked Equations algorithm—to solve for both pressure and velocity fields. Under identical mechanism models, comparisons between simulation results from this two-phase flow program and those obtained from Eclipse reveal that our program demonstrates superior performance in accurately depicting flow states within unfilled caves, thus validating its numerical simulation outcomes for two-phase flow in fractured cave reservoirs. Utilizing the S48 fault-dipole unit as a case study, this research conducted numerical simulations to investigate the water-in-place (WIP) behavior in fractured-vuggy oil reservoirs. The primary focus was on analyzing the upward trend of WIP and its influencing factors during production across various combinations of fractures and dipoles, thereby validating the feasibility of the numerical modeling approach in real-world reservoirs. The simulation results indicated that when multiple dissolution cavities at different locations communicated with the well bottom sequentially, the WIP in the production well exhibited a staircase-like increase. Furthermore, as the distance between bottom water and well bottom increased, its effect on water intrusion into the well diminished, leading to a slower variation in the WIP curve. These characteristics manifested as sudden influxes of water flooding, rapid increases in water levels, and gradual rises—all consistent with actual field production observations. The newly established numerical simulation method for fractured-vuggy oil reservoirs quantitatively describes two-phase flow dynamics within these systems, thus effectively predicting their production behaviors and providing guidance aimed at enhancing recovery rates typically observed in fractured-vuggy oil reservoirs.

Research on Refined Water Injection Technology for Medium and High Water Cut Reservoirs in Nanpu 4 Block

Abstract For water injection development reservoir, the key is to control the di-rection and flow field of the injected water in the reservoir to adjust the tapping of the remaining oil between wells. This paper presents that, by applying the comprehensive discrimination technique of inefficient cir-culation flow field, a flow field evaluation model containing permeabil-ity, overwater multiplier and water saturation seepage characteristics parameters is established and the small layer flow field distribution is quantitatively evaluated by numerical simulation. Based on the geo-logical characteristics, development characteristics and grid inefficient circulation coefficients, the flow field is qualitatively classified into three types: streamline not established, streamline primary and sec-ondary, and streamline fixed and difficult to adjust. Based on the re-search of domestic and foreign literature and numerical simulation, the management system of different types of flow fields is studied to clari-fy the reasonable development technology policy of reservoir flow field adjustment and tapping the remaining oil between wells, so as to achieve the purpose of controlling the reservoir water content rise rate, reducing the water content rate and improving the recovery rate. The mine field experiments conducted in Nanpu 4 block showed that the recovery rate of the block increased by 4 percentage points, indicating that the block development achieved significant results. This is an im-portant guideline for reservoir development in low recovery, medium to high water-bearing reservoirs with water injection development.

Interactions and oil recovery performance of a prepared extended amphoteric surfactant combining with a nonionic surfactant under high salinity condition

The extended amphoteric surfactant (named C12P3E3NS), characterized by FTIR and 1H NMR, was prepared by amination and sulfonation in order to enhance oil recovery (EOR) for the low-permeability oil reservoirs. The surface and interfacial tensions of its combination systems with nonionic surfactant (APG0810, an Alkyl Polyglycoside), obtained by tension meter, were evaluated to obtain an optimized surfactant system for enhancing oil recovery. The compound system (named C12A) with 40 % mole fractions of C12P3E3NS, exhibiting the strongest interaction behavior and highest expansion modulus, possesses the best abilities of reducing the interfacial tension to ultra-low (10-3 mN/m order of magnitude) at a salinity of 10 wt%, and owns certain abilities of emulsifying crude oil. Meanwhile, the contact angle, measured by the contact angle measuring instrument, can be altered from 108.50°to 55.07°by the compound system C12A, confirming its better wetting alteration ability of transforming the capillary force from resistance to driving force. Eventually, displacement efficiency, obtained from core displacement tests, reveals that the compound surfactant system C12A can decrease the pressure by 15.80 % and its corresponding oil recovery factor is 15.25 % after water flooding, demonstrating its favorable displacement performance and potential application in medium or high salinity reservoirs.

An efficient reduced order model for nonlinear transient porous media flow with time-varying injection rates

An intrusive Reduced Order Model (ROM) is developed for nonlinear porous media flow problems with transient and time-discontinuous fluid injection rates. The proposed ROM is significantly more computationally efficient than the Full Order Model (FOM). The training regime is generated using the FOM with constant injection rates during the offline stage. The trained ROM exhibits high accuracy for complex pumping schedules (rate vs time) simulated online. The proposed ROM uses the combination of Proper Orthogonal Decomposition and Discrete Empirical Interpolation Method (POD-DEIM), which is compared with the classical POD-Galerkin. The use of an approximated column-reduced Jacobian is shown to be vital to achieving a substantial speedup of ROM vs FOM run-times. An analysis of the trade-off between accuracy and run-time is conducted for ROMs of different sizes and hyper-parameters. The impact of the training regime on the performance of the presented ROM is assessed. The performance of the ROM is studied in the context of a two-dimensional analysis of time-varying injection into a two-well system in a layered porous media reservoir. The accuracy and efficiency of POD-DEIM motivate its potential use as a surrogate model in the real-time control and monitoring of fluid injection processes.

Physical Properties of High-Rank Coal Reservoirs and the Impact on Coalbed Methane Production

The physical characteristics of coal reservoirs are important factors affecting the occurrence status of coalbed methane, as well as key factors restricting the production capacity. Therefore, taking 3# coal in Qinnan region of China as the research object, based on the actual production data of 200 coalbed methane wells in the research area, experimental testing combined with simulation analysis was used to explore the physical properties of medium and high-order reservoirs and their impact on the occurrence and production of coalbed methane. The characteristics of coalbed methane reservoir formation and production capacity changes in the research area were revealed, and the factors restricting the production capacity of coalbed methane wells were calculated using the gray correlation analysis method. The results indicate that the micropores in the coal reservoir in the study area are well-developed, while the macropores and mesopores (exogenous fractures) are underdeveloped, the surface of the micropores is complex, and the connectivity of the micropores is poor, resulting in reservoirs with high gas adsorption characteristics and low permeability. The fractal characteristics of pores and fractures can reflect the permeability characteristics of reservoirs. Permeability is positively correlated with macropores (exogenous fractures) and mesopores, and negatively correlated with micropores. There is a positive correlation between permeability and productivity, and the reservoir in the study area has a stress-sensitive boundary. The main factors restricting productivity under the complex pore and fracture system of high-rank coal reservoir were identified, and the gray relational analysis method was used to evaluate the development effect of the research area. This study provides guidance for the development of coalbed methane production in high-rank coal reservoirs.

The effect of lens and fitting characteristics upon scleral lens centration.

To quantify the impact of varying central fluid reservoir depth, lens thickness/mass and the addition of a peripheral fenestration upon scleral lens centration. Ten young, healthy adults participated in a series of repeated-measures experiments involving short-term (90 min) open eye scleral lens wear. Scleral lens parameters (material, back optic zone radius, diameter, back vertex power and landing zone) were controlled across all experiments, and the central fluid reservoir depth (ranging from 144 to 726 μm), lens thickness (ranging from 150 to 1200 μm), lens mass (101-241 mg)and lens design (with or without a single 0.3 mm peripheral fenestration) were altered systematically. Scleral lens decentration was quantified using over-topography maps. On average, scleral lens centration varied by <0.10 mm over 90 min of wear. Medium and high initial fluid reservoir conditions resulted in 0.17 mm more temporal and 0.55 mm more inferior lens decentration, compared to the low fluid reservoir depth (p < 0.001). Changes in lens thickness or the addition of a peripheral fenestration did not cause clinically significant changes in centration (<0.10 mm on average) when controlling for fluid reservoir depth. Central fluid reservoir depth was the best predictor of horizontal and vertical lens decentration, explaining 62-73% of the observed variation, compared to 40-44% for lens thickness and mass. Scleral lens decentration remained relatively stable over 90 min of lens wear. A greater initial central fluid reservoir depth resulted in significantly more lens decentration, particularly inferiorly. Large variations in lens thickness, massor the addition of a single peripheral fenestration did not substantially affect lens centration.

Emulsion properties and plugging performances of active crude oil enhanced by amphiphilic Janus nanosheets

Inadequate strength and stability of active crude oil emulsions stabilized by conventional surfactants always lead to a limited plugging rate of plugging agents. Thus, to address this issue, the synthesis of amphiphilic Janus nanosheets was effectively carried out for enhancing the system performances and subsequently characterized. Based on the outcomes of orthogonal tests, an assessment was conducted on the nanosheet and surfactant formulations to optimize the enhancement of emulsion properties. The experimental demonstration of the complex system has revealed its remarkable emulsifying capability, ability to decrease interfacial tension and improve rheological behavior at high temperature (80 °C) and high salinity (35,000 ppm) conditions. Involving probable mechanism of the system performance enhancement is elucidated by considering the synergistic effect between surfactants and nanosheets. Furthermore, variables including water-to-oil ratio, salinity, temperature and stirring intensity during operation, which affect the properties of prepared emulsions, were investigated in detail. The efficacy and stability of the complex system in obstructing medium and high permeability cores were demonstrated. Notably, the core with a high permeability of 913.58 mD exhibited a plugging rate of 98.55%. This study establishes the foundations of medium and high permeability reservoirs plugging with novel active crude oil plugging agents in severe environments.

Enhanced Modulation of Streamflow Flash Droughts by Reservoir Operations in India

AbstractStreamflow flash droughts (SFDs) occur due to a rapid decline in streamflow and cause major challenges associated with water availability for downstream ecosystems, hydropower generation, and irrigation water demand. Human interventions such as reservoir operations and reservoir storage can considerably influence streamflow variability. However, the crucial role of dams/reservoirs on the occurrence of SFDs in India remains unexamined. Using a combination of hydrological and hydrodynamical models, we examined the role of reservoirs on SFDs in India during 1971–2020. Reservoirs play a considerable role in the occurrence of SFDs during the summer monsoon season (June‐September) in India. The frequency and severity of SFDs in the presence of reservoirs are substantially lesser than in the absence of them. In addition, high and low antecedent reservoir storage conditions before meteorological flash droughts (MFDs) do not support the rapid decline of streamflow (i.e., SFDs) downstream of reservoirs, while the medium reservoir storage conditions prior to MFDs favor the development of SFDs. Similar to conventional (or long‐term) streamflow droughts (SDs), SFDs are more frequent in the El Nino phase than in the La Nina phase. Unlike the long‐term streamflow droughts, the implementation of dams considerably reduces the frequency of SFDs during both the negative and positive phases of El Nino Southern Oscillation. Overall, our findings demonstrate the considerable role of human interventions in flash drought occurrence, as SFDs are triggered by MFDs but modulated by reservoir storage and operations.

Effect of thermodiffusion on compositional grading in hydrocarbon reservoirs: Insights from field cases and simulations

Heterogeneity of fluid composition in vertical and lateral directions is observed in many reservoirs, known as compositional grading. It is necessary to evaluate the diffusion forces for modeling this phenomenon. In addition to the chemical and gravity forces, the temperature gradient causes mass diffusion. In the present investigation, the accuracy and reliability of the Haase theory and the Shukla-Firoozabadi method in thermodiffusion modeling are studied comprehensively using field samples from light to heavy-oil reservoirs. On the one hand, the Shukla-Firoozabadi model results in compositional grading reduction by thermodiffusion; on the other hand, the Haase theory reveals enhancement and attenuation effects of thermodiffusion depending on reference enthalpy quantification. A new approach, which employs the reference enthalpies of pseudocomponents as tuning parameters, is proposed to improve the results of the Haase theory. The proposed procedure is also validated using field cases. In addition, the experimental field information compared with isothermal and nonisothermal models are studied to answer the question of "how" and to "what extent" thermodiffusion contributes to compositional grading. Results demonstrated the limited attenuation effect of thermodiffusion in light oils, while this phenomenon leads to severe enhancement of compositional grading in the medium and heavy-oil reservoirs. In heavy oils, the thermodiffusion effect is more pronounced on heavy pseudocomponents rather than light paraffinic species. Finally, the practice of compositional gradient model optimization, which is of particular interest to reduce the uncertainty in fluid initialization and to address reservoir compartmentalization, is presented.

Implementation of a novel EOR screening methodology to the oilfields in Türkiye

In response to growing energy demand of Türkiye, an enhanced oil recovery (EOR) applicability assessment was conducted through an improved screening methodology, calibrated with successful applications. The methodology incorporated some improvements in applicability ranges and a novel pointing system. 159 oilfields in Türkiye were characterized based on reservoir properties and categorized as heavy, weak and strong aquifer support. The characterization revealed how source rock type and regional paleo-tectonic events dictate primary recovery and need for EOR. The EOR assessment implemented promised 58 applicable cases out of 315. Carbon dioxide (CO2) injection is applicable for many fields, which could stimulate feasibility of carbon capture projects in the country. Immiscible nitrogen injection might be an alternative for many of the medium and light oil reservoirs in the absence of CO2. Polymer flooding is also promising mainly for fields having weak-aquifer support. However, our hands-on experience suggests that conformance control is required to control flow of EOR agent in densely fractured carbonates. Thermal methods do not seem applicable in heavy oil reservoirs due to depth limitations except in-situ combustion, which requires pilot test confirmation. Provided methodology in this study may be used as a guideline for other fields to assess EOR potential.

Numerical analysis of hydraulic fracture propagation in deep shale reservoir with different injection strategies

Deep shale reservoirs are characterized by elevated breakdown pressures, diminished fracture complexity, and reduced modified volumes compared to medium and shallow reservoirs. Therefore, it is urgent to investigate particular injection strategies that can optimize breakdown pressure and fracturing efficiency to address the increasing demands for deep shale reservoir stimulation. In this study, the efficiency of various stimulation strategies, including multi-cluster simultaneous fracturing, modified alternating fracturing, alternating shut-in fracturing, and cyclic alternating fracturing, was evaluated. Subsequently, the sensitivity of factors such as the cycle index, shut-in time, cluster spacing, and horizontal permeability was investigated. Additionally, the flow distribution effect within the wellbore was discussed. The results indicate that relative to multi-cluster simultaneous fracturing, modified alternating fracturing exhibits reduced susceptibility to the stress shadow effect, which results in earlier breakdown, extended hydraulic fracture lengths, and more consistent propagation despite an increase in breakdown pressure. The alternating shut-in fracturing benefits the increase of fracture length, which is closely related to the shut-in time. Furthermore, cyclic alternating fracturing markedly lowers breakdown pressure and contributes to uniform fracture propagation, in which the cycle count plays an important role. Modified alternating fracturing demonstrates insensitivity to variations in cluster spacing, whereas horizontal permeability is a critical factor affecting fracture length. The wellbore effect restrains the accumulation of pressure and flow near the perforation, delaying the initiation of hydraulic fractures. The simulation results can provide valuable numerical insights for optimizing injection strategies for deep shale hydraulic fracturing.

A novel TLFD-GA algorithm for multi-objectives optimization of ORC power plants with the effect of pressure drop considered

This research introduces a novel TLFD-GA algorithm for the three-level criteria optimization of organic Rankine cycle (ORC) power plants. It replaces the non-dominated sorting of NSGA-II with three-level fuzzy decision to simultaneously optimize environmental, thermodynamic, and techno-economic criteria. The algorithm provides direct optimization results without needing additional decision-making methods. Furthermore, the impact of pressure drop in plate heat exchangers is investigated, revealing a proportional relationship between pressure drop and the increment of evaporation pressure. A parametric study on 24 basic and recuperative trans-critical geothermal ORC systems indicates that compensating for pressure drop leads to a 5% decrease in thermodynamic performance, a 20% decrease in techno-economic performance, and a 20–60% increase in heat transfer area per net output power. After TLFD-GA optimization, the saving to investment ratio improves by an average of 4.5% across scenarios. R1270 stands out with a remarkable ratio of 3.13 and 4.32 in medium and high-temperature geothermal reservoirs. Moreover, the proposed TLFD-GA optimization algorithm has demonstrated its superiority in terms of superb convergence and stability when compared to NSGA-II, which suggests its prospective application in the low-carbon and green energy fields.

A strong stability gel foam for water shutoff during oil and gas reservoir development

In view of the short effective period of conventional foam for water shutoff during oil and gas reservoir development, a strong stability gel foam system is proposed in this work. By comparing the foam properties of different foaming systems, the optimized formulation of foam system is “0.3% SDS (sodium dodecyl sulfate) + 0.4% HPAM (partially hydrolyzed polyacrylamide) + 0.3% SD-107 (organic chromium).” At 50 °C and 10 000 mg/l salinities, the volume of foam is basically unchanged after a short time of defoaming and finally remains above 70%, and the drainage half-life can reach 16 days. The polymer and crosslinker form a stable three-dimensional network structure on the Plateau boundary after foaming, which has good viscosity and viscoelasticity. The foam system has excellent temperature and salt resistance. It is appropriate for medium and low temperature shallow reservoirs. The foam system has a good plugging efficiency. It can effectively plug the fracture and improve the sweep volume, which has a good application prospect.

Synthesis of biological nanocomposite fluids and enhanced crude oil recovery

Aiming at the problems of small pores, complex structure, large seepage resistance, and poor recovery effect in the development process of offshore medium and low permeability reservoirs, a green and environmental friendly biological nanocomposite fluid (BNF) was developed to enhanced crude oil recovery (EOR). Fe3O4@SiO2-Ag nanoparticles (NPs) were synthesized in the laboratory, and citric acid, tannic acid, sodium alginate, and trehalose lipids were used as surface modifiers for NPs and as fluid stabilizers. The nanocomposites were characterized by SEM–EDS, TEM, FTIR, XPS, XRD, and VSM. The EOR mechanism of BNF was studied by laboratory experiments, in which the interfacial tension can be reduced by 80 %. Moreover, 500 ppm BNF could keep oil and water emulsified for more than 3 months. Static separation of oil droplets and dynamic stripping of oil film exhibited obvious effects, and the bioactive substances’ dispersant and NPs can jointly drive away residual oil. The experiment on core displacement of crude oil showed that 500 ppm BNF can enhance oil recovery by 15.56 % on the basis of water flooding. The BNF oil displacement agent is economic and environmental friendly, providing a new method for the green and high-quality development of offshore oil fields.

Modeling the influence of small reservoirs on hydrological drought propagation in space and time

To increase drought preparedness in semi-arid regions across the world many small and medium reservoirs have been built in recent decades. Together these reservoirs form a Dense Reservoir Network (DRN) and its presence generates numerous challenges for water management. Most of the reservoirs that constitute the network are unmonitored and unregistered, posing questions on their cumulative effects on strategic reservoirs and water distribution at watershed scale. Their influence on hydrological drought propagation is thus largely unexplored. The objective of this study is then to assess DRN effects on droughts both in time and space. A modeling-analytical framework is proposed to achieve this goal. A mesoscale semi-distributed hydrological model was utilized to simulate both a network of large strategic reservoirs and a DRN in a large-scale tropical semiarid watershed. To investigate the effects in time and space generated by the network’s presence, the differences between multiple network scenarios were analyzed. Results show that the presence of the DRN accelerates the transition from meteorological to hydrological drought phases by 20% on average and slows down the recharge in strategic reservoirs by 25%, leading to a 12% increase of periods in hydrological drought conditions in a highly strategic basin and 26% without strategic reservoirs. This is because the DRN increases the hydrological dysconnectivity at catchment scale, reducing inflow to strategic reservoirs. In space, the DRN shifts upstream the basin’s water storage capacity by 8%, but when both large and small reservoirs are present the stored volume distribution behavior is not straightforward. The findings confirm the need to consider the effect of small reservoirs when developing and implementing drought management policies and reservoir-management approaches at regional scale.

Phytoplankton analysis and assessment of reservoir water quality at Rena Medium Reservoir, Godavari Basin, India

Phytoplankton analysis and assessment of reservoir water quality at Rena Medium Reservoir, Godavari Basin, India

Advances in corneal preservation using an active storage machine

Since the 1980s, corneal storage has been carried out by eye banks throughout the world, mainly by two methods: short‐term storage at 4°C (America, India), and medium‐to‐long‐term organoculture at 31–34°C (Europe, Australia). In these two techniques, known as passive, the cornea is simply immersed in a storage medium. However, the control of corneal hydration in vivo depends both on the proper functioning of the corneal endothelial cells (responsible for the imbibition pressure IP) and on the presence of a normal intraocular pressure (IOP), both of which are opposed to the stromal swelling pressure (SP): IP = SP‐IOP. By restoring IOP ex vivo in an active storage machine (ASM) that separates an endothelial chamber from an epithelial chamber, corneal hydration is better controlled, thus preventing the formation of deep endothelial folds responsible for endothelial over mortality. The active control of corneal hydration eliminates the need to add macromolecules to deswell the cornea (continuously for cold storage or during the last 48–72 h for organoculture). The toxicity of this forced deswelling has been demonstrated for organ culture.We performed two successive preclinical studies comparing ASM and organoculture with paired human corneas having more than 2000 cells/mm2 at the time of the first endothelial count. The organoculture medium (CorneaMax, Eurobio, les Ulis, France) was identical in both groups. The ASM was an experimental version from our laboratory, including a PEEK (polyetheretherketone) corneal support, a peristaltic pump, an Edwards pressure sensor, a microsolenoid valve and a microcontroller managing the flow rate (2.6 μL/min) and the IOP (21 mmHg). In the first study, for 52 pairs of corneas stored for 4 weeks, the ASM corneas had, at the end of storage, +23% viable endothelial cells compared to passive organoculture. Furthermore, ASM also significantly increased Na+/K+/ATPase protein expression by 3.8 ± 1.4. In the second study, for 12 pairs of corneas stored for 3 months, the ASM corneas had +53% viable endothelial cells at the end of storage compared to passive organoculture. One third of corneas still had 2000 cells/mm2 or more in ASM versus none in organoculture. The ASM significantly increased Na+/K+/ATPase protein expression by 2.9 ± 0.8.The ASM has 2 transparent windows which allow all quality controls to be performed without deconditioning the cornea, and in particular to perform endothelial counting by specular microscopy on a cornea which remains thin. The ASM thus combines the advantages of both methods of storage: long‐term storage without massive oedema and without toxic dextran and a closed system allowing non‐invasive controls. As with the perfusion machines for vascularized organs, the restoration of near‐physiological conditions improves grafts' quality.We have transferred this innovation to THEA laboratories (Clermont‐Ferrand, world specialist in ophthalmology) which is industrializing the ASM via its spin‐off SINCLER. The industrial version will take the form of a single‐use cassette incorporating a flow/pressure regulator, a media reservoir and a waste bin. The cassette will be plugged into a computer‐controlled multi‐place incubator for IOP and media flow management. The ASM could revolutionize eye banking worldwide.