bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of 3D and Near-Wellbore Geomechanical Models for Well Trajectories Optimization
Authors: Alchibaev D. V. , Glazyrina A. Ye. , Ovcharenko Yu. V. , Kalinin O. Yu. , Lukin S. V. , Martemyanov A. N. , Zhigulskiy S. V. , Chebyshev I. S. , Sidelnik A. V. , Bazyrov I. Sh.
Published: October 2017

For the prediction and elimination of complications in the drilling process is considered a number of examples of the three-dimensional geomechanical model and of the near-wellbore model in order to optimize the trajectory and design of the wells. During the well trajectory planning, the key point is to forecast and minimize all possible risks associated with both geological, mechanical conditions and technological parameters. An optimal solution can be obtained with the use of a detailed geomechanical analysis.

It is shown that in a number of cases, the numerical model of the near wellbore zone is more informative, in comparison with the analytical solution. The result of drilling risks minimization with help of geomechanical analysis tools is presented. A number of recommendations on wellbore construction and stability are established of the comprehensive geomechanical analysis. The discontunities that are derived of seismic field analysis are also included in the review.

The image analysis, 1D geomechanical modelling, of seismic field analysis, near-wellbore numerical simulation and full 3D goemechanical modelling were used as a geomechanics tools to optimize "fishbone" trajectory. Microimages help to determine the presence of cavernousness, natural and induced fractures, geological boundaries and bedding planes. Especially useful is a tool for determining the presence of collapse in the areas of kick-off sidetracks. 1D geomechanical modeling helps to determine favorable intervals for shearing and optimal mud density. To assess the risks during the sidetracking operation, a statistical analysis of the actual data was carried out taking into account the spatial orientation of the sidetrack and the direction relative to the currently acting stress state. Stresses and gradients of caving in the intervals of cuts are refined by the near wellbore model.
Influence of the Elastic Moduli Contrast on the Height Growth of a Hydraulic Fracture
Authors: Shel Egor
Published: October 2017

In mostmodern models and simulatorsfor the hydraulic fracture growth, only stress contrast is taken into account correctly. For the distribution of elastic moduli, a simplified model for averaging the elastic characteristics over crack height is used, in which a composition of several media with different elastic moduli is replaced by one medium with average characteristics.

In this paper, a more accurate method for crack opening evaluation is found, which takes into account the contrast of the elastic moduli of rocks. The problem of the elastic-strength problem was solvedwith the apparatus of singular integral equations. The obtained result is compared with the analytical solution for the widely spread averaged elastic moduli model. It is revealed that the averaged model gives a smoother profile of the crack.

The problem is solved within the assumptions of the plane theory of elasticity and the mechanics of brittle fracture. The medium is assumed to be homogeneous in each separate layer, with contrast of Young's moduli, Poisson's coefficients and stresses between adjacent layers. For the brevity, fluid pressure along the vertical contour of the crack is assumed to be uniform, as in the Pseudo3D model. The problem is solved by means of singular integral equations in which the pressure is equal to the integral of the fracture's opening derivative with the kernel of the equation. The contrast of the elastic moduli does not allow an analytical solution of the problem, in contrary to the case for a completely homogeneous media, which has been observed in classical works.

The contrast of the elastic moduli leads to a sharper distribution of the opening in height, in comparison with that predicted by a simplified model of averaged elastic moduli. In media with higher Young's moduli, the actual opening of the fractureis lower, and in media with lower moduli the opening is higher than model ofthe average elastic moduli predicts. Thus, in a multilayered medium, local narrowing in the vertical crack profile is possible, which hinders the passage of proppant into the productive interlayers lying above and below the initiation pay layer. Also, significant deviations are possible for the area of the crack profile, which can significantly affect length due to material balance. To predict the growth of a crack, not only investigations of the productive interval are important, but also the clay bridges separating the target layers, are needed.
Development of 3D Geomechanical Model: Case Study from One Off-Shore Sakhalin Field
Authors: Ershov A. , Eidinov A. , Popova A.
Published: October 2017

In modern conditions, optimal production field development and explotation require detailed and reliable information on the geomechanical behavior of the rock massive. 3D geomechanical model of the field was developed. A technique for its creation and verifying as well as some application results are presented bellow.

On a base of available geological and geophysical data and core analysis data of reference wells was defined the following: distribution of elastic - mechanical and strength properties of rocks; distribution of pore / reservoir pressures; principal stresses orientations and magnitudes.

The resulting 1D geomechanical models of reference wells were calibrated based on the results of existing well tests and special studies, including data on drilling accidents. 3D grid was created on which petrophysical, elastic-mechanical, strength and other data on reference wells were transferred. A 3D geomechanical model of the whole field (from the seabed to the acoustic basement) was created. The model was matched with all available data. The reliability of the model was further confirmed by the results of the "blind test". The essence of the test is reduced to the construction of a three-dimensional model based on an incomplete set of reference wells with further calculation of the parameters of the wells removed from the modelind process and its compareing with the actual ones.

Analysis of fault tectonics, including the determination of the tectonic regime and the identification of active faults, was performed. The source of anisotropy of horizontal stresses was determined. Estimation of horizontal stresses was made on a base of determination of their regional components, which arose as a reaction of the medium to the applied boundary loads. The boundary conditions were defined by the way of matching modeling calculation results with the results of observations. A forecast for the development of fracture zones near the faults was given also.
Laboratory Studies of Sand Control Systems Used for Heavy Oil Production from Unconsolidated Rocks
Authors: Betekhtin A. N. , Kostin D. K. , Tikhomirov E. V. , Nikolaev M. N. , Lyapin V. V. , Misbakhov R. Zh.
Published: October 2017

The paper addresses issues related to selection of sand control systems applied when producing heavy oil from unconsolidated rocks. A sharp productivity reduction was noticed during the operation of wells with filters. A methodology accounting for subsurface features has been developed for laboratory testing of well-completion systems to reduce uncertainties. Damage related to undesirable drop in flow rate was analyzed. As a result, corrections were promptly introduced to the size of filters used in well completions, which led to increased productivity of newly commissioned wells.
Innovative Technologies and Approaches to Interpreting Logging Data in Horizontal Wells
Authors: Shchetinina N. V. , Malshakov A. V. , Basyrov M. A. , Zyryanova I. A. , Ganichev D. I. , Yatsenko V. M.
Published: October 2017

The article addresses the evolution history of interpretation of logging data from horizontal wells in Russia and abroad. Key problems of interpreting logging data are analyzed. It also describes the application of new technologies and approaches that have increased the validity of logging interpretation. The authors substantiate the need to integrate the full spectrum of geological and geophysical information. Further ways to develop approaches are proposed.
Determination of Oil/Water Contact While Drilling by Interpreting Data from the Azimuthal Deep Resistivity Tool under Conditions of Uncertainty Associated with the Measurements of Inclination
Authors: Zaboev Konstantin , Ruzaev Rinat , Mikhailov Alexander , Grechiho Pavel
Published: October 2017

Geological objectives during horizontal well drilling operations are increasingly challenging. The objective during geosteering in uncertain conditions is the determination of the oil/water contact (OWC). Understanding the OWC position is crucial to oilfield production. Typically, the OWC position is determined by evaluating exploration wells. However, there is uncertainty in how it is transposed across a field when faulting is evident or water injection operations are in place. There is additional uncertainty regarding the well position because various corrections can be made to the directional measurements from the survey tools. Therefore, when geologists are faced with the task of holding a well a certain distance from the OWC, it is not always correct to fully rely on inclinometer measurements. The absolute mark can be any mark with a certain probability within the ellipse of uncertainty. This paper presents an example of how a trajectory based on static measurements with a discreteness of 10 m could differ from a trajectory constructed from a dynamic survey with a much smaller sampling rate. The method proposed uses an azimuthal deep resistivity tool to identify and quantify the distance to the OWC.
Tailoring of the Fracturing Technologies to Challenging Geological Conditions of Jurassic Formation of Yamal Peninsula
Authors: Ishangaliev Askhat , Yudin Alexey , Borisenko Alexey , Vernigora Denis , Gromovenko Alexander , Korepanov Alexander , Olender Oleg
Published: October 2017

Novoportovskoe field is one of the largest oil, gas and condensate fields on the Yamal Peninsula. The Jurassic reservoir is the main productive horizon at that field. It contains 50 % of oil reserves and it is described by a 45-meter deposit with a gas cap and bottom water. The main risk during hydraulic fracturing, in the absence of barriers, is the proximity of gas- and water-bearing formations. The hydraulic fracture breakthrough into gas and water zones leads to a significant decrease of oil production rate. The main objective of the described project was a selection of fracturing technologies, which would minimize the indicated risk.

A number of technologies was introduced to control the vertical growth of the hydraulic fracture: polymer-free fracturing fluid to reduce the viscosity and enhance the hydraulic fracture cleaning. The technology of enzyme fluid breaker that enables to significantly improve the retained conductivity of the hydraulic fracture compared to standard oxidative breakers. The efficiency of enzyme breaker does not directly depend on the concentration but advantages of the enzyme breaker increase at low formation temperatures. The safe ball launcher allows minimizing the amount of fluid injected during hydraulic fracturing.

A series of studies was conducted to analyze the hydraulic fracture geometry: Microseismic Monitoring at Multistage Hydraulic Fracturing; Long-Spaced Cross-Dipole Sonic Log, which allows determining the hydraulic fracture height. Production logging tests were performed to assess the productivity and identification of ports with a breakthrough into water- and gas-bearing horizons. The implementation of various technologies and methods of hydraulic fracturing ensured to significantly enhance the well productivity and influenced the field development plan.

The obtaining of a low gas ratio and water encroachment percentage was a key criterion for success of the performed operations. As a result, in most of the wells, the gas ratio does not exceed 500m3/t and water encroachment is not more than 40%. Currently, the enzyme breaker and ball launcher are the preferred methods for multistage hydraulic fracturing in the Jurassic formations of Novoportovskoe field. The well treated with polymer-free fracturing fluid has one of the lowest gas ratio (387 m3/t) and oil production rate of 100 t/day. The ball launcher made it possible to reduce the volume of the injected fluid during hydraulic fracturing by 30% and to decrease the operation time from 5 days to less than 2 days. The approach developed and technologies selected showed a stable growth of productivity and complete applicability of hydraulic fracturing under Jurassic horizon conditions of this unique field.

Stimulation operations under complicated geographic and geological conditions give some opportunities for the oil industry in the Arctic.
Unconventional Basement Reservoir: From Studying to Prediction on the Example of North-Var’yegansky Field
Authors: Kazakova Anastasiia S. , Rykus Mikhail V.
Published: October 2017

As a rule, unconventional reservoirs of pre-Jurassic sequence are characterized by a complex structural and tectonic pattern, sharp variability of net pay thickness and properties. Therefore, using standard approaches often leads to unreliable forecasts. To find effective forecast tools, authors holistically analyze various types of well data and seismic survey, which results in identifying the most efficient tools for studying geological aspects and the way they influence field development, and forecasting.

Stages of this work include identifying productive methods for well correlation, core analises, description of thin sections and well log methods and their matching for the purpose of detecting regularities for various rock types using well tests and well performance data. When data were analyzed, the focus was placed on physical properties of reservoir rocks. Besides, the field structure is studied as a whole unit using tectonic history reconstruction.

One of the main results of this work is a comprehensive study of the geological development of the upper part of the Paleozoic basement on North-Var’yogansky field area for the purpose of a further identification of reservoir extension zones and prediction of well performance depending on rock and void types. Taking into account the new geological image, rock typing is carried out. It is identified that development of rocks with reservoir properties depends on the following factors: primary rock composition, existence of the intake centers of hydrothermal solutions and channels though which they arrived (faults, cracks, fractures) and a set of secondary processes. In the result of this work a complete compliance of well data with seismic survey was achieved. This provided for identification of promising drilling zones and making a plan for geological modeling. Justification of the recommended well logging list and conclusions as to the efficiency of various study methods are important points in studying this kind of fields of the Paleozoic basement.

Nowadays, the discussed approach to studying the Paleozoic basement reservoir is the most appropriate one. In this paper, authors show matching rocks and void properties with field development, which is a top-priority goal for modern geology.
Digital Field as a Field and Production Managment Tool
Authors: Chagirov P. S. , Korobeynikova E. V.
Published: October 2017

Digital Field Data Analytical System is a tool for managing the operation processes of the enterprise, covering a range of tasks to monitor hydrocarbons movement from the bottom of a well to the inlet facilities of the LNG plant. The system allows online monitoring and control of the development and operations at the field by issuing advance alerts about possible complications in the wells and pipeline segments in the gas gathering system. The system is unique because it is based on the integrated approach of the production management and a multidisciplinary team to promptly prevent well and pipeline problems and make decisions on the operating parameters of the wells, pipelines and the entire field. The system allows to respond proactively to possible multimillion risks caused by the failures in the stable operation of the field (including the disruptions in the operation of expensive project facilities), the uninterrupted utilization of the plant's capacity and, as a consequence, the regularity of LNG offloading to tankers.
First in Russia Large-Scale Implementation of the Channel Fracturing Technology in Horizontal Wells
Authors: Yudin Alexey , Sypchenko Stella , Gromovenko Alexander , Romanovskiy Rostislav , Chebykin Nikolay , Serdyuk Andrey , Bukharov Dinar , Faizullin Ildar , Churakov Artem
Published: October 2017

Main producing horizons of the southern license block of the Priobskoe oil field are low-permeable sandstone formations AS10–AS12. Here, horizontal drilling and multistage stimulation (MSS) involving hydraulic fracturing have proved to be an effective way of field development. Full-scale testing of the channel fracturing technology has become the next stage of MSS optimization. This paper is dedicated to analyzing the efficiency of this method based on data from 40 wells.

Centered around creation of channels inside the fracture, the new method of hydraulic fracture allows better reliability of proppant placement without conductivity restraint; this is achieved by pulsing the proppant on surface, and use of fibers. Moreover, the channel fracturing technique provides significant savings in materials needed for a stimulation job – particularly, up to 45% of proppant and up to 20% of fluid – accelerating bringing-in of the as well as reducing the environmental footprint. The screenout risk is mitigated by pulsing the clean fluid and using fibers while using higher proppant concentrations at the same time.

Over the course of three years, more than 240 channel fracturing jobs were executed in 43 wells. This paper contains a detail analysis of performance of the wells put on production with implementation of the new MSS technique, compared to neighbor wells where conventional stimulation techniques were used. The wells are divided into groups, e.g. by fracture direction (transverse and longitudinal) and water content in the area, i.e. water-free sections and high water cut sections. The obtained production data proves that wells stimulated with channel fracturing show at least the same efficiency than wells where conventional fracturing was used, and involve better utilization of less resources.

The project described in this paper is the first experience of mass use of channel fracturing technique for horizontal wellbores in Russia. Lessons learnt from this experience, efficiency analysis, and applicability criteria defined in the scope of this project will help assess the potential of this new technique for other oil and gas fields in Russia.
Mathematical Modeling of Proppant Embedment and Its Effect on Conductivity of Hydraulic Fracture
Authors: Pimenov A. A. , Kanevskaya R. D.
Published: October 2017

The proppant embedment into rock during the operation of the hydraulically fractured well is one of the reasons for the production rate decrease. Most researchers analyze this problem on the basis of laboratory experiments and do not take into account the well production data. The article proposes a mathematical model of proppant embedment, which makes it possible to estimate the change in the fracture conductivity. A joint calculation of the stress and pressure fields is carried out. The stress values are used to check the conditions at the start of proppant embedment. The discussed example shows a decrease in the width and conductivity of the fracture due to the proppant embedment, and the conditions are found under which this effect is significant. Usually, in order to assess the fracture conductivity, well tests are carried out. Using proposed mathematical model together with the well test results, makes it possible to estimate the contribution of proppant embedment to the change in fracture conductivity, as well as to identify additional factors leading to well production rate decrease.
Improved Hydraulic Fracturing Results Utilizing Microfrac Testing in a West Siberia Field
Authors: Karpov V. B. , Parshin N. V. , Ryazanov A. A. , Zheng Y. , Kornilov A. V. , Moiseenko A. A.
Published: October 2017

Identification and quantification of in-situ stress barriers is a crucial part of every hydraulic fracturing design and treatment programme. The absence of stress barriers may lead to significant vertical growth of the fracture, creating a channel between the oil-bearing intervals and potential undesirable water-bearing formations.

This paper presents a case study where the in-situ stress profile in a tight oilfield in West Siberia was re-calibrated. The original stress profile, which was based on core analysis, gamma ray and acoustic data, indicated the stress contrast was enough to contain the fracture within the producing layer. Unexpectedly, high water cut between 60 to 70 % was reported in the horizontal wells, where multi-stage hydraulic fracturing was performed and the source of water production was uncertain.

Consequently, straddle packer microfrac testing was conducted in one well to create a more detailed and better-constrained stress profile in the target oil-bearing formation as well as in the bounding shale above and below. The data obtained indicated very little stress contrast between the production layer and the surrounding shale layers. The revised stress model differed significantly from what was typically used in West Siberia. The updated hydraulic fracture model showed that excess height growth into the surrounding shale barriers was likely, and breakthrough into the water-bearing layer located 50 to 70 meters above could explain the high observed water cuts in the treated wells.

Assuming a uniform stress profile along the lateral, the hydraulic fracture design was then optimized to decrease the risk of breakthrough into the water zone. The optimized treatments involved low-viscosity fracturing fluid and also a reduced amount of proppant per stage used in the treatment. The optimized hydraulic fracture treatment was performed in several horizontal wells, which saw a reduction in the initial water cut to below 10%, and also experienced an increase in oil production. This demonstrates the importance of having reliable stress measurements for hydraulic fracturing design.
Drip Irrigation Affects the Morphology and Distribution of Olive Roots
Authors: Deng Shixin , Yin Qun , Zhang Shanshan , Shi Kankan , Jia Zhongkui , Ma Luyi
Published: October 2017

Under field conditions, this study investigated the influence of the irrigation amount on olive root morphology and spatial distribution. Soil samples were taken with an auger at distances of 30, 60, and 90 cm from the tree trunks in four directions. The roots were analyzed using an Epson Twain Pro root scanning system. The results indicated that under different irrigation treatments, the indicators of root morphology of different varieties showed different responses to the irrigation amount. The root length density (RLD), root surface area (RSA), and root volume (RV) of Arbosana first increased with increasing irrigation amount but then decreased; however, those of Arbequina monotonically increased with increasing irrigation amount. The root average diameter of the two varieties was inversely proportional to the irrigation amount. In the vertical dimension, the RLD and RSA of each treatment decreased with increasing soil depth and were mainly distributed in the surface soil (0–20 cm in depth). The RLD and RSA in the vertical direction (VD) of the drip irrigation belt were higher than those of the belt in the parallel direction (PD), and the range was 12% to 86%. Compared with the roots of the 0- to 20-cm soil layer, the roots of the 20- to 40-cm and 40- to 60-cm soil layers were more influenced by the irrigation amount. Horizontally, the RLD and RSA decreased with increasing radial distance. The 30-cm radial area contained most roots, the proportion of roots in this region increased with increasing irrigation capacity. The influence of irrigation quantity in the PD of the drip irrigation belt was greater than that in the VD. The results suggest that irrigation does not change the root spatial distribution pattern but does promote root growth. The two varieties had different responses to irrigation. In terms of soil moisture levels after irrigation, 75% of field capacity is appropriate for ‘Arbosana’, whereas 100% is advisable for ‘Arbequina’. To improve water use efficiency, moisture should be irrigated within the 30-cm radial distance from the trunk, and irrigation depth is not easy to more than 20 cm. This study provides a scientific basis for the efficient water management of olive trees.
Interspecific and Intergeneric Hybridization in Baptisia and Thermopsis
Authors: Hawkins Susan M. , Ruter John M. , Robacker Carol D.
Published: October 2017

Interspecific and intergeneric crosses were performed between species in the genera Baptisia and Thermopsis with the goal of creating hybrids with the best qualities of both parents. Baptisia australis (L.) R. Br. was used as both the male and female parent in intergeneric crosses. Thermopsis chinensis Benth. ex S. Moore, T. lupinoides (L.) Link, and T. villosa Fernald & B.G. Schub. were used as male and female parents in both interspecific and intergeneric crosses. Pollen was collected from B. alba (L.) Vent., B. bracteata Muhl. ex Elliott, and B. lanceolata (Walt.) Ell. and used to make interspecific and intergeneric crosses. Putative hybrids were obtained from both interspecific and intergeneric crosses. Interspecific crosses produced a higher percentage of pollinations resulting in seed set and the number of seeds per pollination than intergeneric crosses. Morphological differences between parent species and progeny were evident in putative hybrids resulting from intergeneric crosses between T. villosa and B. australis and T. villosa and B. alba. Most putative hybrids bloomed during the second year after germination. Because seedlings could be obtained from both interspecific and intergeneric crosses, hybrids within and between the genera Baptisia and Thermopsis are feasible. The Fabaceae family contains 670–750 genera and 18,000–19,000 species. Baptisia (commonly called false or wild indigo) and Thermopsis (commonly named false lupine) of the Fabaceae belong to the tribe Thermopsidae, which comprises 46 species in six genera. All species in Thermopsis and Baptisia are herbaceous; they are the only two genera in Thermopsidae that do not have woody species. Thermopsis contains 23 species and has a wide-spread distribution with species endemic to Asia and much of temperate North America. Although Thermopsis is considered to have originated in central Asia, T. chinensis Benth. ex S. Moore and T. fabacea (Pallas) Candole are thought to have originated in North America and migrated over the Bering Land Strait to Asia. Three Thermopsis species, T. fraxinifolia Nutt. ex M.A. Curtis, T. mollis (Michx.) M.A. Curtis ex A. Gray, and T. villosa Fernald & B.G. Schub., are native to the southeastern United States. Baptisia contains 15–17 species that are endemic to the southeastern and midwestern United States.
Establishment of a Rapid and Efficient Micropropagation System for Succulent Plant Haworthia turgida Haw.
Authors: Liu Boling , Fang Hongzhou , Meng Chaorong , Chen Ming , Chai Qingdong , Zhang Kai , Liu Shijuan
Published: October 2017

In the present study, the effect of plant growth regulators (PGRs) on callus regeneration, adventitious shoot differentiation, and root formation of Haworthia turgida Haw. was investigated. The greatest callus induction percentage (95.6%) was achieved with leaf explants inoculated on Murashige and Skoog (MS) medium with 1.0 mg·L−1 6-benzyladenine (BA) and 0.1 mg·L−1 1-naphthaleneacetic acid (NAA), and this callus induction medium supplemented with 2.5 mg·L−1 thidiazuron (TDZ) was optimal for callus proliferation. The maximum number of shoots (25.7) was obtained when the callus was cultured on MS medium supplemented with 1.0 mg·L−1 BA and 0.2 mg·L−1 2,4-dichlorophenoxyacetic acid (2,4-D). The highest number of roots per shoot (6.2) and highest rooting frequency (82.0%) were obtained when adventitious shoots were inoculated on MS medium with 0.05 mg·L−1 NAA. Regenerated plantlets were transferred to a mixture of vermiculite and soil and acclimated in a greenhouse. The survival rate of the transplanted plantlets was about 91.6%. The rate of ex vitro rooting was 83.3%, indicating that this technique is effective for root induction in H. turgida. This study has established a rapid and efficient micropropagation system that can be beneficial for commercial cultivation and germplasm conservation of H. turgida.
Horticulture in Iran Can Be an Alternative to Petroleum and a Major Source of International Business with Unique Potential and Challenges
Authors: Fallahi Esmaeil
Published: October 2017

The art and science of horticulture and horticultural crops are integral parts of Iranian’s rich and ancient culture and modern economy. Many deciduous fruit, flowers, and vegetables are native to Iran (Persia), and from there, they were distributed to the rest of the world through the Silk Road established by the Achaemenid, the Royal Pars Dynasty. Variations in climate and presence of numerous mountains, lakes, rivers, and natural springs have created a unique country capable of producing all types of fruits, vegetables, and flowers. Apples and other deciduous fruits are commercially produced in mountain ranges of Alborz and Zagrous and in many central provinces of Iran. The Caspian Sea area in the north of Iran is one of the most unique regions in the world where mild Mediterranean climate meshed with the adjacent Alborz mountain ranges has created a home to numerous species of edible horticultural plants, ranging from tea to cherries and pomegranates. Pistachio, olive, citrus, banana, and date are produced in Kerman, Fars, and Khuzestan regions. However, the Iranian horticultural industry faces many challenges, including global and regional political issues. Although some attempt has been made to preserve invaluable germplasm, a large number of native fruits, vegetables, and flowers are becoming extinct. Postharvest transportation and storage of horticultural crops is one of the most important issues facing Iranian horticulture. The future of horticulture in Iran can potentially be bright, and horticultural products have the potential to replace the oil income after reserves disappear, particularly if peace prevails in the region.
Soil Heating and Secondary Plant Covers Influence Growth and Yield of Winter High Tunnel Spinach
Authors: Drost Dan , Ernst Taunya , Black Brent
Published: October 2017

High tunnel (HT) winter production may be limited by extreme low air temperatures, suboptimal soil temperatures, large diurnal temperature changes, and short daylengths and associated low light conditions. To determine the productivity of spinach in extreme climates, HT production trials were conducted in the fall (October to December) and winter (January to March) of 2010–12 at the Greenville Research Farm in Logan, UT (lat. 41 N. elevation 1455 m). Soil heating (±) using electric cables and secondary covers (fabric rowcovers and plastic low tunnels) were evaluated to determine combined effects on fall and winter spinach production. Soil heating significantly increased yield in all cover treatments in the Fall 2010 (F2010) trial when spinach was planted in November, but had little to no effect on plant productivity in the other three trials (more appropriate planting dates) even though it did increase soil temperature marginally. The addition of secondary covers significantly increased plant biomass and leaf area when compared with the uncovered control. Excluding the F2011 trial when spinach was planted earlier under more favorable temperature and light conditions, the use of low tunnels resulted in significantly higher spinach yields (biomass and leaf area) than when grown under fabric rowcover. In the fall, relative growth rates (RGRs) decreased exponentially regardless of whether the soil was heated or not heated or if a secondary cover was used. This response was because of the seasonal decline in light levels and temperatures. In the winter production cycle, spinach relative growth without covers was similar or increased as climatic conditions improved. For plants grown under fabric or plastic rowcovers, RGR remained more constant or decreased during the production cycle. Increased yields were possible with secondary covers as air temperatures increase more quickly in the morning, maintained optimal temperatures longer each day (higher growing degree hours), and retained trapped heat later into the evening. Statistical interaction between heating cables and secondary covers were rarely observed. Fall and winter HT spinach production increases when further protection with secondary plant covers is provided; however, supplemental soil heating is not necessary.
Irrigation Requirements for Seed Production of Two Eriogonum Species in a Semiarid Environment
Authors: Shock Clinton C. , Feibert Erik B.G. , Rivera Alicia , Saunders Lamont D. , Shaw Nancy , Kilkenny Francis F.
Published: October 2017

Seeds of native plants are needed for rangeland restoration in the Intermountain West. Many of these plants are rarely cultivated and relatively little is known about the cultural practices required for their seed production. Irrigation trials were conducted over multiple years for two perennial Eriogonum species, Eriogonum umbellatum Torr. and Eriogonum heracleoides Nutt. The two species grown at the Oregon State University Malheur Experiment Station, Ontario, Ore., received 0, 100, or 200 mm·year−1 of drip irrigation. Seed yield responses to irrigation were evaluated by linear and quadratic regression against 1) applied water; 2) applied water plus spring precipitation; 3) applied water plus winter and spring precipitation; and 4) applied water plus fall, winter, and spring precipitation. In general, seed yields responded quadratically to irrigation. For E. umbellatum, over 11 years, highest seed yields averaged 260 kg·ha−1 and ranged from 207 to 508 kg·ha−1. For E. heracleoides, over 6 years, highest yields averaged 353 kg·ha−1 and ranged from 168 to 588 kg·ha−1. Adding spring precipitation to applied water improved the accuracy of estimated water requirements for maximum seed production of E. umbellatum. For E. heracleoides, adding precipitation to applied water did not improve the accuracy of estimated water requirements for maximum seed production. Averaged over 11 years, seed yield of E. umbellatum was maximized by 209 mm·year−1 of spring precipitation plus irrigation. Averaged over 6 years, seed yield of E. heracleoides was maximized by 126 mm·year−1 of applied water. Both species required relatively small amounts of irrigation to help assure seed yield, and the irrigation needed for E. umbellatum could be adjusted by taking spring precipitation into account.
Multinuclear Magnetic Resonance Analysis of Two Humic Acid Fractions from Lowland Rice Soils
Authors: Mahieu N. , Olk D.C. , Randall E.W.
Published: October 2017

To determine the effects of intensive cropping of tropical lowland rice (Oryza sativaL.) and the associated long‐term soil submergence on chemical properties of soil organic matter, we used solid‐state13C and15N and solution31P nuclear magnetic resonance (NMR) spectroscopy to analyze the labile mobile humic acid (MHA) and the more recalcitrant calcium humate (CaHA) fractions extracted from a series of soils supporting several long‐term field experiments in the Philippines. The soils varied mainly in degree of submergence and cropping intensity, ranging from a rainfed rice field without soil submergence to irrigated double‐ and triple‐cropped fields in which soil remains submerged almost all year long. As reported previously, all analyses associated increasing intensity of rice cropping with larger proportions of less humified material in the MHA and CaHA, such as diester phosphorus (P), amide nitrogen (N), and phenolic carbon (C). We established significant correlations between proportions of various spectral areas as well as between some spectral areas and other humic acid (HA) properties such as visible light absorption and free radical concentration (positive indices of humification) and hydrogen (H) concentration (negative index of humification). For example, spectral proportions of heterocyclic N were positively, and proportions of amide N and phenolic C negatively, correlated with visible light absorption and free radical concentration, and each of these spectral proportions had an opposite sign when correlated with H concentration. The correlations of N‐alkyl C proportions were the strongest with these properties and with other functional group proportions.
Enzymatic Transformation and Binding of Labeled 2,4,6‐Trinitrotoluene to Humic Substances during an Anaerobic/Aerobic Incubation
Authors: Thiele S. , Fernandes E. , Bollag J.‐M.
Published: October 2017

Organic pollutants are degraded in soil and simultaneously non‐extractable residues are formed. However, proof is lacking that this fixation has a detoxifying effect. We investigated the transformation and binding of 2,4,6‐trinitrotoluene (TNT) with catechol or soil humic acid as cosubstrates. Carbon‐14‐labeled TNT and its reaction products were quantified by radiocounting; extractable compounds were identified by high performance liquid chromatography (HPLC). Bound and extractable residues of 15N‐labeled TNT and metabolites were studied by 15N nuclear magnetic resonance spectroscopy (15N NMR). Since TNT is not easily transformed under oxidizing conditions an anaerobic/aerobic treatment was used. Anaerobic microorganisms from cow manure were used to reduce TNT during the anaerobic phase and subsequently, a laccase from Trametes villosa was used in the aerobic phase to oxidatively couple the metabolites to humic matter. Seventy‐four percent of TNT was immobilized with catechol as cosubstrate, but only 25% with humic acid. With catechol the main extractable component was TNT, while with humic acid it was mostly the metabolite 4‐aminodinitrotoluene. For both co‐substrates, the spectra of immobilized metabolites obtained by solid‐state 15N‐cross polarization magic angle spinning (CPMAS) NMR spectroscopy showed signals in the chemical shift region for protonated aromatic amino compounds. However, in the presence of catechol, an additional signal from non‐extractable nitro groups was found, which could represent sequestered TNT. The partially reduced metabolites of TNT that formed non‐extractable residues in humic acid are not likely to be remobilized easily and are thus regarded as detoxified.
Imaging of Water Flow in Porous Media by Magnetic Resonance Imaging Microscopy
Authors: Deurer Markus , Vogeler Iris , Khrapitchev Alexander , Scotter Dave
Published: October 2017

Magnetic resonance imaging (MRI) was used to study the flow of water in a column 14 mm in diameter packed with glass beads. The sample was fully saturated and water was pumped through the column using a peristaltic pump, at flow rates of 125 and 250 mL h−1This corresponds to mean velocities of 0.5 and 1 mm s−1, given a porosity of 0.46 m3m−3Nuclear magnetic resonance (NMR) images of the proton density and velocities within a 2‐mm slice were taken at a spatial resolution of 0.15 × 0.15 × 2 mm3At a mean pore water velocity of 1 mm s−1we approximated hydrodynamic dispersion using NMR‐measured velocity distributions in a 2‐mm slice through the sample. Additionally, we conducted a step pulse tracer experiment with chloride through the same column and at identical initial and boundary conditions. We fitted the convection–dispersion equation to the breakthrough curve and compared the column scale dispersion of the tracer experiment with the respective NMR estimate derived at the slice scale.
Combination Effect of Light and Toxicity in Algal Tests
Authors: Cleuvers Michael , Altenburger Rolf , Ratte Hans Toni
Published: October 2017

The sensitivity of Scenedesmus subspicatus against potassium dichromate is positively correlated to the photon flux density during the algal growth inhibition test. Low photon flux densities led to significantly reduced maximum effects and higher EC50 levels. To improve the testing of colored substances, we distinguished between the toxic effect (chemical part, represented by potassium dichromate) and the shading effect (physical part, simulated by reduced light intensities during the test) of a hypothetical light absorbing substance. The contribution of these single effects to the total inhibition varied greatly. At high concentrations of potassium dichromate (1.6 and 3.2 mg L−1) the physical part never exceeded 25% of the total inhibition, not even at strongest light reduction, while at low concentrations (0.2 and 0.4 mg L−1) the physical effect became more prominent when halving the amount of available light. Further, the combination effect of the chemical and the physical effect could be calculated well only by using the concept of independent action. Thus, if chemical and physical effects are measured in combination, as is the case in tests with dyestuffs, the current test protocol for the algal growth inhibition test may lead to incorrect estimations of the toxic potential.
Chemistry of Inorganic Arsenic in Soils
Authors: Smith E. , Naidu R. , Alston A. M.
Published: October 2017

There are more than 10000 arsenic (As) contaminated sites in Australia. The ability of soils at these contaminated sites to sorb As is highly variable and appreciable amounts of As have been recorded in the subsurface soils. The potential risk of surface and ground water contamination by As at these sites is a major environmental concern. Factors that influence adsorption capacity of soils influence the bioavailability and subsequent mobility of As in soils. In the present study we investigated the effect of PO3−4 and Na+ and Ca2+ on the sorption of AsV and AsIII by an Oxisol, a Vertisol, and two Alfisols. The presence of P (0.16 mmol L−1) greatly decreased AsV sorption by soils containing low amounts of Fe oxides (<100 mmol kg−1), indicating competitive adsorption between P and AsV for sorption sites. In contrast, the presence of a similar amount of P had little effect on the amount of AsV adsorbed by soils with high Fe content (>800 mmol kg−1). However, AsV sorption substantially decreased from 0.63 to 0.37 mmol kg−1 as P concentration was increased from 0.16 to 3.2 mmol L−1 in selected soils. This suggests increased competition between P and AsV for soil sorption sites, through either the higher affinity or the effect of mass action of the increasing concentration of P in solution. A similar effect of P on AsIII sorption was observed in the low sorbing Alfisol and high affinity Oxisol. However, the amount of AsIII sorbed by the Oxisol was much greater than the Alfisol for all treatments. The presence of Ca2+ increased the amount of AsV sorbed compared with that of Na+ and was manifested through changes in the surface charge characteristics of the soils. A similar trend in AsIII sorption was recorded with changes in index cation, although the effect was not as marked as recorded for AsV
Dissolution Kinetics of Heavy Metals in Dutch Carbonate‐ and Sulfide‐Rich Freshwater Sediments
Authors: Buykx S. E. J. , van den Hoop M. A. G. T. , Loch J. P. G.
Published: October 2017

In two sulfide‐rich freshwater sediments from the Biesbosch and Kromme Rijn River in the Netherlands differing in carbonate content and acid volatile sulfide (AVS) content, metal and sulfide dissolution kinetics were studied at different acid concentrations by varying both the procedure of acid addition and the extraction time. The establishment of equilibrium was monitored by measuring the pH in time, which reached a near constant value. The equilibrium pH was reached quickly when large amounts of acid were added and slowly when small amounts of acid were added. This observation was confirmed by the yield of extracted metals after either a 45‐min or 24‐h extraction over a pH range from 0 to 5. The pH factor seemed to be of more influence than time for the dissolution of metals. The amount of extracted metals was highly dependent on the metal itself due to its physico–chemical behavior. Although the sediments studied varied in carbonate content, acid volatile sulfide (AVS), and total metal content, the extracted fraction of metals compared with their total content in the sediment was similar for most metals. Finally, the AVS content as well as the ratio of simultaneously extracted metals (SEM; sum of Cd, Cu, Ni, Pb, and Zn) to AVS decreased with increasing pH. Because the SEM to AVS ratio may be used to set environmental quality criteria for the sediment compartment, this observation is of significance.
Concentration, pH, and Surface Charge Effects on Cadmium and Lead Sorption in Three Tropical Soils
Authors: Appel Chip , Ma Lena
Published: October 2017

Reactions of heavy metals with soil are important in determining metal fates in the environment. Sorption characteristics of two heavy metals, Cd and Pb, in three tropical soils (Mollisol, Oxisol, and Ultisol) from Puerto Rico were assessed at varying metal concentrations (0 to 1.2 mM) and pH values (approximately 2 to 7). All soils sorbed more Pb than Cd. Sorption maxima were obtained for each metal for the Oxisol and Ultisol soils, but not the Mollisol. Sorption appeared to depend more on soil mineralogy than organic matter content. Sorption isotherms were linear within the sorption envelope with similar slopes for each soil–metal curve, when plotting metal sorption as a function of pH. Cadmium and Pb isotherms yielded average slopes of approximately 36 ± 1 and 28 ± 1 units (percent increase in metal sorption per 1‐unit increase in pH), respectively. Metal sorption depended more on metal type than soil composition. Cadmium sorption displayed a greater pH dependence than Pb. Cadmium sorption was less than or equal to the amount of negative surface charge except at pH values greater than the point of zero net charge (PZNC). This suggests that Cd was probably sorbed via electrostatic surface reactions and/or possible inner‐sphere complexation at pH > 3.7. However, the amount of Pb sorbed by the Oxisol was greater than the amount of negative surface charge, suggesting that Pb participates in inner‐sphere surface reactions. Lead was sorbed more strongly than Cd in our soils and poses less of a threat to underlying ground water systems due to its lower mobility and availability.
Rhizosphere Acidification and Cadmium Uptake by Strawberry Clover
Authors: Jauert P. , Schumacher T. E. , Boe A. , Reese R. N.
Published: October 2017

Strawberry clover (Trifolium fragiferum L.) is a hardy legume found in indigenous or introduced populations throughout the world. Tolerance to saline and alkaline soils, flooding, and heavy metals make it a good prospect for reclamation projects. The research, described here, was conducted to: (i) characterize the morphological variation in plants from available seed sources, (ii) evaluate cadmium uptake and tolerances over a wide range of morphological variants, and (iii) elucidate the variability in the effects of roots on rhizosphere pH and the relationship to cadmium uptake. Seeds from selected accessions were planted in the greenhouse for comparison of morphological variation. The accessions examined had a mean height of 10.7 ± 7 cm. Accessions 254916 and 237925 are tall with high rhizosphere pH values and might be useful in phytoremediation. Strawberry clover accessions were also grown hydroponically to examine differences in cadmium uptake. The ability of strawberry clover roots to change rhizosphere pH and take up cadmium was examined using culture tubes containing nutrient agar, a moderate level of cadmium, and a pH indicator dye. The results provided evidence for a negative correlation between rhizosphere pH and cadmium uptake.