bluuebunny/crossref_metadata_2025 huggingface dataset:
Smart well- Benefits, Types of Sensors, Challenges, Economic Consideration, and Application in Fractured Reservoir
Authors: Pari M. Nadri , Kabir A. H. , Motahhari S. Mahdia , Behrouz Turaj
Published: May 2009

Smart Well technology has seen rapid evolution in the last decade because of technological advancements. Proper knowledge of this technology, with some risk mitigating techniques, makes several benefits to an oil company including the capability of drilling longer horizontal and extended reach wells, particularly snake wells with great reduction in cleanup, reservoir management and water and gas breakthrough concerns. Even in some cases unexpected benefits have been discovered from this technology.

Sensors are considered to be the heart of smart well completion. There are different types of sensors in the oil industry including wellbore internal sensors and casing external sensors. Some of these sensors are used for wellbore measurement and some for imaging the distribution of reservoir attributes away from the well. In this paper we will investigate all types of sensors either developed sensors and emerging sensors to measure pressure, temperature, flow Rate, noise, phase composition, pH, water cut, gas fraction and capacitance. However commonly used ones are P, T and flow rate sensors. Others are still emerging technologies. It is possible to use permanent sensors named pressure, resistivity, acoustic on outside wall of the casing as well to estimate permeability, porosity, saturation and monitor near wellbore water / flood front encroachment.

Although Smart Well technology has shown several benefits but it possesses some challenges regarding their reliability and cost effectiveness and implementation phases. As a result, many companies tend to apply this technology with caution knowing that the cost of a smart completion can easily be three to four times more than a conventional completion.

In this paper we present a comprehensive review of state-of-the-art Smart Well technology including all benefits, different types of sensors, challenges, economic consideration and application in fractured reservoir.
Prediction of Rock Mechanical Parameters for Hydrocarbon Reservoirs Using Different Artificial Intelligence Techniques
Authors: Abdulraheem A. , Ahmed M. , Vantala A. , Parvez T.
Published: May 2009

Rock mechanical parameters of reservoir rocks play an extremely important role in solving problems related to almost all operations in oil or gas production. A continuous profile of these parameters along the depth is essential to analyze these problems which include wellbore stability, sand production, fracturing, reservoir compaction, and surface subsidence. The mechanical parameters can be divided into three main groups, viz., elastic parameters, strength parameters, and in-situ stresses. Even the profile of in-situ stresses with depth is estimated using logs with elastic parameters as an essential input. The focus of this work is on the prediction of elastic parameters and their variation with the depth of a given reservoir.

For an isotropic medium, there are two independent elastic parameters, viz., Young's modulus and Poisson's ratio. Generally, logging data consisting of density, compressional and shear wave velocities are used to estimate these parameters. However, these data provide dynamic elastic properties which are different from static values, especially in case of Young's modulus.

To get continuous rock samples throughout the depth of the reservoir and conduct triaxial tests to determine the static values of these parameters is extremely expensive. Consequently, static values of Young's modulus and Poisson's ratio obtained from laboratory testing on rock samples acquired from selected intervals are used to calibrate the dynamic data obtained from logs. However, since the rock layers vary in their properties with depth, a realistic estimation of static elastic values of the rock is still a challenge. The problem is more prominent in limestone rocks compared to sandstone rocks. Further, shear velocity data is not always available from well logs, making the problem more difficult.

An extensive experimental program was carried out first to obtain the static values of elastic parameters of reservoir rock samples at reservoir conditions of high pressure. Log data consisting of different variables such as density, velocity, and porosity from the same wells were also obtained.

Three artificial intelligence methods viz. Neural Network, Fuzzy Logic and Functional Network, were used to obtain a continuous profile of static elastic parameters along the depth. The results obtained from these approaches were compared using log inputs. The strengths of each of these approaches are also discussed.
3D Reservoir Geomechanical Modeling in Oil/Gas Field Production
Authors: Koutsabeloulis Nick , Zhang Xing
Published: May 2009

The pore pressure, stress state and geological structures as well as their evolution during an oil/gas field life have widespread influence on implications for wellbore stability, hydraulic fracturing, fault-reactivation, early water-cut, top surface subsidence, reservoir compaction and water/gas flooding. These events have a significant impact on reservoir performance and their effects need to be taken into account in production surveillance, analysis and forecasting. A coupled reservoir geomechanical modeling approach is developed, using the static and dynamic models of VISAGETM System, to compute the change in reservoir pore pressure and stress state, the evolution of reservoir properties, the development of potential fracturing and the reactivation of existing faults. This geomechanical modeling consists of an initial stress simulation prior to production and a coupled reservoir simulation due to depletion and/or injection activities. A very representative initial stress state can be simulated using this approach and can be well calibrated with stress measurements from wireline logs, borehole breakouts and regional stress. Based on the simulated initial stress state, the change in pore pressure due to depletion and/or injection is used to compute the change in effective stress and associated reservoir deformation. The production history and observed reservoir deformation in the past can be simulated. Reservoir performance and associated reservoir deformation can also be predicted in the future production. A full field study using the VISAGETM System was performed to help assess the integrity of the development plan in South Arne field, North Sea. The predicted stress and strain changes that were induced by production/injection were used to assess the wellbore stability, potential for faults reactivation, cap rock integrity and rock fracturing. This study demonstrates that coupled geomechanical modeling lends direct support to drilling operations and reservoir management.
A Porothermoelastic Wellbore Model in Oil and Gas Saturated Naturally Fractured Porous Media
Authors: Nair Rajesh , Abousleiman Younane
Published: May 2009

The impact of initial oil saturation and presence of fractures on hole stability has been analyzed using a three-dimensional, fully-coupled multi-phase finite element model. The model accounts for thermo-hydro-mechanical coupling as well as solubility of gas in oil and evaporation of oil into gas in both the rock matrix and fractures. In addition, the viscosities of the oil and gas phases, formation volume factors for oil and gas, gas-oil solubility ratio, oil volatility ratio and the saturations are assumed to be dependent on the temperature. The model is verified with analytical solutions for the limiting case of a medium saturated with a single fluid. A parametric study is carried out varying the initial oil saturation and fracture parameters and the changes to the stress state around the wellbore are assessed. A preliminary analysis of failure study shows that the presence of fractures and lower initial oil saturation increases the failure potential.
Drilling and Completing Horizontal Wells in Unconsolidated Sandstone Reservoir in Saudi Arabia; A Rock Mechanics View
Authors: Rabaa Ali S. , Abass H. H. , Mousa Talal S
Published: May 2009

Drilling horizontal wells is a common practice for Saudi ARAMCO in most of its oil and gas reservoirs of Saudi Arabian clastic and carbonate fields. A comprehensive study of rock mechanical properties with detailed analysis of the in-situ stress field was conducted to evaluate well stability during drilling and completion across a friable eolian oil-bearing sandstone reservoir. This paper discusses the application and implementation of the study to successfully drill and complete development horizontal wells in a challenging sandstone reservoir.

All horizontal wells were completed with different type of sand screens including Premium and Expandable Sand Screen (ESS). It is vital to obtain a near-gauge hole during drilling for a maximum stability of the screen during the life of a well. It is therefore important to prevent excessive compressive shear failure at the wellbore wall and avoid instability problems during drilling and completion. Therefore, an optimum confining pressure to the wellbore surface needs has been derived. The recommended mud type and weight windows derived from the study have been employed while drilling producers but not with injectors. The correlation between the mud weights and the in-situ stress magnitude will be discussed.

Well stability during drilling and long term screen integrity is dependant on the well azimuth relative to the in-situ stress field. The azimuth of the maximum horizontal stress, SHmax, was determined to generally line up in the E-W direction. The wellbore stability problems experienced in this direction as well as those drilled normal to it (i.e., N-S), will be addressed.

In regards to stability of very weak and friable formation intervals (such as those encountered in the, dunes and sand sheet facies), the operational practices are focused on creating gauged hole with least erosion effect as a critical measure to deploy the ESS; thus, ensuring successful completion and sustained production. The effect of mud on rock strength was evaluated during the foregoing study; therefore, results from using oil-base mud will be discussed and compared to results from the wells drilled with water-based mud.
Performance of Hot Water Injection in Heterogonous Reservoirs using Multilateral Wells
Authors: Alajmi Abdullah F. , Gharbi Ridha , Algharaib Meshal
Published: May 2009

The use of multilateral wells in the oil industry has increased rapidly during the last decade. The main reason for this upsurge is that these wells provide large contact areas with the reservoir and therefore better recovery performance is achieved. In addition, the availability of new technologies in recent years has substantially reduced the cost of drilling these wells. In fact, in many areas of the world, drilling multilateral wells is becoming the norm when deciding to drill new wells. Furthermore, the continuous growth in the world oil demand stimulates the oil producers to develop all kind of resources including heavy oil reserves. The significant heavy oil accumulations already existed in the world has led to a greater emphasis on their development using thermal EOR methods. This study investigates numerically the performance of using multilateral well configurations in recovering heavy oil from heterogeneous reservoirs using hot water flooding. In order to cover a wide range of heterogeneity, a series of reservoir permeability maps, each with different permeability structures and variations, were generated stochastically. In each of these heavy oil reservoirs, extensive three-dimensional, fine-mesh simulation runs were performed using different configurations of multilateral wells. The oil recovery performance obtained by hot water flooding was compared to that obtained by conventional water flooding in all these reservoirs. The objective was to determine the functional relationships between the oil recovery performance and several design parameters including: (1) degree of heterogeneity (2) well configurations, and (3) viscosity ratio. Results show that these parameters play important roles in the displacement behavior of heavy oil using multilateral wells, with reservoir heterogeneity having a more significant effect. The study suggests that there exist critical values of these parameters under which hot water floods can be more effective than conventional water floods. The paper will present these conditions in detail and situation where the performance of hot water floods can be ineffective.
Nano-Technology - Its Significance in Smart Fluid Development for Oil and Gas Field Application
Authors: Amanullah Md. , Al-Tahini Ashraf M.
Published: May 2009

Nanotechnology application can revolutionalise the additive characteristics and behaviour by tuning particle properties to meet certain operational, environmental, and technical requirements. Hence, the nanotechnological research leading to create some tailored made nanoparticles could be a promising step change research for smart fluids development for different industrial applications. These particles are ultra fines in nature, usually larger than an atom cluster but smaller than ordinary micro particles and thus have very high specific surface area with enormous area of interactions. Due to nano-scale particle dimension, the nano-type fluid additives have both external as well as internal inhibition potential, require a very low additive concentration and thus expected to provide superior fluid properties at a drastically reduced additive concentration.

Nano-particles with high thermal stability and affinity to acid gases such as H2S and CO2 will help meet the technical challenges of sour gas environment, deep and geothermal drilling and thus expected to complete a well economically and safely with a drastic reduction in oil and gas exploration and exploitation risk. Identification, screening, selection, and/or development of nontoxic, environment friendly and biodegradable nano-particle-based drilling fluids are expected to meet the current as well as the future environmental norms and regulations for drilling and production in deep water and sensitive environments.

This paper provides a detailed description of the likely benefits of emerging nano-particle-based additives in smart fluid design for oil and gas field application, especially for a new generation of drilling and drill-in, completion, stimulation, fracturing, etc fluids for trouble-free drilling, completion and production of oil and gas resources.
Technology and Team-Based Approach Yields Saudi Arabia's Longest Fully Cemented Horizontal Liner
Authors: Ramos Marlio Campos , Hussein Sameh , Wedewer Kirby , Dieker Ansgar
Published: May 2009

Saudi Aramco's "M" Field is located offshore and will be developed using over 300 wells with a combination of land and offshore drilling facilities.

Well number M-A is a land-based, power water injector well, drilled to an offshore bottomhole location. The resulting well design dictated directionally drilling an extended-reach well with an 8-1/2-in. horizontal-hole section over 13,900 ft (4237 m) in length.

It was apparent from the outset that directionally drilling the 8-1/2-in. section was going to be extremely challenging. Once drilled, running and cementing the 7-in. liner would present a host of additional difficulties. To ensure a successful outcome, Saudi Aramco assembled a dedicated team of Operator and Service personnel to review all aspects of this openhole section and resulting liner running operations.

The latest in directional drilling technology was used to ensure the exacting directional control needed to deliver the wellbore. In addition, running the over 14,400-ft- (4389-m)-long liner required the use of new and innovative liner hanger technology to overcome any challenges encountered during liner deployment.

This paper will outline the planning, methods, and equipment applied to deliver the resulting 8-1/2-in. hole section, and successfully deploy Saudi Arabia's longest-ever cemented 7-in. liner.
New Completion Methodology to Improve Oil Recovery and Minimize Water Intrusion in Reservoirs Subject to Water Injection
Authors: Sierra Leopoldo , East Loyd , Kulakofsky David
Published: May 2009

Water injection during the early stage of a new reservoir's development is gaining popularity around the world. This is especially true in Saudi Arabia where water injection is used to improve oil recovery and for pressure maintenance by placing short or long horizontal water-injection wells around the reservoir flanks.

For cases where water-injection wells are placed in reservoir flanks, some of the producing wells are perforated transversally oriented to the water-injection wells to improve the oil recovery around the involved areas. For this specific exploitation strategy, there is a potential risk of water channeling from the injector to the producing well toe which, once it happens, might jeopardize recovery efficiency.

For the referenced exploitation strategy, a new completion methodology considering the placement of a fracture barrier at the toe of the producing well to delay water intrusion and improve recovery efficiency is proposed. This paper discusses the process to create the fracture barrier and the benefits of the completion methodology supported with extensive simulations for the different scenarios.
Innovative Approach for Water Injection Trees Integrity
Authors: Al-Rufaie Yousef A. , Al-Tammar Hasan I. , Al-Kady Alaa
Published: May 2009

The majority of the PWI wellheads injection trees in the Ghawar field have already passed their half-life time designated by the manufacturer and others have even completed their life cycle. Several operating factors were considered during the initial design stages of these trees based on the operating circumstances. The alloy (steel) of the PWIs composite trees have been selected to cope with the anticipated flow media, such as seawater, high injection pressures and rate (3,000 psig), frequent valve cycling and the life lasting expectancy was set for 20 years.

Nowadays, despite frequent valve care maintenance through the ongoing valve care program, the integrity of these valves has become susceptible to failure more than ever. The failures are caused either internally due to seats ring and ball damage, or externally due to flange leaks due to "O" rings and groove damage. In addition to the harsh operating conditions, aging is also another major cause for valves' integrity deterioration.

The innovative idea is to utilize synthetic valve care sealants to temporarily stop valve internal leaks (internal passing) by injecting a sealant through the ball valve's upper and lower grease fittings that are directly related to valve seats and sealing area, Fig. 2. The dual function of the lubricants/sealants is to clean hard deposits4, lubricate sealing elements and fill-in the internal channels and grooves. By doing so, the seats get pushed against the ball valve body sealing area, resulting in 100% pressure seal from both directions. The above stated idea is in use now as we speak, and has proven its practicality in the field to resolve valve leakage issues and make job executions arrangements simple and cost-effective.
Long Term Evaluation of a New Liquid Resin Additives used for Fracture Conductivity Enhancement in a Gas Producer Screenless Completion, Jauf Reservoir, Saudi Arabia
Authors: Leal Jairo , Solares J. Ricardo , Al-Ghurairi Fadel , Sierra Leopoldo
Published: May 2009

Jauf is a high pressure/high temperature gas producer sandstone reservoir, which exhibits a high sanding tendency in some zones throughout the reservoir. To combat the sanding tendency, Saudi Aramco has implemented two screenless sand control strategies by performing the indirect proppant fracturing process. The first or older strategy combines a number of techniques such as, indirect fracturing from oriented perforated thin consolidated zones, tip screenout design, use of a combination of resin coated proppant with fibers, forced closure, and a carefully controlled flowback procedure. The second strategy combines the indirect fracturing from oriented, perforated-thin consolidated zones, tip screenout design and the use of the new liquid resin additives.

Although a solids-free high rate gas production has been achieved in the majority of wells for which the first strategy was implemented, a high reduction in fracture conductivity in the form of positive skin has been detected from pressure buildup tests conducted in a number of fractured wells. Al-Ghurairi et Al (SPE 98088) explained the reasons for the positive skin and it was associated with partial penetration, given that the interval from which a fracture is initiated is usually perforated in high Young's Modulus rock and limited to 30-40 feet; thus the fracture is initiated away from the high sanding tendency zones and extended vertically into such zones. The other main component for the positive skin was attributed to the fibers used for proppant flow back control purposes, since it is well known through extensive industry testing, that the combination of proppant and fibers can reduce fracture conductivity in treated wells.

Supported by extensive lab testing showing that the combination of the two new resin additives, mixed with proppant, could provide effective solids and proppant flowback control without reducing fracture conductivity; the second strategy was implemented in the field, in December 2004. The initial outstanding results of this first pilot application were documented in the paper1 SPE 98088. After the initial evaluation the well was closed, up to the second quarter of 2006, to finish the surface production facilities.

This paper is a continuation of paper SPE 98088 and it discusses the long-term evaluation results and benefits of the new liquid additives used to improve and sustain the fracture conductivity.
Droplet Size Analysis of Emulsified Acid
Authors: Al-Mutairi S. H. , Nasr-El-Din H. A. , Hill A. D.
Published: May 2009

Emulsions have been used for many applications in the petroleum industry for many decades. Emulsified acid has been used in acid fracturing and well acidizing since 1933. A large number of fracturing treatments that used emulsified acid has been reported in the literature. Another fair number of researchers conducted lab experiments utilizing the emulsified acid. However, all of this work cannot be reproduced because of inadequate characterization of the emulsion. One essential way to characterize emulsions is by their droplet size. Various mixing modes and proportions produce emulsions with different size distributions for the dispersed phase. Those physical variations are believed to generate different properties (viscosity, stability, etc) of the emulsions.

The main objective of this paper is to provide a detailed description of the droplet size distribution of emulsified acids. Methods to measure and represent the data are the core of this section. We show that coarse or fine emulsions can be produced by selecting the mode of mixing and speed of shearing. Simple mixing and low shearing produce coarse emulsions whereas atomizing and high shearing produce fine emulsions. It is also demonstrated that the droplet size and specific surface area are affected by emulsifier concentration and acid volume fraction. Average droplet size decreases with increasing emulsifier concentration. The diameter also increases with increasing acid volume fraction. The specific surface area of the droplets increases with increasing emulsifier concentration and decreases with increasing acid volume fraction.

The change of droplet size has a practical impact on the stability, rheology and reactivity of emulsified acid. Good understanding and characterization of the emulsified acid by its size distribution will lead to advancements in this area.
High Speed Network for Intelligent Field Data Acquisition
Authors: Almadi Soloman , AL-Khabbaz Fouad , AL-Walaie Soliman , AL-Harbi Saad , AL-Amri Ali , AL-Gharairy Hussain
Published: May 2009

Process Control systems are embarking on a new wave of opportunities driven by Information Technology developments in infrastructure and system integration. Currently, most process and control systems consist of multiple, separate networks with limited interconnectivity. On the other hand, and due to the rapid developments of Information Technology, desktop computer system, Internet and Ethernet technologies are becoming increasingly suitable for use in the Manufacturing and Process Control sectors. This means that for the first time computer and communication structures based on Ethernet/Internet technology can be extended throughout the entire company. This paper provides an overview of the network, technology, and topologies utilized for an optimal High Speed Network for Oil and Gas Field Data Acquisition systems.
An Innovative Multi-Reservoir Permanent Downhole Monitoring System through a Single Well
Authors: Al-Omair Abdullatif , Ukaegbu Orji O. , Alshafie Muhammed , Shafiq Muhammad , Almarri Abdullah
Published: May 2009

This paper describes an innovative Down Hole Permanent Monitoring System (PDHMS) that allows real-time monitoring of bottom-hole pressure and temperature of two stacked reservoirs using one vertical observation well in a Saudi Aramco field.

Permanent monitoring of pressure and temperature enables reservoir engineers to assess the performance of the reservoir in areas such as flood front movement and pressure support maintenance. In this well a multi-reservoir dual gauge system was deployed to monitor pressure and temperature in two stacked carbonate reservoirs.

The standard dual-gauge system mandrel architecture requires below packer installation of the gauges which in turn increases the risk of leakage in the electric lines of the system. In this paper, we describe an innovative and potentially reliable digital permanent monitoring solution that uses the state-of-the-art welded system that aims to eliminate the risk of leakage.

Included in the paper are the design criteria, deployment methodology and the "lessons learned" from installation of this fully welded PDHMS.
Optimizing Proppant Conductivity and Number of Hydraulic Fractures in Tight Gas Sand Wells
Authors: Abass Hazim , Sierra Leopoldo , Tahini Ashraf
Published: May 2009

A substantial future potential for gas production lies in tight gas reservoirs with porosity of 5-8% and permeability less than 0.1 mD (micro-Darcy range). To construct a commercial well in these reservoirs, a well must contact as much as possible a large drainage area of the reservoir. Therefore, wells drilled in these challenging reservoirs must be hydraulically fractured to yield commercial gas production rate. The number of hydraulic fractures and their conductivities are vital parameters to ensure production increase and production sustainability during the life of the well. This paper focuses on the proppant fracture conductivity and the optimum number of fractures required along a horizontal well in a tight gas sand (TGS) reservoir.

The flow system in TGS reservoirs include matrix and natural/induced hydraulic fractures that contribute to the gas transport in a very complex manner. Laboratory tests were performed to determine the stress dependant permeability as a function of stress. A tensile natural fracture was simulated by splitting a whole core by failing it under tension using a Brazilian test procedure. The tensile fractured core was then propped with a small mesh proppants and the permeability of the propped fracture was determined. The experimental results of stress dependant permeabilities provided a basis for optimum fracture conductivity based on the flow properties of the porous components of a given reservoir (matrix, natural fractures, and propped fractures).

The results from the experimental phase were employed in a reservoir simulation study to determine the optimum fractures along a horizontal well required to convert a marginal well into an economic well. A series of reservoir simulation runs were performed given a set of well and reservoir characteristics. Common factors include reservoir properties, PVT, drainage area, well geometry, and created fracture geometry. The controlling factors include number of fractures, reservoir permeability, skin damage, and fracture conductivity. The number and optimum fracture conductivity required for appreciable production increase in tight gas reservoirs is demonstrated. A comparison between stress dependant and the stress independent permeabilities indicates the importance of including the effect of stress in any reservoir simulation of tight gas reservoirs.
Application of Hybrid Fracture Treatment to Tight Gas Sands in East Texas Cotton Valley Sands
Authors: Sani Abu M. , Nadezhdin Sergey V. , Villarreal Ruben , Chabernaud Thierry , Brown Ernest J.
Published: May 2009

Hydraulic fracture treatments are necessary to ensure the best deliverability of tight gas from east Texas Cotton Valley Sands. Historically these treatments have been performed using a wide variety of techniques using a range of fluids including slick water, linear gel, crosslinked polymers and CO2 emulsions. Most of the productive sands are associated with nearby water sands that are often intersected by the hydraulic fractures as their heights grow which results in high water production and a subsequent significant reduction in produced gas. An integrated engineering process of reservoir and production analyses was used to evaluate the stimulation treatment carried out for several offset wells throughout the field. The analyses determined the fracture geometry: fracture length, fracture conductivity, and permeability. The results were then used to calibrate a log-derived permeability and stress models. An advanced petrophysical analysis using these models improved the identification and characterization of potential movable water zones. A perforation scheme was proposed to minimize intersecting the water sands. Several stimulation techniques based on the rock mechanical model of the sands were evaluated. These included treatment with slick water, crosslinked polymer, hybrid (combination of slick water and crosslinked gel), CO2-based emulsions, and viscoelastic fluids. A high-rate hybrid treatment was selected because of the fracture geometry it would generate: bigger width, longer length, and minimal height growth.

The first new well came on production with a significantly low water-gas-ratio (WGR), from a first-year average of 483 bbl/MMscf for the offset wells to 135 bbl/MMscf for the new well. The first-year gas from this new well was more than double that of the offset wells average (163 MMscf versus 65 MMscf) and 88% higher than that of the best offset well. The polymer concentration was lowered to ensure better and earlier cleanup. On the next well drilled in the area, the same hybrid treatment was applied only to the portion of the Taylor sand located in the Cotton Valley sands. It came on line with higher gas production than the offset wells. For the first 6 months, total gas produced was 56 MMscf compared with the 40-MMscf average of the offsets, and the WGR was 147 bbl/MMscf compared with 397 bbl/MMscf.
Nanofluid Coreflood Experiments in the ARAB-D
Authors: Kanj Mazen Y. , Funk Jim J. , Al-Yousif Zuhair
Published: May 2009

This paper addresses a critical step on the road to having in-situ reservoir agents. It targets the limiting size of these devices and endeavors to model their transport mechanisms in the rock matrix. It also details an experimental study on nanofluid coreflood experiments in the ARAB-D formation of the giant Ghawar field in Saudi Arabia. The study aims to test the feasibility and future reality for displacing molecular nanoagents in the reservoir. The testing objectives, process, and results are further detailed herein.
Modeling Complex Dispersive Capacitance in Carbonates using NMR T2 Distributions
Authors: Funk James J. , Al-Harbi Ahmad M.
Published: May 2009

One frequently used model for miscible displacement in carbonates uses a capacitance mass exchange process to model both concentration profiles as a function of position and effluent profiles as a function of time. The capacitance effect in carbonates is quantified as a concentration driven mass exchange between a poorly connected system (stagnate fraction) and the miscible flowing fraction.

In a simple yet elegant experiment we have been able to expand this model to carbonate rocks that contain bi-modal pore size distributions. By combining experimental single phase dispersion tests with continuous nuclear magnetic resonance (NMR) T2 distribution measurements we observe directly velocity and concentration gradients. Results illustrate that the micro-porous system in select skeletal-oolitic rock types is preferentially connected and that intra-pore system fluid transport is more pronounced than that occurring between micro and macro pore systems. Using a combination of effluent and in-situ measurements we are able to model time dependent capacitance effects not apparent with the conventional capacitance dispersion model. The new model accurately captures early micro-macro system fluid exchange and late time capacitance effects modeled using effluent profiles.
Late Summer Management Can Improve Forage Yield Distribution and Nutritive Value in Temperate Grassland
Authors: Arzadun Martín J. , Mestelan Silvia A.
Published: May 2009

Chemical defoliation (glyphosate spraying) at the end of summer and fertilization are practices proposed to improve winter forage availability in native grasslands of the Flooding Pampa of Argentina. However, there is no preceding work comparing the effect of either practice on the yield and botanical composition of these grasslands. In 2002 and 2003, three defoliation treatments were applied in mid‐February: control (C) without summer defoliation; severe summer defoliation (D) to 2‐ to 3‐cm stubble height and glyphosate, isopropylamine salt of N‐[phosphonomethyl] glycine, G, applied at 2.2 kg a.i. ha−1. Additionally, the effect of three rates of N, 0, 35, and 70 kg N ha−1and P, 0, 11, and 22 kg P ha−1 applied in combination with the three late summer defoliation treatments were researched. Early changes during fall in the biomass components ryegrass (Lolium multiflorum Lam.), warm‐season grasses (WSG), dead matter, and litter were evaluated after defoliation treatments. The effect of defoliation treatments along with N and P fertilization was followed on seasonal and annual forage yield, botanical composition, in vitro dry matter digestibility (IVDMD), and crude protein (CP). Glyphosate application increased annual ryegrass contribution while reducing WSG and legumes, mostly narrow leaf trefoil (Lotus tenuis Waldst & Kit.) and annually yielded 29% less forage dry matter (DM) than the intense mechanical defoliation. Forage IVDMD and CP were increased by D and G in fall the first year. In the second year CP was low in G in winter and spring. Changes in botanical composition can explain the differences observed in quality DM traits. Fertilizer increased forage yield 2 to 10 kg DM per kg N and 8 to 24 kg DM per kg P applied. Severe defoliation applied in late summer increased fall and winter forage availability and quality without the negative effect on legumes observed with glyphosate that had a negative impact on DM accumulation and quality in spring.
Estimating Mean Field Residue Cover on Midwestern Soils Using Satellite Imagery
Authors: Gelder B. K. , Kaleita A. L. , Cruse R. M.
Published: May 2009

Knowledge of residue cover is crucial for targeting conservation efforts to reduce soil erosion, runoff, and associated environmental impacts; however, a rapid, accurate, inexpensive methodology is not currently available. Previous studies have shown mixed results detecting crop residue using Landsat residue indices, but conditions generally included poor soil color contrast, emergent vegetation, or categorized residue cover. Our objectives were to evaluate a new normalized difference residue index (NDRI), along with other indices, over multiple image dates in 2005 and 2006 on dark soils in north‐central Iowa. An automated method for field boundary delineation was used. The NDRI, using Landsat Bands 3 and 7, performed best overall, explaining 81% of the residue cover differences overall, 78% before emergence, and 9% after emergence. The normalized difference tillage index (NDTI), using Landsat Bands 5 and 7, also performed well explaining 68% of the variation overall, 86% before emergence, and 6% after emergence. Introduction of an empirical correction of the influence of green vegetation improved index performance. The NDTI outperformed the NDRI after green vegetation correction, explaining 67% of the variation versus 63%. The NDTI also returned the best RMSE (0.11) under preemergence conditions, and 0.15 after green vegetation correction. Generally, indices utilizing Landsat Band 7, which contain lignin and cellulose absorption bands absent in soil, returned the best residue detection results. Indices utilizing Landsat Band 4, where the reflectance of green vegetation is high, had difficulty detecting residue cover, especially after plant emergence.
Legume Cover Crops are More Beneficial than Natural Fallows in Minimally Tilled Ugandan Soils
Authors: Mubiru Drake N. , Coyne Mark S.
Published: May 2009

It is important to establish the various effects of legume cover crops on soil physicochemical properties because they have been considered for use as improved fallows (with shorter rest periods) to enhance development and maintenance of soil productivity. Our objectives were to assess: (i) aboveground dry matter yields of legume cover crops; and (ii) cover crop effects on weed infestation and soil physicochemical properties in a minimum tillage management system. Trials were conducted for 2 yr at Kawanda Agricultural Research Institute and on farmers' fields in Mbale and Pallisa districts, eastern Uganda. The experiment layout was a Randomized Complete Block Design (RCBD) in a split‐plot arrangement with four replications. Natural and improved fallows were established in the second cropping season of 2004. Cover crops used in the improved fallows included mucuna [Mucuna pruriens (L.) DC.var. utiliz], Dolichos lablab (Lablab vulgaris Savi cv. Rongai), canavalia [Canavalia ensiformis (L.) DC.], and crotalaria (Crotalaria paulina Schrank). The fallows were reestablished in the same plots in the second cropping season of 2005 after maize (Zea mays L.). Canavalia yielded significantly more dry matter than the other fallows regardless of year or site. With an average yield of 169 kg N ha−1 canavalia accumulated significantly more N than the other fallows; all improved fallows produced significantly more N than the natural fallow. Canavalia also accumulated significantly more P than the other fallows; all improved fallows, with the exception of crotalaria, accumulated more P than the natural fallow. There was no significant change in soil physicochemical properties by the improved fallows. All effects considered, improved fallows were more beneficial than natural fallow. A significant improvement in soil physicochemical properties using legume cover crops might be possible, though it may require more than the two cropping cycles used in this study of degraded soils.
Crop Rotation, Wheat Straw Management, and Chicken Manure effects on Soil Quality
Authors: Limon‐Ortega Agustin , Govaerts Bram , Sayre Kenneth D.
Published: May 2009

New crop rotation and adequate fertilizer management are needed to maintain productivity of high input irrigated wheat (Triticum aestivum L.) systems. This study was initiated in 1998 in northwest Mexico. The objective was to examine the effects of two straw managements (incorporated or burned), three crop rotations [wheat‐sesbania (Sesbania spp.), wheat‐maize (Zea mays L.), or wheat‐fallow], and the application for wheat of three N fertilizer sources (urea, chicken [Gallus gallus] manure, or a mixture of both) at two rates (0 and 200 kg N ha−1) on soil properties. Soil microbial biomass C and N, soil N, P, K concentrations, pH, sodium absorption ratio, electrical conductivity, aggregate size distiribution and stability were evaluated in 2001, 2002, and 2005 during the wheat cropping seasons. Straw management had no consistent effect on the amount of carbon mineralized from the soil microbial biomass (SMB C). Planting sesbania as a summer crop after harvesting wheat in the spring enhanced both SMB C and N. The effect of straw management and crop rotation on aggregate size distribution was minimal. Chicken manure application increased the soil N, P, and K concentration. Potassium was accumulated after burning residues. Enhancing rotation complexity and reducing fallow by including summer maize or sesbania increased the soil organic matter. To enhance the measured soil attributes wheat should be followed by a crop like sesbania in the summer and the use of organic manure should be combined with an inorganic N source allowing a balanced application of nutrients as required by the crop.
Corn Response to Conventional and Slow‐Release Nitrogen Fertilizers across a Claypan Landscape
Authors: Noellsch A. J. , Motavalli P. P. , Nelson K. A. , Kitchen N. R.
Published: May 2009

Improvement of N fertilizer recovery efficiency (NRE) is necessary to reduce excess N entering the environment and to increase economic returns. A 2‐yr field trial was established in 2005 in Northeast Missouri to determine the effects of conventional and slow‐release N fertilizer sources and landscape position (summit, sideslope, and low‐lying) on crop growth and NRE in corn (Zea mays L.) in a claypan soil. Nitrogen fertilizer treatments at 168 kg N ha−1 consisted of pre‐plant applied and incorporated polymer‐coated urea (PCU), urea, 50% PCU/50% urea mix by weight, anhydrous ammonia (AA), and a nontreated control. Gravimetric soil water content data in 2005 and 2006 indicated that the low‐lying position was often wetter than the summit and sideslope positions. Anhydrous ammonia and PCU treatments increased grain yield 1470 to 1810 kg ha−1 over urea in the low‐lying position in 2005 and 2006. Corresponding increases in plant N uptake and NRE were observed in the low‐lying position in 2005 with use of PCU and AA compared to urea, but not in 2006. Based on the grain yield results in this research and different fertilizer cost and crop prices, gross profit differences for use of PCU and preplant‐applied AA compared with urea in the low‐lying position could range from $50 to $642 ha−1. These results demonstrate that targeted use of different N fertilizer sources in claypan landscapes may increase grain yields and profitability.
Soybean Production in a Kura Clover Living Mulch System
Authors: Pedersen P. , Bures E. J. , Albrecht K. A.
Published: May 2009

Increased demand for soybean [Glycine max (L.) Merr.] and high grain prices, have led many livestock producers to consider converting their perennial forage crop fields to production of row crops. The objective of this research was to determine whether established kura clover (Trifolium ambiguum M. Bieb.) can be suppressed and serve as living mulch for soybean production. The experiment was conducted in 2005 and 2006 near Arlington and Lancaster, WI. Five treatments were imposed in a randomized complete block design with four replications. Plots were subdivided for soybean grain harvest and for forage harvest. Treatments included (1) soybean planted into established kura clover that was killed by tillage (soybean control), or suppressed (2) two, (3) three, or (4) four times with herbicide, and (5) a kura clover control without any soybean. The soybean seed yield ranged from 1.53 to 5.10 Mg ha−1 and the soybean forage yield ranged from 1.42 to 5.90 Mg ha−1. Seed yield of soybean in the three living mulch treatments was 36% less than the mean yield of soybean in killed and tilled kura clover. There was a trend for increased yield with more herbicide applications although yield with four applications was significantly greater than with two applications in one site‐year only. Monoculture kura clover always yielded more forage than soybean in living mulch. Soybean forage yield was inconsistently affected by treatments and yield. Results from this study showed no obvious advantages, but additional risk, associated with soybean production in kura clover living mulch.
Transpiration and Yield Relationships of Grain Sorghum Grown in a Field Environment
Authors: Tolk J. A. , Howell T. A.
Published: May 2009

The ability of plants to convert transpiration (T) into dry matter has been studied since the early 20th century. Research has compared differences among species using transpiration efficiency (TE), the ratio of biomass yield (Yb) to T; and m and k, which are the slopes of the linear Yb/T relationship normalized by atmospheric evaporative demand. The objective of this research was to develop transpiration and biomass relationships (TE, m, and k) and the transpiration and grain relationship (TEg) of grain sorghum (Sorghum bicolor L. Moench) grown in a field environment. Grain sorghum was grown in 1998 and 1999 in weighable lysimeters using stored soil water only and in a rain shelter facility. This approach limited the irrigation and precipitation evaporation components of E so that T estimated (Test) using lysimetry in a field environment was emphasized. The TE remained constant through a range of water availability. The TE was similar between the 2 yr, and the combined data produced a slope of the Yb/Test relationship of 3.5 g m−2 mm−1. This was similar to the 3.3 g m−2 mm−1 reported for sorghum in the early 20th century, but smaller than current field studies which ranged from 4.0 g m−2 mm−1 to 5.7 g m−2 mm−1. The TEg was 2.6 g m−2 mm−1. Normalization of Test by seasonal averages of reference evapotranspiration and vapor pressure deficit produced significant differences between years in the slopes of the relationships. Transpiration efficiency did not require normalization for variations in climate between years.
Evaluating YieldTracker Forecasts for Maize in Western Kansas
Authors: Coyne P. I. , Aiken R. M. , Maas S. J. , Lamm F. R.
Published: May 2009

We seek to predict in‐season land productivity to guide irrigation management decisions designed to optimize water utilization in the Ogallala Aquifer region. YieldTracker is a mathematical model that simulates growth and yield of graminoid crops using weather and leaf area index (LAI) as inputs, where LAI can be derived by remote sensing. We tested this model using 3 yr of maize (Zea mays L.) yield data from Colby, KS. Four replications of three treatments—rainfed and subsurface drip irrigation (SDI) at 3.8 and 7.6 mm d−1—were compared with simulated yields (36 model runs). Results indicated that YieldTracker has potential as a decision aid for managing irrigated maize, but has insufficient mechanistic complexity to simulate yields of water‐stressed maize. YieldTracker projected canopy development well, but LAI does not necessarily correlate with canopy efficiency in capturing solar radiation and converting it to biomass and then partitioning biomass to grain under conditions of limiting soil water. Remotely sensed normalized difference vegetation index (NDVI), a surrogate for LAI, tends to saturate at LAI > 3. Using hyperspectral reflectance data, we found a total chlorophyll vegetation index (TCI) responded nearly linearly to LAI values as high as 6. Similarly, a simple ratio vegetation index, based on a narrow band of wavelengths in the red edge spectral region, responded linearly to increasing LAI. Water band indices (WBI) in the 900 to 970 nm waveband were sensitive to changes in TCI as available soil water decreased. Incorporating TCI and a WBI might improve YieldTracker performance across a range of soil water conditions.