bluuebunny/crossref_metadata_2025 huggingface dataset:
SAVING THE BEST FOR LAST? A CROSS‐SPECIES ANALYSIS OF CHOICES BETWEEN REINFORCER SEQUENCES
Authors: Andrade Leonardo F. , Hackenberg Timothy D.
Published: October 2012

Two experiments were conducted to compare choices between sequences of reinforcers in pigeon (Experiment 1) and human (Experiment 2) subjects, using functionally analogous procedures. The subjects made pairwise choices among 3 sequence types, all of which provided the same overall reinforcerment rate, but differed in their temporal patterning. Token reinforcement schedules were used in both experiments and the type of exchange schedule varied across blocks of sessions. Some conditions permitted immediate exchange of tokens for consumable reinforcers (food for pigeons, video access for humans); in other conditions, tokens accumulated and were exchanged for consumable reinforcers only at the end of the sequence. Choice patterns in the immediate‐exchange conditions were generally similar across species, with both pigeons and humans preferring sequences with the shortest delay to the initial reinforcer in the series. The results are broadly consistent with models of temporal discounting expanded to include the impact of sequences of delayed reinforcers acting in parallel from the time of the choice. Preferences were less consistent with discounting models in the delayed exchange conditions. Questionnaire data gathered at the end of the experiment were consistent with prior results of questionnaire studies, but showed no straightforward relation to the observed choice patterns, urging caution in the extrapolation of results from one decision‐making domain to the other.
Understanding Production Drivers and Challenges in Converting a Vertical to Horizontal Oil Play Utilizing Single Well Modeling
Authors: Gonzales Veronica M. , Barham Michael , Lawless Paul , Cherian Bilu V. , Mata Domingo , Higgins-Borchardt Shannon , Alatrach Samer
Published: October 2012

The recent growth in horizontal well technology has resulted in existing oil and gas vertical development plays to be evaluated for horizontal well applicability. As operators attmept to evaluate the criteria for converting from vertical well plays to horizontal well plays, sound data gathering and modeling become crucial to understand how completion strategies needs to be modified for improved production, without utilizing an expensive trial and error methodology.

The Powder River basin contains a variety of producing shales and sands currently being explored for vialibility (i.e. Niobrara, Frontier, etc). In this study, reservoir and fracture properties are estimated based on hydraulic fracture modeling, rate-transient analysis techniques and production history matching to calibrate log data measurements. The challenges associated with calibration and modeling measurements from petrophysical and rock mechanics models are compared with hydraulic fracture and production modeling results to understand the direction of optimization and future basin growth.

Past experiences are typically the basis for design and implementation of developing a new drilling and completion program. Interpretation of the hydraulic fracture behavior is often inferred from simple diagnostics, and as production ensues the repeatability for success or failure is often attributed to modifying the hydraulic fracturing program or geological influences, which is subject to inconsistency and qualitative introspection. Within this study a single well modeling approach is utilized to understand fracture geometry, correlate this with production history matching results, and distinguish production attribution from hydraulic fracture characteristics or reservoir properties. Exercising this workflow addresses challenges affiliated with modeling fracture propagation and production matching and the gap associated with horizontal well development in existing vertical plays.
Use of Untreated Subsurface Non-Potable Water for Frac Operations
Authors: Pettigrew Dana , Limanowka Andy
Published: October 2012

Fresh water is being extensively used for fracturing operations to stimulate both gas and oil shale wells. Once used for this purpose, the water is either disposed of, or needs extensive treatment to recondition it for further fracturing operations. Producers in the Horn River Basin have access to a huge underground non-potable aquifer that is deeper than the fresh water zones and shallower than the shale gas wells that require fracture treatment for stimulation. The question is, how to use this water resource to economically fracture stimulate the shale gas wells?

Extensive testing on the water quality of the Debolt aquifer indicated that the Debolt water remains stable if kept above the bubble point pressure, but existing positive displacement frac pumps cannot pump this water in its stable and untreated condition. However, a centrifugal pump can pump this water in its stable and untreated condition, but current designs are for 42 MPa maximum operating pressures, which are too low for use in shale well fracturing operations. A newly developed 69 MPa High Pressure Horizontal Pumping System (HPHPS) was designed and tested to provide a pump capable of utilizing raw Debolt water as a fracture fluid.

This paper will discuss the use of an HPS (Horizontal Pumping System) pump, designed to provide high pressures of up to 69 MPa, enabling this pump to be used as a High Pressure Horizontal Pumping System (HPHPS) frac pump.

This pump was successfully used in the Horn River Basin of North Eastern British Columbia to pump Debolt source water (a saline, sour and gassy aquifer), untreated during fracturing operations in 2010 and again in 2011. Additional testing of this prototype HPHPS frac pump is being conducted during the 2012 frac campaign. This paper will discuss the field operating procedures and performance of this style of pump during this large frac campaign.

Usage of an HPHPS frac pump also enables a Pressurized Frac On Demand (PFOD) system to be used to fully exploit the use of this method for water supply to a frac system.
Practical Analytical Model to Simulate Production of Horizontal Wells with Branch Fractures
Authors: Stalgorova E. , Mattar L.
Published: October 2012

A common way to produce hydrocarbons from tight reservoirs is to use horizontal wells with multiple hydraulic fractures. In many cases, fractures do not have a simple bi-wing shape, but are branched. For modeling purposes, branch-fracturing can be represented by a high permeability region near each fracture, while the bulk of the space between the fractures remains unstimulated.

This paper presents an analytical model to simulate the flow rate and pressures for such a reservoir system. The model is a variation on the tri-linear flow solution. It is simple, and flexible enough to be applicable to multi-frac horizontal wells. The model takes into account three linear flow regimes: flow within the fracture (at very early time), flow within the stimulated region towards the fracture and flow within the un-stimulated region towards stimulated region. The model was validated by comparing its results with synthetic data sets generated using numerical simulation; the results showed excellent agreement.

This paper illustrates the various flow regimes and how they are affected by reservoir and completion parameters. The characteristic features of each flow regime are demonstrated using typecurves. History matching of actual field case is presented to illustrate the practicality of the model. The proposed analytical solution provides a practical alternative to numerical solutions, and saves significant computational time.
An Experimental Study of Spontaneous Imbibition in Horn River Shales
Authors: Makhanov K. , Dehghanpour H. , Kuru E.
Published: October 2012

Fracture fluid flow back has been identified as one of the major challenges of hydraulic fracturing operations conducted in shale reservoirs. Factors causing the very low fracture fluid recovery need to be well understood and properly addressed, in order to get full benefits from costly hydraulic fracture jobs conducted in unconventional reservoirs. Despite the recent surge of investigations of the problem, one major question still remains: what happens to the fracture fluid that is not recovered? Does it stay in the fracture or does it go into the matrix? In case of both mechanisms are responsible for fracture fluid retainment, what fraction of fracture fluid stays in the propped fracture and what fraction is transferred from fracture to matrix. The focus of the current study is to understand if the transfer of fracture fluid from fracture to matrix through imbibition is of significant importance.

We systematically measure the imbibition rate of water, brine, and oil into the actual core samples from the three shale sections of Horn River basin (i.e., Fort Simpson, Muskwa and Otter Park). We characterize the shale samples by measuring, porosity, wettability, mineral composition through XRD analysis, and interpreting the well log data.

The results show that imbibition could be a viable mechanism for fluid transfer from fracture to matrix in Horn River shales. The comparative study shows the imbibition rate in the direction parallel to the bedding plane is higher than that in the direction perpendicular to the bedding. The study also suggests that the imbibition rate of the aqueous phases is significantly higher than that of the oleic phases.
Predicting Growth and Decay of Hydraulic Fracture Width in Porous Media Subjected to Isothermal and Non-isothermal Flow
Authors: Tran David , Settari A. (Tony) , Nghiem Long
Published: October 2012

Based on the continuum thermo-poroelastic theory, a new analytical formula of fracture width is developed to quickly predict its transient growth or decay. The effects of the poroelastic stress (also called backstress) and thermal stress are taken into account. The counterbalance between the effects of backstress and thermal stress (in case of injection of cold fluid) is shown to be a function of flow and thermal properties and can be easily demonstrated by the formula developed. The analytical formula of fracture width is not complicated and does not require complex calculations. Different phenomena affecting the magnitude of fracture width are easily examined, such as the presence or absence of leak-off, isothermal or non-isothermal fracturing as well as initial effective stress in the formation. Results show that the fracture width continuously decays with time due to the effect of pore pressure when there is leak-off. On the other hand, the fracture width will grow with time by the influence of thermal stress when cold fluid is injected. Unlike cold fluid, when hot fluid is used, the crack may close completely and the speed of the process will depend upon the temperature of the injected fluid. Formulae for penetration depths for pressure and temperature are also developed and applied to the crack width equation so that time-dependent maximum apertures and crack profiles can be computed. The analytical solution has also been validated by the finite element numerical method.
Fast Track Analysis of Shale Numerical Models
Authors: Kalantari-Dahaghi A. , Esmaili S. , Mohaghegh S. D.
Published: October 2012

Latest advances in shale gas reservoir simulation and modeling have made it possible to optimize and enhance the production from organic rich shale gas reservoirs.

Reservoir simulator is no longer used with a simple description of the complex shale gas reservoirs, but with multiple, equally probable realizations to allow risk assessment. Nevertheless, the perennial challenge in shale reservoir modeling is to strike a balance between explicit representation of reservoir complexity and long simulation run time for multiple realizations.

Focus of this study is on the development, calibration and validation of a Shale Surrogate Reservoir Model (AI-based proxy model) that represents a series of complex shale numerical simulation models. The Shale Surrogate Reservoir Model is then used for fast track analysis of the shale numerical model. Reservoir simulation model for a generic shale gas reservoir are constructed using a popular commercial simulator that is capable of handling complex fracture network (natural and multiple stages of hydraulic fractures), different sorption types (instantaneous and time dependent one), and capturing long transient nature of the flow in shale matrix. Validation of the Shale Surrogate Reservoir model using several blind simulation runs is also presented.

Shale Surrogate Reservoir Model is a replica for the numerical simulation model with response that is measured in fractions of a second. As such, it provides the means for comprehensive and fast track analysis of the model in a relatively short period of time, allowing the reservoir engineer to scrutinize different realizations and propose development strategies.
Recent Achievements Within E-Line Milling
Authors: MacLeod Anthony , Greenlee James , Henriques Kristine
Published: October 2012

Since the concept of milling obstructions on electric line (e-line) was introduced in 2005, operators around the world have applied this technique successfully removing downhole valves, plugs, scales, cement and nipple profiles achieving cost-effective and time-efficient interventions.

Recently, a series of e-line milling operations were performed to remove repeater-sub and ball-seat restrictions in oil producing horizontal wellbores located in Southeast Saskatchewan. The low pressure reservoirs favored intervention technologies that did not require excessive hydrostatic head. Operators have traditionally used nitrogen mixed with water to prevent damage to the reservoir and to maintain circulation; however, this reduces the amount of torque that can be achieved at the bit, and causes stalling and sticking issues.

Using a combination of tractor and milling technology on e-line in these wells provided the required torque for milling with a steady and constant weight on bit throughout the wellbore for removal of ball seat restrictions.

This paper presents the latest achievements within e-line milling in Canada. The paper will discuss best practices of date as well as a discussion of e-line milling challenges through three case studies in Canada.
Software Development for Petrophysical Analysis of Shale and Tight Formations
Authors: Yu Guang , Aguilera Roberto
Published: October 2012

Shale and tight formations have long been a challenge for petrophysical interpretation. In the case of shales, the presence of clays and organic matter, complex mineralogy and pore structure make the log responses complicated. In tight reservoirs, the presence of connected and non-connected dissolution pores, microfractures and slot porosity also complicates the interpretations. This work seeks to integrate and digitize new petrophysical techniques and procedures that address these problems into a software system to assist with shale and tight reservoirs characterization.

A petrophysics software system that includes dual and triple porosity models as well as elastic geomechanical properties has been developed to assist with the evaluation of shale and tight formations. Some critical petrophysical parameters can be quantified, such as matrix, fracture, non-connected and effective porosities, water saturation, total organic carbon, level of organic metamorphism, flow regimes (continuous vs. diffusion-like) at any pressure of interest, as well as Young modulus, Poisson’s ratio and minimum horizontal stress. Based on these estimates, detailed shale and tight reservoirs characteristics can be analyzed and the original hydrocarbons in place can be determined with good accuracy.

Practical workflows for calculating each parameter are also organized and integrated. Object-oriented programming techniques are utilized for the development of this software considering its development life cycle for large-scale software development. Optimization capacity adopted in the current development for the reuse of the software components for future development is also explained.

Two case studies using data from the Nikanassin formation in the Deep Basin of the Western Canada Sedimentary Basin (WCSB) and the Haynesville shale formation in Texas are presented to illustrate the software development and the application of the software. Conventional well log data, such as gamma ray, density, neutron, acoustic, resistivity, and cores and drill cuttings are utilized in the examples, which is further validated with other sources of information.

It is concluded that the methodology developed in this software will prove valuable and facilitate the petrophysical evaluation of shale and tight formations.
What Don’t We Know About Self Sourced Oil Reservoirs: Challenges and Potential Solutions
Authors: Larter Steve , Huang Haiping , Bennett Barry , Snowdon Lloyd
Published: October 2012

While light tight oil reservoirs such as found in Bakken and Cardium style plays can be stimulated by fracturing, significant oil production from true shale reservoirs dominated by clay size fraction sediments may not be feasible, even when reservoirs are fractured, if current oil storage models in source rocks are valid. We look at the source rock knowledgebase and the gaps in our understanding relevant to assessing oil production from shale sections. Despite over four decades of study of petroleum source rocks by geochemists, our mechanistic understanding of them remains at best qualitative and inadequate for quantitative reservoir characterisation purposes. Past studies emphasised molecular chemistry details and gross mass balance studies at large scale, but only few detailed mechanistic studies of actual physical process and transport function during generation and primary migration are available. Empiricism and generality dominate current concepts and most R&D peaked in the 1980s when Oil Company R&D spending was at its highest, but declined after that. Today there are many areas of uncertainty, but reassuringly, research is starting again and crucially, abundant core samples, which were largely absent before, are now also available. There has also been a revolution in the understanding of shale sedimentology which forces us to reexamine many of our earlier precepts about source rock formation and suggests that in the absence of naturally fractured silica or carbonate intervals within source rocks, such as found in the Monterey Fm., very small scale collateral silt and sand horizons may be locally important small scale reservoirs in typical shales. The bulk of the oil storage in source rocks however is in kerogen, where dominantly diffusive rather than Darcy flow processes operate and where fracturing may have little impact on productivity. We look at the technical barriers, both theoretical and analytical, to understanding true shale dominated reservoir oil production potential.
Integration of Production Data for Estimation of Natural Fracture Properties in Tight Gas Reservoirs Using Ensemble Kalman Filter
Authors: Nejadi Siavash , Leung Juliana , Trivedi Japan J
Published: October 2012

Productivity in deep-basin tight gas reservoirs can be improved significantly by natural fracture enhanced permeability. Therefore, deviated and horizontal wells are often drilled to intersect highly fractured formations. Unfortunately, fractured reservoirs are highly heterogeneous, often characterized by probability distributions of fracture properties in a discrete fracture network (DFN) model. In addition, the relationship between recovery response and model parameters is vastly non-linear, rendering the process of conditioning reservoir models to both static and dynamic (production) data challenging.

In the current paper, a novel approach is presented for uncertainty assessment and characterization of fractured reservoir model parameters using data from diverse sources. First, Monte Carlo based techniques were used to generate multiple DFN models conditioned to geological and tectonic information, accounting for the uncertainty associated with static data. Next, each model or realization was upscaled for flow simulation. Finally, Ensemble Kalman Filter (EnKF), a data assimilation technique that has been used for assisted history matching, was employed to update the DFN models using production data. In order to ensure positive definiteness of the updated permeability tensors, to reduce the size of model parameter space, and to eliminate the redundancy between parameters for improved convergence, principal component analysis was performed such that only the main principal components of the full permeability tensor and sigma factors were updated through EnKF algorithm.

The qualities of the history-matched models were assessed by comparing the spatial distribution of the updated model parameters with the initial ensemble, as well as the Root Mean Square Error (RMSE) of the predicted data mismatch. The results clearly demonstrate that, characterization of fractured reservoirs combining DFN modeling with updating principal components of the upscaled model parameters through EnKF has the potential to resolve the shortfall of traditional techniques for history matching of such complicated reservoirs. The proposed approach can be used effectively to update reservoir models and optimize development plans in unconventional gas reservoirs using continuous flow and pressure measurements.
A Simplified Engineering Model Integrated Stimulated Reservoir Volume (SRV) and Tight Formation Characterization With Multistage Fractured Horizontal Wells
Authors: Zhao Gang
Published: October 2012

Stimulated Reservoir Volume (SRV) is an engineering concept developed for the purposes of quickly evaluating the effective well drainage area and analyzing the actual performance of a multistage horizontal well in tight formation. Usually SRV is defined using microseismic event mapping. However, there are many other factors hindering the realization of the correct SRV value and largely impairing its engineering application.

A simplified integrating model with multiple regions that combines the near wellbore engineered reservoir area, the SRV region, the original tight formation area and the outbound reservoir region, named as region I, II, III and IV, respectively, were built and analyzed systematically, where the region I confines the horizontal wellbore with multiple artificial hydraulic fractures and allows the integration of complex skin factor distribution, region II intends to capture the influence of SRV under various parametric settings such as fracture networking and matrix-fluid mobility variations, region III accommodates the general geological information for the original large scale tight formation environment and region IV supports the information input for the outbound reservoir environment.

The multiple region modeling has been successfully built and applied to understand the relationship among wellbore, fracture, SRV and original reservoir formation. Theoretical study on the transient pressure and rate responses were conducted to address the technical challenge encountered. The results, presenting in a type curve format under various conditions, have shown that SRV region is strongly related to the fracture influenced/dominated boundary flow regime and appears as a region possessing a less than 1 slope in pressure and reciprocal rate derivative curves, which indicates that the flow process has reached the theoretical SRV boundary, i.e., the fracture influenced area/boundary. However, the derivative value would not reach one due to the inflow from the outside original reservoir region. This phenomenon is a symbolic feature of tight formation with SRV connectivity, as many field cases have been so indicated.

This work allows a quick estimation of SRV region, a better understanding of the influence of the complicated wellbore configurations and a way to characterize the reservoir connectivity between SRV and original/outbound tight formation reservoir.
Potential Investigation of Shale Gas Reservoirs, Southern China
Authors: Wei C. , Wang H. , Sun S. , Xiao Y. , Zhu Y. , Qin G.
Published: October 2012

The shale gas development has more than 3 decades of history. In China, the development is still in the early stage due the technology limitation. The estimated technically recoverable shale gas reserve is 882 Tcf in China. The predicted shale gas production in 2020 is 3.5 Tcf which will contribute 26% of natural gas consumption in China. In order to stabilize the gas output to meet the demand of economic development, increasing recoverable shale gas reserve becomes more and more important.

In this study, a Qiongzhusi reservoir was taken as an example to investigate the potential of shale gas in southern China. The methodologies involved in this investigation include experimental study on core analysis with Total Organic Content (TOC) and Vitrinite Reflectance, outcrops study, geostatistical analysis, and geo-modeling. Besides these methods, an irreplaceable step was to compare the reservoir conditions of given reservoir with successful developments in Barnett and Marcellus in the United States.

By integrating all above technologies and methods, the study forecasted the sedimentary facies, estimated shale gas distribution, and evaluated the petrophysical properties of the shale play. The result indicates that most of the Qiongzhusi reservoirs have promising thickness, favorable kerogen type (type I), high TOC, and encouraging maturity. This paper also predicted favorable zones in the middle and upper Yangtze area with properties of thickness more than 60 meters, TOC not less than 2.0%, and Vitrinite Reflectance from 2.5% to 4.6%.

The study would bring the reservoir engineers and geologists with detailed evidence to support the development of Qiongzhusi reservoirs, and furthermore, it offers the methodology to the research of other shale plays with similar properties.
Multiwell Analysis of Multifractured Horizontal Wells in Tight/Shale Gas Reservoirs
Authors: Nobakht M.. , Clarkson C. R.
Published: October 2012

Shale gas reservoirs have become a significant source of gas supply in North America owing to the advancement of drilling and stimulation techniques. Long horizontal wells completed with multiple-fracturing stages (MFHW) are the most popular method for exploiting shale gas reservoirs today and therefore, development of analysis methods for analyzing production data from these wells has gained tremendous attention in the last decade. The analysis methods developed so far are aimed to obtain understanding of fracture length, fracture conductivity, stimulated reservoir volume (SRV), contacted gas-in-place and other information for a MFHW being analyzed. Although single well analysis methods are of tremendous value, the industry also needs analysis methods for analyzing a group of MFHWs. In this paper, analysis methods developed for single well analysis of MFHWs are extended to analyze a group of MFHWs. These analysis methods are proved to be very useful for cases that adjacent wells are in communication (ex. fracturing one well affected the production of the adjacent wells). It is shown how these methods help engineers to diagnose and characterize the communication between MFHWs and use the results to optimize the size of frac job and spacing between horizontal wells in tight/shale gas plays.
Quantification of cm-Scale Heterogeneities in Tight-Oil Intervals of the Cardium Formation at Pembina, WCSB, Alberta, Canada.
Authors: Solano N. A. , Krause F. F. , Clarkson C. R.
Published: October 2012

A detailed, fine-scale, reservoir characterization study of (light) tight oil rock intervals in the Cardium Formation is performed using an innovative combination of X-Ray CT Scan technology, hardness and profile (probe) permeability measurements. This study aims to quantify the geometry, degree of heterogeneity, and several other key properties, of individual microlithofacies within the highly bioturbated sandstone lithofacies.

Contrasting bulk density values between these microlithofacies domains is identified using X-ray CT-Scan imagery reconstruction. Statistical analysis yields numerical information regarding geometry and connectivity of individual bodies for a given microlithofacies within the analyzed volume. Permeability, as estimated from a profile (probe) permeameter, and hardness of the samples, as quantified using a hardness index (from Leeb Hardness measurements), is investigated for a sub-centimeter 2D grid on slabbed surfaces. This detailed mapping allows the analysis of mm- to cm-scale correlations between rock quality and CT images.

Identified microlithofacies include SS1 and SS2 (sandstones), SH1 (shale), and PB (pyrite-filled burrows). Permeability can exceed 50 mD in SS1 microlithofacies, but generally is less than 1 mD for SS2 and 0.01 mD for SH1. Volumetric reconstruction of these microlithofacies yields approximately 85% total sandstone content for an average sample from tight-oil Cardium lithofacies (which is higher than visual assessment of 50-60% sandstone). The sandstone ratio of SS2/SS1 is between 3 and 5; microlithofacies SH1 and PB have a patchy distribution through the core. SS1 appears as highly disturbed relics of very thinly bedded patches, and sandstone-filled, subhorizontally oriented, sub-centimeter scale burrows. Relatively higher values of bulk density and hardness index characterize SS2 and SH1 microlithofacies.

The overall low permeability usually measured in this lithofacies can be attributed to the complex interplay between biological and physical sedimentary structures at the cm-scale, generating more or less randomly connected volumes with contrasting flow and storage capacity. This study provides a roadmap for more accurate property measurements and modeling at the core scale for this complex lithofacies of the Cardium Formation; we believe that this will also be useful for other tight oil reservoirs.
Evidence of Reopened Microfractures in Production Data Analysis of Hydraulically Fractured Shale Gas Wells
Authors: Apiwathanasorn Sippakorn , Ehlig-Economides Christine
Published: October 2012

The triple porosity analytical model provides a way to account for shale gas production from multiple hydraulic fractured horizontal wells that may have reopened a network of microfractures in the shale during hydraulic fracturing. This behavior has also been analytically modeled as multiple parallel finite conductivity hydraulic fractures in a dual porosity formation. In theory these models may reveal a series of flow regimes exhibiting linear, bilinear, and even trilinear flow. In practice, characterizing the various flow regimes is challenging because typically only one or two of them are likely to appear in any one transient data set.

This work concludes possible theoretical flow regime combinations which may be seen in fractured shale gas wells based on the dual and triple porosity models. Then sensitivity studies are investigated using typical shale gas formation and completion parameters to identify under what conditions in practice the transient data may reveal the flow regimes sensitive to microfractures and how likely or unlikely the those flow regimes could be present in field data.

Investigation of production rate and pressure field data from Barnett and Horn River shale formations illustrates that confirmation of a reopened fracture network, or "complexity", as this has been called by some authors, is not obvious even though some cases show the model related to reopened fracture network yield better matches than the homogeneous model.

This work emphasizes that interpretation using different models may yield significantly different results while still matching the observed behaviors equally well. Though buildup data may help to reduce uncertainties of parameters related to features visible at very early time, the variation of production forecast and recovery estimation is still expected if the model predicts large volume of reopened fracture network with ultra-low shale matrix permeability.
Influence of privatization of water delivery on access to the right to water in Kenya
Authors: van de Loo Elsa
Published: October 2012

This article analyses the influence of privatization of water resources on access to the right to water in Kenya. It is premised on the belief that water is a fundamental human right and must not be seen as a social or economic good. Attention will be given to national-, regional- and international legislation and proposals on the right to water, water as a human right and the privatization of water resources. This article is based on literature study and interviews.
Participation in the implementation of the Water Framework Directive in Denmark: The prospects for active involvement
Authors: Wright Stuart A.L. , Jacobsen Brian H.
Published: October 2012

Public participation in the form of informing, consulting and actively involving all interested parties is required during the implementation of the Water Framework Directive (WFD). This paper discusses progress with implementation of the WFD in Denmark and the measures taken to conform to the requirements for public participation. The first aim of the paper is to establish whether enough is being done regarding participation in Denmark, the conclusion being that whilst Denmark is in line with statutory requirements, consultation appears limited whilst evidence of active involvement is lacking. The paper then presents the Danish AGWAPLAN project which actively involved farmers in selecting measures to reduce diffuse nutrient pollution from agriculture. The second aim of the paper is to establish whether nationwide implementation of the AGWAPLAN concept is worthwhile. AGWAPLAN resulted in outcomes which could potentially increase the effectiveness of the WFD. Furthermore, the adoption of the project approach would also be one way to satisfy the requirement for active involvement in the Directive. However, some problems exist, relating to time, administrative costs, problems with control and the fact that additional measures to reduce N leaching would be necessary. Whether national implementation is worthwhile requires the weighing up of the advantages and disadvantages of the concept, which is ultimately a political decision.
Modelling regional general equilibrium effects and irrigation in Canterbury
Authors: Alexander Lennox James , Diukanova Olga
Published: October 2012

We describe the development of a regional computable general equilibrium (CGE) model for the analysis of issues concerning water supply and (re)allocation in Canterbury, New Zealand. Traditionally, water has been seen as an abundant resource, but growing irrigation demands are now outstripping the supply of water and competing with in-stream uses and non-use values. In the longer term, this problem may be exacerbated by climate change, which is predicted to increase water demands and reduce supply in parts of Canterbury. It is important to be able to quantify the impact on the regional economy of changes in water availability and policies and other measures addressing water supply or demand. A particular concern is the current, relatively inflexible, ‘first-come, first-served’ system for water allocation. In this paper, we present some preliminary scenarios focusing on a reduction of irrigation supply and the interaction with changes in rainfall. These results are intended only to illustrate the potential of the modelling approach, not least because the provisional data to which the model is currently calibrated are in many cases dated or incomplete. We discuss how the model and its underlying database may be improved and extended to provide results that are qualitatively robust and policy-relevant.
Obstetric Nephrology
Authors: Umans Jason G.
Published: October 2012

Preeclampsia, a common and potentially devastating multisystem disorder unique to human pregnancy, represents a novel form of secondary hypertension with complex renal and systemic effects. Recent translational and clinical research reveals key pathophysiologic contributions due to dysregulation of angiogenic factors and of angiotensin signaling. Despite these insights, there are still difficulties in the clinical definition of preeclampsia and in the diagnosis of women with this disorder. Although recent research suggests the potential for new preventive and treatment strategies, most have not yet been shown ready for clinical use.
„Fieldwork in philosophy“: Geertz and Bourdieu in dialogue
Authors: Spasic Ivana , Gorunovic Gordana
Published: October 2012

Unlike the standard view that Clifford Geertz and Pierre Bourdieu embody
contrary social scientific paradigms, it is argued that they share a whole
set of similarities in terms of theory, research practice, and scholarly
ethics. After briefly presenting the details of their encounter in the early
1970s, the authors identify the following points of their implicit and
unintended convergence: 1) blurring of interdisciplinary boundaries, 2) work
in North Africa, 3) relation to important predecessors, 4) commitment to
fieldwork and rejection of ?grand theory?, 5) postpositivism and
anti-postmodernism, and 6) reflexivity. At the same time, irreducible
differences between the two are noted, marking the outer limits of this kind
of comparative analysis. Finally, it is argued that Geertz and Bourdieu
missed the opportunity to enter a genuine dialogue and learn from each other
lessons that may have helped them improve their respective scholarly
projects.
Is There Life after the Complete Loss of Analyst Coverage?
Authors: Mola Simona , Rau P. Raghavendra , Khorana Ajay
Published: October 2012

This paper examines the value of sell-side analysts to covered firms by documenting the effects on firm performance and investor interest after a complete loss of analyst coverage for periods of at least one year. We find that analyst coverage adds value to a firm both because it reduces information asymmetries about the firm's future performance and because it maintains investor recognition for that firm's stock. After the introduction of regulations that curtailed the informational advantage of analysts in the early 2000s, the investor recognition role of analysts remains important. Firms that lose all analyst coverage continue to suffer a significant deterioration in bid-ask spreads, trading volumes, and institutional presence but do not show a significant difference in subsequent performance relative to covered peers. In addition, controlling for other factors, we find that firms that lose all analyst coverage for one year are significantly more likely to delist than their covered peers. Our results provide insight into the reasons why firms place so much importance on analyst coverage.
Spindle Cell Rhabdomyosarcoma of the Neck with t(6;8) Translocation: Report of a Case and Literature Review
Authors: Mentrikoski Mark J. , Golden Wendy , Bourne T. David , Legallo Robin
Published: October 2012

Spindle cell rhabdomyosarcoma is an uncommon subtype of embryonal rhabdomyosarcoma. Found almost exclusively in children, these tumors are classically located in the paratesticular and head and neck regions. Morphologically these lesions can resemble several other benign or malignant soft-tissue spindle cell lesions, especially smooth muscle or myofibroblastic tumors, and thus immunohistochemical staining is often needed to prove skeletal muscle differentiation. Although there is extensive literature reporting the genetics of embryonal rhabdomyosarcoma, little is reported specific to the spindle cell subtype. Below we present the case of a 7-month-old male presenting with a large posterior neck mass that was diagnosed as spindle cell rhabdomyosarcoma. Karyotype evaluation revealed a t(6;8) (p12;q11.2) chromosomal translocation within the lesion. We review the histologic and immunohistochemical diagnosis of these tumors and discuss the genetics of rhabdomyoscarcomas.
Nontraumatic Intradural and Subdural Hemorrhage and Hypoxic Ischemic Encephalopathy in Fetuses, Infants, and Children up to Three Years of Age: Analysis of Two Audits of 636 Cases from Two Referral Centers in the United Kingdom
Authors: Scheimberg Irene , Cohen Marta C. , Vazquez Rita E. Zapata , Dilly Susan , Adnani Mudher Al , Turner Kerry , Sethuraman Chitra
Published: October 2012

We analyzed the presence or absence of intradural hemorrhage (IDH) and subdural hemorrhage (SDH) and the degree of hypoxic-ischemic encephalopathy (HIE) in the brain of all nonmacerated fetuses of >24 weeks, neonates, and children up to 3 years of age who died of natural causes over a defined period. We looked into the cause of death and the performance of cardiopulmonary resuscitation in our cohort. The IDH was classified as macroscopic or negative/microscopic only; the HIE was classified as absent, indeterminate, or definite. In fetuses, SDH with IDH was present in 22%; IDH alone was present in 31%, and there was no or minimal hemorrhage in 47% of cases. In infants and children SDH with IDH was present in 19%; IDH alone was present in the 32%, and there was no or minimal hemorrhage in 49% of cases. There was a statistically significant correlation between SDH and HIE, especially in infants and children ( P < 0.001). When cases were grouped per age, a significant association between age and hemorrhage ( P < 0.0001) was demonstrated, SDH being more common in infants ≤1 month corrected age. Intradural hemorrhage can be the source of thin-film SDH in fetuses, infants, and young children. The presence of SDH is associated with hypoxia. Intradural and subdural hemorrhages are more common in autopsies of infants under 1 month corrected age. Although more rare, they can also be found in children between 1 month and 3 years of age in the absence of trauma.
Neonatal Alloimmune Thrombocytopenia Associated with Massive Chronic Intervillositis: A Case Report and Review of the Literature
Authors: Tchakarov Amanda , Coffey Amy , Tatevian Nina
Published: October 2012

Neonatal alloimmune thrombocytopenia (NAIT) presents as isolated thrombocytopenia in a normal neonate as a result of destruction of fetal platelets by maternal antibodies against paternally derived human platelet antigens. Neonatal alloimmune thrombocytopenia affects 0.1% of births, with maternal antibodies crossing the placenta as early as 14 weeks' gestation. Few reports describe placental histopathological changes occurring in NAIT cases. We present a case of NAIT associated with massive chronic intervillositis, a rare entity occurring in 0.06% to 0.8% of reviewed 2nd- and 3rd-trimester placentas; to our knowledge, this is the 1st report of such an association.
Caregiver placebo effect for dogs with lameness from osteoarthritis
Authors: Conzemius Michael G. , Evans Richard B.
Published: October 2012

Objective—To document the caregiver placebo effect in owners and veterinarians of dogs with lameness from osteoarthritis.

Design—Prospective, randomized, double-blinded, placebo-controlled, multicenter clinical trial.

Animals—58 dogs with lameness secondary to osteoarthritis.

Procedures—Dogs enrolled in the placebo arm of an FDA-approved study were evaluated to determine the relationship between subjective (caregiver responses) and objective (force platform gait analysis) patient outcome measures.

Results—A caregiver placebo effect for owners evaluating their dog's lameness occurred 39.7% of the time. A caregiver placebo effect occurred 44.8% of the time when veterinarians examined dogs for lameness at a walk, 44.8% of the time when veterinarians examined dogs for lameness at a trot, and 43.1% of the time when veterinarians evaluated dogs for signs of pain on palpation of the joint. This effect was significantly enhanced with time. Mean ground reaction forces (GRFs) remained unchanged for dogs during treatment with the placebo. Individually, of 58 dogs, 5 had GRFs that worsened by ≥ 5% over 42 days, 7 had GRFs that improved by ≥ 5% over 42 days, and 46 had GRFs that remained unchanged.

Conclusions and Clinical Relevance—A caregiver placebo effect was common in the evaluation of patient response to treatment for osteoarthritis by both pet owners and veterinarians. Force platform gait analysis was an unbiased outcome measure for dogs with lameness from osteoarthritis. A caregiver placebo effect should be considered when interpreting owner and veterinary reports of patient response to treatment.
Parathyroid hormone concentration in geriatric cats with various degrees of renal function
Authors: Finch Natalie C. , Syme Harriet M. , Elliott Jonathan
Published: October 2012

Objective—To determine whether cats in the nonazotemic stages of chronic kidney disease have increased plasma parathyroid hormone (PTH) concentrations as a compensatory physiologic mechanism to maintain plasma phosphate concentration within the reference interval.

Design—Prospective longitudinal study.

Animals—118 client-owned geriatric cats with various degrees of renal function.

Procedures—For each cat, a blood sample was obtained for plasma biochemical analysis and determination of plasma PTH concentration, and a urine sample was obtained for determination of urine specific gravity at study entry (baseline) and after 12 months. For a subset of 30 cats, plasma calcitriol concentration was determined at baseline. Cats were categorized into 1 of 3 groups on the basis of kidney function at the end of 12 months. At baseline and after 12 months, plasma concentrations of variables associated with calcium homeostasis were compared between the 3 groups and also within groups over time. Multivariable linear regression was used to identify variables associated with plasma PTH concentration.

Results—Plasma PTH concentration was significantly increased in cats that developed azotemia, compared with PTH concentration in cats that remained nonazotemic, and PTH concentration increased before changes in plasma calcium and phosphate concentrations were detected. A moderate positive association between plasma calcitriol and PTH concentrations was identified. Plasma PTH concentration was associated with age and plasma urea, creatinine, and total calcium concentrations in the final multivariable model.

Conclusions and Clinical Relevance—Results suggested that renal secondary hyperparathyroidism can develop prior to azotemia in cats, even in the absence of hyperphosphatemia and hypocalcemia.
Evaluation of hemostatic and fibrinolytic markers in dogs with ascites attributable to right-sided congestive heart failure
Authors: Zoia Andrea , Augusto Monica , Drigo Michele , Caldin Marco
Published: October 2012

Objective—To determine whether dogs with ascites secondary to right-sided congestive heart failure (CHF) have bleeding disorders associated with hypofibrinogenemia and discordant plasma fibrin-fibrinogen degradation products (FDPs) and D-dimer assay results (ie, a circulating concentration of FDPs higher than the reference range and a circulating concentration of D-dimer within the reference range).

Design—Retrospective case-control study.

Animals—80 client-owned dogs.

Procedures—Dogs with ascites secondary to right-sided CHF (group 1; n = 20), unhealthy dogs without cardiac disease (group 2; 40), and dogs with left-sided CHF (group 3; 20) were included in the study. Urine bile acids-to-creatinine concentration ratios were calculated as a marker of liver function. Differences among groups regarding coagulation profile analysis results and prevalence of discordant FDPs and D-dimer assay results were determined.

Results—No significant differences were detected among the 3 groups regarding urine bile acids-to-creatinine concentration ratios. Plasma fibrinogen concentration was significantly lower for group 1 versus groups 2 or 3. Prevalence of discordant FDPs and D-dimer assay results was significantly higher for group 1 versus groups 2 or 3. Eighteen group 1 dogs had discordant FDPs and D-dimer assay results. Ten of these dogs had concurrent hypofibrinogenemia, 2 of which had clinical signs of bleeding. Only 10 dogs in groups 2 or 3 had discordant FDPs and D-dimer assay results; none of these dogs had hypofibrinogenemia or clinical signs of bleeding.

Conclusions and Clinical Relevance—Dogs with right-sided CHF and ascites may be at increased risk for primary hyperfibrinogenolysis (ie, hypofibrinogenemia and discordant FDPs and D-dimer assay results).