bluuebunny/crossref_metadata_2025_split huggingface dataset:
Wildfire provides refuge from local extinction but is an unlikely driver of outbreaks by mountain pine beetle
Authors: Powell Erinn N. , Townsend Philip A. , Raffa Kenneth F. 
Published: September 2011

Bark beetle outbreaks and wildfire are important disturbances in conifer ecosystems, yet their interactions are not well understood. We evaluated whether fire injury increased susceptibility of lodgepole pines (Pinus contorta) to mountain pine beetle (Dendroctonus ponderosae Hopkins), how it influenced beetle reproductive success, and whether beetle population phase altered this interaction. Eight sites that experienced wildfire and eight unburned sites were examined in the Greater Yellowstone Ecosystem (USA). Half were in areas where D. ponderosae was undergoing outbreaks, and half were in areas with low populations. We examined 2056 trees one year after fire for burn injury and beetle attack. We quantified beetle reproductive success in a random sample of 106 trees, and measured gallery areas of D. ponderosae and competing subcortical herbivores in 79 additional trees. Baited flight traps sampled stand‐level populations of subcortical herbivores and predators.Wildfire predisposed trees to D. ponderosae attack, but nonlinearly, with moderately injured trees being most preferred. This tree‐level interaction was influenced by stand‐level beetle population size, in that both healthy and fire‐injured trees of all classes were attacked where populations were high, but no healthy trees, and only low and moderately injured trees were killed where populations were low. The number of adult brood produced per female was likewise curvilinear, being highest in moderately injured trees. This reflected an apparent trade‐off, with high intraspecific competition arising from the large number of beetles needed to overcome defenses in healthy trees, vs. high interspecific competition and low substrate quality in more injured trees.These results suggest that fire‐injured trees can provide a reservoir for D. ponderosae during periods when populations are too low to overcome defenses of healthy trees, and might otherwise face localized extinction. However, the likelihood of populations increasing from endemic to outbreak levels in response to increased susceptibility is offset by the opposing constraints of lower substrate quality and higher competitor load in severely injured hosts, and the relative scarcity of moderately injured trees. Wildfire may confer some reproductive increases to populations already outbreaking. We present a conceptual model of how these disturbances and inherent feedbacks interact to affect beetle population dynamics.
Performance and Economic Evaluation of Cyclic-Pressure Pulsing in Naturally Fractured Reservoirs
Authors: Artun Emre , Ertekin Turgay , Watson Robert , Al-Wadhahi Majid , Miller Bernie 
Published: September 2011

Summary
Gas cyclic-pressure pulsing is an effective improved-oil-recovery (IOR) method in naturally fractured reservoirs. A limited number of studies concerning this method in the literature focus on specific reservoirs, yet the optimum operating conditions have not been broadly investigated. In this study, we present a detailed parametric study of the process from both operational and reservoir perspectives. Incremental oil production, discounted incremental oil production, and net present value (NPV) are considered as the important markers for the performance criteria. The necessary analyses are performed using a single-well, dual-porosity, compositional reservoir model. In the first part of the study, parametric studies are conducted to develop a better understanding of the operational parameters affecting the process performance in the shallow, naturally fractured, and depleted reservoir of Big Andy field in eastern Kentucky, USA. These include analyses of various design parameters (e.g., soaking period, cycle rate limit, number of cycles, cycle, and cumulative injected-gas volumes). In the second part of the study, reservoir characteristics are investigated. Comparative discussions are presented between cases with CO2 and N2 as the injected gas on reservoir fluids of different compositions (heavy, black, and volatile oils). Influences of area, thickness, fracture/matrix permeabilities, initial reservoir pressure, and temperature on the process are studied. It is observed that N2, as a lower-cost gas, would be a better choice than CO2 in the Big Andy field. With the oil price used in this study, the cost of injected gas becomes relatively insignificant in economic considerations. Increased income from increased oil production overcomes the increased costs with higher volumes of gas. The way reservoir characteristics affect the process performance is similar in cases with CO2 and N2, but differs significantly with different reservoir fluids. Thicknesses ranging between 20 and 50 ft produced more favourable results than thicker reservoirs. A higher efficiency was observed with smaller drainage areas (5 to 8 acres) in the presence of heavy oil. For the cases with volatile and black oil, it is observed that the process efficiency is not altered significantly by the area. The phase behaviour of the reservoir fluid is important for the performance of the process. Initial pressure/temperature of the reservoir and, therefore, the initial fractions of gas/liquid phases affect the process efficiency in a more pronounced manner.
Multinode Intelligent-Well Technology for Active Inflow Control in Horizontal Wells
Authors: Sun Kai , Guo Boyun , Saputelli Luigi 
Published: September 2011

Summary
Nonequalized production influx along a horizontal or inclined wellbore is believed to be responsible for early water/gas breakthrough in oil-production wells. Nonequalized water-injection distribution has been recognized as a cause of poor sweep efficiency in waterflooding. The nonequalized fluid flow is attributed to reservoir heterogeneity and frictional pressure drop along the wellbore. A practical means of minimizing the problem is to use inflow control devices (ICDs) between isolation packers to adjust the production influx or injection distribution within the isolated compartments. However, the ICDs are passive devices (i.e., once they are set in place in a completion string, they cannot be adjusted to ensure equalized flow when reservoir conditions change during oil production or water injection). This paper introduces a new technology called the multinode intelligent well system (MNIWS) that is under development and will be soon available to the industry.
Starting with analyzing the data from an existing horizontal well with an ICD installation, a different completion design scenario was investigated for the well using the MNIWS. Computer modeling of well performance shows that the MNIWS technology suite can equalize production influx and delay water breakthrough into the horizontal wellbore more effectively than the conventional ICD completion when the inflow condition changes during the well's life.
An Improved Triple-Porosity Model for Evaluation of Naturally Fractured Reservoirs
Authors: Al-Ghamdi Ali , Chen Bo , Behmanesh Hamid , Qanbari Farhad , Aguilera Roberto 
Published: September 2011

Summary
Many naturally fractured reservoirs are composed of matrix, fractures, and nontouching vugs (there can also be any other type of nonconnected porosity that can occur; for example, in intragranular, moldic, and/or fenestral porosity). An improved triple-porosity model is presented that takes these different types of porosities into account. The model can be used continuously throughout a reservoir with segments composed of solely matrix porosity, solely matrix/fractures, solely fractures/vugs, or the complete triple-porosity system.
The model improves a previous triple-porosity algorithm by handling rigorously the scale associated with each: matrix, fractures, and vugs. This permits determining more-realistic values of the cementation or porosity exponent, m, for the composite system and consequently improved values of water saturation and reserves evaluations. The values of m for the triple-porosity reservoir can be smaller than, equal to, or larger than the porosity exponent of only the matrix blocks, mb, depending on the relative contribution of the vugs and fractures to the total porosity system.
It is concluded that not taking into account the contribution of matrix, fractures, and vugs in the petrophysical evaluation of triple-porosity systems can lead to significant errors in the determination of m, and consequently in the calculation of water saturation, hydrocarbons in place, and recoveries, and ultimately can lead to poor economic evaluations—either too pessimistic or too optimistic. This is illustrated with two examples from Middle East carbonates.
Combining Resistivity and Capture Sigma Logs for Formation Evaluation in Unknown Water Salinity--A Case Study in a Mature Carbonate Field
Authors: Minh C.Cao. Cao , Saldungaray P.. , Belowi A.R.. R. , Ong L.W.. W. , Al-Mudhhi M.A.. A. 
Published: September 2011

Summary
Formation evaluation in unknown water salinity can be performed by solving simultaneously for Sw and Rw from the logs of resistivity and sigma. This has not been used extensively in the past because the logs are often acquired on wireline at various times, leading to unknown invasion effects that complicate the integration of the deep-reading resistivity and the shallow-reading sigma logs. We will show that when the two measurements are free from invasion effect and other interpretation parameters (such as porosity and Archie m and n) are reasonably known, the technique works well and gives reliable Sw and Rw answers.
Both numerical and graphical solutions are presented. The numerical technique uses a minimization routine to solve for a salinity value that is consistent with Sw calculated from resistivity and from sigma. The salient point of the paper is the graphical technique that provides better insights into petrophysics than a set of equations. It uses an overlay of equisaturation and equisalinity lines superimposed on the crossplot of sigma vs. resistivity data. The overlay dynamically changes as porosity, lithology, hydrocarbon type, temperature, and other parameters vary with depth. The graphical technique has several applications. For the interpretation, it is used to estimate Sw and salinity, and to identify zones of changing properties. For quality control, it is used to validate the input data. For processing, it is used to select parameters and analyze their sensitivities to the results. For job planning, it is used to validate (or invalidate) the application from input values of resistivity and sigma. The graphical technique provides a valuable aid to the petrophysicist and gives an independent verification of the numerical solution.
The proposed technique is illustrated with wireline induction and sigma logs acquired in several wells in a mature Middle East carbonate field. The studied wells are completed in open hole and are flowed during logging to ensure that both resistivity and sigma logs are free from invasion effect. The results of the resistivity/sigma technique compare very favorably with those of carbon/oxygen (C/O) logging. Moreover, production-logging data confirmed the results and showed that the resistivity/sigma technique provides more-robust answers than C/O in low-porosity formations (below 15 p.u.).
Quantifying the Risk of CO2 Leakage Through Wellbores
Authors: Loizzo M.. , Akemu O.A.P.. A.P. , Jammes L.. , Desroches J.. , Lombardi S.. , Annunziatellis A.. 
Published: September 2011

SummaryLeakage through new or existing wellbores is considered a major risk for carbon dioxide (CO2) geological storage. Long-term effective containment of CO2 is required, and the presence of millions of suspended or abandoned wells exacerbates the potential risk in mature hydrocarbon provinces. Accurate estimates of risk profiles can support the acceptance of geological storage and the adoption of economically effective risk-prevention and -mitigation measures.Reliable data about long-term containment of CO2 are almost nonexistent, so wells that exhibit a similar risk profile (such as gas storage, gas production, and steam injection) should be used as a proxy to assess failure rates and consequences for cemented wellbores.Statistical data about occurrence of leaks and their consequences are analyzed to determine the risk profile of CO2 leaks. A smaller sample of data about leak rates is also analyzed to provide their statistical distribution. Rates and consequences are then compared to try to assess the order of magnitude of major and catastrophic leaks.Hydrothermal CO2 leaks in natural analogs are also reviewed to compare the distribution of leak rates and the consequences upon health, safety, and environment of CO2 releases to soil and atmosphere.Analysis of existing data will show that major leaks are likely to occur in less than two wells per 1,000, with the overwhelming majority of CO2 leaks being small and with limited or negligible consequences.Given their risk profile, CO2 wellbore leaks should be addressed through a routine risk-management approach. Their frequent occurrence requires effective prevention measures, such as understanding leaks and adapting and deploying practices to minimize their occurrence. On the other hand, their low impact ensures maximum effectiveness of mitigation measures, such as monitoring. Because leaks can be detected long before damage ensues, they can be observed to predict their long-term consequences and to plan the most effective intervention without unnecessary immediate operation shutdowns.In conclusion, the recommended course of action is to focus on risk prevention and early detection. This implies the evolution from a "no-leaks" attitude (even for negligible leak consequences) to one that seeks no damage and relies on tight surveillance.
Lateral Buckling—The Key to Lockup
Authors: Mitchell Robert F. , Weltzin Tore 
Published: September 2011

Summary
Conventional wisdom suggests that buckled pipe first forms a plane buckled configuration, then transitions to a helical shape as the axial load increases. The helical configuration has been studied extensively using analytic solutions that allow calculation and analysis. Lateral buckling has received much less attention because no analytic solution exists for smooth pipe. Most conclusions about lateral buckling are just guesses. Tool joints have received some analysis, and buckling calculations, both lateral and helical, have been made for pipe with connectors, but these calculations have received little attention from the industry.
Buckling tests (Weltzin et al. 2009) were performed in the Ullrigg U2, a 2020-m research well with a buildup and 60° tangent geometry. These tests represent a major advance in the understanding of drillstring buckling. Although there have been many laboratory-scale studies and a few full-scale tests of limited value, this study is the first full-scale study to acquire a large amount of high-quality buckling-displacement data for analysis.
This paper presents the calculated drillstring positions for two loading tests performed in build and inclined sections of the Ullrigg U2 test well. Both tests were loaded until drillstring lockup. By lockup, we mean that no increase in load could be transmitted to the load sensor at the bottom of the drillstring with further decreases in hookload at the surface. In both cases, lateral buckling was the primary buckling mode, with only a short interval in the build-section tests showing actual helical buckling.
The results from the Ullrigg U2 tests show that connectors appeared to have primary importance in the buckling behavior of drillpipe, and lateral buckling was the primary mode of behavior. These results, which were not expected, will require considerable revision of the conventional buckling models with much more focus on the impact of connectors and a deeper understanding of lateral buckling. In particular, the analysis of casing running in extended-reach horizontal wells will be impacted significantly.
Damage Mechanisms in Unconventional-Gas-Well Stimulation—A New Look at an Old Problem
Authors: Shaoul Josef , van Zelm Lars , de Pater C.J.. J. 
Published: September 2011

Summary
After fracture stimulation of a tight gas well, production often rises slowly instead of showing an early transient. This indicates either severe reduction in fracture conductivity or reservoir damage. There is still no agreement in the industry about the most important damage mechanisms. Work performed by Pratts and Holditch in the 1970s showed that fracture-face damage from filtrate invasion is unimportant unless there is permeability damage in the invaded zone of at least 99%. New ideas have been proposed that may better explain the behavior commonly seen in actual tight gas well production data. These ideas include relative permeability with water and gas both immobile at a given saturation ("permeability jail"), small-scale reservoir heterogeneity, and stress-sensitive-matrix permeability at high drawdown.
Experience from the field has been contradictory. Sometimes no water is produced back, but gas production does not appear to suffer. In other cases, the gas rate is significantly lower than expected, but significant fracture fluid is recovered. With the inherent coupling of fracture length and permeability in well-test interpretation and the practical impossibility of achieving radial flow in tight-gas reservoirs with large fracture lengths, it has been difficult to prove any theory about the cause of poor performance from tight gas fracture treatments. This paper shows simulation results of a number of damage effects on post-fracture production from an unconventional (0.001-md) gas well. Furthermore, realistic assumptions about proppant-pack cleanup show a connection not only between poor cleanup and short effective fracture length, but also reduction in contacted kh and connected reservoir volume. New reservoir-simulation results are presented that show a 50% reduction of production in the first years because of these effects in unconventional reservoirs.
Clinical and histologic effects of intracardiac administration of propofol for induction of anesthesia in ball pythons (Python regius)
Authors: McFadden Michael S. , Bennett R. Avery , Reavill Drury R. , Ragetly Guillaume R. , Clark-Price Stuart C. 
Published: September 2011

Abstract
Objective—To assess the clinical differences between induction of anesthesia in ball pythons with intracardiac administration of propofol and induction with isoflurane in oxygen and to assess the histologic findings over time in hearts following intracardiac administration of propofol.
Design—Prospective randomized study.
Animals—30 hatchling ball pythons (Python regius).
Procedures—Anesthesia was induced with intracardiac administration of propofol (10 mg/kg [4.5 mg/lb]) in 18 ball pythons and with 5% isoflurane in oxygen in 12 ball pythons. Induction time, time of anesthesia, and recovery time were recorded. Hearts from snakes receiving intracardiac administration of propofol were evaluated histologically 3, 7, 14, 30, and 60 days following propofol administration.
Results—Induction time with intracardiac administration of propofol was significantly shorter than induction time with 5% isoflurane in oxygen. No significant differences were found in total anesthesia time. Recovery following intracardiac administration of propofol was significantly longer than recovery following induction of anesthesia with isoflurane in oxygen. Heart tissue evaluated histologically at 3, 7, and 14 days following intracardiac administration of propofol had mild inflammatory changes, and no histopathologic lesions were seen 30 and 60 days following propofol administration.
Conclusions and Clinical Relevance—Intracardiac injection of propofol in snakes is safe and provides a rapid induction of anesthesia but leads to prolonged recovery, compared with that following induction with isoflurane. Histopathologic lesions in heart tissues following intracardiac injection of propofol were mild and resolved after 14 days.
Evaluation of epidemiological, clinical, and pathological features of neuroaxonal dystrophy in Quarter Horses
Authors: Aleman Monica , Finno Carrie J. , Higgins Robert J. , Puschner Birgit , Gericota Barbara , Gohil Kishorchandra , LeCouteur Richard A. , Madigan John E. 
Published: September 2011

Abstract
Objective—To describe epidemiological, clinical, and pathological features of neuroaxonal dystrophy in Quarter Horses (QHs) on a single farm.
Design—Prospective case series.
Animals—148 horses.
Procedures—Neurologic, pathological, and toxicological evaluations were completed in selected neurologically affected horses over a 2-year period. Descriptive statistical analysis was performed.
Results—87 QHs and 1 QH-crossbred horse were affected. Most (50/88 [56.8%]) affected horses were 1 to 2 years old (median age, 2 years [range, 2 months to 34 years]). Neurologic deficits included obtundation (53/88 [60%] horses), decreased to absent menace response (33/88 [37.5%]), proprioceptive positioning deficits, wide-based stance, ataxia, and dysmetria (88/88 [100%]). Most (78/88 [88.6%]) horses had mild ataxia, but some (10/88 [11.4%]) had moderate to severe ataxia. Low serum concentrations of vitamin E (≤ 2 mg/L) were detected in 3 index case horses and 16 of 17 randomly selected horses (13/14 affected and 3/3 unaffected) during study year 1. Dietary vitamin E supplementation did not improve neurologic deficits in affected horses; vitamin E administration in pregnant mares appeared to decrease but not prevent disease development among offspring born the following year. Lesions detected at necropsy included bilaterally symmetric neuroaxonal degeneration with axonal spheroids in the nucleus gracilis, nucleus cuneatus medialis, nucleus cuneatus lateralis, and nucleus thoracicus (5/5 horses).
Conclusions and Clinical Relevance—Neuroaxonal dystrophy should be considered in evaluation of young horses with ataxia and proprioceptive positioning deficits. Vitamin E deficiency may contribute to disease severity.