bluuebunny/crossref_metadata_2025 huggingface dataset:
Estudio de la asociación entre neuropatía autonómica pupilar y retinopatía diabética en pacientes diabéticos tipo 2
Authors: Pérez Estepa Héctor , Rivera Rojas Lucy
Published: November 2015

La alteración pupilar en la diabetes se interpreta como una manifestación de la neuropatía autonómica y lesión microvascular, lo que se refleja en hallazgos fundoscópicos no normales. Objetivo: describir la asociación entre neuropatía autonómica pupilar y retinopatía diabética en pacientes diabéticos tipo 2. Materiales y métodos: estudio descriptivo analítico comparativo. Se incluyeron 76 sujetos, divididos en dos grupos, 46 pacientes diabéticos tipo 2 y 30 sujetos sanos (no diabéticos) mayores de 40 años. Se midió el diámetro y la velocidad de respuesta pupilar con una cámara de alta resolución en sistema de videoscopia, y evaluación de retina en cámara retinal. Resultados: se encontró diferencia entre la velocidad pupilar y HbA1c del grupo de pacientes diabéticos tipo 2 (0,512 mm/s DE 0,283; HbA1c 7,89 % DE 1,88) con respecto al grupo de pacientes sanos (3,5 mm DE 0,52; 0,785 mm/s DE 0,368; HbA1c 6,31 DE 0,59). Los principales hallazgos fundoscópicos localizados en retina fueron neovascularización (78,26 %), exudados (67,39 %) y hemorragias (60,87 %). Se observó asociación entre HbA1c mayor a 7,89 % y velocidad pupilar menor a 0,598 mm/s con la presencia de neovascularización y hemorragias retinales. Conclusiones: se evidenció asociación entre las respuestas pupilares, la HbA1c y los hallazgos retinales en pacientes diabéticos tipo 2.
Variables y parámetros influyentes en los perfiles de ablación del láser de excímeros
Authors: Tomás-Juan Javier
Published: November 2015

El láser de excímeros permite corregir los errores refractivos miópicos, astigmáticos e hipermetrópicos mediante la ablación de la superficie corneal. Para conseguir el mejor tratamiento y la mejor corrección visual postoperatoria es necesario un buen mantenimiento y calibración de todos los parámetros del láser y de los factores ambientales de la sala de quirófano. Después de la cirugía en algunas situaciones se produce un incremento de las aberraciones, las cuales afectan en gran medida a la calidad visual del paciente. En la actualidad nuevos dispositivos basados en la ablación guiada por frente de onda y la ablación topográfica se han introducido con el objetivo de disminuir las aberraciones postoperatorias. En el presente trabajo se realiza un análisis de los principales parámetros del láser de excímeros que influyen en la ablación, como los diferentes perfiles de ablaciones corneales, que muestran cómo se relacionan directamente con la calidad visual posquirúrgica.

 
Glaucoma agudo por cierre angular: manejo de urgencias por el optómetra
Authors: Muñoz Montero Ángela Patricia , Montoya Amézquita Glorith Xiomara
Published: November 2015

Existe una presentación clínica de glaucoma de ángulo cerrado o agudo con sintomatología dolorosa y de curso rápido, con grandes posibilidades de detección y tratamiento oportuno. Este cuadro inicia por afluencia excesiva entre el iris y el cristalino que impide el flujo de humor acuoso de la cámara posterior a la anterior con el progreso de bloqueo pupilar relativo, ocluyendo la porción filtrante de la malla trabecular y causando elevación de la presión intraocular (PIO). La urgencia se manifiesta con fuerte dolor ocular y reducción de la agudeza visual, que puede manejarse adecuadamente por el optómetra, con el fin de hacer una remisión oportuna al servicio de oftalmología, ya que las consecuencias de la progresión de la enfermedad o de un diagnóstico incorrecto son irreversibles en términos de pérdida de agudeza visual y campo visual, lo que afecta de modo considerable la calidad de vida de los individuos. Objetivo: presentar los parámetros clínicos para identificar, diagnosticar y manejar la urgencia de cierre angular y remitir oportunamente para el tratamiento oftalmológico. Metodología: revisión de literatura a través de una búsqueda bibliográfica. Resultados: se presenta una guía de manejo para el optómetra, donde se muestra el tratamiento primario de la urgencia ocular por glaucoma de ángulo cerrado.
Comparación de la prueba de tamizaje PlusoptiX con la retinoscopia bajo cicloplejia para la detección de defectos refractivos significativos
Authors: Frazier Marcela , Hill Michael
Published: November 2015

Objetivo: comparar la prueba de tamizaje PlusoptiX con la retinoscopia bajo cicloplejia para la detección de defectos refractivos significativos en menores entre los 4 y 18 años. Métodos: el PlusoptiX se usó en una muestra de 220 menores en varias escuelas en Cartagena, donde se comparan los resultados con los de la retinoscopia bajo cicloplejia. Para el análisis estadístico se aplicó la prueba de diferencias para muestras relacionadas en el software SAS 9,4 con ≈ 0,05, a fin de comparar los valores de la mediana (Wilcoxon) y la distribución cumulativa (Kolgomorov-Smirnov) entre las dos técnicas. Se generaron los valores de concordancia nominal entre los rangos que clínicamente se consideraron importantes de ±0,50 y ±1,00 D. Asimismo, se calculó la sensibilidad y especificidad del instrumento PlusoptiX para detectar defectos refractivos significativos. Resultados: se detectó hipermetropía > +3,50 D en 4,5 %, miopía > –3,00 en 0,04 %, astigmatismo > –1,50 D en 15,9 %, anisometropía > 1,50 D en 3,2 %. La concordancia entre el PlusoptiX y la retinoscopia fue de ±0,50 en 34,7-41 % en los valores de esfera y de ±0,50 en 57,7-61,3 % en los valores de cilindro. La mejor sensibilidad fue de 72 %, con una especificidad de 61 %. Conclusiones: el PlusoptiX produjo resultados diferentes de la retinoscopia bajo cicloplejia. El instrumento PlusoptiX puede ser usado para facilitar tamizajes; sin embargo, debe prestarse atención a su baja sensibilidad y especificidad.
Informe de la salud visual y ocular de los países que conforman la Red Epidemiológica Iberoamericana para la Salud Visual y Ocular (REISVO), 2009 y 2010
Authors: Brusi Laura , Argüello Lady , Alberdi Agustín , Bergamini Javier , Toledo Florencia , Mayorga-Corredor Myriam Teresa , Rodríguez Martha Fabiola , Figueroa Luisa Fernanda , López Yolanda , Medrano Sandra , Díaz Augusto , Chavarría Adrián , Chacón Voloshena Raúl , Alfonso César , Rodríguez Selma , Chacón Juan Pablo , Chacón Carlos , Mojica Alfonso , Gené Sampedro Andrés , Morales Hernández Mari Carmen , Bueno Gimeno Inmaculada , España Gregori Enrique , Sánchez Ramos Celia , Velázquez Guerrero Rubén , Sandoval Olga , Muñoz Juan Manuel
Published: November 2015

Según las estimaciones más recientes de la Organización Mundial de la Salud (OMS), cerca de 314 millones de personas en el mundo presentan discapacidad visual, debido a enfermedades oculares o a errores de refracción no corregidos. De estas personas, 45 millones son ciegos y el 90 % vive en países con ingresos bajos. Las principales causas de ceguera son catarata (39 %), errores refractivos no corregidos (18 %), glaucoma (10 %), degeneración macular asociada a la edad (7 %), opacidad corneal (4 %), retinopatía diabética (4 %), tracoma (3 %), afecciones oculares infantiles (3 %) y oncocercosis (0,7 %).
Evaluación del lag de acomodación con la retinoscopía de Nott entre los 5 y los 19 años de edad
Authors: León Álvarez Alejandro , Zapata Giraldo Paulo César
Published: November 2015

Objective To determine the normal values of lag of accommodation in a population between the ages of 5 and 19 from public schools in Pereira. Materials and methods Lag of accommodation in 505 individuals (392 individuals selected) from public schools in Pereira was assessed using the Nott retinoscopy. Results The average lag of the entire group was 0.51 D (percentile 5 = 0.19 D percentile 95 = 0.89 D) there was no divergence based on gender, but there was divergence between the age groups of 5-9 and 15-19 (Kruskal-Wallis = 0.0214). Conclusions Lag of accommodation in this group was lower than reported in other studies. Therefore, we recommend using the results found in the assessed ages as benchmarks in our environment.
Avances en la construcción de un sistema de información en salud en Colombia
Authors: Orduña Ortegón Yeimi Pilar
Published: November 2015

Introducción: los sistemas de información buscan facilitar los aspectos logísticos de la atención en salud, permitir que las instituciones de salud funcionen efectivamente, ayudar a los prestadores de asistencia a actuar con eficacia, mejorar el acceso a los datos administrativos, clínicos y epidemiólogos tanto individuales como colectivos, y simplificar el acceso a las referencias biomédicas. Objetivo: identificar los avances en la construcción de un sistema de información en el ámbito nacional. Metodología: se realizó un estudio exploratorio de tipo descriptivo observacional en el cual son utilizados métodos cualitativos, con el fin de recopilar datos existentes para la identificación y descripción de los sistemas de información en Colombia. Inicialmente, se hizo una revisión de bases de datos como Lilacs, Google Académico y SciELO, durante los últimos veinte años, en los siguientes países: Venezuela, Cuba, Brasil, Colombia, Perú, España, Costa Rica y México. Recomendaciones: para la implementación y puesta en marcha de un sistema de información funcional en el país, se deberán formular políticas generales que faciliten estrategias nacionales, dirigidas a la generación de proyectos, el desarrollo de infraestructuras y la maximización de recursos destinados. Conclusión: los avances tecnológicos permiten mejorar y dominar la información, lo que significa dominar los procesos y la toma de decisiones.
Cambios en la agudeza visual, la queratometría y refracción en pacientes después de cirugía de pterigion grado I y grado II
Authors: Ríos Figueroa María Fernanda
Published: November 2015

El pterigion es un crecimiento de tejido fibrovascular conjuntival que se extiende sobre la córnea, puede sobrepasar el área pupilar, interferir la visión y generar tracciones que podrían causar cambios refractivos. Objetivo: determinar los cambios en la agudeza visual, en la queratometía y en el estado refractivo después de la cirugía de pterigion leve y moderado. Materiales y métodos: estudio observacional descriptivo en el que se evaluaron 52 ojos de 46 pacientes que acudieron al hospital San Antonio de Chía con diagnóstico de pterigion grado I o grado II. A cada paciente se le midió agudeza visual, queratometría y refracción antes y después de un mes de la cirugía del pterigion. Se aplicaron las pruebas ji2 (X2), t pareada y Wilcoxon. Resultados: en el grupo con pterigion grado I no se observaron diferencias estadísticamente ni clínicamente significativas en la agudeza visual (p = 0,14), ni en la queratometría (p = 0,69) ni en la refracción (p = 0,33) después de la cirugía. En el grupo con pterigion grado ii se observaron diferencias estadísticamente significativas en la queratometría (p = 0,0042), pero no en la agudeza visual (p = 0,88) o en la refracción (p = 0,52); sin embargo, estos pacientes tuvieron tendencia a disminuir su visión y a miopizarse. Conclusiones: no se evidenciaron cambios significativos luego de la cirugía en el grupo de pacientes con pterigios grado I, mientras que en el de pterigion grado II sí se evidenciaron cambios estadísticamente significativos en la queratometría y cambios clínicamente relevantes en la agudeza visual sin corrección.
Hydrate Anti-Agglomerants for Sour Gases with Corrosion Inhibitor Properties
Authors: Mukherjee D. , Fowles R. , Treybig D. S. , Murugan P.
Published: November 2015

Hydrates can agglomerate and block pipelines causing blowouts and serious harm to personnel in addition to stopping production. They may contain as much as 30% H2S. Thermodynamic inhibitor (THI) methanol is the default method for addressing hydrate problems. Methanol can dissolve corrosion inhibitors (CIs), leading to increased corrosion rates. Alternatives are kinetic hydrate inhibitors (KHIs) but their performances are negatively affected by CIs, and they may not be suitable for sour conditions. The objective of this work was to develop anti-agglomerates (AAs) alternatives to THI and KHI that simultaneously provide corrosion protection while functioning in a sour environment.

Gas hydrate analysis was done in a gas hydrate autoclave up to 1915 psi (13,203 KPa) using 1-8% H2S, 3% CO2 and remaining CH4 at 4 °C. AAs were tested with and without alkylpyridine CI (CI-1) and torque values were used to measure performance. Selected AAs were tested to ascertain their effect on corrosion in low, medium and high salinity brine. Also corrosion studies were conducted in a benchtop autoclave at different operating parameters; temperature (22, 30, 50, 80 and 120 °C), H2S composition (4%, 20% and 35%), CO2 (3%, 4% and 10%) at total pressure of 350 psi (2413.2 kPa) and 1000 psi (6894.8 KPa). Testing was performed on 1018 carbon steel using a modified ASTM G170 method.

In hydrates testing, ≤ 2% quaternary compounds AC-1 and AC-2 (with CI-1) gave lower torque values (< 2.8 Ncm) compared to the blank (12.0 Ncm) and control (CI-1 only) (9.2 Ncm). Corrosion rate in 4% H2S, 3% CO2 at 22 °C was 24 and 12.41 mpy for the blank, while AAs (with CI-1) caused decrease in corrosion rate to 0.75 and 0.9 mpy for low and medium salinity brine respectively in the water phase.

For severe conditions at 120 °C, 20% H2S and 10% CO2, the blank gave a corrosion rate of 37.83 mpy with pitting whereas 200 ppm of V-53 (33% AC-1) and V-9 (33% AC-2) provided corrosion rates of 2.26 mpy and 2.62 mpy without pitting in the brine phase. In 35% H2S and 4% CO2, the blank showed a corrosion rate of 45.78 mpy with pitting whereas 200 ppm of CI-1 and specially formulated quaternary compounds (CI-2 and CI-3) provided corrosion rates of 2.57, 2.19 and 8.87 mpy without pitting in the synthetic brine phase.

The compounds presented in this paper were able to control hydrate agglomeration up to 100 % water cut, remained active in the presence of corrosion inhibitor and demonstrated corrosion protection in sour conditions.
Applying Rock Physics Analysis to De-Risk Exploration Prospects in Mannar Basin, Sri Lanka
Authors: Malkani Anil , Routray Prabir , Majumdar Pinaki , Kumar Prem , Ghosh Biswanath , Chacko Soman
Published: November 2015

The study area, block SL-2007-01-001, operated by Cairn India Ltd., is located in the Mannar basin of NW offshore Sri Lankan (blue polygone in Figure-1) and contains a sedimentary section exceeding 7km, the age of which ranges from Jurassic to Recent. The large number of oil and gas discoveries in the contiguous Cauvery Basin, both in Cretaceous and Tertiary sections, makes this frontier basin an attractive candidate for exploration. In 2010 Cairn Lanka acquired 1753 sq km of 3D seismic data in order to assess the exploration potential of this deep water block. This paper focuses on the role that rock physics analysis played in the assessment, risking, and ranking of the key leads identified in the basin. Of the numerous leads identified, three were high-graded in large part due to their DHI characteristics, resulting in the Dorado and Barracuda gas discoveries (Well-A & Well-C in Figure-1, respectively), the first hydrocarbons to be discovered in the Mannar Basin. The third well, Well-B, was a dry hole.

De-risking of exploration prospects was based on quantitative seismic interpretation supported by rock physics analysis. This paper emphasizes how rock physics can add value in an exploration project to influence business decisions by reducing subsurface uncertainties. The nearest well, CY-DWN-2, that provided data for depth trends and rock physics analysis is located approximately fifty kilometers south west of the study area. Although this was a dry hole, it provided significant information on the sedimentary sequence, rock properties, and their associated seismic responses. Various "what if" scenarios were created to understand associated seismic responses. The analsyis explained the dry hole at CY-DWN-2 and highgraded the prospectivity of the Dorado lead. The latter was subsequently drilled, leading to the Dorado discovery.
Natural Productivity Analysis and Well Stimulation Strategy Optimization for the Naturally Fractured Keshen Reservoir
Authors: Zhang Fuxiang , Huang Yongjie , Yang Xiangtong , Qiu Kaibin , Yuan Xuefang , Luo Fang , Zhang Yang , Zheng Zijun
Published: November 2015

The Keshen reservoir is a naturally fractured, deep, tight gas sandstone reservoir under high-tectonic stress. Stimulation is critical to the successful development of the Keshen gas field. However, due to the heterogeneity of the natural fracture system in the reservoir, there is large variation in natural productivity from production wells, which mandates different types of stimulation operations from simple acidizing to massive hydraulic fracturing. Hence, to improve the efficiency of reservoir stimulation and overall performance of the reservoir development, reliably evaluating the natural productivity from production wells and optimizing well stimulation strategy (by selecting appropriate stimulation operations) are required.

To this end, single well production history matches were conducted to calculate the natural fracture (NF) permeabilities for 12 acidizing wells with known matrix petrophysical properties. It was found out that the NF permeability is clearly correlated to the intersection angle ((, angle between maximum horizontal stress and NF strike) and Young's modulus (E), based on detailed natural fracture interpretation and geomechanics analysis. By using a correlation with the intersection angle and Young's modulus, the NF permeabilities for seven hydraulic fractured wells with large size treatment were obtained and the natural productivity for each well was predicted. By comparing predicted natural productivity with actual post-stimulation productivity, the productivity enhancement by hydraulic fracturing treatment was determined. The comparison showed that the productivity improvements by hydraulic fracturing treatment were very limited and unnecessary for the wells with high natural productivity, while improvements were substantial for others. Subsequently, the well stimulation selection criterion was formulated, which classified wells into three categories based on the natural productivity, and specified stimulation method was recommended for each well category, respectively.

This paper shows an example: the natural productivity of a newly drilled well was predicted, and massive hydraulic fracturing was selected based on the stimulation treatment selected criterion. The well was successfully stimulated with absolute open flow (AOF) of 3.6 MMm3/d, which doubled the natural productivity.

The workflow used to estimate the natural productivity of the tectonically active Keshen reservoir and to establish the well stimulation selection criterion, and their application and validation, which are rarely published previously, are presented in this paper.
Failure Analysis of Carbon Steel Sub Sea Water Injection Pipelines and Their Protection for Good IOR
Authors: Bhardwaj Anil , Kumar Bipin , Prasad Sangeeta R. , Srivastava S. K.
Published: November 2015

Water injection is one of the methods for maximizing oil production and improving oil recovery by way of maintaining reservoir pressure. It entails injection of water in sufficient quantities with acceptable quality into the appropriate zones of the reservoir in a cost efficient manner. Treated water is transmitted from treatment to well generally through carbon steel pipelines; as there are flexible pipelines, internally coated pipelines being used for water injection also. And this paper is solely for carbon steel pipelines. The corrosion of these water injection pipelines is a major issue for the Oil & Gas industry with a view to preserve the reservoir permeability and integrity of the pipelines.

A few case studies pertaining to failure of API 5L carbon steel subsea water injection pipelines with their root cause analysis are presented in this paper. In order to identify the cause and mechanism of failure, detailed laboratory and analytical investigations were carried out with a view to characterize the material property as well as to evaluate the corrosivity of operating environment. Studies like visual inspection, non destructive testing, corrosion product analysis, elemental compositional analysis, metallographic investigations, inclusion content test, hardness testing, tensile strength studies, impact test, stereomicrscopy, scanning electron microscopic (SEM) coupled with energy dispersive spectroscopy (EDS) studies, have been carried out. Process parameters, operating & maintenance practices, chemical treatment program with quality parameters etc. have also been critically examined.

Pipeline material was found to conform to the specification API 5L. The analysis showed that the most probable cause of the failure of the pipeline was under-deposit/grooving corrosion, which started with oxygen and Microbiologically Influenced Corrosion due to Sulphate Reducing Bacteria and was subsequently supported by very low flow velocities in those pipelines. The stagnant water and the formation of thick deposit consisting of corrosion product, sludge or suspended solids and biomass as a result of proliferation of bacterial colonies were the conditions for attack to set off. Galvanic corrosion further accelerated the metal loss process as grooving/channeling resulting into failure at 6 O'clock position. Presence of large number of inclusions in some of pipeline materials was an additional cause of accelerated corrosion process.

On the basis of root cause failure analysis, the major integrity threats to the water injection pipelines resulting from process control were identified. Accordingly, preventive and remedial measures essential for preserving integrity of water injection pipelines have been suggested. Implementation of good operating and maintenance practices, robust quality control measures, continuous monitoring of corrosion trends, prompt corrective actions are the key requisites to abate failures due corrosion.
Novel Use of Spent Amine Solution of Gas Sweetening Plant as H2S Scavenger, Corrosion Inhibitor & Biocide
Authors: Shukla A. K. , Chauhan P. S. , Sahu S. K.
Published: November 2015

Gas Sweetening is the most important operation of any Natural Gas Processing Plant. At ONGC, Uran Plant, gas received from offshore is combined with the crude stabilization off gas (CSU off gas) and condensate fractionating off gas and then passed through Gas Sweetening Units (GSU) to remove CO2 and H2S from the gas before further processing in LPG and EPRU for extraction of value added products.

GSU plant was originally designed for and operated with gas sweetening solvent system consisting of DIPA (Di-Isopropanol Amine) & Sulfolane. Contamination of solvent by amine degradation products and comingled composition of solvent system became a bottleneck for increasing gas processing capacity and to enhance plant capacity, comingled solvent system was replaced with a third generation solvent system consisting of MDEA, Sulfolane & Piperazine.

After change-over, approximately 500 MT of comingled amine solution having a mixture of DIPA, MDEA, Sulfolane, Piperazine and Oxazolidone (an amine degradation product), was available as a hazardous waste. Owing to the complexity of the mixture having five different chemicals, reclaiming of useful solvent from the comingled solution was ruled out and the only option left was its disposal by incineration.

Keeping in view the large quantity of spent solution & huge cost of disposal, study was undertaken to explore possibility of use of spent solution for some other in house applications.

Extensive lab studies carried out to evaluate anti-corrosive, anti-microbial and H2S scavenging properties of spent solution & found that amine solution has adequate H2S Scavenging & corrosion inhibition efficiency at 400–500 ppm and bactericidal efficiency at 30 ppm of dosage.

The subsequent field trial at 400–500 ppm of doses in one of the Oil trunk line having three phase flow (oil, associated gas and water) for quite a period has shown substantial reduction of H2S content in the off gas.
Investigation of Thermal Finger Print in Accelerating Rate Calorimetry for Air-Injection Enhanced Oil Recovery Processes.
Authors: Bhattacharya S. , Mallory D. G. , Moore R. G. , Ursenbach M. G. , Mehta S. A. , Belgrave J. D.
Published: November 2015

The Accelerating Rate Calorimeter (ARC) is unique for its exceptional adiabacity, its sensitivity and its sample universality. Accelerating Rate Calorimetry is used as one of the screening tests employed to determine the suitability for Air-Injection enhanced oil recovery. These tests indicate oil reactivity and exothermicity over a broad range of temperatures: low temperature range, negative temperature gradient region and high temperature range. An experimental and simulation study was carried out to expand understanding and interpretation of the data derived from high pressure closed ARC tests.

Athabasca bitumen was used for the experimental study in a closed ARC at 13.8 MPag (2000 psig) to identify the temperature ranges over which the oil reacts with oxygen in the injected air. Experimental analysis for self-heat rate from accelerating rate calorimetry data and mass loss rates from differential thermo-gravimetric analysis shows the influence of mass transfer of oxygen within bitumen in the low and high temperature range. A numerical model was developed to predict the solubility, diffusivity and reactions of oxygen with bitumen. The model incorporates solubility of oxygen using partition/equilibrium coefficient (K-value) which transfers throughout oil layer by diffusion. This model considers both low and high temperature oxidation and thermal cracking reactions.

The results show by integrating mass transfer with the traditional kinetic model it is possible to predict the negative temperature gradient region which will therefore predict the onset in the exotherm of Self- Heat-Rate. The results also show that the swellability of bitumen due to solubility of air and product gases creates a concentration gradient of oxygen inside the bitumen. Viscosity and temperature dependence of the mass transfer of oxygen is linear, as time passes and chemical reaction becomes more important with increasing temperature, the relationship deviates from linearity. With an increase in temperature, the influence of chemical interaction on the oxygen distribution becomes greater, and this results in a shorter initial stage of mass transfer of oxygen within the bitumen film at low temperatures. This implicates that the ARC can be an effective tool for understanding the role of mass transfer on the oxidation characteristic for predicting low, negative temperature gradient and high temperature regions.
Innovative Concepts in Wire Line Focussed Sampling in Open Hole: Case Studies From an Oil Field Off the West Coast of India
Authors: Garg Vivek , Medhekar Sharad , Pratap Mahendra
Published: November 2015

The paper deals with focused sampling in two reservoirs of a carbonate field off the west coast of India. It was imperative to characterize the fluid through down hole optical spectroscopy prior to trapping the PVT samples. The fluid type in both the reservoirs was known. In one case gaseous phase was predominant for a long time even though the reservoir is oil bearing. The near well bore permeability was very low of the order of 1 md/cp due to drilling induced damage. Because of low permeability high draw down was applied resulting in low flow line pressure which was below the bubble point pressure of the reservoir and therefore the gas fraction was mainly being pulled into the flow line. The well was drilled with oil based mud and fluorescence channel was indicating high fluorescence. The possibility of the fluorescence due to oil based mud was ruled out after the flow line pressure was considerably reduced resulting in no fluorescence. This indicated that fluorescence seen earlier was due to liquid fraction along with gas, an effect similar to that seen with an atomizer. More over the fluorescence values were high which further strengthened the assumption that oil droplets were in the flowing media. With meticulous analysis of the down hole optical spectra from the fluid in the tool flow line and subsequent pressure adjustments oil started to flow after pumping for about six hours and oil PVT sample was trapped

The other case is related to trapping an uncontaminated gas sample. The sample purity was essential as the same was to be matched with leaking gas at the surface and thereafter to track down the gas reservoir that was contributing to the leakage. The reservoir from which this sample was being trapped is a depleted reservoir and no PVT sample was available for this reservoir. Sample studies for other gas reservoirs in the field were available. Due to pressure depletion there was considerable mud loss and after eleven hours of pumping and simultaneous analysis of the down hole optical spectra, the gas sample was trapped with contamination less than 9%
Petrophysical Rock Type Based Saturation Model To Reduce The Uncertainty In A Deepwater Low Resistivity Clastic Gas Reservoir.
Authors: Dhar Samir Kumar , Kumar Alok , Nandipati Viswanath , Bhattacharya Aumeya
Published: November 2015

Initial water saturation (Swi) in a gas reservoir is an important parameter for inplace resource (GIIP) and ultimate reserve estimation, which in turn impacts the economic decision. Swi estimation in a low resistivity deep-water clastic reservoir is more challenging because limited well data in less number of (costly) appraisal wells in a large area. Conventionally, Swi is computed from open hole logs and validated with core plug data to reduce the range of uncertainty in estimation. But this standard methodology fails when resistivity log derived Swi shows a variance with the saturation measured from the core plugs and increases the range of uncertainty. Sometimes, log derived Swi shows high water saturation in the gas bearing interval due to low anomalous resistivity which is beyond correction.

Saturation height modelling is an age old solution for this sort of problem and the same was attempted first to estimate Swi. But single saturation height function does not represent all the rock types of the reservoir and replicate log derived Swe curve. Petrophysical rock typing was carried out using porosity and permeability from the core plug in the first step and then by using the concept of flow zone index (FZI) and rock quality index (RQI). FZI-RQI based rock types were able to characterize the reservoir in a better way in 3D-Geologic model and also able to separate the different behaviours of Capillary pressure curves.

Two saturation height functions were made after characterizing good rock and poor rock type, which were tested in the dynamic model for flow simulation and recovery factor estimation successfully. This innovative concept of FZI-RQI based petrophysical rock typing (PRT) and saturation height modelling finally added value to recreate the Swi curve against the low resistivity pay interval and to reduce the range of uncertainty in Sw estimation.
Technology Challenges in Deep Water Subsea Well Intervention - A focus on Equipment Design Advancements
Authors: Suresh D. , Manikandan S. , Rajashree S.
Published: November 2015

Due to the current challenging environment in Oil and Gas industry, cost effective hydrocarbon recovery from Subsea Wells is mandating innovative methods in equipment design construction and qualification. Different types of intervention systems are required based on the issue being addressed, the intervention technique being used, depth of water, geographical locations, vessel types and pressure/temperature conditions. The industry is increasingly utilizing well access solutions such as Open water riser system and Light Well Intervention System not only for equipment installation, but also to improve efficiency of operations, to facilitate life-of-field hydrocarbon production enhancement and restorative intervention techniques. Suppliers and Operators of subsea intervention system need to rise to the challenge of meeting increasingly stringent industry standards and customer requirements. This necessitates but is not limited to the importance of utilizing effective seal design, robust barrier design, advanced materials and safety rated control systems with rigorous design and qualification test validation.

The more demanding requirements of the move to deeper and deeper water and higher pressures and temperatures have led to enormous challenges both at the component and system level. This is driving the incorporation of the latest technology on both metallic and non-metallic seals for high temperature application. This is particularly relevant in valve qualification for field producing hydrocarbons with high levels of sand. Size and weight reduction design strategies for equipment destined to be used in deep water allows for effective selection of existing rigs and vessels of opportunity. Advanced design validation including 3D printing of components has resulted in more accurate and predictable results for Component interactions, Strength Integrity and Fatigue Capacity. Thermal analysis used for prediction has allowed for prevention of hydrate formation which has proved essential to validation of the intervention system performance.

To qualify subsea components in deep water, technology enhancements, the latest manufacturing techniques and supply chain approaches, welding techniques etc. are critical to success. Deepwater System challenges include communicating and controlling the well and Xmas tree remotely through an Installation and Workover Control System. This can be resolved with design of optimized safety-rated electro-hydraulic system along with a robust sensor system which provides a safe and reliable method for hydrocarbon containment during critical well intervention operations.

This paper will depict some of the latest design techniques required to deliver advanced equipment to the Intervention market. The areas addressed will be: Identification of the technology challenges, providing right solution, usage of design tools for equipment design advancement and managing risk.
An Innovative Approach for Curing Severe Loss Control Problems in Mumbai Offshore while Drilling - A case study
Authors: Rastogi R. , Lal Kishori , Singhal R. , Sinha M. P. , Pratap K. Krishna
Published: November 2015

This paper relates severe lost circulation problems often encountered when the well is drilled overbalanced through high-permeability, fractured, or easily fractured formations. As numbers of LCM pills, neat cement plugs were placed in damaging and non-damaging reservoirs, resultant failed to provide an adequate solution.

Recently, severe mud loss problems were encountered during drilling in Mumbai Region from depleted reservoirs, unconsolidated, highly permeable, fractured and fragile limestone formations, both from nonproducing and producing reservoirs (L-III, L-II, L-I, H1A, H3B, etc.). The losses range from 100 BPH to total loss. Attempts are made to stop the losses with the placement of advanced lost circulation treatments. To mitigate these types of losses, an innovative technique developed with a temperature-activated Rapid Setting Fluid (RSF) Pill from indigenously available chemicals and used as an alternative to LCM / cement plugs for severe loss control problems in Mumbai Offshore. The RSF system has proven successful for curing severe dynamic and static losses by pumping treatments through the drill string bottom hole assembly (BHA) (no trip out required) and taking advantage of its highly controllable fast setting properties.

The RSF pill is a stoichiometric mixture of magnesium compound, forming hard and a series of high mol. wt. magnesium inorganic poly-hydrates, displaying characteristics of conventional cement slurry in pumpability, but very different chemically. As the RSF Pill enters the lost zone, it sets rapidly (a rapid transition from liquid to solid) and builds sufficient compressive strength within 5-6 hrs. The reaction causing solidification is wholly a function of time and temperature and unaffected by hydrostatic pressure. The pill is non-damaging as it is non-invasive, sets at the lost zone mouth and 90-100 % soluble in 15 % Hydrochloric acid. The pill can be successfully used up to 140 °C BHST.

The field trial has been carried out successfully in two wells of Mumbai Offshore: N_12#3Z (Mumbai High L-III reservoir) in partial loss conditions and HG#6H (Miocene Bandra Limestone formation) with total losses. It has also established that the new Loss Control Solution, RSF Pill can be placed successfully in all types of lost zones (like L-III, L-II, L-I, H1A, H3B) to mitigate the mud losses.

The paper also details the specific chemical and mechanical characteristics and field performance of the RSF pill. It concludes that the combination of unique fluid properties and best practices in fluid placement procedures plays a vital role in the successful implementation and development in the treatment of loss circulation in limestone formations. This technique is unique, easy, very effective and provides cost benefits.
Novel Approach for Evaluation of Simultaneous Water and Gas Injection Pilot Project in a Western Offshore Field, India
Authors: Agrawal G. , Verma V. , Gupta S. , Singh R. , Pandey A. , Kumar A. , Chadha H. K. , Agarwal A. K. , Chaudhary S. , Saxena R.
Published: November 2015

A field in western offshore India proved to be a major hydrocarbon-bearing structure, but wells in the field gradually declined in reservoir pressure and production when they were self-flowing. To improve recovery, water injection was performed, which almost doubled the field production. However, water cut eventually increased drastically, thereby reducing oil production. To curtail increasing water cut and improve oil recovery, a tertiary recovery method was sought.

After closely studying various recovery methods, simultaneous water and gas (SWAG) injection was proposed in which a predefined mixture of produced gas and water was injected to improve oil sweep and reduce residual oil saturation by oil swelling, ultimately increasing oil recovery. However, to practically observe field suitability and feasibility of the SWAG method, a pilot project that included four injectors and one producer was launched.

Efficiency of SWAG injection increases as a result of the consistent gas and water fine bubble flow regime developed in the wellbore, depending on casing size, tubing-shoe distance from perforation, and deviation. To evaluate this efficiency, production logging with optical probes to detect gas holdup was proposed in three injectors with different casing sizes and deviations. The existing wellbore flow regime from results of production logging were observed and compared with respect to favorable flow behavior to understand the effect of these factors on SWAG injection effectiveness. We found and suggested the deviation and casing-size configuration that was deemed optimal.

This was the first time production logging was used in India to evaluate the SWAG injection wellbore flow regime, and the method proved effective. The results are to be used for full-field SWAG injection implementation to improve overall field recovery.
Microseismic Monitoring Reveals Hydraulic Fracture Development in Clustered Horizontal Well Completed in High-Temperature Tight Gas Reservoir, Sultanate of Oman
Authors: Nadezhdin Sergey , El Gihani Mahmoud , Al Alqam Amin , Briner Andreas , Harrasi Othman , El-Taha Yasin , Batmaz Taner
Published: November 2015

Since 2012, Petroleum Development Oman (PDO) has attempted several hydraulic fracture monitoring (HFM) evaluations in deep, high-temperature, tight gas wells in the Amin Formation of the Fahud salt basin. The first successful job was executed in late 2014 for treatments placed in a horizontal wellbore. Following this job, in-depth HFM analyses were conducted that led to recommendations on well completion and fracturing treatment improvements. The purpose of the HFM trial in this challenging tight gas Amin reservoir of the Fahud salt basin was evaluating hydraulic fracture geometries, fracture propagation, and orientation. The horizontal well had been purposely drilled in the vicinity of an earlier completed vertical well to enable execution of the HFM job. Microseismic monitoring provided a direct measurement of the rock-failure coordinates and helped in gauging the effectiveness of the hydraulic fracture treatment placed in two clusters of the same fracturing stage. A large set of raw data representing 52,000 triggers was recorded and processed through different filtering methods including processing noise generated from gas flow in the monitoring well behind the casing. The evaluation suggested that the fractures have grown upward. It also revealed fracture length dimensions and stimulated reservoir volume along with the previously unmeasured fracture azimuthal orientation. The HFM job provided insight on how the hydraulic fractures propagate when two perforation clusters are placed in different stress zones, and if it is possible to place comparable hydraulic fractures in both. HFM results were coupled with geomechanics work and post-fracturing production logging to develop recommendations for future well completion improvements.
Arresting Decline in the Ravva Field: Success Story of Phase-5 Drilling Campaign
Authors: Sarkar S. , Kumar S. , Reddy K. , Shankar V. , Mishra U. S. , Sabharwal V.
Published: November 2015

Cairn India operated Ravva Field is located offshore Krishna-Godavari (KG) Basin on the east coast of India. The field was discovered in 1987 and was brought into production in 1993 from the Middle Miocene sandstones. Oil production rate reached its plateau of ~50,000 bopd by 1999. The field produced at the plateau rate for ~ 9 years before starting to decline by the end of 2007.

Two infill drilling campaigns were planned and executed in 2007 and 2011 to arrest the production decline and add incremental reserves to the field. New infill wells increased production for a short while but failed to arrest the prevailing declining trend. By the end of 2013, Ravva oil production dropped to ~21,000 bopd and was declining by 35–40% per year. Arresting the production decline by finding additional reserves in a mature waterflooded field which had already achieved ~49% oil recovery was a challenge with significant risks. Planning for additional infill drilling targeting areas of undrained oil required an integrated approach with adoption of advanced technologies to minimize risks.

A 4-D monitor seismic survey was acquired in 2010 over the Ravva field and co-processed with a vintage baseline survey to identify areas of undrained oil. Separate processing of the 2010 high density 3-D survey provided improved seismic imaging of the subsurface architecture. A high resolution 3-D model was created by using sequence stratigraphic concepts, fault seal analysis studies, detailed property modeling through integration of seismic attributes, log and core data. An integrated subsurface study was initiated in 2011 to identify infill well opportunities in the field. A full cycle of integrated reservoir modeling from seismic to simulation was carried out using advanced technologies and workflows.

The integrated study resulted in the identification of several infill opportunities as well as near field exploration and appraisal targets. The Ravva Phase-5 drilling campaign executed in 2014-15 comprising 8 infill, 1 water injector, and 2 exploration/appraisal wells was the most extensive infill campaign in the field's history. Well results from the drilling campaign have been very encouraging. The ten producers drilled in the campaign together added ~18,000 bopd to the field production and they are estimated to improve the field oil recovery by ~3%. By March 2015, when all new wells were brought online, Ravva field production had once again reached 28,000 bopd. The success in near field exploration and appraisal has extended the producing field boundary and has identified upsides that could support future drilling campaigns.

The Ravva Phase-5 drilling campaign has showcased the first successful application of a 4-D OBC seismic project in India. New technologies such as 4-D seismic combined with integrated subsurface reservoir modeling can demonstrably arrest production decline in comparable mature oil fields and drive recovery factors closer to the technical limit.
A convergence theorem of multi-step iterative scheme for nonlinear maps
Authors: Mogbademu Adesanmi
Published: November 2015

Let K be a nonempty closed convex subset of a real Banach space X,T:K ? K
a nearly uniformly L-Lipschitzian (with sequence {rn}) asymptotically
generalized ?-hemicontractive mapping (with sequence kn ? [1,?), lim n?? kn =
1) such that F(T) = {p?K:Tp=p}. Let {?n}n?0, {?kn}n?0 be real
sequences in [0,1] satisfying the conditions: (i) ?n?0 ?n = 1 (ii) limn??
?n, ?kn = 0, k = 1, 2,..., p?1. For arbitrary x0 ? K, let {xn}n?0 be a
multi-step sequence iteratively defined by xn+1=(1??n)xn + ?nTny1n, n?0,
ykn = (1 ? ?kn )xn + ?kn Tnyk+1n, k = 1,2,..., p?2 (0.1), yp?1n=(1? ?p?1n)xn
+ ?p?1n Tnxn, n ? 0, p ? 2. Then, {xn}n?0 converges strongly to p ? F(T).
The result proved in this note significantly improve the results of Kim et al. [2].
Craterlike structures on the cut surface after oxygen-assisted laser cutting of steel
Authors: Orishich Anatoly M. , Shulyatyev Victor B. , Filon Alexander E.
Published: November 2015

A new type of defects on the laser cut surface after oxygen-assisted laser cutting of low-carbon steel is reported. The defects look like craters or hollows. The craters are predominantly observed in the bottom part of the cut. At the sheet thickness of 16 mm, the craters have a characteristic diameter and depth of about 20 μm. The craters are presumably formed by the melt drops that are separated by the gas flow and fall onto the liquid melt film on the side wall near the cut front.
Effect of Sugar Content on Acetaldehyde Yield in Cigarette Smoke
Authors: Cahours X , Verron T , Purkis S
Published: November 2015

The relationship between cigarette blend sugar and acetaldehyde formed in its smoke is a matter of current regulatory interest. This paper provides a re-analysis of data from 83 European commercial cigarettes studied in the 1970s and more modern data on sugar levels and acetaldehyde yields from a series of 97 European commercial cigarettes containing both inherent sugar and in other cases inherent and added sugar. It also provides data from 65 experimental cigarette products made from single curing grades of tobacco, having a wide range of inherent sugar levels but no added sugar.

This study has shown that there is no relationship between acetaldehyde yields and blend sugar content even if a multivariate analysis is carried out taking into account Nicotine Free Dry Particulate Matter (NFDPM) as a co-factor. Such analyses should take into consideration each of the known contributory factors in order to avoid misleading conclusions.

No distinction was found between the mainstream acetaldehyde yields from dark air-cured, flue-cured or US blended style cigarettes irrespective of their sugar content after taking account of differences in NFDPM yields. Similarly, no distinction was found between mainstream acetaldehyde yields of cigarettes made from single grades of either flue-cured, sun-cured or air-cured tobaccos with no sugar added.

This work supports the conclusion that structural material in the tobacco plant is the main source of acetaldehyde in mainstream smoke after combustion during cigarette smoking.