Estimation of field production profiles in case of asphaltene deposition

In this work, we aimed to predict possible field production scenarios in case of asphaltene deposition based on field data as well as recommend remediation and stimulation measures to mitigate the risks of asphaltene deposition in the reservoir. We considered the influence of asphaltene formation in the near-wellbore of producers on the production data without reservoir pressure maintenance system in one of the oil fields. The asphaltene envelope in the reservoir oil was obtained, and the operating conditions of the field were evaluated under the possibility of asphaltene deposition. According to the results of dynamic modeling, the pressure map was plotted and the low-pressure areas in the near-wellbore were shown, which contributes to the aggravation of the problem associated with the asphaltene envelope. Based on the geometrical features of the low-pressure area, the dependence of the permeability reduction in the near-wellbore of the production well on the operating time was obtained using the asphaltene deposition model proposed by Wang and Civan. Based on the Buckley-Leverett theory, the field production profiles were calculated with and without asphaltene deposition. A decrease in the oil rate and consequently, the decrease in cumulative oil production in the field is expected due to the damage formation by solids. Maintenance of the production level will be facilitated by treating the nearwellbore with aromatic solvents and maintaining the reservoir pressure above the asphaltene onset pressure

Particle-particle particle-mesh method for dipolar interactions:on error estimates and efficiency of schemes with analytical differentiation and mesh interlacing

The interlaced and non-interlaced versions of the dipolar particle-particle particle-mesh (P3M) method implemented using the analytic differentiation scheme (AD-P3M) are presented together with their respective error estimates for the calculation of the forces, torques, and energies. Expressions for the optimized lattice Green functions, and for the Madelung self-forces, self-torques and self-energies are given. The applicability of the theoretical error estimates are thoroughly tested and confirmed in several numerical examples. Our results show that the accuracy of the calculations can be improved substantially when the approximate (mesh computed) Madelung self-interactions are subtracted. Furthermore, we show that the interlaced dipolar AD-P3M method delivers a significantly higher accuracy (which corresponds approximately to using a twice finer mesh) than the conventional method, allowing thereby to reduce the mesh size with respect to the non-interlaced version for a given accuracy. In addition, we present similar expressions for the dipolar ik-differentiation interlaced scheme, and we perform a comparison with the AD interlaced scheme. Rough tests for the relative speed of the dipolar P3M method using ik-differentiation and the interlaced/non-interlaced AD schemes show that when FFT computing time is the bottleneck, usually when working at high precisions, the interlaced AD-scheme can be several times faster than the other two schemes. For calculations with a low accuracy requirement, the interlaced version can perform worse than the ik and the non-interlaced AD schemes.All authors are grateful to the DAAD organization for providing financial support. C.H. thanks the DFG for support through the SimTech center of excellence, the ScaFaCoS collaboration, and the SFB 716, and acknowledges helpful discussions with A. Arnold and M. Pippig.Peer reviewe

Combined identification and prediction algorithms

Рассматривается задача построения математической модели зависимости выходных переменных от входных переменных стохастического объекта с учетом априорных знаний о зависимости. Для решения этой проблемы используются как параметрические, так и непараметрические подходы. В работе предлагаются комбинированные алгоритмы идентификации и прогнозирования стохастических объектов с использованием линейной комбинации непараметрических и параметрических оценок регрессии

Household Food Strategies in Response to Seasonality and Famine

SUMMARY Rural families have a range of strategies with which to cope with seasonal and inter?seasonal fluctuations in food supply. For landed households the most important seasonal strategies include choice of cropping patterns to spread risks involving mixed cropping, cultivation of secondary crops, particularly root crops. Other seasonal coping mechanisms include sale of small assets and livestock, drawing down of stored product and cultivation of supportive social relationships. Off?farm income earning work provides one of the best buffers against seasonal stress. If a bad season stretches into a prolonged drought, or if there is a sudden drop in purchasing power, then these activities are further intensified, but families are forced into divesting resources: selling productive assets, constricting food intake, and migration. If investment in rural areas and food production recognised these strategies the severe impact of famine could be avoided. RESUME Stratégies des Familles pour la Production de Nourriture en Réponse aux Variations Saisonnières et à la Famine Les familles rurales ont toute une série de stratégies qui les aident à faire ux fluctuations saisonnières et inter?saisonnières de l'approvisionnement en nourriture. Pour les ménages propriétaires terriens, afin de diminuer les risques, les stratégies saisonnières les plus importantes comprennent le choix de l'échelonnement des récoltes nécessitant une culture mixte, la culture de plantes secondaires en particulier de plantes à racines. D'autres mécanismes saisonniers les aident à faire face au problème, tels la vente de petits biens et de bátail, la limitation des produits emmagasinés et l'entretien de relations sociales de soutien mutuel. Un travail salarié procurant un revenu indépendent de celui de la ferme est une des meilleures garantie contre les tensions saisonnières. Si une mauvaise saison se prolonge pour devenir une sécheresse ou qu'une baisse soudaine de pouvoir d'achat se produise, alors ces activités s'intensifient encore plus, mais les familles sont obligées d'avoir recours à des moyens dépréciatifs: vente de biens productifs, réduction des rations de nourriture, migration. Si les investissements dans les secteurs ruraux et de la production alimentaire tenaient compte de ces stratégies, l'effet désastreux de la famine pourrait être évité. RESUMEN Estrategias de alimentación hogareña para responder a la estacionalidad y el hambre Las familias rurales tienen una serie de estrategias para enfrentar las fluctuaciones estacionales e interestacionales de la disponibilidad de alimentos. Para los hogares con tierra, la más importante consiste en la elección de patrones de cultivos para dispersar los riesgos e incluye cultivos mixtos y producción de cultivos secundarios, especialmente raíces. Otro mecanismo estacional reside en la venta de pequeños bienes y animales, el uso de productos almacenados y el desarrollo de relaciones sociales de apoyo. El trabajo remunerado fuera de la granja constituye uno de los mejores amortiguadores en contra de la tensión estacional. Si una mala estación se prolonga en una sequía o si subitamente cae el poder de compra, las actividades mencionadas se intensifican aún más, pero las familias son forzadas a desinvertir recursos, debiendo vender bienes productivos, además de constreñir el consumo de alimentos y emigrar. Si la inversión en áreas rurales y en la producción de alimentos reconociese estas estrategias, el severo impacto del hambre podría evitarse

Pathways curriculum and family interventions to promote healthful eating and physical activity in American Indian schoolchildren

Pathways, a multisite school-based study aimed at promoting healthful eating and increasing physical activity, was a randomized field trial including 1704 American Indian third to fifth grade students from 41 schools (21 intervention, 20 controls) in seven American Indian communities