Biopolymer Drill-in Fluid Performance for Different Rheological Models using Statistical Characterisation

Appropriate selection of rheological models is important for hydraulic calculations of pressure loss prediction and hole cleaning efficiency of drilling fluids. Power law, Bingham-Plastic and Herschel-Bulkley models are the conventional fluid models used in the oilfield. However, there are other models that have been proposed in literature which are under/or not utilized in the petroleum industry. The primary objective of this paper is to recommend a rheological model that best-fits the rheological behaviour of xanthan gum-based biopolymer drill-in fluids for hydraulic evaluations. Ten rheological models were evaluated in this study. These rheological models have been posed deterministically and due to the unrealistic nature have been replaced by statistical models, by adding an error (disturbance) term and making suitable assumptions about them. Rheological model parameters were estimated by least-square regression method. Models like Sisko and modified Sisko which are not conventional models in oil industry gave a good fit. Modified Sisko model which is a four parameter rheological model was selected as the best-fit model since it produced the least residual mean square of 0.61 Ibf2/100ft4. There is 95% certainty that the true best-fit curve lies within the confidence band of this function of interest. Keywords: Biopolymer; Least-Square Regression; Residual Mean Squares; Rheologra

A Qualitative Study of the Meaning for Older People of Living Alone at Home in Rural Ghana

Many people live alone in old age, often with significant health and other challenges. Living alone may contribute to social isolation, with this concept understood as loneliness that has negative influences on health and wellbeing. Alternatively, living alone could be salutogenic (or positive). An interpretive-descriptive study explored the meaning for older adults of living alone at home in rural Ghana, a developing African country. After purposive sampling, multi-day observations and repeated interviews of 10 individuals occurred until data saturation was achieved. Three themes emerged: (a) how they came to be living alone, (b) their variable ability to competently and comfortably live at home alone in old age, and (c) fears associated with living alone in old age. Most of the participants interviewed indicated that living alone was not a choice. Many difficulties with living alone were present, including fears about personal safety and the need to cope with health and income issues. As such, new considerations for old age social isolation were identified. With accelerating population aging, more older people will be living alone, making it essential for health and social policies to be designed in rural and urban areas of each country that address local cultural and economic realities.   &nbsp

Regenerative capacity and factors influencing the management of Mucuna pruriens var. utilis live-mulch

The regenerative capacity of Mucuna pruriens var. utilis live-mulch and factors affecting its management were investigated. Six plots of mucuna (each measuring 48 m2) were established at an intra-row spacing of 40 cm and inter-row spacing of 80 cm. The number of days to canopy closure after planting and after the first, second and third trimmings were recorded. The trimming frequency for early-maturing and late-maturing maize varieties and the biomass yield and number of active nodules per plant were determined. Mucuna pruriens attained complete canopy closure 55 days after planting (DAP). The number of days required for complete canopy closure after the first, second and third trimmings were 34, 32 and 26, respectively. The number of trimmings (60 to 90 DAP) varied from 0-1 (for earlymaturing maize) to 1-2 (for late-maturing maize). The fresh biomass yields at the first, second and third trimmings were 12364, 5941 and 7209 kg ha–1, respectively; while litter yield ranged from 469 to 914 kg ha–1. The effective nodule count per plant varied from 4 (45 DAP) to a maximum of 63 (120 DAP). The N yield (90 days after planting mucuna) was 179 kg ha-1 of which 60 kg ha-1 mineralizable N could be provided for an intercrop. Significant positive relationships were established between biomass yield, N content of mucuna plant, days after planting, and number of effective nodules per plant. The study showed that it would be appropriate to trim M. pruriens two times (at 60 DAP and 34 days after first trimming) during the intercropping of a latematuring maize crop to reduce competition between maize crop and live-mulch for water and plant nutrients in the soil. La capacité régénératrice de paillis vif Mucuna pruriens var. utilis et les facteurs influançant son aménagement étaient étudiés. Six lots de mucuna ( de 48 m² chacun) étaient cultivés avec un espacement 40 cm intra-rayons et un espacement de 80 cm inter-rayons. Les nombres de jours à la fermeture de la canopée après la plantation et après les tailles premières, deuxièmes et troisièmes étaient enregistrées . La fréquence de la taille pour les variétés de maïs de maturation tôt et de maturation tardive, le rendement de la biomasse et le nombre de nodule actif par plante étaient déterminés. Mucuna pruriens ont atteint une fermeture complete de la canopée 55 jours après la plantation. Le nombre de jours exigés pour la fermeture complète de la canopée après les tailles premières, deuxièmes et troisièmes étaient respectivement 34, 32 et 26. Les nombres de taille (60-90 jours après plantation ) variaient de 0-1 ( pour le maïs de maturation tôt ) à 1-2 (pour le maïs de la maturation tardive ) . Les rendements de biomasse fraîche aux tailles premières, deuxièmes et troisièmes étaient 12364, 5941 et 7209 kg ha-¹, respectivement, alors que le rendement de litière variait de 469 à 914 kg ha-¹ . Le compte effectif de nodule par plante variait 4 ( 45 jours après plantation) à un maximum de 63 (120 jours après plantation ). Le rendement d'azote (A) (90 jours après plantation de mucuna) était 179 kg ha-¹ dont 60 kg ha-¹ d'A minéralisable pourrait être disponible à une culture associée. Des rapports positives considérables étaient établis entre le rendement de biomasse, la teneur d'A de la plante mucuna, les jours après la plantation et le nombre de nodules effectifs par plante. L'étude montrait qu'il serait approprié de tailler légèrement M. pruriens deux fois (60 jours après plantation et 34 jours après la taille première ) pendant l'association culturale de la culture du maïs d'une maturation tardive afin de réduire la concurrence pour l'eau et les nutriments de plante dans le sol entre la culture maïs et le paillis vif. Ghana Journal of Agricultural Science Vol. 40 (1) 2007: pp. 51-5