The melting process of polyethylene glycol 1500 (PEG 1500) adjacent to a hot vertical wall in a rectangular enclosure is investigated experimentally. Polyethylene glycol 1500 was selected because its melting temperature is >44 0 C making it a suitable candidate as lagging material to prevent wax deposition and hydrate formation in subsea oil pipelines. A new apparatus cell consisting of a rectangular cell 200x200x180mm split equally into three chambers by two, 2mm thick, aluminium plates was constructed. Each end chamber was supplied with hot and cold water respectively. The centre chamber was filled with PEG1500.Thermocouples and an infrared camera were used to measure the temperature at different locations inside and on the surface of the phase change material (PCM). The temperature contours, percentage (%) of melting and the melt front evolution are presented for various operating conditions. A dye tracer solution was used to show the natural circulation of the PCM as it melted. Results indicate that during the initial stage of melting heat conduction is the dominating mode of heat transfer, followed by transition from conduction to convection regime and convection dominating heat transfer regime. The results show a strong correlation between the hot wall temperature and the fraction melt as it control the convection heat transfer. In contrast, the results also show that cold wall temperature have insignificant effect on fraction of PCM melt with the time for constant hot wall temperature and the melt rate has a same characteristic shape for all cold wall temperatures used in this study. A dye tracer study shows the natural circulation in the liquid zone, confirm the presence of the strongest convection at the solid-liquid interface and reveal the velocity profile/current direction. An approximate time of six minutes was recorded for the circulation of the solution round the enclosure giving approximate velocity of 0.00117 m/s.

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After a field has been put on production, it is very pertinent that the saturation and contact changes within the reservoir be monitored. This is difficult on a frequent basis considering the cost implications of the processes involved. Usually, the main two methods employed are the use of PNC/PNS (C/O and Sigma) logs, and the 4D-Seismic. The latter, though the more recent, has been gathering popularity especially in the Gulf of Mexico and North Sea, because of its relatively easier and seemingly more dependent concepts. However, the PNC/PNS logs remain the major method used for contact monitoring. Data generated from post-production saturation monitoring campaigns are used for proper reservoir management, generation of short-term oil gains, and reducing risks in planned new wells. Beyond these basic uses, the operation can also help to properly analyse the status of the wells, as well as redefine uncertainty level and reveal new information concerning the wells and reservoir conditions. In this work, a Niger Delta field that has been producing for about 20 years was analysed after the first post-production C/O log campaign was conducted. The logs were interpreted and the results were analysed. Apart from the observations common to the results of such operations, some other insights were revealed by this campaign, particularly in one of the wells producing from the field. The well was completed across two reservoirs, with the shallower completion put behind sleeves, while the deeper was put on production. A major boundary fault seals the reservoirs vertically, ensuring that no external communication was possible. From the production data corresponding to the producing deeper reservoir, it was expected that the logs would confirm that the reservoir was about to quit considering the fact that it had already exceeded its EUR (high). However, after the logs were double-checked for errors and analysed, it was discovered that the shallower reservoir, which has never been put on production, has been partially flushed, and the deeper reservoir, which was expected to be watered out, still had some reasonable amount of oil in place. With these striking discoveries, a full field analysis was done, the details of which was discussed in this paper. At the end of this work, some recommendations were made. This underlines the importance of frequent reservoir monitoring operations. This will help unravel and understand anomalous developments that could be occurring in the field/wells without the knowledge of the operators.

In this paper, the primary aim is to look at the fundamental melting/solidification processes of polyethylene glycol 1500 (PEG 1500) for energy storage – insulation to prolong the cooling time of pipelines in unexpected shut-down conditions, prevent/minimize the wax deposition, and hydrate formation. Polyethylene glycol 1500 was selected because its melting temperature is >317 K making it a suitable candidate as lagging material to prevent wax deposition and hydrate formation in subsea oil pipelines. Experimental apparatus was designed with the Perspex to give an insight into the melting process. Vertical and horizontal annular geometries were used to consider the real-life cases. The vertical annular enclosure length is 950 mm and 34 mm width (Height/Width=27.94). The horizontal annular enclosure length is 300mm and 15.9 mm width (Height/Width=18.87). The thermocouples and camera are used to collect the data for three cases of inner wall temperature of 333 K,343 K and 353 K where is the heat added to the phase change material (PCM) for both cases. The main conclusions are: i) the horizontal annular case melt faster than the vertical case, in particular, at higher heating surface temperature of 353 K, ii)The temperature of the inner region was remained hot for long time which provide a good evidence that support the concept of using the PCM as heat storage–insulation material; iii) the melting percentage for horizontal case is 100% higher from the melting percentage of vertical case at 333 K which reduced to about 20% for 343 K, iv) increasing the heating surface temperature substantially reduces the total melting time for both orientations.