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Upstream oil production using dual string completion, i.e., two tubing inside a well casing, is common due to its cost advantage. High pressure gas is employed to lift the oil to the surface when there is insufficient reservoir energy to overcome the liquids static head in the tubing. However, gas lifting for this type of completion can be complicated. This is due to the operating condition where total gas is injected into the common annulus and then allowed to be distributed among the two strings without any surface control. High uncertainties often result from the methods used to determine the split factor—the ratio between the gas lift rate to one string over the total gas injected. A hybrid model which combined three platforms: the Visual Basics for Application programme, PROSPER (a nodal analysis tool) and Excel spreadsheet, is proposed for the estimation of the split factor. The model takes into consideration two important parameters, i.e., the lift gas pressure gradient along the annulus and the multiphase pressure drop inside the tubing to estimate the gas lift rate to the individual string and subsequently the split factor. The proposed model is able to predict the split factor to within 2% to 7% accuracy from the field measured data. Accurate knowledge of the amount of gas injected into each string leads to a more efficient use of lift gas, improving the energy efficiency of the oil productions facilities and contributing toward the sustainability of fossil fuel.
Chew Chen Law; Mohamed Zamrud Zainal; Kew Hong Chew; Jang Hyun Lee. Hybrid Model for Determining Dual String Gas Lift Split Factor in Oil Producers. Energies 2019, 12, 2284 .
AMA StyleChew Chen Law, Mohamed Zamrud Zainal, Kew Hong Chew, Jang Hyun Lee. Hybrid Model for Determining Dual String Gas Lift Split Factor in Oil Producers. Energies. 2019; 12 (12):2284.
Chicago/Turabian StyleChew Chen Law; Mohamed Zamrud Zainal; Kew Hong Chew; Jang Hyun Lee. 2019. "Hybrid Model for Determining Dual String Gas Lift Split Factor in Oil Producers." Energies 12, no. 12: 2284.
The Total Site Profile (TSP) can be a powerful tool to evaluate the potential for further Heat Integration improvement for a Total Site (TS). A systematic Total Site Heat Integration (TSHI) methodology to target decreasing the capital cost of heat transfer units at Total Sites has been developed. The methodology includes a set heuristics that have been developed to identify and prioritise the strategic process changes to apply, as a result of changes in the TSP shape. The TSP and expanded Total Site Problem TableAlgorithm (TS-PTA) can provide useful insights for the plant designers to identify "where", in terms of which temperature interval, and which streams within the entire TS to focus the process modification efforts. The keep hot stream hot (KHSH) and keep cold stream cold (KCSC) principles can be applied to favourably change the TSP shape to provide a larger temperature driving force to further reduce the HTA and capital costs. In one of the case study, the application of KHSH and KCSC on TSP increases the temperature driving force between the medium pressure steam utility and process resulting in a reduction of 3,827m2 heat transfer area (HTA) and a saving of 10% in heat exchangers cost. The proposed changes to the selected streams should be assessed from feasibility, practicality and economic perspectives. The selected and potentially acceptable process modification options can be conveniently merged with potential retrofit project (e.g. to increase plant capacity) considered for the Total Site
Kew Hong Chew; Jiří Jaromír Klemeš; Sharifah Rafidah Wan Alwi; Zainuddin Abdul Manan. Process modification of Total Site Heat Integration profile for capital cost reduction. Applied Thermal Engineering 2015, 89, 1023 -1032.
AMA StyleKew Hong Chew, Jiří Jaromír Klemeš, Sharifah Rafidah Wan Alwi, Zainuddin Abdul Manan. Process modification of Total Site Heat Integration profile for capital cost reduction. Applied Thermal Engineering. 2015; 89 ():1023-1032.
Chicago/Turabian StyleKew Hong Chew; Jiří Jaromír Klemeš; Sharifah Rafidah Wan Alwi; Zainuddin Abdul Manan. 2015. "Process modification of Total Site Heat Integration profile for capital cost reduction." Applied Thermal Engineering 89, no. : 1023-1032.
This paper extends the scope of the Pinch Analysis for process modifications of individual processes to total site heat integration (TSHI). The Plus-Minus principle has been adapted to enable the beneficial process modification options to be selected in order to maximise energy savings in TSHI. The Total Site Profile (TSP) is divided into three regions: (a) the region above the horizontal overlap between the Site Sink and Source Profiles, (b) the horizontal overlap region and (c) below the horizontal overlap region. The proposed methodology identifies the options to reduce utility targets in these regions using the TSP, Site Utility Composite Curves (SCC), Utility Grand Composite Curve (UGCC), modified Problem Table Algorithm (PTA), Total Site Problem Table Algorithm (TS-PTA) and some new heuristics. The identified changes on the TSP are then linked to the specific changes at the individual processes. The illustrative case study shows that the Plus-Minus principle application in the TSHI context can further improve heat recovery. The proposed spreadsheet-based methodology combines the advantages of graphical visualisation, as well as the numerical precision
Kew Hong Chew; Jiří Jaromír Klemeš; Sharifah Rafidah Wan Alwi; Zainuddin Abdul Manan. Process modifications to maximise energy savings in total site heat integration. Applied Thermal Engineering 2015, 78, 731 -739.
AMA StyleKew Hong Chew, Jiří Jaromír Klemeš, Sharifah Rafidah Wan Alwi, Zainuddin Abdul Manan. Process modifications to maximise energy savings in total site heat integration. Applied Thermal Engineering. 2015; 78 ():731-739.
Chicago/Turabian StyleKew Hong Chew; Jiří Jaromír Klemeš; Sharifah Rafidah Wan Alwi; Zainuddin Abdul Manan. 2015. "Process modifications to maximise energy savings in total site heat integration." Applied Thermal Engineering 78, no. : 731-739.
Pressure drop is an important consideration in Total Site Heat Integration (TSHI). This is due to the typically large distances between the different plants and the flow across plant elevations and equipment, including heat exchangers. Failure to consider pressure drop during utility targeting and heat exchanger network (HEN) synthesis may, at best, lead to optimistic energy targets, and at worst, an inoperable system if the pumps or compressors cannot overcome the actual pressure drop. Most studies have addressed the pressure drop factor in terms of pumping cost, forbidden matches or allowable pressure drop constraints in the optimisation of HEN. This study looks at the implication of pressure drop in the context of a Total Site. The graphical Pinch-based TSHI methodology is extended to consider the pressure drop factor during the minimum energy requirement (MER) targeting stage. The improved methodology provides a more realistic estimation of the MER targets and valuable insights for the implementation of the TSHI design. In the case study, when pressure drop in the steam distribution networks is considered, the heating and cooling duties increase by 14.5% and 4.5%.
Kew Hong Chew; Jiří Jaromír Klemeš; Sharifah Rafidah Wan Alwi; Zainuddin Abdul Manan; Andrea Pietro Reverberi. Total Site Heat Integration Considering Pressure Drops. Energies 2015, 8, 1114 -1137.
AMA StyleKew Hong Chew, Jiří Jaromír Klemeš, Sharifah Rafidah Wan Alwi, Zainuddin Abdul Manan, Andrea Pietro Reverberi. Total Site Heat Integration Considering Pressure Drops. Energies. 2015; 8 (2):1114-1137.
Chicago/Turabian StyleKew Hong Chew; Jiří Jaromír Klemeš; Sharifah Rafidah Wan Alwi; Zainuddin Abdul Manan; Andrea Pietro Reverberi. 2015. "Total Site Heat Integration Considering Pressure Drops." Energies 8, no. 2: 1114-1137.