This study focuses on heat transfer characteristics of phase change material (PCM) during energy storage and release in vertical double pipe configuration. Paraffin wax with an average melting temperature of 52 °C is used as the energy storage material and water is used as the heat transfer fluid (HTF). The heat transfer fluid flows in the inner tube and the wax is stored on the shell side. Eighteen thermocouple wires are placed in the wax to provide a detailed measurement for the temperature field during energy storage and release. Measurements are made as a function of the flow direction, flow rate, and inlet temperature of the heat transfer fluid. Results indicate that natural convection dominates the melting process for upward flow of the heat transfer fluid. On the other hand, the solidification process is dominated by conduction. During melting and upward flow of the HTF, the density difference of hotter and cooler molten wax layers initiates natural convection cells. Further mixing within the melt is also caused by descent of the higher density solid wax.
Asphaltene precipitation is considered a precursor of the plugging of oil wells and subsurface equipment and is a topic of continuous interest among companies and academic institutions. Numerous models to predict asphaltene precipitation at reservoir conditions have emerged over the years, and some have been dropped for several reasons. One particular case is the utilization of cubic equations of state such as Peng–Robinson (PR) and Soave–Redlich–Kwong (SRK), which although are relatively simple to code and utilize, have not been as effective in predicting asphaltene precipitation as compared to other models such as the perturbed chain version of the statistical associating fluid theory equation of state (PC-SAFT EOS). However, we have found that after improving the crude oil characterization procedure to obtain a proper set of simulation parameters from the available experimental data, the cubic equation of state can show excellent predictive capabilities in modeling asphaltene onset pressure under gas injection. In this work, we develop a characterization methodology based on the contents of Saturates–Aromatics–Resins–Asphaltenes (SARA) that can be used with PR EOS. Several case studies with published data from six crude oils are conducted to assess the predictive capability of the new approach in modeling asphaltene onset pressure under gas injection. Comparisons are made with PC-SAFT EOS to highlight the advantages and disadvantages of each model. Also, the modeling approach is tested against high-pressure and high-temperature data from four wells from the Middle East that have not been previously published in the literature. The results indicate that PR EOS yields results that are at least as good as those obtained from PC-SAFT in predicting the onset of asphaltene precipitation in crude oil under various amounts and types of gas injection.
Jurassic Reservoirs in Abduliyah field of West Kuwait are characterized by abnormal pressure variation within and across Jurassic formations, which cause profound drilling problems such as well kicks and mud losses resulting in increased drilling time, cost and materials in addition to reservoir damages. The development of Najmah –Sargelu (NJ/SR) unconventional fractured reservoir requires drilling through high-density fracture swarms to ensure well productivity, which in many instances result in "alternate loss & gain scenario," occasionally, making the well control options limited. On the other hand, drilling through Marrat section encounters drilling difficulties such as mud loss and differential sticking in depleted middle Marrat layers juxtaposed to high-pressure layers of upper intervals. Keeping the above problems in mind, Managed pressure Drilling (MPD) was applied first time in both 9-1/4″ NJ-SR & 6-1/2″ Marrat reservoir sections in a deviated well of Abduliyah field. The Use of MPD in this well offered several advantages and improvements in drilling and completion performance as given below: Reduction in Operation Time: Successfully drilled through Base Gotnia, Najmah-Sarjelu & Marrat Formations to Target Depth smoothly without any Non-productive Time (NPT) Down hole problem avoidance: No downhole complications experienced during drilling to Target Depth. Implementation of new casing design: Drilled Najmah-Sarjelu, Dharuma, Up. Marrat and Upper part of Middle Marrat in the same section for the first time in Abduliyah field which allows future re-entry sidetracking using 6 ½″ horizontal wellbores to enhance productivity for cost-optimal development of NJ-SR & Marrat reservoirs. Reduction in drilling fluid density: The sections were drilled with lower drilling fluid density by 1.5-2.0 ppg resulting in optimum overbalance pressure to avoid formation damage while reducing the risk of differential stuck pipe, with savings in mud cost. Health Safety & Environment (HSE) Improvement: The MPD sections were drilled without any incident indicating improved HSE performance. Reduction in overall well cost: Significant cost reduction was achieved by using MPD for drilling the sections. The paper aims to share the successful case study of drilling through Jurassic reservoir sections of Abduliyah deviated well using MPD technology along with lessons learned and benefits for its future implementation in similar wells across all KOC assets
While drilling through a reservoir, a lot of valuable information can be obtained from mud logging to support formation evaluation. Field data will help wellsite geologists, petrophysicist and reservoir engineers to predict reservoir quality, fluid contacts and reservoir permeability based on formation gases detected while drilling. This study discusses some examples from exploratory wells that have recently been drilled in Kuwait. Gas readings were recorded while drilling through Cretaceous and deep Jurassic formations to evaluate hydrocarbon content using Advanced Gas Chromatography. The primary components of the system utilized are: a constant volume gas extractor, a gas sample flow control system, and a high resolution chromatographic system. To interpret the findings Gas readings are monitored by a complex system which provides real-time continuous measurements of the concentration of formation gases from very light components such as methane, to heavy components such as C6, C7 and C8 hydrocarbon species, comprising n-hexane, n-heptane, n-octane, benzene and toluene. Formation gas is considered as the first indication of a reservoir's fluid characterization and reflects the extent of the productivity of the well. Geochemical ratios and equations can enhance the interpretation of field data and give the first indication of zones of interest that need further evaluation. The integration of the gas data along with the drilling parameters (ROP, ΔFlow) can be of valuable inputs to quantify the Rock properties such as porosity and permeability, this new approach can extend the utilization of gas data not only for formation evaluation and fluid characterization but also for formation petro-physical structure. To take advantage of the field data, the gas readings are plotted on a depth log, which can be easily integrated with other data. Geochemical equations are plotted against depth and lithology to determine fluid type, contacts and evolution.
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