The transition of one flow regime into another is a very networks, which could be potentially hazardous for

The utilization of T‐junctions for flow division is quite common in industries. Due to the phenomena known as multiphase maldistribution, occurring in a T‐junction, they are often used as partial phase separators for reducing the work load on phase separation devices in oil and gas platforms. Previous literature says that reducing the diameter ratio of the T‐junction improves the two‐phase separation, however it was also reported that reducing the diameter ratio too much has a negative effect on two‐phase separation. To test this, a numerical study was performed to see the two‐phase stratified flow separation in 1, 0.6 and 0.167 diameter ratio T‐junctions. Furthermore, the impact of air superficial velocity on phase maldistribution at the junction is also considered. The T‐junctions with diameter ratios 1 and 0.6 were just used for the validation of present model, by comparing the obtained numerical results with previous experimental data. While, 0.167 diameter ratio T‐junction is the one for which the actual analysis was performed. It is concluded that an increase in air superficial velocity aids liquid carryover, whereas liquid carryover is very sensitive to side arm extraction rates in a very small diameter ratio T‐junction.

The transition of one flow regime into another is a very common phenomena in pipeline networks, which can be potentially hazardous for the structural integrity of the pipeline. Literature review showed that there is almost no reported detail investigation of transitional flow whereby the fluid constituents change from one regime to another especially slug transition. Most of the open research papers focused on slug flow regime and its liquid holdup in horizontal pipelines and channels have been carried out on experimental test rigs. The objective of this study is to explore oil-gasoil vapor slug transition and its liquid holdup in a 3.15 inch diameter horizontal straight pipe. The abrupt change in gas/liquid velocities, which causes transition of flow patterns is analyzed using incompressible Volume of Fluid (VOF) method, along with Piecewise Linear Interface Construction (PLIC) technique to capture the sharp front of segregated gas-liquid interface. Slug liquid holdup derived from the present numerical model is compared to existing experimental correlations in the literature.

Flow assurance problems related to flow slugging, hydrates, and wax gelling lead to this study, post two integrated oil pipelines clogged in the Caspian Sea during the winter season. The methods and proposed solutions will be further deliberate, which includes the development of operating envelope to ease implementation. The overall methodology is based on dynamic flow assurance simulation and mathematical analysis, which was adapted depending on the problem being studied. Reduced production and terrain undulations had caused severe slugging in both pipelines which are flowing multiphase fluids. The bifurcation analysis of slug control valve will be discussed to determine the best choke opening that can eliminate slugging. The flow slugging also caused hydrate risk that was made worst during shutdown. Few strategies of hydrate mitigation including implementing extra heat insulation at riser air gap, gas flaring, optimised and overdose injection of mono ethylene glycol (MEG) were considered. Hydrate mass was evaluated for all the mitigations and requirement to inject lean MEG immediately after shutdown or prior start-up was identified. In terms of wax management, lower Flowing Tubing Head Temperature (FTHT) from wells added a challenge with limited facilities capability to operate more than the wax appearance temperature (WAT). Operating envelope of crude oil heater under heating limitation will be clearly shown to avoid operating in wax region. The development of operating envelope had enabled Operations personnel to know the safe condition to operate both pipelines during critical scenarios. The approach has changed the way the company operates, to ensure production is protected and maintained with minimal disruption caused by slugging, hydrate and wax gelling events.

In Malaysia more than 13 Tscf of natural gas reserve remain undeveloped due to high carbon dioxide (CO2) content of up to 70 mole% (Darman & Harun, 2006). High CO2 content gas fields will have to be developed to meet gas demand in Malaysia despite the technical and economical challenges. Cryogenic technology has been identified to be the most suitable technology for offshore since it is capable of handling a wide range of CO2 content. However, proper phase behavior study should be undertaken as CO2 may freeze-out to become solid at certain cryogenic conditions. The objective of this study is to validate the prediction of commonly used Equation of State (EOS) models on the Vapor, Liquid & Solid Equilibrium (VLSE) of CO2 - hydrocarbon system against existing experimental data and to simulate cryogenic process to remove CO2 for offshore application. Primary focus is given to the accurate prediction of solid CO2 behavior using conventional EOS models. Based on the selected EOS model, a phase behavior study under cryogenic condition has been conducted on a gas field containing CO2 level up to 52 mole% in the wellstream. A process simulation model is developed based on Ryan Holmes and Controlled Freeze Zone#x2122; (CFZ#x2122;) processes. In this study various feed and process conditions were evaluated to determine the optimal removal of CO2 from the wellstream. The proper representation of the actual high CO2 gas reservoir VLSE phase behavior using the available EOS model is very important to avoid unnecessary facility problem for a cryogenic technology application. From this study, advanced Redlich-Kwong-Soave (RKSA) model is recommended to be used for high CO2 fluid characterization and simulation.

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Temperature-dependent viscosity is one of critical properties in designing facilities for waxy crude oil production. Several viscosity models have been developed and available in literature. Nevertheless, those models are still insufficient to cover all waxy crude oil produced from various regions. Therefore, this work aims to develop a general viscosity model for Malaysian waxy crude oils. Extensive rheological study was conducted and showed that viscosity behavior below WAT can be best described using Herschel-Buckley model. Multiple correlation and regression analysis were also performed to identify critical physico-chemical properties dictating the viscosity behavior. Based on the finding, a general viscosity model was developed by modifying Herschel-Buckley model and incorporate the critical physico-chemical properties. The general model was compared with widely used viscosity model and other models available in literatures to assess its performance on describing the viscosity behavior. The comparison showed that the general model has lowest average absolute percentage error and hence, it is more superior than the other models. Nevertheless, the model still has limitation in describing viscosity at the transition regime which is between WAT and 5°C below WAT.