Topics on Integrated Asset Modelling, Production Systems Boosting and Virtual Metering
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This thesis addresses four existing gaps and missing facilities in the route to improve the capabilities to model an entire oil and gas field extending from the reservoir to the field sales point. Such a model, referred by the oil and gas industry as Integrated Asset Model (IAM), enables mathematical assessments of the trade-offs between design, operational alternatives and mathematical optimization subject to the entire system constraints. The gaps and issues addressed are divided into the following chapters: Chapter 1- Describes the basics of the IAM approach and software packages throughout used in this research. Chapter 2- Describes a methodology to develop a low cost field simulator tool where coupling a hydrocarbon production system, from reservoir to the sales point is presented. A gas-condensate reservoir has been chosen, scaled-up by previous researchers. The study undertakes a compositional characterization of the reservoir fluids, and calculations of flow in reservoir, wells, surface network, and LNG plant. Some of the challenges faced have been the coupling and transfer of information of thermodynamic models and fluid properties from the reservoir to the production network system. Linking reservoir and process simulator to get a field production simulator can be a very useful tool but it still need to be improved on running the simulator for each Reservoir time step and Process Simulator and reservoir fluid updates before moving to the next reservoir time step. Chapter 3- Proposes the development of a tool inside the Process Simulator Hysys that applies the Huntington method (1985) for calculation of a subsea compressor polytropic head (Wet Gas Compressor). The current methods available in the process simulator Hysys are valid only for dry gas. For wet gas these models fail. Previous authors(For example Hundseid 2006-2008) have worked on the topic before but none of them developed it as a routine and made available as a tool in the process simulator where it is easier to use even for those that are not familiar with the complex calculations. Implementing a routine in the process simulator, would make available a tool for wet gas compressor calculation. Chapter 4- Presents a model-based study for accelerated production of an oil field. It combines two mature Enhanced Oil Recovery technologies: Miscible of Water-Alternating-Gas (WAG) injection and a down hole Electric Submersible Pump (ESP). The field used as test case was a Multi-well oil field undergoing WAG, originally studied by Killough and Kossack (1987). The integrated approach proposed for field production strategy with the ESP is relevant with regard to the achievable early production. Gas-Alternating-Water recovery method with the installation of an ESP has shown accelerating oil recovery although the investment costs can be high Chapter 5- Deals with the fluid dynamic and thermodynamic aspects of Chokes. The first part of the chapter presents predictions of the outlet temperature. Different combinations of thermodynamic processes, containing expanders and valves, have been considered to identify the configuration that better represents the experimental data (gathered by a previous researcher) in a process simulator. There are recognized areas governed by gas, oil and water, and some differences among the configurations of the model. It was observed that the pressure drop across the Choke is not fully isenthalpic as there was enthalpy variation. The biggest variation was observed in the gas dominated zone. The second part of the chapter deals with the prediction of mass flow from wells using chokes, based on available inlet and outlet measurements –pressure and temperature. The simple Bernoulli equation adapted for multiphase outperformed some of well known models used in the oil and gas industry. Because of its good performance, this new technology could reduce costs with the installation of physical multiphase flowmeters in subsea wells. With those models included in an IAM tool a reliable and low-cost tool can be available for field development studies, field planning and operations.