The demand for energy has increased recently worldwide, requiring new oilfield discoveries in order to supply this need. Following this demand increase, challenges grow in all areas of the petroleum industry especially those related drilling operations. Due to hard operational conditions found when drilling complex scenarios such as high pressure/high temperature zones, deep and ultradeep waters and other challenging ones, the use non-aqueous drilling fluids became a must. The reason for that is because this kind of drilling fluid is capable to tolerate these extreme drilling conditions found in those scenarios. However, it can experience changes in its properties as results of pressure and temperature variations, requiring special attention during some drilling operations, such as the well control. To support well control operations and preserve the well integrity, well control simulators are very useful to verify operational parameters and to assist drilling engineers in the decision making process during well control operations and kick situations. Well control simulators are also important computational tools for rig personnel training. This work presents well control research and development contributions, as well as the results of a computational well control simulator that applies the Driller's Method and allows the understanding the thermodynamic behavior of synthetic drilling fluids, such as n-paraffin and ester base fluids. The simulator employed mathematical correlations for the drilling fluids PVT properties obtained from experimental data.The simulator results were compared to a test well data set, as well to published results from other kick simulators.
The influx of gas from formations during drilling or when the well is left undisturbed during tripping, logging, and flow check can dissolve very quickly in Non-aqueous drilling fluids (NAF). The dissolved gas can stay unnoticeable till the gas comes out of solution below bubble point pressure closer to surface. The objective of the paper is to develop a model to predict the time dependent mass transfer of CO2 in oil at subcritical pressures and validate the model using experimental results. Since CO2 is soluble in oil, the interaction between solvent and solute can help us understand the dissolution and mass transfer mechanism of CO2 in oil. A model has been developed by incorporating factors that drive the interaction and the rate of gas loading into the liquid to predict the time-dependent mass transfer. A 1.5 inch vertical low pressure apparatus is used to conduct experiments by injecting CO2 into pressurized static column of oil. Pressure inside the pipe, and mass of CO2 injected are varied to study their effects on mass transfer. Boundary conditions for this model are provided from experimentally obtained data of volumetric mass transfer coefficient of the injected gas and liquid system at gas injection flow rate. The developed time-dependent model has been validated using the data collected from the tests. The volumetric mass transfer coefficient is found to change with pressure. This model can be extended to experiments under high-pressures to replicate the downhole conditions. The model can be modified to include desorption to predict the loading and unloading of gas in NAF, and gas oil ratios at depths along the annulus in a real well.
The demand for energy has increased recently worldwide, requiring new oilfield discoveries in order to supply this need. Following this demand increase, challenges grow in all areas of the petroleum industry especially those related drilling operations. Due to hard operational conditions found when drilling complex scenarios such as high pressure/high temperature zones, deep and ultradeep waters and other challenging ones, the use non-aqueous drilling fluids became a must. The reason for that is because this kind of drilling fluid is capable to tolerate these extreme drilling conditions found in those scenarios. However, it can experience changes in its properties as results of pressure and temperature variations, requiring special attention during some drilling operations, such as the well control. The well control is a critical issue since it involves safety, social, economic and environmental aspects. To support well control operations and preserve the well integrity, well control simulators are very useful to verify operational parameters and to assist drilling engineers in the decision making process during well control operations and kick situations. Well control simulators are also important computational tools for rig personnel training. This work presents well control research and development contributions, as well as the results of a computational well control simulator that applies the Driller’s Method and allows the understanding the thermodynamic behavior of synthetic drilling fluids, such as n-paraffin and ester base fluids. The simulator employed mathematical correlations for the drilling fluids PVT properties obtained from experimental data.The simulator results were compared to a test well data set, as well to published results from other kick simulators.
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