Simulation of Subsea and Platform Production Schemes to Quantify Flow Assurance Risks under Transient and Steady State Conditions in Offshore Kuwait

2021 ◽  
Author(s):  
Eissa Al-Safran
Keyword(s):  
Steady State ◽  
Optimum Design ◽  
Capital Investment ◽  
Flow Assurance ◽  
Field Development ◽  
Development Scheme ◽  
Production Scheme ◽  
Simulation Results ◽  
Steady State Simulation ◽  
Offshore Development

Abstract In offshore production, the type of field development scheme is crucial aspect due to its associated flow assurance risks, which affect project economic, safety, and sustainability. The objective of this study is to simulate and evaluate two offshore field development schemes, namely subsea and platform in offshore Kuwait. Further objective is to carry out detailed transient simulation study on the subsea scheme to investigate flow assurance risks related to terrain slugging, and hydrates formation during shut-in and re-start transient events. The evaluation of the two schemes is based on the associated flow assurance risks, and project economics. Steady state simulations are used to identify the feasible production scheme, which is further simulated under transient shut-in/restart events to investigate flow assurance risks related to terrain slugging and hydrates formation. The steady state simulation results of this study showed that flow assurance risks such as hydrates and pipeline corrosion are significant in both production schemes. To mitigate these risks, sixteen different field development designs of both production schemes were simulated and economically evaluated. Results revealed that the subsea multiphase development scheme with 10-in. ID carbon steel multiphase flowline and 0.3-in. thick polypropylene thermal insulation is the optimum design. Consequently, the optimum design is further analyzed under transient conditions, resulting in appreciable risk of terrain slugging due to hilly-terrain pipeline configuration, especially for the low production rate cases. The transient shut-in/restart simulation results revealed a risk of hydrates formation due to cooling effect during shut-in, which is mitigated by MEG injection. In conclusion, the subsea multiphase flow scheme is selected over platform scheme due to manageable flow assurance risks, low capital investment cost, and minimum environmental impact. This study would enable Kuwait Oil Company to evaluate different offshore development schemes to ensure sustainable production with safe operation and protected environment.

Thermal Hydraulics of Accelerator-Driven System Using RELAP5 Code

2015 ◽  
Vol 1 (4) ◽  
Author(s):  
Indu Kumari ◽  
Ashok Khanna
Keyword(s):  
Steady State ◽  
Constant Heat ◽  
Power Extraction ◽  
Driven System ◽  
Design Values ◽  
Accelerator Driven System ◽  
Simulation Results ◽  
Steady State Simulation ◽  
Heat Loads ◽  
Relap5 Code

A lead–bismuth eutectic (LBE)-cooled accelerator-driven system (ADS) of 30 MeV and 0.5 mA proton beam has been simulated. The performance of this 15-kW ADS has been analyzed for three coolants (LBE, air, and water), all under variable and constant heat loads using the thermal hydraulic code RELAP5/Mod4.0. Steady-state simulation results for temperature of coolants match the reported design values within 3.2% of relative error. The effect of variation of mass flow rate on power extraction has also been evaluated for the three coolants, namely, LBE, air, and water.

Comparisons of Steady and Time-Averaged Unsteady Flow Predictions for Impeller–Diffuser Interactions in a Centrifugal Compressor Stage

2007 ◽  
Author(s):  
N. He ◽  
A. Tourlidakis ◽  
R. L. Elder
Keyword(s):  
Steady State ◽  
Velocity Field ◽  
Pressure Field ◽  
Vaned Diffuser ◽  
Unsteady Simulation ◽  
Simulation Results ◽  
The Difference ◽  
Steady Simulation ◽  
Steady State Simulation ◽  
Isentropic Efficiency

In the present paper a computational analysis of the interactions between a backswept impeller and its downstream vaned diffuser in a high-speed centrifugal compressor is presented. Both steady and unsteady simulations are carried out at the peak efficiency point. Geometry scaling was used in the unsteady simulation in order to deal with the problem of unequal pitch. For the steady simulation, an averaging approach is used at the interface between the impeller and the diffuser. A detailed comparison between the time averaged unsteady results and the steady simulation results is performed and some unsteady phenomena are also discussed in order to advance the understanding of the flow physics involved. One important conclusion is that the unsteady simulation is important since the difference between the time averaged unsteady results and steady simulation results is quite significant especially in the velocity field and the stage efficiency. From the comparisons of the predicted results with available experimental data in terms of velocity vectors and isentropic efficiency, it can be concluded that the geometry scaling method used in the current unsteady simulation is reasonable and successful and the computational model employed for the predictions consists a reliable computational tool. In general, the contours of different flow variables for the averaged unsteady simulation results are more uniform than the steady ones, especially in the vaneless space. In the static pressure field, there are relatively small differences. The main differences occur in the region of the vaneless space and downstream of the throat area, and in general the difference is found to be quite small. In the velocity field, the differences are large compared with the ones occurring in the pressure field. The area with the largest differences extends from the vaneless space into the semi-vaneless and vaned diffuser channel. The unsteadiness also modifies the flow angle and hence the incidence angle at the leading edge of the vaned diffuser, the maximum difference can reach 3 degrees. The difference in the stage isentropic efficiency can reach above 1 per cent, which is considered to be quite high. The results also indicate that the larger differences between the time-averaged unsteady and steady state simulation results usually occurred in the area that flows are highly unsteady or nearly separated. Consequently the steady state simulation is still not very accurate to predict highly unsteady flow and separated flows.

Integrated Subsurface to Surface Modeling to Assess Reservoir Uncertainty Quantification to A Carbonate Reservoir

2020 ◽  
Author(s):  
A. Chaterine
Keyword(s):  
Uncertainty Quantification ◽  
Gas Production ◽  
Carbonate Reservoir ◽  
Production Volume ◽  
Production Forecast ◽  
Uncertainty Range ◽  
Field Development ◽  
Production Forecasting ◽  
Production Scheme ◽  
Rock Compressibility

This study accommodates subsurface uncertainties analysis and quantifies the effects on surface production volume to propose the optimal future field development. The problem of well productivity is sometimes only viewed from the surface components themselves, where in fact the subsurface component often has a significant effect on these production figures. In order to track the relationship between surface and subsurface, a model that integrates both must be created. The methods covered integrated asset modeling, probability forecasting, uncertainty quantification, sensitivity analysis, and optimization forecast. Subsurface uncertainties examined were : reservoir closure, regional segmentation, fluid contact, and SCAL properties. As the Integrated Asset Modeling is successfully conducted and a matched model is obtained for the gas-producing carbonate reservoir, highlights of the method are the following: 1) Up to ± 75% uncertainty range of reservoir parameters yields various production forecasting scenario using BHP control with the best case obtained is 335 BSCF of gas production and 254.4 MSTB of oil production, 2) SCAL properties and pseudo-faults are the most sensitive subsurface uncertainty that gives major impact to the production scheme, 3) EOS modeling and rock compressibility modeling must be evaluated seriously as those contribute significantly to condensate production and the field’s revenue, and 4) a proposed optimum production scenario for future development of the field with 151.6 BSCF gas and 414.4 MSTB oil that yields a total NPV of 218.7 MMUSD. The approach and methods implemented has been proven to result in more accurate production forecast and reduce the project cost as the effect of uncertainty reduction.

scholarly journals Spatiotemporal Patterns Formed by a Discrete Nutrient-Phytoplankton Model with Time Delay

Complexity ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-18
Author(s):  
Feifan Zhang ◽  
Wenjiao Zhou ◽  
Lei Yao ◽  
Xuanwen Wu ◽  
Huayong Zhang
Keyword(s):  
Steady State ◽  
Time Delay ◽  
Numerical Simulations ◽  
Functional Response ◽  
Bifurcation Analysis ◽  
Discrete Model ◽  
Continuous Model ◽  
Spatiotemporal Patterns ◽  
Homogeneous Steady State ◽  
Simulation Results

In this research, a continuous nutrient-phytoplankton model with time delay and Michaelis–Menten functional response is discretized to a spatiotemporal discrete model. Around the homogeneous steady state of the discrete model, Neimark–Sacker bifurcation and Turing bifurcation analysis are investigated. Based on the bifurcation analysis, numerical simulations are carried out on the formation of spatiotemporal patterns. Simulation results show that the diffusion of phytoplankton and nutrients can induce the formation of Turing-like patterns, while time delay can also induce the formation of cloud-like pattern by Neimark–Sacker bifurcation. Compared with the results generated by the continuous model, more types of patterns are obtained and are compared with real observed patterns.

scholarly journals Adaptive modulation based on steady-state mean square error for underwater acoustic communication

2021 ◽  
Vol 2021 (1) ◽  
Author(s):  
Zhiyong Liu ◽  
Zhoumei Tan ◽  
Fan Bai
Keyword(s):  
Steady State ◽  
Mean Square Error ◽  
Adaptive Modulation ◽  
Blind Equalization ◽  
Training Sequence ◽  
Transmission Efficiency ◽  
Underwater Acoustic Communication ◽  
Mean Square ◽  
Modulation Mode ◽  
Simulation Results

AbstractTo improve the transmission efficiency and facilitate the realization of the scheme, an adaptive modulation (AM) scheme based on the steady-state mean square error (SMSE) of blind equalization is proposed. In this scheme, the blind equalization is adopted and no training sequence is required. The adaptive modulation is implemented based on the SMSE of blind equalization. The channel state information doesn’t need to be assumed to know. To better realize the adjustment of modulation mode, the polynomial fitting is used to revise the estimated SNR based on the SMSE. In addition, we also adopted the adjustable tap-length blind equalization detector to obtain the SMSE, which can adaptively adjust the tap-length according to the specific underwater channel profile, and thus achieve better SMSE performance. Simulation results validate the feasibility of the proposed approaches. Simulation results also show the advantages of the proposed scheme against existing counterparts.

Cyclic Breathing Simulations in Large Scale Models of the Lung Airway From the Oronasal Opening to the Terminal Bronchioles

2012 ◽  
Author(s):  
D. Keith Walters ◽  
Greg W. Burgreen ◽  
Robert L. Hester ◽  
David S. Thompson ◽  
David M. Lavallee ◽  
...  
Keyword(s):  
Steady State ◽  
Boundary Conditions ◽  
Large Scale ◽  
Whole Body ◽  
Patient Specific ◽  
Cfd Simulations ◽  
Reduced Order ◽  
Scale Models ◽  
Steady State Simulation ◽  
Conducting Zone

Computational fluid dynamics (CFD) simulations were performed for unsteady periodic breathing conditions, using large-scale models of the human lung airway. The computational domain included fully coupled representations of the orotracheal region and large conducting zone up to generation four (G4) obtained from patient-specific CT data, and the small conducting zone (to G16) obtained from a stochastically generated airway tree with statistically realistic geometrical characteristics. A reduced-order geometry was used, in which several airway branches in each generation were truncated, and only select flow paths were retained to G16. The inlet and outlet flow boundaries corresponded to the oronasal opening (superior), the inlet/outlet planes in terminal bronchioles (distal), and the unresolved airway boundaries arising from the truncation procedure (intermediate). The cyclic flow was specified according to the predicted ventilation patterns for a healthy adult male at three different activity levels, supplied by the whole-body modeling software HumMod. The CFD simulations were performed using Ansys FLUENT. The mass flow distribution at the distal boundaries was prescribed using a previously documented methodology, in which the percentage of the total flow for each boundary was first determined from a steady-state simulation with an applied flow rate equal to the average during the inhalation phase of the breathing cycle. The distal pressure boundary conditions for the steady-state simulation were set using a stochastic coupling procedure to ensure physiologically realistic flow conditions. The results show that: 1) physiologically realistic flow is obtained in the model, in terms of cyclic mass conservation and approximately uniform pressure distribution in the distal airways; 2) the predicted alveolar pressure is in good agreement with previously documented values; and 3) the use of reduced-order geometry modeling allows accurate and efficient simulation of large-scale breathing lung flow, provided care is taken to use a physiologically realistic geometry and to properly address the unsteady boundary conditions.

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