The Experts below are selected from a list of 234 Experts worldwide ranked by ideXlab platform
Sigurd Skogestad - One of the best experts on this subject based on the ideXlab platform.
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Subsea solution for anti-slug control of multiphase risers
2013 European Control Conference (ECC), 2013Co-Authors: Esmaeil Jahanshahi, Sigurd Skogestad, M. LieunghAbstract:A top-side choke valve is usually used as the manipulated variable for anti-slug control of multi-phase risers at Offshore Oil-Fields. With new advances in the subsea technology, it is now possible to move top-side facilities to the sea floor. The two main contributions in this paper are to consider an alternative location for the control valve and to consider how to deal with nonlinearity. This research involved controllability analysis based on a simplified model fitted to experiments, simulations using the OLGA simulator, as well as an experimental study. It was concluded that a control valve close to the riser-base is very suitable for anti-slug control, and its operation range is the same as the top-side valve. However, a subsea choke valve placed at the well-head can not be used for preventing the riser-slugging.
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ECC - Subsea solution for anti-slug control of multiphase risers
2013 European Control Conference (ECC), 2013Co-Authors: Esmaeil Jahanshahi, Sigurd Skogestad, M. LieunghAbstract:A top-side choke valve is usually used as the manipulated variable for anti-slug control of multi-phase risers at Offshore Oil-Fields. With new advances in the subsea technology, it is now possible to move top-side facilities to the sea floor. The two main contributions in this paper are to consider an alternative location for the control valve and to consider how to deal with nonlinearity. This research involved controllability analysis based on a simplified model fitted to experiments, simulations using the OLGA simulator, as well as an experimental study. It was concluded that a control valve close to the riser-base is very suitable for anti-slug control, and its operation range is the same as the top-side valve. However, a subsea choke valve placed at the well-head can not be used for preventing the riser-slugging.
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Comparison between nonlinear model-based controllers and gain-scheduling Internal Model Control based on identified model
52nd IEEE Conference on Decision and Control, 2013Co-Authors: Esmaeil Jahanshahi, Sigurd SkogestadAbstract:Instability and inverse response behaviour make anti-slug control at Offshore Oil-Fields an interesting control problem where a robust solution considering the nonlinearity of the system is required. We tested three control solutions by experiments in this paper. First, we used state-feedback with state estimation by a nonlinear high-gain observer. Secondly, we applied feedback linearization with measured outputs. Finally, we designed gain-scheduling IMC (Internal Model Control) based on linear models identified from closed-loop step test. We compared these three solutions in terms of robustness and their range of operation. The high-gain observer was only applicable by using the top-side pressure measurement in a limited range; it was not stable when using the the subsea pressure measurement in closed loop. The IMC method was more robust against time-delay in the subsea pressure measurement compared to the feedback linearizing controller.
Esmaeil Jahanshahi - One of the best experts on this subject based on the ideXlab platform.
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Subsea solution for anti-slug control of multiphase risers
2013 European Control Conference (ECC), 2013Co-Authors: Esmaeil Jahanshahi, Sigurd Skogestad, M. LieunghAbstract:A top-side choke valve is usually used as the manipulated variable for anti-slug control of multi-phase risers at Offshore Oil-Fields. With new advances in the subsea technology, it is now possible to move top-side facilities to the sea floor. The two main contributions in this paper are to consider an alternative location for the control valve and to consider how to deal with nonlinearity. This research involved controllability analysis based on a simplified model fitted to experiments, simulations using the OLGA simulator, as well as an experimental study. It was concluded that a control valve close to the riser-base is very suitable for anti-slug control, and its operation range is the same as the top-side valve. However, a subsea choke valve placed at the well-head can not be used for preventing the riser-slugging.
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ECC - Subsea solution for anti-slug control of multiphase risers
2013 European Control Conference (ECC), 2013Co-Authors: Esmaeil Jahanshahi, Sigurd Skogestad, M. LieunghAbstract:A top-side choke valve is usually used as the manipulated variable for anti-slug control of multi-phase risers at Offshore Oil-Fields. With new advances in the subsea technology, it is now possible to move top-side facilities to the sea floor. The two main contributions in this paper are to consider an alternative location for the control valve and to consider how to deal with nonlinearity. This research involved controllability analysis based on a simplified model fitted to experiments, simulations using the OLGA simulator, as well as an experimental study. It was concluded that a control valve close to the riser-base is very suitable for anti-slug control, and its operation range is the same as the top-side valve. However, a subsea choke valve placed at the well-head can not be used for preventing the riser-slugging.
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Comparison between nonlinear model-based controllers and gain-scheduling Internal Model Control based on identified model
52nd IEEE Conference on Decision and Control, 2013Co-Authors: Esmaeil Jahanshahi, Sigurd SkogestadAbstract:Instability and inverse response behaviour make anti-slug control at Offshore Oil-Fields an interesting control problem where a robust solution considering the nonlinearity of the system is required. We tested three control solutions by experiments in this paper. First, we used state-feedback with state estimation by a nonlinear high-gain observer. Secondly, we applied feedback linearization with measured outputs. Finally, we designed gain-scheduling IMC (Internal Model Control) based on linear models identified from closed-loop step test. We compared these three solutions in terms of robustness and their range of operation. The high-gain observer was only applicable by using the top-side pressure measurement in a limited range; it was not stable when using the the subsea pressure measurement in closed loop. The IMC method was more robust against time-delay in the subsea pressure measurement compared to the feedback linearizing controller.
Egil Sunde - One of the best experts on this subject based on the ideXlab platform.
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Microbial analysis of backflowed injection water from a nitrate-treated North Sea Oil reservoir
Journal of Industrial Microbiology & Biotechnology, 2009Co-Authors: Gunhild Bødtker, Kristine Lysnes, Eva Ø. Bjørnestad, Terje Torsvik, Egil SundeAbstract:Reservoir souring in Offshore Oil Fields is caused by hydrogen sulphide (H_2S) produced by sulphate-reducing bacteria (SRB), most often as a consequence of sea water injection. Biocide treatment is commonly used to inhibit SRB, but has now been replaced by nitrate treatment on several North Sea Oil Fields. At the Statfjord field, injection wells from one nitrate-treated reservoir and one biocide-treated reservoir were reversed (backflowed) and sampled for microbial analysis. The two reservoirs have similar properties and share the same pre-nitrate treatment history. A 16S rRNA gene-based community analysis (PCR-DGGE) combined with enrichment culture studies showed that, after 6 months of nitrate injection (0.25 mM NO_3 ^−), heterotrophic and chemolithotrophic nitrate-reducing bacteria (NRB) formed major populations in the nitrate-treated reservoir. The NRB community was able to utilize the same substrates as the SRB community. Compared to the biocide-treated reservoir, the microbial community in the nitrate-treated reservoir was more phylogenetically diverse and able to grow on a wider range of substrates. Enrichment culture studies showed that SRB were present in both reservoirs, but the nitrate-treated reservoir had the least diverse SRB community. Isolation and characterisation of one of the dominant populations observed during nitrate treatment (strain STF-07) showed that heterotrophic denitrifying bacteria affiliated to Terasakiella probably contributed significantly to the inhibition of SRB.
Gunhild Bødtker - One of the best experts on this subject based on the ideXlab platform.
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Microbial analysis of backflowed injection water from a nitrate-treated North Sea Oil reservoir
Journal of Industrial Microbiology & Biotechnology, 2009Co-Authors: Gunhild Bødtker, Kristine Lysnes, Eva Ø. Bjørnestad, Terje Torsvik, Egil SundeAbstract:Reservoir souring in Offshore Oil Fields is caused by hydrogen sulphide (H_2S) produced by sulphate-reducing bacteria (SRB), most often as a consequence of sea water injection. Biocide treatment is commonly used to inhibit SRB, but has now been replaced by nitrate treatment on several North Sea Oil Fields. At the Statfjord field, injection wells from one nitrate-treated reservoir and one biocide-treated reservoir were reversed (backflowed) and sampled for microbial analysis. The two reservoirs have similar properties and share the same pre-nitrate treatment history. A 16S rRNA gene-based community analysis (PCR-DGGE) combined with enrichment culture studies showed that, after 6 months of nitrate injection (0.25 mM NO_3 ^−), heterotrophic and chemolithotrophic nitrate-reducing bacteria (NRB) formed major populations in the nitrate-treated reservoir. The NRB community was able to utilize the same substrates as the SRB community. Compared to the biocide-treated reservoir, the microbial community in the nitrate-treated reservoir was more phylogenetically diverse and able to grow on a wider range of substrates. Enrichment culture studies showed that SRB were present in both reservoirs, but the nitrate-treated reservoir had the least diverse SRB community. Isolation and characterisation of one of the dominant populations observed during nitrate treatment (strain STF-07) showed that heterotrophic denitrifying bacteria affiliated to Terasakiella probably contributed significantly to the inhibition of SRB.
Daniel B Olsen - One of the best experts on this subject based on the ideXlab platform.
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lifecycle energy accounting of three small Offshore Oil Fields
Energies, 2019Co-Authors: David Grassian, Daniel B OlsenAbstract:Small Oil Fields are expected to play an increasingly prominent role in the delivery of global crude Oil production. As such, the Energy Return on Investment (EROI) parameter for three small Offshore Fields are investigated following a well-documented methodology, which is comprised of a “bottom-up” estimate for lifting and drilling energy and a “top-down” estimate for construction energy. EROI is the useable energy output divided by the applied energy input, and in this research, subscripts for “lifting”, “drilling”, and “construction” are used to differentiate the types of input energies accounted for in the EROI ratio. The EROilifting time series data for all three Fields exhibits a decreasing trend with values that range from more than 300 during early life to less than 50 during latter years. The EROilifting parameter appears to follow an exponentially decreasing trend, rather than a linear trend, which is aligned with an exponential decline of production. EROilifting is also found to be inversely proportional to the lifting costs, as calculated in USD/barrel of crude Oil. Lifting costs are found to range from 0.5 dollars per barrel to 4.5 dollars per barrel. The impact of utilizing produced gas is clearly beneficial and can lead to a reduction of lifting costs by as much as 50% when dual fuel generators are employed, and more than 90% when gas driven generators are utilized. Drilling energy is found to decrease as the field ages, due to a reduction in drilling intensity after the initial production wells are drilled. The drilling energy as a percentage of the yearly energy applied is found to range from 3% to 8%. As such, the EROilifting+Drilling value for all three Fields approaches EROilifting as the field life progresses and the drilling intensity decreases. The construction energy is found to range from 25% to 63% of the total applied energy over the life of the field.
