Reproducing slugging oscillations of a real oil well

Meglio, Florent Di; Kaasa, Glenn-Ole; Petit, Nicolas; Alstad, Vidar

doi:10.1109/cdc.2010.5717367

Cited by 12 publications

(15 citation statements)

References 15 publications

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“…The observer gain is designed so that the observer is robust to uncertainties in modeling the nonlinear functions. The structure of the high-gain observer is similar to the one used in [7]: (1), (2) and (4). For the third state equation (f 3 ), we transformed the state into top pressure which is a measurement (y = z 3 andŷ =ẑ 3 ).…”

Section: B High-gain Luenberger Observermentioning

confidence: 99%

“…One may say a observer is not high-gain, because the observer gain is K = 1 [7]. However, it depends on which unit is used for the measurement; for example there is a scaling factor of 10 3 between Pa and kPa for pressure.…”

Section: Introductionmentioning

confidence: 99%

“…A nonlinear Luenberger-type observer which uses only topside pressure to reproduce oscillations of the riserslugging instability was proposed in [7], and then used for anti-slug control of a pipeline-riser system in experiments [8]. This observer was designed based on a three-state simplified model of the system [9].…”

Section: Introductionmentioning

confidence: 99%

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Anti-slug control experiments using nonlinear observers

Jahanshahi

Skogestad

Grøtli

2013

2013 American Control Conference

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Abstract-To prevent slug-flow on offshore oil production units, controlling a subsea pressure is the recommended solution. However, the subsea pressure is not often available as a measurement. The top-side pressure is usually measured but it is difficult to use for stabilizing control, because of its Right Half-Plane zero dynamics combined with nonlinearity. We have used the top-side pressure as measurement for different observers to estimate state variables of the system, and then used the estimated states for control. This scheme was tested in experiments using three types of observers. A simple Luenberger observer with a large gain was found to be more robust than the standard Unscented Kalman Filter (UKF). We modified the UKF to a Fast UKF for time-scale separation of the closed-loop system. The resulting observer was robust, also less sensitive to measurement noise compared to the simple Luenberger observer when measuring the top-side pressure. Surprisingly, the nonlinear observers were not able to work in closed-loop when the subsea pressure was used as the measurement. On the other hand, a linear observer worked very well for this case with a larger operating range compared to that of the top-side pressure.

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Section: B High-gain Luenberger Observermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Anti-slug control experiments using nonlinear observers

Jahanshahi

Skogestad

Grøtli

2013

2013 American Control Conference

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“…It has been discovered that casing-heading instability is not the only source of unstable well production, but it has been observed that it is the most significant factor for gaslifted oil-wells [2], [10]. some investigation about the gas-lift instability can be found in [3], [4], [5] and references therein, and the control of this instability can be found in [6], [7], [10]. In many practical situations at offshore platforms, the slugging problem is to handled in a manual control manner, which is definitely not cost-effective nor highly reliable.…”

Section: Introductionmentioning

confidence: 98%

Emulation and control of slugging flows in a gas-lifted offshore oil production well through a lab-sized facility

Jepsen¹,

Hansen²,

Maï³

et al. 2013

2013 IEEE International Conference on Control Applications (CCA)

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In the oil and gas industry, the gas-lift assist approach is often used in the production wells when the reservoir pressure is insufficient to ensure cost-effective production. However the side-effect of this approach is the often occurrence of regular/irregular large oscillations of the production flow and pressures in the production well system, which is referred to as the slugging flow problem. This instability is mainly due to the casing-heading mechanism. This work investigates the possibility to use a feedback control for stabilizing the production operation without sacrificing the production capability. A labsized production well system is constructed in an economic manner. Afterwards, a simple nonlinear model is derived according to physical principles and then verified with the experimental facility. A observer-based state feedback control is designed to handle the potential slugging problem. The developed controller manipulates the openness degree of the production choke based on feedback a number of pressure measurements. The current simulation results showed satisfactory control performances by stabilizing the system operation at some relatively large production rate which is originally open-loop unstable.

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“…Di Meglio et al (2010a) proposed a partially linearizing feedback controller that uses the mass of liquid in the riser for state feedback. Di Meglio et al (2010b) used a simple nonlinear Luenberger-type observer to estimate the state variable needed for the controller. However, the separation principle does not hold for nonlinear systems in general, and the closed-loop observer/controller is not 1 Corresponding author guaranteed to be stable for all conditions.…”

Section: Introductionmentioning

confidence: 99%

Nonlinear model-based control of two-phase flow in risers by feedback linearization

Jahanshahi

Skogestad

Grøtli

2013

IFAC Proceedings Volumes

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Active control of the production choke valve is the recommended solution to prevent severe slugging flow conditions at offshore oilfields. The slugging flow constitutes an unstable and highly nonlinear system; the gain of the system changes drastically for different operating points. Although PI and PID controllers are the most widely used controllers in the industry, they need to be re-tuned for different operating conditions. The focus of this paper is to design a model-based nonlinear controller in order to counteract nonlinearities of the system. Feedback linearization based on the riser-base pressure and the topside pressure was used for the control design. Stability and convergence of the closed-loop system was verified in theory as well as by experiments on a test rig.

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Reproducing slugging oscillations of a real oil well

Cited by 12 publications

References 15 publications

Anti-slug control experiments using nonlinear observers

Anti-slug control experiments using nonlinear observers

Emulation and control of slugging flows in a gas-lifted offshore oil production well through a lab-sized facility

Nonlinear model-based control of two-phase flow in risers by feedback linearization

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