Solutions Oil & gas

Offshore and onshore oil- and gas production facilities are highly influenced by operational transients and dynamic disturbances. Despite a large number of plant measurements, a major challenge is to measure changes in flow and composition, and thus to predict the future effects of them. As a consequence of this, and in order to ensure high regularity, upstream choke positions and downstream PID controller setpoints for levels, pressures and temperatures are typically fixed at conservative and “comfortable” values.

Cybernetica has developed a dynamic model library which is tailor-made for on-line estimation (soft sensing), control, optimization and short-term predictions. In combinations with our tool for Nonlinear Model Predictive Control, Cybernetica CENIT, we are able to develop advanced, multivariable control solutions that pushes the production against the real physical plant constraints. This is achieved by continuously manipulating a set of free variables, like choke positions and PID controller setpoints. Our dynamic models are corrected online from real, dynamic plant measurements in order to avoid model degradation and to maintain reliable plant predictions.

 

Figure2By introducing solutions from Cybernetica, the plant throughput or production rate may be increased by several percentages. In addition, direct control of product quality, reduced energy consumption and a minimum of emissions may be obtained.

Experience

Cybernetica has extensive experience in implementing MPC on onshore gas terminals. We have also tested applications for offshore facilities. This work has been performed in close cooperation with Statoil (Norway).

We have been highly involved in research projects were modeling, control and optimization of offshore production plants has been addressed. Some of the results have been approved for technological readiness levels that allows for pilot installations. Research projects have been run together with Statoil and Petrobras (Brazil).


Case Handling of liquid slugs – Avoid reduction in production

Slugging in wells, pipelines and risers represents a major type of plant disturbance for several offshore facilities. The result will sometimes be throttled production from these specific sources, in order to avoid separator level alarms, with possible plant shut-down as a consequence. A significant production potential may therefore be lost. Improved slug handling is obtained by coordinated actions of several liquid level controllers (LICs).

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