Learning control for riser-slug elimination and production-rate optimization for an offshore oil and gas production process

Abstract

Slugging flow in the offshore oil & gas production attracts lot of attention due to it's limitation of production rate, periodic overload on processing facilities, and even direct cause of emergency shutdown. This work aims at two correlated objectives: (i) Preventing slugging flow; and meanwhile, (ii) maximizing the production rate at the riser of an offshore production platform, by manipulating a topside choke valve through a learning switching model-free PID controller. The results show good steady-state performance, though a long settling time due to the unknown reference for no slugging flow.

Comparison of Model-Based Control Solutions for Severe Riser-Induced Slugs

“…The slug testing facility is an extension of the facility examined in [11,18]. The new testing facility can be observed in Figure 1.…”

“…The pipeline-riser dimensions can be found in Table 1. The pressure and flow measurement uncertainties have been reduced by installing new equipment in a narrower range than in [11,18], such that the pressure measurement uncertainty now is 0.01 bar and the flow measurement uncertainty now is 5.56 × 10 −4 kg/s. However, it has to be noted that the multi-phase flow transmitters are more uncertain the more gas is present in the pipeline, as they are measured by Coriolis flow meters.…”

“…Re r is obtained from a calculation similar to Equation (8). Even though the fiction coefficients can be calculated in different ways, Equations (7) and (11) are applied, respectively, because the results were closer to the data from the testing facility.…”

“…The value of P t,v will vary further from P t the longer the topside choke valve is located from the riser top. The friction for P t, f is calculated similar to the friction Equation (11). Note that P t,v is not considered a model output similar to P t , but is used for improving the model accuracy for (another output) ω mix,out .…”

“…Re r (11) where is the roughness of the riser, Re r is the Reynolds number of the fluid mixture in the riser, and D r is the diameter of the riser. Re r is obtained from a calculation similar to Equation (8).…”