Krishnamoorthy, Dinesh,
Jahanshahi, Esmaeil and Skogestad, Sigurd. Gas-lift
Optimization by Controlling Marginal Gas-Oil Ratio using Transient Measurements
Published in IFAC-PapersOnLine 51 (8), 19-24
(IFAC Workshop on Automatic control in offshore oil and gas production)
Abstract: This
paper presents the application of a steady-state gradient control using
transient measurements to a gas-lift optimization problem. Optimal operation of
a gas-lifted field involves controlling the marginal gas-oil ratio (mGOR), which is the steady-state gradient of the oil rate
with respect to the gas lift rate. In this paper, we apply a novel method to
estimate the marginal GOR online using a dynamic model and transient
measurements, without the need for additional perturbation. The proposed method
is based on linearizing the dynamic model around the
current operating point to estimate the marginal GOR, which is then controlled
using simple feedback controllers to achieve optimal operation. In case of
disturbances, the proposed method is able to adjust fast to the new optimal
point, without the need to solve computationally expensive optimization
problems. By using transient measurements, it does not need to wait for the
process to reach steady-state to update the model. The
proposed method was tested in simulations and was
shown to provide similar performance as an economic MPC.
This
paper won the ABB Best Student Paper Award.