Grey-Box Modeling of an Offshore Deoiling Hydrocyclone System

The increasing water cut from offshore production wells render optimization of the deoiling process vital for continuous oil and gas production. Hydrocyclones are commonly used as the last stage of the deoiling process and must therefore keep the oil content in the produced water below 30ppm to comply with the local legislation. Optimizing the performance of hydrocyclones is a balance between separation efficiency and reject flow rate. Thus, it is essential to exploit the freedom within the system which may be found by means of analyzing the internal fluid mechanics of the hydrocyclones. This work investigates the establishment of a control-oriented grey-box model of a hydrocyclone as an extension of a previously defined droplet trajectory-based model. The model parameters were estimated using numerical optimization by fitting the model outputs to experimental data. This work proposes a method to estimate how the hydrocyclone pressures are related to its flow rates by means of virtual orifice equations. The experimental results prove that the proposed model is able to estimate the relationship between pressures and flow rates with good accuracy and can be extended in future works to include dynamic properties.