(18a) An Innovative Advanced Control Solution for Slug Mitigation

Sanjay Sharma and Ravi Nath

Honeywell Process Solutions

Houston, TX

Paper to be presented at the

2016 AIChE Spring Meeting

April 10 - 14, 2016

ABSTRACT

In Offshore Oil production processes, production from oil wells comprising a mixture of oil, water and gas flows from the subsea wells to the surface Separators. Often, the gas phase separates from the liquid (oil and water) phase as production flows from the wellhead to the Separators.  This separation of phases can cause an undesirable operating condition when production flow becomes discontinuous with periods of large volume of liquid phase followed by periods of predominantly gas phase.  This phenomenon is called slugging and causes the liquid flow into the Separators to swing significantly.  Slugging is disruptive as it can lead to unstable operation of the downstream process and can sometimes cause flaring incidences or shutdown of the production process.  

Traditionally, PID controllers are employed to maintain the oil and water phase levels in the separators.  Since PID algorithm is oblivious to the operating high and low limits, these controllers are tuned very tightly to ensure that the level remains within safe limits at all times.  Doing so however propagates the fluctuations in oil flow to downstream process which is not desirable. 

A solution that is sometimes employed to minimize slugging is to monitor the process operating conditions and manipulate the separator inlet choke as soon as slugging is detected.  Although such strategy may mitigate slugging, it also has the undesirable side effect of reducing production. 

In this paper, an innovative advanced control solution that effectively mitigates slugging is presented.  The proposed solution employs a Honeywell patented, non-linear, control technology to maximize the utilization of the surge capacity in the Separators so as to reduce fluctuations in the oil flow to downstream process.  A case study for an operating facility is presented that reduces oil flow variance by 80% without curtailing production.

KEYWORDS: Slug Mitigation; Advanced Process Control, Non-linear Control.