Smart Choke - A Simple and Effective Slug Control Technology to Extend Field Life

Abstract

Slugging in pipeline-riser systems is becoming more common as the petroleum industry matures. Current trends of developing deepwater fields and producing from marginal fields via subsea tie-backs to existing facilities often lead to slugging. Slugging also occurs in fields approaching end of life, due to decreased gas coupled with increased water productions. Slugging is a major problem for offshore operations because it causes large fluctuations in gas and liquid production which may cause platform trips and riser vibrations. These will lead to production deferment, riser integrity/safety issue, and potential abandonment for fields operating near end of life.The most recent slug control technology in Shell is the Smart Choke. This technology utilizes a single control valve which is installed between the riser top and first stage separator. It is an active slug control device which regulates liquid and gas flow by manipulating the control valve opening. Compared to conventional slug management techniques which require large footprints and high capital/operating costs, Smart Choke is compact and cost-efficient.Smart Chokes have been installed in the Gulf of Mexico, Nigeria and Malaysia. The pipelines had large fluctuations in pressure and gas/liquid flowrates due to hydraulically unstable flowline/riser system. The installed Smart Chokes were tested to be effective in suppressing riser-induced slugs and controlling slugs initiated within horizontal pipelines. Deployments to-date has shown for example field life extensions of over one year or production gains of about 5 to 10%. This paper presents the implementation of Smart Choke from feasibility study to site implementation in a Malaysian field. It is the first project that integrates Smart Choke control into a platform control system for easier operation. Field data are presented to demonstrate how Smart Choke has extended the field life through the control of slugs. As a result, the shut-in field which was planned for abandonment could continue production.

Suppression of liquid slugs and phase separation through pipeline bends

“…In these situations, large fluctuations in gas and liquid production may cause high oscillations and uncontrolled vibrations, ultimately leading to production deferral, riser integrity/safety issues, and potential abandonment of fields near their end of life. [ 6 ] Slug elimination and control have been investigated in several studies. [ 7,8 ] Various solutions have been proposed to reduce or eliminate slugging.…”

Venturi Multiphase Flow Measurement based Active Slug Control

“…Based on this principle, the Shell Smart Choke was developed, where the S 3 control algorithm is implemented on a single control valve. However, this solution was also based on controlling the flow rates [12], [13]. Some other contributions on active slug flow control can be found, e.g.…”