Overview of Conventional Sand Jetting System and Improved Cyclonic Jetting Nozzle for Oil and Gas Separator

INTRODUCTION

Conventional sand jetting system embarks on nozzle spraying technique for sand fluidization. This method requires high fluid velocity at nozzle to transform deposited sand into slurry before it is being pushed towards discharge pipe at bottom of separator. High turbulence condition is generated nearby nozzle area that will propagate to oil and water separation layer on top of the vessel. Cyclonic jetting nozzle serves as superior solution to conventional sand jetting system due to its ability to maintain laminar parting of oil and water on top of separator. It creates circular vortex which extends horizontally to approximately 1 m in radius from nozzle, so that fluidized sand is drawn to the centre of vortex due to pressure difference between vessel and slurry discharge exit. By doing so, the system prevents mixing of oil and water separation while minimizing turbulence at top section. Besides, fluid momentum is preserved in such a way that lower pressure drop across the system is attained as compared to conservative sand jetting system, hence motive fluid usage is reduced significantly.

DESCRIPTION

The working principle of a conventional sand jetting system involves spray medium like water being fed to a series of spaced-out sprat nozzles fitted along the vessel over the sludge retention baffle, as shown in Fig 1.

Working principle of conventional sand jetting system
Fig.1. Working principle of conventional sand jetting system

Pressurized water is introduced to facilitate movement of deposited solids to the bottom and centre out a nozzle where a pan is typically installed to prevent blockage of exit nozzle [1][2]. An alternative is that it promotes the fluidization of deposited solids along with the facilitation of particulate hydrodynamic transport out of the unit along the designated pipelines[3].

The working principle of a cyclonic jetting nozzle, however, involves motive fluid being pushed towards converging swirl chamber that acts as fluid accelerator. Swirl chamber will spin the fluid inwards and release high velocity fluid at nozzle outlet nearby suction gate. Though a cyclonic jetting nozzle appears to be more efficient as compared to traditional sand jetting system, it lacks in conserving fluid momentum inside converging swirl chamber. This is a result of a steep velocity direction alteration across swirl chamber.

A study has conducted to improve pressure loses at swirl chamber due to steep change in motive flow direction. The improvement includes expanding the  swirl chamber for optimising fluid usage, and a custom profile at outlet is introduced to reduce flowrate at the outer section, so that more fluid can be directed towards the inner section of separator. As a result, it has shown that the improved cyclonic jetting nozzle is able to provide enhanced performance in area coverage of 1.2 m as compared to 1.0 m covered by conventional cyclonic jetting nozzle which translates to 20% increase in area coverage using the same motive flowrate. By incorporating swirl cone inside diverging swirl chamber, end cap at suction gate and custom nozzle opening profile delivers superior sand removal process as compared to conventional cyclonic nozzle. Those modifications have successfully offer higher suction velocity, which translates to larger area covered with less and residue at tank surface relative to traditional nozzle design. Present nozzle affords high potential in significant cost reduction strategy by means of reduced number of nozzles required per manifold and less motive fluid needed.

References

[1] “Sand Jet System – Finepac Structure.” http://finepacindia.in/jet-systems.html (accessed Dec. 14, 2021)

[2] C. H. Rawlins and I. I. Wang, “Design and Installation of a SandSeparation and -Handling System for a Gulf of Mexico Oil Production Facility,” SPE Prod. Facil., pp. 134–140, 2001, Accessed: Dec. 14, 2021. [Online]. Available: https://eprocess-tech.com/wpcontent/uploads/2016/10/DesignAndInstallationOfASand.pdf

[3] C. H. Rawlins and E. Technologies, “SPE 166118-MS Design of a Cyclonic Solids Jetting Device and Slurry Transport System for Production Systems.”

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