Innovative In-Vessel Sand Removal Solution in Driving Cost Down for Brownfield Sand Management
Authors: Myo Thant Maung Maung , Che Daud M Faizal , Mohd. Sallehud-Din M Taufik , Tuan Mahmud Tuan M Yusoff , T Aziz Tengku Zulfadzly , Kayat Zainab 
Published: February 2022

Sand problem is massive and widespread in oil and gas industry including unconventional reservoirs. In most brownfields production system, separators are where sand accumulate in large quantities. However, not all vessels are equipped with online vessel desanding system hence requiring shutdown to manually remove the accumulated sand. This paper aims to present the development and implementation of an innovative online vessel desanding solution to sustain production whilst managing sand issues in driving cost down at one of PETRONAS offshore facilities.

Internals in vessels have a significant role in capturing sand and its deposition capacity. Opportunities for new and novel vessel internal modification can be developed which promotes sand deposition/retention within the vessel based on CFD. The first step requires analytical study based on Stoke’s terminal velocity approach to identify constraints to deposition and narrow down potential design concepts. Eulerian - Lagrangian coupled-modelling was used to evaluate sand retention performance of the proposed concept against existing vessel internal configuration. Subsequently sand deposition analysis is conducted to estimate vessel cleaning frequency. Frequent monitoring of in-vessel sand retention performance before and after need to be carried out to validate its adequacy.

The use of internally developed modelling on sand deposition and CFD analysis resulted in an in-vessel desanding concept which resulted in feasible option compared to depending on an existing standpipe. The new design showed a good sand with retention 91% of cumulative weight retained with cut-off size of 100 micron with adequate accumulation capacity. The design also indicated sand accumulation will not disrupt the liquid level control system as there will be no blockage at the tapping point, which is located downstream of the weir. It had increased the operator response time for process control of the existing separator which is beneficial for operations. Vessel maintenance and cleaning activity is relatively easier as access to dry area is available. The solution was implemented in one of the fields in Malaysia with demonstrated significant increase in amount of sand collected within vessel which has reduced sand carry-over at liquid outlet. The spin off benefits was also seen on the Crude Oil Transfer Pump (COTP) availability which has improved from 96% to 98% and a Meantime Between Failures (MTBF) of COTP has improved by 50%.

Low cost and innovative approach is a promising solution for the ageing fields with excessive solids production. New proposed solution is able to maintain the current separation efficiency under various multiphase-flow conditions. The most important step in having a successful implementation is to have a systematic and effective sand sampling to provide accurate measure of the total sand quantity produced from each well and its particle size distribution.