A Major Offshore Trial of a Free-Standing Mid-Depth BOP Drilling Riser System Event: A Major Offshore Trial of a Free-Standing Mid-Depth BOP Drilling Riser System Date: May 2015 Author: F. Lim, H. Zhang, L. Ching - 2H, Y. Guo, S. Ji, C. Tang - COSL A major offshore trial of a mid-depth BOP drilling riser system was conducted in 2009 by COSL in 470m water depth of the South China Sea. The objective of the trial was to demonstrate the feasibility of using a shallow water drilling platform to drill in depths which would otherwise be beyond its reach. A free-standing tieback string supported by a buoyancy unit presented an ‘artificial seabed’ and wellhead at an elevation which the platform’s existing drilling riser with its subsea BOP could connect to and drill through. The trial mobilised a 3rd generation semi-submersible drilling platform Nanhai 5, its drilling riser and subsea BOP, a test tieback string, and a fully commissioned buoyancy unit. The full offshore transportation and installation sequences were executed for Nanhai 5 to successfully connect to a mock-up ‘real seabed’ wellhead via the afore-mentioned set-up. The novel components in the system, particularly the tieback string and buoyancy unit, were instrumented and monitored to study their motion behaviour for correlation against analytical predictions. In the present day ultra-deepwater drilling world, the interests for such a depth-extending system have revived, in the context of the fleet of modern 3000m-rated drilling platforms wanting to go beyond 3000m water depth. The lessons learnt from the COSL trial bear significant relevance for designing future systems. This paper describes the trial, its design and planning, certain problems encountered and some recorded system behaviour. If you would like a copy of this technical paper register to download it (pop-up form). Back to All Technical Papers Services Deepwater Production Systems Riser Concept Engineering Steel Catenary Risers Top Tensioned Risers Hybrid Risers Flexible Pipes & Risers Composite Risers Subsea Flowlines & Jumpers Subsea Umbilicals System Verification & CVA Drilling, Completion & Workover Drilling Risers Drilling Riser Management Subsea Completion & Workover Risers Subsea Wellheads & Conductors Offshore Platform Conductors Platform Well Integrity & Life Extension Well Engineering Well Plug & Abandonment Integrity, Life Extension & Monitoring Riser Integrity & Life Extension Subsea Wellhead System & Life Extension Machine Learning for Riser Engineering Riser System Digital Twin Riser Monitoring System Engineering Riser Inspection, Maintenance & Repair Subsea Incident Engineering Fracture Mechanics and ECA Minimum Facility Platforms Conductor Supported Wellhead Platforms & CoSMOS Monopile Wellhead Platforms Exploration to Early Production Systems Structural Engineering Services Installation Engineering Decommissioning Engineering Riser Delivery Management Component Detailed Design Mechanical Connectors Systems & Qualification Testing Offshore Renewables & Alternative Resources Fixed Offshore Wind Floating Offshore Wind Deep Sea Mining Get the latest riser insights! Receive our riser news, published papers and blog posts in your inbox monthly. *