ChITA: Chain Induced Trench Alarm – A Low Energy Early Warning Concept for Mooring Integrity

Abstract Mooring line touchdown zones on deepwater floating production systems are subjected to repeated cyclic interaction between the chain and seabed. Over time, this interaction leads to progressive seabed excavation and trench formation along the chain path. As trenching propagates toward the anchor foundation, such as suction piles or driven piles, the resulting loss of lateral and vertical soil confinement can significantly reduce anchor holding capacity. If left undetected, this degradation may lead to unacceptable safety margins, necessitating costly remedial interventions, operational downtime, or in extreme cases, full mooring system replacement. This paper introduces ChITA (Chain Induced Trench Alarm), a retrofit-friendly, low-energy early-warning monitoring concept designed to detect and alert operators to potentially critical trench development before anchor limit states are reached. ChITA operates by monitoring site-specific trench geometry and chain excursion characteristics and comparing them against calibrated thresholds derived from anchor capacity and geotechnical performance criteria. When these thresholds are exceeded, indicating elevated risk to anchor integrity, the system autonomously triggers an alarm. Upon activation, ChITA communicates the alert through SEND (Subsea Emergency Notification Delivery), a generic satellite-enabled data transmission architecture. SEND allows rapid and reliable delivery of alarm notifications from subsea assets to topside or onshore systems without the need for permanent umbilicals or high-bandwidth communication infrastructure, making it particularly suited for brownfield and deepwater applications. Currently, trench evolution and mooring integrity are typically assessed through periodic Remotely Operated Vehicle (ROV) inspections, which are episodic, expensive, and provide limited temporal resolution. By contrast, ChITA offers a cost-effective, continuous, and near–real-time monitoring solution that enhances situational awareness and enables proactive intervention. The proposed system has the potential to significantly reduce inspection costs, mitigate mooring integrity risks, and improve asset reliability, offering broad applicability and value to the global offshore industry.