HORUS Towards a Permanent Monitoring of Underwater Geohazards

摘要

Geohazards can significantly affect the underwater developments and regularly, there is no possibility to avoid tornbe exposed to those geohazards. In such a case, mitigations are usually designed and implemented to limit thernconsequences of the geohazards. They rely on our understanding of geohazards, our ability to model theirrnbehavior as a function of time, and our capability to predict any possible evolution during the field life. It is the aimrnof TOTAL effort over the past 20 years.rnOne way of improving our knowledge is to develop long-term monitoring systems for critical areas. Inspired byrnscientific sub-sea observatories for natural hazards, TOTAL is developing a monitoring station called HORUST ,rnfor Hazards Observatory for Risk analysis by Underwater System, specifically dedicated to geo-hazards forrnindustrial applications.rnThis station can be equipped with a variable but multi-sensors payload depending on the type of geohazards thatrnaffect the area. Among the different possibility of permanent in-situ measurements, pore pressure, temperature,rngas content, microseismicity and seabed deformations are considered. These parameters will provide earlyrnwarnings for potential slope instabilities, gas escapes, modification of the soil properties, or any evolution of therngeological features.rnThis cabled station is connected to the production facilities where data are recorded and real time preprocessedrnin order to detect anomalies, and possibly, to raise alarms. If the parameter monitoring seems relatively easy,rndata management and data processing are more of concern: alarm levels need to be associated to reliablernindicators. Multi parameter cross-correlation and comparison to pre-defined "normal" thresholds is part of thernpreprocessing that is automatically performed offshore. The station is designed to facilitate maintenance andrnsensor replacement by an ROV. A connecting/disconnecting rack is available for the installation of newrnequipment. Additional battery pack can also be set on the structure for a short-term autonomous use inrnexploration areas.rnThis monitoring concept is currently under development in Nigeria.