Abstract

We developed a system, whose skills find application in different fields related to O&G offshore activities. These applications comprise the characterization and mapping of light and heavy hydrocarbons at the sea bottom. Therefore, the system can contribute to methane hydrates/shallow gas detection that constitute a geological risk (geohazard) for the O&G activities and contribute significantly to the phenomenon of global warming. On the other hand, the mapping of heavy hydrocarbons, which are the scarcely biodegradable residue of oil spills, can be useful for determining an environmental background before undertaking any new O&G activity. The applications of the system, however, are not limited to environmental assessments. It also allows the acquisition of useful data for exploration activities. Sea bottom geochemical surveys (determination of natural seepages of hydrocarbons of thermogenic origin) prove to be more precise, increasing sampling density, and with a lower environmental impact than the standard approach, that requires sea bottom piston/gravity cores. Together with real-time measurements, the system can collect interstitial water samples to be analysed in laboratory.

Introduction

This work is based on a well-established Eni's technology: the Clean Sea platform (Ref. 1 and references therein cited).

In the recent years Eni developed an innovative submarine robotic technology, called "Clean-Sea", which performs monitoring and inspection of offshore O&G plants, in a completely automatic manner.

Clean-Sea is based on the use of a commercial autonomous submarine vehicle or AUV (Autonomous Underwater Vehicle), equipped with a modular system of instrumented devices (sensors, samplers, analyzers), interchangeable according to the specific missions to be performed, able to automatically carry out the real-time measurements of specific selected parameters.

The distinctive feature of the system is its "intelligent" behavior, that is its autonomous ability to modify, in real time, the pre-set mission, based on the data actually acquired. This reactive behavior allows it to concentrate the measurements in the vicinity of any anomaly present in the marine environment, in order to obtain the best accuracy in detecting both the position of the anomaly and its chemical-physical characteristics.

It is therefore a relatively low-cost, hybrid, modular, robust system with limited logistical needs.

It already worked in Oil & Gas facilities such as offshore Norway, Caspian Sea, Adriatic Sea, Ionian Sea, Sicily Channel, Eastern Mediterranean.

It works up to 3000 m water depth, currently it has been tested up to 1150 m.

Various types of support vessels have been used, in terms of size and rental costs (tugs, icebreakers).

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