2019 AAPG Annual Convention and Exhibition:

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Real-Time Mapping, In-Situ Analysis, and Sampling of Hydrocarbons With Underwater Vehicles

Abstract

Natural seeps occur where oil and gas find their way out of the subsurface to the seafloor. Seeps present an opportunity to obtain geochemical data and use it to de-risk hydrocarbon exploration. Sampling natural seeps is particularly valuable in deep water exploration because the collected geochemical samples provide detailed information on thermal maturity, age, facies, and the organic matter type that formed the hydrocarbons. We present a chemical sensing system for use on underwater vehicles during seep exploration. The system makes calibrated in situ chemical measurements and is capable of real-time three-dimensional mapping of dissolved hydrocarbon plumes, which informs sample collection for later laboratory analyses. The system is calibrated under operating conditions by means of a calibration standard which results in reliable measurements properly adjusted in time and space. When deployed together with multi-beam sonar on an Autonomous Underwater vehicle (AUV) the advantages are twofold. First, seeps can be mapped at 10x-100x greater resolutions than conventional multi-client ship surveys. Second, the chemical sensors enable real-time discrimination of prospective seep sites. The chemical sensing system can also be deployed from an ROV. We discuss the performance of the chemical sensing system during laboratory and field trials.