Design of the ROV Dedicated Seafloor Heat Flow Probe

Abstract

As the exploration of the natural gas hydrate is developed towards the target drilling phase, the traditional EWING-type and LISTER-type heat flow probe is unable to meet the needs of fine detection of the seafloor heat flow in the target area of the nature gas hydrate. The ROV (Remotely Operated Vehicle) dedicated seafloor heat flow probe is designed based on the status and operating characteristics of ROV which has been already adopted in China, which is suitable for measuring the large-scale and high-density seafloor in-situ heat flow, analyzing and understanding the fine thermal structure and thermal state of the special geological structure, and focusing on solving seafloor heat flow measurements in local structure. In the ROV dedicated seafloor heat flow probe, a high-precision NTC thermistor is adopted as the sensor, and ADUC845 chip with an internal integration of 24-bit high-resolution A/D converter is selected as the main processor. Furthermore, the ROV (Remotely Operated Vehicle) dedicated seafloor heat flow probe can measure the resistance values of the thermistors in five channels through the measurement mode of DC unbalanced bridge in a way of time sharing, and use STEINHART & HART equation to conduct R-T conversion, thus obtaining a more accurate geothermal gradient curve of the seafloor sediments after correction by the seven-point three-phase data conversion method, of which the measurement accuracy is 0.005℃ and the resolution ratio reaches 0.001℃. And it can also obtain the valuable raw data of the heat flow with the sea trial of the “SeaLion ROV†of Chinese scientific investigation vessel “Ocean VI†and the “Jiaolong HOV (Human-Occupied Vehicles)†of “Xiangyanghong XVI†vessel.