水下机器人在深水OBN地震采集中的应用

海上地震采集时采用传统的海面投放方式布放深水海底节点(OBN)时点位偏差较大,无法满足基本的勘探精度要求,因此近年来水下机器人(ROV)被引入到海上地震采集行业。结合非洲东部某近岛海域OBN采集实例,讨论了ROV在深水地震采集应用中的主要环节,包括动态定位船和ROV系统构成及原理,ROV系统在OBN采集节点布放及回收时的质量检测、参数校准方法、深水声波定位方法、点位精度评价方法、实际布放回收效率等。利用初至波二次定位技术,对用ROV布放OBN的坐标精度进行了验证,结果表明ROV可获得较传统海面投放方式精度更高且点位偏移量更稳定的布放效果,但布放及回收效率大大降低。研究结果为ROV在深海或复杂海域OBN地震采集的进一步研究与应用提供了有价值的定量技术评价指标。

In traditional deep-ocean seismic acquisition,the ocean bottom node (OBN) is placed on the sea floor.Thus,a large deviation from the receiver point can occur.In recent years,remotely operated vehicles (ROVs) have been used for deep-ocean OBN seismic acquisition.Here,taking an OBN acquisition from an offshore area in East Africa as an example,the main steps of ROV utilization in deep-ocean seismic acquisition were discussed,namely:the structure and operation procedures of the dynamic positioning (DP) and ROV system,the quality detection and parameter calibration method,the deep-ocean acoustic positioning method,the positional accuracy evaluation,and the actual distribution and reclaiming efficiency during OBN acquisition node placement and reclaiming using the ROV system.The coordinate accuracy of OBN locations deployed by ROV was verified using first-break positioning technology.The results showed that the ROV deployment method can achieve better position accuracy than the traditional technique;however,the deployment and reclaiming efficiencies were greatly reduced.No obvious difference was observed between the ROV coordinates and the first-break positioning results based on single-shot gathers;however,a small difference between the deployment and pick-up locations was observed.This study provides a reliable reference for the quantitative technical evaluation of the application of ROVs in deep-ocean OBN seismic acquisition.