DAS技术在油气地球物理中的应用综述

Application review of DAS technology in oil and gas geophysics

光纤分布式声波传感技术(DAS)基于相位敏感光时域反射,是一种利用光纤后向瑞利散射干涉效应实现声波信号连续分布式探测的新型传感技术.在油气勘探开发领域,近年来在井中VSP、地表地震采集、时延或永久油藏监测、水力压裂监测等方面开展了试验和应用,取得了初步的成功.相比常规地面检波器及井中检波器,DAS技术具有低成本、高效率、密集采样、资料品质不低于传统地震检波器等优势.但DAS技术的局限性在于数据信噪比受光纤布设方式影响、单分量采集、保真距离有限.在综合分析的基础上,展望DAS技术未来发展方向:(1)螺旋缠绕技术等多分量DAS技术的发展及实用化和工业化,以及新型光纤电缆的发展,将大幅度地提高光纤的灵敏度和动态范围,DAS将逐渐克服其局限性.(2)DAS解调技术的发展和光纤采集方式的优化,包括新型采集观测系统、光纤与地层耦合技术等,以及针对性处理、成像技术发展将进一步提高DAS数据的信噪比和成像质量.(3)由于DAS具有成本低、采样率高等优点以及未来DAS技术在提高信噪比方面的进展,DAS技术在油气地球物理技术领域的应用前景将更广阔.

Fiber optic Distributed Acoustic Sensing(DAS), based on phase-sensitive optical time-domain reflectometry, is a novel sensing technology that can continuously and distributedly detect acoustic signals by means of Rayleigh backscattering interference effect. In recent years, in the field of oil and gas exploration and exploitation, DAS have been tested and applied in many aspects,such as borehole VSP, surface seismic acquisition, 4 D or permanent reservoir monitoring, hydraulic fracturing monitoring and so on, and early success have been achieved. Compared with conventional surface geophone and borehole geophone, DAS technology has the advantages of low cost, high efficiency, dense sampling and data quality not lower than traditional geophone, etc. However, the limitations of DAS technology lie in the S/N of DAS data is affected by the way of optical fiber installation, single component acquisition and limited fidelity distance. On the basis of the comprehensive analysis, the future development direction of DAS technology is predicted.Firstly,the development,practicability, and industrialization of multi-component DAS technology, such as helically wound technology, as well as the development of new optical fiber cable, will greatly improve the sensitivity and dynamic range of optical fiber, thus DAS will gradually overcome its limitations. Secondly, development of DAS interrogation technology and optimization of acquisition method, including new type of acquisition geometry, optical fiber and formation coupling technology, and development of targeted processing and imaging technology will further improve the signal-to-noise ratio and imaging quality of DAS data. Thirdly, due to the advantages such as low cost and high sampling rate and so on, and progress in improving the signal-to-noise ratio in the future, DAS technology will be more extensively applied in the field of oil and gas geophysics, providing technical support for optimizing exploration and production decisions and increasing oil and gas recovery.