摘要：

邻井低频分布式光纤声波传感监测作为近年来兴起的压裂监测技术，是实现压裂裂缝精细诊断的有效手段。为使业界进一步了解低频分布式光纤声波传感技术在水力压裂裂缝监测中的研究进展，推动光纤压裂监测现场规模化应用，本文从分布式光纤声波传感技术原理出发，简要阐述了分布式光纤声波传感机理及井中布设方式，系统总结了该技术在数值模拟、物理模拟和水力压裂现场应用方面的研究进展，最后提出了未来低频分布式光纤声波传感技术的发展方向。研究结果表明：①水力压裂低频光纤声波传感技术具有精度高，实时性强的优点，正逐渐应用于现场压裂监测，并得到了国内外学者的广泛关注。一次性光纤具有部署简单、成本低、占用空间小和性价比高等优点，未来有望成为邻井压裂监测的主要方式。如何有效降低光纤滑移效应对光纤应变响应的影响对于提高光纤监测的应变数据质量具有重要意义。②正演模拟主要通过光纤应变场模拟与实际监测数据进行对比分析，定性分析光纤应变规律，从而建立不同裂缝扩展类型与光纤应变规律的对应关系，解释邻井水力裂缝形态和扩展模式，目前应变解释模型主要考虑水平邻井和垂直邻井两种监测方法，尚无法表征应力干扰引起的裂缝偏转，与实际现场监测结果存在一定差距，未来亟需建立考虑应力干扰和流量分配的多裂缝复杂正演模型，为现场光纤数据解释提供指导。③反演模拟主要通过位移不连续法构建裂缝扩展模型求解裂缝尺寸，目前主要求解方法包括最小二乘法、Picard迭代、L-M方法和DRAM算法，但均无法同时反演3个方向上的裂缝几何参数。未来反演模拟的研究需要集中于求解算法的优化，如何更好地降低多解性影响将是后续算法优化的主要攻关方向。④物理模拟主要依托基于光频域反射(OFDR)技术的分布式光纤解调器与真三轴压裂设备相结合开展裂缝监测实验，试验参数设置尚无法完全贴合现场实际情况，分布式光纤在不同岩石试样中的布设方式以及光纤试验数据解释是未来室内物理模拟研究的主要攻关方向。结论认为，邻井光纤监测对于压裂裂缝尺寸解释具有显著的应用潜力，未来有望成为解决非常规资源开发瓶颈问题的关键技术。

关键词: 水力压裂, 低频分布式声学传感, 邻井监测, 裂缝监测, 研究进展

Abstract:

Low-frequency distributed acoustic sensing in adjacent wells, a recently emerged fracturing monitoring technology, enables detailed diagnosis of hydraulic fractures. To promote industry understanding of recent advances in low-frequency distributed acoustic sensing technology for hydraulic fracture monitoring and facilitate its large-scale field application, this paper begins with the principles of distributed acoustic sensing. It briefly explains the sensing mechanism and well deployment methods, systematically summarizes research progress in numerical simulation, physical modeling, and field applications during hydraulic fracturing, and concludes by outlining future development directions for low-frequency distributed acoustic sensing technology. Research findings indicate that: ①Low-frequency fiber-optic acoustic sensing technology for hydraulic fracturing delivers high precision and real-time monitoring capabilities. This technology is increasingly being deployed for field fracture monitoring and has garnered significant attention from researchers worldwide. Disposable fiber optic systems offer distinct advantages including simplified deployment, low cost, compact footprint, and excellent value proposition. They represent a promising primary solution for future offset-well fracturing monitoring. Mitigating fiber slippage artifacts’ impact on strain response is therefore paramount for enhancing strain data fidelity in fiber optic sensing applications. ②Forward modeling primarily involves comparative analysis of simulated fiber optic strain fields with actual monitoring data to qualitatively characterize strain patterns. This establishes correlations between distinct fracture propagation types and their corresponding strain signatures, enabling interpretation of hydraulic fracture geometry and growth modes in offset wells. Current strain interpretation models predominantly consider two monitoring configurations: horizontal and vertical offset wells. However, these models fail to characterize fracture deflection induced by stress shadowing, resulting in discrepancies with field monitoring observations. Future work urgently requires developing sophisticated multi-fracture forward models that incorporate stress interference effects and fluid partitioning mechanisms to provide reliable guidance for field data interpretation. ③Inversion modeling primarily utilizes the Displacement Discontinuity Method(DDM) to construct fracture propagation models and solve for fracture dimensions. Current solution approaches include Least Squares, Picard iteration, Levenberg-Marquardt (L-M) method, and the Delayed Rejection Adaptive Metropolis (DRAM) algorithm. However, none can simultaneously invert fracture geometric parameters in all three spatial dimensions. Future inversion research must focus on optimizing solution algorithms, where effectively mitigating the impact of solution non-uniqueness will be the primary research focus for subsequent algorithmic enhancements. ④Physical simulation experiments primarily integrate distributed optical fiber interrogators based on Optical Frequency Domain Reflectometry (OFDR) technology with True Triaxial fracturing apparatuses to monitor fracture propagation. However, current experimental parameter configurations still fall short of fully replicating field conditions. Optimizing fiber deployment methodologies across diverse rock specimens and advancing the interpretation of laboratory-derived fiber optic data represent critical research priorities for future physical simulation studies. The study concludes that offset-well fiber optic monitoring demonstrates significant potential for interpreting hydraulic fracture dimensions. This technology holds considerable promise as a key enabling technology for addressing critical bottlenecks in unconventional resource development.

Key words: hydraulic fracturing, low-frequency distributed acoustic sensing, adjacent well monitoring, fracturing monitoring, research progress

中图分类号: 

• TE319

• O439