扫描频率激振下振动器-大地耦合振动与频宽拓展研究

The vibroseis is the main equipment for oil and gas exploration, which plays an important role in the exploration of deep, ultra-deep and unconventional oil and gas resources. Due to the lack of excitation precision and applicable bandwidth of the vibrator under the excitation of sweep frequency, the exploration signal has the disadvantages of distortion, insufficient low-frequency contents and misalignment of ground force at high frequency, which seriously limit the exploration capability of the vibroseis. In this research, the vibrator-ground coupling vibration model under the excitation of sweep frequency will be established, based on constructing the pressure distribution equation of the baseplate bottom surface and proposing dynamic stiffness, dynamic damping and captured ground to describe the nonlinear interaction between the vibrator and the ground. The establishment of the model will break through the bandwidth limitation of the vibrator excitation model and reveal the vibrator-ground coupling vibration law. Based on the study of the ground force and the downgoing energy, the influence law of coupling system parameters on excitation performance will be investigated, the key parameters of coupling system will be obtained, and the excitation accuracy will be improved. With the goal of improving the ground force, the downgoing energy and the octave of bandwidth, the optimization model of vibrator bandwidth extension with multiple parameters and multiple objectives will be established. With the study of weight coefficients for different exploration needs, the optimization design strategy of personalized vibrator bandwidth extension will be proposed. It is hoped that this research can provide theoretical support for wide-band optimization design of vibrator structure and individualized exploration. It is of great significance for the vibroseis to improve the excitation accuracy, achieve wide-band excitation and increase its exploration capability.

可控震源是油气勘探的主力装备，对深层、超深层和非常规油气资源勘探起着重要作用。由于扫描频率激振下振动器激振精度和适用频宽不足，导致激发的勘探信号畸变、低频成分不足、高频出力失准，严重限制了可控震源的勘探能力。本项目通过构建平板底面压力分布方程，以动刚度动阻尼及参振土体描述振动器与大地之间的非线性互作用，建立扫描频率激振下振动器-大地耦合振动模型，突破模型适用频宽较窄的局限，揭示振动器-大地耦合振动规律；基于振动出力和下传能量分析，研究耦合系统参数对激振性能的影响规律，掌握关键耦合系统参数，提高激振精度；以提高振动出力、下传能量和频宽倍频程为目标，建立振动器频宽拓展多参数多目标优化模型，结合针对不同勘探需求的评价因素权重集研究，提出个性化振动器频宽拓展优化设计策略。研究成果为可控震源结构优化设计与个性化勘探提供理论支撑，对于提升激振精度、实现宽频激振，提高其勘探能力具有重要意义。

可控震源是油气勘探的主力装备，在深层、超深层和非常规油气资源勘探领域有着良好的应用前景。由于扫描频率激振下振动器激振精度和适用频宽不足，导致激发的勘探信号畸变、低频成分不足、高频出力失准，严重限制了可控震源的勘探能力。本项目针对上述问题，开展了扫描频率激振下振动器-大地耦合振动模型构建与振动规律研究、耦合系统参数对振动器扫频激振性能的影响规律研究、以及振动器频宽拓展研究。取得了以下主要成果：（1）构建了振动器平板底面压力分布方程，以动刚度动阻尼描述了扫描频率激振下振动器与大地之间的相互作用，构建了平板-大地耦合振动模型，建立了扫描频率激振下振动器-大地耦合振动模型，突破了传统加权和模型适用频宽窄的局限；（2）全面研究了扫描频率激振下振动器-大地耦合振动规律，开展了单频扫描与线性扫描激励下的振动器-大地耦合振动现场试验，分析了动刚度动阻尼、振型、相位、加速度、位移、相位、出力、能量传递等结构响应，开展了耦合参数灵敏度分析，掌握了耦合系统参数对振动器激振性能的影响规律，提出了一种满足扫频激振的振动出力和下传能量计算方法，阐述了振动出力与扫描频率的三阶段关系，解释了系统重锤统治低频响应、平板占据高频响应的机理；（3）开展了振动器低频拓展限制因素和高频拓展限制因素分析，通过蒙特卡罗模拟研究了振动器-大地共振频宽，建立了振动器频宽拓展多目标优化模型，构建了针对不同勘探需求的评价因素权重集，搭建了高效的优化算法模型，提出了个性化振动器频宽拓展优化设计策略，优化拓展了振动器激振频宽、提升了宽频激振性能。项目研究成果为提高可控震源振动器激振精度、拓展可控震源振动器激振频宽提供了理论支持，有力助推了新一代高精度宽频可控震源的研制。