气体钻井近钻头超前探测声源评价与优选

Evaluation and Optimization of Acoustic Sources for Advanced Detection nearDrill Bits in Gas Drilling

  • 摘要: 为了优选适用于气体钻井条件下的近钻头超前探测声源,提出了气体钻井条件下近钻头声波超前测距方法,进行了不同探测距离下的超声波测距、冲击回波共振测距、扫频声波共振测距和冲击震源测距试验,分析了4类声波测距声源的可行性,并从声源特征、探测距离和分辨率3个方面优选了适用于气体钻井的近钻头超前探测声源。试验结果表明:当超声波的频率较低且尾波较短时,可从靠近声波发射源接收到的波形中识别出反射波信号,但探测距离近;冲击回波共振频率受岩性影响较大,导致入射波与反射波之间未形成理想的驻波,其共振测距的误差较大;扫频声波产生的入射波和反射波可形成较为理想的驻波,测距误差较小,但对扫频发生器的低频性能要求高;根据试验结果优选出的冲击震源可用于探测岩性界面,该冲击震源的尾波被显著衰减,有利于识别时域内的地层反射波信号。研究表明,优选出的冲击震源具有冲击能量强、频率低和尾波短的优势,可满足气体钻井条件下超前探测对声源的要求。

     

    Abstract: To optimize the acoustic sources for advanced detection near drill bits in gas drilling environments, a near-bit acoustic ranging method was proposed. This method is specifically tailored for gas drilling conditions. Experiments were conducted on ultrasonic ranging, impact echo resonance ranging, sweep-frequency acoustic resonance ranging, and impact reflection wave ranging at various detection distances. The feasibility of these four types of acoustic sources for ranging was evaluated. The near-bit acoustic source suitable for gas drilling was optimized based on three factors: acoustic source characteristics, detection distance, and resolution. Experimental results indicate that when the ultrasound frequency is low and the tail wave is short, the reflected wave signal can be identified in the waveform received close to the acoustic wave emission source, but the detection range is limited. The frequency of the impact echo is highly influenced by lithology, which prevents the formation of an ideal standing wave between the incident and reflected waves, leading to significant errors in resonance ranging. The incident and reflected waves generated by sweep-frequency acoustic sources form relatively ideal standing waves, resulting in smaller ranging errors. However, this requires high low-frequency performance of the sweep-frequency generator. The preferred impact source can effectively detect lithological interfaces, and its tail wave experiences significant attenuation, which is beneficial for identifying reflected wave signals from the formation in the time domain. The results show that the preferred impact source offers advantages such as strong impact energy, low frequency, and short tail wave, which meet the acoustic source requirements for advanced detection under gas drilling conditions.

     

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