钻井液浸泡对巴西改组岩石声学特性的影响

The influence of drilling fluid soaking on rock acoustic characteristics in Baxigai Formation

万有维 熊健 刘向君 梁利喜 龚洁2

西南石油大学油气藏地质及开发工程国家重点实验室，四川 成都 610500 中国石油测井有限公司新疆分公司，新疆 克拉玛依 834099

State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu 610500, China China Petroleum Logging Co., Ltd., Xinjiang Branch, Karamay 834099, China

在钻井过程中，钻井液浸泡后的地层岩石会发生损伤并诱发井下复杂事故，造成井壁失稳。文中以巴西改组岩石为研究对象，采用超声波透射法对钻井液浸泡前后的岩石进行声波测试，利用傅里叶变换、小波变换等研究了岩石声学特性，并讨论了钻井液浸泡对岩石声学特性的影响。研究结果表明：浸泡前，泥岩的声波时差、衰减系数大于砂岩；浸泡后，砂岩与泥岩的衰减系数增大，砂岩声波时差降低而泥岩声波时差增大，且砂岩与泥岩频域信号振幅明显降低，高频信号被吸收，低频信号比例增加，声波信号主频向低频方向发生偏移。借助小波变换，从微观角度来看，钻井液浸泡后岩石结构发生损伤，且泥岩的损伤较为严重。

During the drilling process, the rock will be damaged after the drilling fluid soaking, which will induce complex downhole accidents and cause the instability of the wellbore. Taking the rock in Baxigai Formation as the research object, acoustic test is carried out on the original rocks and the rocks after drilling fluid soaking by ultrasonic transmission method. The acoustic characteristics of the rocks are investigated by Fourier transform and wavelet transform, and the influence of drilling fluid soaking on rock acoustic characteristics is discussed. The results show that interval transit time and the attenuation coefficient of mudstone are larger than that of sandstone, and the attenuation coefficient of sandstone and mudstone increases after soaking. The interval transit time of sandstone decreases after soaking, while the mudstone increases. The signal amplitude of the sandstone and mudstone frequency domain is significantly reduced after soaking, the high frequency signal is absorbed, the proportion of the low frequency signal is increased, and the dominant frequency of the acoustic signal is shifted to the low frequency direction. From the microscopic point of view, by means of wavelet transform, the microstructure of the rock is damaged, and the damage of the mudstone is serious after the drilling fluid soaking.

10.6056/dkyqt202004023