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提出了一种可用于随钻声波测井的非对称的圆弧片状声源,旨在发展一种能够在钻井过程中精确确定反射体位置的三维反射声波远探测方法。研究了在复杂的井孔条件(钻铤偏心、各向异性和不规则井孔形状)下,该声源向地层中辐射的声场的特征,进一步分析了不同井况条件对三维随钻远探测声波测井的影响。数值模拟结果表明,在圆形井孔、钻铤居中条件下,无论快速地层还是慢速地层,圆弧片状声源均能够向地层中定向辐射声波信号,其辐射指向性图主瓣3 dB角宽窄,旁瓣级低,方位分辨率较高,适用于随钻三维反射成像测井;井壁粗糙程度、地层各向异性等因素对声场特征影响不大,说明该方法适用于粗糙井壁和各向异性地层情况;钻铤偏心和井壁一侧的破坏对辐射声场的影响较大。对本文的模型而言,在破坏深度小于3 cm或者偏心距离小于2 cm时,声场仍有较好的方位特征,该方法仍然适用。而当破坏深度大于6 cm,声场指向性图出现多个幅值较大的角瓣,可能无法利用其确定反射体的方位。本文的研究结果为三维随钻反射声波仪的设计和研发提供了必备的理论基础。
An asymmetrical circular flaky sound source, which can be used for logging-while-drilling sonic logging, is proposed to develop a three-dimensional (3D) reflected soundwave far detection method that can accurately determine the reflector’s position during drilling. The characteristics of the acoustic field radiated by the sound source into the formation under complicated wellbore conditions (eccentricity of the collars, anisotropy and irregular borehole shape) are studied. Further analysis is made on the sound field radiated by the sound source to the formation under different well conditions Impact of acoustic logging. The results of numerical simulation show that, in the case of circular wellbore and collar, the circular arc flake sound source can direct the radiated sound wave signal in the formation both in fast and slow formations. The main beam of the radiation pattern is 3 dB Angle width, low side-lobe and high azimuth resolution, which is suitable for logging 3D logging while drilling. The factors such as the roughness of the borehole wall and formation anisotropy have little effect on the sound field characteristics, indicating that this method is suitable for rough borehole wall And anisotropic formation; the eccentricity of drill collar and the damage on one side of the borehole wall have a great influence on the radiation field. For the model in this paper, the sound field still has good azimuth characteristics when the depth of failure is less than 3 cm or the eccentric distance is less than 2 cm. This method is still applicable. When the destructive depth is more than 6 cm, multiple amplitude lobes appear in the acoustic field. It may not be possible to determine the orientation of the reflector. The results of this paper provide the necessary theoretical basis for the design and development of 3D LDRS.