圆弧片状声源向地层中辐射声场的有限差分模拟

发布时间：2018-05-28 00:18

本文选题：辐射声场 + 声波测井　；参考：《声学学报》2017年01期

【摘要】：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。
[Abstract]:In this paper, an asymmetrical circular arc sound source for acoustic logging while drilling is proposed, which is aimed at developing a 3-D acoustic remote detection method which can accurately determine the position of reflected body during drilling. In this paper, the characteristics of sound field radiating from this sound source to the formation under complex well hole conditions (drill collar eccentricity, anisotropy and irregular well shape) are studied, and the influence of different well conditions on the 3-D acoustic logging is further analyzed. The numerical simulation results show that, under the condition of circular well hole and the center of drill collar, the circular arc slice sound source can radiate the acoustic wave signal in the formation direction, and the main lobe of the radiation directivity diagram is 3 dB wide, regardless of the fast formation or the slow formation. Because of the low sidelobe level and high azimuth resolution, this method is suitable for 3D reflection imaging logging while drilling, and the factors such as the roughness of well wall and formation anisotropy have little influence on the acoustic field characteristics, which indicates that this method is suitable for rough wellbore and anisotropic formation. The eccentricity of drill collar and the failure of one side of the shaft wall have great influence on the radiation sound field. For the model in this paper, when the depth of failure is less than 3 cm or the distance of eccentricity is less than 2 cm, the sound field still has better azimuth characteristics, and this method is still applicable. However, when the depth of damage is greater than 6 cm, there are many angular lobes with larger amplitude in the sound field directivity diagram, which may not be used to determine the orientation of the reflector. The results of this paper provide an essential theoretical basis for the design and development of three-dimensional acoustic reflectors while drilling.
【作者单位】：中国石油大学油气资源与探测国家重点实验室;北京市地球探测与信息技术重点实验室;美国德州大学奥斯汀分校;
【基金】：国家自然科学基金项目(11204380,11374371,11134011,61102102) 国家油气重大科技专项项目(2011ZX05020-009) 中国石油科技创新基金项目(2014D-5006-0307) 中国石油天然气集团公司项目(2014B-4011,2014D-4105,2014A-3912) 中国石油大学(北京)科研基金项目(2462015YQ0516)资助
【分类号】：TE24;P631.81

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