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准确地测量煤层气储层的声波时差是提高煤岩力学参数、地应力计算精度的保障,进而为压裂施工设计提供测井技术支持.煤岩性脆、机械强度低,钻进过程中不可避免地会出现井壁坍塌、扩径,致使声波时差测井值受扩径的影响在所难免.现有声波时差测井扩径影响校正方法多针对的是石油领域的砂泥岩剖面而提出的,专门针对煤层气储层的方法尚不多见,现有方法是否适用于煤层气储层不得而知.鉴于此,本文以鄂东气田韩城矿区为例,采用统计方法对研究区主力煤层的声波时差、井径测井响应特征进行了翔实剖析,发现扩径严重的煤层气储层声波时差较大.通过对常用声波时差扩径影响校正方法进行系统梳理和深入分析,得知其在煤层气储层中的适用性.优选适用性较高的频率法,对研究区煤层气储层进行了扩径影响校正.结果表明,校正结果较实测值低、且与实验室分析化验值较为接近,表明频率法能够较有效地提高声波时差测井扩径影响的校正精度.
Accurately measuring the acoustic jet lag of CBM reservoirs is the guarantee to improve the calculation accuracy of coal rock mechanics parameters and in-situ stress, and then provides the logging technical support for fracturing design.The brittleness of rock is brittle, the mechanical strength is low, The avoidance of borehole wall collapses and enlargement will inevitably cause the sonic logging to be affected by the expansion of diameter.Because the correction method of sounding time-difference logging expansion effect is mostly aimed at the sandstone-mudstone profile of oil field It is not clear whether the existing method is suitable for CBM reservoirs.In view of this, taking Hancheng mining area in the East Ordovician gas field as an example, the authors use statistical methods to analyze the main coal seams in the study area The time difference of acoustic wave and the logging response of borehole logging are analyzed in detail, and it is found that the time difference of sound wave in the coalbed methane reservoir with serious expanding diameter is large.Through the systematic analysis and further analysis of the correction methods of the commonly used acoustic jet lag effect, The applicability of coalbed methane reservoirs, and the better applicability of frequency method to calibrate the expansion of CBM reservoirs in the study area.The results show that the calibration results are lower than the actual measured values, Analysis of laboratory values are close to the chamber, indicating frequency method can more effectively improve the correction accuracy acoustic logging diameter effects.