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准确识别气水是气藏测井评价的一个关键问题,提出了利用不同观测模式下T_2谱中心位置差异来识别气水的方法。理论分析发现,改变核磁共振测量模式会使得到的T_2谱中心位置发生变化,而天然气对这种变化比地层水更为敏感,可以利用这一性质进行气水识别。编制了利用不同等待时间或不同回波间隔T_2谱进行气水识别的软件,并对四川盆地某地区碳酸盐岩储层气藏进行了测试,气水识别结果与试油结果一致,证明了所提方法的有效性。将该方法应用于多口井,结果显示具有较好的识别效果,同时发现利用不同回波间隔的2组T_2谱对数均值差异进行气水识别的准确性要高于不同等待时间的2组T_2谱。
Accurately identifying gas and water is a key issue in gas reservoir logging evaluation. A method to identify gas and water using the difference of T 2 spectrum center positions in different observation modes is proposed. Theoretical analysis shows that changing the NMR measurement mode will change the center position of T_2 spectrum, while natural gas is more sensitive to this change than formation water, and this property can be used to identify gas and water. The software of gas and water identification using different waiting time or T_2 spectrum with different echo intervals was developed and the carbonate reservoir in a certain area of Sichuan Basin was tested. The result of gas and water identification was consistent with that of the test oil, The effectiveness of the proposed method. The method is applied to multiple wells and the result shows that the method has a good recognition effect. At the same time, it is found that the gas-water identification accuracy of logarithmic mean difference of two T_2 spectra with different echo intervals is higher than that of two groups with different waiting time T_2 spectrum.