关于利用自然伽马曲线对砂泥岩临界值的确定

--Use gamma log ray log curve to determine the critical value of sandstone and mudstone

鄂尔多斯盆地东部砂岩储层致密、黏土矿物含量及炭屑含量高，导致砂岩在测井曲线上显示的自然伽马响应泥质含量比地层实际泥质含量高，这给地质解释带来一定困惑，究竞自然伽马测井曲线上读取的砂质含量多少可以作为解释砂岩与泥岩的临界值？基于此，以鄂尔多斯盆地东部致密砂岩储层特征和自然伽马测井的原理为基础．结合录井描述、岩心观察及化验分析等资料对岩性和测井地质解释进行一一标定，利用频率统计法计算出砂质含量为60％V作为砂岩的临界值，这个结论对今后储层研究具有一定的指导意义。

Sandstone reservoirs in the eastern Ordos Basin are tight, with high contents of clay mineral and carbon debris. This leads to a higher shale content of sandstone on the displayed response of natural gamma ray log than the actual shale content. This brings some confusion to geological interpretation. How much arenaceous content read from the gamma ray log curve can be as interpretation of critical value between sandstone and mudstone？ Based on the reservoir characteristics of tight sandstone in eastern Ordos basin and gamma ray logging principle, combined with data such as logging description, core observation and laboratory analysis, etc., the litbology and logging interpretations are calibrated one by one. The sabulous content of 60% calculated with frequency statistics method can be used as a sandstone threshold. This conclusion has some significance for the future reservoir study.