低阻砂岩气藏测井饱和度计算方法——以准噶尔盆地玛河气田为例

Calculation Method of Logging Saturation in Low Resistivity Sandstone Gas Reservoir:Case Study of the Mahe Gas Field in Junggar Basin

为了解决准噶尔盆地南缘地区低阻油气藏饱和度计算数值不准问题,以玛河气田古近系紫泥泉子组低阻砂岩气藏为例。通过孔渗、岩电、铸体薄片、阳离子交换容量等实验数据,研究分析阳离子交换量、阳离子当量电导、阳离子交换容量、胶结指数、饱和度指数等参数的变化规律,建立适用于低阻砂岩气层含水饱和度计算的变参数的Archie饱和度模型和Waxman-Smits(W-S)饱和度模型,并进行实例井验证,获得良好效果。研究结果表明:在低阻砂岩气层中,常规的Archie模型适用于胶结指数、饱和度指数较小的纯产气或电阻率较低的水层,但在气水同层中解释效果较差;而通过变参数的Archie与W-S模型计算出的含水饱和度值均满足同一段储层下部含水饱和度大于储层上部的规律特征,其结果数据与岩心分析、气测试结果相吻合。两种饱和度计算新模型对低阻砂岩气藏储层饱和度的解释精度和流体识别的准确度提高方面具有重要指导意义。

In order to solve the problem of inaccurate calculation of the saturation of low-resistance oil and gas reservoirs in the southern margin of the Junggar Basin,the low-resistivity sandstone gas reservoir of the Paleogene Ziniquanzi Formation in the Mahe gas field was taken as an example.Based on the experimental data of porosity,rock electricity,casting thin slices and cation exchange capacity,the changes of cation exchange capacity,cation equivalent conductance,cation exchange capacity,cementation index m,saturation index n and other parameters were studied and analyzed in detail.Both Archie saturation model and W-S saturation model with variable parameters change were established well,which were suitable for the calculation method of water saturation of low resistivity sandstone gas reservoir.They were verified by an example well.The results showed that the conventional Archie model was suitable for pure gas production or water layers with low resistivity with smaller parameters m and n,while the interpretation effect was poor in the same gas and water layer in low-resistance sandstone gas layers.The water saturation values calculated by the variable parameter Archie and W-S models all satisfy the characteristics that the water saturation in the lower part of the reservoir was greater than the upper part of the reservoir in the same section.The result data was confirmed to be consistent with the core analysis and gas test results.The two new saturation calculation models were of great significance to improve the accuracy of reservoir saturation interpretation and fluid identification in low resistivity sandstone gas reservoirs.