X射线荧光录井砂泥岩地层识别方法

Identification method for sand-shale formation by X-ray fluorescence logging

PDC钻头快速钻井条件下,井底返出的岩屑细碎且混杂,常规岩屑录井难以有效识别地层岩性。针对该问题,依据岩石地球化学理论的岩石矿物元素组成及其含量,以X射线荧光录井测得的岩石矿物元素及其含量数据为基础,分别定义了反映砂岩砂质含量的Si/(Al+Fe+Si+Ca)和泥岩泥质含量的(Al+Fe)/(Al+Fe+Si+Ca)特征参数并分析了其意义,据此建立了两曲线交会图板。应用过程中,分别结合砂岩地层"一高三低"和泥岩地层"三高一低"的测井曲线辅助特征,可实现砂泥岩地层的识别。实例分析表明,利用该方法不但可以有效识别砂泥岩地层,而且通过不同砂岩或泥岩井段的对比可以反映岩性的相对纯度。

Under the condition of fast drilling by PDC bit,cuttings returning from the downhole are fine and mixed,it is difficult for conventional cutting logging to identify formation lithology effectively.In view of this problem,on the basis of elementary composition and their contents of rock minerals from rock geochemistry theory,taking the rock mineral element and its content data measured by X-ray fluorescence logging as the basis,the authors defined the characteristic parameters of Si/(Al+Fe+Si+Ca)which reflects sabulous content of sandstone and(Al+Fe)/(Al+Fe+Si+Ca)which reflects argillaceous content of mudstone and analyzed their meaning,thus two-curve crossing chart was established.Combining with the auxiliary characteristics of logging curves respectively:1-high and 3-low sandstone formation and 3-high and 1-low mudstone formation,the identification of sandstone and mudstone formations can be realized.The example analysis showed that the method not only can effectively identify the sandstone,mudstone formations,but also reflect the relative purity of lithology through the comparison of the different sandstone or mudstone intervals.