提高伽马伽马曲线煤层定厚解释精度方法探讨

在贫煤地区,煤炭资源赋存差异较大,纳入资源量计算的煤层厚度也较低,个别地区甚至降到0.30m。目前煤层定厚解释常用视电阻率曲线和伽马伽马曲线。煤层顶底板在视电阻率曲线的解释点是"根部拐点",因此人为误差较小;而伽马伽马曲线的解释点是煤层密度和煤层顶底板密度的二维函数,变化较大。根据伽马伽马测井曲线的对称性原理,提出利用平均密度法确定煤层定厚点,即用煤层伽马伽马曲线幅值分别与顶、底板围岩的伽马伽马曲线幅值相乘后再开方的方法获得煤层定厚顶、底板解释点的伽马伽马幅值。该方法既提高了伽马伽马曲线煤层定厚解释精度,又将复杂问题简单化,在实际工作中具有较强的可操作性和使用性。

A Discussion on Gamma-gamma Logging Traces Coal Seam Thickness Interpreting Accuracy Improvement

In coal shortage areas, there have larger coal resources hosting differentia, the coal thickness lower limit can be incorporated into resource estimation is rather low, in some areas even downgrade to 0.30m. At present, coal seam thickness interpretation commonly uses apparent resistivity and gamma-gamma traces. Coal roof and floor interpreting points on apparent resistivity traces is according to the“root knee points”, thus smaller human errors;while on gamma-gamma traces are 2D functions of coal seam density and coal roof, floor density, thus larger changes. Based on symmetry principle in gamma-gamma logging, using average density method to determine coal seam thickness has been put forward. Those is using coal seam gamma-gamma traces amplitude multiplies by coal roof, floor country rock gamma-gamma traces amplitudes respectively, and then extract to get gamma-gamma amplitude to interpret thickness deter-mining roof and floor points. The method can not only improve gamma-gamma traces coal thickness interpretation accuracy, but also simplify complex issues, thus stronger operability and applicability in practices.