This paper introduces a new method, that is, cation/oxygen ratio (CATO), a carbon/oxygen type measurement, to calculate the residual oil saturation based on the raw spectral logging data.

• CATO是碳氧比能谱测井中,非弹性散射谱线中消除了氧计数影响的非弹性散射计数率与氧的计数率的比值,该值对油和水的响应与常规碳氧比值相似;