基于颜色显示快速估算页岩有机碳含量的新方法

有机碳含量(TOC)是页岩气储层评价的关键参数之一,它既是页岩生气的物质基础,也是页岩吸附气的重要载体。以鄂尔多斯盆地山西组页岩系统为例,根据不同的颜色显示划分出4种岩性:黑色煤、灰黑色页岩、灰色页岩、灰白色粉砂岩,赋予这4种岩性不同的颜色显示值,计算页岩系统的总颜色评价值(TCA),拟合页岩系统中TCA和实测TOC之间的关系,依据TCA估算页岩系统的TOC。研究发现,当页岩系统中4种岩性的颜色显示值为等比数列(1、2、4、8)时,TCA和实测TOC相关系数(R2)高,且以指数拟合和三次方拟合的相关系数(R2)最高;页岩系统中TCA的对数和实测TOC的对数呈现良好的正相关性,根据页岩中TCA估算的TOC和实测TOC十分接近。因此,在室外工作中可以利用该方法快速估算页岩系统的TOC,从而为页岩气目标层段的优选提供参考依据。

A NOVEL METHOD FOR ESTIMATION OF TOTAL ORGANIC CARBON IN SHALES BASED ON COLOR MANIFESTATIONS

The total organic carbon （TOC） is one of the key parameters in shale gas reservoir evaluation, it is not only the material basis of shale gas, but also an important carrier of shale gas. Take Shanxi Formation in Erdos Basin as an example, the shales are divided into four different types with different colors： black coal, gray black shale, gray shale, gray white siltstone, then four different color values are given to calculate total color assessment（TCA） of shale and fit the relationship between TCA and measured TOC. The results show that the calculation of TCA is positively correlated with the measured TOC, the correlation coefficient （R2） of exponential fitting and three square fitting is the highest, the calculation of TOC is very close to the measured TOC. Therefore, we can quickly calculate the TOC of shale by using the method in the outdoor work, which provides the reference for the optimization of target zones for shale gas.