长庆油田长7段黏土矿物X衍射分析K因子的求取及应用

过去一直被认为是烃源岩的长7段泥页岩，目前被证实可以作为页岩油储层，这就使得定量分析长7段岩石中各类黏土矿物含量变得十分重要。由于不同地区黏土矿物结晶程度存在差异，导致传统X衍射定量分析的行业标准并不具有普适性，因此要精确测量长7段黏土矿物含量，就需要针对研究区具体情况，实测一套符合该区情况的K因子。利用X衍射定量分析中的K因子法，以石英为内标物，求取长7段岩石中各类黏土矿物的K因子，进而计算出了各矿物的含量。此外，通过X荧光光谱矿物化学配平以及热重分析两种方法对相应样品进行了黏土矿物的定量和半定量分析，进一步验证了K因子的正确性，分析结果与利用K因子法获得的矿物含量具有较好的一致性。所求取的K因子，对今后该区域利用X射线衍射法定量分析黏土矿物含量提供了基础参数，从而可以促进判断页岩的岩性、对比不同岩性岩石中单矿物含量及变化关系等方面的研究。

The Calculation and Application of K Factors of Clay Minerals by X-Ray Diffraction Analysis in Chang7, Changqing Oilfield

The shale in Chang 7 oil-bearing formation of the upper Triassic Yanchang Formation, Ordos Basin, have always been considered as high quality hydrocarbon-source rock in past, but recent exploration shows this oil-bearing formation is a possible shale reservoir and rich in oil and gas resources.However, the research of its characteristics of lithology and reservoir is still limited, and the traditional research methods of petrological characteristics of sandstone are disappointment for the shale which are composed of fine grains.Consequently, it is extraordinarily important to confirm the lithology and reservoir characteristics of Chang 7 oil-bearing formation by quantitatively calculate the content of clay minerals in the rocks of it.In the quantitative analysis of XRD, the diffraction peak intensity of each mineral is related to the content of the mineral, but it is not a simple proportional relationship, so we need rectify the result by the K factor.Because the special structure and the different crystallization degree of clay minerals are the main factors which influence the K factor, instead of using the results of the former researches, we need calculate the K factors of the clay minerals in Chang7 oil-bearing formation.Therefore, based on the internal standard method of XRD analysis, we carried out the clay mineral separation step to deal with the samples for increasing the proportion of clay minerals, and used quartz as the internal standard material.Depending on the change of quartz content, the diffraction intensity of minerals in two XRD analysis of with and without the internal standard material, we can calculate the K factors.Then, using the internal standard method, the content of each mineral in the rock can be calculated by the K factors.In order to verify the K factor, we choose monomineralic balancing method based on XRF and thermogravimetric analysis to get quantitative and semi-quantitative result, respectively.The analysis result has good consistency with mineral content that calculated based on the K value.The consistency shows the K factor is reliable.In practice, the mineral content calculated by K factor analysis method is useful in judging lithology and comparing mineral content and variation relationship of different kind rocks.