改进的Δlog R模型在烃源岩评价中的应用

Application of Improved Δlog R Model in Evaluation of Source Rocks

传统的Δlog R模型在基线值、电阻率和声波时差之间的关系系数确定等方面存在很强的主观性、区域实用性等问题。针对以上问题,选取鄂尔多斯盆地盐池-定边地区长7油层组泥页岩等复杂岩性作为研究对象,采用追本溯源的思想,对Δlog R模型的由来进行了数学推导。利用Δlog R基线的模型化和不同实测点的斜率动态化取代传统Δlog R模型中电阻率和声波时差叠合系数为固定值的算法,得出改进的Δlog R模型的计算公式,并在研究区对计算结果进行验证和误差分析。改进的Δlog R模型得出的有机碳含量与实测的有机碳含量符合程度较高;单井纵向上表现出长7油层组有机质丰度非均质性很强,具有向上变小的趋势;改进的Δlog R模型较传统模型计算误差最小,适用范围得到一定程度扩大,可在盐池-定边地区推广应用。

The traditionalΔlog R model can be used to evaluate the organic matter abundance but this method has strong subjectivity and regional differences while determining the baseline value and the relationship coefficient between resistivity and acoustic time difference.In view of the above problems the complex lithology such as the shale in the Yanchi-Dingbian area of Ordos Basin was selected as the research object and the idea of tracing back to the origin was used to deduce the equation ofΔlog R.By modelling ofΔlog R baselines and changeable slopes among different measured spots replacing the fixed composite coefficient the improvedΔlog R calculation formula was obtained The results of the improved model were verified by the core and the error analysis was carried out it is found that the organic carbon content obtained by the improvedΔlog R model was in good agreement with the core analysis results.For single well the calculation results of the new model show that the heterogeneity of organic matter abundance was very strong in the longitudinal direction in Chang7 Reservoir but there was a tendency to become smaller.Compared with the traditional model the improvedΔlog R model has little calculation error and the scope of application has been expanded to a certain extent which means that this method can be used for source rock evaluation in whole Yanchi-Dingbian region.