优化的?logR技术及其在中——深层烃源岩总有机碳含量预测中的应用

Improved Δlog R technique and its application to predicting total organic carbon of source rocks with middle and deep burial depth

针对利用Δlog R技术预测中—深层烃源岩总有机碳含量效果较差的问题,依据一一映射原理,利用归一化方法对Δlog R技术进行优化,并引入自然伽马参数,建立优化的总有机碳含量预测模型。该模型不仅可预测中—深层烃源岩有机碳含量,也可预测浅层烃源岩总有机碳含量。引入自然伽马参数,有助于减少非烃源岩高阻段对总有机碳含量预测的影响,增强预测模型的抗干扰能力;将所有参数归一化,不仅消除测井仪器不同等因素带来的误差,也降低运算过程中数据的复杂程度。结合渤海湾盆地东濮凹陷西南部洼陷勘探程度较低,使用测井仪器种类较多和沙三段中亚段烃源岩埋藏较深、声波时差较低的勘探现状,分别利用Δlog R技术和优化的Δlog R技术对烃源岩总有机碳含量进行预测。相比Δlog R技术,优化模型相关系数的平方提高了0.371,估计标准误差降低了0.139,表明优化的Δlog R技术能够较好地预测中—深层烃源岩总有机碳含量的变化趋势。另外,利用优化模型预测东濮凹陷西南部洼陷总有机碳含量分布,结果表明研究区北部为有利烃源岩发育区。

Abstract：An ΔlogR technique has a poor effect on predicting total organic carbon of source rocks with middle and deep burial depth. Aiming at this problem,on the basis of the normalization principle and one-to-one mapping,the ΔlogR tech？ nique was modified and natural gamma ray was introduced to build a model for total organic carbon prediction,by which the total organic carbon can be predicted not only in the middle and deep source rocks but also in the shallow. The intro？ duced natural gamma data helps to reduce the impact of high resistivity of non-hydrocarbon source rocks on total organic carbon estimation and improve anti-interference ability of the prediction model. All data are normalized to solve the errors caused by different well logging instruments or standards,which also helps to reduce the complexity of data in the process. Combined with the exploration situation of southwest subsag in Dongpu Sag,including poor exploration,application of many well logging instruments,source rock buried deeply in the middle of the third member of Shahejie Formation and low acoustic value,the ΔlogR and the improved ΔlogR techniques were applied respectively to predict total organic carbon. Compared with the ΔlogR technique,the square of correlation coefficient is increased by 0.371 and the standard deviation is decreased by 0.139. It indicates that the improved ΔlogR technique could be well applied to predicting total organic car？ bon of source rocks with middle and deep burial depth. In addition,the improved ΔlogR technique was applied to predict？ ing total organic carbon of source rocks in southwest subsag of Dongpu Sag,and the result indicates that the north is a po？ tential area for petroleum exploration.