蒙皂石转化伊利石的数值模拟——溶解沉淀模型与化学动力学模型

Numerical Modeling for the Smectite to Illite Transformation:Dissolution-precipitation model and kinetic model

提出了改进的溶解沉淀数学模型,在塔里木盆地塔中4井应用获得成功。该井石炭系的实例表明:该模型在粘土矿物内的模拟结果,与K-Ar定年分析吻合,并接近于粘土矿物分析数据。实例指出:在较早提出的化学动力学模型、新近提出的溶解沉淀模型中,最敏感的参数都是活化能;将粘土矿物分析数据作为约束条件来校准活化能,是获得正确的蒙皂石史和伊利石史之关键。采用最佳活化能计算,可获得最佳模拟结果:①算出的伊利石开始生长的年代与K-Ar定年分析吻合;②模拟结果与粘土矿物分析数据接近。通过实例还发现:溶解沉淀模型仅适用于粘土矿物内的转化问题,而化学动力学模型仅适用于伊/蒙间层内的转化问题。

This paper presents an improved mathematical model of dissolution-precipitation, which successfully runs in Well Tazhong 4 of the Tarim Basin. The case study of the Carboniferous Formation in the well shows that the simu- lation outcome of the model in clay mineral coincides with the K-Ar dating and approaches the data of clay mineral an- alyses. The case study indicates that the most sensitive parameter in whether the early-presented kinetic model or the latest presented dissolution-precipitation model is the activation energy, and it is a key to obtain the proper smectite and illite histories that one can calibrate the activation energy by using the data of clay mineral analyses as constraint. By adopting the optimal activation energy, one can obtain the optimal results： （a） the starting time of illite growth calculated coincides with the K-Ar dating, and （b） the results approach the data of clay mineral analyses. It is also found through the case study that the dissolution-precipitation model is only applicable to the transformation in clay mineral while the kinetic model is only applicable to the transformation in illite-smectite interstratifications.