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

Key words: 
• activation energy /
• sensitivity analyses /
• optimization /
• basin modeling /
• Well Tazhong 4

Abstract: 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 simulation outcome of the model in clay mineral coincides with the KAr dating and approaches the data of clay mineral analyses. 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.