Role of Microbes in the Smectite-to-Illite Reaction

Temperature, pressure, and time have been thought to control the smectiteto-illite (S-I) reaction, an important diagenetic process used for petroleum exploration. We demonstrated that microorganisms can promote the S-I reaction by dissolving smectite through reduction of structural FE(III) at room temperature and 1 atmosphere within 14 days. This reaction typically requires conditions of 300° to 350°C, 100 megapascals, and 4 to 5 months in the absence of microbial activity. These results challenge the conventional concept of the S-I reaction and of reaction kinetic models.