Interstratified illite–smectite phases: formation mechanisms and practical applications

Abstract

Secondary micas after smectite, including mix illite–smectite phases, can form in sediments by three mechanisms, each being specific to particular environments. As the process develops, the newly formed phases undergo structure ordering. Two mechanisms involve transformation of 2:1 mixed-layer structures, and the third is the growth of screw dislocations, with formation of ordered mix phases having a Reichweite parameter of R = 1 or R = 2. We propose methods for identifying such phases when they are present in small amounts or when their XRD patterns lack well-pronounced superperiodic reflections, as well as mathematical formalism for illitization modeling. The theoretical issues are illustrated with field examples, and the illitization mechanisms are discussed in terms of their possible practical applications.

Petrographic Insights into the Evolution of Nano-Scale Organic Matter Pores with Organic Matter Conversion

“…A weak/moderate positive correlation is observed between Smic and TOC content (R 2 = 0.48) for the DMG shales, and a weak positive or no correlation (R 2 = 0.15) is observed between SBET and TOC content (Figure 7). These results are similar to the pore structure-TOC relationships for shales of the Lower Jurassic Gordondale Member from the Western Canadian Basin, together indicating that neither micropore surface area nor BET surface Generally, mixed-layer I/S and illite are the intermediate and final products of the diagenetic conversion of smectite to illite, respectively [45]. The dissolution of feldspar, which is involved in kaolinite formation, is regarded as the main source of K + and Al 3+ [43,46] and promotes the transformation of smectite to illite and I/S.…”

“…The formation of kaolinite reduces the primary porosity and contributes to a decrease in secondary porosity [34], resulting in a weak negative correlation between kaolinite content and pore structure parameters. Generally, mixed-layer I/S and illite are the intermediate and final products of the diagenetic conversion of smectite to illite, respectively [45]. The dissolution of feldspar, which is involved in kaolinite formation, is regarded as the main source of K + and Al 3+ [43,46] and promotes the transformation of smectite to illite and I/S.…”

Understanding Shale Instability through the Lens of Clay Mineralogy and Zeta Potential

“…The most tiresome task for shale stabilization studies is the choice of a proper shale sample especially when the role of any novel inhibitor is being studied. Because it will be useless to perform swelling experiments on shale outcrop which doesn't have any smectite content or haven't undergone through illitization [72][73][74][75][76][77][78][79][80][81][82]. Similarly, for shale Shale recovery (%)…”