Experimental Study On The Interaction Between Smectite Minerals And Organic Matter

Smectite is an important clay mineral that can adsorb a large amount of organic matter.The interaction between smectite and organic matter occurs widely in sediment,mudstone and shale.During diagenesis and low-grade metamorphism,the conversion of tri-octahedral smectite into chlorite and di-octahedral smectite into illite are the two common clay mineral transformations.There has been a great deal of research work on the preservation of organic matter and oil and gas accumulation by the transformation of the montmorillonite.However,the adsorption mechanism of the organic matter on the smectite and how the organic matter affects the transformation of smectite,especially the saponite chloritization,have not yet been solved and studied.In view of this,two typical natural organic matter,Lysine(left-handed)and Chitosan,were combined with smectite,in order to study the adsorption mechanism of organic matter into the smectite and the difference with the other clay minerals.In addition,a hydrothermal simulation experiment of the transformation of the smectite minerals was carried out to study the influence factors and transformation mechanism of the saponite chloritization.At the same time,the two kinds of organo-smectite complex were carried out in the hydrothermal simulation experiment to study the difference of the influence of organic matter between the montmorillonite illization and the saponite chloritization.The main results are as follows:1.The maximum adsorption order of lysine on different clay minerals in the same conditions are:saponite>montmorillonite>chlorite>kaolinite>illite.The correlation coefficient of the clay minerals fitted with the Freundlich equation is greater than the correlation coefficient of the Langmuir equation.There are two adsorption mechanisms for the lysine:the cation exchange and the attraction of organic molecules.Lysine will choose the form of cation exchange into the interlayer firstly.With the increase of concentration,lysine will enter into the interlayer of saponite by the combination of Van Edward force and hydrogen bond with the attraction and distribution of organic molecules.2.Lysine is adsorbed on the interlayer of saponite,mainly adsorbed on the hydroxyl sites.Lysine is mainly adsorbed on the surface of chlorite,kaolinite and illite,and there is a very small amount of interlayer adsorption in chlorite and illite.Kaolinite is easier to reach saturated adsorption than other clay minerals at low concentration.The lysine-saponite complex is much more stable than the other lysine-clay complexes.3.Under high temperature conditions,the saponite chloritization can occur quickly,and there is no mixed layer mineral in the reaction process,and the crystallinity of chlorite is high.At low temperature,the degree of chloritization of the saponite is low and the crystallinity is poor.The alkaline environment is more conducive to the saponite chloritization.Under the same conditions,the participation of lysine will inhibit the development of chloritization,and chitosan cannot influence the process of saponite chloritization.4.Conditions such as temperature,time,pH and water/rock ratio will affect the process of montmorillonite illization.Under the same conditions,the accompanying organic matter will not change the degree of illization,but it will affect the crystallinity of illite formed.Lysine and chitosan have a promoting effect on the montmorillonite illization,but with the increase of temperature,the promotion effect is decreasing,and the temperature plays a decisive role in all the conditions.