The Effect Of Polyethylene Glycol On The Swelling Of Clay And The Settlement Of Slime Water

Clay minerals have the characteristics of being easy to swell and disperse in contact with water.This property of clay will make it difficult for the slime water to settle during the coal preparation process and cause damage to the reservoir during the development of the oil field.The expansion of minerals is mainly due to the hydration of montmorillonite.Inorganic cations can compress the diffusion double electric layer on the surface of particles to increase Zeta potential and reduce the thickness of hydration film on the surface of particles.Moreover,it can reduce the repulsion force between particles and crystal layers,and reduce the stability of slime water.Polyethylene glycol and other macromolecules destroy the ordered water molecular structure on the surface and between layers of clay by adsorbing on the surface of clay and replacing the water molecules adsorbed by clay,so as to weaken the hydration expansion and dispersion of clay and achieve the purpose of inhibition.In this paper,the expansion law of montmorillonite is studied.The inhibitory effect of polyethylene glycol and KCl on the expansion and dispersion of montmorillonite under inhibited and non-inhibited conditions is studied by viscometer and particle size distribution analyzer.Zeta potential,X-ray diffraction and infrared Spectroscopy analysis of inhibitor mechanism.The main conclusions are as follows:(1)The expansion test of montmorillonite shows that there are two aspects of the hydration expansion of montmorillonite.On the one hand,the water molecules undergo a difference in concentration and enter the interlayer;on the other hand,the surface of the montmorillonite particles will adsorb water molecules.The hydration film is continuously increasing,which makes the montmorillonite particles disperse.The formation of hydrated layer on the surface of montmorillonite is slow,and the whole process lasts about 40 hours.Lattice expansion is a faster and slower process.The layer spacing of the montmorillonite raw soil is 12.41?,and the maximum after hydration expansion is about 14.75?.Under acid condition,the diffusion double layer on the surface of montmorillonite is compressed,and the cation exchange capacity of montmorillonite decreases.With the decrease of p H value of solution,the hydration index of montmorillonite is also decreasing.When the p H is 3,the hydration index is0.27.(2)The inhibition performance of PEO increases with the increase of molecular weight and hydrophobicity.The higher the concentration of PEO,the stronger the inhibition of montmorillonite hydration.The inhibition performance under the inhibition condition is obviously better than the non-inhibition condition:the particle size of the system under the inhibition condition is larger than the non-inhibition condition,and the absolute value of the Zeta potential under the inhibition condition is smaller than that in the non-inhibition condition.(3)K~+can exchange Na~+between montmorillonite layers and reduce the adsorption of water molecules between the layers.PEO can be adsorbed on the surface of clay particles,prevent the contact of clay with water,weaken the contact of free water molecules with the surface of clay and penetrate into the crystal layer,thereby inhibiting the expansion of montmorillonite particles.At the same time,PEO can be inserted between the layers of montmorillonite,so that the interlayer distance reaches 17.57?.The inhibitor will not change the structure of montmorillonite.When PEO4000 and K~+exist at the same time,there will be a synergistic effect,which will increase the hydrocarbon adsorption of montmorillonite and increase the hydrophobicity of montmorillonite.(4)Clay inhibitor can significantly improve the settling performance of slime water.Compared with PEO4000,the settling effect of slime water is better when KCl is used as inhibitor.When PEO and KCl were used at the same time,the dosage of reagents needed was small.The slime water with solid concentration of 3%could reach the upper liquid clarification state within 24 hours in the inhibition environment with PEO concentration of 0.15%and KCl concentration of 0.25%.The paper has 30 pictures,14 tables and 101 references.