Study On CO₂ Bubble Motion And Wettability Of Rock Surface

Supercritical CO₂ geological storage,as a method to reduce CO₂ content in atmosphere quickly and permanently,has been paid more and more attention by many countries.The wettability of rock surface has an important influence on geological storage.According to the geological storage conditions,different solutions?water?in high temperature and high pressure environment?temperature:45?,60?,80?,pressure:8¹6MPa?were studied by means of capture bubble method and volume addition and subtraction method.The bubble motion characteristics of CO₂ in NaCl,MgCl₂)and the variation of contact angle on the surface of phlogopite.In that aspect of bubble motion,the deformation coefficient of the bubble and the velocity of the bubble movement are describe.The results show that:?1?the deformation coefficient of the air bubble is gradually increased in the course of motion,reaching the peak value at the time of collision with the surface of the phlogopite,and then to a fixed value after several wave fluctuations;the movement speed of the air bubble is almost zero at the growing stage,and gradually increases after the injection needle is separated from the injection needle;energy loss after a collision with a phlogopite surface,a speed reduction,a plurality of repeated collisions,a final velocity approaching to zero and still at the phlogopite surface;?2?the further the bubble initial position is away from the phlogopite surface,the greater the velocity of the bubble and the phlogopite surface,the more serious the degree of deformation of the air bubbles is,?3?the change of the bubble motion characteristics under different circumstances:the deformation coefficient exhibits an increased tendency with the increase of the temperature,and the deformation coefficient in the brine is larger than the deformation coefficient in the water,And the maximum value of the bubble movement speed gradually increases with the increase of the temperature,and decreases with the increase of the ion concentration.The results show that:?1?under the existing experimental conditions,the velocity of the bubble and the surface of the phlogopite is changed by changing the initial position of the bubble and the surface distance of the phlogopite,and the effect of the velocity on the final contact angle is found to be small;?2?the contact angle?static contact angle,dynamic contact angle?increases with the increase of temperature and decreases with the increase of ion concentration.At the same ion strength,the contact angle in MgCl₂ solution is larger than that in NaCl solution.However,there is no unified trend of the influence of pressure on contact angles.?3?two different experimental phenomena were observed in the backward contact angle experiment:one was that the bubble was finally pressed into the injection needle and completely disappeared;The other is that the bubble finally breaks away from the injection needle and forms a stable contact angle on the surface of phlogopite,resulting in adhesion.The forward contact angle and the backward contact angle of the two phenomena are different.Whether or not the adhesion phenomenon occurs,the backward contact angle is larger than the forward contact angle,but the forward contact angle when the adhesion phenomenon occurs is larger than the forward contact angle when it does not occur.However,the backward contact angle of the adhesion phenomenon is smaller than that of the backward contact angle when the adhesion phenomenon occurs.In this paper,the bubble motion characteristics of supercritical CO₂ in brine solution and the contact angle of phlogopite surface are studied,which enriches the research data of bubble motion characteristics and mineral surface wettability,and finds the evolution law of wettability.It has important reference value for the development of theory and technology of Supercritical CO₂ geological storage.