Modification Process of Sulfonated Asphalt for Drilling Fluid
Raw Material Pretreatment: Select petroleum asphalt and remove impurities such as dirt and sand grains by filtration or precipitation methods before setting it aside for later use. Sulfonation Reaction: Use oleum or sulfur trioxide as the sulfonating agent. Place the asphalt in a reaction kettle at a temperature ranging from 120 to 160 °C, stir and heat it, and then slowly add the sulfonating agent. Strictly control the addition speed (if it is too fast, it is likely to cause violent local reactions and side reactions) and the reaction time (usually 3 to 6 hours, which depends on the properties of the asphalt and the amount of the sulfonating agent used), so that some hydrogen atoms in the asphalt molecules are replaced by sulfonic acid groups, thus changing the chemical structure of the asphalt.
Neutralization Treatment: After the sulfonation reaction, use sodium hydroxide or calcium hydroxide to neutralize the acidic system. For example, the reaction between NaOH and R - SO₃H generates R - SO₃Na, which improves the water solubility and dispersibility. Precisely control the amount of the alkaline substance to ensure that the pH value of the product is between 7 and 9. Post-treatment and Drying: Wash the neutralized product with water to remove inorganic salts and impurities, and then treat it by spray drying or vacuum drying. The former is beneficial for dispersion, while the latter can avoid the impact of high temperatures.
Purposes of Modifying Sulfonated Asphalt for Drilling Fluid
Filtration Loss Reduction: Due to the fact that the modified sulfonated asphalt can adsorb on the rock of the wellbore through sulfonic acid groups and its macromolecular structure can fill the pores, it can form a dense filter cake on the wellbore, reduce the filtration loss caused by the penetration of the drilling fluid water into the wellbore, and stabilize the drilling fluid system. Lubrication: Its molecular structure can form a lubricating film between the drilling tools and the wellbore. The sulfonic acid groups interact with the surface, and the non-polar parts provide a lubricating interface, reducing the friction of the movement of the drilling tools, and reducing energy consumption and wear.
Anti-collapse: By adsorbing on the rock of the wellbore to change its properties, the sulfonic acid groups chemically adsorb with metal ions to form a protective film, improve the strength and anti-water erosion ability of the rock, and prevent the hydration and expansion of clay minerals from causing the collapse of the wellbore.
