With the development of drilling fluid technology, asphalt modified products are widely used in oil drilling. The commonly used modified asphalt treatment agents in oil fields include emulsified asphalt, oxidized asphalt, sulfonated asphalt and so on.
The emulsified asphalt refers to the oil-in-water type (O / W) emulsion formed in the asphalt aqueous solution containing the emulsifier and other additives under the mechanical stirring force.
According to the different electrical properties of emulsifier, it can be divided into cationic emulsified asphalt, anionic emulsified asphalt, non-ionic emulsified asphalt and so on.Emulsified asphalt is often used as anti-collapse and plugging agent in drilling engineering to improve the quality of mud cake, seal formation pores and cracks, and reduce the filtration loss of drilling fluid.Due to the negative charge of clay particles, cationic emulsified asphalt is used in oil field to inhibit clay swelling.
At present, a large number of studies on the performance of cationic emulsified asphalt to prevent collapse, reduce filtration loss and inhibit clay swelling have proved that has a good anti-collapse and plugging effect.And only 2% concentration of cationic emulsified asphalt can significantly reduce the filtration loss of drilling fluid.
The effect of the addition of cationic emulsified asphalt on the rheology of drilling fluid is as follows.
(1) Cationic emulsified asphalt can have a small impact on the rheological properties of drilling fluid.When the concentration is below 4%, the apparent viscosity of drilling fluid fluctuates with the increase of the concentration, but the fluctuation range is small.The changes of plastic viscosity and dynamic shear force also fluctuate also in a small range with the increase of concentration.
(2) When temperature between 45 ℃ and 75 ℃, and the concentration of cationic emulsified asphalt in drilling fluid is below 4%, whether add cationic emulsified asphalt or not, the apparent viscosity of drilling fluid decreases with the rise of temperature, and the plastic viscosity and dynamic shear force change greatly at the higher temperature of 65 ℃ and 75 ℃.With the increase of temperature, the influence of cationic emulsified asphalt on the rheology of drilling fluid will gradually decrease
