Oil-based Mud Additives

Oil-based muds use crude oil or refined hydrocarbons (e.g., diesel, white oil) as the continuous phase and are thickened by the addition of hydrophobically modified bentonite. The lubricity and fluid loss characteristics of these muds are superior to those of water-based muds, but the toxicity of their base fluids is a particular concern.

In recent years, "green" synthetic hydrocarbons known as synthetic-based muds (SBMs) have been developed. These non-aromatic materials contain easily breakable chemical bonds that facilitate biodegradation, making them suitable for use in environmentally sensitive areas. They are similar to traditional oil-based muds in terms of matrix properties, but due to their aliphatic nature, other chemical additives need to be adjusted accordingly. Although oil-based muds and synthetic-based muds are collectively referred to as oil-based muds, they are generally invert emulsions containing a high proportion of water. The viscosity of such emulsions is provided by the internal phase, which is usually denser using a high-salinity brine (e.g., calcium chloride).

To maintain the stability of invert emulsions, high-performance emulsifiers are required, which are composed of multiple components that optimize performance. One of the main advantages of oil-based mud is that it can keep the reservoir surface wet, thereby inhibiting shale expansion, reducing fluid loss and reducing damage to the production layer. In order to maintain the oil-wet characteristics, wetting agents are also added to the formulation. In addition, commonly used chemical additives include dispersants, lubricants and foaming agents.