Chapter 1 - Drilling Muds

Abstract

This chapter discusses classification of drilling muds. The classification of drilling muds is based on their fluid phase alkalinity, dispersion, and the type of chemicals used in their formulation. Drilling muds are usually classified as either WBMs or OBMs, depending upon the continuous phase of the mud. However, waterbased drilling muds (WBMs) may contain oil and oil-based drilling muds (OBMs) may contain water. OBMs generally use hydrocarbon oil as the main liquid component, with other materials such as clays or colloidal asphalts being added to provide the desired viscosity together with emulsifiers, polymers, and other additives including weighting agents. Water may also be present, but in an amount not usually greater than 50% by volume of the entire composition. If more than about 5% of water is present, the mud is often referred to as an invert emulsion. WBMs conventionally contain viscosifiers, fluid loss control agents, weighting agents, lubricants, emulsifiers, corrosion inhibitors, salts, and pH control agents. Water makes up the continuous phase of the mud, and is usually present as at least 50 volume percent of the entire composition. Oil is also usually present in small amounts, but will typically not exceed the amount of the water, so that the mud will retain its character as a water-continuous-phase material.