Calcium reducers are using in drilling fluid that utilize dissolved Ca+2 as a component. Examples are lime mud, gyp mud and calcium chloride [CaCl2] mud. The latter is rarely used, but is based on solutions of CaCl2 that, in high concentration, can impart density. Calcium chloride (CaCl2), a cost-effective mud additive, has good inhibitive capacity suitable for shale/clay-stone drilling, and its solution has low activity. Drilling fluid mixed with calcium chloride, however, has rheology and filtration rate that are difficult to manipulate, and is easy to foam.
To solve these problems, Alkyl polyglucoside (APG) was introduced into the CaCl2 drilling fluid. By analyzing water activity of the CaCl2-APG drilling fluid, and testing on artificial cores, the concentration of CaCl2 needed that is best for borehole stabilization was determined. Using suitable viscosifiers, filtration reducers and defoamers, a CaCl2-APG drilling fluid that can be used at 130℃. was developed, with good inhibitive capacity and lubricity.