A drilling-fluid additive used primarily for fluid-loss control, manufactured by reacting natural cellulose with monochloroacetic acid and sodium hydroxide[NaOH] to form CMC sodium salt. Up to 20 wt % of CMC may be NaCl, a by-product of manufacture, but purified grades of CMC contain only small amounts of NaCl. To make CMC, OH groups on the glucose rings of cellulose are ether-linked to carboxymethyl (-OCH₂-COO^–) groups. (Note the negative charge.) Each glucose ring has three OH groups capable of reaction, degree-of-substitution = 3. Degree of substitution determines watersolubility and negativity of the polymer, which influences a CMC’s effectiveness as a mud additive. Drilling grade CMCs used in muds typically have degree-of-substitution around 0.80 to 0.96. Carboxymethylcellulose is commonly supplied either as low-viscosity (“CMC-Lo Vis”) or high-viscosity (“CMC-Hi Vis”) grades, both of which have API specifications. The viscosity depends largely on the molecular weight of the starting cellulose material.

1.Adding the Carboxymethyl cellulose into the slurry, it can help slurry to form a thin, strong and ow permeability filter cake in the well, to reduce water loss.
2. Adding the Carboxymethyl cellulose into the slurry, it can easy to release the gas in the slurry, and keep the debris in the pit quickly.
3.The drilling slurry also have existence of time same as other suspension. , after adding CMC to make it stable and to extend the lifespan. 4. The slurry which containing Carboxymethyl cellulose will little affected by the mold, so there are no need preservatives additive and maintaining a high PH value
5. Carboxymethyl cellulose can anti-pollution of a variety of soluble salts in the pit as flushing fluid drilling.
6. The slurry which containing Carboxymethyl cellulose has very good stability, it still reduce water loss even the temperature is above 150 ℃. To choose which kinds of Carboxymethyl cellulose can use in oil drilling, should be based on the slurry type, the region, the depth and other different conditions. High viscosity, high degree of substitution of Carboxymethyl cellulose should use in the low slurry density. for density of the slurry should use low viscosity, high degree of substitution of Carboxymethyl cellulose.