Carboxymethylcellulose (CMC) has important applications in oil drilling. Here are some of its main uses:

1. Reduce filtration loss and mud cake thickness: CMC can significantly reduce filtration loss and thin the mud cake thickness in drilling fluids with low solid phase and no solid phase.

2. Enhance mud stability: CMC can form a stable suspension system for mud and maintain good stability even at high temperatures.

3. Prevent mud pollution: CMC can resist the pollution of various soluble salts, so it can effectively prevent mud pollution during the drilling process.

4. Improve drilling efficiency: CMC can form a thin, hard, low-permeability filter cake on the well wall, thereby reducing water loss and improving drilling efficiency.

5. Prevent the influence of mold: Mud containing CMC is rarely affected by mold, so there is no need to maintain a high pH value or use preservatives

In general, the application of CMC in oil drilling is mainly to improve the drilling effect by improving the performance of the mud, increasing the drilling efficiency and reducing the pollution of the mud.