Carboxymethyl cellulose CMC is a white flocculent powder with stable performance and is easily soluble in water. The solution is a neutral or alkaline transparent viscous liquid, which is compatible with other water-soluble glues and resins. The product can be used as an adhesive , thickener, suspending agent, emulsifier, dispersant, stabilizer, sizing agent, etc. Carboxymethyl cellulose is used in petroleum and natural gas drilling, well digging and other projects
The role of carboxymethyl cellulose CMC: 1. CMC-containing mud can make the well wall form a thin and firm filter cake with low permeability, reducing water loss. 2. After adding CMC to the mud, the drilling rig can get a low initial shear force, so that the mud can easily release the gas wrapped in it, and at the same time, the debris can be quickly discarded in the mud pit. 3. Drilling mud, like other suspensions and dispersions, has a shelf life. Adding CMC can make it stable and prolong the shelf life. 4. The mud containing CMC is rarely affected by mold, so it is not necessary to maintain a high pH value and use preservatives. 5. Contains CMC as a treatment agent for drilling mud flushing fluid, which can resist the pollution of various soluble salts. 6. CMC-containing mud has good stability and can reduce water loss even if the temperature is above 150°C. CMC with high viscosity and high degree of substitution is suitable for mud with low density, and CMC with low viscosity and high degree of substitution is suitable for mud with high density. The choice of CMC should be determined according to different conditions such as mud type, area, and well depth.
Application of CMC in Drilling Fluid
1. Improved filter loss performance and mud cake quality, improved anti-seize ability.
CMC is a good fluid loss reducer. Adding it to the mud will increase the viscosity of the liquid phase, thereby increasing the seepage resistance of the filtrate, so the water loss will be reduced.
The addition of CMC makes the mud cake dense, tough and smooth, thereby reducing the jamming phenomenon of differential pressure jamming and drilling tool remote movement, reducing the resistance moment to the rotating aluminum rod and alleviating the suction phenomenon in the well.
In general mud, the amount of CMC medium viscous product is 0.2-0.3%, and the API water loss is much reduced.
2. Improved rock carrying effect and increased mud stability.
Because CMC has good thickening ability, in the case of low soil removal content, adding an appropriate amount of CMC is enough to maintain the viscosity required to carry cuttings and suspend barite, and improve the mud stability.
3. Resist the dispersion of clay and help prevent collapse
CMC’s water loss reducing performance slows down the hydration rate of mud shale on the well wall, and the covering effect of CMC long chains on the well wall rock strengthens the rock structure and makes it difficult to peel off and collapse.
4. CMC is a mud treatment agent with good compatibility
CMC can be used in conjunction with various treatment agents in the mud of various systems, and obtains good results.
5. Application of CMC in cementing spacer fluid
The normal construction of well cementing and cement injection is an important part to ensure the quality of cementing. The spacer fluid prepared by CMC has the advantages of reduced flow resistance and convenient construction.
6. Application of CMC in workover fluid
In oil testing and workover operations, if high-solids mud is used, it will cause serious pollution to the oil layer, and it will be more difficult to eliminate these pollutions. If clean water or brine is simply used as workover fluid, some serious pollution will occur. Leakage and filtration loss of water into the oil layer will cause water lock phenomenon, or cause the muddy part in the oil layer to expand, impair the permeability of the oil layer, and bring a series of difficulties to the work.
CMC is used in workover fluid, which can successfully solve the above problems. For low-pressure wells or high-pressure wells, the formula can be selected according to the leakage situation:
Low-pressure layer: slight leakage: clean water +0.5-0.7% CMC; general leakage: clean water +1.09-1.2% CMC; serious leakage: clean water +1.5% CMC.