Polyanionic cellulose (PAC) is a common drilling fluid treatment agent with the functions of viscosity increase and filtration loss reduction. The following is its addition and configuration method in drilling fluid:
1. Preparation: First, prepare clean mixing equipment, such as a high-speed mixer, to ensure that it can operate normally to ensure that polyanionic cellulose can be fully dispersed and dissolved. At the same time, prepare a base fluid that meets the requirements. The base fluid is generally fresh water or brine configured according to actual needs. The water quality should meet the standards for drilling fluid preparation to avoid excessive impurities that affect the performance of polyanionic cellulose.
2. Determine the amount of addition: The amount of addition is determined based on the performance requirements of the drilling fluid, the formation conditions, and the drilling process. Generally speaking, in freshwater drilling fluid, the amount of polyanionic cellulose added is usually between 0.3% and 1.0% (mass fraction); in brine or saturated brine drilling fluid, the amount may be appropriately increased, generally around 0.5% to 1.5% (mass fraction). However, the specific amount needs to be adjusted through indoor experiments and actual conditions on site.
3. Dry mixing method: slowly and evenly sprinkle the calculated amount of polyanionic cellulose into the stirring base liquid. In order to prevent the polyanionic cellulose from agglomerating, the spreading speed should not be too fast, and it should be stirred while spreading. The stirring speed is generally controlled at 1000-2000 rpm. The stirring time depends on the dissolution of the polyanionic cellulose. It is usually necessary to continue stirring for 30 minutes to 2 hours until it is completely dissolved and the solution is uniform and free of agglomerates.
4. Prehydration method: first prehydrate the polyanionic cellulose with a certain amount of fresh water in a smaller container. According to the ratio of polyanionic cellulose to water of 1:10 to 1:20 (mass ratio), slowly add the polyanionic cellulose to water under stirring conditions and stir for 30 minutes to 1 hour to make it initially swell to form a paste. Then slowly add the pre-hydrated paste to the stirring drilling fluid base fluid, and continue stirring for 30 minutes to 1 hour to fully disperse and dissolve the polyanionic cellulose in the drilling fluid.
5. Post-configuration treatment: After the polyanionic cellulose is added and configured, the performance of the drilling fluid needs to be tested, such as viscosity, shear force, filtration loss, etc. According to the test results, if necessary, the content of polyanionic cellulose or the amount of other treatment agents added can be adjusted to meet the requirements of drilling construction. At the same time, the configured drilling fluid should be properly stored to avoid pollution and environmental factors such as temperature and pH value.
When using polyanionic cellulose to configure drilling fluid, operators should strictly follow the operating procedures, take personal protection, and avoid inhaling dust or contact with skin and eyes.
