Polyanionic cellulose (PAC) is a common drilling fluid additive with thickening and filtration loss reduction effects. The following is the general preparation method and steps of polyanionic cellulose drilling fluid:
1. Prepare equipment and materials: prepare containers (such as mixing tanks), mixing equipment (such as electric stirrers), measuring instruments (such as measuring cylinders, electronic scales), as well as polyanionic cellulose, water (fresh water or salt water, etc. according to actual conditions), and other additives that may be needed (such as soda ash, etc., for adjusting pH value and improving performance).
2. Calculate the dosage: According to the required drilling fluid performance requirements and formula, accurately calculate the dosage of polyanionic cellulose and other additives. Generally speaking, the amount of polyanionic cellulose added to the drilling fluid is usually around 0.3% - 1.0% (mass fraction), and the specific dosage needs to be determined according to actual conditions.
3. Add water and pre-mix: Add the required amount of water to the mixing tank, turn on the mixing equipment, and pre-mix at a lower speed (such as 300-500 rpm) to form a certain vortex in the water, creating good mixing conditions for the subsequent addition of additives.
4. Slowly add polyanionic cellulose: Slowly and evenly sprinkle the calculated amount of polyanionic cellulose into the mixing tank to avoid agglomeration. It can be added in small amounts and multiple times to ensure that the polyanionic cellulose can be fully dispersed in the water. During the addition process, keep the mixing equipment running normally.
5. High-speed stirring and dissolving: After the polyanionic cellulose is added, increase the stirring speed (such as 1000-1500 rpm) and continue stirring for 30 minutes to 1 hour to fully dissolve and hydrate the polyanionic cellulose to form a uniform solution. At this time, the viscosity of the drilling fluid will gradually increase.
6. Add other additives: According to the formula requirements, add other additives in sequence, such as soda ash (generally added in an amount of 0.1%-0.5%), etc. During the addition process, pay attention to the changes in the performance of the drilling fluid and make appropriate adjustments if necessary. After each additive is added, continue to stir for a period of time (generally 10-20 minutes) to ensure that it is fully mixed and effective.
7. Performance adjustment and testing: Use measuring instruments to test the performance of the prepared drilling fluid, such as measuring its viscosity, shear force, filtration loss, pH value, etc. According to the test results, adjust the performance of the drilling fluid. For example, if the viscosity is low, the amount of polyanionic cellulose can be appropriately increased; if the filtration loss does not meet the requirements, a filtration reducer can be added.
8. Circulation and aging: Circulate the prepared and adjusted drilling fluid in the mixing tank to further mix it evenly. Then, let the drilling fluid age for a period of time (generally 4-24 hours) to allow the polyanionic cellulose and other additives to fully play their role and make the drilling fluid performance more stable.
When preparing polyanionic cellulose drilling fluid, it should be strictly followed in accordance with the operating procedures, pay attention to safety, and avoid contact between additives and skin and eyes. At the same time, the drilling fluid formula and performance parameters should be reasonably adjusted according to the actual drilling conditions and formation conditions.
