Polyanionic cellulose (PAC) is a water-soluble polymer widely used in the petroleum industry as a drilling fluid additive. It is a polyanionic derivative of cellulose, synthesized by chemical modification of cellulose with carboxymethyl. PAC has excellent properties such as high water solubility, thermal stability, and hydrolysis resistance. These properties make PAC an ideal additive for drilling fluid systems in petroleum exploration and production.
The application of PAC in oil drilling is mainly due to its ability to control the viscosity and filtration properties of drilling fluids. Viscosity control is a critical factor in drilling operations as it affects drilling efficiency and safety. The use of PAC helps stabilize the viscosity of the drilling fluid, which is very important for maintaining the flow properties of the drilling fluid. The viscosity of the drilling fluid is controlled by the concentration of PAC used and the molecular weight of the polymer. The PAC molecule acts as a thickener, or viscosifier, because it increases the viscosity of the drilling fluid. The viscosity of drilling fluid depends on PAC concentration, degree of substitution and molecular weight.
Filtration control is another critical factor in drilling operations. Filtration performance is related to the rate at which fluid invades the well wall during drilling. Using PAC helps improve filtration control and reduce liquid intrusion. Fluid intrusion can lead to loss of circulation, formation damage and reduced drilling efficiency. Adding PAC to the drilling fluid creates a gel-like structure that acts as a filter cake on the well walls. This filter cake reduces fluid intrusion, helping to maintain the integrity of the wellbore and reducing the risk of formation damage.
PAC is also used to improve the shale suppression properties of drilling fluids. Shale suppression is the ability of a drilling fluid to prevent reactive shale from hydrating and swelling. Hydration and expansion of reactive shale can lead to problems such as wellbore instability, pipe stuck, and lost circulation. Adding PAC to the drilling fluid creates a barrier between the shale and the drilling fluid. This barrier helps maintain the integrity of the well wall by reducing hydration and swelling of the shale.
Another application of PAC in oil drilling is as a water loss reduction additive. Filtration loss refers to the loss of drilling fluid entering the formation during drilling. This loss can lead to formation damage, lost circulation and reduced drilling efficiency. The use of PAC helps reduce fluid losses by creating a filter cake on the well walls that blocks fluid flow into the formation. Reduced fluid loss helps maintain wellbore integrity and improves drilling efficiency.
PAC can also be used to improve the wellbore stability of drilling fluids. Wellbore stability refers to the ability of drilling fluid to maintain wellbore stability during drilling. The use of PAC helps stabilize the well wall by forming a filter cake on the well wall. This filter cake reduces fluid intrusion into the wall and reduces the risk of wellbore instability.
The use of polyanionic cellulose in oil drilling offers many benefits. PAC is used to control the viscosity and filtration performance of drilling fluid, improve shale inhibition performance, reduce filtration loss, and improve wellbore stability. The use of PAC in oil drilling helps increase efficiency and reduces the risk of formation damage, lost circulation and wellbore instability. Therefore, the use of PAC is critical to the success of oil drilling and production.
Post time: Oct-08-2023