Application of PAC ( Polyanionic Cellulose ) in Oil Drilling Fluid
Due to excellent thickening, stabilizing, suspending properties and resistance to high temperature, PAC is widely used in the oil drilling fluid.
Polyanionic Cellulose is more suitable for offshore drilling and the functions of Polyanionic Cellulose in drilling fluid are listed as below.
1). The drilling mud is the suspended matter of solids in the aqueous solution, and the same as other colloidal suspension dispersions, so has a certain life period. Polyanionic Cellulose can keep it stable and then prolong its life period. It has more obvious effects especially in mud suspension dispersions with dissolving salt.
2). The drilling mud with Polyanionic Cellulose can form thin and solid shaft wall as well as filter cake with low permeability, and thus can reduce the hole shrinkage and collapse phenomena resulting from water loss of mud.
3). The mud with the addition of Polyanionic Cellulose is seldom affected by mycete, so it doesn’t need to maintain high pH value or use preservatives. It can still keep stable with corresponding decrease of the usage amount of other chemical agents, or even within a certain range of temperature variation during the drilling process.
4). The mud with Polyanionic Cellulose enables the drilling machine to obtain low initial gel strength, so the mud can discharge air in it easily and discard debris in a mud pit quickly. PAC-HV applies to the mud with smaller proportion and a small usage amount can increase viscosity and reduce fluid loss. A small amount of Polyanionic Cellulose can replace a lot of clay and this kind of mud can reduce the difficulties resulting from encountering CaSO42H20 or CaSO4 salt belt during drilling process. However, PAC-LV applies to the mud with larger proportion, can reduce the fluid loss but have little effect on the viscosity. In use, Polyanionic Cellulose should be dissolved in water to prepare the solution (usually 1/40-1/20) and then add into the mud. Polyanionic Cellulose can also be compounded with other chemical agents to add into the mud.
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