Polyacrylamide is a linear polymer, and its products are mainly divided into dry powder and colloid. According to its average molecular weight, it can be divided into three categories: low molecular weight, medium molecular weight and high molecular weight. According to its structure, it can be divided into non-ionic, anionic and cationic. The main chain of polyacrylamide contains a large number of amides with high chemical properties, which can be modified to prepare various PAM derivatives. Products have been widely used in papermaking, mineral processing, oil extraction, metallurgy, building materials, sewage treatment and other industries. As lubricant, suspending agent, clay stabilizer, oil displacement agent, fluid loss control agent and thickener, amphoteric polyacrylamide (PAM) has been widely used in drilling, acidizing, fracturing, water plugging, cementing, secondary oil recovery and tertiary oil recovery and other fields, is an important oilfield chemical.
PAM polyacrylamide powder plays an important role in changing the rheological properties of liquids, increasing the viscosity of driving fluids, improving the efficiency of water driving waves, and reducing groundwater infiltration.
When polymer flooding is used, the surface additive is flowed and injected into the well in proportion. After the polymer and water are injected, the injected water can move forward to drive out the remaining crude oil in the well fractures, thereby enhancing the recovery rate, which is called tertiary oil recovery. The molecular weight of polyacrylamide for tertiary oil recovery is 10% to 50%, and the relative molecular weight is between hundreds of thousands to several million. Large oil fields have entered the middle and late stages of oil exploitation, and the content of oil and water produced will increase. In order to stabilize oilfield production, tertiary oil recovery technology is widely used to improve oil recovery rate. The polyacrylamide flooding test has achieved a good effect of increasing production.
The polyacrylamide powder produced on the market uses acrylamide as raw material, and is prepared by an aqueous solution polymerization method with an initiator. The monomer concentration, initiator dosage, reaction time, and reaction temperature in the preparation process have a certain influence on the molecular weight of the polymer. The size of the molecular weight directly determines other properties, so it is of great significance to find out the synthesis conditions under different molecular weight ranges. The main polymerization methods of polyacrylamide powder include aqueous solution polymerization, inverse emulsion polymerization, inverse suspension polymerization, micro Emulsion polymerization and precipitation polymerization, etc. The aqueous solution polymerization is the earliest method used in the industrial production of polyacrylamide.
What is the effect of monomer concentration on molecular weight? With the increase of the monomer concentration, the degree of polymer polymerization increases, the viscosity of the product increases, and the molecular weight increases, which is consistent with the free radical polymerization reaction, and the monomer concentration increases again. Due to the increase of the reaction heat, it is not easy to dissipate heat, which leads to the chain transfer reaction speed. increases, the molecular weight decreases. Therefore, the reaction system controls the monomer concentration within 20%.
Most products are colorless and transparent colloids before drying. The determination of the molecular weight of dry powder polyacrylamide is related to its solid content, and the polymer viscosity directly reflects its molecular weight. Some scholars have also studied the relationship between initiator concentration and molecular weight. The results show that the molecular weight increases continuously with the increase of initiator in the range of initiator concentration of 0.05%-0.1%; as the amount of initiator increases, the molecular weight increases. A downward trend, it can be seen that the relationship between the concentration of the initiator and the molecular weight is also very close.