Application of polyacrylamide in the petroleum industry

Polyacrylamide is a linear water-soluble polymer compound with high relative molecular weight and good water solubility. It is the most widely used water-soluble polymer compound. In petrochemicals, polyacrylamide (PAM) is a multifunctional additive that plays an important role in drilling fluid, well washing fluid, water injection and oil recovery.

It is mainly reflected in the following five applications:

1. Application of polyacrylamide in tertiary oil recovery
PAM's thickening, flocculation and rheological properties of fluids play an important role in oil recovery. It is widely used in drilling, water plugging, acidification, fracturing, well washing, completion, drag reduction, scale prevention and oil recovery. In general, the use of PAM is to improve the recovery rate of oil.

In the tertiary oil recovery method of improving oil recovery, the role of polyacrylamide is to adjust the rheology of injected water, increase the viscosity of the drive fluid, improve the frequency of water drive sweep, reduce the permeability of the water phase in the formation, and enable water and oil to flow forward at a uniform speed. Polymer flooding is to increase the viscosity of injected water and improve the oil-water mobility ratio by adding a certain amount of high molecular weight polyacrylamide to the injected water. Due to the adsorption and complementation of polyacrylamide molecules by the oil layer, the permeability of high and medium permeability layers or high and medium water-flooded layers is reduced, the penetration resistance of the injected water is increased, and the water absorption of low permeability layers or low but not water-flooded layers is increased, the scope of the injected water on the oil layer plane and the water-flooding thickness in the vertical direction of the oil layer are expanded, thereby expanding the water-flooding volume, displacing the unused crude oil during water flooding, and achieving the purpose of improving crude oil recovery. On average, each ton of PAM can increase crude oil production by 179.7 tons.

In the field of oil fields, newer anionic and cationic PAM can be used to protect the injected groundwater from penetrating from the core hole and gathering and recovering crude oil, improve the economic efficiency of oil well production, and control the infiltration of water into the oil layer.

2. Polyacrylamide as a water plugging agent
During the production process of oil fields, due to the heterogeneity of geology, water immersion problems often occur, and water plugging is required. The essence is to change the seepage state of water in the formation to achieve the purpose of reducing oil field water production, maintaining formation energy, and improving the final recovery rate of the oil field. Polyacrylamide chemical water plugging agents have selectivity for the permeability of oil and water. The permeability to oil can be reduced by up to 10%, while the permeability to water can be reduced by more than 90%. The feature of selective water plugging is not available in other water plugging agents. Usually, the appropriate relative molecular weight of polyacrylamide is selected according to the formation type. For oil layers with good homogeneity and high average permeability, polyacrylamide with medium relative molecular weight (5 million to 7 million) can be selected; for fractured oil layers with low bedrock permeability or oil layers with large permeability changes, polyacrylamide with high relative molecular weight (more than 10 million) can be selected.

Polyacrylamide can be used without crosslinking, but it can be crosslinked with aluminum salts, chromium salts, zirconium salts, etc. to form gels. Some resins can also be added to form a mutually soluble polymer network to make it more temperature resistant. PAM can also be used to adjust the water absorption profile in the formation and block large pores, and good results have been achieved in practice.

3. Polyacrylamide as a drilling fluid adjuster
As a drilling fluid adjuster, partially hydrolyzed polyacrylamide (HPAM) is often used, which is obtained by hydrolysis of polyacrylamide. Its function is to adjust the rheology of the drilling fluid, carry cuttings, lubricate the drill bit, reduce fluid loss, etc. The drilling fluid prepared with PAM has a low specific gravity, which can reduce the pressure and blockage on the oil and gas layer, make it easy to find the oil and gas layer, and is conducive to drilling. The drilling speed is 19% higher than that of conventional drilling fluid and about 45% higher than that of mechanical drilling speed. In addition, it can greatly reduce drill jam accidents, reduce equipment wear, and prevent well leakage and collapse.

4. Polyacrylamide as a fracturing fluid additive
Fracturing technology is an important measure to increase production in the development of dense layers in oil fields. Fracturing fluids made of cross-linked methylene polyacrylamide are widely used due to their high viscosity, low friction, good sand suspension capacity, low filtration loss, good viscosity stability, less residue, wide supply, convenient configuration and low cost.

During the fracturing and acidizing process, polyacrylamide is configured into an aqueous solution with a concentration of 0.01%-4%, pumped into the underground formation to fracture the formation. The polyacrylamide solution has the effect of thickening and carrying sand and reducing the loss of fracturing fluid. At the same time, polyacrylamide also has a drag-reducing effect, thereby reducing the transmission loss of pressure.

5. Polyacrylamide as an oilfield water treatment agent
Polyacrylamide and its derivatives are an important class of synthetic organic polymer flocculants. Compared with traditional inorganic flocculants, polyacrylamide has the advantages of a wide variety, high flocculation efficiency and less mud residue. It can be used as a flocculant, sludge dehydrating agent and anti-scaling agent for oilfield sewage treatment.