Application of Polyacrylamide in Oilfield Drilling

Application of Polyacrylamide in Oilfield Drilling

          Polyacrylamide is a multifunctional oilfield chemical treatment agent widely used in drilling, cementing, completion, well repair, fracturing, acidification, water injection, water plugging and profile control, and tertiary oil recovery operations, especially in the fields of drilling, water plugging and profile control, and tertiary oil recovery.

              Polyacrylamide aqueous solution has high viscosity, good thickening, flocculation, and rheological adjustment effects, and is used as an oil displacement agent and drilling mud regulator in petroleum extraction.

             In the middle and later stages of oil extraction, polymer flooding and ternary composite flooding technologies are mainly promoted to improve crude oil recovery. By injecting polyacrylamide aqueous solution, the oil water flow ratio is improved, resulting in an increase in the crude oil content in the extracted material.

             Adding polyacrylamide to tertiary oil recovery can increase oil displacement capacity, avoid oil layer breakdown, and improve oil recovery rate.

          The petroleum industry is a large user of polyacrylamide, and the technological progress of polyacrylamide has promoted the development of the petroleum industry. The demand of the petroleum industry has accelerated the pace of technological innovation and industry development of polyacrylamide.

1. Oil extraction

According to statistics, about 31% of polyacrylamide is used in oil fields in the United States, while it accounts for over 60% in China. Polyacrylamide is an additive with multiple functions in oil field chemicals, such as drilling fluid, flushing fluid, water injection oil recovery, and enhanced oil recovery. The key lies in the combination of usage conditions, requiring reasonable design and selection of polyacrylamide varieties (including dosage form, molecular weight, ionicity, etc.).

For example, non-ionic polyacrylamide and cross-linking agent can form gel through oxidation reduction reaction, which can be used as water shutoff agent for oil wells; Anionic polyacrylamide is used as an additive in drilling mud due to its excellent thickening and flocculation effects.

Used in geology and oil drilling to regulate mud properties, it has a special effect on resisting water sensitive formations and preventing wellbore collapse. In addition, utilizing the shear orientation of polyacrylamide linear macromolecules in flowing fluids, they can easily grow into straight strips under turbulent conditions and in the direction of flow. Polyacrylamide, as a friction reducing agent, is an ideal material to resist turbulent flow. For example, in long-distance pipeline transportation of crude oil, adding polyacrylamide with a molecular weight of over 10 million, equivalent to 0.1 PPM of crude oil, can greatly reduce the resistance and energy consumption during the transportation process.

2. Used as a degreaser

Among the three methods of improving oil recovery, using polyacrylamide as a degreaser plays an important role. The function of polymers is to regulate the rheological properties of injected water, increase the viscosity of the driving fluid, improve the efficiency of water flooding, reduce the water phase permeability in the formation, and enable water and oil to flow forward at a uniform speed.

 When micellar polymer is used for oil displacement, the microemulsion with ultra-low interfacial tension prepared by surfactant and assistant is injected into the water injection well first, and then polymer solution is injected into the water injection well. Water flows forward as a plunger. Displacement of residual oil dispersed in pores to improve the recovery rate of crude oil.

Due to the fact that the polyacrylamide used in Sancai generally contains 10% -50% basis weight, with molecular weights ranging from several hundred thousand to over ten million. This is a very active research field that has developed many modified polymers. In the later stage of large-scale oil field exploitation, the water content of the extracted oil is increasing day by day. In order to stabilize oilfield production, the use of tertiary oil recovery technology can improve oil recovery rate and ensure stable production of the oilfield.

3. Used as a water blocking and adjusting agent

In the production process of oil fields, due to the heterogeneity of the formation, water immersion problems often occur, requiring water plugging. Its essence is to change the flow state of water in the formation, achieving the goal of reducing water production, maintaining formation energy, and improving oil field recovery.

Polyacrylamide chemical water plugging agent has developed rapidly, with a large dosage and selective ability to penetrate oil and water. Its permeability to oil can be reduced by more than 10%, while its permeability to water can be reduced by more than 90%. The characteristic of selective water blocking is not found in other water blocking agents. Usually, the appropriate molecular weight of polyacrylamide is selected based on the type of formation. 

For oil reservoirs with good homogeneity and high average permeability, medium molecular weight polyacrylamide can be selected; High molecular weight polyacrylamide can be used for fractured oil layers with low rock permeability or oil layers with large permeability changes. Polyacrylamide can not be cross-linked in use, but can also be cross-linked with aluminum salt, chromium salt, etc. to form gel. Some resins can also be added to form a mutually soluble polymer network, so that it has higher temperature resistance. This method has been applied to water plugging in high water cut oil fields with carbonate bottom oil layers and has achieved significant results. The use of polyacrylamide can also adjust the water absorption surface and seal large openings in the absorption layer, and good results have been seen in practice.

4. Used as an additive for fracturing fluid

Fracturing technology is an important measure for increasing production in the development of tight layers in oil fields. Its function is to open up the passage of rocks, allowing oil to flow through. The fracturing fluid, which is cross-linked with methylene polyacrylamide, is widely used due to its high viscosity, low friction, good sand suspension ability, convenient configuration, and low cost advantages.