1.Introduction

Polyacrylamide (PAM for short) is an important water-soluble high-molecular polymer. Due to its excellent thickening property, flocculation property and rheological regulation performance, it is widely used in the field of oil and gas extraction. In the development of oil and gas fields, PAM is mainly used in key links such as enhancing crude oil recovery (EOR), optimizing drilling fluids, thickening fracturing fluids and wastewater treatment. This article will explore in detail the mechanism of action, application scenarios and future development trends of PAM in oil and gas fields.

2.The main role of PAM in oil and gas fields

2.1 Enhanced Crude Oil Recovery (EOR)

In the middle and later stages of oilfield development, the fluidity of crude oil in the formation decreases, and it is difficult for conventional oil extraction methods to effectively extract the remaining oil. As a polymer oil displacement agent, PAM can enhance the oil recovery rate in the following ways:

Increasing the viscosity of the aqueous phase: PAM solution has a relatively high viscosity, which can reduce the water-oil flow ratio, decrease the "finger penetration" phenomenon, and improve the oil displacement efficiency.

Improving ripple efficiency: PAM solution can seal the high-permeability layer, forcing the displacement liquid to enter the low-permeability layer and expanding the ripple volume.

Microscopic oil displacement effect: PAM molecules can reduce the interfacial tension between oil and water, promoting the stripping and migration of residual oil droplets.

Application cases: Daqing Oilfield, Shengli Oilfield and others have adopted partially hydrolyzed polyacrylamide (HPAM) for polymer flooding, increasing the recovery rate by 10% to 20%.

2.2 Drilling Fluid Additives

During the drilling process, PAM, as a drilling fluid treatment agent, mainly plays the following roles:

Lubrication and drag reduction: Reduce the friction between the drill bit and the wellbore to enhance drilling efficiency.

Stabilizing the wellbore: By adsorbing onto the surface of clay particles, it inhibits the hydration and expansion of shale and prevents the collapse of the wellbore.

Control the filtration loss: PAM can form a dense filter cake, reducing the filtration loss of drilling fluid into the formation.

Common types:

Nonionic PAM (NPAM) : It has good salt resistance and is suitable for high mineralization strata.

Anionic PAM (APAM) : Suitable for freshwater or low-salinity drilling fluid systems.

2.3 Fracturing fluid thickener

In the development of shale oil and gas and tight reservoirs, hydraulic fracturing is a key means to increase production. PAM, as a thickener for fracturing fluid, can:

Enhance sand-carrying capacity: Increase the viscosity of the fracturing fluid to ensure that proppants (such as quartz sand) are effectively transported deep into the fractures.

Reducing friction: The drag reduction performance of PAM can reduce pipeline pressure loss and improve fracturing efficiency.

Controllable degradation: Some cross-linked PAM can break the gel after fracturing, reducing formation damage.

Application trend: In recent years, hydrophobic associative polyacrylamide (HAPAM) has been widely used in high-temperature and high-pressure reservoirs due to its temperature and salt resistance.

2.4 Oil and Gas Field Wastewater Treatment

The produced water from oil and gas fields contains a large amount of suspended solids, oils and chemical agents. PAM is used as a flocculant in:

Oil-water separation: Through electro-neutralization and adsorption bridging effects, tiny oil droplets coalesce, facilitating separation.

Sludge dewatering: When compounded with inorganic flocculants (such as PAC), it enhances the efficiency of sludge settling and dewatering.

Reinjection water treatment: Ensure that the reinjection water meets the standards of low solid phase and low oil content to prevent formation blockage.

Common types:

Cationic PAM (CPAM) : Suitable for oily wastewater and sludge dewatering.

Amphoteric PAM: Adaptable to complex water quality conditions.

3.Challenges of PAM Application in Oil and Gas Fields

Although PAM is widely used in oil and gas fields, the following challenges are still faced:

Insufficient temperature and salt resistance: Conventional HPAM is prone to degradation in high-temperature (>80℃) or highly mineralized strata.

Mechanical shear degradation: Under high-speed injection or formation shear action, molecular chains are prone to breakage, reducing the viscosity-increasing effect.

Biological stability issue: Microorganisms can degrade PAM, which affects the long-term oil displacement effect.

Solution:

Develop high-temperature and salt-resistant PAM types (such as hydrophobic modified and nano-composite PAM).

Polymer cross-linking techniques (such as chromium cross-linking and organometron cross-linking) are adopted to enhance stability.

4.Future Development Trends

Intelligent responsive PAM: such as pH/ temperature-sensitive PAM, which can adapt to the formation environment independently.

Nano-reinforced PAM: By adding nanoparticles such as SiO₂ and TiO₂, the temperature resistance and shear resistance are enhanced.

Green and environmentally friendly PAM: bio-based PAM or degradable PAM, reducing environmental burden.

5.Conclusion

Polyacrylamide (PAM) plays an irreplaceable role in the development of oil and gas fields, demonstrating outstanding performance from enhanced oil recovery to wastewater treatment. In the future, with the research and development of new PAM materials, their application in unconventional oil and gas (such as shale gas and tight oil) will further expand, providing key technical support for the sustainable development of the petroleum industry.