Polyacrylamide widely used in petroleum industry

Application of polyacrylamide in petroleum industry:

As a multifunctional additive, PAM is used as a thickener, stabilizer and sedimentation flocculant for drilling fluid in the drilling process, and is used to improve the rheology of drilling fluid; improve the size of suspended particles, increase suspension force, and accelerate crude oil filtration and separation . As a soil structure forming agent, it can improve the impact resistance of the surface of the wellbore; when drilling through the opening layer, the drilling fluid that is not easy to disperse can obtain an efficient separation effect. Partially hydrolyzed homopolyacrylamide undergoes methylolation reaction with formaldehyde, glyoxal, etc. to produce products containing methyl groups in side chains, and obtains satisfactory results in crude oil production.

1. Application of polyacrylamide in tertiary oil recovery

The properties of PAM's thickening, flocculation and fluidity regulating effects make it play an important role in oil recovery. It is widely used in drilling, water plugging, acidizing water, fracturing, well washing, well completion, drag reduction, scale prevention and oil displacement, etc. In general, PAM is used to increase oil recovery. In particular, many oil fields have entered into secondary and tertiary recovery, and the reservoir depth is generally above 1000, and some reservoirs have a depth of 7000. Correspondingly, offshore oil production also puts forward new requirements for PAM, requiring it to be resistant to shear force, high temperature (above 100°C to 200°C), 2+, 2+ ions, and seawater degradation.

Among the three methods of improving oil recovery, the use of polyacrylamide as an oil displacement agent occupies an important position. The role of the polymer is to adjust the rheology of the injected water, increase the viscosity of the drive fluid, improve the sweep efficiency of water flooding, reduce the permeability of the water phase in the formation, and enable water and oil to flow forward at a uniform speed. When micelles and polymers are used for oil flooding, surfactants and additives are formulated into microemulsions with ultra-low interfacial tension and injected into the well, then the polymer solution is injected, and finally water is injected. The water is pushed forward in the form of a plunger flow, displacing the residual oil dispersed in the void, and improving the recovery of crude oil. The general concentration of polyacrylamide used for tertiary oil recovery is 10-50%, and the relative molecular weight ranges from hundreds of thousands to more than ten thousand.

2. Polyacrylamide is used as a water blocking regulator

In the process of oil field production, due to the heterogeneity of the formation, water immersion problems often occur, and water plugging is required. In essence, it changes the seepage state of water in the formation to reduce water production in the oilfield, maintain formation energy, and improve oilfield performance. purpose of ultimate recovery. Polyacrylamide chemical water blocking agent has the selectivity of the permeability of oil and water, the permeability of oil can be reduced by more than 10%, and the permeability of water can be reduced by more than 90%.

The feature of selective water shutoff is not found in other water shutoff agents. Usually, the appropriate molecular weight of polyacrylamide is selected according to the formation type. For oil layers with good homogeneity and high average permeability, polyacrylamide with a relative molecular mass of 5-7 million can be selected; for fractured oil layers with low bedrock permeability or oil layers with large permeability changes, a high relative molecular mass of 1000 can be selected. More than ten thousand polyacrylamide. Polyacrylamide can be used without crosslinking, but it can be used with aluminum salts, chromium salts, zirconium salts, etc. temperature resistance. This method has been applied in water plugging in domestic carbonate bottom water reservoirs with high water cut, and has achieved remarkable results. The use of polyacrylamide can also adjust the water absorption profile in the formation and block large pores, and good results have been achieved in practice.

3. Polyacrylamide is used as drilling fluid regulator and fracturing fluid additive

As a drilling fluid conditioner, partially hydrolyzed polyacrylamide is often used, which is obtained by hydrolysis of polyacrylamide. Its role is to adjust the rheology of drilling fluid, carry cuttings, lubricate the drill bit, reduce fluid loss, etc. Drilling fluid prepared with polyacrylamide has a low specific gravity, which can reduce the pressure and blockage of oil and gas layers, make it easier to find oil and gas layers, and facilitate drilling. The drilling speed is 19% higher than conventional drilling fluids, and about 45% higher than the mechanical drilling speed. In addition, it can greatly reduce pipe sticking accidents, reduce equipment wear, and prevent lost circulation and collapse.

Fracturing technology is an important stimulation measure for oilfield development of tight formations. The fracturing fluid made of cross-linked methylene polyacrylamide has high viscosity, low friction, good sand suspension ability, low fluid loss, good viscosity stability, less residue, wide supply, convenient preparation and low cost. low and widely used.

In fracturing and acidizing treatment, polyacrylamide is formulated into an aqueous solution with a concentration of 0.01%-4%, and pumped into the downhole formation to fracture the formation. The polyacrylamide aqueous solution has the function of thickening and carrying sand and reducing the loss of fracturing fluid. Moreover, polyacrylamide has a drag-reducing effect, so it can reduce the pressure transmission loss.

4. Polyacrylamide is used as oil well cement admixture

The terpolymer prepared by AMPS, methacrylic acid and acrylamide is suitable for various brine drilling fluids and has good high temperature retarding effect. The copolymer of AMPS and acrylic acid introduced by Halliburton Company of the United States, the compound composed of the copolymer of AMPS and N,N-dimethylpropionamide and carboxymethyl hydroxyethyl cellulose can be used as oil well cement admixture, which can effectively reduce water drilling The high temperature filtration loss of the liquid.

5. Polyacrylamide is used as drilling fluid treatment agent

Graft copolymer of AMPS and acrylamide and starch, copolymer of AMPS and acrylamide and N, N-dimethylacrylamide, graft copolymer of AMPS and humic acid and acrylamide in freshwater drilling fluid, salt water drilling Fluid, saturated brine drilling fluid and seawater drilling fluid all have good fluid loss control, temperature resistance and salt resistance.

Pollution caused by clay dispersion and other factors often causes the viscosity of the drilling fluid to increase. At this time, a viscosity reducer is needed to control the rheology of the drilling fluid. The most commonly used drilling fluid viscosity reducer is iron chromium lignin sulfur salt viscosity reducer. The terpolymer of AMPS, acrylic acid and methacrylic acid is used as a drilling fluid viscosity reducer to replace it, which not only retains good salt resistance and temperature resistance, but also overcomes its toxicity. Studies have shown that terpolymers are more resistant to high-valent metal ions than binary copolymers.

6. Polyacrylamide is used as an additive for completion fluid and workover fluid

The copolymer of AMPS, acrylic acid and itaconic acid can be used as a viscosifier for preparing seawater and brine, which can increase the viscosity of completion fluid by more than 4 times, and has good thermal stability, which overcomes the traditional polymer in brine system. Disadvantage of viscosity drop.