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Application of polyacrylamide in oil fields

    Polyacrylamide (PAM for short) is not only a high-efficiency flocculant, but also an extremely excellent thickener because of its high viscosity. PAM can be used as a multi-purpose additive in oilfield oil exploitation due to thickening, flocculation and convection regulation, such as drilling fluid, fracturing fluid, and polymer flooding to enhance oil recovery ( EOR). In oil exploitation, the key to the application lies in the combination of the conditions and requirements, and the rational design and selection of its constituent structures, such as molecular morphology, molecular weight, ionicity, etc., and the correct construction process.
I. PAM is used as a drilling fluid additive
    Drilling fluid is used as a drilling mud performance regulator in petroleum exploration. The role of PAM is to regulate the rheology of the drilling fluid, carry the cuttings, and lubricate the drill bit for the benefit of drilling. In addition, it can greatly reduce stuck accidents, reduce equipment wear, and prevent the occurrence of lost circulation and collapse, so that the diameter of the well rules. Often used in this regard are partially hydrolyzed polyacrylamides, polyacrylamide potassium salts, which are obtained by hydrolysis of PAM or polypropylene.
    Second, PAM is used as polymer flooding
    Among the methods for improving oil recovery, polymer flooding technology plays an important role. The role of the polymer is to adjust the rheology of the injected water, increase the viscosity of the driving liquid, improve the water flooding efficiency, reduce the water phase permeability in the formation, and allow the water and oil to flow forward at a constant speed.
    Polymer flooding is to increase the viscosity of the injected water by adding a certain amount of high molecular weight polyacrylamide to the injected water to improve the oil-water mobility ratio. Due to the adsorption and trapping effect of the oil layer on the polyacrylamide molecules, the permeability of the high and medium permeable layers or the high and middle water-flooded layers is reduced, and the seepage resistance of the injected water is increased, so that the low-permeability layer is low or not. The water absorption of the flooded layer increases, which expands the range of the injected water on the plane of the oil layer and the thickness of the flooded layer in the longitudinal direction of the oil layer, thereby expanding the flooding volume, and unloading the unutilized crude oil during water flooding to improve the recovery of crude oil. The purpose of the rate.
    The concept and technical methods for polymer flooding to enhance oil recovery have been around for 15 years (1949-1964). In 1964, the United States began field trials of polymer flooding and industrial scale use tests. The National Petroleum and Energy Research Center (NIPER) believes that the ultimate recovery factor ET is determined by the oil displacement efficiency Ed, the sweep efficiency Es, and the economic factor Ee, ET = Ed × Es × Ee. The main contribution of the polymer is to increase the viscosity of the displacement working fluid, reduce the oil-water flow ratio and adjust the permeability profile, and improve the ultimate recovery by improving the sweep efficiency. Phillips Petroleum Company further explained the role of the polymer: 1 polymer makes the viscosity of the water phase increase, some polymers can reduce the relative permeability of the water phase after flowing through the porous medium; 2 reduce the water-oil ratio, water and oil flow The decrease of the ratio can reduce the fingering phenomenon; 3 the increase of the viscosity of the aqueous phase and the decrease of the relative permeability of the water phase can cause the fluid injected later to be transferred to the unspreaded band, thereby increasing the sweep coefficient.
        During the "7th Five-Year Plan" period, the two field trials of Daqing and Dagang Oilfields have achieved encouraging and good results. The development test of Daqing Oilfield shows that this process can greatly improve oil recovery and increase crude oil production. On average, per liter of polymer can increase the production of crude oil by more than 150 tons and increase oil recovery by 10%. Research work shows that this technology has a good application prospect in China. It is expected that in the future, polymer flooding and the use of chemical agents such as polymers will have greater development in China.
    Third, PAM is used as water blocking agent and profile control agent
    In the oilfield production process, due to the heterogeneity of the formation, flooding problems often occur and water shut-off is required. The essence is to change the penetration state of water in the formation to achieve the purpose of reducing oil production, maintaining formation energy and improving ultimate recovery. The PAM chemical water blocking agent has a selective effect on the oil and water permeability, and has less permeability to oil and a lower permeability to water. It can be used without cross-linking. It can also be cross-linked with aluminum salt, chromium salt, zirconium salt, etc. to form a gel. It can also add some resins to form an interpenetrating polymer network (IPN) to make it more temperature resistant. . If the W/O type PAM latex and the modified amino resin are chemically crosslinked, an interpenetrating polymer network water blocking agent can be formed, which has been applied in the oil field blocking water, and has achieved obvious effects. PAM can also be used to adjust the water absorption profile in the formation and block the large pores. Good results have been observed in practice.
    Fourth, PAM is used as a fracturing fluid additive
    The fracturing process is an important stimulation measure for the development of dense layers in oil fields. Its function is to open the passage of rocks and allow oil to flow through. The fracturing fluid obtained by crosslinking methylene polyacrylamide is widely used due to its high viscosity, low friction, good suspendedness, and ease of preparation and low cost.