What is polymer flooded oil

Polymer flooding is actually to add water-soluble polymers to the injection well to increase the viscosity of the injected water, so that the flow capacity of the oil is relatively improved, thereby improving the oil field recovery rate
.
Polymer flooding is a tertiary oil recovery method
.
After years of pilot testing in the mine in China, polymer flooding has achieved a good effect of improving the recovery rate by 8% to 10%, and has formed a certain scale of industrial production capacity in Shengli, Daqing, Dagang and other oilfields, which has become a new measure for
increasing reserves and production in oilfields.

1.
The reservoir of polymer flooding should have the following conditions

At present, some of the hydrolyzed polyacrylamide polymers used have problems such as salt sensitivity, chemical degradation, and shear degradation, so there are certain requirements
for the geological conditions of the reservoir 。 It is generally believed that the reservoir suitable for polymer flooding should have the following conditions: (1) The oil layer temperature should not be too high, preferably not more than 70 °C; (2) The mineralization degree of formation water and injection water is low, which is conducive to polymer viscosity, and the general mineralization degree should be less than 10000mg/L; (3) The coefficient of variation of the permeability of the oil layer is too large or too small, which is not conducive to improving the effect of polymer flooding; (4) The permeability of the oil layer should be high and the porosity should be greater than 25%, if it is too small, it is not conducive to polymer flooding; (5) Other factors, such as the wettability of the oil layer and the pH value of the formation water, are also issues that must be considered and studied by
polymer flooding.

Most of China's oilfields belong to continental strata, in the plane, longitudinal heterogeneity is very serious, stratigraphic crude oil viscosity of more than 5mPa·s accounted for more than 90%, with a great potential for polymer flooding
.
According to the study, China's reserves suitable for polymer flooding reach 4.
3577 billion tons, of which Shengli Oilfield has 974 million tons, which can increase recoverable reserves of nearly 100 million tons, with great
potential.

2.
Factors affecting the efficiency of polymer flooding

There are many and complex factors affecting the oil flooding effect of polymers, including the heterogeneity of the oil layer, the mineralization of the formation water, the temperature of the oil layer, the characteristics of the well network, and the relative molecular weight and injection of the polymer
.
Therefore, when designing the agglomeration scheme, various factors should be considered comprehensively to achieve maximum economic benefits
.

3.
Dynamic change law of polymer oil flooding

Polymer oil flooding can be divided into the following three stages: water flooding blank stage, polymer injection stage and subsequent water flooding stage
.
Among them, the polymer injection stage is the central stage
of polymer oil flooding.
It is generally 3 to 3.
5 years, and the main task at this stage is to implement the polymer oil flooding program
.
The amount of polymer used in the scheme is injected into the oil layer according to different injection segments, and the later stage of this stage will also be the peak of oil increase, and more than 50% of the polymer flooding oil increase will be produced at this stage
.
After the polymer solution is fully filled, the injection well will continue to inject water into the third stage to maintain the polymer flooding effect until the water content of the oil production well reaches more than
98%.

4.
Polymer drive main process equipment

(1) Polymer dry powder dispersion device
.
It is the core device injected into the polymer device
.
Its performance directly affects the operation of the entire polymer injection device and the quality of the oil displacement effect
.
Its role is to dissolve a certain weight of polymer dry powder evenly in a certain weight of water, prepare a mixed solution of a determined concentration, and then transport it to the maturation tank
.
In order to prevent the degradation of the polymer solution, the whole set of devices is made of stainless steel
.

(2) Single screw pump
.
It is a kind of internal meshing closed positive displacement pump, with working balance, no pulsation or turbulence, and has the characteristics of
self-priming ability.
In order to prevent the viscosity loss of polymer solutions, single screw pumps are currently used in polymer injection processes as delivery pumps for mixtures and polymer busses
.

(3) Injection plug pump, the current polymer injection pump are selected plunger pump, the main reason is that the pump performance adapts to viscoelastic liquid, while the viscosity loss of polymer liquid is small
.
At present, there are more applications in the mine, including single plunger metering pump and three-plunger metering pump
.