The Polymer Molecular Configuration Of Oil Displacement Agents And Their Flow Characteristics

Owing to the fast acting increasing in the crude oil demand in China and the deep rising in international crude oil price, it has become necessary for petroleum industry to develop the production potentiality of older oilfields and enhance the oil recovery in China. So, in recent years, various chemical flooding techniques are being stdied by many petroleum scientists in an expectation of a more substantial increase in recovery. For more in-depeth study on the influencing factors of chemical flooding and their mechanism and on the basis of available studies, the molecular aggregaton structure, molecular coil dimension, rheological property and seepage property of chemical flooding systems and their mechanism were studied, by making use of scanning electron microscopy (SEM), dynamic light scattering (DLS), rheological property experiment and core flow experiment.The results show that the polymer molecular in solution is in the form of multi-layer stereoscopic random reticulation, with self-similarity of fractal growth. Several chemical flooding systems are the performance of the rheological property of"shear thickening at first and shear thinning then". The molecular aggregaton structure and molecular coil dimension (Dh) of polymer are affected by polymer molecular weight, concentration, solvent water salinity, shear and temperature, etc, which result in the changing of macro rheological property and viscoelasticity of polymer solution, as well as of its resistance factor, residual resistance factor and the ability of transmission and migration when passing core. The nonionic surfactant can adsorb on the polymer molecular chains in the form of micellar aggregate, forming"nonionic surfactant -polymer"complex. The molecules aggregate a"flaky- reticulation"structure, result in a greater Dh, a greter rangeability of solutioin viscosity with the shearing rate, a better viscoelasticity, a greater resistance factor and residual resistance factor and a worse ability of transmission and migration.The mocules in"Alkali/surfactant/polymer"system aggregate a relatively loose bead-like network, which resulting in a decreasing of Dh, a weakening of shearing rate dependence of viscosity and viscoelasticity and a decreasing resistance factor and residual resistance factor. However, by adding alkali, the"Alkali/surfactant/polymer"system is easy to produce precipitation in the model so that under the condition of low viscosity, its ability of transmission and migration is worse than polymer solution with the same concetration.The molecular configuration of"Polymer gel 1"with characteristics of an intra-molecular cross-linking is still in the form of the reticulation, but not strong. Its gel shows spherical molecules which irregularly distribute in the network backbone. The molecular configuration of"Polymer gel 2"with characteristics of an inter-molecular cross-linking mainly presents long-range dense flake structure with strong rigidity and the best capacity of increasing viscosity. The abilities of transmission and migration of"Polymer gel 1"and"Polymer gel 2"are wose than polymer solution, the resistance factor and residual resistance factor are greater. Opposite to polymer, the residual resistance factors of"polymer gel 1"and"polymer gel 2"are greater than resistance coefficients.The Active polymer, whose molecular trunk is thicker and its branch is lower than those of polymer, shows a"flake-network"configuration, and has seldom twist between the branches of different molecules. At the same concentration, the molecular coil dimension (Dh) of active polymer is largest, its resistance factor and residual resistance factor are greatest and the ability of transmission and migration is very poor.