Low Toxicity And Weak Gel Flooding Enhanced Oil Recovery Technology Research

Systematically studied in this paper are the low toxicity formulation of weak gel profile-modifying systems, the gelling reaction mechanisms and applied property evaluation and the injection parameters optimization of weak gel, and the matching technique such as regulation of enhancing recovery, disposal of wastewater containing weak gel and so on, by profile-modifying techniques of weak gel and the concept of environment protecting, making Huabei Chaheji Oil Field as research background. Achievements of this paper provided a stable foundation for research and practical application of low toxicity weak gel profile-modifying matching techniques.Through many lab screening experiments, we researched proper low toxicity formulation of weak gel system: the concentration of polymer HPAM 1500mg/L, cross linking agent 60 mg/L; coagulation retarder 450 mg/L, oxygen scavenger 100 mg/L; stability agent 200 mg/L. The gelling time of this system can be modulated and controlled. It can be used for liquid making-up of wastewater produced in Chaheji Oil Field whose salinity is 8432 mg/L. This paper also researched the gel reaction mechanism and cross-linking delaying mechanism.We researched the saline and thermal stability, screen factor, transformation pressure, pore resistance factor, injection property, transmission property, dynamic and static ageing stability, coefficient of resistance, coefficient of residual resistance, effective viscosity of weak gel system and its percolation feature through porous media. The result indicated that weak gel system had fairly good saline and thermal stability and anti-shear property. It is reasonable using screen factor to evaluate the gelling time and using transformation pressure to evaluate the intensity. The pore resistance factor of weak gel came up to more than 80. It indicated that the weak gel had fairly high viscoelasticity after gelling and it can satisfy the needs of profile-modifying in reservoirs. Weak gel had good property of injection and transmission. The retention ratio of viscosity was usually 79-82% after weak gel got through the core, so the weak gel had fairly good dynamic stability. Compared with the polymer solution which had equal concentration, the resistance coefficient of weak gel was higher than 10-30 times, the residual resistance coefficient was higher than 8-30 times, however, their effective viscosity were basically equal. It indicated that weak gel was a technique whose mechanism is physically plugging big high-permeation cross-flow channel(deep profile-modifying). On the other hand, because of the existence of effective viscosity, the weak gel had the function of displacement(movable). The bigger the size of pore throat of reservoir which was implemented profile-modifying with weak gel, the bigger the recovery;...