In-depth combined blockage removing technology with liquid alternating gas injection for polymer flooding response wells in Bohai Oilfield

The blockage in polymer flooding response wells in Bohai Oilfield is complicated, so the conventional blockage removing technologies don't work well.In this paper, the compositions of blockage were analyzed.It is shown that the blockage is existed in the complex form with organic matters, inorganic matters and polymer coating with each other.Therefore, it was proposed to adopt the concept of blockage stripping and removing step by step, i.e., cleaning the organic matters using organic solvent firstly and then dispersing the micelle bearing blockage.Contrast experiments were carried out on the blockage removing results of various blockage removers from three aspects, i.e., organic matter dissolution, micelle degradation and gel oxidizing and breaking.The blockage remover system selected according to the blockage removing mechanism is composed of 8%-10% methanoic acid + 4%-6% organic blockage remover D+1% strong oxidizer.The block radius of polymer flooding response wells in Bohai Oilfield is over 3 m.To improve the blockage removing effects and expand blockage removing radius, polycyclic blockage dissolution effects were compared and analyzed.And consequently, the blockage removing technology of polycyclic treatment and liquid alternating gas injection or accompanied injection was developed.This new technology was tested on site, and its application effect is remarkable with single-well daily oil increment of 60 m³/d.It provides the new idea for solving the productivity difficulty of polymer flooding response well.And it is worth popularizing in field.