Using Separated Molecular Weight and Pressure for Zonal Layer Injection Technique to Improve Pay-gross Thickness Ratio in ASP Flooding(PPT)

摘要

ASP flooding is a novel tertiary oil recovery technique, which has been developed ,for further EOR in Daqing oilfield. Field tests showed that the recovery rate can be improved by 20 percent higher than water flooding. For a typical heterogenic oilfield, taking Daqing oilfield as representation, due to permeability considerable differences varied in different layers, commingled ASP fluid injection with single molecular weight polymer might block the layers. As a result, it is difficult to improve the down hole injection profile effectively. Numerical study showed that better developed results could be achieved by using molecular weight polymer in ASP fluid matching injection for heterogenic multilayered oilfield on longitudinal. The recovery rate could be improved by 2 percent based on commingled injection. In this paper, a separated molecular weight and pressure injection technology for ASP flooding has been developed based on microscopic mechanism and analog simulation studies. A special ASP fluid injecting string for separating molecular weight and pressure was designed on the condition of keeping the same surface investment. The injection string can apply different molecular weight polymer fluids in ASP injection for different layers as required, matching with the permeability differences of reservoir on longitudinal distribution. The injection volume and formula weight of ASP fluids for zonal layers can also be controlled. The molecular weight is regulated from 20 percent to 50 percent and the choke pressure difference can be up to more than 2.5MPa. The maximum viscosity loss ratio is less than 8 percent. Field test in near a hundred wells showed that the injection profile was improved effectively and the pay-gross thickness ratio was increased by 8 percent after using this technique. It will play an important role on the development of mature oilfield in future.