Layered Injection Technology Research Articles

Layered injection technology for chemical flooding of Class-III oil reservoirs in the Daqing Oil Fields complex, Songliao Basin, Northeast China

The Class-III oil reservoirs of Lasaxing oilfield in the Daqing Oil Fields complex have geological oil reserves of 1.86 billion tonnes, an oil recovery of 39%, with remaining reserves accounting for more than 45% of the total geological reserves of the oilfield. Therefore, they have considerable potential for future oil production. The current layered injection technologies fail to achieve effective control over the low single-layer injection rates since they can only produce low throttle differential pressure under low injection rates (5–20 m3/d). In this study, a symmetrically-structured double-offset-hole injection allocator and a novel throttling component were developed. Their spatial layout was constructed and mechanical parameters were optimized using finite element analysis, which allows for expanding the flow rate range at low injection rates. According to experimental results, the throttle differential pressure increased from 0.2 MPa to 0.8 MPa at an injection rate of 5 m3/d, and the range of the single-layer flow rates expanded from 20 – 70 m3/d to 5–70 m3/d. The field test results show that the effective production of oil layers with medium and low permeability was achieved and that the ratio of producing oil layer thickness to the total reservoir thickness increased by 9.7% on average. Therefore, this study provides valuable technical support for the effective chemical-flooding-based development of Class-III oil reservoirs.

Experimental evaluation of ASP flooding to improve oil recovery in heterogeneous reservoirs by layered injection approach

AbstractTo improve the oil displacement effect of ASP (alkali/surfactant/polymer) solution in heterogeneous oil reservoirs, layered injection technology is proposed for the first time for Daqing Oilfield. The technology uses partial pressure tools to control the injection amount of ASP solution in high‐permeability oil layers and uses a partial quality tool in low‐permeability oil layers. To study the experimental effect of this layered injection technology, the relationships between the different permeability, molecular weight, and concentration of the ASP solution, as well as the resistance coefficient and residual resistance coefficient, are first established, and then, a layered injection experimental model is established to carry out experimental research on injection capacity and oil displacement capacity. The experimental results show that the smaller the range of the core permeability is, the larger the molecular weight and concentration of the ASP solution are, and the poorer the injection capacity of the ASP solution is. After the action of a partial pressure tool and a partial quality tool, the injection capacity of ASP solution is improved to different degrees, and the oil displacement effect of low‐permeability cores is significantly improved, while the total oil recovery is increased, and the total oil recovery of heterogeneous cores under different conditions is increased by 1.4%‐4.05%. This experiment is of great significance to the study of improving the oil recovery of heterogeneous reservoirs.