Exploration and Development Research Institute, Shengli Oilfield Company, SINOPEC, Dongying City 257015, Shandong
Abstract: The resources of extra-low permeability reservoirs suitable for CO2 flooding are abundant in Shengli Oilfield, but the application of CO2 flooding faces technical bottlenecks such as being difficult to be miscible and low sweep efficiency due to the formation characteristics of deep burial depth, low abundance, strong heterogeneity, and high miscible pressure. The geology, fluid mechanics, reservoir engineering theory, and methods are applied comprehensively. By combination of the physical experiments and numerical simulation, the evaluation system of adaptability, technologies of laboratory experiment and schedule optimization technology series of reservoir engineering of CO2flooding for enhancing oil recovery are formed, and the injection–production technologies of CO2flooding are further established. The field test shows that CO2 has a good capability of injection and the oil increment is obvious. The cumulative oil increment is 6.9 × 104 t at a cumulative CO2 injection of 30.7 × 104 t in the pilot test area in Gao89-1 Block. The oil recovery is 18.6% in the central well block with enhanced oil recovery of 9.7%. The advanced injection of CO2 is 1.9 × 104 t, and the formation pressure recoveries from 17 MPa to 33.7 MPa in the Fan142-7-X4 well group. The miscible flooding is formed and the corresponding oil well produces fluid by natural flow exploitation. The daily oil production of the single well is kept stable at 5–6 t/d, which is much higher than 1 t/d before CO2 injection.