Abstract
The development effect of low permeability reservoirs of offshore Shahejie Formation in China is poor with fast formation pressure drop, rapid production decline and numerous abnormal wells due to the influence of low permeability, strong heterogeneity, ultra-high reservoir temperature and pressure and high wax and asphaltene content. To overcome these difficulties, this paper takes geological conditions, reservoir potential, stimulation technology and actual wells situation into consideration on the basis of the reservoir performance research, and gives full play to the integration of reservoir and mechanical recovery. A set of production enhancement and efficiency improvement technologies has been formed, including moderate periodic water injection based on pressure fluctuation theory, liquid extraction optimization for low permeability fields, modified compound plugging removal technology, small flowrate and broad width electric pump selection technology, and pump stuck early warning technique to achieve the efficient development of offshore low-permeability oilfields. Moderate periodic water injection not only makes full use of the imbibition effect to achieve the equilibrium displacement, but also avoids the water channeling in fracture area; eight main controlling factors are used to classify and evaluate the liquid extraction potential and select the well group at level-1 for the workover with the effect of daily oil increase of 42 m3; modified compound plugging removal technique completely removes the pollution and plugging of the formation and the wellbore to release the potential of the oil wells to the greatest extent and cumulative oil increase of 6 well times is expected to be 12.44×104 m3; small flowrate and broad width electric pump selection technology applied for more than 30 well times improves the adaptability of the pumps substantially and extends the pump inspection cycle to 857 days; real-time pump stuck warning technique through the dual pattern of analyzing both conventional and high-frequency data guarantees the efficient operation of oil wells. The technologies in this paper have been applied in the target low-permeability field with daily oil production of 429 m3, oil recovery rate of 1.1%, natural decline rate drop year by year and the expected recovery factor of 20.9% under current well pattern. The key technologies in this paper have improved the target reservoir development effect significantly and provided important reference significance for other offshore low-permeability reservoirs development.
Semi-analytical modeling of advanced water injection in low permeability reservoirs under non-Darcy-flow condition