Engineering Design Of Top Gas Injection Stable Gravity Drainage Of Ultra-thick Reservoir

The reserves of ultra-thick structural reservoirs in China are large in scale and they are generally characterized by strong heterogeneity and difficult to exploit.The effect of waterflooding is generally worse than that of conventional reservoirs.Horizontal gas injection is easy to break through the gas prematurely and the development effect is poor.It is necessary to further change the displacement mode.Further enhanced oil recovery by gas injection gravity stable flooding and other technologies.For gas injection gravity stabilization technology,there have been many successful cases abroad,but the application of this technology in China’s oil fields is still in the initial stage of exploration.In this paper,the principle of gas injection to enhance oil recovery is analyzed,and the mechanism of top gas injection gravity flooding is studied.The principle of top gas injection gravity drive mainly depends on the gravity differentiation of oil and gas.Gravity is the main driving force of top gas injection gravity drive,which is also the feature of distinguishing traditional gas injection drive.Carrying out long core displacement experiment and interface migration experiment and study the influence of different injection gas,injection speed and angle on oil displacement efficiency.The change of fluid flow after gas injection is studied by microcosmic method.The homogeneous model and heterogeneous model are designed to observe the change of oil-gas interface.Experiments show that proper gas injection speed is the key to the formation of stable downward movement of gas oil interface in gas injection gravity drainage.The lower the gas injection speed,the easier it is to form stable gravity drive,and then better displacement effect can be obtained.For gas injection,the larger the angle of inclination is,the more obvious the gravity effect is,the more stable the gravity drive can be formed and the recovery factor can be enhanced.Based on the field data of the block,eclipse is used to establish the mechanism model of ultra-thick oil reservoir,carrying out the adaptability analysis of reservoir conditions and sensitivity analysis of injection production parameters,evaluate the influence of porosity permeability relationship,oil saturation,rhythmic layer,injection production well spacing,timing of gas injection,gas injection speed,oil production speed and other factors on the final oil recovery and clarify the influencing factors and technical adaptability of gas injection gravity stable flooding.The influencing factors and technical adaptability of gas injection gravity stable flooding are clarified to provide guidance for similar reservoirs to carry out gas injection gravity stable flooding.