Top Of The Gas Injection Gravity Stable Flooding To Enhance Oil Recovery Mechanism

Aimed at the mechanism studies of crestal gas injection for gravity stable flooding to enhance oil recovery in this paper, based on the investigation of comprehensive literatures about its application examples at home and abroad, characters of reservoir geology suitable for crestal gas injection are summarized, characters of suitable reservoir exploitation and characters of organic solid phase deposition are analyzed during gas injection, then the mechanisms of miscibility and gravity flooding of crestal gas injection are analyzed.Taking associated gas injection of A12B well in WZ12-1 for example, PVT test of formation fluid, swelling test and multi-contacts test of injection gas-crude oil by DBR-PVT instrument, which was introduced from abroad, are conducted. phase behaviors and miscibility mechanisms of injection gas-crude oil are test and are simulated by p-T, p-X phase diagram calculation models, which were displayed in lines of constant volume fraction, multi-contacts phase equilibrium calculation models, and a three-parameter cubic equation of state for asymmetric mixture density calculations. Taking associated gas injection and CO₂ injection in a certain oil field for examples, slim tube test is conducted to determine minimum miscibility pressure and research the compatibility between injection gas and crude oil. Long core flooding test of crestal gas injection by Hycal long core flooding instrument is conducted to research flooding effect of various injection gases and difference of flooding effect with horizontal core and slant core. Then slim tube test and long core flooding test of A12B well in WZ12-1 oil field are numerically simulated, to study the mechanism of miscibility and evaluate flooding effect through different long care flooding modes of crestal gas injection.Last, based on feasibility assessment result of crestal gas injection, geology and reservoir feasibility estimation for crestal gas injection of middle block WIV segment reservoir in WZ12-1 oil field are done. With reservoir numerical simulation technique, gas injection is simulated with reservoir profile; the effects of oil recovery rate, gravity variance, reservoir heterogeneity, capillary pressure and injected gas viscosity on recovery ratio are studied. Reservoir is simulated with three-dimensional numerical model. Different exploitation schemes of depletion exploitation, water flooding and gas flooding are compared. Then, oil rate, well open time and gas injection well net are analyzed sensitively and optimized. At last venture and potentiality of crestal gas injection are evaluated.