In-house Laboratory Investigation Of CO_ 2 -water Alternative Drive In Low Permeablilty Field

Fang 48 block is typical of low permeability reservoirs, which has the low starting pressure, high viscosity, the low displacement efficiency, and the poor water intake ability. In order to develop the reservoir effectively and reasonably, the paper carries on the feasibility of CO₂-water alternative drive through experimental method and simulate the layer actual situation on the basis of the sufficient survey about low permeability features and the low permeability condition at home and abroad when injecting gas.Gas-water alternative drive is a kind of effective method of improving oil recovery, and it can reduce the residual oil saturation of water flooding reservoir, improve displacement efficiency of oil, and improve the volume sweep efficiency of CO₂ at the same time. According to CO₂-water alternative drive experiment of low permeability reservoirs of Fang 48 block, this article gives out the following parameters which are measured at the different conditions of CO₂-water alternative drive, such as CO₂-water alternative drive recovery, breakthrough time of gas, the renew rate, the oil gas oil ratio of production, the ability of gas injection and so on. In this experiment, we confirmed the best injection parameters (alternate proportion, alternating slug, injection rate and injection intensity), and compared it with CO₂ drive. The experiment shows that the ratio of water and gas in the CO₂-water alternative drive is 1:1, and the size of slug is one-tenth of pore volume, and the effect of oil displacement is best at the time that the rate of injection rate is 1.14cm³/min, and the soonner the time of gas-water alternative drive, the effect of it is the better.The recovery efficiency of CO₂-water alternative drive is higher than CO₂ drive, so choose CO₂-water alternative drive firstly when conduct CO₂ drive.