Research On Impact Factors And Evaluations Of Gas-wetting Core

In gas condensate reservoir, the liquid phase will condensate near the wellbore when thewellbore pressure below the dew point pressure, lowers the permeability of bottom wellbore,resulting in the deliverability of gas-well serious decline. In order to solve the liquidcondensation in gas condensate reservoir, some academics have suggested that reversing thewettability of the near wellbore from liquid-wetness to gas-wetting by fluorocarbon surfactant,the C-F bond of fluorocarbon surfactant has an excellent character of hydrophobic andoleophobic, it can form a monolayer adsorption on the rock surface which will convert thewettability of the rock into gas-wetting. This paper mainly includes three parts: the first, thisarticle proposes some method of quantitatively evaluate gas-wetting, based on the study ofconventional methods, including contact-angle, Amott method, USBM and Washburn method.Using several different types of fluorocarbon surfactant prepares gas-wetting cores, optimumselecting fluorocarbon surfactant with good gas-wetting reversal agent-FG24and FG90,which can convert the wettability of core into liquid wet or neutral gas-wetting. the core canbe strong gas-wetting when the concentration of FG24is0.3%, the contact angle of waterphase and oil phase is respectively141.3°and95.5°; the core can be strong gas-wetting whenthe concentration of FG90is0.5%, the contact angle of water phase and oil phase isrespectively96.8°and82°; Second, according to the measurement result of surface energy,the stronger gas-wetting of the core is, the smaller the surface energy is. The surface energyof the cores is least, only1.19mN/m, treated by0.6%FG24; The surface energy of the coresreduces from109.3mN/m to16.2006mN/m, the least surface energy is treated by0.5%FG90.The study found that treated by fluorocarbon surfactant, gas-wetting of core gas issignificantly enhanced; the surface energy of the core can be greatly reduced. Meanwhile,though the adsorption experiments of FG, measuring the adsorption of FG24FG90on quartzsand. In a certain concentration range, the adsorption increases with the increasingconcentration of surfactant; Third, carried though the high-temperature and high-pressuregas-driving, result shows that the gas displacement efficiency and permeability of coreincrease as the temperature rises. When temperature is120℃, gas displacement efficiencyis75%(treated by FG24) is three times more than gas displacement efficiency before treatment.; When temperature is100℃, gas displacement efficiency of treated by FG24isthree times than the pre-processed, permeability increases significantly; When temperature is80℃, gas displacement efficiency of treated by FG24is2times than the pre-processed. At ahigh temperature, gas-wetting reversal agent easily forms a gas-wetting adsorption film on thesurface core, and then forms gas-wetting dominant channels in the medium, and the flowconditions of gas and liquid can be significantly improved. Based on the emulsificationmechanism and Jamin superposition mechanism, the fluid can move faster in the gas-wettingadvantages channels, ultimately enhance oil and gas recovery.