Research And Application Of Diverted Acidizing Using Foamed Acid In Low-permeable Reservior In Hekou Oil Field

In the low-permeable reservior of Hekou oil field, flowback of reacted acid after conventional acidizing treatment is of difficulty. Reacted acid and secondary precipitate can not be eliminated on time, affecting the effectiveness of acidizing treatment. Repeated acidizings creat passageway in the formation. Acid flows away through the passageway. Water cut in some wells steep rises after acidizing treatment. Foam acidizing has selection, which can block high-permeable formation and water formation. Acid can be diverted into low-permeable formation and oil formation. It can control water cut after acidizing treatment. Gas expansion helps to flowback of reacted acid, reducing the harm to formation.Foam fluid property and flow rule were researched. Formula for foam acid was gained through evaluation experiments of foaming agent and stabilite. The formula has good foamability, stability, resistance of mineralization and temperature. Experiments of core displacement show that foam has selection of oil and water containing cores, and high and low permeable cores. Foam has good diversion effect, which is fit to uneven layer.Experiments of foam flow property in porous media show that foam stability in water wetting media is good, and foam generation is easy. Foam stability in oil wetting media is bad, and foam generation is hard. Experiments of foam flow in long and thin pipe show that foam blocking ability is in direct proportion to gas fluid ratio. Foam blocking ability increases with gas fluid ratio in some range. Foam can not cause end face blocking. Pressure difference at inflow point is lower than that in interior of the model.According to energy conservation equation, mass conservation equation and momentum conservation equation, an array of ordinary differential equation for calculating the temperature and pressure distributions of foam fluid in the wellbore was established. Coupled solve of temperature and pressure distributions using numerical method was conducted. Distributions of foam temperature, foam quality, and pressure in wellbore were obtained. The results show that along with the increase of well depth, foam pressure and foam density increase. Start pressure and balance pressure of foam fluid lift are both lower than that of nitrogen gas lift. Along with the increase of acid flow, circle point, atart pressure, and balance pressure are all increasing. Field application technology of foam acidizing was researched, which can direct site application.