A Mathematical Model Study On Foam Acidizing Diversion In Horizontal Well

Foam possesses temporary block characteristic, Foam diversion can effectively solve theproblem that acid distribution among layers of different permeability, which is important toequably unblock in horizontal well. The key in successful use of foamed acid acidizingtechnology is full understanding the diversion mechanism of foamed acid in horizontal well.Because of this, the foam and acidizing mechanism of foamed acid are discussed througha series of experiments. Then the characteristic of horizontal well acidizing and the propertiesof foam fluid are studied. On this basis, according to variable mass pipe flow in horizontalwell and foam diversion in the formation, furthermore, rheological properties are considered,a mathematical model is presented.Then the discrete model is given and solved by numerical methods. Then a well in thefield is taken as an example. Make a theoretical dynamic analysis of the pressure in thewellbore, the skin factors and the distribution of the foamed acid. The ratio of radius increaseand standard deviation analysis are presented.Through them, distribution law of foamed aciddiversion in horizontal well is discussed.The results show that:1) Equably unblock in horizontal well can be solved effectively byusing foamed acid.2) The radius of foamed acid increases with time, but the radius near theheel has a lager increasing range than the radius near the toe.3) The total skin factor in thenear-well region increases with time, however, the initial skin factor decreases with time.4)The pressure in the wellbore increases with time, but the pressure along the wellboredecreases at the same time.5) The diversion effect is affected by injection rate，foam quality，temperature，radius of wellbore and permeability ratio.6) The diversion effect will becomebetter with the increase of the injection rate or foam quality and worse with the increase ofradius of wellbore or temperature.7) The diversion effect will also become worse if thepermeability ratio is too large，especially the low permeability zone.