关键词: 碳酸盐岩, 蚓孔, 温度场, 突破体积

Abstract: In carbonate acidizing,acid is injected down the wellbore to the treated formation to dissolve the rock so as to create worm holes.Due to the occurrence of acid-rock reaction,the temperature field of the near-wellbore region plays a very important role in influencing acidization results.However,the effect has not been investigated in literature.In this paper,this problem was studied based on a two-scale continuum model which concerned convection,diffusion and heat transfer in the pore and the reaction in the interface between acid and rock.The results showed that the required injection velocity for worm holes increased compared with the experimental ambient condition.Since the formation was deep and formation temperature was high,reaction rate was very high compared with that at ambient temperature according to the Arrhenius equation.In addition,breakthrough volume,which was the ratio of total injection volume to total pore volume,decreased greatly at high injection rate.Then,the acidization results of different boundary conditions(adiabatic condition and constant temperature condition)were compared.Under the adiabatic condition,since the released heat by the reaction could not be transferred to the outside,the temperature in the simulated regime was higher than that under the constant temperature condition,which led to low breakthrough volume.Finally,breakthrough volumes at different formation temperatures were very similar at a low injection velocity if acid did not exchange heat with the formation.However,breakthrough volumes would increase with formation temperature at a low injection velocity if acid did exchange heat with the formation.

Key words: carbonate, wormhole, temperature field, breakthrough volume