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

摘要： 在碳酸盐岩油藏酸化中,近井筒附近的温度场对酸化效果影响很大。通过一种双重尺度模型对这一问题进行了研究,模型考虑了孔隙中的对流传质、传热和液固表面的酸岩反应。结果表明:与实验室常温条件相比,地层高温条件下的酸岩反应速率增快,形成主蚓孔的注酸速度增大(Damköhler数减小),且当注酸速度较大时,突破体积明显下降;当模拟区与外界不发生热交换时(绝热边界),由反应放出的热量使得模拟区的温度上升,造成突破体积比等温边界时的小;若酸液在井筒中不与地层发生热交换,则注酸速度较低时不同地层温度的突破体积几乎没有差别;反之,注酸速度较低时突破体积随着地层温度的上升而增加。

关键词: 碳酸盐岩, 蚓孔, 温度场, 突破体积