高凝油油藏自生热压裂井筒温度场计算模型

在高凝油油藏的压裂施工中,对地层注入冷流体会使井底周围的原油冷却,导致原油析蜡或凝固,从而堵塞流动通道,降低裂缝的导流能力.因而采用自生热压裂技术,依靠生热剂发生化学反应所放出的热量来提高注入流体的温度,使井底压裂液的温度在施工期间高于原油的凝固点或析蜡点.在压裂过程中预测井筒温度的变化,以保证压裂液在进入裂缝后不会对裂缝和储层造成“冷伤害”是实施这一技术的关键.根据热平衡方程,建立了自生热压裂过程中井筒温度场的数学模型,采用隐式差分格式建立了数值计算方程,并对一口井进行了实例计算和分析.结果表明,采用自生热压裂技术能有效地提高压裂液的温度,防止高凝原油析蜡和凝固,避免储层伤害,提高原油的流动能力.

Calculation model for well bore temperature profiles in high freezing point oil reservoirs with in-situ heat fracturing treatment

To enhance the effect of fracturing treatment for the high freezing point oil reservoirs,it is necessary to prevent the injection of cold fluid from cooling crude oil around the wellbore,because the cold fluid may cause the wax separated or solidified in the crude oil and plugging some flowing channels.The in_situ heat fracturing technique was applied to stimulation of the temperature of injected fluid in high freezing point oil well.The heat out of chemical reactions resulted from heat_generation agent can heat up the oil layer.Consequently,the damage of organism blocking can be removed,and the cold damage of injected fluid to reservoir can also be prevented,and the productivity of oil well can be improved greatly.However,the key for realizing this technology is to forecast the bottom hole temperature profiles during fracturing treatment.In view of this point,a mathematical model for wellbore temperature profiles based on heat_balance equation was established,and the numerical computation equations using implicit difference format were set up.Aiming at an example of Liaohe Oil Field,the effects of injecting temperature,injection rate of surface fluid and concentration of heat_generation agents on the change of the bottom temperature in wellbore were analyzed.This technique can improve the fracturing treatment effect.