基于缝内流体温度场模拟的低伤害压裂液体系研究

Study on low damage fracturing fluid system based on simulation of fluid temperature field in fractures

压裂施工时在压裂液流经井筒进入地层的过程中,受储层岩石环境影响,其温度逐渐升高,液体的流变性能也随之发生变化,进而影响人工裂缝形态及支撑剂的铺置。研究压裂液在上述过程中温度变化规律有助于优化液体配方,改善支撑剂的铺置效果。因此,本文借鉴经典的K-DR模型,并考虑裂缝形态在压裂过程中的动态变化,建立了施工过程中液体温度计算模型。以上述数学模型为基础编制了温度场计算软件,利用该软件开展了大量的数模计算,结合压裂液体系室内评价成果,建立了不同温度条件下压裂液浓度设计图版,并耦合温度分布与压裂液性能及压裂注入量关系,形成压裂施工过程中裂缝不同位置的液体性能变化剖面,指导压裂液配方设计。该图版获得广泛应用,通过优化压裂液稠化剂浓度,降低了压裂液成本及液体残渣含量,近两年应用82井次,节约稠化剂共计496 t,获得显著的经济效益。

During the whole process of fracturing fluid flowing through the wellbore into the formation,the temperature of the fracturing fluid will gradually increase due to the influence of the reservoir rock environ-ment,and the rheological properties of the fluid will also change,thus affecting the artificial fracture morphol-ogy and proppant placement.Studying the temperature change rule of fracturing fluid in the above process will help to optimize the liquid formula and improve the proppant placement effect.Therefore,by referring to the classic K-D-R model and considering the dynamic change of fracture morphology in the fracturing process,a calculation model of liquid temperature in the construction process was established.Based on the above mathe-matical model,a temperature field calculation software had been developed,and a large number of numerical simulation calculations had been carried out using the software.Combining with the results of the indoor evalu-ation of the fracturing fluid system,a design chart of the fracturing fluid concentration under different tempera-ture conditions had been established,and the relationship among the temperature distribution,the fracturing fluid performance and the fracturing injection volume had been coupled to form the fluid performance change profile at different positions of the fracture during the fracturing construction process,which could be used to guide the design of the fracturing fluid formula.This chart has been used widely.By optimizing the concentra-tion of thickener in fracturing fluid,the cost of fracturing fluid and the content of liquid residue have been re-duced.It has been applied 82 times in the past two years,saving a total of 496 t of thickener,and achieving significant economic benefits.