A BCG − CO₂ fracturing fluid composed of a new thickener and CO₂ causes low amounts of formation damage, and it can be used to stimulate low‐permeability gas reservoirs with water sensitivity. However, at present the rheological properties of this foam fracturing fluid are unclear, which has limited its field application to some degree. The main purpose of this study was to ascertain the rheological parameters and a model of the BCG − CO₂ fracturing fluid. The rheological properties of the BCG − CO₂ fracturing fluid were evaluated by using a foam rheological test system. The unfoamed condition test results showed that when the shear rate was lower than 1000 s⁻¹, the effective viscosity exhibited a rapid decreasing trend. The effective viscosity of the BCG − CO₂ fracturing fluid was 4 to 26 mPa · s under foamed conditions. The comparison results showed that the viscosity of the BCG − CO₂ foam was suitable as a low damage fracturing fluid. The measured data were fitted using the H‐B and power law models in this study. The power law model, by contrast, was fit for describing the relationship between shear rate and shear stress. The foamed condition rheological index n^′ first decreased and then increased with increasing foam quality, and the rheological coefficient k^′ first increased and then decreased with increasing foam quality. For the different foam qualities, the rheological index n^′ first increased and then decreased with increasing temperature. The rheological coefficient k^′ showed a decreasing trend with increasing temperature. When an exponential function, in which the foam quality and temperature were independent, was used for fitting, it was not accurate in predicting the rheological properties. The fitting results based on a quadratic polynomial surface model were better. The average calculation errors of the rheological parameters were all less than 3.32%. The findings of this study can help develop a better understanding of the heat transfer and flow coupling process in wellbore and fracture in fracturing treatment.

中文翻译：

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低伤害BCG-CO2压裂液流变参数的变化及模型。

甲BCG - CO ₂一个新的增稠剂构成的压裂流体和CO ₂的原因低量的地层损害的，并且它可以用于刺激低渗透气藏与水的敏感性。然而，目前尚不清楚该泡沫压裂液的流变性质，这在一定程度上限制了其现场应用。这项研究的主要目的是确定BCG-CO ₂压裂液的流变参数和模型。使用泡沫流变测试系统评估BCG-CO ₂压裂液的流变特性。未发泡条件试验结果表明，当剪切速率低于1000 s ^-1时，有效粘度呈现出快速下降的趋势。在发泡条件下，BCG-CO ₂压裂液的有效粘度为4至26 mPa·s。比较结果表明，BCG-CO ₂泡沫的粘度适合作为低破坏性压裂液。在这项研究中，使用H-B和幂定律模型拟合了测量数据。相反，幂律模型适合于描述剪切速率和剪切应力之间的关系。发泡条件下流变指数n ^'随着泡沫质量的增加先降低后增加，流变系数k ^'首先随着泡沫质量的增加而增加，然后减少。对于不同的泡沫质量，流变指数n ^'首先随温度升高而升高，然后降低。流变系数k ^′随温度升高呈下降趋势。当使用泡沫质量和温度独立的指数函数进行拟合时，在预测流变特性方面是不准确的。基于二次多项式曲面模型的拟合结果更好。流变参数的平均计算误差均小于3.32％。这项研究的发现可以帮助人们更好地理解压裂处理中井眼和裂缝中的传热和流动耦合过程。