黄原胶及其衍生物的耐温耐剪切性能

Temperature Resistance and Shear Resistance of Xanthan Gum and Its Derivatives

耐温耐剪切性能是压裂液性能的重要参数,也是决定压裂施工成败的关键因素之一。为拓宽黄原胶非交联压裂液的应用范围,提高其压裂施工效果,针对黄原胶(XG)溶液的耐温耐剪切性能,研究了化学改性、构象等因素的影响。结果表明,化学改性可以显著增强黄原胶在低温下的耐温耐剪切性能,但对高温下的耐温耐剪切性能提升很小。化学改性可以促使黄原胶的网络结构和黏弹性能得到进一步增强,盐离子的加入可以促使改性黄原胶构象向双螺旋结构转变,将化学改性和盐离子同时作用于黄原胶,可以显著增强黄原胶的耐温耐剪切性能及其在高温下的支撑剂悬浮性能。此外,耐温耐剪切测试(180℃)前、后的流变性能对比表明,盐离子的加入可以增强黄原胶溶液在高温下的黏弹性能、触变性和表观黏度,使其在超高温下仍具有良好的携砂性能,拓宽了黄原胶和改性黄原胶作为非交联压裂液的适用范围。因此,通过化学改性和盐离子共同作用,可显著提高黄原胶压裂液的流变性能和耐温耐剪切性能,使得黄原胶非交联压裂液,特别是海水基改性黄原胶压裂液,具有优良的压裂性能和广阔的应用前景。

Temperature resistance and shear resistance are important parameters of fracturing fluid and the one the key factors to the success of fracturing job.To widen the application o f non-crosslinking xanthan gum fracturing fluids and improve their job performance,study has been conducted on the effects o f chemical modification and molecular conformation of xanthan gum(XG)on the high temperature resistance and shear resistance o f XG solution.It was found that at low temperatures,chemical modification can remarkably enhance the temperature resistance and shear resistance o f XG.At high temperatures,chemical modification plays almost no role in enhancing the temperatoe resistance and shear resistence of XG.Chemical modification improves the networking structure of XG molecules and the viscoelasticity of XG solution.Addition of salts(ions)into XG solution accelerates the formation of double helix conformation o f XG molecules.The combined action o f chemical modification and salts on XG remarkably improves the temperature resistance,shear resistance and suspending capacity at elevated temperatures.Comparison of rheology before and after shearing at 180℃indicated that salts can enhance the viscoelasticity,thixotropy and apparent viscosity o f XG solution at elevated temperatures,improving its sand carrying capacity,and widening the application o f non-crosslinking fracturing fluids formulated with XG and modified XG.It is concluded that combined action of chemical modification and salts greatly improves the rheology,temperature resistance and shear resistance of XG solution,thereby widening the application of non-crosslinking fracturing fluids formulated with XG,especially the XG fracturing fluids mixed with seawater.