黄原胶和羧甲基纤维素对水合物浆液流变特性的影响规律研究

Study on the influence of xanthan gum and carboxymethyl cellulose on the rheological properties of hydrate slurries

当深水钻井气侵发生后,水合物在井筒中生成,从而改变钻井液流变性,造成井筒压力精确控制困难。实验研究了水基钻井液添加剂主剂黄原胶和羧甲基纤维素对水合物浆液流变特性的影响规律,分析了水合物浓度、黄原胶浓度和羧甲基纤维素浓度对浆液表观黏度、剪切强度和塑性剪切强度等流变参数的影响,发现不同水合物浓度条件下含黄原胶的水合物浆液均为假塑性流体,呈现剪切稀释性,而含羧甲基纤维素的水合物浆液在水合物浓度低于4%时呈现剪切增稠性,在水合物浓度高于4%呈现剪切稀释性。同时,发现水合物浓度的增加,会凸显水合物浆液的剪切稀释性,降低其流变指数,增加稠度系数。根据非牛顿流体幂律模型,构建了含黄原胶和羧甲基纤维素浓度的水合物浆液流变模型,可为预测深水钻井井筒内水合物生成风险和构建水合物高效防治方案提供理论基础。

When gas influx occurs in deep water drilling,hydrate is prone to form in the borehole,which changes the rheology of drilling fluid and makes it difficult to precisely manage wellbore pressure.The influencing laws of water-based drilling fluid additives,dominated by xanthan gum and carboxymethyl cellulose,on the rheological properties of hydrate slurry were experimentally studied.After analyzing the influences of hydrate concentration,xanthan gum concentration and carboxymethyl cellulose concentration on the rheological parameters such as apparent viscosity,shear strength and plastic shear strength,it is found that hydrate slurries containing xanthan gum are all pseudoplastic fluids under different hydrate concentrations,exhibiting shear thinning properties,while those containing carboxymethyl cellulose exhibit shear thickening when the hydrate concentration is lower than 4%,and exhibit shear thinning when the hydrate concentration is higher than 4%.At the same time,it is found that as the hydrate concentration increases,the shear dilution of hydrate slurry is highlighted,thus reducing its rheological index and increasing the consistency coefficient.According to the power-law model of non-Newtonian fluid,a hydrate slurry rheological model including xanthan gum and carboxymethyl cellulose concentrations is constructed,which can provide a theoretical basis for predicting hydration risk in deepwater drilling and preparing an efficient borehole hydrate prevention scheme.