抗高温高密度水基钻井液流变性研究

STUDY ON RHEOLOGICAL PROPERTIES OF HIGH-TEMPERATURE HIGH-DENSITY WATER BASED DRILLING FLUID

使用Fann50SL型高温高压流变仪对抗高温、高密度水基钻井液的流变性能进行了测定。实验分析表明,该种抗高温高密度水基钻井液在高压下表观黏度、塑性黏度和剪切应力随温度升高而降低,其降低趋势逐渐递减。运用回归分析方法对实验数据进行处理,确定出钻井液在高温高压下遵循的流变模式——卡森模式,建立了预测井下高温高压条件下钻井液表观黏度的数学模型。计算表明,所建立的预测钻井液表观黏度的数学模型能够较准确地描述高密度钻井液在高压下与温度之间的关系,钻井液的表观黏度与温度呈指数函数关系。运用幂律、H-B和卡森等流变模式对钻井液高温高压下的流变数据进行拟合分析时,建议最好选用卡森模式。

A HTHP rheometer, Fann50SL, has been used to measure the HTHP rheological properties of a kind of high-temperature high-density water based drilling fluid. The experimental analysis indicates that the apparent viscosity (AV), plastic viscosity (PV), and gel strength (Gel) of that drilling fluid will decrease with temperature, and the decrease amount will become smaller with the temperature increased. And the regressed results suggest that the best model suitable for HTHP rheological properties of this drilling fluid is Casson Model. Based on these investigations, a mathematical model used to predict the apparent viscosity of drilling fluid at HTHP conditions is established. The calculation results have proven the accuracy of this model. It is recommended to better use Casson model to conduct matching analysis of rheological properties of HPHT drilling fluid.