基于黏度计读值预测的高温高压流变性预测方法

钻井液高温高压流变参数预测分析是深井超深井钻井液性能调整、水力参数计算的基础，建立了一种基于黏度计读值预测的钻井液高温高压流变性分析方法。首先，开展了高温高压流变实验，基于实测数据分析了旋转黏度计读值随温度、压力的变化规律。然后，引入比例因子将各转速测量读值归一化，运用数值方法分别分析了恒压变温、恒温变压情况下比例因子与温度、压力的变化关系，先建立了高温高压下比例因子预测模型，随后建立了通用的高温高压黏度计读值预测模型，同时给出了高温高压流变模型优选与流变参数计算方法。通过多组实验数据计算对比，运用该方法计算所得黏度计读值与实测值吻合很好。进而运用该方法分析了一组实测钻井液在井筒内的流变参数变化情况，与传统方法相比，该方法不再局限于常规流变参数（塑性黏度、表观黏度等）预测，其可以扩展到所有流变模型的高温高压流变参数预测中。 

A Method of Predicting High Temperature High Pressure Rheological Property Based on Viscometer Readings

Prediction and analysis of high temperature high pressure (HTHP) mud rheological property together form the basis on which drilling fluid property control and hydraulic parameter calculation for deep and ultra-deep wells are performed. This paper introduces a method of analyzing HTHP drilling fluid rheological property using viscometer readings. In developing the new method, the pattern of the rotational viscometer readings changing with temperature and pressure is analyzed using data from laboratory HTHP experiments. The readings at different rotational speeds are then normalized using factors of proportionality. Using numerical method, the relationship among the factor of proportionality, temperature and pressure at constant pressure changing temperature and constant temperature changing pressure is analyzed. A model for predicting HTHP factor of proportionality and a general model for predicting HTHP viscometer readings are established based on the analyses. Methods of selecting HTHP rheological model and calculating rheological parameters are also developed. The calculated rheological parameters and the measured ones fit very well, as shown by comparing two sets of parameters. Using the method, a set of rheological data of a drilling fluid taken from a wellbore is analyzed. Compared with conventional methods, this new method can be use to predict not only normal rheological properties (plastic viscosity, apparent viscosity etc.), but also HTHP parameters of all rheological models.