摘要
通常根据牛顿流体所得剪切速率计算非牛顿流体流变参数,计算结果存在误差,不利于准确描述钻井液流变性及提高水力计算精度,因此需要修正其剪切速率。根据四参数流变模式本构方程,运用幂级数展开理论推导,得出了流体在水平旋转运动中的流变规律及剪切速率表达式。编制了流变参数计算程序,根据剪切速率计算式迭代修正剪切速率,再利用修正的剪切速率回归计算流变参数。应用不同类型钻井液数据及一组水力实测数据对文中计算方法进行了流变分析及水力计算评价。结果表明:未修正的剪切速率误差较大,修正剪切速率后所得流变参数能够更好地描述钻井液流变性;运用剪切速率修正后所得流变参数进行水力计算,压降计算精度提高0.5 MPa,井底附加循环当量密度(ECD)与实测数据吻合更好,表明该方法具有一定的理论与应用价值。
It is common to calculate rheological parameters of a non-Newtonian fluid based on shear rates obtained by the Newtonian fluid formula,which gives a calculated result with considerable errors that goes against either an accurate description of rheological properties of drilling fluids or a high-precision hydraulic calculation.Therefore,it is necessary to amend shear rates derived from the Newtonian fluid formula when they are employed in a rheological parameter calculation of non-Newtonian fluids.Based on a constitutional equation of the four-parameter rheological model,we obtained an expression for rheological laws and shear rates of fluids in a horizontal rotation movement by means of the theoretical inference of power series.A calculation procedure of rheological parameters was programmed,in which shear rates are amended according to the iteration of shear-rate calculated modes and then rheological parameters are calculated through the regression of revised shear rates.This calculation model was rheologically analyzed and evaluated in terms of hydraulic calculation by utilizing various drilling fluid data and a set of measured hydraulic data.The results show that an unrevised shear rate shows a larger error,while rheological parameters obtained from revised shear rates can describe the rheological behavior of drilling fluids better.The result of hydraulic calculations obtained by using rheological parameters derived from revised shear rates shows a higher calculation accuracy of pressure drawdown by 0.5 MPa,more consistent with measured data by the attached ECD at down hole,thus,this approach is of definite theory and application values.
出处
《石油学报》
EI
CAS
CSCD
北大核心
2012年第1期128-132,共5页
Acta Petrolei Sinica
基金
国家重大科技专项"窄密度窗口安全钻井技术与配套装备"(2011ZX05021-003)资助
关键词
非牛顿流体
流变模式
流变规律
剪切速率
流变参数
水力评价
non-Newtonian fluid
rheological model
rheological law
shear rate
rheological parameter
hydraulic evaluation
