用多元回归法预测水基绒囊钻井液当量静态密度

Prediction of equivalent static density of water-based fuzzy ball drilling fluids with multiple regression method

王金凤 郑力会 韩子轩 邓金根

WANG Jinfeng ZHENG Lihui HAN Zixuan DENG Jin’gen

中国石油大学石油工程教育部重点实验室，北京　102249

MOE Key Laboratory of Petroleum Engineering in China University of Petroleum, Beijing 102249, China

由于地层温度、压力的影响，预测水基钻井液井下当量静态密度比较困难。水基绒囊钻井液的囊核包裹一定量气体，温度和压力不仅影响基液密度，而且影响囊核体积，使得井下当量静态密度变化规律更加复杂。室内研究首先用PVT实验仪测定密度为0.85 g/cm3的无固相绒囊钻井液在1~20 MPa、30~130 ℃下的密度，然后利用多元回归法处理测定的220个密度数据点，建立绒囊钻井液不同井深时的井下静态密度预测模型。此模型相关系数0.96、相对误差小于5%，可信度高。用该模型计算2 500 m井深时绒囊钻井液密度与磨80-C1试验井实际测量结果比较，相对误差小于4%，表明此模型可预测井下水基绒囊钻井液的当量静态密度。

Being affected by formation temperature and fluid column pressure, it is difficult to predict the equivalent static density (ESD) of water-based drilling fluids. It is more difficult to predict the downhole ESD variation law of water-based fuzzy ball drilling fluid due to the ball cores wrapping a certain amount of gas, making the formation temperature and fluid column pressure affect not only the density of based liquid, but also the volume of ball cores. A downhole ESD prediction model for fuzzy ball drilling fluids in different well depths is established by firstly performing a laboratory PVT experiment to test the density of the solid-free fuzzy ball drilling fluid with standerd state density of 0.85 g/cm3, under the pressure range of 1~20 MPa and the temperature range of 30~130 ℃, and then processing the 220 density data points with the multiple regression method. The correlation coefficient is 0.96 and the relative error is below 5%, and the reliability is high. There is a 4% difference between the density calculated by the model at the depth of 2500 m and the actual measurement result in M80-C1 test well, indicating that this model can be used in downhole ESD prediction.