Analysis And Application Of Flow Detection Curve Based On Least Square-Total Least Square Method

With the exploitation of underground oil and gas resources,oil and gas well engineering requires more and more precision of cementing mud flowmeter.Because some detection errors cannot be reasonably avoided in design,automatic correction based on detected results is the key to improve the measuring accuracy of flowmeter.BLTD cementing flowmeter is a new product designed by Shenyang Baiyun Machinery co.,ltd according to the specific requirements of a drilling company in Liaoning Province.BLTD cementing flowmeter has been applied to some cementing operations.But,detection accuracy is still inaccurate under different external environmental impacts.It needs to be controlled by experienced operators on cementing site.There is an urgent need to develop viable alternatives.The purpose of this thesis is to analyze the causes of errors according to the particularity of mud flow detection based on the cementing test data collected in different environments,and to establish a reasonable mathematical model for the testing curve of cementing mud flowmeter,so as to expand the testing range of the flowmeter and improve the detected accuracy.In this thesis,two new methods,Recursive Fuzzy Weighted Least Squares(RFWLS)and Clustering Algorithm Least Squares-Total Least Squares(CA-LS-TLS),are proposed based on Least Squares and Least Squares-Total Least Squares.Various methods are used to fit the test data,and the fitting effect was compared with the correlation coefficient.A better curve fitting effect is obtained by using CA-LS-TLS method.Based on the tangential turbine structure of this type of flowmeter,the control equation of impeller is deduced,and the comprehensive detection model of this flowmeter is established.At the same time,the consistency between the fitting results and the theoretical model is verified.In order to eliminate the influence caused by pressure change and medium viscosity,the flow characteristic curve and the inertia interval data are modified and compensated by the piecewise linear interpolation method and the impeller inertia theorem according to the linear relationship between the data.It makes the flow detection model of BLTD cementing mud flowmeter lower limit,wider range and better repeatability..The cementing flow data collected by several groups were used in the experiment,and the results show that,when both independent variables and dependent variables have errors,the curve fitting errors of RFWLS method and CA-LS-TLS method are smaller than existing curve fitting methods,and the advantages of CA-LS-TLS method are more obvious.The flow detection error can be controlled within 5.12%,which can fully meet the needs of engineering applications by improving the fitting accuracy and error compensation.The fitting method proposed in this thesis is general,which can significantly reduce the error of curve fitting.The established model and method can also provide certain theoretical basis for the design of other tangential turbine flowmeters.