Magnetic Location Technology For Reference Wells Based On MWD Data

With the increasing difficulties in oilfield development and the continuous development of petroleum exploration and development technology,the drilling process is increasingly faced with challenges,and the demand and precision requirements for interwell positioning are also getting higher.Among the many positioning methods,the passive magnetic positioning method has the advantages of simple operation and not occupying the adjacent well.However,there are still some shortcomings in the establishment of the magnetic positioning model and magnetic interference,which affect the accuracy of passive magnetic positioning.The magnetic positioning technology based on MWD in an adjacent well has a wide range of practical engineering needs and application prospects in oilfield drilling operations.Therefore,it is of great theoretical and practical significance to carry out research on its key technologies.This thesis contains the following studies:(1)A magnetic distance measurement and positioning system while drilling is designed.The magnetic field matching between the residual magnetic data of an adjacent well and the theoretical magnetic field model is established in order to solve the distance and azimuth between forward drilling and the adjacent well.For the problem of poor convergence when the two wells are within the same plane,another passive magnetic positioning model based on MWD data is proposed for when the adjacent well casing is in the same plane with the forward drilling.The validity of the theoretical model is fully verified by ground experiments.(2)A method to remove multi-field magnetic interference in the process of downhole positioning is proposed.A method for calculating magnetic interference of BHA by using demagnetization factor of the model is studied and the method reasonably assumes the BHA as a long ellipsoid.For magnetic interference other than that of the BHA,the Kalman filter is used to eliminate the influence of magnetic interference on the calculation of the relative position between wells.(3)Based on the magnetic positioning model and the multi-field magnetic interference removal method,a set of anti-collision software for magnetic ranging while drilling was developed,which realized automatic calculation of the location of the adjacent well based on MWD data.The effectiveness of the system and the practicability of the software are verified by the field experiments.Ground experiments show that the greater the distance between the casing and the survey line,the lower the positioning accuracy.When two wells are at different surface positions,the positioning accuracy decreases with the increase of the Angle between wells and the vertical distance between different surfaces.The mathematical model analysis shows that the magnetic interference of BHA on the fluxgate sensor decreases obviously with the increase in length of the non-magnetic drill collar segment,and the magnetic interference of the BHA on the fluxgate sensor is the least when the distance between the sensor and the bottom of the drill collar is 1/2-2/3 of the total length of the drill collar.It is found that when the range of magnetic positioning technology based on MWD in the adjacent well is less than 7 m,the error is less than 10%.