Analysis of the Relative Position Uncertainty in the Intersecting Process of U-Shaped Horizontal Wells

To effectively use RMRS to guide the accurate intersection of two U-shaped horizontal wells,the relative position uncertainty in the intersecting process was analyzed.According to the guiding process of RMRS for well intersections,the relative position uncertainty was divided into two parts:the relative position uncertainty between the bottomhole being drilled and the measure point by RMRS,and the relative position uncertainty between the intersection point and the measure point by inclinometer.The covariance matrix of relative position uncertainty caused by RMRS and the inclinometer was obtained by using a borehole position uncertainty model.Through the conversion of coordinates,the total covariance matrix was obtained in the same coordinate system,and then the error ellipsoid and error ellipse were determined on the basis of the total covariance matrix.From the example it could be determined that when the distance from bottom-hole drilled to the intersection point was 101.84 m,the lengths of semi-axes were 3.75,1.90 and 2.66 m respectively.With the drilling operation,when the distance from bottomhole to intersection point was 10.00 m,the lengths of semi-axes were 0.25,0.56 and 0.07 m.The result indicated that the relative position error measured by RMRS was no longer cumulative but decreased gradually.The analysis of relative position uncertainty being made simultaneously would help the realization of the intersection of two wells,and guide the use of RMRS effectively.