Research On Correction Design Method Of Borehole Trajectory In Non-straight Wells

With the deepening of oil exploration and development,the difficulty and risk of drilling are increasing,and the problem of trajectory deviation of non-straight wells is becoming more and more serious,which seriously affects the drilling efficiency and safety.Therefore,it is becoming more and more important to modify the trajectory of non-vertical wells.The purpose of hole trajectory correction is to make the actual drilling trajectory closer to the design trajectory,thus improving the quality and efficiency of drilling,providing more reliable basis for subsequent drilling work,and also helping to reduce drilling costs and risks.Borehole trajectory prediction and trajectory deviation analysis are qualitative and quantitative monitoring while drilling processes.It is judged whether the trajectory of the borehole to be drilled is about to deviate by predicting the traveling trend of the borehole trajectory,and whether the deviation between the trajectory of the borehole to be drilled and the designed trajectory exceeds the preset range by using the deviation analysis method.If the predicted trajectory deviates from the designed trajectory and the deviation exceeds the set threshold,the appropriate trajectory correction design method is called to correct the deviation,so as to realize accurate drilling state control of the borehole trajectory.Based on the comprehensive investigation of literature and the collection of field data,this paper studies and summarizes the current conventional methods of borehole trajectory prediction and trajectory correction.In view of the problem of single data analysis and large error in geometric prediction method of borehole trajectory,a non-straight borehole trajectory prediction model based on BP neural network is established,which can predict the drilling parameters of the section to be drilled and then get the trajectory trend.Through the error analysis of an example,it can be concluded that the average relative error of BP neural network prediction is about 4%,which is more accurate and practical than geometric prediction.A three-step analysis method of borehole trajectory deviation in non-straight wells is proposed to define the deviation degree of predicted trajectory.This method is faster and more convenient than projection diagram and normal scanning diagram.By determining the corresponding point of each sub-point on the predicted trajectory on the designed trajectory,then evaluating the predicted trajectory data and the designed trajectory data,calculating the deviation evaluation value,and verifying whether the normal distance,the X and Y offsets are within the allowable error range.If the deviation exceeds the threshold,the trajectory correction design is carried out.By studying the conventional design method of borehole trajectory correction,taking the shortest trajectory as the performance index,the deviation point and tool deviation ability as the design variables,and taking the accuracy of the middle target and the boundary of the design variables as the constraint conditions,two-way alignment method and single arc method are proposed for the design method of borehole trajectory correction for non-straight wells.Starting from the current measured terminal point,the next target area is taken as the target point,and according to the data such as vertical depth,azimuth change rate and deviation change rate,single arc is used.The research in this paper can provide technical reference for trajectory correction of non-straight wells under different working conditions,improve drilling efficiency and reduce drilling cost and risk.