Spatial Position Detection Method Of Horizontal Section Of Dual Horizontal Wells Based On Adjacent Casing String Magnetic Field

Steam auxiliary gravity drive(SAGD)technology is widely used in the development of heavy oil and ultra-heavy oil reservoirs.Among them,the parallel horizontal wells group production method contributes the most to the recovery factor.The key to the implementation of this technology is that the horizontal section of the two horizontal wells is accurately controlled using ranging positioning techniques.Currently,active magnetic ranging technology such as rotating magnetic ranging system(RMRS)rotating magnetic field ranging guidance system or magnetic electromagnetic guidance tool(MGT)is mainly used,which requires double wells operation and has low measurement efficiency,high time and economic costs.The passive magnetic ranging technology can detect the relative azimuth and distance of the adjacent well casing by using the magnetic field characteristics of the casing string.This method can work in a single-well to effectively improve the drilling speed of horizontal wells and save costs by using measurement while drilling.Therefore,its application prospect for SAGD dual horizontal wells steering drilling is very broad.This paper mainly focuses on the improvement of the theoretical model of casing string remanence,the feasibility analysis of passive magnetic ranging for parallel horizontal wells,and the inversion method of casing string space position in adjacent parallel horizontal wells.First,the fitting method of the theoretical model of the casing string remanence was optimized.The theoretical model of the remanence around the casing string was improved in consideration of the influence of the casing coupling,and the experimental verification was carried out.The improved model is used to simulate and analyze the magnetic field around the unmagnetized the magnetized casing strings.Second,the influence range of the residual and induced magnetic field of the casing string,the detectable range of magnetic anomalies and the magnetic field gradient distribution around the casing string are analyzed.Finally,based on the genetic algorithm and Kalman filter algorithm,a method for calculating the space position of the casing string in the adjacent well and the error correction method are established.Compiled supporting software,the main functions include the forward analysis of the magnetic field around the casing string,the inversion calculation of the space position of the adjacent well casing string,and error correction.The research results show that the improved remanence model around the casing string can more accurately describe the remanence distribution around the casing string.Three situations: in-phase magnetic pole connection of unmagnetized casing string,out-of-phase magnetic pole connection of magnetized casing string and in-phase magnetic pole connection are applicable to SAGD dual horizontal well passive magnetic ranging technology.The magnetic field gradient can be used to determine the relative position of adjacent casing.The axial change rate of the total magnetic field can play an auxiliary role.The distribution law of the axial gradient of the magnetic field around the casing string and the axial change rate of the total magnetic field is the same with different sizes.For the first time,a combination of genetic algorithm and Kalman filter is used to establish a method for detecting the spatial position of the horizontal section of a double horizontal well based on the magnetic field around the adjacent casing string.The ground measurement test verifies that the method can effectively inversely calculate the space position of the adjacent well casing string.