Research On Anti-collision Monitoring Technology Of Cluster Well Based On Three-component In Transient Electromagnetic Method

As oilfield mining is in full swing,cluster wells are getting more and more popular in drilling and mining projects.As the downhole space is limited,the probability of wellbore collisions gradually increases with the increasing of the well trajectory.Anti-collision scanning of the cluster wells is an effective method to prevent and decrease the wellbore collision.Currently,the main anti-collision scanning methods are horizontal plane scanning method,normal plane scanning method and minimum distance scanning method.All these three methods in the anti-collision scanning work apply the principle of electromagnetic detection.However,the first two methods can only scan in a specific direction,so the scanning distance is not necessarily the minimum distance in space.Therefore,the minimum distance scanning method is widely used,but this method has disadvantage in precision.In order to improve the precision of scanning,this paper makes some improvements on the basis of the minimum distance scanning method.The three-component detection technology of transient electromagnetic method is proposed in this thesis.The improvement of the accuracy is studied from two aspects in this thesis.Firstly,accuracy is improved in the calculation method.The disadvantage of the separation factor currently used is that during the calculation,the error in the drilling process is not taken into account,making the calculated results too conservative and wasting the downhole space.In order to improve the calculation accuracy and reduce the collision probability,the error of the wellbore drilling is taken into account in the definition calculation of Oriented Separation Factor(OSF).The example verifies that the OSF calculation result is higher than the SF,proving that the Oriented Separation Factor can effectively improve the calculation accuracy.According to the value of OSF,anti-collision is divided into four levels.Secondly,the accuracy is improved from the detection method.When detecting the underground environment,the detection principle which is based on the transient electromagnetic method of Maxwell’s equations is not limited by the environment.In the electromagnetic detection system,the core element is the eddy current in the formation.The size of the eddy current is related to the conductivity of the formation.Therefore,the induced electromotive forcegenerated on the induction coil is also a function of the conductivity of the surrounding formation.The analyzed detected voltage signal can be converted into formation conductivity.In order to subdivide the downhole detection area more carefully and reduce the detection blind area,a transient electromagnetic three-component detection system is proposed.Compared with the transient electromagnetic,the structure of this detection system adds two horizontally perpendicular coils in the horizontal direction.The coaxially wound transceiver coils are on three mutually perpendicular probes,simultaneously transmitting three directions of AC signals,and receiving three cross signals.With the detection signal in the direction,nine magnetic field components can be obtained,and the relationship of nine magnetic field components can be obtained by the Maxwell equations.According to the three-component detection system,the adjacent well casing distance and azimuth detection model is established.According to the established model,the relative distance and azimuth of the two wells are obtained,and combined with the calculation method of the directional separation coefficient,the maximum safety distance can be calculated with high precision,effectively realizing the anti-collision monitoring of the cluster wells.On the basis of the above theory,a three-dimensional simulation model of the three-component detection system is established based on the physical parameters of the actual oil well casing in the experimental part.Meanwhile,a large number of simulation experiments are carried out for the parameters affecting the detection performance.According to the experimental results,the sensitivity and accuracy of the detection system can be proved.It proves the practicability of the three-component electromagnetic detection system and provides theoretical foundation for further application and study.