Wellbore Cross-collision Risk Analysis And Visualization

In the recent years,the technology of infill wells and cluster wells is widely used,the distance between wells becomes more and more smaller,unexpected wellbore cross-collision accident occurred Wellbore cross-collision risk evaluation has a significant meaning to wellbore anti-collision.Currently,the indexs to evaluate the risk of wellbore collision include wellbore distance,separation factor,collision probability,and each index also contains a variety of calculation methods.However,most of the calculation methods have only theoretical mathematical model,which can not apply in the drilling site.In this paper,it reappears the mathematical process of various calculation methods,according to the existing mathematical model,and shows the detailed calculation process,which have a support to selective the evaluation indexs.Wellbore separation factor is the most common index to evaluate the risk of wellbore collision.Because the index considers the effect of wellbore error,it is more reliable than the minimum distance index.However,all existing computing methods can only evaluate the separation degree of two ellipses on some a plane,and can not directly evaluate the separation degree of two ellipsoids in 3D space,and lead to over-optimistic or over-conservative evaluation results inevitably,and can not satisfy the drilling requirements.Therefore,a new computing method to wellbore separation factor is presented,which zooms two error ellipsoids by the same scaling up to their exterior contact condition,then select the zoom coefficient as the wellbore separation factor.The new method can directly and accurately evaluate the separation degree of two error ellipsoids in 3D space.A quadratic equation set with four unknown parameters is derived and discussed,as well as its numerical solution method and some tactics to accelerate its solution speed.Then,the new method is completely feasible,not only on the theory,but also on calculation.An instance analysis shows that,the new method can preferably evaluate the risk of wellbore collision.It can contribute to pinpoint dangerous intervals,decrease the anti-collision workloads.Using the MATLAB R2014 a software,this paper programs the software of “Wellbore cross-collision risk evaluation”.The calculation methods of wellbore cross-collision risk evaluation indexes are all programmed to evaluate the risk of cross-collision between the wellbore.Using the software,we could get the separation factor evaluation results,the diagram of horizontal projection,vertical projection and three-dimensional trajectories containing the wellbore error ellipsoids.The software provides an advanced measure for the evaluation of the wellbore cross-collision risk.