Research On Risk Classification Method Of Wellbore Cross-collision

In the past,the major oilfields can develop oil-gas reservoirs by drilling vertical wells,and there is no problem of wellbore collision.With the continuous development and application of directional drilling technology,drilling construction is facing increasingly severe risk of wellbore collision.Before the drilling operation,the risk of wellbore collision is evaluated,the risk level is divided,and the corresponding risk control measures are taken to prevent and resolve the risk,which can not only ensure the downhole safety,but also reduce the management cost.The research on risk classification method of borehole collision provides systematic theoretical support for“improving quality,speed and efficiency”of drilling engineering,and has important guiding significance for avoiding downhole accidents and improving risk management ability.In this paper,according to the characteristics of drilling operation,the concept and types of borehole collision are described comprehensively and systematically,and analyzed the causes of the accidents in detail.Combined with drilling practice,this paper introduces the specific operation methods of two kinds of borehole anti-collision technology,and puts forward some measures and suggestions,which provides a practical basis for the selection of wellbore collision risk assessment index and the establishment of evaluation index system.Secondly,this paper uses the relevant functions of COMPASS software and MATLAB software to evaluate the common wellbore collision risk evaluation indexes,and points out the shortcomings and limitations of various calculation methods of separation factors.Based on many experts of a certain directional technology company,a variety of expert questionnaires are designed,and identified the risk factors of borehole collision by Delphi method,and the evaluation indexes are preliminarily selected.According to the definition of risk,the indicators are divided into possibility index and severity index,which lays the foundation for the establishment of evaluation index system.Then,using AHP to calculate the weighted coefficient of the risk evaluation index of the borehole collision,and the indexes are quantified and the score is determined,and structured the evaluation index system of the risk of wellbore collision.Based on the theory of risk matrix,a risk matrix model of wellbore collision is developed,which is suitable for field anti-collision construction.There are targeted control measures for each level in the model.Finally,combined with the drilling construction example of Shengli Oilfield,the risk matrix model is used to divide the risk level,and various targeted control measures are taken to reduce the risk level,which effectively eliminates the hidden dangers of downhole accidents and plays a good role in collision prevention and early warning.It is proved that the risk classification method of wellbore collision studied in this paper has high field application value.