Study On 3-D Trajectory Design Of Shale Gas Horizontal Well With Considerations Of Directional Drilling Limit And Target Accuracy

The Fuling shale gas field is located in Southeast of Sichuan Province in China,where is covered with mountains and has complex geology condition.It is difficult to accurately predict the vertical depth of the target reservoir before drilling,which increases difficulty in hitting the target accurately.Large cluster horizontal well technology is the advanced well type and engineering model for efficient development of shale gas in Fuling area.However,it is limited by drilling technology and equipment capacity these days,which brings the number restriction of horizontal well on a single platform and increases the design difficulty of the outermost well on the platform.In view of the above problems,this paper comprehensively considers the factors such as target accuracy and extension limit,establishes a set of 3-D trajectory optimized calculation method for horizontal wells.Firstly,based on two-buildup three-dimensional trajectory design method,the slope of the twist-azimuth-section and the control deviation of the tool face was presented to optimize the trajectory,and the track of the deviation correction section is added to modify the three-dimensional twist-azimuth-section trajectory design.Secondly,considering the influence of reservoir vertical depth prediction error,the transition section is added to modify the trajectory design of the target section,which establishes a 3-D trajectory optimization design model of horizontal well that considering the accuracy to hit the target.Thirdly,choose the outermost well as the research objectives,a multiobjective trajectory optimization design model of three-dimensional horizontal well is established accounting for the various constraints such as the lateral extension limit,the drilling time and wellbore potential energy.This paper uses genetic algorithm to solve the model.which is solved by genetic algorithm.Finally,based on those conclusions,a platform for horizontal wells considering extension limit and target accuracy is developed.The above research can provide quantitative calculation and theoretical guidance to large scale the large cluster wells in mountainous areas of China.