Study On Optimal Design Method Of Multilateral Well Trajectory

Multilateral well is a drilling technology, which can use the horizontal well and the direction well drilling technology to improve the recoverability of reservoir. According to the term of the reservoir, it can design the well and proceed the distribution of the hole's room, to improve the level of comprehensive exploitation of the reservoir, by means of effectively increasing the bare area of the reservoir, increasing the valid drilling footage of the hole, saving drilling investment, sufficiently utilizing the upper hole of the well, and at last, to access the aim of improving recoverability. Based on surveying and studying the many documents, the paper simply analysis correlation technology of the multilateral well which in the world .Based on this, the paper introduced the basic principles of multilateral well drilling engineering design and the calculation methods of multilateral well trajectory design ,setting up calculation methods of multilateral well main borehole and branch borehole. The paper combined previous calculating methods of the friction torque, based on the features of multilateral well trajectory, using the method which combined the friction tourque soft model and rigid model. Because the well trajectory is often three-dimensional, so the paper established two friction torque rigid model: the friction torque rigid model in 2-D bending hole and 3-D bending hole. .At the same time , using the calculating methods of cubic spline interpolation deal with actual wellbore trajectory data which provide favorable data support for multilateral well friction torque calculation and intension calibration. According the characters of multilateral well trajectory, the paper proposed a general ideal for the optical design of the multilateral well trajectory, and established the optimal trajectory model for multilateral well main hole and branch hole separately, and introduced the Mathematical programming theory into the optimal model's solution. The paper through designed experimental well trajectory which optimizing the design parameters of multilateral well trajectory. The paper analyzed the relation of angle between branch hole and original hole. and discussed the variation trend of the shortest straight line distance caused by different build-up rate which under certain branching angle and research the mutual change between branching angle and build-up rate and straight line distance. The paper analyzed the variation trend of build-up rate caused by branching angle s variation which in different vertical depth. Meanwhile the paper researches the variation trend of azimuth difference and deviation difference and vertical depth difference which in different tool face angle. Finally, the paper presented empirical parameters which can instruct the design of multilateral well trajectory, which surely have the guidance for optimizing the design parameters of multilateral well trajectory.With the future study, the multilateral well drilling technology will have more broad application prospect in oil-gas field development.