Optimization Design In Cluster Horizontal Wells Trajectory

With the progress of Factory-like drilling, using cluster horizontal wells to develop low permeability oil and gas fields, unconventional oil and gas fields and marine oil and gas resources has become the consensus of petroleum engineers. Wellbore trajectory design is one of the key technologies in cluster horizontal wells drilling.This paper has done the following work of optimization design in cluster horizontal wells trajectory, based on the research results of former experts. Firstly, depending on different optimization targets and principals, this paper studies on methods of selecting the optimal corresponding relation between wellheads and targets and optimizing wellheads arrangement of single platform. Using disjoint and minimum distance menthod, this paper selects the optimal corresponding relation between the wellheads and the targets, which will not only ensure that there is no collision between the tracks of single-well cluster horizontal wells, but also initially ensure the shortest of the single well trajectory cluster horizontal wells. According to designing the horizontal wellbore direction is consistent with minimum horizontal principal stress direction, to meet the needs of offset distance, this paper selects the optimal wellheads arrangement by parallel distribution.Secondly, by considering the influence of friction resistance during cluster horizontal wells drilling, combining with current conditions of cluster horizontal well technologies and devices in Changqing Oilfield, this paper analyzes the relationship between offset distance and friction resistance. By considering constructability, this paper holds the first research on the impact of offset distance on wellbore trajectory design, puts forward the principles and methods of offset distance design of shallow cluster horizontal wells, provides the solutions of the problem of failure; Basing on reducing the risk of cross-collision, by choosing the minimum length of anti-collision intervals as the optimal index, this paper establishes cluster horizontal wells drilling sequence mathematical optimization model, and provides the optimal drilling sequence using the method of space geometry.Finally, based on optimization theory, the new model regards the length of trajectory as its objective function, in which main factors affecting trajectory design are considered, in order to KOP, build up rate, inclination and azimuth angle as the design variables, with the target accuracy, formation conditions, the design variables boundary as constraint conditions, such a cluster horizontal well borehole trajectory optimization design model is established. Matlab optimization toolbox fmincon function is used to solve the optimization design model, and it is verified to be rational and accurate by example calculate, which can be used as auxiliary tool for wellbore trajectory design.