Design method for relief well trajectory to avoid side-track operations and control the relative distance

Abstract

A blowout can cause significant damage to both property and the environment. The relief well is the final and most helpful option to intercept and stop the blowout. However, the relief well trajectory design methods are still closely guarded by oil companies. Compared with conventional directional wells, additional design parameters such as relative azimuth and relative distance need to be considered in the relief well trajectory design. Therefore, designing the relief well trajectory with conventional methods is challenging. Moreover, side-track operations occur frequently in relief well engineering. Quantifying and reducing side-tracking risk is also an urgent problem to be solved. A new relief well trajectory profile is established based on the dual-2D well trajectory to address these challenges. The design parameters are determined in this profile. Then, a side-tracking risk calculation model is developed based on the well trajectory control theory and error theory. To minimize the side-tracking risk, a design parameter optimization method is established. The relief well “pass-by” trajectory is designed with this new design method. The result shows that, with this optimization method, the relative distances and relative azimuths can be determined in the following and intercepting phases. The relative distances between the relief well and target well are verified. The result shows that the new relief well trajectory can meet the requirements of relative distance. The traditional design method and the new design method are compared. The result shows that the new design method can effectively avoid complicated trial calculations and control the relative distance. In this paper, an effective design method for the relief well trajectory is established. The optimization objective of side-tracking risk is introduced into the relief well trajectory design method, which provides a new way for design parameter optimization. The relief well trajectory design method with a directional target well and new optimization objectives should be paid attention to in further research.