The objective of this work was to develop a workflow to execute open hole sidetracks in the lateral section of horizontal wells, as an alternative to sidetracking against a mechanical barrier such as cement plugs or whipstock systems.
The methodology implemented for sidetracking in open hole without mechanical deflection consists in three phases:
(1) Well planning to kick-off and deviate from the original wellbore against a suitable lithology and achieve a trajectory with manageable tortuosity.
(2) Designing specific bottom hole assemblies (BHA) to execute the sidetrack and return to the target geosteering window. It was necessary to refine the geomechanical and structural models of the reservoir to predict and anticipate BHA response to the target lithology.
(3) Executing specific drilling practices including time-drilling, surveying, torque & drag and wellbore cleaning monitoring. All of this until the sidetrack BHA was confirmed to be in the new trajectory.
To date, four wells have been successfully sidetracked without mechanical deflection in unconventional fields operated by YPF.
A reference procedure was developed, following the success of operations in which the sidetrack was performed in a single run, lateral sections were then drilled to TD with a different BHA optimizing ROP and geosteering demands as usual, casing was run through the KOP and reached final depth without issues.
This procedure incorporates specific parameters and conditions derived from the accumulated knowledge and experiences of previous experiences. Its implementation in future lost in hole scenarios is expected to mitigate the adverse impact of these events, contributing to overall operational efficiency and cost effectiveness of each project.
When drilling horizontal wells in unconventional reservoirs, it might become necessary to sidetrack from the original wellbore within the lateral section, in the event of a lost in hole incident, in which BHA or casing components cannot be retrieved. This is known to be a more convenient solution in terms of surface facilities and overall project costs compared to drilling an entire new well.
