What is directional drilling?

Directional drilling plays a vital role in maximizing the subsurface resource extraction while minimizing the surface impact. Before drilling begins, extensive advance analysis, engineering design and planning are necessary. Subsurface interpretation, which involves geology and geophysics, depicts what lies beneath the surface and the location of oil and gas deposits, along with their associated uncertainties.

Once the interpretation is established, a well plan is developed outlining the intended trajectory of the wellbore. The trajectory is designed to efficiently drill the well—minimizing torque and drag while avoiding potential risks such as existing wellbores—and access the desired reservoir column. The directional driller’s role is to follow this plan, employing a combination of science and engineering to navigate the complexities of drilling through multiple formations, traversing the planned well path and reaching the target coordinates. Real-time adjustments are often necessary because conditions can change unexpectedly during the drilling process. Adjustments are made within agreed tolerances and anti-collision limits, typically coordinated with the drilling and geology teams and documented in the daily report.

The two technologies most commonly used to steer wells toward their targets are the bent motor and the rotary steerable system (RSS). The bent motor is a technologically less complicated, more affordable option that allows operators to adjust the direction of the wellbore by controlling the orientation of the toolface (the bend direction) while sliding downhole. However, in longer, higher-inclination wells, bent motor steering can be limited by toolface control, slide efficiency, torque and drag, and hole-cleaning constraints.

In contrast, the RSS is a more advanced and costly technology that uses downhole sensors and control mechanisms to steer the drillbit while rotating. This system allows for greater precision and control over the drilling trajectory, making it particularly useful for extended-reach wells. RSS often delivers smoother wellbores, which can reduce drag, improve the casing running and enhance the overall drilling efficiency.

Bent motors are common where cost and simplicity dominate, while RSS is selected when smoother wellbores, tighter tolerances or complex 3D trajectories justify the added cost. Often, the key decision is selecting the trajectory and steering approach that meets the target, anti-collision requirements, and cost and time objectives.

Advances in digital systems are transforming how directional drillers understand and react to downhole conditions. Real-time data, automated tools and emerging artificial intelligence models now support faster detection of dysfunction, such as stick-slip, whirl, bit bounce or high vibration, which are conditions that can lead to tool damage or failure.

Using machine learning to analyze real-time drilling data helps detect early warning signs so the team can adjust parameters and prevent downhole issues, protecting tools and maintaining the wellbore’s trajectory and hole stability.

Additionally, improving the communication between different service providers and software platforms through standardized real-time data streams (e.g., wellsite information transfer standard markup language) and integrated operations centers enhances the operational efficiency because multiple companies with unique software are involved in the drilling.

These technologies enable faster dysfunction recognition, fewer tool-damage events and better consistency in the trajectory execution, strengthening operational safety and improving the drilling performance while potentially improving the asset economics.

The views reflected in this article are the views of the authors and do not necessarily reflect the views of Ernst & Young LLP or other members of the global EY organization.