Back Drilling — A special craftsmanship of control depth drilling

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What is Back Drilling?

Back drilling, also known as breakback drilling or pullback drilling, is a special technique used in oil and gas drilling to precisely control the depth and trajectory of the wellbore. It involves selectively drilling in the opposite direction, back towards the surface, in order to correct any deviations from the planned well path.

Back drilling enables drillers to keep the wellbore within the target zone, ensuring optimal resource recovery. It is an essential skill for drilling deviated, horizontal, and extended reach wells where precision steering is critical. Though complex, back drilling can save operators time and expenses by eliminating the need to permanently sidetrack or redrill improperly placed wellbores.

Why is Back Drilling Necessary?

Drilling precision is crucial but challenging to achieve consistently. Several factors can cause the wellbore to deviate from its planned path:

  • Natural tendency of the drill bit to drop or drift directionally
  • Differences in rock strength and density
  • Equipment wander and flexing drill strings
  • Formation dip and faults

Without intervention, these deviations add up and can result in a wellbore missing its geological target. Back drilling provides a solution to correct the well path and return it to the sweet spot. Operators may choose to back drill in the following situations:

  • Wellbore is drifting out of the pay zone
  • Approach angle to a horizontal landing is too high or low
  • Planned fork or lateral cannot be properly executed
  • Target reservoir cannot be accessed from current path
  • Well path approaches a geologic hazard or surface location

How Does Back Drilling Work?

Back drilling follows these general steps:

  1. Monitoring the wellbore trajectory using directional survey tools. MWD/LWD systems give continuous measurements.
  2. Identifying deviations from the well plan and deciding if intervention is required. This may be hundreds or thousands of feet along the planned path.
  3. Stopping forward progress and pulling the drill string back to the kickoff point of the deviation.
  4. Adjusting the toolface and inclination and drilling back downhole along the desired trajectory.
  5. Matching the original well path below the kickoff depth and continuing on the well plan.
  6. Further monitoring and back drilling as needed to stay in the target zone.

Precision is vital since the new trajectory must be merged with the existing wellbore. This takes considerable skill and practice by the directional driller.

Essential Equipment for Back Drilling

Advanced tools that give the directional driller better control and visibility are essential for back drilling:

  • Downhole MWD/LWD tools – Provide real-time directional surveys downhole. Critical for early detection of deviations.
  • Advanced mud motors – Allow precise adjustment of bend settings for fine steering. Motors with variable bend angles aid directional control.
  • Rotary steerable systems – Offer continuous rotation and full 3D steering capability. Ideal for intricate back drilling maneuvers.
  • EM steering tools – Electromagnetically interact with formations to steer the bit. Used in combination with rotary steerable assemblies.
  • Jar assemblies – Help transmit jarring forces to free stuck pipe during back drilling.
  • String stabilizers – Centralize drill strings and reduce pipe flexing for improved toolface control.
  • Anti-vibration tools – Dampen downhole vibrations for better steering control and faster ROP.
  • Hole openers – Ream the hole smooth when back drilling to previous depth. Ensures tools can pass through easily.
  • Slick assemblies – Lower friction between drill string and borehole. Aid during pullback to previous kickoff point.

Having versatile, responsive directional control equipment is vital for achieving a precise re-drill and tie-in with the existing trajectory. Real-time data integration is also critical for making fast, informed steering decisions.

Back Drilling Best Practices

While a technically complex process, back drilling can be performed efficiently and effectively by following some industry best practices:

Rigorous trajectory planning – The initial well design and plan should utilize anti-collision modeling with ample clearance from hazards. This provides margin if deviations occur.

**Responsive trajectory management ** – Use high-frequency downhole surveys and promptly act at first signs of deviation. Small corrections early can avoid large back drilling jobs.

Communication with directional driller – Consult with the directional driller to review the planned trajectory and priorities. Keep them informed of geological targets.

Detailed monitoring and analysis – Utilize all data including MWD/LWD, drilling mechanical data and drilling dynamics modelling to gain insights into downhole conditions.

Proactive mitigation of vibrations – Frequent vibration monitoring allows early detection and steps to optimize drilling parameters before undesirable toolface control impacts occur.

Manage doglegs severity – Gradual doglegs implemented during back drilling will allow easier workstring rotation and passage of tools through the curve.

Backreaming and opening the hole – Condition the hole by reaming any ledges and tight spots. Makes redrilling the section faster with less stalling.

Break circulation at shallow depths – When pulling out of hole, periodically circulate bottoms up to verify no obstructions exist before passing pullback points.

Have contingency equipment ready – Have backup assemblies, jars, reamers on hand in case difficulties are encountered during the back drilling operation.

With the right methods and preparations, back drilling can be a highly precise technique for achieving complex well geometries where directional precision matters most.


What are some common challenges faced during back drilling?

Some typical challenges encountered with back drilling include:

  • Going back downhole through tight doglegs
  • Maintaining desired toolface and inclination
  • Stabilizing in narrow target formations
  • Avoiding stuck pipe during pullback
  • Reaming through ledges and tight spots
  • Fishing operations if tools are lost in the hole
  • Logistical issues tripping in/out of long laterals

How is back drilling different from sidetracking?

Sidetracking involves deviating the wellbore from an existing hole by mechanical whipstock tools or milling. It permanently branches away to drill another wellbore. Back drilling redrills in the same hole to correct the trajectory so no permanent sidetrack is created.

How long does a typical back drilling operation take?

The time required depends on depth and complexity. Shallow interventions may take 1-2 days. Deeper operations with long laterals could take weeks. Good planning and procedures can minimize downtime.

What type of directional drilling assembly is preferred for back drilling?

Rotary steerable systems with full 3D steering capability offer the most control. Adjustable bent-housing mud motors also assist with fine trajectory adjustments. EM tools combined with RSS provide added precision.

When is back drilling not ideal and a sidetrack is better?

If the existing wellbore is badly damaged, unstable, or severely deviated, it may be better to sidetrack and avoid redrilling problems. For some trajectories, sidetracking can be simpler than intricate back drilling.

Does back drilling increase the risk of stuck pipe incidents?

Pulling back to previous depths then back downhole can increase chances of differentially stuck pipe. Careful drilling practices and having free-point indicators on all BHA components helps reduce differential sticking risks.