Directional drilling

Directional drilling is the art and science involving the intentional deflection of a wellbore in a specific direction in order to reach a predetermined objective below the surface of the earth

• At one time it was thought that all wells were vertical
• Methods to measure deviation were developed in the 1920’s (initially acid bottle)
• Directional drilling developed after 1929 when new survey instruments were available (inclination and direction)
• The first controlled directionally drilled well was drilled in the Huntington Beach Field in 1930 to tap offshore reserves from land locations
• Directional drilling became more widely accepted after a relief well was drilled near Conroe, Texas in 1934

• Today, directional drilling is an integral part of the petroleum industry
• It enables oil companies to produce reserves that would not be possible without directional drilling
• One of the primary uses of directional drilling was to sidetrack a well even if it was to go around a stuck BHA

 

• Sometimes multiple sidetracks are used to better understand geology or to place the wellbore in a more favorable portion of the reservoir
• Straight hole drilling is a special application of directional drilling

1. To keep from crossing lease lines
2. To stay within the specifications of a drilling contract
3. To stay within the well spacing requirements of a developed field

 

• Drilling multiple wells from a single structure or pad
• Most offshore development would not be possible without directional drilling
• Inaccessible surface location
• Drilling in towns, from land to offshore and under production facilities

• Drilling around salt domes
• Salt can cause significant drilling problems and directional drilling can be used to drill under the overhanging cap
• Steeply dipping sands can be drilled with a single wellbore
• Fault drilling
• In hard rock, deviation can be a problem
• Sometimes the bit can track a fault
• Drilling at a higher incident angle minimizes the potential for deflection of the bit
•  Relief well drilling
• Directional drilling into the blowout when the surface location is no longer accessible
• Very small target and takes specialized equipment
•  Horizontal drilling
• Increasing exposure of the reservoir to increase productivity
•  Multilateral drilling
• Drilling more than one wellbore from a single parent wellbore

•        Extended reach drilling wells are characterized by high inclinations and large departures in the horizontal plane

• Extended reach wells are wellbores where the horizontal departure is significantly higher than the true vertical depth of the well, which is the horizontal departure – TVD ratio (HD/TVD)
• Extended reach wells have been drilled with HD/TVD ratios greater the 6/1.
  BP drilled a well at Wytch Farm with a measured depth of 34,967’ (10,658 m), a TVD of 5,266’ (1,605 m) and horizontal departure of 33,181’ (10,114 m) 
  
  

  
  

  
  

  
  

  •    There are four basic hole patterns
  •      Not all wells conform to the basic hole patterns and may be a combination of patterns
  •     For simplicity, the basic hole patterns are defined as:
  • 
  •