Types Of Horizontal Wells


1 -10 deg/100ft


10-30 deg/100ft


>90 deg/100ft

There are five recognized types of horizontal wells that have evolved for reasons of hydrocarbon reservoir requirements or to designate the equipment required to drill the wells. For example, long-radius wells are drilled with standard directional equipment while short-radius wells require an assortment of special equipment. The types of wells have become known as:

  1. Long-Radius
  2. Medium-Radius.
  3. Short-Radius
  4. Tangent
  5. Combination

The long-radius, medium-radius, and short-radius wells are shown in the figure. The figure contains their individual attributes. These types have a single build section. It may be noticed that for the same final departure of the well, the short-radius type of well will intersect more pay formation.

However, torque and drag of the drill string may curtail the final departure length of the short-radius well. The horizontal section will, in most cases, be less than 500 feet.

The tangent horizontal well is shown in the figure. Note that the straight section is tangent to both of the circular sections at each of its ends.

The tangent well is popular because it allows the searching of the formation into which the horizontal section is to be put; that is, the final small turn is not completed until the eminent drilling of the pay formation is assured.

Whereas, the prior three types are a hit or miss proposition once the drill hole is kicked off. However, the tangent well may have a shorter productive interval than the other types.

Horizontal Wells

If a lease boundary or a reservoir terminator exists, the short-radius and the medium-radius wells will give longer horizontal pay sections.

Drilling TangentDrilling Tangent

The combination horizontal wells usually contain a long-radius in the upper build, a tangent section, and a medium-radius in the bottom build. The long-radius may reduce costs for the upper and major build while the tangent section in conjunction with the medium-radius or short-radius bottom build gives assurance of drilling the horizontal section in the most favorable location in the pay zone.

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