Learning Objectives
After completing this topic “Horizontal Drilling”, you will be able to:
- What is horizontal drilling used for?
- Why is horizontal drilling better?
- What is vertical and horizontal drilling?
Introduction
Horizontal drilling is the process of directing part of a well course through a reservoir such that its inclination angle is approximately 90° from vertical. This horizontal section may be anywhere from a few feet to thousands of feet in length.
Horizontal wells can trace their roots back to at least the 1930s (Ranney, 1939). But it was not until the 1980s that advances in directional drilling and formation evaluation brought them into the mainstream of oil and gas operations. Since then, in a number of fields, they have significantly outperformed conventional wells in terms of increased productivity, improved ultimate recovery and lower overall development costs.
There have also been disappointments along the way, which have shown that the benefits of horizontal drilling are not all-encompassing, but are contingent on reservoir characteristics.
Horizontal Drilling Applications
Horizontal wells work to best advantage in thin reservoirs having a relatively high ratio of vertical to horizontal permeability (vertically fractured formations are prime candidates) and a potential for drawdown-sensitive production problems like sand production water and gas coning.
Other common candidates for horizontal drilling are:
- Reservoirs that would otherwise be economically inaccessible.
- Heavy oil reservoirs.
- Channel deltaic sand and reef core reservoirs.
- Coal bed methane reservoirs.
- Increasing reservoir contact within the reservoirs.
- Unconventional shale, tight oil & gas reservoirs.
Figure 1 illustrates some typical applications of horizontal well technology.
The remainder of this section focuses on drilling methods and considerations for horizontal wells. For a detailed discussion of horizontal well applications that addresses the reservoir management, formation evaluation, completion and stimulation aspects of this technology, the reader may refer to Economides (1993), or to the subject titled ” Horizontal Wells: Completion and Evaluation,” under the topic heading “Well Completion and Stimulation.”
