Directional drilling helps to minimize surface disturbance or avoid disturbance in sensitive or special areas. Wells do not have to be drilled perfectly vertical. Directional drilling techniques exist that allow wells to be drilled at angles (slant hole wells); allow wellbores to curve sideways (horizontal wells); or to have more than one curve (S-curve or deviated wells).
Benefits of Directional Drilling
Horizontal and vertical well on one pad, Vermejo Park Ranch
The benefits of directional drilling are numerous. Using these techniques, companies can drill a number of wells in different directions from one well pad (multilateral wells), which can decrease overall surface disturbance by reducing the number of well pads required to drain an oil or gas field.
Studies also show that directional drilling has been successful in a variety of geological formations (e.g., shallow reservoirs, deep reservoirs, tight sands, coal beds, tar sands). Furthermore, if horizontal drilling is used in coal beds, there may be no need to hydraulically fracture the beds, resulting in a decreased potential for groundwater pollution.
Directional drilling diagram. Credit: Geology.com
Perhaps the greatest benefit to the surface owner, or for the protection of sensitive ecosystems, is the ability to locate well sites away from residences or other areas that should not be disturbed. It is now possible for companies to access oil or gas by drilling a well that is miles away from a specific property or site.
A major benefit to the companies and mineral owners receiving royalties is increased oil and gas production. Oil- and gas-bearing formations tend to be more wide than they are deep, consequently, wells that intersect a producing formation at an angle or horizontally often can drain more of the oil and gas than purely vertical wells. There are numerous studies showing that directionally drilled wells have been able to extract 2- 25 times more oil or gas than vertical wells drilled in the same oil or gas field.
The drilling of a directional well is more costly than drilling a typical vertical well because it requires specialized equipment; constant attention to the placement of the drill bit; it takes several days longer to drill the wells; and pumping costs may increase because parts may wear out faster. According to the U.S. EPA, however, the increased costs of directional drilling are often more than offset by increased production and the reduced need for drilling multiple wells.
In the Dundee Formation of Michigan, as much as 85 % of the known oil remained in the formation after many years of production, but many wells were on the verge of being plugged because daily production had fallen to only five barrels of oil per well. The U.S. Department of Energy co-sponsored a project to drill a horizontal well in the formation. This well produced 100 barrels per day. The program attracted other well developers, and 20 to 30 additional horizontal wells are being drilled in the formation. It is estimated that the application of horizontal drilling to this formation may yield an additional 80 to 100 million barrels of oil.
In the Ignacio-Blanco field of the San Juan Basin of Colorado, the typical spacing of coalbed methane wells is one well per 160 or 320 acres. In 2005, several companies approached the Colorado Oil and Gas Conservation Commission because they wanted the ability to drill one well per 80 acres in order to extract the methane.
The COGCC granted the companies the ability to have 80-acre DOWNHOLE spacing. On the ground surface, however, the companies were required to drill the new well from an existing pad (which they are allowed to enlarge, but only slightly). In other words, the SURFACE spacing will remain at one welllpad per 160 acres.
While it does not explicitly mention "directional drilling," in practice, In order to access the gas from an existing pad the companies in La Plata County are going to have to directionally drill.
Read the COGCC Order No. 112-180, which outlines the requirement to drill from an exisiting (or "common") pad.
Read the Memorandum of Understandings signed by BP and La Plata County, which also includes a provision to drill from existing well pad unless that is found to be "impractical."
For more information:
- Molvar, Erik, M. 2003. Drilling Smarter: Using Directional Drilling to Reduce Oil and Gas Impacts in the Intermountain West.
U.S. Environmental Protection Agency (U.S. EPA). October, 2000. Profile of the Oil and Gas Extraction Industry. EPA Office of Compliance Sector Notebook Project. EPA/310-R-99-006. p.72.