Drilling Methods 101: Conventional vs. Unconventional

07 Apr.,2024

 

Vertical/Conventional Drilling

Vertical, or conventional drilling has been used since the 1800’s to extract gas from reservoirs deep within the earth.

Quite simply, it is just that – a well that is drilled straight down (or vertical) into the earth. Sometimes it is difficult or impossible to set up drilling operations above a natural gas reservoir, for instance, under an urban area in which surface conditions would not be conducive or legally allowed.

Because of these vertical limitations they have the possibility of being resolved through horizontal drilling.

Horizontal/Unconventional Drilling

Horizontal, or unconventional drilling is based off of directional drilling technology where the lower part of the wellbore parallels the oil zone. With this type of directional drilling, oil and gas wells can be drilled at various angles underground.

Horizontal wells have become a preferred method of recovering oil and gas from reservoirs that occupy horizontal strata (or nearly so) because they offer greater contact with the surface area than vertical, or conventional wells. With the ability to steer and maneuver the well in different directions, operators can hit hard to reach areas and stimulate the reservoirs very effectively.

Directional drilling combined with high-pressured injections of organic and inorganic materials into low-permeable shale formations to extract the gas or oil contained therein is the process known as “fracking”. With these injections, the shale rock is cracked to allow the release and flow of the trapped oil and gas from tiny pore spaces back up through the wellbore to the surface.

However, drilling for unconventional natural gas requires a whole set of new environmental issues since it requires more chemicals, more water and more wastewater injection wells.

While the cost factor for a horizontal well may be as much as two or three times that of a vertical well, the production factor can be enhanced as much as 15 or 20 times, making it very attractive.

a-horizontal-well-intersecting-shale-formations

Geology.com outlines a few other applications where horizontal drilling is being used:

 

 

A) Hit targets that cannot be reached by vertical drilling.

Sometimes a reservoir is located under a city or a park

where drilling is impossible or forbidden.

This reservoir might still be tapped if the drilling pad is located on the edge of the city or park and the well is drilled at an angle that will intersect the reservoir.

 

target-can’t-be-reached-by-vertical-drilling

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