Horizontal oil and gas
drilling has become one of the most valuable technologies ever
introduced in the business. It is an
enhanced oil recovery (EOR) or gas recovery method that is becoming more and more
popular as the price per barrel of oil gets higher.
Unlike a directional well that is drilled to position a reservoir entry
point, a horizontal well is commonly defined as any well in which the
lower part of the well bore parallels the oil zone. The angle of
inclination used to drill the well does not have to reach 90° for the well
to be considered a horizontal well. Applications for horizontal wells
include the exploitation of thin oil-rim reservoirs, avoidance of
drawdown-related problems such as water/gas coning, and extension of wells
by means of multiple drain holes.
Cost experts have agreed that horizontal wells have become a preferred
method of recovering oil and gas from reservoirs in which these fluids
occupy strata that are horizontal, or nearly so, because they offer
greater contact area with the productive layer than vertical 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.
To give an idea of the effectiveness of horizontal drilling, the U.S.
Department of Energy indicates that using horizontal drilling can lead to
an increase in reserves in place by 2% of the original oil in place. The
production ratio for horizontal wells versus vertical wells is 3.2 to 1,
while the cost ratio of horizontal versus vertical wells is only 2 to 1.
Three main types of horizontal wells:
Horizontal oil drilling can be used in many
situations where conventional drilling is either impossible or cost
prohibitive. This is by no means an exhaustive list, but it should get you
thinking about the possibilities of horizontal directional drilling.
well drilling can be used in these scenarios:
under buildings, roads, and
other surface obstructions under active sites where surface operations precluded drilling
equipment (Airports and Highways)
to efficiently extract soil vapor
to identify the causes of decreased well performance
to place leak detection sensors beneath solid or hazardous waste
to install gas collection systems at landfills or similar waste dumps
to stabilizing hillsides for mine waste dumps or other unstable
granular soil masses
to dewater hillsides where mudslides endanger housing developments
to install groundwater collection galleries in shallow aquifers for
private or public water supply
to convey fluids between vertical wells and treatment facilities