Methods in obtaining the most
from oil and gas reservoir
(Onshore)
Definition: What is “onshore”?
Onshore refers to the mainland. In exploration and
production, “onshore” refers to the development of oil
fields, gas deposits and geothermal energy on land.
In the wind energy sector, “onshore wind farms” generate
energy with windmills installed on land. Since the energy
turnaround, the term “onshore” is often used in Germany
for the generation of renewable wind energy using wind
farms and wind power plants.
Onshore oil extraction, gas extraction,
geothermal
The onshore extraction of crude oil and geothermal energy
requires drilling into underground deposits. The targeted
search for crude oil, natural gas and geothermal deposits is
called prospecting.
Compared to offshore extraction, the onshore extraction of
oil and gas is less elaborate and more cost-effective.
Special methods such as seismic reflection are used for the
exploration of crude oil, natural gas and geothermal
deposits. Mature onshore fields are commonly used for
crude oil extraction in Germany, frequently distinguishing
themselves with a broad maximum extraction volume and a
long extraction phase.
Conventional onshore oil extraction
In conventional extraction, one differentiates between
primary, secondary and tertiary extraction depending on
the degree of difficulty.
Unconventional onshore oil extraction
Since the number of conventional deposits is decreasing,
crude oil is increasingly being extracted from
unconventional deposits such as oil sands or oil shale.
Onshore services and onshore project
management
For crude oil, natural gas and geothermal exploration and
production, many natural gas and crude oil as well as
geothermal companies engage special service providers
(companyman) with in-depth exploration know-how and
years of practical experience for the efficient management
of regulations and processes as well as cost reduction.
EDPSolutions assists companies in the crude oil, natural
gas and geothermal industries in the extraction of crude
oil, natural gas and geothermal energy with professional
project management and project support.
Onshore Drilling
Drilling into the Earth in the hopes of uncovering valuable resources is
nothing new. In fact, the digging of water and irrigation wells dates back to
the beginning of recorded history. At first, these wells were primarily dug by
hand, then by crude stone or wood tools. Metallurgy brought about the use
of iron and bronze tools to delve beneath the Earth’s surface, and
innovations led to more efficient ways of removing debris from the newly
dug hole. The first recorded instance of the practice of ‘drilling’ holes in the
ground came about around 600 B.C., when the Chinese developed a
technique of repeatedly pounding bamboo shoots capped with metal bits
into the ground. This crude technology was the first appearance of what is
known today as ‘percussion drilling,’ a method of drilling that is still in use.
Much advancement has been made since these first bamboo drilling
implements. This section will cover the basics of modern onshore natural
gas drilling practices.
There are two main types of onshore drilling. Percussion, or ‘cable tool’
drilling, consists of raising and dropping a heavy metal bit into the ground,
effectively punching a hole down through the earth. Cable tool drilling is
usually used for shallow, low pressure formations. The second drilling
method is known as rotary drilling, and consists of a sharp, rotating metal
bit used to drill through the Earth’s crust. This type of drilling is used
primarily for deeper wells, which may be under high pressure.
Cable Tool Drilling
Cable tool, or percussion drilling, is recognized by many as the first drilling
method employed to dig wells into the earth for the purpose of reaching
petroleum deposits and water. This method is still in use in some of the
shallow wells in the Appalachian Basin, although rotary drilling has taken
over the bulk of modern drilling activities.
The basic concept for cable tool drilling consists of repeatedly dropping a
heavy metal bit into the ground, eventually breaking through rock and
punching a hole through to the desired depth. The bit, usually a blunt,
chisel shaped instrument, can vary with the type of rock that is being
drilled. Water is used in the well hole to combine with all of the drill cuttings,
and is periodically bailed out of the well when this ‘mud’ interferes with the
effectiveness of the drill
bit.
Cable tool drilling has
historically taken many
forms. In the early days of
percussion drilling,
equipment was very crude
compared to today’s
technology. The
‘springpole’ technique,
used in the early 1800s,
consisted of a flexible pole
(usually a tree trunk)
anchored at one end, and
laying across a fulcrum, Early Percussion Rigs in Pennsylvania –
much like a diving board. Late 1800’s
The flexible pole, or Source: Office of Fossil Energy, DOE
springpole, would have a heavy bit attached at the loose end. In order to
get the bit to strike the ground, workers would use their own body weight to
bend the pole toward the ground, allowing the bit to strike rock. The tension
in the pole would spring the bit free, in case it became stuck in the ground.
Many improvements have been made since these early percussion rigs. In
fact, it was from cable tool drilling that one of the most important drilling
advancements was made. In 1806, David and Joseph Ruffner were using
the springpole technique to drill a well in West Virginia. In order to prevent
their well from collapsing, they used hollow tree trunks to reinforce the
sides of the well, and to keep water and mud from entering the well as they
dug. They are credited as the first drillers to use a casing in their well – an
advancement that made drilling much more efficient and easily
accomplished. It is believed by many that ‘Colonel’ Drake’s 1856 well
achieved success due to the use of steel casing to reinforce the well.
Drake’s well was drilled using steam powered cable tool drilling methods.
For more information on well casings, and well completion, click here.
Innovations, such as the use of
steam power in cable tool drilling,
greatly increased the efficiency and
range of percussion drilling.
Conventional man-powered cable
tool rigs were generally used to drill
wells 200 feet or less, while steam
powered cable tool rigs, consisting
of the familiar derrick design, had
an average drilling depth of 400 to
500 feet. The deepest known well
dug with cable tool drilling was
completed in 1953, when the New
York Natural Gas Corporation
drilled a well to a depth of 11,145
A Modern, Mobile Cable Tool feet.
Drilling Rig Despite the historical significance of
Source: Anadarko Petroleum Corporation
cable tool drilling, modern drilling
activity has shifted mainly toward rotary drilling methods. However, the
foundation of knowledge laid by years of cable tool drilling is, in many
cases, directly transferable to the practice of rotary drilling.
Horizontal Drilling
Horizontal drilling is flexible in that it allows for the extraction of natural gas
that had previously not been feasible. Although on the surface it resembles
a vertical well, beneath the surface, the well inclines so that it runs parallel
to the natural gas formation. These legs can go in different directions at
different depths and can be more than one mile long horizontally, in
addition to the vertical well that can be thousands of feet below the
surface. Horizontal drilling allows one surface well to branch out
underground and tap many different natural gas resources. It also allows
the well to make contact with larger areas within productive formations.
As of result of
advances in
horizontal drilling
natural gas
resources in shale
basins has been
more accessible
leading to more
diversified sources of
natural
gas. Combining this
with other
technologies such as
seismic imaging has Horizontal Well and Drill
Source: National Energy Technology Laboratory, DOE
contributed to lower
marginal operating and capital costs, which in turn allow natural gas
producers to more economically extract natural gas from resources.
Horizontal drilling also permits the development of natural resources with
minimal aboveground disturbance, reducing the environmental footprint of
natural gas operations and the cost and potential disturbance of existing
roads or other infrastructure. Directional drilling and horizontal drilling
terms are often used interchangeably. Directional drilling refers to drilling
at a slant or angle to increase contact with the resource. Horizontal drilling
is a type of directional drilling. Horizontal drilling uses a technique known
as hydraulic fracturing in order to extract natural gas from geologic
formations. For more information please visit our hydraulic
fracturing section.
Diagram of a petroleum onshore drilling rig
nshore Oil Drilling
The days of “black gold” squirting out are history
Oil exploration initially meant drilling relatively shallow holes more or less straight
down. This is the symbolic picture of the “easy oil” era. Today, oil companies use
sophisticated directional drilling to drill snake and weave-shaped undergrounds to find
pockets of oil and increase recovery from a single well. The days of the oil pump
turning continuously and “black gold”
just squirting out are history.
The drilling of bores into underground formations is accomplished using an elongated
"drill string" built from a number of tubular drill pipe sections coupled at their ends,
which carries the drill bit or other cutting tools. The drill string extends from the
surface into a well or "wellbore", which is formed by the rotating drill bit.
The drill string, which frequently contacts the surrounding bore hole casing, inevitably
suffers from frictional wear, shock and abrasion, causing similar damage to the
surrounding casing. If this persists, the casing is worn thin and will eventually rupture.
A shut-down is then necessary, with lengthy and expensive remedial work before the
casing is restored to a fully effective condition. Frequently, the productive life of a well
is wholly determined by the integrity of its bore hole casing.
