How Does an Oil Well Work?

How Does an Oil Well Work?
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Oil is among the more versatile nouns in the English language. Depending on your recent experience and the nature of your everyday life, hearing the word might evoke images of stir-fry cooking, aggressive tanning, or the "thick" and "earthy" smell of an auto-repair shop.

But today, oil – once dubbed "black gold" as a nod to the inevitable vast fortune of anyone who discovered a sizable oil field in centuries past – has something of a bad reputation.

Fossil fuels allowed human civilization to take an unprecedented technological and industrial worldwide leap forward starting in the 19th century, yet oil and its ancient carbon-based cousins are pariahs of a sort today. This is because incontrovertible evidence has mounted to show that oil, for all its value across not only the transportation sector but every other human endeavor as well, is seriously damaging to the environment when burned.

Whatever your ideas may be on how to best address the energy needs of a world with a population topping 7 billion as of 2019, anyone who has ever seen an oil well, even from a distance, can't help but appreciate the sheer engineering triumph involved in pumping something out of the ground that is not only deep within rock, but in rock below the ocean floor itself. Oil wells come in a variety of different types and have a more colorful history than you might expect.

Fossil Fuels and Energy: The Oil Imperative

"Oil" can refer to a number of different substances that are nonpolar and liquid at room temperature. Many types of oil provide nutritional energy. They do not dissolve in water (which is why oil is hard to clean using water alone), as their long hydrogen-carbon chemical chains are hydrophobic ("water fearing"). "Oil" in the present context refers to the stuff that is found in significant concentrations in the Middle East, off the coast of Venezuela, North America and a few other regions.

Oil (also commonly called petroleum, from the Latin from "petra," or rock, and oleum, or oil is one of three primary fossil fuels, the name given to substances formed over many millions of years from living materials, though not from actual fossils. The other two types are natural gas and coal. Together, fossil fuels are expected to provide the vast majority of the world's energy supply beyond 2050 despite voluble concerns from scientists and environmental groups about the planetary warming resulting in part from their combustion.

Electricity, heating and transportation might be considered the main uses of oil and its cohorts, but the reach of fossil fuels extends far into manufacturing, food preparation, cosmetics and other industries as well.

As of 2018, oil was running ahead of natural gas in terms of which was contributing a greater share to U.S. energy consumption, as oil stood at 36 percent to 31 percent for natural gas (and 13 percent for coal, making fossil fuels responsible for 80 percent of U.S. fuel consumed). The increase in the use of the drilling technique known as hydraulic fracturing, or "fracking," to extract natural gas from the ground sparked a surge in that fuel's consumption beginning in the 1990s.

Oil Use in the 21st Century

All indications are that there will be a high demand for properly functioning oil wells for the foreseeable future. As noted, petroleum supplied 36 percent of American energy needs as of 2018, and yielded almost half of all energy derived from fossil fuels. These "internal" figures were subject to rapid shifts in the first fifth of the 21st century, but on the whole, fossil fuels were expected to account for virtually the same share of energy consumption both domestically and globally in 2040.

  • In 2017, the U.S. powered through almost 20 million 44-gallon barrels of crude oil per day. That's 880 million gallons, or over two and a half gallons per person. 

Oil is used – and, for the moment, in most cases required – to move vehicles. (Don't be confused by the terminology: The stuff called "gasoline" comes from petroleum, while natural gas is something else entirely.) It is also used directly to heat buildings and produce electricity. In manufacturing, the petrochemical industry uses petroleum as a raw material to make products such as plastics, solvents and other goods.

History of the Oil Well

Unlike the advent of the telephone, human heart transplantation or the wireless radio, there is no one person who can be credited with being "the" oil well inventor.

Oil wells were being drilled with bamboo in China far back as 347 BCE, and these were ambitious projects: Depths of up to 800 feet were reached using this technology. It wasn't until the 1500s or so that oil taken from the ground was used in the lamps of the day.

The first oil wells reached Europe, Canada and the U.S. in the 1850s, driven by the promise of the nascent Industrial Revolution that relied on previously unimaginable amounts of power production to sustain its own burgeoning growth.

Throughout the 20th century, the introduction of steam-recovery practices, horizontal drilling and finally computerization continued to grow and shape the extraction aspect of the booming oil industry. More production means more and more capable wells, and this has been the result, along with some perhaps predictable "black eyes" on the industry.

  • As of 2016, over 1,500 oil companies had been incorporated in the United States alone.

Where Oil Comes From

How is oil actually located before it is removed from the ground, and how do petrochemical engineers determine whether a located store of oil is worth the expense of withdrawing it from the ground by whatever means is easiest? While most of the attention given to oil wells naturally lies on their visible function, few people understand how anyone knows where to put these imposing structures in the first place.

One especially little-known feature about oil extraction: While it's true that it's found underground, it's not the case that it exists in convenient pools or reservoirs or even flows, like sap in a tree. For the most part, it needs to be removed from the interior of actual rocks, albeit large ones. (Imagine having to have major jaw surgery to have a single troublesome tooth extracted.)

Fortunately for the oil industry, nature does much of the work of making oil available by pushing some of it out of the rocks, which often come under incredible internal pressure. This allows human oil-seekers to find a trail to the main source located deeper within the Earth.

Basic Oil Well Structure

An oil well diagram is required to properly follow the material here, since most of the terminology is unfamiliar to most people.

Every oil well needs to be drilled before equipment can be arranged around the hole, and this is what is meant by the term "drilling rig." After this heavy bore is used to create a hole anywhere from about six inches to three feet wide, the sides of the well are reinforced with casing made from various materials in layers.

The oil well pump apparatus sits above the top of the well, where oil removed from below is directed to one side. This "production tree" looks a little like a horse from the side, and has components with names to match. The bridle connects the rod pushing vertically down into the well to the horse's "head," which redirects force horizontally along a walking beam. A series of elaborate levels, pulleys and gears leads to the prime mover, the source of mechanical power at the opposite end of the production tree.

Types of Oil Well Drilling

Two main techniques are used to drill oil wells today. In horizontal drilling, the idea is to extract oil that happens to be oriented in a mostly sideways direction in relation to the ground. This is the situation most commonly observed in rock shale because of the way the rock itself forms (it tends to fracture sideways under high pressure).

A horizontal drill unit has J-shaped pattern, which means its operators must first figure out how far to drill straight down before heading more horizontally (not a 90-degree turn). Once this depth is ascertained the next step is finding the right angle to optimize access to the oil below and to one side.

In hydraulic fracturing ("fracking"), a newer technique that took off at the close of the 20th century, highly pressurized fluid that contains sand and other rough material is pumped through previously drilled well bores, such as the aforementioned horizontal drilling wells. Despite the success of fracking from an efficiency standpoint, its ecological consequences have made it a target of environmental groups.

For example, over 90 percent of the fluid needed for fracking remains in the ground after it's put there, and the requirement for water is exceedingly high. Other concerns include toxin exposure, ground water and contamination and the lowering of local air quality.

Drilling Rigs

Most of the earlier models considered to be part of the current oil-well era were A-frame rigs, which are still used today, mostly in exploratory missions. There are large-diameter (large-bore) drills used in situations in which surgical precision may not be an issue.

The type of auger (the actual drill part of a drilling tool) used depends on local conditions underground, to the extent these are known or can be predicted. If a sample from a given area is high in ground water, for example, a hollow auger is likely to be chosen. The evaluation and drilling processes are really only different in scale from you deciding what kind of shovel to use to dig a post hole in your back yard.

As you may have guessed, portable oil drilling rigs entered the picture along the way, and a common model weighs a sizable but manageable 265 pounds or so. These can be mounted on trucks as needed.

Oil Well Disasters

On April 20, 2010, an oil rig named Deepwater Horizon, located off the Gulf of Mexico, cradled by the southeastern coast of the United States, exploded, killing 11 workers. In the three months that followed before engineers from the rig's owner, British Petroleum (BP), were able to cap the damaged Macondo well below the rig, an estimated 4 million gallons of crude oil made its way into the ocean, making this the worst mishap of its type in terms of pure scale.

Countless lawsuits followed in the wake of the explosion, the ecological effects of which were severe and still being evaluated a decade later. When such mishaps occur, capping the damaged well becomes a logistical nightmare because of both being below water and the fantastic pressures in play.

Oil Well Drilling Animation

If you want to watch a cartoon-style short movie of an oil well in operation, see the Resources for a YouTube video depicting exactly this. They may be big and unwieldy-looking, but oil wells are elegant and elaborate machines, any consequences from their zealous deployment notwithstanding.

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