Oil drilling rigs are the backbone of our modern society. These modern tools, which allow us to locate and extract crude oil from the ground, are also responsible for the flourishment and prosperity of many nations.
However, understanding the complex world of oil drilling is no easy task. The various terminologies and types of drilling rigs can confuse most industry veterans.
In this article, we explain the science behind oil drilling rigs and discuss their operating procedure and the challenges behind oil drilling.
State of the Oil Industry in 2024
The first quarter of 2024 has seen a decline in crude oil demand. With the rise in the adoption of electric vehicles and a general shift towards renewables, the IEA estimates gasoline (petroleum) demand to decrease by 25% in 2024 and 31.25% in 2025.
While the demand has decreased, the price of a barrel of crude oil has increased in Q1 of 2024.
The oil and gas industry has invested in new technologies over the last 15 years, which have significantly improved annual oil production.
However, the reduced demand for oil and natural gas may impact the economies of countries reliant on exporting crude oil.
Some US oil companies are also looking to diversify their energy production portfolio. Fervo Energy has started utilizing its oil drilling equipment to tap into geothermal energy.
Despite the decline in demand, the oil business is still as profitable as ever. Many industries still rely on oil’s convenience and power, and the industry will continue to prosper for the foreseeable future.
What are Oil Drilling Rigs?
Oil drilling rigs are giant industrial structures used to explore and extract crude oil from the earth’s crust. They can also dig water wells and extract natural gas.
Oil drilling sites include onshore oil fields, offshore deposits underwater, and remote uninhabited areas such as deserts or the Arctic regions.
Most oil drilling rigs stand tall at 125 ft., equivalent to a 12-story building, and cover several thousand square feet of land.
Key Components of a Drilling Rigs
- Derrick – Large vertical support structure that holds the drill bit and adds new pipes to the drill wells.
- Drill String—The part of the drilling apparatus that penetrates the ground consists of a drill pipe, drill collars, and a drill bit.
- Drill Bit – The cutting tool is tied to the end of the drill string. It’s made of strong materials (tungsten, diamond, carbide steel, etc.) and comes in several shapes and sizes.
- Mechanical Drivers – Motors that provide the rotary motion to the drill bit, move the drill string up and down and lower the pipes into the drill hole.
- Electricity Generators—Large diesel generators power the drilling rig. They drive the mechanical motors and oil pumping mechanisms and power the monitoring equipment.
- Casing – Metal pipes of varying diameter and length that provide structural integrity to the drill hole.
- Blowout Preventers – Pressure relief valves on top of the drill pipe that prevent the build of excess pressure.
- Mud Circulation System—A system of pumps and pipes that delivers a lubricating mud mixture to the drilling apparatus.
Challenges of the Oil Drilling Process
- Environmental Impact—Oil drilling is a disruptive process. It negatively affects neighboring land, damaging plant life and destroying animal habitats. Oil spills pollute and contaminate the soil and nearby water bodies as well.
- Remote Locations – Most oil rigs, especially offshore drilling rigs, operate in remote locations thousands of miles from shore. Getting supplies to these remote locations can be a financial and logistical nightmare. The job’s nature also necessitates workers staying on the drilling vessel for months.
- Regulatory Compliances—Oil drilling requires high regulation and safety oversight. Businesses must address matters related to the environment, public health, worker safety, etc. The oil and gas industry, in general, must abide by several national and international regulations.
- Worker Safety – Safety on a drill site with several tons of heavy equipment, toxic chemicals, and other hazards should always be a priority. Maintaining worker safety and implementing emergency response plans on a drill site with hundreds of employees is challenging.
- Equipment Maintenance – Drilling rig equipment is reliable and long-lasting under standard operating conditions. However, drilling operations in remote areas like the Arctic will inevitably damage and chip away at the equipment. Rigorous inspections and maintenance protocols are required to keep the production equipment up and running.
How does the Oil Drilling Process Work?
Source: HowStuffWorks
The oil and gas industry follows the same basic steps for identifying and extracting underground energy sources.
Step 1 – Site Survey
Before any real drilling starts, a comprehensive site assessment and land survey is required. Geological surveys using various high-tech equipment help identify potential oil fields.
Engineers and scientists conduct seismic, magnetic, and gravity surveys for months before any drilling or oil production can start.
Step 2 – Rig Setup
Once the site is finalized, drilling equipment is assembled on site.
Equipment includes the machinery for drilling operations, the power supply systems, anchors and other support structures, on-site monitoring rooms/cabins, and various other application-specific setups.
Step 3 – Drilling Process
Oil drilling involves rotating and pushing a drill bit into the earth using a giant mast called a derrick. As the drill penetrates the ground, drilling mud (or drilling fluid) lubricates the drill and increases penetration efficiency.
Drilling mud is a mixture of water, clay, and other additives that help the drill break down hard underground rocks while keeping the drill bit from overheating from friction.
Step 4 – Casing Installation
Casing refers to a series of metal pipes inserted into the drill hole.
The outer pipes provide structural integrity to the hole, preventing it from collapsing, while a series of inner pipes maintain a water-tight seal for oil extraction. New casings are installed after every few hundred feet of hole depth.
Step 5 – Monitoring and Evaluation
The drill site is under constant monitoring and geological surveys that identify underground rock formation, porosity, and moisture levels.
Based on the survey results, engineers evaluate the need for power and drill bit changes.
Step 6 – Extraction Process
After reaching the desired depth (between 6,000 – 40,000 ft.), the drilling rig is moved to the side in favor of extraction equipment.
Special pipes, pumps, valves, wellheads, and other tools extract crude oil from the hole depth to the surface level.
Step 7 – Oil Production
Once the oil well is complete, the production process kicks into high gear. Several thousand barrels of oil and gas can be extracted from the ground daily.
Large oil trucks and sea vessels (for offshore drilling) quickly transport oil from the drill site to a storage area.
Offshore vs. Onshore Oil Drilling
Onshore drilling refers to dry land-based oil extraction processes. On the contrary, offshore drilling extracts resources from the seafloor at various depths.
Onshore Land Rigs
Land drilling rigs are the most basic type of oil production equipment. These massive structures are assembled on-site according to the job needs.
Upon task completion, the rig gets dismantled and transported on heavy-duty trucks to a warehouse or the next drill site.
Offshore Oil Rigs
Offshore oil rigs are designed for underwater drilling and operate anywhere from shallow waters to the middle of the ocean.
Some rigs are intended for fixed installation on the ocean floor, while others have a mobile design that allows them to move from one drilling location to another.
There are several types of offshore oil drilling rigs designed to tackle the various challenges of the sea.
Every Type of Offshore Oil Drilling Rig
Offshore oil drilling rigs come in all sizes and shapes. Rig designs range from small fixed platforms to massive floating production systems.
1. Jack-Up Rigs
Jack-up oil drilling rigs are mobile structures designed for shallow water operations. The floating drilling rig is towed to the desired location, and support legs reach down to the sea bed, anchoring the right and pushing it upward.
Once the job is done, the support legs will retract, freeing the drilling vessel.
2. Barge Rigs
Barge-type drilling rigs are the most minor type of offshore oil rigs. These mobile oil production vessels are designed for very shallow waters, with a depth of around 10-20 ft. Barge rigs have a large hull that floods with water after reaching the desired drilling location, keeping the vessel from drifting.
3. Submersible Rigs
Submersible offshore drilling rigs are the big brother to barge rigs. These floating production vessels have a large pontoon design at the bottom. Pontoons are large cylinders that get flooded with water until they rest on the seafloor.
When drilling operations are done, pontoons expel the stored water, and the submersible rig begins to float. Submersible offshore rigs are ideal for medium water depth, 18-70ft.
4. Semi-Submersibles Rigs
Semi-submersible oil rigs use the same pontoon design with retention cables attached. When filled with water the pontoons dive several feet into the water but don’t touch the seafloor. Instead, a series of mooring lines and anchors are used to keep the rig stationary and tied to the sea floor.
Semi-submersibles increase the operating water depth up to 2,000 ft. (~600m).
5. Platform Rigs
Platform oil drilling rigs, also called fixed platforms rigs, are structures built on water platforms that keep the oil drilling equipment several feet above the water surface. These platforms stand on large metal or concrete legs that touch the seafloor.
A base platform is built on the seafloor, and drilling equipment is brought on board using large ships. Concrete platforms are exceptionally economical for water depths over 500 ft. (~150m).
6. Compliant Towers
Compliant tower offshore drilling rigs use a narrower flexible structure as a platform. These rigs are mobile and can easily be relocated without the need for complete dismantlement of the equipment.
The narrower design of compliant towers allows them to withstand larger lateral forces, making them ideal for deeper waters, 1,000 – 2,000 ft. (~300-600m).
7. Tension-Leg Platform
Tension leg platforms are mobile oil production systems anchored to the sea floor using long and heavy cables. The platform stays stationary due to the cables’ tensile stress, which is also called vertical tendons.
Tension-leg oil drilling platforms can operate in deep waters around 7,000 ft. (~2,100m).
8. Spar Platform
A spar platform has a massive cylindrical base several hundred feet long. The cylinder stays submerged in the water and has grooves along the outer surface that provide stability against ocean currents. The cylinder doesn’t reach the ocean floor. Instead, a series of cables tie the cylinder of the floating vessel to the ocean floor.
The spar platform is an upgrade to the tension leg platform. Adding a cylinder to the drilling rig’s base increases its operational water depth to 10,000 ft. (~3000m).
9. Drill Ships (Floaters)
A drillship is an offshore drilling rig built on a large sea vessel base. It is an excellent choice for mobile offshore drilling operations. The ship is easy to maneuver and can operate in shallow and deep waters.
Its size and onboard equipment determine the exact capabilities of a drillship.
Conclusion
Oil drilling rigs are an incredible marvel of engineering. They are massive structures that operate on land and sea to extract crude oil from deep within the earth’s core.
The extraction process is incredibly challenging, especially in remote locations. Luckily, years of research have improved drilling technology, resulting in specialized tools enabling drilling in the toughest environments.
Businesses looking to buy an oil drilling rig should consider their operating location and choose an appropriate system.
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