In the world of oil and gas extraction, drilling is a fundamental activity. It is the process by which wells are created to access underground oil or gas reservoirs. These resources are obtained primarily through two methods: onshore drilling and offshore drilling, the so-called Onshore e offshore accounts. See how each one works:
Difference between onshore and offshore oil extraction
The main difference between the two modalities lies in the location of the reservoirs. While onshore exploration occurs on dry land, offshore exploration occurs offshore, in deep waters. In Brazil, offshore production, especially in the pre-salt layers, is the leading source of oil and gas extraction.
In practice, onshore exploration involves drilling wells on land to extract oil and natural gas from underground reservoirs. Historically, this method launched the Brazilian oil industry, particularly in the Recôncavo Basin in Bahia.
Offshore exploration, on the other hand, is carried out at sea, using gigantic and complex platforms. It is currently the main frontier of Brazilian production, responsible for most of the country's oil and gas extraction.
How does onshore drilling work?
Onshore drilling takes place on land, in regions where oil reserves can be accessed from the surface, such as deserts, plains, or forests. Operations begin with geological surveys and data analysis to identify potential oil reservoirs.
After the site is selected, drilling rigs are transported and installed onshore. They can vary in size and complexity, depending on the depth and geological characteristics of the well. The process involves inserting a drill bit fixed to the base of a drill string, which rotates to cut through layers of rock and sediment until it reaches the oil-bearing formations.
During the process, drilling fluids—known as mud—circulate through the drill string, lubricating the drill bit, cooling the equipment, and bringing rock fragments to the surface. As the well is deepened, steel casings are installed and cemented to ensure stability and safety.
Once drilling reaches the planned depth, the well undergoes evaluation and testing to determine its potential productivity. If deemed commercially viable, it enters the completion phase, with the installation of equipment that prepares it for oil or natural gas extraction.
Pros of onshore drilling
- Cost-effectiveness: In general, onshore drilling is more cost-effective than offshore operations.
- Accessibility: logistics on land are simpler, with easy access to equipment and teams.
- Consolidated technology: as it is a centuries-old technique, it relies on extensive knowledge and mature practices.
Cons of onshore drilling
- Land use conflicts: may compete with agricultural, residential or environmental activities.
- Environmental impact: risks of soil and water contamination, in addition to environmental degradation.
- Public opposition: noise, land occupation and environmental risks generate resistance in local communities.
What is offshore oil exploration like?
To meet global demand for fossil fuels, companies in the sector have invested billions in developing offshore operations, expanding their frontiers in search of new reserves in the ultra-deep waters of the oceans.
Offshore drilling presents unique challenges due to adverse weather conditions, water depth, and the need for high-tech equipment. Drilling rigs are installed on fixed platforms, semi-submersible structures, or drillships, depending on the depth and conditions of the marine environment.
The procedure is similar to onshore drilling, with the main difference being the environment and complexity of the operation. Drilling fluids remain essential for lubrication and transport of rock cuttings, while directional drilling techniques allow access to reservoirs located at different angles beneath the seabed.
Once the well is completed, it undergoes testing and evaluation. If approved, it enters operation with strict safety protocols to protect the environment and the teams working on the platform.
Pros of Offshore Drilling
- Access to large reserves: enables the exploration of extensive oil and gas fields in deep-sea areas.
- Fewer territorial conflicts: reduces interference with urban and agricultural activities.
- Technological advances: allows operations at previously inaccessible depths.
Cons of offshore drilling
- High costs: requires high investments in technology and maintenance.
- Technical challenges: Extreme conditions increase complexity and operational risk.
- Strict regulation: subject to more restrictive environmental and safety standards.
What about oil extraction in Brazil?
Onshore oil exploration played a crucial role in the history of the sector in Brazil. The first commercial production began in Bahia in 1939, with the Lobato field. Since then, activity has expanded to Rio Grande do Norte, Sergipe, and Espírito Santo.
In recent years, the onshore sector has gained new momentum. With Petrobras' sale of onshore fields, opportunities have emerged for independent and mid-sized companies, which have invested in technology and the recovery of mature wells—areas that still hold productive potential.
Despite the onshore expansion, the majority of national production is concentrated offshore. Offshore platforms, especially in the Campos, Santos, and Espírito Santo basins, are responsible for Brazil's leading role in the sector. And pre-salt is the biggest highlight.
Discovered in 2006 in Brazil, this geological layer, located more than seven thousand meters deep beneath thick layers of salt, contains an estimated 70 to 100 billion barrels of oil and natural gas. This solidifies the country's position among the countries with the largest reserves in the world.
The Tupi field, in the Santos Basin, was a milestone for the pre-salt layer. Technological advancements have reduced costs by up to 40%, and a single well can produce over 50 barrels per day, demonstrating the strength of Brazilian offshore production. This information is from the federal government.
The Brazilian exploration is divided as follows:
Onshore exploration: Alagoas, Amazonas, Bahia, Ceará, Maranhão, Rio Grande do Norte and Sergipe concentrate mature and traditional fields, many of them in operation for decades.
Offshore exploration: Espírito Santo, Rio de Janeiro and São Paulo are home to the country's largest reserves, including the pre-salt layer.
Read also where does oil come from
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