Oil and gas: extraction steps, types of drilling and samples generated - Core Case

Oil and gas: extraction steps, types of drilling and samples generated

In Brazil, the first survey with the objective of finding Petroleum was carried out in São Paulo, between 1892-1896, by Eugênio Ferreira de Camargo. It reached a depth of 488 meters, but the well produced only sulfurous water. It was only in 1938 that oil was discovered in Lobato, Bahia.

In 1968, the first oil field was discovered on the Brazilian continental shelf, in Sergipe. Since then, many wells have been drilled.

Would you like to know more about the oil, extraction steps, drilling and samples generated in this process? Read this content until the end.

A Brief Introduction on Petroleum

Petroleum is a complex mixture of hydrocarbons and varying amounts of non-hydrocarbons. In short, it is generated from the transformation of organic matter accumulated in sedimentary rocks, when subjected to appropriate thermal conditions.

Oil platform.

When it occurs in the liquid state in subsurface or surface reservoirs, it is called oil (or crude oil, to differentiate it from refined oil). 

The mixture of hydrocarbons that is in the gas state on subsurface and turns into liquid on the surface is known a condensate. 

Now the term natural gas refers to the fraction of oil that occurs in the gaseous state or in solution in oil in subsurface reservoirs.

Oil extraction steps

Oil is an abundant natural resource, but its research involves high costs and complex studies.

An oil well can be considered as an engineering project, thus, it requires that a series of premises and variables be obeyed, so that the intervention is optimized in time, cost and adequate safety.

Drilling equipment.

Oil, like any mineral good, has well-defined stages for its extraction to be carried out. Here we can briefly summarize 3 of them: prospecting, drilling and extraction.


This step is the first to be carried out and aims to carry out studies and apply methods that identify the existence of oil in a given location. These analyses are carried out in sedimentary basins and several direct and indirect methods are used. For this, geologists, geophysicists and paleontologists, among other specialists, gather to carry out the necessary research.


At this stage, oil deposits are discovered and several wells are drilled in the surroundings to define the limits of the deposit and assess the volume of reserves. Drilling is a destructive process, where a drill bit advances over the rock formation, breaking it into centimeter to millimeter fragments. 

It can be done on land, using drilling rigs, or at sea, with the help of offshore platforms, depending on where the mineral is found.


Extraction is influenced by the amount of gas accumulated in the deposit. If it is large, it will be able to push the oil to the surface, without the need for pumping, at least in the initial phase of production, simply by installing a pipe that communicates the well with the outside. If the gas pressure is weak or zero, extraction pumps will be needed.

Types of perforation

During this process, several drillings can and should be carried out in the project in order to find new oil deposits or even to understand in detail the extent of the current explored deposit. Check out some types of perforations:

  • Pioneer well: well drilled at the beginning of research for oil/natural gas;
  • Stratigraphic well: aims to map the stratigraphy of the region;
  • Extension or delimitation well: as the name implies, this type of well is made to enlarge or demarcate the limits of a deposit;
  • Adjacent Pioneer Well: aims to discover new deposits close to an area that has already been explored;
  • Well for shallower deposits: this is done with the aim of finding out if there are shallower deposits than those already discovered in a given area;
  • Well for a deeper deposit: this is done with the aim of discovering if there are deeper deposits than those already discovered in a given area;
  • Production or development well: well that allows the drainage of oil from a field;
  • Injection well or injector: aims to increase or improve the recovery of oil and natural gas from a reservoir;

In addition to the concepts mentioned above, we can classify the type of drilling according to the direction:

  1. Vertical well: probe and target (or objective) are vertical;
  2. Directional well: any well in which drilling is not performed vertically;
  3. Horizontal well: made horizontally, especially to ensure better use of oil.

Type of perforation according to direction. Source: Instituto Fisiomar

Samples of rocks and fluids generated in the oil and natural gas exploration and production process

Samples are portions of rock, sediment or fluid extracted from the well, from the ocean floor surface or from the land surface.

According to the ANP, the following samples are collected within the scope of oil and natural gas exploration and production activities in Brazilian sedimentary basins:

  • Core samples and their respective plugs;
  • Gutter samples;
  • Side samples;
  • Fluid samples;
  • Rocks or sediments obtained from land or ocean floor surveys.
  • Thin, biostratigraphic blades and polished sections;
  • Sample profiling;

Sample types. Source: Petrocase – Core Case


Fractions, generally cylindrical, obtained from cores and normally used in petrophysical tests to determine the porosity and permeability of a reservoir rock.

Gutter samples

Biostratigraphic: Type of blade that is prepared with special techniques for the preservation, concentration and recovery of the fossiliferous content of a rock. The analysis of such blades essentially aims at the relative dating and the determination of the sedimentation paleoenvironment.

Thin: A type of blade that is prepared with rock fragments polished to a thin thickness and intended for observation with a transmitted light petrographic microscope (provided with adaptations for microscopic analysis of rocks).

Both aim to determine the mineralogical content of the rock and its microstructures.

Side samples

Samples obtained from the wall of the well, approximately cylindrical in shape, whose acquisition aims to preserve the structure of the rock and provide security as to the depth of the extraction.


Substances that do not resist tangential or shear forces, deforming continuously and taking the shape of the container in which it is contained. Examples: water, gas and oil.

Core sample

Sample obtained in a well, usually of cylindrical shape, whose acquisition aims to sample specific strata of rock, preserving its structural characteristics, and with precision in the extraction depth.

Core Case and its performance in the Oil and Gas sector

CORE CASE is a Brazilian-Canadian company with 11 years of existence that has consolidated itself in the mining market and is present in the most important companies in the segment. 

Our purpose is to add value to the production process of the largest companies in the extraction of natural resources (mining, oil and gas), prioritizing long-term sustainability. 

See in the video below the solutions we have developed for the oil and gas sector.

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