Natural Gas Fields and Exploration Techniques

Dry Gas Fields

In these, gas is the main product. These are sites that contain hydrocarbons in the gaseous phase but produce no liquid formed by changes in pressure and temperature. The gas is generated through a process of expansion, similar to what occurs in cylinders, where the amount of gas associated with pressure gives embaçada.

Associated Gas Deposits

The gas produced in oil fields, gas-oil, and condensate is called associated gas, since it is produced jointly with liquid hydrocarbons. The gas generated in dry gas fields is called non-associated gas or free gas, and liquid parts are minimal.

How to Locate a Gas Site

When underground accumulations of oil or natural gas are likely to exist, a series of steps follows to locate the site most likely to contain them for later extraction. The geologist's main job is to identify the conditions under which oil and gas accumulate. To do this, they use different methods of exploration, the most important being:

Geological Methods

These involve studying surface rocks for direct indications, such as volumes or springs of petroleum, asphalt, and gas. Surface geology is applied to verify the existence of rocks associated with the origin and storage of hydrocarbons and to interpret the existence of traps in the soil by observing and measuring their impact on the ground. To this end, aerial photographs are also used. The surface geology studies require a prior survey that provides a relief map. On this map, geologists plot the acquired data to interpret the subsoil and its petroleum possibilities.

Geological Methods (Continued)

These involve studying surface rocks for direct indications, such as volumes or springs of petroleum, asphalt, and gas. Surface geology is applied to verify the existence of rocks associated with the origin and storage of hydrocarbons and to interpret the existence of traps in the soil by observing and measuring their impact on the ground. To this end, aerial photographs are also used. The surface geology studies require a prior survey that provides a relief map. On this map, geologists plot the acquired data to interpret the subsoil and its petroleum possibilities.

Geophysical Exploration Techniques

• Gravimetric Method: Measures variations in the gravitational force depending on the density of rocks.
• Magnetic Method: Measures local variations in the magnetic field and, accordingly, can determine the distribution of rocks containing different magnetic properties.
• Seismic Reflection Method: Measures the properties of rocks to transmit sound waves from a trigger, which travel faster in hard rock and compact soft rock.