Petroleum Exploration

 

Although the concession contracts includes all phases of the activity of the petroleum industry - Exploration - Development & Production (Exploitation) - the reality of the country, in relation to this sector of economic activity, is very incipient, that is, all contracts signed with the Portuguese State, more than a hundred, since 1938, never crossed the first phase corresponding to exploration.

 

The exploration phase aims at geological investigation and aims to identify geological resources or delimit areas with greater potential and targets for future more detailed research work, expanding knowledge about the national territory - in the case of petroleum, Portuguese sedimentary basins and its eventual petroleum systems, with the main objective of making a commercial discovery.

 

The acquisition of new geological and geophysical data implies high investments, fully supported by the Concessionaires, resulting in greater and better knowledge of the national geological infrastructure and particularly of its sedimentary basins.

 

All these geological and geophysical data acquired, processed and interpreted are delivered to the State in documental, graphic and digital support and in physical support - rocks and sediments samples, thin sections, microfossil cells, and, which, after a period of confidentiality, become available for the country.

 

For decades this data has been reused by various areas of geosciences, various national and international institutions, public or private, allowing a geological mapping, either onshore or offshore, production of geological cartography, seismic risk assessment and seismic vulnerability of infrastructures, risk assessment of underwater landslides and consequent formation of tsunamis, valorization of other geological resources, physical characteristics of the marine substrate for infrastructure implementation, climate change, paleoceanography, etc.

 

They also allow for the development of many dozens of academic works, including masters, doctorates and post-docs, and the pursuit of research work for the development of new assessment methodologies.

 

Exploration usually starts with the acquisition of indirect data through geophysical methods, such as gravimetry and magnetometry, used mainly in the initial recognition phase of sedimentary basins, to obtain, quickly and economically, information about the depth of the basement (thickness of the sedimentary cover) and the general features of the structure of the basin.

 

 

 

Example of Total Magnetic Intensity (TMI) map – extracted from Lusitanian Basin Structural GIS & SEEBASETM Study, February 2012 - FrOGTech. Main Report and Appendix.

 

At a later stage and still in geophysical methods, seismic data survey or acquisition phase follows, which aims to obtain indirect data on the subsurface geology, compared to echographic and tomographic images of the human body, with a view to identification of sedimentary strata and geological structures that favor the accumulation of petroleum.

 

 

Example of seismic section acquired and processed in 2000-2002.

 

 

Seismic line interpretation. The ages are hypothetical due to the lack of wells in the deep offshore of the Peniche and Alentejo Basins

 

After an idea of the dimension, depths, contours of the sedimentary basin, places with better characteristics, structures and geological traps through the processing and interpretation of indirect data obtained through geophysical methods, such as those mentioned above, direct data acquisition follows, which in geology means the collection of geological samples, in this case, through the sampling of sediments from the bottom of the sea and/or exploration drilling.

 

Exploration wells usually take place after acquisition of geophysical data, as it generally involve very high investments, in the order of tens to hundreds of millions of euros, and are only carried out after careful interpretation of the acquired data and after identifying targets with potential.

 

Exploration wells are carried out locally and temporarily (usually from 1 week to three months) occupying an area of the order of 1,000 m².

 

 

Exploration well in Aljubarrota, using state-of-the-art technology. Soundproofed well.

 

In the context of activities for the study and characterization of the geological resource "petroleum", it is important to give the true meaning to the Anglo-Saxon terms "exploration" and "exploitation", which have raised some doubts, and their correct translation into Portuguese, being that both terms designate different phases of petroleum activity, as follows:

 

the term “exploration” should be translated as “pesquisa” (sensu lato) or “prospeção e pesquisa” (sensu stricto);

 

  and the term “exploitation” for “produção/extração” (sensu lato) or “desenvolvimento e produção” (sensu stricto).