Giuseppe Bolondi
AGIP SpA
Milan
A knowledge of the structure of the earth's deep crust, down to 3040 km is at the basis of our understanding of the geological processes that have given rise to the formation of mountain chains and sedimentary basins and to such phenomena as volcanoes and earthquakes.
Present geological and geophysical knowledge of the upper portion of the earth's crust has in recent years received a decisive overall impetus mainly as a result of work carried out in the field of oil and gas exploration.
Such activities have in fact provided an enormous quantity of data on land and offshore as the result of drilling and seismic survey programs.
In particular, as a result of the highly sophisticated technologies and instruments now available, seismic reflection methods can supply more and more realistic images of the subsurface. These images are available even in very complex situations and at depths well beyond those of immediate interest to oil exploration or that are even within drilling reach.
Thus university and scientific institutions are very interested in using the geological and geophysical methods of oil exploration to investigate even more complicated and difficult questions.
Some of these are questions inherent to the structure of the earth's crust, down and beyond the depths of the crust-mantel transition, i.e., beyond the Mohorovicic discontinuity that until now has been glimpsed and postulated only in very general terms, thanks to events registered on the occasion of earthquakes.
Passive seismic methods, related to earthquakes, locate the Moho at depths that vary from 30-60 km depending on the characteristics of the crust overhead.
The world of science considers it essential to study the earth's crust in much greater detail and accuracy so as to obtain a more precise reconstruction of the entire crust.
OIL, GAS INTEREST
It is believed, especially since the advent of plate tectonics, that geodynamic phenomena are the driving force in the formation and development of mineral deposits, the existence of volcanic activity and the degree of stability in zones where the activities of man have had their greatest development.
Clearly, the oil industry is bound to take a keen practical interest in these studies in view of their direct effect on the evolution of oil fields.
It is for these reasons that in nearly all industrialized countries projects have been set up to develop new models related to the structure and evolution of the earth's crust by using reflection methods for deep exploration of the subsurface.
The U.S. launched Cocorp (Consortium for Continental Reflection Profiling) in 1974.
Cocorp was soon followed by similar initiatives in Europe, such as the British Institutions Reflections Profiling Syndicate (Birps), the French Etude Continentale et Oceanique par Reflection et Refraction Sismiques (Ecors), and the Swiss NFP-20.
CROP PROJECT
Italy felt it necessary to have its own project for the systematic study of the earth's crust of the Italian peninsula.
This was accomplished through the use of seismic reflection and all other available geological and geophysical data.
During 1985-88 within the framework of the "Strategic Project" of the Consiglio Nazionale delle Ricerche (CNR-National Research Council), seismic profiles were acquired across the Alps in cooperation with the French Ecors earth's crust project and the Swiss NFP-20 project and in the western Mediterranean with Ecors.
AGIP SpA, Italy's CNR, and the Italian National Electricity Authority ENEL, signed a 5 year agreement in 1989 to increase work on the project and develop an industrial approach to the various technological problems and financial burdens. The agreement is renewable for a further 5 years.
The technical, organizational, and financial cooperation of the three partners will make it possible to carry out the project with the latest and most up to date geological and geophysical methods that are currently in use in the oil exploration industry.
SEISMIC LINES
Within the University-CNR framework the new grid of deep seismic profiles has been redefined, and this covers the whole peninsula and the surrounding seas (Fig. 1).
The 140 km line CROP-04 across the southern Apennines (Fig. 2) and seismic profiles from the Tyrrhenian and Ionian Seas have been acquired for a total of 3,400 km.
The participants are acquiring the CROP-03 line, which cuts the northern Apennines using helicopters to cover the rough terrain.
The parameters used for all these profiles are quite different from those normally used in the surveys carried out in hydrocarbon exploration.
RESULTS
The first results from the line CROP-04 have recently been presented.
The project's sponsors have agreed that all data acquired and results obtained must not be made public until 3 years have passed.
The preliminary seismic results that are currently under examination by the interpretation groups suggest that there are good prospects of achieving the project's objectives.
This in itself can already be considered a success, given the operational and intrinsic difficulties in exploring areas that are deep in the earth and complex in structure.
Copyright 1992 Oil & Gas Journal. All Rights Reserved.
