Results of Some Non-seismic Exploration Methods in Different Gaso-Petroleum Regions of Western and Central Cuba

Abstract

It is well documented that most hydrocarbon accumulations have escapes or microseepage that are predominantly vertical, as well as that they can be detected and mapped using various non-conventional and non-seismic exploration methods . The surface expression of hydrocarbon microseepage can take a variety of forms, which determine the development of several detection methods, both direct (hydrocarbon gas geochemistry) and indirect (Redox Complex) , as well as non-seismic geophysical methods (gravimetry , magnetics, electrics, and airborne gamma spectrometry), morphometry, and remote sensing . Benefits in the use of non-seismic and non-conventional exploration methods , integrated with geological data and seismic, result in a better evaluation of prospects and exploration risk . The source materials are as follows: the gravimetric (Bouguer reduction 2.3 t/m³) and aeromagnetic (reduced to pole) maps at a scale of 1:50,000; airborne gamma-spectrometric maps (channels K, Th and U (Ra)) at a scale 1:100,000; the Digital Elevation Model (90 × 90 m) and; digital maps of hydrocarbon shows and oil wells of the Republic of Cuba at a scale of 1:250,000. The processing consisted in the regional-residual separation of the gravimetric and morphometric fields, the calculation of the first vertical derivative of the gravimetric and aeromagnetic fields and of the K/Th ratio. A mapping of sectors of oil–gas interest in western and central Cuba related to the conventional oil of the Placetas Tectonic-Stratigraphic Unit and the Jurassic level is based on the presence of a complex of indicator anomalies. It considers the following attributes: subtle local gravimetric maximums (in or near regional minimums); minimum of the K/Th ratio and local maximums of U (Ra) at its periphery, and; local maximums of residual relief.