Własności petrofizyczne osadów kambru i eokambru wyniesienia Łeby

Andrzej Miesztalski




The attempt to characterize the petrophysical properties of the Cambrian and Eocambrian deposits in the area of the Łeba elevation (Fig. 3) has been made in this work. The existing results of the standard laboratory researches have been applied when having a particular aim in: effective and complete porosity measurements, permeability measurements, specific gravity and bulk density measurements, the results of geochemical and geophysical studies (gamma and neutron-gamma profiling). A great number of measurements such as the observations of petrophysical thin-sections and the measurements of the geometry of porous space have been made additionally when applying the method of mercury porosimeter. Taking into account the above mentioned procedures one might easily notice that the pores of subcapillar-type (having conventional diameters below 0.5 microns) (Fig. 2, 3) play an important role as far as the size of effective porosity referred to the Cambrian and Eocambrian deposits is concerned. The effective porosity related to these formations consists of microinterstices and intragranular spaces. Genetically their origin must be connected with the period of intensive consolidation of the deposit in which for the recrystalization processes the organic substance migration was considerably limited. When analyzing the Cambrian deposits one may easily notice the close correlation between the sizes of rock permeability and its effective porosity (Fig. 4).
On the contrary to the Cambrian deposits this correlation in the Eocambrian deposits (Fig. 5) is unsignificantly noticed (it can be as well the result of insufficient supply with data). About four horizons featuring the higher values of effective porosity and permeability (Fig. 6) can be shown in the profiles of the Cambrian and Eocambrian formations situated in the area of the Łeba elevation. Nearly all more important symptoms of bitumens occurrence are closely connected with those horizons. The differentiation of these parameters is more evident not only in the vertical position but also in the horizontal position. Within the isolated petrophysical horizons the effective porosity and permeability are said to be higher in the zone of the elevated block of Żarnowiec. Such an explanation or a regularity may be overwhemingly referred to the whole region of the Łeba elevation and can be of a paramount importance effecting the directions of further prospecting in that region. When sumerizing all above mentioned facts one might seem that the occurrence of bitumens within the discussed area is mostly connected with the distribution of values of the examined physical parameters and therefore with the hypsometric position related to the Cambrian and Eocambrian deposits.


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