Imaging of Hidden Structures from the North Apuseni Mts, Romania, Using Narrow-Angle Seismic Reflection Data

Ionelia Panea

doi:10.4236/ojg.2020.101003

Abstract

I present results of processing and structural interpretation of narrow-angle seismic reflection data recorded over an area of 30 × 50 km located in the southern part of the North Apuseni Mts, Romania. The investigated area is characterized by complex subsurface geology and rough topography. The seismic measurements were performed along five linear profiles, P1-P5, using an active spread of 96 geophones for each shot point; geophone spacing was 25 m. The length of each acquisition line is greater than 10 km. The signal-to-noise ratio of these data varies along the lines and its variation is considered to be an effect of rough topography, complex subsurface geology and varying surface conditions encountered during seismic data acquisition. The data processing was performed using a standard processing flow but with different processing parameters from one data set to another. I obtained five depth-converted migrated seismic sections after data processing. The accuracy of the depth values depends on that of the stacking velocities obtained from the velocity analyses performed on the filtered seismic data. Borehole information is not available, the investigated area belonging to the areas investigated for hydrocarbons. Each seismic section shows a different structural image of the subsurface and provides useful information about the tectonic and stratigraphic evolution of the investigated area. I obtained various structural images of the subsurface after the interpretation of the depth-converted migrated seismic sections, from a simple one with undeformed and inclined reflectors to a complex one with folded and faulted reflectors, especially the older ones. I interpreted intrusive bodies piercing through the overlying sediments, which are in good agreement with the results of older geophysical studies.

Highlights

Accurate information about the subsurface geological structure is obtained after the integrated interpretation of the seismic and the borehole data recorded in studies performed for hydrocarbon exploration
The investigated area is characterized by complex subsurface geology and rough topography
The signal-to-noise ratio of these data varies along the lines and its variation is considered to be an effect of rough topography, complex subsurface geology and varying surface conditions encountered during seismic data acquisition

Summary

Introduction

Accurate information about the subsurface geological structure is obtained after the integrated interpretation of the seismic and the borehole data recorded in studies performed for hydrocarbon exploration. On the Romanian territory, seismic reflection data were recorded using active spreads of 48 or 96 geophones for each shot point, the geophone spacing being 50 m or 25 m. Numerous hydrocarbon-bearing structures were identified, and exploited, in areas from the Romanian segment of the Eastern Pannonian Basin after the geological interpretation of the time seismic sections and the borehole data. A small set of seismic sections and borehole data provided by industry were used to explain the tectonic and stratigraphic evolution of the northern part of the Eastern Pannonian Basin [2]. For the Beius Basin, located in the southern part of the North Apuseni Mts, a structural contour map of the basement and an isopach map of the Neogene formations were built after the geological interpretation of the seismic sections provided by industry [3]; images with interpreted time seismic sections, the location and the distribution of the seismic lines are not shown in [3]

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