scholarly journals Interpretation of High Resolution Aeromagnetic Data for Hydrocarbon Exploration in Bornu Basin, Northeastern, Nigeria

2020 ◽  
Vol 63 (2) ◽  
Author(s):  
Adesoji Akanji ◽  
Oluseun Sanuade ◽  
Olawale Osinowo ◽  
Onyeka Okafor
Keyword(s):  
High Resolution ◽  
Hydrocarbon Exploration ◽  
Aeromagnetic Data

scholarly journals Analytic Signal Depth from High Resolution Aeromagnetic Data over the Gongola Basin Upper Benue Trough Northeastern Nigeria

2021 ◽  
Vol 25 (4) ◽  
pp. 585-590
Author(s):  
H. Musa ◽  
N.E. Bassey ◽  
R. Bello
Keyword(s):  
High Resolution ◽  
Magnetic Structure ◽  
Horizontal Cylinder ◽  
Analytic Signal ◽  
Aeromagnetic Data ◽  
Polynomial Fitting ◽  
Benue Trough ◽  
Local Maxima ◽  
Depth Determination ◽  
Programming Software

The study of high-resolution aeromagnetic data was carried out over the Gongola basin, upper Benue trough, northeastern Nigeria, for analytic signal depth determination. Total intensity magnetic map obtained from the data using the Oasis Montaj TM programming software was used to get the residual map by polynomial fitting, from where the analytic signal was obtained with the use of anomaly width at half the amplitude (X1/2). This was used to carry out depth estimations over the study area. The results showed that it peaks over the magnetic structure with local maxima over its edges (boundaries or contact), and the amplitude is simply related to magnetization, likewise results also showed that the depth estimates were in the range of 1.2 to 5.9 km and were calculated for contact, dyke/sill and horizontal cylinder respectively. The lowest values are from DD profiles, while the highs are from AA profiles. This work is important in identifying dykes, contacts and intrusives over an area.

Reflection seismic imaging of buried shallow salt structures – examples from ongoing case studies in Northern Germany

2021 ◽  
Author(s):  
Ulrich Polom ◽  
Rebekka Mecking ◽  
Phillip Leineweber ◽  
Andreas Omlin
Keyword(s):  
High Resolution ◽  
Water Resources ◽  
Industrial Development ◽  
Geophysical Methods ◽  
Hydrocarbon Exploration ◽  
P Wave ◽  
Depth Range ◽  
Reflection Seismic ◽  
Wide Range ◽  
Cap Rock

<p>In the North German Basin salt tectonics generated a wide range of evaporite structures since the Upper Triassic, resulting in e.g. extended salt walls, salt diapirs, and salt pillows in the depth range up to 8 km. Due to their trap and seal properties these structures were in the focus of hydrocarbon exploration over many decades, leading to an excellent mapping of their geometries below 300 m in depth. During salt rise Rotliegend formations were partly involved as a constituent. Some structures penetrated the salt table, some also the former surface. Dissolution (subrosion) and erosion of the salt cap rock by meteoric water took place, combined with several glacial and intraglacial overprints. Finally the salt structures were covered by pleistocene and holocene sediments. This situation partly resulted in proneness for ongoing karstification of the salt cap rock, leading to e.g. local subsidence and sinkhole occurrence at the surface. The geometry, structure and internal lithology of these shallow salt cap rocks are widely unknown. Expanding urban and industrial development, water resources management and increasing climate change effects enhance the demands for shallow mapping and characterization of these structures regarding save building grounds and sustainable water resources.</p><p>Results of shallow drilling investigations of the salt cap rock and the overburden show unexpectedly heterogenous subsurface conditions, yielding to limited success towards mapping and characterization. Thus, shallow high-resolution geophysical methods are in demand to close the gaps with preferred focus of applicability in urban and industrial environments. Method evaluations starting in 2010 geared towards shallow high-resolution reflection seismic to meet the requirements of both depth penetration and structure resolution. Since 2017 a combination of S-wave and P-wave seismic methods including depth calibrations by Vertical Seismic Profiling (VSP) enabled 2.5D subsurface imaging starting few meters below the surface up to several hundred meters depth in 0.5-5 m resolution range, respectively. The resulting profiles image strong variations along the boundaries and on top of the salt cap rock. Beside improved mapping capabilities, aim of research is the development of characteristic data features to differentiate save and non-save areas.</p>

Depth to magnetic basement in the Anambra Basin, Benue Trough of Nigeria from aeromagnetic data: A prelude for hydrocarbon exploration

2021 ◽  
pp. 1-57
Author(s):  
Olatunbosun O. Olagundoye ◽  
Chiedu S. Okereke ◽  
Aniekan E. Edet ◽  
Dominic Obi ◽  
Aniediobong Ukpong
Keyword(s):  
Depth Estimation ◽  
Data Transformation ◽  
Hydrocarbon Exploration ◽  
Hydrocarbon Generation ◽  
Depth Range ◽  
Aeromagnetic Data ◽  
Benue Trough ◽  
Anambra Basin ◽  
Magnetic Basement ◽  
Fault Structures

Data transformation, regional-residual separation, trend analysis, and Analytic Signal (AS) depth estimation were applied to aeromagnetic data covering the Anambra Basin, which is a major depocentre in the Benue Trough, southeast Nigeria with the primary objectives of accentuating attributes of magnetic sources and determining if sufficient sediment thickness exists for hydrocarbon generation, maturation, and expulsion. The application of data transformation techniques (such as map projection, merging, and reduction-to-pole) and regional-residual ensured the computation of a crustal magnetic field that would be suitable for magnetic analyses. Results indicate that the magnetic basement in the basin forms an undulating surface overlain by sediments with average thickness ranging between 4 km and 7.5 km, while maximum thickness reaches 8 km in some areas. This depth range suggests promising prospect for source-facies maturation and expulsion. We expect that areas in the study area with these appreciable sediment thicknesses, good preservation of graben-fill, and suitable areal closures or fault structures would be favorable for hydrocarbon prospectivity.

THE INTERPRETATION OF AEROMAGNETIC SURVEYS FOR HYDROCARBON EXPLORATION

1999 ◽  
Vol 39 (1) ◽  
pp. 494
Author(s):  
I. Kivior ◽  
D. Boyd
Keyword(s):  
Spectral Analysis ◽  
Sedimentary Basins ◽  
Hydrocarbon Exploration ◽  
Petroleum Exploration ◽  
Magnetic Data ◽  
Curve Matching ◽  
Aeromagnetic Data ◽  
Profile Data ◽  
Aeromagnetic Survey ◽  
New Approach

Aeromagnetic surveys have been generally regarded in petroleum exploration as a reconnaissance tool for major structures. They were used commonly in the early stages of exploration to delineate the shape and depth of the sedimentary basin by detecting the strong magnetic contrast between the sediments and the underlying metamorphic basement. Recent developments in the application of computer technology to the study of the earth's magnetic field have significantly extended the scope of aeromagnetic surveys as a tool in the exploration for hydrocarbons. In this paper the two principal methods used in the analysis and interpretation of aeromagnetic data over sedimentary basins are: 1) energy spectral analysis applied to gridded data; and, 2) automatic curve matching applied to profile data. It is important to establish the magnetic character of sedimentary and basement rocks, and to determine the regional magnetic character of the area by applying energy spectral analysis. Application of automatic curve matching to profile data can provide results from the sedimentary section and deeper parts of a basin. High quality magnetic data from an experimental aeromagnetic survey flown over part of the Eromanga/Cooper Basin has recently been interpreted using this new approach. From this survey it is possible to detect major structures such as highs and troughs in the weakly magnetic basement, as well as pick out faults, and magnetic layers in the sedimentary section. The results are consistent with interpretation from seismic and demonstrate that aeromagnetic data can be used to assist seismic interpretation, for example to interpolate between widely spaced seismic lines and sometimes to locate structures which can not be detected from seismic surveys. This new approach to the interpretation of aeromagnetic data can provide a complementary tool for hydrocarbon exploration, which is ideal for logistically difficult terrain and environmentally sensitive areas.

AN AUTOMATIC METHOD OF COMPILATION AND MAPPING OF HIGH‐RESOLUTION AEROMAGNETIC DATA

Geophysics ◽  
1971 ◽  
Vol 36 (4) ◽  
pp. 695-716 ◽  
Author(s):  
B. K. Bhattacharyya
Keyword(s):  
High Resolution ◽  
Magnetic Measurements ◽  
High Sensitivity ◽  
Positional Error ◽  
Automatic Method ◽  
Aeromagnetic Data ◽  
Aeromagnetic Survey ◽  
Machine Method ◽  
Flux Gate ◽  
Definition Of

An automatic method has been developed for compilation of digital aeromagnetic data. This method has been applied to the data obtained during a high‐sensitivity aeromagnetic survey over an area in the Precambrian shield of northeastern Ontario in Canada. With this method, all points of intersection between traverse and base lines are determined automatically and adjusted within the limits of positional error for minimizing differences in magnetic values at the intersections. Then the data are corrected for diurnal variation and leveled to tie the magnetic measurements together. Next, the resulting total field values are contoured with a machine method at a scale of 1:25,000. For such a scale, the minimum contour interval that can be used in the present area is two gammas. However, because of the accuracy of the method of compilation, with a larger scale, it is possible to trace one‐gamma contours. The maps thus compiled have been compared with published aeromagnetic maps of data obtained with conventional flux‐gate and proton‐precession magnetometers. The new maps are vastly superior to the old ones for delineating trends, patterns, and fine features of available detailed geological maps. This superiority is mainly due to the excellent definition of small amplitude anomalies, some of only a few gammas in magnitude, on the high‐resolution magnetic maps.

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