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Estimation of curie Point Depth (cPD) across the Pan African Belt in Northern cameroon from Aeromagnetic Data

Open Journal of Earthquake Research 2020年第3期9卷 217-239页

作者： Jean Daniel Ngoh Théophile Ndougsa Mbarga Kevin Mickus Yara Tarek tabod c.arles tabod Postgraduate School of Science Technology and Geosciences University of Yaoundé I Yaoundé Cameroon Department of Physics Advanced Teachers’ Training College University of Yaoundé I Yaoundé Cameroon Department of Geography Geology and Planning Missouri State University Springfıeld MO USA Exploration Department Egyptian Petroleum Research Institute Cairo Egypt Faculty of Science University of Bamenda Bambili Cameroon

The depth to the curie isothermal point (cPD) was estimated using aeromagnetic data from northern cameroon. The cPD was estimated using a two-dimensional power density spectral analysis of nineteen 30 × 30 km blocks over a series of Neoproterozoic lithologies associated with the Pan African orogeny. The results show that there are two main regions characterized by the cPD analysis: 1) Shallow depths (~6.37 - 10.09 km) which are located in several regions including the northern portions of the study area (toward the regions of Hina Marbak, Gawel and northern Moutouroua), the southeast (Kaele region), the south (Guider) and the southwest (Mayo Oulo), and 2) deeper depths (~10.68 - 13.72 km) are located in the northeast (Mindif) and southwest (southern Moutouroua, Guider and Bossoum). The shallow depths can be related to two tectonic regimes: 1) the West-central African Rift System with northeast-trending strike-slip faults emanating from the Gulf of Guinea and 2) the cameroon Volcanic Line. However, the ultimate source of these shallow regions is interpreted to be related to the cameroon Volcanic Line based on low seismic velocities imaged by recent broadband seismic studies which are concentrated along the northeast-trending strike-slip faults. An additional finding using the cPD depths, a curie isothermal temperature of 580°c and a one-dimensional heat flow model, was heat-flow values ranging from 105.68 to 227.63 mW/m2, which are above average global heat flow values and are therefore indicative of potential geothermal resources.

关键词： Magnetic Anomaly Spectral Analysis curie Point Depth Geothermal Gradi-ent Heat Flow

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The Integrated Approach to Seismic Attributes of Lithological characterization of Reservoirs: case of the F3 Block, North Sea-Dutch Sector

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Open Journal of Earthquake Research 2020年第3期9卷 273-288页

作者： Oumarou Sanda Djeddi Mabrouk tabod c. tabod Jean Marcel Jean M. Abate Essi Simon Ngos III National Institute of cartography Yaoundé Cameroon Department of Physics Faculty of Science University of Maroua Maroua Cameroon Department of Geophysics Faculty of Hydrocarbons and Chimistry M’Hamed Bougara University of Boumerdès Boumerdès Algeria Department of Physics Faculty of Science University of Yaoundé 1 Yaoundé Cameroon Department of Physics Faculty of Science University of Bamenda Bamenda Cameroon Ore Processing Laboratory Institute for Geological and Mining Research Nlongkak Yaoundé Yaoundé Cameroon Department of Exploration Faculty of Mining and Petroleum Industries University of Maroua Kaélé Cameroon

Technological development, particularly the development of signal processing, has contributed to the improvement of the quality of results in the analysis of the characteristics of hydrocarbon reservoirs. This scientific advance is especially marked by the introduction of seismic attributes in the characterization of reservoirs. This paper is aimed at evaluating the contribution of seismic attributes in the lithological characterization of hydrocarbon accumulation zones. Thus, it has been found that instantaneous attributes make it possible to highlight the different properties of reservoir rocks. Techniques for extracting three-dimensional volume attributes have been applied to a 3D seismic data volume of the F3 block in the Dutch sector of the North Sea. The purpose of using these volume attributes is to extract signal characteristics from lithofacies in hydrocarbon zones. The results provide a remarkable contribution to instantaneous seismic attributes in reservoir location, hydrocarbon detection, and reservoir lithological prediction. The instantaneous amplitude, the derivative of amplitude 1, the factor Q, the energy and the Hilbert transform are attributes which highlight the presence of hydrocarbons through the bright spots. Thus, curvature, similarity, dip, and coherence are useful in the determination of traps such as faults and anticlines. The crossing of the instantaneous amplitude and the instantaneous frequency makes it possible to analyze the lithofacies. In the same way, the analysis of the crossed diagrams between the porosity and the instantaneous amplitude made it possible to define the different layers of the reservoir.

关键词： Seismic Seismic Attributes characterization Lithology Reservoir

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Subsurface Structural Mapping Using combined Terrestrial and Grace Gravity Data of the Adamawa Plateau (North-cameroon)

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International Journal of Geosciences 2017年第7期8卷 869-887页

作者： Bouba Apollinaire Kamguia Joseph tabod c.arles tabod Yap Loudi Nouayou Robert Kande Houetchak Ludovic Oyoa Valentin Department of Physics Higher Teachers’ Training College University of Maroua Maroua Cameroon Department of Physics Faculty of Science University of Yaounde I Yaounde Cameroon National Institute of cartography Yaounde Cameroon

In order to analyze and determine the geological structures of the Adamawa plateau, the terrestrial gravity data were combined to data computed from GGM02c gravity model. The dense gravity net obtained were further introduced into qualitative and quantitative interpretations. The resulting Bouguer anomaly map obtained from combined data shows NE-SW direction which nearly coincides with the main direction of the fractures affecting the basement in the region and indicates strong gradients marking the presence of discontinuities between heavy and negative gravity anomaly. In order to conduct the quantitative interpretation of the combined gravity data, three profiles were drawn on the residual Bouguer anomaly map and therefore were interpreted using spectral analysis method and 3D density inversion. The knowledge of the depth and density of the geological structures show an uplift of dense rocks under the granite-gneiss substratum. This dense material found in the ENE-WSW direction of the Adamawa Plateau is interpreted as basaltic intrusion probably resulting from tectonic processes. According to this study, the depths of 3.83 km and 9.62 km are the new values of depths obtained for futures investigations in the Adamawa plateau.

关键词： GGM02c Adamawa Plateau Bouguer Anomaly 3D Density Model Spectral Analysis

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Gravity Model for an Anomalous Body Located in the NW Portion of the Douala Sedimentary Sub-Basin, cameroon (central Africa)

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Open Journal of Geology 2014年第10期4卷 524-541页

作者： Eric N. Ndikum c.arles T. tabod Bernard Z. Essimbi Fidèle Koumetio Noutchogwe c. Tatchum Department of Physics University of Yaoundé 1 Yaoundé Cameroon Department of Fundamental Sciences Higher Technical Teacher Training College (HTTTC) Bambili The University of Bamenda Bamenda Cameroon Department of Physics Faculty of Science The University of Bamenda Bamenda Cameroon Department of Physics Faculty of Science University of Dschang Dschang Cameroon Department of Physics Higher Teacher Training College (HTTC) Bambili The University of Bamenda Bamenda Cameroon

Gravity studies have been carried out in the Douala sub-basin which is a sedimentary basin located both onshore and offshore on the South coast of cameroon between latitudes 3°03'N and 4°06'N and longitudes 9°00' and 10°00'E, covering a total surface area of 12,805 km2. On its onshore portion, the Douala sub-basin has a trapezoic shape and covers a total surface area of about 6955 km2 while the offshore part covers an area of about 5850 km2. Gravity data used in this study are constituted of 912 gravity data points located between longitudes 8°10.2' to 10°59.4'E and latitudes 2°30.6' to 4°59.4'N and the study area is located to the NW section of the onshore portion of the Douala sub-basin. This study area is characterised by considerably high positive anomalies attaining peak values of about 104.1 mGals at longitude 9°9.9' and latitude 4°1.1' with contour lines which are mostly oriented in the NNE direction. Residual anomalies were extracted by upward continuation of the Bouguer anomaly field at an optimum height of 30 km. This residual field and those obtained by the separation of polynomial of order 4 had a very high correlation coefficient factor of 0.979. The multi-scale horizontal derivative of the vertical derivative (MSHDVD) method was applied on the extracted residual anomalies for the delimitation of possible contacts in the source while the amplitude spectrum was used to estimate the depth to the top of the potential field source. The MSHDVD method did not delimite any clear cut contacts in the source but the amplitude spectrum estimated the potential field source at a depth of about 4.8 km. The ideal body theory was used to determine the density contrast along a 65 km NW-SE profile yielding a value of 0.266 g/cm3. 2.5D modelling aimed at bringing out the underlying structural layout of this study area presents a source body which is very probably an intrusive igneous block surrounded by sedimentary formations and having a density of 2.77 g/cm3 at a depth

关键词： Douala Sub-Basin Sedimentary Basin Bouguer Anomaly Residual Field Upward continuation 2.5D Model Intrusive Igneous Block

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Evidence of Some Major Structures Underlying the Douala Sedimentary Sub-Basin: West African coastal Basin

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Journal of Geoscience and Environment Protection 2017年第7期5卷 161-172页

作者： Eric N. Ndikum c.arles T. tabod F. Koumetio Noutchogwe c. Tatchum Kenfack J. Victor Department of Physics University of Yaoundé I Yaoundé Cameroon Department of Fundamental Sciences Higher Technical Teacher Training College (HTTTC) Bambili The University of Bamenda Bamenda Cameroon Department of Physics Faculty of Science The University of Bamenda Bamenda Cameroon Department of Physics Faculty of Science University of Dschang Dschang Cameroon Department of Physics HTTC Bambili The University of Bamenda Bamenda Cameroon Department of Earth Science Faculty of Science University of Dschang Dschang Cameroon

Gravity data have been processed in the Douala sedimentary sub-basin in a section consisting of a set of 116 gravity data points located between latitudes 3°03'N and 4°06'N and longitudes 9°00'E and 10°00'E. The established Bouguer anomaly fields and the Residual anomaly fields, extracted by upward continuation at an optimum height of 30 km, were both characterized by considerably high positive anomalies. These anomalies showed many ring-like positive gravity anomaly contour lines in the study region. Gravity gradients were analysed using the multi-scale horizontal derivative of the vertical derivative (MSHDVD) method, and this excluded the existence of fault lines across this region. Amplitude spectrum was used to estimate the potential field source at a depth of about 4.8 km. The ideal body theory capable of handling sparse data contaminated with noise was applied along a 50.2 km WWS-EEN profile to determine a density contrast of 0.266 g/cm3. Using these results as constraints, 2.5 D modelling carried out along this profile presented two major blocks with density contrast of 0.266 g/cm3. The first block is probably an intrusive igneous body with a density of about 2.77 g/cm3 , having an average thickness of about 26 km with its top and base lying at depths of about 4.25 km and 30.25 km respectively. The second block is likely a pillar of igneous material, located at a depth of about 10.77 km with a density of about 2.77 g/cm3 whose base goes deep down beyond the crust-mantle boundary. These results support previous findings that there are similarities between the Douala sedimentary sub-basin and the coastal sedimentary basin of Mauritania-Senegal and thus foster the suggestions of a more extensive movement that would have affected the whole of the West African coast.

关键词： Douala Sedimentary Sub-Basin Bouguer Anomaly Residual Field 2.5D Model Igneous Block

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Structure of the crust Beneath the South Western cameroon, from Gravity Data Analysis

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International Journal of Geosciences 2016年第8期7卷 991-1008页

作者： Marcel Jean E. J. M. Abate P. Njandjock Nouck H. E. Ngatchou V. Oyoa c. T. tabod E. Manguelle-Dicoum Department of Physics Faculty of Science University of Yaounde I Yaounde Cameroon National Institute of cartography Ministry of Scientific Research and Innovation Yaounde Cameroon Geological and Mining Research Institute Ministry of Scientific Research and Innovation Yaounde Cameroon Department of Earth Science Faculty of Science University of Yaounde I Yaounde Cameroon Department of Physics Advance Teacher’s Training College University of Maroua Maroua Cameroon Department of Physics Faculty of Science University of Bamenda Bambili Cameroon

The study area is located in the south western cameroon and includes part of the cameroon Volcanic Line (cVL). Volcanic activity has been recorded in this area, precisely on the Mount cameroon which recently erupted in 2002. In addition, deadly carbonic gas was emitted by crater lakes (Monoun and Nyos) in 1984 and 1986 respectively. Potential field model EGM2008 has been used to investigate the structure of the crust. A regional/residual separation is performed using upward continuation and polynomial separation methods. The results from this operation show a similarity between the regional anomalies resulting from both methods. The regional anomaly maps present an increasing gradient trending ENE-WSW above and below latitude 5?N. Moreover, six nearly parallel profiles were drawn on the cVL in addition to two other profiles at the northern edge of congo craton. These profiles were used to estimate the depths of the Moho discontinuity and some shallow sources by the means of the Bouguer and the residual anomalies respectively. The results show that the Moho discontinuity depths vary from 19 - 25 km (under Mount cameroon) to 28 - 34 km (in Kumbo), while the southern neighbouring zone presents a Moho discontinuity depth ranging between 23 - 31 km (in Ngambe) and 22 - 32 km (in Eseka). These findings agree with the previous seismic and gravity researches lead in the area. EGM2008 is therefore a reliable tool to investigate the subsurface structures.

关键词： South Western cameroon EGM2008 Bouguer Anomaly Spectral Analysis Moho Discontinuity

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