Earth Science Malaysia (ESMY)

Reduction to the pole (RTP) is a magnetic anomaly data processing filter to remove the influence of the magnetic inclination angle. This filter is needed because of the magnetic dipole nature which complicates the interpretation process. The research aims to explore andesite rocks through the application of RTP to the local magnetic anomalies data in Kutasari District, Purbalingga Regency, Indonesia. The research procedures include data acquisition, processing, modeling, and interpretation. The 2D-modeling results on the local magnetic anomalies data have produced three layers of rock. Layer with a susceptibility value of 0.00291 cgs is interpreted as vesicular andesitic rocks, layer with a susceptibility value of 0.02307 cgs is interpreted as massive andesitic rocks, meanwhile layer with a susceptibility value of 0.00721 cgs is interpreted as undifferentiated volcanic rocks. The results showed that the west to northwest part of the study area is the most prospective area containing andesite rocks.

Structural interpretation and characterization of Assa-field in Northern Niger Delta was done to map the primary structures responsible for hydrocarbon entrapment and closures that are favorable for the accumulation of hydrocarbon as well as to indicate areas for hydrocarbon exploration in the field. The method used for this research involved delineation of lithology, identification of reservoir, interpretation of horizon and fault to generate structural maps of the subsurface. Depth and time structure maps were generated to show more detailed structure of the field. Three major horizons (sand 1, sand 2, and sand 3) were mapped based on uniqueness and clarity of their features. Major faults were delineated from the 3-D seismic section. The appearance of these faults in the field is a sign of possible hydrocarbon accumulation. The knowledge from the results of this study can be applied in exploration and production to identify hydrocarbon trapping potential of a field and volumetric evaluation of fluid in a field.

3D Lithology and reservoir fluid studies based on conventional interpretation approach, such as low Vp/Vs values indicating gas presence have been used to discriminate hydrocarbon fluids. This work was provoked by the emerging trends of noticeable uncertainties leading to drilling of dry wells in the study area. Confirming the physical indicators of hydrocarbon in the reservoirs through the employed method is worthwhile. Well log data of M oil field was investigated with the aim of identifying reservoir rocks through qualitative and quantitative interpretations of subsurface well log data of M oil field through rock properties cros-splots analysis in the select reservoir in the field (M-5000) and to derive elastic rock attributes such as Lame’s parameter terms (λρ and μρ), Vp/Vs, P-Impedance and S-Impedance from available petrophysical data. Rock attributes derived from well logs were combined to produce three major forms of crossplots, which described and characterized the reservoir in terms of fluid and lithology present. The combinations were: VP/VS versus IP, μρ against λρ and IP versus IS. These rock parameters were analyzed in cross-plots space and used to determine which of them constitutes better indicators of pore fluids and lithology. The M- oil field cross-plot analysis indicate the lowest values of VP/VS (2.05-2.40); IP (5600-6300 (m/s*(g/cc)), λρ (16-20 (GPa*g/cc)), and μρ (4-9.5 (GPa*g/cc)). However, the low values of VP/VS, IP, λρ, and μρ, perhaps IS corresponds to hydrocarbon (Gas) saturation within the M- oil field.

On sheet 134 of the aeromagnetic map of Nigeria is a prominent northeast (NE) trending negative anomaly that extends for >20 km. This work reinterprets the anomaly using oasis montage™ 7.0 software, by inverse geological modelling of magnetic profiles. The aim of this work is to identify the Chibok magnetic anomaly as a plate tectonic feature, and as part of the West African Rift System. Three profiles were modelled across the residual magnetic anomaly, which yielded a depth range of 1 to 2 km. The result furnished a subsurface picture of ‘horst and graben’ which are characteristic of rifts. The sedimentary infill of the interpreted rift is considered to be sands/or sandstone due to the low magnetic anomaly. Sandstone has very low magnetic susceptibility [30 x106 emu (S.I.)] compared to granite and basalt. Geological data showed NW, NE, N-S, and E-W structural trends on the granitic basement. These manifest as faults, shear zones, joints and foliations. Emplacement of the Tertiary basalt in the NW of the area of study area showed planes of crustal weakness in the Precambrian basement. A palinspatic map of the area identified the pre-Tertiary geology. The sediment infill of the interpreted rift may serve as very rich aquifer for groundwater abstraction for irrigation in this semi-arid zone. The evidence of the plate tectonic nature of the interpreted rift indicated its alignment with offshore transform faults like Chain and Charcot as well as the Cameroun Volcanic Line.

A 3 Axis MCL6 Magnetometer was used to gather the magnetic data. The information was gathered from a 1 km by 500 m area along eight profile lines with a length of roughly 1000 m each. Each profile is spaced roughly 250m apart from the other. The magnetic investigation was created in a way that provided clear definition of the depth to phenomena in the region. Measurements of the magnetic strengths at discrete spots along traverses spaced consistently throughout the area of interest were required by the data collecting approach in order to sufficiently cover the segment utilized to ascertain the structure and deformation analysis of the study area. The geological conditions in the shallow subsurface provide the highest frequency events of interest, whereas magnetic property contrasts at or beneath the basement surface produce the lowest frequency occurrences. Significant lateral variations and contrasts in the shallow formations’ magnetic characteristics are produced either singly or as a result of a particular combination of faulting, deposition, and mineralization linked to displacement and deformation of the structural system.

In recent decades, urban sprawl has been viewed as one of the most pressing issues that cities over all the world in developing countries are batting with. It is often associated mostly with rural-urban migration and rising birth rates, where development is given precedence over urban planning. The study focuses on the urban sprawl of the greater Port Harcourt city. The greater Port Harcourt city is expanding at an unprecedented rate, with no adequate planning or statistical record. The study intends to address this issue by building models using remote sensing and geographic information system (GIS) tools in order to analyze urban sprawl in the Greater Port Harcourt city. To achieve this set of objectives, three sets of Landsat sensors, which were captured at different time intervals (1986, 2006, and 2021), were used to monitor urban sprawl in the study area. The Geographic Positioning System (GPS) was used during the field visit to collect the ground control points of some locations within the city. The National Population Commission (NPC) data was also employed to acquire the demographic statistics. The result of the study shows that the built-up area had expanded from 47.35 km2 (10.76%) in 1986 to 71.05 km2 (16.14%) in 2000 and to 284.68 km2 (64.68%) in 2021. This expansion in built-up area generates a decline in wetland, bare land, and forest land from 112.296 km2 (25.51%), 61.369 km2 (13.94%), and 160.152 km2 (36.39%) in 1986 to 72.468 km2 (16.47%), 86.486 km2 (19.65%), and 136.853 km2 (31.09%) in 2000, and to 42.810 km2 (9.73%), 10.858 km2 (13.94%), and 40.8384 km2 (9.28%) in 2021. The findings of the study are important because they give the government information on how quickly the study area is expanding, allowing it to adopt an appropriate planning strategy. In conclusion, the study demonstrate that remote sensing and GIS techniques can be utilized to successfully monitor the environment on a regular basis in order to investigate urban sprawl and inform better decision-making.

The hazards of being over-exposed to ionizing radiation at various mining sites are of great concern to environmental scientists. This study aims to measure the activity concentrations of 40K, 238U, and 232Th radionuclides at various mining sites of Paago, Iseyin local Government, Oyo state, Southwestern Nigeria using a well calibrated HPGe detector. Twenty (20) soil samples were obtained, analyzed, and compared with the WHO recommended standard. The results obtained indicate that 40K, 238U, and 232Th values ranging from 58.40 to 950.41Bqkg-1, 5.57 to 24.22Bqkg-1, and 4.1 to 25.93Bqkg-1. The gamma absorbed dose rate in the soil samples ranged from 6.85nGyh-1 to 45.73nGyh-1, with mean absorbed dose rate lower than the WHO recommended average value of 59nGh-1. The annual effective dose rates in the air varied from 14.26 to 19.74μ Svyr-1 with an average value of 17.99 μSvy-1, while the highest and lowest values of radium equivalent in the soil were 113.68Bqkg-1 and 21.62Bqkg-1. These findings shows that the external and internal hazard indices obtained were less than unity and the means activity concentration of the three radionuclides was lower than the world average recommended value indicating that the study areas pose no significant radiological threat to the populaces, and the crops are safe for consumption.

This study investigated the effect of channel planforms changes on potential river flooding in Kaduna state (River Kaduna as case study); with the aim to ascertain the effects of river channel planform on its potential flooding and put measures in place to advert the environmental menace. Topographic maps covering the entire course of the river and the characteristics of the river to be studied were obtained from the federal ministry of survey. The reliability of satellite images was verified by ground measurements using a 30m Surveyor’s tape on four bridges that cross River Kaduna. The measurements obtained were compared with correspondent measurements on the satellite image and found that the ground measurements and the measurements on both SPOT and Sentinel images were close. Three reaches (Meander 1, 2, 3; Straight reach 1, 2, 3 and Braided reach 1, 2, 3) were selected for this study. Variations measured along the river were changes in channel width, changes in sinuosity index, changes in braiding index channel lateral migration and changes in channel length from 1962 to 2017. The results showed a reduction in the channels width in all the reaches from average of 190m in 1962 to 74m in 2017; the sinuosity index was low in the duration considered (average of 1,15) while the braiding index value had a mean of 0.55. Channel migration also reduced from an average of 82m in 1962 to 53m in 2017 while the river reduced by 12% within this same period. The propensity of river flooding in the study area is high hence there is the need to carry out channel improvement, early warning system and desiltation of the river in order to eliminate the potential danger.

The sulphide ore mineralization occurrence in the area is structurally controlled. However, wrong structural delineation has led to some recorded mine failures and revenue loss faced by investors and government. Therefore, subsurface structural mapping is crucial for the successful and reliable delineation of sulphide ore enrichment zone within the area. To this effect ground magnetic method was used to appraise the structural elements associated with the sulphide mineralization in Ikenyi Izzi area, part of Southern Benue Trough. The total magnetic field intensity (TMI) was recorded, corrected, and separated into regional and residual magnetic fields. The TMI varies from 33259.7–33329.7nT with an average field value of 33299.4nT. Whereas residual susceptibility value ranges from -36.3–25.7nT with significant magnetic closures which correspond to the areas of low and high susceptibility values. Three dominant structural geometries was identified in the area; NE-SW>NW-SE>N-S with few E-W structures. The NE-SW and some N-S structures characterized areas of high magnetic anomaly closures and are associated with the regional trends of the igneous intrusive rocks, whereas NW-SE structures host the ore deposit (Trending ≥N300°) and dominantly associated with areas of low magnetic anomaly zones. The cross-cutting relationship of the NE-SW, N-S and NW-SE structures infers a close association of the intrusions and mineralization, which was validated by ground truthing. The residual susceptibility values of 1 to 10nT and ≥ 10nT were inferred as shale and intrusive rocks respectively. The implication of this study denotes that missing appropriate structural elements delineation could lead to abortive mines target.

The study aimed at predicting the porosity of reservoir sands in ‘Arike field’ Niger Delta, Nigeria by converting seismic trace of the interval of interest in the seismic survey into a porosity log to generate a porosity volume. Optimal number of relevant attributes were selected using multi-attribute analysis. The study discovered that three attributes (energy, velocity fan, and Q factor) were efficient. These attributes were then utilized to train a supervised neural network to establish the relationship between seismic response and porosity. The Opendtect software used, extracted all specified input attributes and target values over the specified range along the well tracks and randomly divided the data into a training and test set attribute. The study established the integration and correlation of energy attribute, velocity fan attribute, and Q factor as relevant seismic attributes for porosity estimation when little or no well log is available, hence giving a means of spatially extending well data.