Monte Carlo (MC) Assessment of Structurally-Controlled Shallow Offshore “Teldomi” Reservoirs, Niger Delta, Nigeria - Inferences from 3D Seismic and Wireline Log Data

Monte Carlo Simulation (MCS) was used to assess the properties of three structurally controlled reservoirs namely, Reservoir A, Reservoir B, and Reservoir C in the study area. Geologically plausible ranges specified by the mean and standard deviation values of the initial petrophysical parameters of gross pay volume (GPV), net-to-gross (NTG), porosity (POR), and hydrocarbon saturation (Sh) were estimated from six wells and 3D seismic data. The MC simulation consisted of the generation of independent random values, representing the uncertainties constrained by a random probability distribution. For each randomly simulated combination of these parameters, original-oil-in-place (OOIP) was simulated. This process was repeated ten thousand (10000) times for each parameter after which the cumulative distribution functions (CDFs) for the simulated parameters were constructed from which summary statistics, risks and uncertainties were determined at P10 (downside), P25, P50, P75 and P90 (upside). Between the downside and upside probabilities, the GPV would be more than 13000 acre feet but less than 141000 acre-feet; the NTG would be more than 0.43 but less than 0.84; the porosity could be as low as 6% but not more than 29%; the hydrocarbon saturation would be more than 36% but less than 100%. At any given percentile, Reservoir C contains more hydrocarbon than the other two reservoirs but has the highest uncertainty. The three reservoirs would have more than 16 million barrels at P10, but not more than 111.5 million barrels combined in-place oil volume at P90. The results obtained can guide optimal future development decision on the reservoirs in the study area and thus confirmed MC simulation as veritable uncertainty modelling tool. Keywords: Monte Carlo, Structural, 3D Seismic, Wireline Log, Reservoi

Characterization of the Sulfide Deposits in the Southeastern Nigeria Using VLF Method: Insights from Numerical Modeling and Field Examples

A priori geologic and geophysical information has been used to construc conceptual VLF experiments on conductively and inductively coupled overburden geological models of the lead-zinc (Pb-Zn) mineralization zone found in southeastern Nigeria.This is based on the finite element approach to (1) simulate different geologic situations of overburden occurrence, (2) examine the roles played by overburden in modifying and masking VLF responses of a buried conductor target, and (3) confirm the effectiveness of VLF method in mapping lead-zinc lodes found in sedimentary terrains.The computed theoretical model curves and field examples are expected to serve as guide for VLF anomaly pattern recognition due to overburden thickness, resistivity and width of conductor in similar terrain as the study area

An appraisal of the geologic structure beneath the ikogosi warm spring in south-western nigeria using integrated surface geophysical methods

An integrated surface geophysical investigation involving resistivity and magnetic methods was carried out in the immediate vicinity of the Ikogosi warm spring situated in south-western Nigeria with a view to delineating its subsurface geological sequence and evaluating the structural setting beneath the warmspring. Total field magnetic measurements and vertical electrical sounding (VES) data were acquired along five N-S traverses. Magnetic and VES data interpretation involved inverse modelling. The inverse magnetic models delineated fractured quartzite/faulted areas within fresh massive quartzite at varying depths and beneath all traverses. The geoelectrical sections developed from VESinterpretation results also delineated a subsurface sequence consisting of a topsoil/weathered layer, fresh quartzite, fractured/faulted quartzite and fresh quartzite bedrock. It was deduced that the fractured/faulted quartzite may have acted as conduit for the movement of warm groundwater from profound depths to the surface while the spring outlet was located on a geological interface  (lineament)

The Horizontal Loop Electromagnetic (HLEM) Response of Ifewara Transcurrent Fault,Southwestern Nigeria: A Computational Results

The need to accurately interpret geological models that approximate mineralized zones in a Basement Complex terrain necessitate the development of horizon loop electromagnetic method (HLEM) forward modeling solutions for such scenarios. The focus of the present work is on finding rapid forward modeling solutions for synthetic HLEM data as an aid in exploration for moderate to deep conductive mineral exploration targets.The main thrust is obtaining idealized HLEM models that are required for geological interpretation of the subsurface in such environment. The original HLEM equations developed by Wesley were extended to represent a horizontally stratified earth with a conductive approximated by shear zone. From these equations a computer program was written to calculate the HLEM responses for optimal conductor model with known values of coil separations (L), depth of burial (z) and angle of dip of the target.The thin conductive model was used because it is simple and suitable for different geological scenarios. The accuracy of the approximate forward solution has been confirmed for HLEM systems with various geometric ranges, frequencies and conductivities. Three models having varying overburden thickness, dip angle of target and source-receiver separation were used in the forward modeling. The effect of varying the dip angle,overburden thickness and coil separation was studied in all the three models used. The result obtained from the forward modeling showed that variation of the dip angle gave rise to changes in the amplitudes of the anomalies generated, while that of overburden and coil separation gave rise to changes in anomaly shape. Also, the geometry and position of the causative body were precisely delineated

An appraisal of the geologic structure beneath the Ikogosi warm spring in south-western Nigeria using integrated surface geophysical methods

An integrated surface geophysical investigation involving resistivity and magnetic methods was carried out in the immediate vicinity of the Ikogosi warm spring situated in south-western Nigeria with a view to delineating its subsurface geological sequence and evaluating the structural setting beneath the warmspring. Total field magnetic measurements and vertical electrical sounding (VES) data were acquired along five N-S traverses. Magnetic and VES data interpretation<br /> involved inverse modelling. The inverse magnetic models delineated fractured quartzite/faulted areas within fresh massive quartzite at varying depths and beneath all traverses. The geoelectrical sections developed from VESinterpretation results also delineated a subsurface sequence consisting of a topsoil/weathered layer, fresh quartzite, fractured/faulted quartzite and fresh quartzite bedrock. It was deduced that the fractured/faulted quartzite may have acted as conduit for the<br /> movement of warm groundwater from profound depths to the surface while the spring outlet was located on a geological interface  (lineament)