Near-surface structural model was geostatistically developed from a sample density of 36 Uphole/LVL survey points to determine the properties of the weathering layer geological materials. Results from the generated Isopachs and Isovels show a dominant 2-weathered layer model with 1-weathered layer model in only five locations, mainly along the escarpment. The average thickness of the weathering layer to the first refractor consolidated layer is 18.84 m with an average velocity of 1791.40 ms . Proper application of these results will prove very useful and reliable for the enhancement of optimization processes during stages of seismic data processing and serve as baseline data for future 4D seismic data acquisition for accurate mapping of the deep underlying structures for oil and gas exploration in the North-Central part of the Niger Delta.
The near-surface anisotropic properties within the SouthWestern Niger Delta were investigated to determine their impacts on geotechnical constructions. Uphole data analyses reveal a weathered layer that is thickest in the NW, E and SE with an average of 4.2 m and thinnest in the North-Central with a value of 3.8 m; a sub-weathered layer that is thickest in the NW and SW with an average of 32.1 m and thinnest in the SE with a value of 19.0 m and an underlying consolidated layer with great thickness. Vp/Vs values of 1.16265, 1.16279 and 1.16278 were computed for the layers, respectively. Similarly, Poisson's ratio of-0.9214,-0.9201 and-0.9202 were obtained for the layers respectively. Shear modulus has an average of 4.01 × 108 Nm-2 in the weathered layer, 26.0 × 108 Nm-2 in the sub-weathered layer, and 49.98 × 108 Nm-2 in the consolidated layer. Young's modulus has an average of 0.63 × 108, 4.11 × 108 and 7.98 × 108 Nm-2 in the layers, respectively. Bulk modulus has an average of 0.74 × 108 Nm-2 , 4.62 × 108 Nm-2 and 0.94 × 108 Nm-2 in the layers, respectively. The ultimate bearing capacity, qf has an average of 804.9, 2241.0 and 3349.8 kNm-2 in the layers, respectively. The allowable bearing pressure, qa of the soil has an average of 201.2, 560.2 and 837.4 kNm-2 in the layers, respectively. Core samples collected to a depth of 66 m from 12 wells revealed an admixture of sand, sandy-clay, clayey-sand and dominant clay units. These quantitative results correlate with the standard geotechnical values for clay. The large deposit of about 30 m of clay delineated in this research may act as expansive soils which portends danger for foundations of buildings located in this area and must be avoided.
The Kirchoff and Finite-Difference migrations were carried out on seismic data from the western part of the Niger Delta of Nigeria. The survey for the acquisition of the data was oriented southwest-north-east, at an angle of 45.4490 o . The KIRCH and FXMIG seismic migration programs were used to process and display the seismic sections. The sections were interpreted for diffractions, faults, and structures. It was observed that the dipping structures were incorrectly positioned downdip from the true reflection point. Prior to migration, the dipping structures were steeper and longer. For both Kirchoff and Finite-Difference migrations, there was proper imaging of the dipping structures. The structures were accurately moved updip and diffractions collapsed. The faulting pattern is a growth fault system as is generally the case in the Niger Delta basin. The reflectors became shorter, anticlines more clearly defined, and reflection events terminating at fault planes. Finite-Difference migration is preferred because it is faster, handles velocity variation and noise better, and events appearance is sufficiently distinctive for the interpreter to find traps, seals and reservoirs.
Velocity analysis was conducted in, Agbada Field, onshore Niger Delta using geostatistical tools. This provided a quantitative technique of integrating interval velocities from Checkshots and Sonic Logs for 60 wells with the two-way travel time from 3-D pre-stacked seismic image data for an identified reservoir (D5.2). Analyses by crossplots, regression plot with variogram modelling, and kriging produced results useful in improving on some of the associated limitations arising from spatial data continuity, anisotropy and azimuthal properties inherent in velocity data. Besides, error term analysis, poor correlation between primary and secondary data, and improper calibration of data from various sources result in poor depth estimate. Geostatistical velocity analysis facilitates enhanced estimation and better depth conversion. This will improve the existing structural framework necessary for the quantification of bypassed hydrocarbon and possible redevelopment of the fields in the Niger Delta, Nigeria.
Petrophysical properties were evaluated in five wells in eastern Central Swamp Depobelt, Niger Delta using well logs. Analyses by Kingdom Suite software reveal that reservoirs’ thicknesses ranged between 24.5ft in SNG in Afam 16 to 200.5ft in SNB in Obeakpu 005. Volume of shale varies within and across all the wells with values <30% of the total thicknesses. Relative permeability to water (Krw) ranges from 0.00 to >1.00 across the wells. Reservoirs SNE and SNF in Afam 16 have average Krw of 0.00 implying 100% water-free hydrocarbon production. SNC reservoir in Afam 15 and Afam 16 has average Krw >1 implying 100% water production. The relative permeability to oil (Kro) is very high in reservoirs with high hydrocarbon saturation. SNH in Korokoro 006 has average hydrocarbon saturation of 85.70% and Kro of 0.89. SNB in Obeakpu 005 has average absolute permeability of 62,086.9mD. Reservoirs SNB, SNC and SND contain no producible hydrocarbon in Afam 15 but contain producible hydrocarbon in Afam 16, Korokoro 003 and Obeakpu 005 wells. Reservoirs SNE, SNF, SNG and SNH in Afam 15, Afam 16, Korokoro 003 and Korokoro 006 contain producible hydrocarbon with the exception of SNF in Korokoro 003. Afam 15 and Afam 16 are mainly gas-producing with estimated gas-in-place ranging from 72,630.27cu.ft/acre in SNB in Afam 15 to 1,534,667.86cu.ft/acre in SNH in Afam 16 while Korokoro 003, Korokoro 006 and Obeakpu 005 are mainly oil-producing with estimated oil-in-place ranging from 47,590.26bbl/acre in SNB in Korokoro 003 and 387,754.83bbl/acre in SNB in Obeakpu 005.
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