Uphole Seismic Refraction Survey for Low Velocity Layer Determination over Yom Field, South East Niger Delta

Ofomola, Merrious Oviri

doi:10.3923/jeasci.2011.231.236

Cited by 7 publications

(7 citation statements)

References 2 publications

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“…The result in this study also agrees with the findings of the survey carried out in the Yom field in the southern Niger Delta. The study shows that the velocity of the weathered layer ranged between 250 and 800 m sec −1 (Ofomola, 2011).…”

Section: Ajasmentioning

confidence: 95%

“…Three major sedimentary cycles have occurred in the Niger Delta structural basin since the early Cretaceous. The subsurface stratigraphic units associated with the cycles are, the Benin, the Agbada and the Akata formations (Ofomola, 2011;Akpoborie et al, 2011). The Benin formation is about 1800m deep and consists essentially of loose and unconsolidated sands.…”

Section: Location and Geology Of The Areamentioning

confidence: 99%

“…The shale is understood to be over pressured and under-compacted. It is rich in hydrocarbon and constitutes the source rock for hydrocarbon (Ofomola, 2011).…”

Section: Location and Geology Of The Areamentioning

confidence: 99%

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Downhole Seismic Refraction Survey of Weathered Layer Characteristics in Escravos, Nigeria

Anomohanran¹

2014

American Journal of Applied Sciences

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The problem of datum correction in seismic surveys and the failures associated with civil engineering structures with specific reference to roads and buildings has been attributed to lack of understanding of the soil structure among others. This is why this survey on downhole seismic refraction was conducted from nine borehole locations in Escravos, Nigeria to determine the weathered layer characteristics of the area. In carrying out this study, the McSeis 160MX instrument was employed in recording data obtained from a set of hydrophones arranged in a definite manner in each of the boreholes. The data were analysed graphically by using the seismic refraction interpretation techniques. Results of interpretation indicate that the velocity of the weathered layer ranged between 454 and 533 m sec −1 with an average value of 495 m sec −1. The results also revealed that the depth of the weathered layer ranged between 2.91 and 4.41 m with an average value of 3.68 m. Analysis of the results revealed that the depth and velocity of the weathered layer increased downward towards the southern part of the study area. This is an indication that the weathered layer sloped downward to the south. It is recommended that shots for seismic survey should be located at a depth of 4.41 m to eliminate the effects associated with the low velocity layer. It is also recommended that construction of heavy buildings and roads especially bridges should have their foundations laid to a depth of 4.41 m to enable the infrastructure sit on the consolidated layer.

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Section: Ajasmentioning

confidence: 95%

Section: Location and Geology Of The Areamentioning

confidence: 99%

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Downhole Seismic Refraction Survey of Weathered Layer Characteristics in Escravos, Nigeria

Anomohanran¹

2014

American Journal of Applied Sciences

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“…Three major sedimentary cycles have occurred in the Niger Delta structural basin since the early Cretaceous era. The subsurface stratigraphic units associated with the cycles are, the Benin, the Agbada and the Akata Formations (Ofomola 2011;Akpoborie et al 2011).…”

Section: Location and Geology Of The Study Areamentioning

confidence: 99%

Determination of subsurface rock properties from AVO analysis in Konga oil field of the Niger Delta, Southeastern Nigeria

Ohaegbuchu

Igboekwe

2016

Model. Earth Syst. Environ.

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Amplitude variation with offset (AVO) analysis was carried out on Konga oil field, an onshore oil field in the Niger Delta, Southeastern Nigeria. The study consisted of forward modeling from rock parameters measured from well logs and AVO analysis of events on pre-stack time migrated 3D seismic gathers. Forward modeling predicted specific AVO behaviour of anomalous reservoir sands in the field. Density, compressional and shear wave velocity logs, combined with a wavelet extracted from recorded seismic gathers were used to generate synthetic seismic gathers and Gassmann fluid substitution models. These synthetics supported key observations made of the AVO response in the field data. AVO attributes (intercept and gradient) were derived from analysis of common depth point (CDP) gathers obtained from a 3D pre-stack seismic survey. The attributes were cross-plotted to establish trends against which anomalous amplitude behaviour were identified. Reflections related to shales and brine sands exhibit a relatively small range of orientations creating a dominant ''background trend'' against which anomalous events related to hydrocarbon-saturated reservoirs show clear deviations. On the basis of crossplot analyses (reflectivity versus offset/angle and intercept versus gradient) and modeled acoustic impedance, Class 1 type AVO anomalies observed are associated with non-hydrocarbon bearing clastic rocks that are most probably brine saturated in the field. Evidence from these results show that drilling in this field in search of hydrocarbon reservoirs poses a risky venture.

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“…These approaches have been extensively discussed and applied in different basins around the world (Hampson and Russell, 1984;Zhu et al, 1992;Belfer and Landa, 1996;Lanz et al, 1998;Martí et al, 2002;Bergman et al, 2004;Yordkayhun et al, 2007;Guevara et al, 2013). The up-hole survey technique have equally been tested and applied within the Niger Delta Basin, Nigeria (Enikanselu, 2008;Igboekwe and Ohaegbuchu, 2011;Ofomola, 2011;Adeoti et al, 2013;Anomohanran, 2014). In the present study, the up-hole survey technique is applied in the assessment of the weathering layer charateristics over OPL-135 in the western part of the Niger Delta Basin, South-South, Nigeria, to better understand the near-surface characteristics and to enhance the subsequent acquisition and processing of 3 D seismic reflection data of the prospect.…”

Section: Introductionmentioning

confidence: 99%

Assessment of Weathering Layer Characteristics over OPL-135 in the Western Part of the Niger Delta Basin, South-South, Nigeria

Adizua¹,

SOFOLABO²,

Obi-Egbedi³

2021

Current Research in Geoscience

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An up-hole seismic refraction survey was carried out in OPL-135 in the Western part of the Niger Delta Basin, (SS) Nigeria. A total of thirty seven (37) up-hole locations in a (4.03.750) km grid configuration were drilled and logged over the prospect. The focal objective for the study was to assess the weathering layer characteristics over the prospect, specifically, to estimate the weathering and sub-weathering layer thicknesses and velocities, in a bid to better understand the near-surface properties and to enhance the subsequent acquisition and processing of 3 D seismic reflection data of the prospect. From the data acquired, time-depth plots for each up-hole shot point were derived, which was used to determine the velocities of the underlying layers for each point. Depth to the refractor distance were computed to determine the thickness of the weathered layers. The result obtained gave an overview of the lateral variation in the thicknesses and velocities of the near subsurface over the prospect. The thickness of the weathering layer obtained ranged from 3.1 m at up-hole point 21 and 28 to 6.8 m at up-hole point 12, with an average value of 4.7 m across the prospect. The weathering layer velocity ranged from as low as 210 m/s at up-hole point 4 to as much as 593 m/s at up-hole point 29, with an overall average value of 361 m/s. The sub-weathering layer velocities ranged from 1131 m/s at up-hole point 32 to a maximum of 1987 m/s at up-hole point 3, with an overall average of 1707 m/s across the prospect. The results from this study would aid proper planning/implementation of the 3 D seismic acquisition program for the prospet and would as well be an indispensible tool in the pre/main and post processing of the acquired seismic reflection data.

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Uphole Seismic Refraction Survey for Low Velocity Layer Determination over Yom Field, South East Niger Delta

Cited by 7 publications

References 2 publications

Downhole Seismic Refraction Survey of Weathered Layer Characteristics in Escravos, Nigeria

Downhole Seismic Refraction Survey of Weathered Layer Characteristics in Escravos, Nigeria

Determination of subsurface rock properties from AVO analysis in Konga oil field of the Niger Delta, Southeastern Nigeria

Assessment of Weathering Layer Characteristics over OPL-135 in the Western Part of the Niger Delta Basin, South-South, Nigeria

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