Near-Surface Seismic Velocity Data: A Computer Program For Analysis

A computer program (NESURVELANA) has been developed in Visual Basic Computer programming language to carry out a near surface velocity analysis. The method of analysis used includes: Algorithms design and Visual Basic codes generation for plotting arrival time (ms) against geophone depth (m) employing the Least-Squares approximation to fit the best lines, computing velocities from the reciprocals of the slopes of the lines and determining thickness for multi-layer cases. The program was debugged and test-run on Microsoft Windows XP using a set of two near-surface seismic velocity data acquired by the Up-hole technique within the South-Central Niger Delta, Nigeria. The first set of data showed a weathered two-layer case, where the layer has a thickness of 6.0 m and velocity of 431 m/s and a consolidated layer velocity of 1845 m/s. The second set of data was a weathered three-layer case, where the thicknesses were 4.3 m and 7.7 m with the weathered and second layer with velocities of 513 m/s and 1132 m/s respectively and a consolidated layer velocity of 1756 m/s for the third layer. These results are comparable with those obtained by other researchers for the Niger Delta, Nigeria. The resulting information from this near-surface velocity analysis is essential for static corrections for the accurate mapping of the underlying structures for oil and gas exploration, and geotechnical engineering for foundation works in building houses, bridges, dams and construction of highways. Keywords: Algorithm design, visual basic codes, least-squares approximation,weathered layer thickness and velocity. Nigerian Journal of Physics Vol. 19 (2) 2007: pp. 253-26

Elements in the process of discovery

No Abstract. Global Journal of Humanities Vol. 6 (1&2) 2007: pp. 41-4

Estimation of Thermal Conductivity in the North-western Niger Delta Sedimentary Basin, Nigeria, Using Geophysical Well Logs

Thermal conductivity estimates are computed from nineteen petroleum wells in the northwestern Niger Delta, Nigeria, using a geometric mean model. Sonic and gamma-ray logs were digitised and used in the estimation of in situ conductivity. The Niger Delta is composed of three major diachronous lithostratigraphic units of shaly Akata, shaly-sandstone Agbada and sandy Benin formations, which form the bulk of the deltaic sediments. All the wells used in the study could only penetrate the top-most Benin and the underlying Agbada formations, except Akata that is the last deeply lying formation. Mineralogy, porosity and lithology exert the most important control on the matrix thermal conductivity in the Niger Delta sedimentary basin. There is a decrease of thermal conductivity with increasing shale fraction. The bulk conductivity also show an increase with increasing sandstone fraction. Increase in porosity results in a decrease in bulk conductivity. Thermal conductivity values and variations for a given lithologic unit are reduced at increased porosity, such that thermal conductivity of the top-most continental Benin sand-stone formation vary between 2.39W/m°C and 2.74W/m°C with an average of 2.52W/m°C. Thermal conductivity for the underlying, marine shaly-sandstone Agbada formation varies between 2.16W/ m°C and 2.69W/m°C with an average of 2.33W/m°C. Keywords: Thermal conductivity, porosity, lithology, well logs, geometric mean model, Niger Delta Basin, NigeriaDiscovery and Innovation Vol. 19 (4) 2007: pp. 269-27