The relationships between density and velocity are important in many geological analyses that involve rock property parameters. However, the accuracy of the results is often limited when there is a verbatim application of generalized rock property relationships. Many studies in the Niger Delta Basin suffer from this limitation. As a way forward, well logs in the Niger Delta were used to derive lithology-specific coefficients that can be applied in density-velocity transforms that make use of the Gardner equation. Whereas the default coefficient (a) and exponent (b) in the original Gardner equation are 0.31 and 0.25, respectively, fitting the Gardner curve to local data results in a coefficient value of 0.33 and 0.29 for shales and sands, respectively, when the exponent is kept at the default value. Comparing measured density data with estimates obtained from sonic velocities using the original Gardner equation gives a regional mean absolute deviation of 0.13 g/cc while those of the newly derived local coefficients do not exceed 0.05 g/cc giving an improvement of over 60% in the accuracy of estimated rock properties.

The rocks underlying many parts of Southeastern Nigeria had undergone extensive alterations to form considerable clay deposits. The mineralogical compositions of some of these clay deposits were evaluated with the X-Ray Diffraction (XRD) method to ascertain the suitability of the deposits as raw materials. Results of the analyses indicated that kaolinite (Al 2 Si 2 O 5 (OH) 4 ) is the dominant clay mineral. Traces of bentonite and dickite were also observed, while the identified non-clay minerals were quartz and iron. Chemical analysis of the clays revealed the predominance of SiO 2 , Al 2 O 3 , Fe 2 O 3 and TiO with values ranging from 31.70 to 56.45%, 19.30 to 29.30%, 3.11 to 29.42% and 2.21 to 7.04%, respectively, while the compositions of CaO, MgO, Na 2 O, and MnO in the analyzed samples were relatively lower with values ranging from 0.19 to 0.29%, 0.13 to 0.19%, 0.11 to 0.70% and 0.01 to 0.03%, respectively. The Al 2 O 3 /TiO 2 ratio (3.7 to 13.5) of the studied clays indicated a mafic to intermediate igneous rock origin. Binary plots of TiO 2 versus Al 2 O 3 to distinguish between granitic and basaltic sourced clays indicated basalt-rhyolite/granite provenances. The high chemical index of alteration (95.8%), chemical index of weathering (98.3%) and low contents of alkali and alkali earth elements (averaging 0.11%) of the clayrich sediments, is indicative of a relatively intense weathering source area. The SiO 2 -K 2 O/Na 2 O plots suggested that the sediments in the study area were deposited between passive and active continental margins. In comparison with other reference clays and standard specifications, the clay deposits in the study area possess characteristics satisfactory for economic and some engineering purposes.

Cenozoic sediments form extensive outcrops in the Niger Delta Basin. Detailed palynostratigraphic study was undertaken across Paleogene sequences exposed in Bende–Umuahia Area in up-dip sectors of the Niger Delta Basin, southeastern Nigeria, to establish different palynomorphs assemblage zones, with their corresponding ages. Palynological analysis was carried out on 27 selected outcrop samples, using the conventional maceration technique for recovering acid-insoluble organic-walled microfossils from sediments. Three Cenozoic lithostratigraphic units, including Imo Formation, Ameki Formation, and Ogwashi Formation, are exposed in the study area. Lithologies are sandstone, carbonaceous shale, mudstone, limestone, and the lignite. A total of 65 species of sporomorphs and 51 dinoflagellate cysts were identified. The recovered spores and pollen grains were used to establish six informal palynomorph assemblage zones, labeled as zone A – zone F, based on the first and the last occurrences of two or more species. These palynomorph assemblage zones include: (1) zone A — middle Paleocene Scabratriporites simpliformis–Bombacidites annae zone; (2) zone B — late Paleocene Foveotricolporites crassiexinus–Mauritidiites crassiexinus zone; (3) zone C — early Eocene Striatopollis catatumbus–Momipites africanus zone; (4) zone D — middle Eocene Margocolporites umuahiaensis–Gemmastephanocolporites brevicolpites zone; (5) zone E — late Eocene Cicatricosisporites dorogensis–Perfotricolpites nigerianus zone; and, (6) zone F — Oligocene–early Miocene Verrucatosporites usmensis–Magnastriatites howardii zone. The erected palynozones were correlated and compared with existing biozones in subsurface, down-dip sectors of the Niger Delta Basin, with pantropical palynological zones in tropical areas of Africa, and with palynofloral provinces of northern South America. A comparison of palynozones studied in southeastern Nigeria with other international palynozones, in this study, will assist in establishing the correlation of sediments for these areas.

The search for hydrocarbons has gone beyond shallow hydrostatic reservoirs, necessitating deep drilling beyond known depths in the mature Onshore Niger Delta fields. Often times, the challenge has been the ambiguity in pore pressure prediction beyond the shallow depths where disequilibrium compaction is no longer the active overpressure contributor. This leads to underbalanced drilling with the implication that well drilling is terminated at the occurrence of the first kick, before reaching the target depth. Thus, in this study, the dominant overpressure mechanism is determined by the analyses of velocity, density versus depth cross-plots. The Eaton empirical approach, equivalent depth method (EDM), a deterministic approach, and Bowers velocity-vertical effective stress (Vp-VES) relationship were applied to Vp-sonic log to compare prediction profiles. Pressure data were used to infer geologically consistent Eaton's exponents and Vp-VES curve for loading and unloading scenarios. The results show that deeper than the approximately 11,000 ft where unloading began, EDM and Eaton's exponent of 3.0 would fail. However, higher exponents can be adopted for the area at onset of unloading temperatures ranging from 98 to 100°C. The estimated shale pressure profile from the EDM, Eaton's exponents and Vp-VES models accurately fit the measured pressure data. In that way, the uncertainty in the prediction can be quantified. Hence, predrill estimates of shale pressures can be generated beyond known depths since the model can be used to transform seismic velocity to formation pressure, thereby ensuring better anticipation of potential risks and cost-effective drilling.