No description available.

No description available.

No description available.

The Nigerian igneous rocks described in this thesis are the Younger Granites from Northern Nigeria. The granites are sub-divided into four groups, namely, the early granites and porphyries group; the biotite-granite-group; the riebeckiteblotite- granite group and the riebeckite-granite group and, analysed for trace elements by various techniques. The distribution of Li, F, Ga, Rb, Sr, Y, Zr, Nb, Sn, Ba, La, Yb and Pb in over 70 specimens is discussed to characterise the granite groups. The early granites and porphyries group always contains lower trace element concentrations of Li, F, Rb, Y, Nb, Sn, Yb, and Pb than the biotite-granite group, the riebeckitebiotite- granite group or the riebeckite-granite group. concentrations of Li, Rb, Y, Nb, and Yb are similar in the biotite-granite group and the riebeckite-granite group (exeluding the albite-riebeckite-granites), but the contents of F, Zr and (Sn) can be used to distinguish between the granite groups. The albite-riebeckite-granites (especially those from Amo Rop and Liruei) are unique in their concentrations of Li, V, Ga., Rb, Y, Nb, Sn and Yb. More significant trends do occur in individual ring structures though the range of values varies from complex to complex. An attempt is also made to interpret the cycle of magmatic evolution and Ga, lib and Zr are the most useful element:3 in elucidating some aspects of this process.

The plutonic members of the complexes that comprise the Younger Granite province of Northern Nigeria, include gebbros, syenites, amphibole-fayalite granites and porphyries, amphibole-biotite, biotite, and riebeckite granites, and a short petrographic account of these rocks is riven. Mineralogically the plutonic rocks are characterised by a varied assemblage of mafic minerals, of which the most important are members of the olivine, pyroxene, amphibole and biotite groups; all the ferromagnesian minerals are iron-rich. Analyses nave been made of calcium and soda-rich pyroxenes, calciferous and alkali amphiboles, biotites, cossyrite and ilmenites, that come from some of the above mentioned rocks, and the analytical results are presented and discussed. Whenever possible an attempt has been mane to correlate changes in chemical composition of the analysed minerals with variations in optical properties and, in the case of the amphiboles, variations in unit-cell parameters. Compositional trends in the analysed ferromagnesian minerals have been discussed and compared with compositional trends in the plutonic rocks of the Younger Granite complexes. The possible conditions of formation of some of the analysed ferromagnesian minerals have been considered in the light of experimental studies. The distribution of the complexes throughout the Younger Granites Province is commented upon, and several problems of the evolution of the Younger Granites are discussed.

No description available.

Nuclear magnetic resonance T₂ measurements for estimating permeability and drainage capillary pressure, particularly in tight sandstones, are investigated. An assessment of popular permeability models suggested that permeability is hard to predict universally. The best a model may achieve, compared with the measured permeability, is one order of magnitude. As a result of the research the effective surface relaxivity is solved in collaboration with transverse mean relaxation rate using two large siliciclastics datasets. The developed correlation (p = 0.92T₂¯0.935) was used to convert NMR spectrum to capillary pressure. An improved NMR permeability model is developed (K = CaTP30r1+1); whereby the correlation is not influenced by total porosity but uses properties that are directly related to flow. Effective tortuosity correlates with the ratio of bound to free fluid; as a result a new cementation factor equation is derived. A direct prediction of pore volume from NMR is developed, the approch uses the sum of NMR amplitude (PV = 0.017SA — 0.24), and avoids complex computations and corrections. The modelled drainage capillary pressure replicated the measured curvature; it enhances the conventional fixed scaling factor method and allows permeability predictions. However the calibre of the calculated permeabilities is subject to a good match between the predicted and modelled capillary pressure. The developed NMR permeability model assumes a good relationship between the pore throat and pore body and that mean T₂ is correlated to permeability. However, conditions for using NMR to characterise reservoir properties are that its signal is proportional to the pore size and the absence of paramagnetic ions. Nonetheless, this study illustrates clearly that NMR is an important reservoir characterisation tool.

No description available.

No description available.

No description available.