Magister Scientiae - MSc / Commercial hydrocarbon production relies on porosity and permeability that defines the storage capacity and flow capacity of the resevoir. To assess these parameters, petrographic and petrophysical log analyses has been found as one of the most powerful approach. The approach has become ideal in determining reservoir quality of uncored reservoirs following regression technique. It is upon this background that a need arises to integrate petrographic and petrophysical well data from the study area. Thus, this project gives first hand information about the reservoir quality for hydrocarbon producibility. Five wells (A-J1, A-D1, A-H1, A-K1 and K-A2) were studied within the Orange Basin, Offshore South Africa and thirty five (35) reservoirs were defined on gamma ray log where sandstone thickness is greater than 10m. Eighty three (83) sandstone samples were gathered from these reservoirs for petrographic analyses within Hauterevian to Cenomanian sequences. Thin section analyses of these sediments revealed pore restriction by quartz and feldspar overgrowths and pore filling by siderite, pyrite, kaolinite, illite, chlorite and calcite. These diagenetic minerals occurrence has distructed intergranular pore space to almost no point count porosity in well K-A2 whilst in A-J1, A-D1, A-H1 and A-K1 wells porosity increases at some zones due to secondary porosity. Volume of clay, porosity, permeability, water saturation, storage capacity, flow capacity and hydrocarbon volume were calculated within the pay sand interval. The average volume of clay ranged from 6% to 70.5%. The estimated average effective porosity ranged from 10% to 20%. The average water saturation ranged from 21.7% to 53.4%. Permeability ranged from a negligible value to 411.05mD. Storage capacity ranged from 6.56 scf to 2228.17 scf. Flow capacity ranged from 1.70 mD-ft to 31615.82 mD-ft. Hydrocarbon volume varied from 2397.7 cubic feet to 6215.4 cubic feet. Good to very good reservoir qualities were observed in some zones of well A-J1, A-K1 and A-H1 whereas well A-D1 and K-A2 presented poor qualities.

This study refers to a qualitative and quantitative weathering characterization of a gneiss rock mass (weathering profile, intact rock and discontinuity) in a tropical region. The rock mass was excavated for a construction of an unlined railway tunnel, which during its useful life began to present block instability problems linked to the weathering and the time of exposure of the rock. The weathering of the rock mass and its weathering grades are approached in the geological and geotechnical points of view, covering bibliographical review on the subject, field inspection, direct and indirect investigations, and laboratory tests: petrographic analysis, X-ray diffraction, physical properties and durability index, sclerometry, ultrasonic test, uniaxial and diametral compression. / Este estudo se refere à caracterização qualitativa e quantitativa do intemperismo de um maciço rochoso gnáissico (perfil de intemperismo, rocha intacta e descontinuidades) em uma região tropical. O maciço foi escavado para a construção de um túnel ferroviário não revestido, que ao longo da vida útil começou a apresentar problemas de instabilidade de blocos vinculados ao intemperismo e ao tempo de exposição da rocha. O intemperismo do maciço rochoso e os seus graus de alteração foram abordados do ponto de vista geológico e geotécnico, levando-se em consideração uma ampla revisão bibliográfica sobre o tema, inspeção de campo, investigações diretas e indiretas, e os seguintes ensaios laboratoriais: análise petrográfica, difratometria de raios X, índices físicos e de durabilidade, esclerometria, ultrassom, compressão uniaxial e diametral.

Coal seam gas has been recognised as a new, potential energy resource in New Zealand. Exploration and assessment programmes carried out by various companies have evaluated the resource and indicated that this unconventional gas may form a part of New Zealand's future energy supply. This study has delineated some of the controls between coal properties and gas content in coal seams in selected New Zealand locations. Four coal cores, one from Huntly (Eocene), two from Ohai (Cretaceous) and one from Greymouth (Cretaceous), have been sampled and analysed in terms of gas content and coal properties. Methods used include proximate, sulphur and calorifc value analyses; ash constituent determination; rank assessment; macroscopic analysis; mineralogical analysis; maceral analysis; and gas analyses (desorption, adsorption, gas quality and gas isotopes). Coal cores varied in rank from sub-bituminous B-A (Huntly); sub-bituminous C-A (Ohai); and high volatile bituminous A (Greymouth). All locations contained high vitrinite content (~85 %) with overall relatively low mineral matter observed in most samples. Mineral matter consisted of both detrital grains (quartz in matrix material) and infilling pores and fractures (clays in fusinite pores; carbonates in fractures). Average gas contents were 1.6 m3/t in the Huntly core, 4.7 m3/t in the Ohai cores, and 2.35 m3/t in the Greymouth core. The Ohai core contained more gas and was more saturated than the other cores. Carbon isotopes indicated that the Ohai gas composition was more mature, containing heavier 13C isotopes than either the Huntly or Greymouth gas samples. This indicates the gas was derived from a mixed biogenic and thermogenic source. The Huntly and Greymouth gases appear to be derived from a biogenic (by CO2 reduction) source. The ash yield proved to be the dominant control on gas volume in all locations when the ash yield was above 10 %. Below 10 % the amount of gas variation is unrelated to ash yield. Although organic content had some influence on gas volume, associations were basin and /or rank dependant. In the Huntly core total gas content and structured vitrinite increased together. Although this relationship did not appear in the other cores, in the Ohai SC3 core lost gas and fusinite are associated with each other, while desmocollinite (unstructured vitrinite) correlated positively with residual gas in the Greymouth core. Although it is generally accepted that higher rank coals will have higher adsorption capacities, this was not seen in this data set. Although the lowest rank coal (Huntly) contains the lowest adsorption capacity, the highest adsorption capacity was not seen in the highest rank coal (Greymouth), but in the Ohai coal instead. The Ohai core acted like a higher rank coal with respect to the Greymouth coal, in terms of adsorption capacity, isotopic signatures and gas volume. Two hypothesis can be used to explain these results: (1) That a thermogenically derived gas migrated from down-dip of the SC3 and SC1 drill holes and saturated the section. (2) Rank measurements (e.g. proximate analyses) have a fairly wide variance in both the Greymouth and Ohai coal cores, thus it maybe feasible that the Ohai cores may be higher rank coal than the Greymouth coal core. Although the second hypothesis may explain the adsorption capacity, isotopic signatures and the gas volume, when the data is plotted on a Suggate rank curve, the Ohai coal core is clearly lower rank than the Greymouth core. Thus, pending additional data, the first hypothesis is favoured.

Coal seam gas has been recognised as a new, potential energy resource in New Zealand. Exploration and assessment programmes carried out by various companies have evaluated the resource and indicated that this unconventional gas may form a part of New Zealand's future energy supply. This study has delineated some of the controls between coal properties and gas content in coal seams in selected New Zealand locations. Four coal cores, one from Huntly (Eocene), two from Ohai (Cretaceous) and one from Greymouth (Cretaceous), have been sampled and analysed in terms of gas content and coal properties. Methods used include proximate, sulphur and calorifc value analyses; ash constituent determination; rank assessment; macroscopic analysis; mineralogical analysis; maceral analysis; and gas analyses (desorption, adsorption, gas quality and gas isotopes). Coal cores varied in rank from sub-bituminous B-A (Huntly); sub-bituminous C-A (Ohai); and high volatile bituminous A (Greymouth). All locations contained high vitrinite content (~85 %) with overall relatively low mineral matter observed in most samples. Mineral matter consisted of both detrital grains (quartz in matrix material) and infilling pores and fractures (clays in fusinite pores; carbonates in fractures). Average gas contents were 1.6 m3/t in the Huntly core, 4.7 m3/t in the Ohai cores, and 2.35 m3/t in the Greymouth core. The Ohai core contained more gas and was more saturated than the other cores. Carbon isotopes indicated that the Ohai gas composition was more mature, containing heavier 13C isotopes than either the Huntly or Greymouth gas samples. This indicates the gas was derived from a mixed biogenic and thermogenic source. The Huntly and Greymouth gases appear to be derived from a biogenic (by CO2 reduction) source. The ash yield proved to be the dominant control on gas volume in all locations when the ash yield was above 10 %. Below 10 % the amount of gas variation is unrelated to ash yield. Although organic content had some influence on gas volume, associations were basin and /or rank dependant. In the Huntly core total gas content and structured vitrinite increased together. Although this relationship did not appear in the other cores, in the Ohai SC3 core lost gas and fusinite are associated with each other, while desmocollinite (unstructured vitrinite) correlated positively with residual gas in the Greymouth core. Although it is generally accepted that higher rank coals will have higher adsorption capacities, this was not seen in this data set. Although the lowest rank coal (Huntly) contains the lowest adsorption capacity, the highest adsorption capacity was not seen in the highest rank coal (Greymouth), but in the Ohai coal instead. The Ohai core acted like a higher rank coal with respect to the Greymouth coal, in terms of adsorption capacity, isotopic signatures and gas volume. Two hypothesis can be used to explain these results: (1) That a thermogenically derived gas migrated from down-dip of the SC3 and SC1 drill holes and saturated the section. (2) Rank measurements (e.g. proximate analyses) have a fairly wide variance in both the Greymouth and Ohai coal cores, thus it maybe feasible that the Ohai cores may be higher rank coal than the Greymouth coal core. Although the second hypothesis may explain the adsorption capacity, isotopic signatures and the gas volume, when the data is plotted on a Suggate rank curve, the Ohai coal core is clearly lower rank than the Greymouth core. Thus, pending additional data, the first hypothesis is favoured.