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Energy extraction and conversion
Published in Kornelis Blok, Evert Nieuwlaar, Introduction to Energy Analysis, 2020
Kornelis Blok, Evert Nieuwlaar
In the first stages, kerogen (organic compounds with a high molecular mass) is formed, which can be converted into hydrocarbons by a natural cracking process. As time passes and the hydrocarbons are subject to high temperatures and pressures, natural gas can be formed. The hydrocarbon liquids and gases are mobile and start to migrate through pores and fractures. Normally, porous underground layers are saturated with water; oil and gas are less dense than water, so they migrate upwards through the water-filled pores. Oil and gas accumulate under anticlines, which are up-arched sedimentary strata that contain impermeable layers (see Figure 5.2). The rising oil and gas collect at the apex of the fold. Due to density differences, the gas sits on top of the oil, which sits on top of the water. Faults can form structural traps, as can salt domes.
Geophysics for site selection, monitoring and operation of groundwater recharge projects
Published in Peter J. Dillon, Management of Aquifer Recharge for Sustainability, 2002
B, H and M are all vectors and mG and k are scalar quantities, which are the absolute permeability of vacuum and the magnetic susceptibility of the material, respectively. The contour values on the maps are then absolute values of the magnetic induction obtained from readings taken by a proton precession magnetometer after correcting for diurnal variations of the earth’s magnetic field and sometimes after the regional gradient is removed. In these maps the proper recognition of magnetic anomalies can lead to the identification of unknown geologic features or serve to corroborate some that had been defined by other methods. Some of these features may be relevant to the proper location of groundwater recharge projects. Examples of these are faults, anticlinal and synclinal structures and grabens all of which may produce magnetic anomalies. Faults may produce zones of high fracture density in bedrock aquifers and be favorable sites for locating recharge wells (Figure 1). Grabens and synclines may be filled along their axes with younger sediments that have good storage and hydraulic conductivity characteristics and could be favorable sites for emplacing large direct surface recharge facilities. On the other hand, anticlines may produce areas of shallow bedrock that have unfavorable storage and transmission characteristics for either well recharge or basin recharge methods. Interpretation of magnetic anomalies can be qualitative and quantitative. For site selection at a regional scale a qualitative approach will suffice. This consist of recognizing and delineating anomaly patterns in regional magnetic maps. On a first analysis five major patterns can be correlated to certain geologic features (Parasnis 1986). These are: Circular features frequently associated with igneous rock intrusions Long narrow features frequently associated with dikes, techtonic shear zones, isoclinally folded strata and ore bodies.Dislocation usually related to faultsSheets of anomalies correlated to basalt flows, large gabbro intrusive bodies and green belts.‘Quiet’ areas represented by extensive areas of low relief and no distinctive pattern of contours which are frequently associated with felsic rocks and limestones.
Landscape evolution and hydrogeochemical characteristics of the Pourewa Stream catchment, lower North Island, New Zealand
Published in New Zealand Journal of Geology and Geophysics, 2019
Callum Rees, Julie Palmer, Alan Palmer, Ranvir Singh
The Manawatu plains in the eastern Whanganui Basin contain a series of NE-SW trending anticlines, including the Pohangina, Feilding, Marton, Mt Stewart-Halcombe, and Oroua anticlines (Feldmeyer et al. 1943; Te Punga 1952, 1957). They are bounded on their eastern side by westward dipping reverse faults that only rarely reach the surface (Melhuish et al. 1996; Jackson et al. 1998; Begg et al. 2005). The anticlines are asymmetric, characterised by gentle western slopes (c. 2°) and steep eastern slopes (up to 70°), a geometry interpreted to reflect the underlying reverse faults (Jackson et al. 1998).