An Experimental Study on Percolation Characteristics of a Single-PhaseGas in a Low-Permeability Volcanic Reservoir Under High Pressure
In this paper, we find that with the decrease in the average pore pressure in the process of gas production, both the slippage effect and the stress sensitivity effect will gradually increase; the increase in the slippage effect is significant, while the increase in the stress sensitivity effect is not. In this paper, the Kalamay volcanic gas reservoir of the Junggar Basin in China was selected as the object of our research. The gas reservoir has typical fractured volcanic reservoirs, and the long-term percolation feature remains unclear. To study the percolation characteristics of single- phase gas under high pressure, the experimental method was designed to simulate these characteristics in the process of gas production by measuring the gas flow in the core and the input and output pressure at both ends. We carried out simulation experiments of single-phase gas flow percolation characteristics under high pressure using 11 pieces of vol- canic rock samples in three wells of the study area. The results show that as the core pore pressure increased, the per- meability of low-permeability cores of the volcanic rock decreased significantly at room temperature. However, this decrease became more gradual, which means that the higher the core pore pressure is, the smaller the permeability variation caused by gas slippage is; when the pore pressure is above 10 MPa, the permeability is nearly constant, slip- page effect significantly reduces in the process of gas percolation, so it can be completely ignored under these forma- tion conditions. As the pore pressure decreases, the slippage effect and stress sensitivity effect will gradually increase; when the pore pressure is less than 10 MPa, the permeability appears to increase significantly, and this is especially true for a pressure of 5 MPa. The main cause of this result is the slippage effect of gas seepage during the depletion of the gas reservoir, when the pore pressure is lower than a certain value. The valid stress changes of the core are not large, and the stress sensitivity is not strong, so the slippage effect plays a major role, which leads to an increase in the gas permeability during the late period of certain flow gas production.
Hydrocarbon Seepage, Gas Hydrates, and Authigenic Carbonate in the Northwestern Gulf of Mexico
Rapid deposition of organic rich sediments onto thick Jurassic salt deposits created conditions conducive to the formation and entrapment of large volumes of oil and gas as well as active salt diapirism. Resulting hydrocarbon seepage, brine seepage, hydrate formation and decomposition, methane oxidation, oil degradation and authigenic carbonate precipitation have significantly affected the geology, geochemistry and morphology of the continental slope of the northern Gulf of Mexico. Regional topography is largely controlled by salt diapirism and slumping, and is characterised by pock marks, mud volcanoes, disrupted sediments and large accumulations of carbonate. Sediment chemistry is driven by the influx of oil, gas and brine seepage and secondarily altered by the enhanced microbial and benthic biology. See also Abstract No. 89051216.
Changes in Quartz During Heating and the Possible Effects on Si Production
In Si and FeSi production, the main Si source is SiO2, in the form of quartz. Reactions with SiO2 generate SiO gas that further reacts with SiC to Si. During heating, quartz will transform to other SiO2 modifications with cristobalite as the stable high-temperature phase. Transformation to cristobalite is a slow process. Its rate has been investigated for several industrial quartz sources and has been shown to vary considerably among the different quartz types. Other differences in behavior during heating between these quartz sources, such as softening temperature and volume expansion, have also been studied. The quartz-cristobalite ratio will affect the rate of reactions involving SiO2. The industrial consequences and other implications of the observed difference between quartz types are discussed. Initial studies of industrial quartz were published by Ringdalen et al. In the current work, a new experimental method has been developed, and an investigation of several new quartz sources has confirmed the earlier observed large variation between different sources. The repeatability of the data has been studied and the effect of gas atmosphere investigated. The results from the earlier work are included as a basis for the discussion.