Al2O3 ceramics with well-oriented and hexagonally ordered pores: The formation of microstructures and the control of properties
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The view about the higher porosity with the higher permeability has guided high porosity and high permeability reservoir production operations,but in the low porosity and low permeability reservoirs,there often appears the phenomenon contrary to this view,the capacity difference is very large in almost the same porosity reservoir.Experiment data from 250 rock samples indicate that permeability is not obviously controlled by the total porosity in the low porosity and low permeability rock,traditional porosity-permeability calculation method is no longer applicable.In the low porosity and low permeability rock,permeability is mainly controlled by pore structure,the pore with different pore sizes has different contribution to the permeability,the pore sizes and the corresponded proportion in the pores control the permeability value together.On this basis,the nuclear magnetic resonance logging is used to depict the pore size ranges,then the interval porosity is used to calculate the permeability.This method not only improves the permeability calculation accuracy in the low porosity and permeability reservoir but also develops the traditional formula,it can effectively guide the productivity evaluation of low porosity and low permeability reservoirs in the future.
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Abstract Compared with the seismic wave fields, the influence of porosity and permeability to seismoelectric coupling may be more significant. The seismoelectric effect mainly forms the coseismic signals (CS) and interface response (IR). The influences of the porosity and permeability on the two types of seismoelectric field are still not clear. In this paper, we numerically analyze the response characteristics of the CS and IR with the dependency of porosity and permeability, respectively. The differences in the sensitivity of the CS and the IR fields to porosity and permeability are also determined. The results show that the change of permeability is mainly sensed by the IR field, while the CS has almost no obvious response to it: both the CS and IR fields are sensitive to the change of porosity, but the sensitivity of the IR field is higher and with the increase of porosity, the discrepancy between the sensitivity of the CS and IR fields to porosity changes increases. The signal amplitude anomaly will be caused in both P-wave fields and seismoelectric fields (IR and CS) at the geological body where the porosity changes, but the change of permeability has little impact on the P-wave and only induces an obvious IR amplitude anomaly in seismoelectric fields. This indicates that the seismoelectric effect can better reveal the connectivity characteristics of the geological body than the seismic wave. This investigation can help to distinguish the sensitivity of seismoelectric response to porosity and permeability more clearly.
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Porosity, permeability, and storativity were measured during isostatic hot‐pressing of fine‐grained calcite aggregates at temperatures of 633 to 833 K, confining pressures of 200 to 300 MPa, and argon pore pressures of 100 to 250 MPa. The progressive changes in total porosity were measured in situ by monitoring the sample length changes. The connected porosity and the permeability and storativity were measured in situ by incrementing and oscillating pore pressure techniques, respectively. In a given test, there was a decrease with time in the rate of reduction of porosity, the rates being higher at higher temperature and effective pressure. The permeability k was nonlinearly related to the total porosity ϕ in the form k ∝ ϕ n . The exponent n was approximately equal to 3 and thus consistent with the prediction of the “equivalent channel” model, in the range of porosity from 0.18 down to 0.07. Below 0.07, n became much larger (around 14), an effect that can be attributed to loss of connectivity and which is qualitatively similar to that observed by Bernabé et al. [1982] in post‐hot‐pressing measurements. However, a cube law continues to apply below 0.07 total porosity if the permeability is related to the connected porosity itself. The storativity is also nonlinearly related to the porosity. Model analyses of the permeability and storativity results indicate both that the pore apertures decrease and that the pore shapes become more equant as the porosity decreases. The marked downturn in the permeability‐porosity relationship at total porosities below 0.07 appears from microscopical observation to correspond to a change in pore geometry from largely connected, irregular pores between grains to isolated, tubular pores at junctions of several grains. Application of the “Swiss‐cheese” continuum percolation model indicates a percolation threshold of about 0.04 porosity. Microstructural evidence, the apparent activation energy for densification, and the stress dependence of densification rate suggest that porosity reduction has occurred mainly by dislocation creep.
Overburden pressure
Hot isostatic pressing
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Abstract Permeability and porosity are the two most important parameters of rocks for the evaluation and exploitation of oil/gas reservoirs. In this study, a modified pulse‐decay method has been developed to measure both permeability and porosity simultaneously. In the present method, the gas pressure in one chamber is changed (increased or decreased) instantaneously and then maintained constant, while the pressure response changing with time in the other one is monitored. A mathematical model of this procedure has been formulated, and a general analytical solution, including the early‐time and late‐time evolutions, has been obtained. The late‐time solution is presented for postprocessing of experimental data, which leads to the simultaneous measurement of permeability and porosity values of tight rocks. Our measurements agree well with those from the classical pulse‐decay and gas expansion methods. Compared with measuring the permeability and porosity separately, the proposed method can reduce the total test time and ensure the permeability and porosity are measured under the same effective stress condition.
Effective porosity
Petroleum reservoir
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Micro photoforming is considered to be a useful and promising technique for manufacturing microstructures or micromechanisms. But the materials used in usual photoforming methods are restricted to UV photohardenable resins, and their properties are usually found unsatisfactory. In this paper, the authors proposed a new application of micro photoforming for manufacturing ceramic microstructures. According to the proposal, a liquid mixture, which is made by blending a photohardenable resin and ceramic powders, is used to photoform microstructures in the green state. The resin in the microstructures can be burnt out by so called deresining at appropriate temperature between 450°C and 600°C, and finally the ceramic microstructures can be obtained after sintering at higher temperature. In this paper, the authors also describe the instrumentation for micro photoforming, report some fundamental results that show the promising feasibility of micro photoforming for making three dimensional microstructures in the green state.
Manufacturing process
Liquid state
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Abstract Petrophysical evaluation of shaly gas sand reservoirs is one of the most difficult problems. These reservoirs usually produce from multiple layers with different permeability and complex formation, which is often enhanced by natural fracturing. In this study, we propose a new model to predict porosity and permeability using derived data from NMR. The developed Neural Network (NN) model uses the NMR T2 pin values, and density and resistivity logs to predict porosity, and permeability for two test wells. The NN trained model has displayed good correlation with core porosity and permeability values, and with the NMR derived porosity and permeability in the test wells. This work focuses on determination of porosity (DMR) from combination of density porosity and NMR porosity and permeability from NMR logs using Bulk Gas Magnetic Resonance Permeability (KBGMR). Neural network (NN) technique is used to predict formation porosity and permeability using NMR and conventional logging data. Predicted porosity and permeability have shown a good correlation with core porosity and permeability in the studied shaly gas sand reservoir.
Petrophysics
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Two step
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In this paper, we report an analysis of pressed paper in terms of porosity and permeability. Previously, we reported a pressed paper that exhibits decreased porosity and permeability. Additionally, its applications into programmed sample delivery as well as flow rate control were reported. However, there is a need for a theoretical analysis of pressed paper in terms of porosity and permeability for a more precise design principle and its applications because porosity and permeability are important factors in determining fluidic behavior. Here, we propose a theoretical model for analyzing decreased porosity and permeability in pressed paper. Porosity and permeability of pressed paper were quantitatively calculated using experimental results with a theoretical model. Furthermore, based on the analyzed results of porosity and permeability in pressed paper, a porosity⁻permeability relationship was investigated.
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