尾矿坝排渗设施中土工织物选用的渗透性准则

通过初步的试验研究，确定了有压和土工织物受污染情况下渗透系数会产生变化，提出了土工织物选用的渗透性公式Ｋｇ≥ηｓηｐＫｓ，最后讨论ηｓ、ηｐ的取值。     

Constrained mixture design applied to the development of cassava starch-chitosan blown films

Films composed of cassava starch, chitosan and glycerol were produced by blown extrusion and employing a design for constrained surfaces and mixtures. The effects of the components of the mixture on the mechanical properties, water vapor permeability (WVP) and opacity of the films were studied. According to the models generated by the design, the concentration of starch had a positive effect in all properties. The plasticizer glycerol and its interactions with other components had a positive effect on increasing the WVP. The presence of a higher relative concentration of chitosan favored the formation of more rigid and opaque and less permeable films. In general, the concentrations of starch, chitosan and glycerol led to changes in the film properties, potentially affecting their performance. The design for constrained surfaces and mixtures proved to be a useful tool for this type of study due to the complexity of the conditions of film formation.     

流动剪切对几种聚合物水基凝胶形成的影响

以低剪切速率下的库受特流动近似模拟瓶中实验条件,以通过单填砂管的连续循环流动（渗流）模拟注入地层深部的条件,研究了ＨＰＡＭ／乙酸铬,ＨＰＡＭ／酚醛树脂,黄原胶／乙酸铬等３种体系在流动剪切过程中的凝胶化特点和形成的弱凝胶的弱凝胶的剪切敏感性,考察了填砂粒度,流速和温度对渗流场中弱凝胶形成的影响。     

Degradation of gas diffusion layers through repetitive freezing

This work investigates the degradation of an individual gas diffusion layer (GDL) by repeated freezing cycles. The pore size distribution, gas permeability, surface structure, and contact angle on the surface of the GDL were measured in four different types of GDL: SGL paper with a microporous layer (MPL); SGL paper with 5 wt% of polytetrafluoroethylene (PTFE) loading; Toray paper without PTFE loading; and Toray paper with 20 wt% of PTFE loading. After repeated freezing cycles, the porosity of the GDL without PTFE was reduced by 27.2% due to the volumetric expansion of the GDL. The peak of the log differential intrusion moved toward a smaller pore diameter slightly because of the repeated freezing process. The crack of the MPL increased in its width and length after repeated freezing cycles. The through-plane gas permeability of the GDL with the MPL doubled after repeated freezing cycles due to the growth of the crack in the MPL, but was very small for the GDLs with Toray paper. Besides, the GDLs with PTFE loading showed a relatively larger decrease in the contact angle on the surface than the GDL without PTFE loading due to the separation of PTFE from the carbon fiber during the repeated freezing process.     

The effects of sub-critical and super-critical carbon dioxide adsorption-induced coal matrix swelling on the permeability of naturally fractured black coal

Swelling of the coal matrix with the adsorption of CO₂ is one of the leading problems for CO₂ sequestration in deep coal seams as it causes coal seam permeability to be significantly reduced. The main objective of this study was to investigate the effect of coal mass swelling on the permeability of naturally fractured black coal. A series of permeability tests were conducted using a newly developed tri-axial apparatus on 38 mm by 76 mm naturally fractured black coal specimens. These tests were carried out for CO₂ and N₂ injections at 2-20 MPa injection pressures under 10 to 24 MPa confining pressures at 33 °C. Each coal specimen was then allowed to swell under sub-critical and super-critical CO₂ adsorption and the corresponding effects on CO₂ and N₂ permeabilities were examined. Results indicate that the permeability of naturally fractured black coal is significantly reduced due to matrix swelling, which starts as quickly as within 1 h of CO₂ injection. A further reduction is then observed, and the maximum swelling rate occurs within the first 3-4 h of CO₂ adsorption. The amount of coal matrix swelling due to CO₂ adsorption clearly depends on the phase condition of the CO₂, and super-critical CO₂ adsorption-induced swelling is about two times higher than that induced by sub-critical CO₂ adsorption. Interestingly, although a fractured coal specimen which has already fully swelled under sub-critical CO₂ adsorption can swell significantly more under super-critical CO₂ adsorption, after swelling under super-critical CO₂ adsorption, no further swelling effect occurs under any CO₂ pressure or phase condition. Moreover, the swelling process continues longer under super-critical CO₂ adsorption. It is concluded that super-critical CO₂ adsorption can induce more matrix swelling than sub-critical CO₂ adsorption under the same adsorption pressure.     

顺北油气田非均质碳酸盐岩储层矿化度敏感规律

顺北油气田受断裂多期活动的影响产生了大量的裂缝储集体,具有缝洞型碳酸盐岩特征。针对顺北油气田碳酸盐岩储层的矿化度敏感性评价可知,多个样品数据难以形成统一结论,无法有效指导现场生产。X射线全岩矿物测定一间房组、鹰山组储层垂直方向方解石、白云石、硅质、黏土矿物总含量波动范围在0.9%～65%。扫描电镜观察片状伊蒙混层集中充填裂缝,裂缝数量及形态随机性分布。氦气与氮气法测定2套储层垂直方向的孔隙度为0.42%～2.40%、渗透率为0.03～7.62 mD,波动明显且总孔隙空间较小。测定一间房组水敏、盐敏渗透率损害率为29.47%～74.80%、30.44%～82.93%;鹰山组水敏、盐敏渗透率损害率为66.06%～74.80%、78.10%～79.91%,矿物组分与裂缝发育非均质导致不同区域矿化度敏感性显著波动。用数学方法建立了渗透率损失率、无敏感矿化度范围与黏土矿物总含量比、孔隙度、渗透率、地层水矿化度等因素间定量数学关系,提高储层矿化度敏感评价全面性和快速性,计算临界矿化度KCl溶液较传统方法污染储层渗透率降幅缩小了19.90%,提高矿化度敏感控制效果明显。     

A fractal permeability model for bi-dispersed porous media

In this paper a fractal permeability model for bi-dispersed porous media is developed based on the fractal characteristics of pores in the media. The fractal permeability model is found to be a function of the tortuosity fractal dimension, pore area fractal dimension, sizes of particles and clusters, micro-porosity inside clusters, and the effective porosity of a medium. An analytical expression for the pore area fractal dimension is presented by approximating the unit cell by the Sierpinski-type gasket. The pore area fractal dimension and the tortuosity fractal dimension of the porous samples are determined by the box counting method. This fractal model for permeability does not contain any empirical constants. To verify the validity of the model, the predicted permeability data based on the present fractal model are compared with those of measurements. A good agreement between the fractal model prediction of permeability and experimental data is found. This verifies the validity of the present fractal permeability model for bi-dispersed porous media.     

A study on H2S permeability of CsHSO4 membranes

The gas permeability of H₂S gas at 150 °C through ultra-thin cesium hydrogen sulfate (CsHSO₄) membranes has been investigated. Gas chromatography–mass spectrometry analyses indicate that CsHSO₄ membrane is impermeable to H₂S gas under test conditions. The apparent micropore diameter of the membrane averaged between 9.5 and 11.5 Å with a maximum permeance of 0.09 Barrer (6.75 × 10⁻¹⁹ m² s⁻¹ Pa⁻¹). Atomic force microscope and X-ray diffraction analyses show respectively that the surface morphology and crystal structure of the membranes are preserved, with no adverse effect from prolonged exposure to H₂S gas. Electrochemical impedance spectroscopy analysis confirm over a 30% decrease in membrane resistance via an 80% reduction in membrane thickness.     

An analytical model for the transverse permeability of gas diffusion layer with electrical double layer effects in proton exchange membrane fuel cells

An analytical model is presented for the transverse permeability of gas diffusion layer (GDL) based on an ordered array of parallel charged circular cylinders at the steady state. The formula of calculating the permeability of the transverse direction is given by solving the fluid momentum equation in a unit cell. In the present approach, the proposed model is explicitly related to the porosity and fiber radius of fibrous porous media, the zeta potential, and the physical properties of the electrolyte solution. Besides, the effects of these parameters (the porosity, unit cell aspect ratio, fiber radius, and molar concentration) on the transverse permeability are discussed detailedly. The model predictions are compared with the previous studies in the available literature, and good agreement is found.     

Impacts of low harm fracturing fluid on fossil hydrogen energy production in tight reservoirs

The polymer fracturing fluid has been gradually used in the fossil hydrogen energy field. However, its impacts on the fields are still unclear. In this study, a series of experiments were conducted to solve the problem. First, a new method called the pressure transmission test (PTT) was used to evaluate the permeability damage induced by polymer fracturing fluid. Then several rock properties were tested to reveal rock potential damage induced by the aqueous fracturing fluid, after that the interactions between polymer fracturing fluid and rock were discussed in detail. Results showed that the average permeability pollution is 10.6. Permeability and X-ray diffraction (XRD) tests stated that the core is easier to be blocked by particles in the formation or fracturing fluid residue. Blocking and scanning electron microscope (SEM) tests showed that the nanoscale polymer would stick on the rock surface, and reduce the pore size. Our work provides a new method to evaluate the impact of polymer fracturing fluid on tight reservoirs. Moreover, the mechanism of permeability damage caused by the polymer fracturing fluid was also revealed.