Permeability measurements in mudrocks using gas-expansion methods on plug and crushed-rock samples

Permeability is an important parameter relative to the production of hydrocarbons in shale oil/gas plays; however, the measurement of permeability in these nano-to microdarcy rocks remains a challenge. Results from different methods or from different laboratories are not consistent, and reasons are not fully understood. In the present study, permeability is measured for both plug and crushed-rock samples with different plug diameter or crushed-sample particle size to systematically investigate the permeability measurement to better understand and apply the measured results. A modified gas-expansion (MGE) method, which can measure permeability for plug samples under confining pressures, was established and applied to several Eagle Ford and Barnett Shale (mudrock) samples. Permeability results from this method are in fair agreement with those from the pulse-decay method. The traditional Gas Research Institute (GRI) method was applied to crushed-rock Eagle Ford Shale samples. The results were comparable to reported permeability for an Eagle Ford Shale sample. Particle or plug size has significant influence on permeability measurement. In general, permeability increases with increasing particle or plug size. For crushed sample with GRI method, the reason of increasing permeability is related to the limitation of the GRI technique and the data analysis method. Estimate of the permeability based on Kozeny–Carman Equation was conducted, and the results were used to evaluate the GRI permeability measurement. Particle size of 2–4 mm (5–10 meshes) is considered as an appropriate size for GRI permeability measurement. For plug sample, larger permeability with larger plug diameter is most likely caused by the artificial fractures. Higher confining pressure can reduce the influence of the fractures, but cannot fully remove it. A range of permeability, defined by the GRI permeability with 2–4 mm particles as the lower boundary and permeability of 1-in plug under high confining pressure (>5000 psi) as the upper boundary, can be a more reliable measures to represent the shale matrix permeability. The range of the permeability also highlights the uncertainty in matrix permeability measurement for shale.     

Modeling environmental effects on the size-structured energy flow through marine ecosystems. Part 2: Simulations

Numerical simulations using a physiologically-based model of marine ecosystem size spectrum are conducted to study the influence of primary production and temperature on energy flux through marine ecosystems. In stable environmental conditions, the model converges toward a stationary linear log–log size-spectrum. In very productive ecosystems, the model predicts that small size classes are depleted by predation, leading to a curved size-spectrum.It is shown that the absolute level of primary production does not affect the slope of the stationary size-spectrum but has a nonlinear effect on its intercept and hence on the total biomass of consumer organisms (the carrying capacity). Three domains are distinguished: at low primary production, total biomass is independent from production changes because loss processes dominate dissipative processes (biological work); at high production, ecosystem biomass is proportional to primary production because dissipation dominates losses; an intermediate transition domain characterizes mid-production ecosystems. Our results enlighten the paradox of the very high ecosystem biomass/primary production ratios which are observed in poor oceanic regions. Thus, maximal dissipation (least action and low ecosystem biomass/primary production ratios) is reached at high primary production levels when the ecosystem is efficient in transferring energy from small sizes to large sizes. Conversely, least dissipation (most action and high ecosystem biomass/primary production ratios) characterizes the simulated ecosystem at low primary production levels when it is not efficient in dissipating energy.Increasing temperature causes enhanced predation mortality and decreases the intercept of the stationary size spectrum, i.e., the total ecosystem biomass. Total biomass varies as the inverse of the Arrhenius coefficient in the loss domain. This approximation is no longer true in the dissipation domain where nonlinear dissipation processes dominate over linear loss processes. Our results suggest that in a global warming context, at constant primary production, a 2–4 °C warming would lead to a 20–43% decrease of ecosystem biomass in oligotrophic regions and to a 15–32% decrease of biomass in eutrophic regions.Oscillations of primary production or temperature induce waves which propagate along the size-spectrum and which amplify until a “resonant range” which depends on the period of the environmental oscillations. Small organisms oscillate in phase with producers and are bottom-up controlled by primary production oscillations. In the “resonant range”, prey and predators oscillate out of phase with alternating periods of top-down and bottom-up controls. Large organisms are not influenced by bottom-up effects of high frequency phytoplankton variability or by oscillations of temperature.     

Role of Siliceous Fossil Dissolution in Downcore Variations of Grain Size and Water Content: Western Margin of Clarion-Clipperton Fracture Zone, NE Equatorial Pacific

Grain size and water content in box-core sediments from the Clarion-Clipperton fracture zone (C-C zone) in the northeast equatorial Pacific were analyzed in detail to understand the downcore variations across a hiatus between Quaternary and Tertiary layers. Grain-size distributions in the topmost core sediments show two modes: a coarse mode (peaked at 50 μm) and a fine mode (at 2-25 μm). The coarse mode disappears gradually with depth accompanied by the dissolution of siliceous fossil tests, whereas the fine mode coarsens due to the formation of authigenic minerals. Water content increases abruptly across a color boundary between an upper pale brown layer and a lower dark brown layer that is the hiatus between Quaternary and Tertiary layers. Abundant smectites and microvoid molds, which are created by the prolonged fossil dissolution in the underlying sediment, are attributed for the abrupt downcore variation of water content. Overall variations in grain size and water content in the topmost core sediments in the western C-C zone are possibly constrained by the dissolution of biogenic siliceous fossils. Variations in geotechnical properties related to these changes must be considered in the design of nodule collectors.     

试论工业区工业企业成组布局的经济效果和最佳规模的确定

分析了工业区工业企业成组布局与分散布局相比较的经济效果,并采用年费用指标作为评价成组布局经济效果的基本指标。本文还分析了工业成组布局的经济效果与工业区规模之间的关系。本文以年费用最小为目标函数,以成组布局工业区的一些主要企业(基本企业)和与其相应的具有替代关系的分散布局企业(对比企业)为变量,建立了工业成组布局经济效果及最佳规模优化模型。     

Influence of damage on pore size distribution and permeability of rocks

The model proposed in this article relates permeability to porosity measurements that can easily be performed in the laboratory. The pore size distribution (PSD) curve is updated with strains and damage. The updated volumetric fractions of natural pores and cracks are introduced in the expression of permeability. Contrary to classical permeability models based on PSD integrations, the model proposed in this article accounts for possible changes in the porosity modes: one mode for undamaged samples and two modes for cracked samples. The proposed approach also accounts for varying states of damage, as opposed to classical fracture network models, in which the cracks pattern is fixed. The only material parameters that are required to describe the microstructure are the lower and upper bounds of the pores size for both natural pores and cracks. All the other PSD parameters involved in the model are related to macroscopic parameters that can easily be determined in the laboratory, such as the initial void ratio. The framework proposed in this article can be used in any damage constitutive model to determine the permeability of a brittle porous medium. Drained triaxial compression tests have been simulated. Before cracks initiation, permeability decreases while the larger natural pores are getting squeezed. After the occurrence of damage, permeability grows due to the increase of cracks density. The model performs well to represent the influence of the confining pressure on damage evolution and permeability variations. Copyright © 2012 John Wiley & Sons, Ltd.     

哈尔滨地区积雨云降水微结构特征

1999年5－7月，采用PMS公司生产的GBPP－100型地面雨滴谱仪，对哈尔滨地区各镒降水过程进行了观测。本文对其中的7次雷雨过程进行重点分析，得到积雨云降水的雨滴谱分布、微结构以及起伏特征等一些有意义的结果。     

Enzymatic release of amino acids from different humic substances

Humic substances isolated from water, sediment, and soil were characterized by applying elemental analysis, spectroscopic analysis, and gelchromatographic molecular size distribution. In addition, the amounts and pattern of enzymatically released amino acids were determined. Depending on the origin of the humic substances, the percentage of released amino acid nitrogen related to the total nitrogen was in the range of 0.4 to 26.7%. The samples particularly differed in the content of leucine und tyrosine. The total amount of released amino acids was compared with the results obtained from the other characterization methods. This approach indicated that humic substances with a high content of hydrolysable amino acids had high N/C and O/C ratios and low molecular sizes. Beside this, the absorption of these substances in the UV and visible wavelength range was quite low, while the measured ratios of SAK(254)/SAK(436) showed high values. This work leads to the conclusion that the extent of enzymatically releasable amino acids is not only dependant on the nitrogen content of humic substances. Other physical and chemical properties have to be considered for the understanding of the results obtained by the described biochemical characterization method.     

A development of the lichenometric method applied to the dating of glacially influenced debris flows in southern chile

Lichenometry is a dating technique that has problems relating to questionable assumptions. The development of a size frequency approach, previously used in attempts to resolve some of the problems, is described and applied to the dating of four debris flows marginal to the San Rafael Glacier in Southern Chile. This study provides examples of the development's application, its problems and directions for further work. The size frequency approach, based on new assumptions, uses parameters derived from population size frequency distributions of the lichen species Placopsis patagonica to provide relative and absolute dating for rock surfaces. Changes in the shapes of distributions suggest the relative age of populations. Absolute dating is based on a curve (spanning a 24 year time period) derived from mean diameter size/age correlations. A stratified random sampling design permits the use of inferential statistics. Standard deviations and confidence intervals show error margins, the degree of relatedness between neighbouring populations, and populations that are anomalous. One-way analysis of variance is used to indicate where populations may safely be grouped. The size frequency approach appears to be particularly suitable for use on unstable debris flows where secondary movements are common. The approach also demonstrates that lichen growth and colonization are sensitive to aspect differences and other variations in microhabitat.     

Variation of phytoplankton biomass and primary production in Daya Bay during spring and summer

Environmental factors, phytoplankton biomass (Chl a) and primary production of two water areas in Daya Bay (Dapeng'ao Bay and Aotou Bay) were investigated during the transition period from spring to summer. Chl a ranged from 3.20 to 13.62 and 13.43 to 26.49 mg m(-3) in Dapeng'ao Bay and Aotou Bay respectively, if data obtained during red tides are excluded. Primary production varied between 239.7 and 1001.4 mg Cm(-2) d(-1) in Dapeng'ao Bay. The regional distribution of Chl a and primary production were mostly consistent from spring to summer in both bays. Seasonal transition characters have been found in Daya Bay from spring to summer, including high values of DO, nitrate and silicate. Size structures of phytoplankton and its primary production do not change very much from spring to summer, with micro-phytoplankton dominating and contributing about 50% of the whole. In Daya Bay, phytoplankton is limited by nitrogen in spring, and by phosphate in summer. Artificial impacts are evident from high temperature effluent from nuclear power stations, aquaculture and sewage. During the investigation, a red tide occurred in Aotou Bay, with a maximum Chl a of 103.23 mgm(-3) at surface and primary production of 2721.9 mg Cm(-2) d(-1) in the red tide center. Raised water temperature and nutrient supply from land-sources help to stimulate annual red tides.     

Understanding size and boundary effectsin scaled model blasts - plane problems

This contribution addresses model blasting and focuses on size and boundary effects on wave propagation, fracture pattern development and fragmentation in small scale laboratory size specimen. Small cylindrical specimens are centre-line loaded by linear high velocity of detonation explosive charges and detonated.

Using elastic wave propagation theory and fracture mechanics it is shown that the type of boundary conditions which prevail at the outer boundary of the cylinder control the extension of bore-hole cracking and fragmentation within the body of the cylinder. In the case of a composite cylinder with dissimilar mantel and core materials, the level of fracturing and fragmentation is controlled by the delamination of the interface. This, in turn, depends on the relative diameters of the core and the mantel. The most important parameter though is the ratio between the length of the pulse (space-wise or time-wise) and the characteristic dimensions of the models, i.e. in this case the diameters of the core and the mantel.

The theoretical basis for a simplified two-dimensional plane treatment is developed. Simple or composite, thin, plate-like specimens are centrally loaded; whereas the core is always a circle, the mantel can be either a circle or a square.