Gasification of sugarcane bagasse in supercritical water media for combined hydrogen and power production: a novel approach

A novel process based on supercritical water gasification has been used in this study for co-production of hydrogen and power from sugarcane bagasse as one of the main agricultural wastes of Iran. The cycle of the process was designed first, and then, the thermodynamic equilibrium model of the gasification process was simulated using ASPEN PLUS. The effects of temperature and feed concentration on molar fraction of main components of produced gas were investigated. The temperature was directly correlated with hydrogen production in which hydrogen and carbon monoxide production was favored at higher temperatures. The maximum hydrogen production occurred in the sugarcane bagasse concentrations about 20–30 wt%. Palladium membrane as a metallic dense membrane was used for separation of high-purity hydrogen. Hydrogen production of 8.55 kg/h and electrical power generation of 56 kW were obtained for the 20 wt% mixture of bagasse with a mass flow rate of 1000 kg/h, reactor pressure of 300 bars and temperature of 700 °C.     

Numerical modeling of fracking fluid migration through fault zones and fractures in the North German Basin

Gas production from shale formations by hydraulic fracturing has raised concerns about the effects on the quality of fresh groundwater. The migration of injected fracking fluids towards the surface was investigated in the North German Basin, based on the known standard lithology. This included cases with natural preferential pathways such as permeable fault zones and fracture networks. Conservative assumptions were applied in the simulation of flow and mass transport triggered by a high pressure boundary of up to 50 MPa excess pressure. The results show no significant fluid migration for a case with undisturbed cap rocks and a maximum of 41 m vertical transport within a permeable fault zone during the pressurization. Open fractures, if present, strongly control the flow field and migration; here vertical transport of fracking fluids reaches up to 200 m during hydraulic fracturing simulation. Long-term transport of the injected water was simulated for 300 years. The fracking fluid rises vertically within the fault zone up to 485 m due to buoyancy. Progressively, it is transported horizontally into sandstone layers, following the natural groundwater flow direction. In the long-term, the injected fluids are diluted to minor concentrations. Despite the presence of permeable pathways, the injected fracking fluids in the reported model did not reach near-surface aquifers, either during the hydraulic fracturing or in the long term. Therefore, the probability of impacts on shallow groundwater by the rise of fracking fluids from a deep shale-gas formation through the geological underground to the surface is small.     

Hydraulic fracturing: a toxicological threat for groundwater and drinking-water?

This paper deals with the possible impact of hydraulic fracturing (fracking), employed in the exploitation of unconventional shale gas and tight gas reservoirs, on groundwater, which is the most important source of drinking-water in Germany and many other European countries. This assessment, which is part of an interdisciplinary study by a panel of neutral experts on the risks and environmental impact of hydraulic fracturing, is based mainly on data obtained from three ExxonMobil drilling sites in northern Germany. First, the basic technical aspects of fracking and its relevant water fluxes are explained. The type, purpose and fate of the constituents of the fracking fluids are discussed. The chemicals used in the fracking fluids are assessed with regard to their hazardous properties according to the Regulation (EC) No. 1272/2008 of the European Parliament and of the Council on the classification, labelling and packaging of substances and mixtures (CLP regulation) and the German “Water Hazard Classes”. Contamination of groundwater by ingredients of fracking fluids may occur from under ground or may result from above-ground accidents associated with the transport, storage and handling of hazardous substances used as additives in fracking fluids. The degree of groundwater contamination cannot be predicted in a general way. Therefore, different dilutions of the fracking fluid in groundwater are considered. It is shown that the concentrations of most ingredients resulting from a 1:10,000 up to 1:100,000 dilution of the fracking fluid in groundwater are below health-based reference values such as the limit values of the European Drinking Water Directive, the WHO Guideline Values for Drinking-water Quality, and other health-based guide values for drinking-water. Regarding the salinity of fracking fluids, a dilution of 1:1,000 is sufficient to reach concentrations which are acceptable for drinking-water. From the human-toxicological point of view, the constituents of flowback water are more problematic with respect to drinking-water produced from groundwater than those of the fracking fluids. The few reliable data which have become available, as well as hydrogeological considerations, point in the direction of considerable salt concentrations and toxic constituents, e.g., Hg, As, Pb, Zn, Cd, BTX, PAHs, or even radioactive elements. The identification and assessment of reaction products and metabolites, which are produced as a result of the fracking operation and the metabolic activity of microorganisms, are important topics for further research. The recommendations include the need for a better understanding of the environmental impact of fracking operations, especially with regard to the development of sustainable rules for planning, permission, performance and management of fracking, and for the monitoring of groundwater quality around fracked drilling sites.     

Hydraulic fracturing wastewater in Germany: composition, treatment, concerns

When studying technical methods and measures that could be applicable for flowback treatment, recycling and/or disposal, it is important to characterize the volumes and composition of hydraulic fracturing flowback. In this work, water volumes and water quality data are considered for investigating flowback at three selected drilling sites in Germany. The analysis highlighted an increase of chloride concentrations up to saturation limit over the time. High salinity concentrations were used as indicator for estimating the percentage of hydraulic fracturing fluid and formation water in flowback. For the studied shale gas well a proportion of formation water, 69 %, and hydraulic fracturing fluid, 31 %, in flowback were derived. Thus, 92 % of the hydraulic fracturing fluid remained in the formation. The physical/chemical properties of flowback were categorized in groups to enable the allocation of applicable treatment methods. The analysis revealed that no single technology can meet suitable effluent characteristics, thus two or more treatment systems might be used in series operation. In particular, for flowback containing high salinity concentrations the only treatment options are evaporation or crystallization. Hence, methodological distinctions need to be made between concentration, elimination, disposal and recycling, whereby for the existing concentrate treatment or disposal measures need to be completed and scaled up into the process.     

Thermobarometry in the Sarvian Fe-skarn deposit (Central Iran) based on garnet–pyroxene chemistry and fluid inclusion studies

The Sarvian Fe skarn deposit is located in the Urumieh–Dokhtar magmatic arc, western Iran. The Sarvian quartz diorite intruded the surrounding Permian to Tertiary limy formation, culminated in thermal metamorphism as well as skarnification in which the Sarvian deposit formed. Microthermometry studies in the Sarvian skarn deposit reveal two distinct inclusion groups; group A with medium–high temperature and hypersaline and group B with low–medium temperature and low salinity. Group A inclusions which are entrapped during formation of prograde are thought to be derived from the magmatic source. Fluid boiling and subsequent developing of hydraulic fracturing led to inflow and/or mixing of early magmatic fluids (group A) with circulating groundwater culminated in formation of low salinity and low temperature fluid inclusions (group B) during the formation of retrograde assemblage. Fluid inclusion thermometry reveals the formation temperature and the salinity of 300–370 °C and 31–33 wt% NaCl for the prograde stage and 180–230 °C and 1–15 wt% NaCl for the retrograde stage of skarnification at Sarvian skarn rocks. Fe-mineralization as well as hydrothermal minerals occurred during retrograde metasomatism. The estimated depth and pressure of occurrence for prograde stage are 1000–1200 m and 100–150 bars, and for retrograde stage, these are about 200 m and 50 bars, respectively. Garnet and pyroxene, as the main constituent minerals of prograde stage, are the most informative minerals offering a suitable tool to constrain the skarnification conditions. Garnets in the Sarvian deposit are mainly grossular and andradite, showing both normal and inverse zoning as the result of variation in their chemical composition. Such types of zoning represent alternation of high acidity oxidation and low acidity oxidation conditions that were prevailed on skarnification in the Sarvian prograde assemblage. Also, chemical composition of the Sarvian pyroxenes shows an alternation of high oxygen fugacity and low oxygen fugacity conditions for their formation. This is also supported by fluctuation of the ratios of andradite to grossular and diopside to hedenbergite, denoting to an obvious shifting that was prevailed between oxidizing and redox conditions during formation of prograde assemblage in the Sarvian. Garnet–pyroxene thermometry determines the formation temperature of prograde assemblage between 370 and 550 °C at Sarvian skarn rocks which is verified also by fluid inclusion thermometry. Decomposition of limestone by reaction of high-temperature hydrothermal fluids with carbonate host rock resulted in injection of CO₂ into the Sarvian system that caused oxidation, changing Fe⁺² to Fe⁺³ culminated in the magnetite deposition.     

Implementation of an integrated vulnerability and risk assessment model

An integrated vulnerability and risk assessment model (IVR) is proposed. The proposed model is a composite index that assesses the relationships among four critical components, namely exposure, hazard, vulnerability and capacities and measures, and how these can be used to illustrate the integrated risk and vulnerability situation of an area. These factors are assessed using individual variables. Fifty-four variables, objectively decided upon, were used to measure the contribution of each component factor. The general characteristics of vulnerability, risk, exposure and capacities and measures are well known; however, the relative importance of each variable and their inter-relatedness, in measuring risk and vulnerabilities, as demonstrated by the IVR; and how these in turn affect the impacts of natural hazards, are still debatable. The IVR though provides a valid, reliable and sensitive tool, which can be used to further explore these relationships. Through robust testing and application, subjectivity in the selection of variables can be reduced. Moreover, through the establishment of a database for data collection and storage, objectivity (reliability) can be achieved as well as, availability of the requisite data inputs. The sensitivity of the model allows for the quick identification of strategic action, which will ultimately lead to hazard loss reduction. The values yielded for each component factor can help decision-makers in the allocation of scarce developmental funds as well as identify trends in levels of risk, vulnerability, exposures and capacities and measures as well as determine areas where mitigation strategies are needed most.     

Probabilistic tsunami hazard assessment along Oman coast from submarine earthquakes in the Makran subduction zone

The Sultanate of Oman is among the Indian Ocean countries that were subjected to at least two confirmed tsunamis during the twentieth and twenty-first centuries: the 1945 tsunami due to an earthquake in the Makran subduction zone in the Sea of Oman (near-regional field tsunami) and the Indian Ocean tsunami in 2004, caused by an earthquake from the Andaman Sumatra subduction zone (far - field tsunami). In this paper, we present a probabilistic tsunami hazard assessment for the entire coast of Oman from tectonic sources generated along the Makran subduction zone. The tsunami hazard is assessed taking into account the contribution of small- and large-event magnitudes. Results of the earthquake recurrence rate studies and the tsunami numerical modeling for different magnitudes were used through a logic-tree to estimate the tsunami hazard probabilities. We derive probability hazard exceedance maps for the Omani coast considering the exposure times of 100, 250, 500, and 1000 years. The hazard maps consist of computing the likelihood that tsunami waves exceed a specific amplitude. We find that the probability that a maximum wave amplitude exceeds 1 m somewhere along the coast of Oman reaches, respectively, 0.7 and 0.85 for 100 and 250 exposure times, and it is up to 1 for 500 and 1000 years of exposure times. These probability values decrease significantly toward the southern coast of Oman where the tsunami impact, from the earthquakes generated at Makran subduction zone, is low.     

Sulfide geochemistry and genesis of Chouichia and Ain el Bey copper deposits in northwestern Tunisia

The Chouichia and Ain el Bey copper veins that occur in the Eastern Atlas fold belt in northwestern Tunisia, are hosted in Upper Cretaceous-Paleogene sedimentary sequences in a regional transcurrent shear zone. Paragenetic assemblages were formed during four distinct stages all of which are separated by fracturing and brecciation: Stage 1 consists of low temperature siderite (160–180 °C) formation in association with pyrite, including framboidal pyrite and marcasite. Stage 2 includes pseudomorphing of marcasite by As-rich pyrite and arsenopyrite, and formation of chalcopyrite at higher temperatures (200–300 °C) from S-rich, Fe-Cu-bearing fluids; As contents in individual pyrite and arsenopyrite crystals increase markedly in the rims relative to the centers, thus indicating non-equilibrium conditions. Stage 3 involves fracturing and brecciation predating deposition of enargite, luzonite and tennantite at Ain el Bey, and famatinite and tetrahedrite at Chouichia, from As-Sb-Bi-bearing oreforming fluids; tennantite-tetrahedrite series exhibit iron and copper-excess replacements in tetrahedral sites interrelated with Cu-Fe interactions (electron transfer). In Stage 4 fracturing was followed by calcite formation in voids. Comprehensive data was obtained from scanning electron microprobe (SEM) and microprobe chemical analyses of minerals, geothermometry using sulfur isotopes, As contents in arsenopyrite crystals and fluid inclusions in siderite and calcite, support an input of magmatic hydrothermal ore-forming fluids, although contamination by sedimentary sulfur were also identified.     

煤层气井水力压裂液分析与展望

对目前煤层气常用的压裂液体系进行了分析,对比各自的优缺点及其适用性,并重点分析了泡沫压裂液与清洁压裂液的性能,通过实验室数据与实际应用效果得出,泡沫压裂液体系应优选N₂为其气相;清洁压裂液需要降低合成条件与成本,并研究清洁压裂液内部破胶技术,以减少破胶剂的使用,保护环境。目前煤层气压裂液存在的主要问题有:传统压裂液对地层伤害大,先进的技术难以推广应用,新型压裂液成本高,工艺复杂等;针对存在的问题提出相应的对策:传统压裂液应针对不同敏感性地层条件研制出合适的破胶体系,优化工艺,加强配套工艺技术的研究等。最后指出高效、低伤害、低成本是今后煤层气压裂液的发展方向,开展疏水缔合聚合物-黏弹性表面活性剂清洁压裂液体系、纳米技术的研究,也是今后煤层气压裂、提高煤层气产量的重要手段。      

Major and trace-element composition and pressure–temperature evolution of rock-buffered fluids in low-grade accretionary-wedge metasediments, Central Alps

The chemical composition of fluid inclusions in quartz crystals from Alpine fissure veins was determined by combination of microthermometry, Raman spectroscopy, and LA-ICPMS analysis. The veins are hosted in carbonate-bearing, organic-rich, low-grade metamorphic metapelites of the Bündnerschiefer of the eastern Central Alps (Switzerland). This strongly deformed tectonic unit is interpreted as a partly subducted accretionary wedge, on the basis of widespread carpholite assemblages that were later overprinted by lower greenschist facies metamorphism. Veins and their host rocks from two locations were studied to compare several indicators for the conditions during metamorphism, including illite crystallinity, graphite thermometry, stability of mineral assemblages, chlorite thermometry, fluid inclusion solute thermometry, and fluid inclusion isochores. Fluid inclusions are aqueous two-phase with 3.7–4.0 wt% equivalent NaCl at Thusis and 1.6–1.7 wt% at Schiers. Reproducible concentrations of Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, B, Al, Mn, Cu, Zn, Pb, As, Sb, Cl, Br, and S could be determined for 97 fluid inclusion assemblages. Fluid and mineral geothermometry consistently indicate temperatures of 320 ± 20 °C for the host rocks at Thusis and of 250 ± 30 °C at Schiers. Combining fluid inclusion isochores with independent geothermometers results in pressure estimates of 2.8–3.8 kbar for Thusis, and of 3.3–3.4 kbar for Schiers. Pressure–temperature estimates are confirmed by pseudosection modeling. Fluid compositions and petrological modeling consistently demonstrate that chemical fluid-rock equilibrium was attained during vein formation, indicating that the fluids originated locally by metamorphic dehydration during near-isothermal decompression in a rock-buffered system.     

Impacts of small woody debris on slurrying,persistence, and propagation in a low-gradient channel of the Dongyuege debris flow in Nu River,Southwest China

Debris flows occurring in well-vegetated alpine areas usually contain a range of sizes of woody debris. Large woody debris (LWD), which has a retaining effect on further transportation of debris downstream, is mainly distributed in upstream reaches, and the amount of small woody debris (SWD) deriving from LWD increases dramatically midstream and downstream. The Dongyuege (DYG) bouldery debris flow with a sandy-matrix took place in a wildwood area, causing 96 deaths and its clay-sized fraction does not contain typical clay minerals. However, its total travel distance and runout distance in a low-gradient reach (between 2° and 5°) upstream of the depositional fan apex reached 11 km and 3.3 km, respectively. The abundant SWD in the DYG debris flow might have played a crucial role in slurrying, persistence, and the long runout over the low gradient. To understand why this debris flow extended so far, slurrying experiments, pore water escape experiments, and excess pore pressure experiments were performed. Crude debris (CD) collected from the DYG debris flow deposit was used throughout the experiments, the tested materials of which are separated into CD-containing SWD with a maximum grain size (MGS?=?2 mm), purified debris (PD) without SWD with a MGS of 2 mm, and SWD <?2 mm in diameter. In the five slurrying experiments with PD-SWD-water mixtures, as the SWD content was elevated from 0.0 to 2.0 wt%, the current velocity of escaping pore water decreased uniformly from 17.2 to 0.9 mm/s. When the SWD content was 1.0 wt% or greater, the mixtures can be considered as one-phase flows of viscous fluids. The six pairs of pore water escape experiments based on the slurries remolded with CD and PD, respectively showed that the time needed for pore water to escape from the CD slurries was much greater than those from their PD counterparts. Also, measured was the dissipation rate of the relative excess pore pressure of CD and PD slurries of various densities and volumes, which showed that most of the rates of the PD-slurries were always greater than CD-slurries. Overall, the results show that SWD has a strong influence on the slurrying of the DYG debris without typical clay minerals found in other debris flows, and SWD helps to sustain the high excess pore pressure in the interior of the debris flow mass which resulted in the extended travel distance over such a low gradient. SWD favors the formation and stability of one-phase water-debris mixtures because of its large specific surface area and low density, which makes it able to absorb fine particles and able to be suspended in slurry flows over long timescales. In well-vegetated mountainous areas, SWD should be taken into account in the assessment of debris-flow hazards.     

Formation and evolution of carbonate chimneys at the Lost City Hydrothermal Field

The Lost City Hydrothermal Field at 30°N, near the Mid-Atlantic Ridge, is an off-axis, moderate temperature, high-pH (9-10.8), serpentinite-hosted vent system. The field is hosted on ∼1.5 Ma crust, near the summit of the Atlantis Massif. Within the field, actively venting carbonate chimneys tower up to 60 m above the seafloor, making them the tallest vent structures known. The chemistry of the chimneys and vent fluids is controlled by serpentinization reactions between seawater and underlying peridotite. Mixing of <40-91 °C calcium-rich vent fluids with seawater results in the precipitation of variable mixtures of aragonite, calcite, and brucite. The resultant deposits range from tall, graceful pinnacles to fragile flanges and delicate precipitates that grow outward from fissures in the bedrock. In this study, mineralogy, petrographic analyses, major and trace element concentrations, and Sr isotopic compositions are used to propose a model for the growth and chemical evolution of carbonate chimneys in a serpentinite-hosted environment. Our results show that nascent chimneys are characterized by a porous, interlacing network of aragonite, and brucite minerals that form extremely fragile structures. The chemistry of these young deposits is characterized by ∼10 wt% Ca and up to 27 wt% Mg, extremely low trace metal concentrations, and ⁸⁷Sr/⁸⁶Sr isotope ratios near 0.70760. During aging of the chimneys, progressive reactions with seawater result in the dissolution of brucite, the conversion of aragonite to calcite, and infilling of pore spaces with calcite. The oldest chimneys are dominated by calcite, with bulk rock values of up to 36 wt% Ca and <1 wt% Mg. These older structures contain higher concentrations of trace metals (e.g., Mn and Ti), and have Sr isotope ratios near seawater values (0.70908). Exposed ultramafic rocks are prevalent along the Mid-Atlantic, Arctic, and Indian Ocean ridge networks and it is likely that other Lost City-type systems exist.     

Heavy metal exposure from co-processing of hazardous wastes for cement production and associated human risk assessment

This study was carried out to determine the concentration of heavy metals (Cd, Ni, Pb, Cr, Ni and Zn) in ordinary Portland cement (OPC) produced from the co-processing with hazardous waste in comparison with OPC produced using natural raw materials. The results showed that the concentration of heavy metals in cement produced from natural raw material was in the order of Zn > Pb > Cr > Ni > Cu > Cd. Zn and Cd were the highest and the lowest concentrations, respectively, in cements produced from the co-processing activity. The difference between heavy metals concentrations in OPC produced with and without co-processing was found to be statistically significant. The concentration of heavy metals in the cement produced is generally factory dependent. The human risk assessment associated with the heavy metals for non-carcinogenic and carcinogenic risks has been evaluated. The calculated hazard index (HI) and total lifetime cancer risks (LCR) were lower than the acceptable threshold reference values, HI < 1 and LCR < 1 × 10^?4, respectively. Thus, it is anticipated that there is no potential of non-carcinogenic and carcinogenic risks for both adult and children. However, the findings indicated that there is a need for regulatory monitoring. The exposure pathway for both non-carcinogenic and carcinogenic risks are both in the order of ingestion > dermal > inhalation.     

泥石流的二维数学模型

泥石流是在重力作用下,由砂粒石块和水等组成的固液混合物,是一种发生于山区的复杂的地质灾害现象。泥石流主要是由暴雨诱发引起的,它沿着复杂的三维地形高速流动,具有流体流动的特性。为了模拟泥石流的运动规律,预测降雨诱发的泥石流的到达距离和泛滥范围,减少和避免泥石流引起的灾害,把泥石和雨水组成的固液混合物假定为遵循均匀、连续、不可压缩的、非定常的牛顿流体运动规律。基于质量守恒方程和Naiver-stokes方程,采用深度积分方法,推导出了一个模拟泥石流运动的二维数学模型。所有方程式可用有限差分法来求解。结合GIS,该模型可用于预测泥石流的流动距离和泛滥范围,以及泛滥范围内的危险房屋和路段,也可以用于泥石流灾害的风险性分析。     

A study on soil physico-chemical, microbial and metal content in Sukinda chromite mine of Odisha, India

Soil samples from chromite mining site and its adjacent overburden dumps and fallow land of Sukinda, Odisha, were analysed for their physico-chemical, microbial and metal contents. Chromite mine soils were heterogenous mixture of clay, mud, minerals and rocks. The pH of the soils ranges between 5.87 and 7.36. The nutrient contents of the mine soils (N, P, K and organic C) were found to be extremely low. Analysis of chromite mine soils revealed accumulation of a number of metals in high concentrations (Fe > Cr > Mn > Ni > Zn > Pb > Sr) which exceeded ecotoxicological limits in soil. Correlation and cluster analysis of metals revealed a strong relation between Cr, Ni, Fe, Mn among the different attributes studied. Assessment of different microbial groups such as fungi, actinomycetes and bacteria (heterotrophic, spore forming, free-living nitrogen fixing, phosphate solubilising and cellulose degrading) from mine soils were found to be either extremely low or absent in some soil samples. Further chromium tolerant bacteria (CTB) were isolated using 100 mg/L Cr(VI) enriched nutrient agar medium and were screened for their tolerance towards increasing concentrations of hexavalent chromium and other toxic metals. Out of 23 CTB isolates, three bacteria tolerated up to 900 mg/L, 6 up to 500 mg/L, 20 up to 200 mg/L of Cr(VI). These bacteria were also found to be sensitive towards Cu > Co > Cd and very few CTB strains could show multiple metal tolerance. These strains have great scope for their application in bioremediation of toxic chromium ions in presence of other metals ions, which needs to be explored for their biotechnological applications.     

Chromium,molybdenum, vanadium,and fluoride sorption from steelwork slag eluates by different mineral additives

Today, the environmental behavior of steelwork slags is very important for their application. When slags are used as building materials, they can interact with water and soil, with the possibility of leaching of harmful components, e.g., metals such as vanadium or anions such as fluoride. The leachable concentrations of various environmentally relevant parameters have to be below defined limit values, which are given by environmental authorities. In this study, different mineral additives have been investigated for their suitability to reduce chromium, molybdenum, vanadium, and fluoride concentrations in slag eluates, as a basis for planned investigations of the long-term leaching behavior of slag/additive mixtures. Seven mineral additives including iron oxide hydroxide, sludge from aluminum production, triple superphosphate, two water work sludges I and II, zeolite powder, and zeolite granules were tested for their efficiency to sorb trace elements and fluoride from four slag eluates comprising two basic oxygen furnace slags and two electric arc furnace slags. The limit values according to the German Alternative Construction Material Ordinance were used to verify which additives were able to minimize concentrations of trace elements and fluoride in slags eluates. Due to high eluate concentrations, the sludge from aluminum production and the triple superphosphate could be excluded from further investigations. The efficiency of the other additives follows the trend iron oxide hydroxide > water work sludges > zeolites. Particularly, the iron oxide hydroxide and the water work sludge I seem to be appropriate to enhance possible applications of slags with respect to the German regulation.     

First Data on Formation Conditions of the Zhilnoye Au–Ag Epithermal Gold Deposit (Eastern Chukotka,Russia)

The first data on study of individual fluid inclusions in the Zhilnoye deposit have been obtained. It has been found that the gold-bearing quartz veins of the deposit were formed by heterogeneous hydrothermal fluids with low salt concentrations (0.2–3.6 wt% equiv. NaCl under intermediate temperature conditions of 246–350°C). The fluid pressure was 80–160 bar corresponding to 0.3–0.6 km depths of formation under hydrostatic conditions. The parameters of the mineral-forming fluids of the Zhilnoye deposit correspond to typical parameters of the fluids of epithermal deposits.     

煤储层水基压裂液用表面活性剂的筛选实验

水力压裂会对煤储层造成水锁伤害,在压裂液中加入表面活性剂是减缓水锁伤害的有效途径。采用1.5% KCl溶液为基液,在其中加入不同浓度的阴离子型表面活性剂AS和非离子型表面活性剂NS,配置出8种压裂液,分别对河东煤田柳林沙曲矿的焦煤样和太原西山屯兰矿的瘦煤样进行静置沉降实验、毛细管压力测试和离心分离实验,最终优选出煤储层水基压裂液用最佳表面活性剂为0.05% AN复配溶液（AS:NS=9:1）,由此构成了表面活性剂压裂液（1.5% KCl+0.05% AN）。研究结果表明,在水基压裂液中加入0.05% AN复配溶液（AS:NS=9:1）,可以大幅度降低压裂液的表面张力,改变压裂液的界面状态,从而增加煤表面的亲水性,降低煤孔隙的毛细管压力,使得压裂液的可排性增强,进而能够有效控制储层的水锁伤害,实现增产。      

Hydraulic fracturing in unconventional gas reservoirs: risks in the geological system, part 2

Hydraulic fracturing is a method used for the production of unconventional gas resources. Huge amounts of so-called fracturing fluid (10,000–20,000 m³) are injected into a gas reservoir to create fractures in solid rock formations, upon which mobilised methane fills the pore space and the fracturing fluid is withdrawn. Hydraulic fracturing may pose a threat to groundwater resources if fracturing fluid or brine can migrate through fault zones into shallow aquifers. Diffuse methane emissions from the gas reservoir may not only contaminate shallow groundwater aquifers, but also escape into the atmosphere where methane acts as a greenhouse gas. The working group “Risks in the Geological System” as part of ExxonMobil’s hydrofracking dialogue and information dissemination processes was tasked with the assessment of possible hazards posed by migrating fluids as a result of hydraulic fracturing activities. In this work, several flow paths for fracturing fluid, brine and methane are identified and scenarios are set up to qualitatively estimate under what circumstances these fluids would leak into shallower layers. The parametrisation for potential hydraulic fracturing sites in North Rhine-Westphalia and Lower Saxony (both in Germany) is derived from literature using upper and lower bounds of hydraulic parameters. The results show that a significant fluid migration is only possible if a combination of several conservative assumptions is met by a scenario.