Natural Fissures Research Articles

Experimental study of microstructure and rock properties of shale samples

The study of shale mechanical properties is very important for well completion and stimulation in shale gas reservoirs. Thus,the geomechanical properties of Paleozoic marine shale in Lower Yangtze Basin were studied.With the application of argon ion polisher,high-solution CT and scanning electron microscope,the shale samples were processed and their microstructures were observed. Besides, mineral compositions of this shale were analyzed by XRD technique. In order to get the compression characteristic of shale, the scratch and uniaxial experiments were performed. In addition, the loading and unloading situations were simulated under different effective stress conditions in order to reduce negative effects of natural fissures and rock relaxation. Finally,the multi-stage triaxial compression deformation experiment was performed on the triaxial rock testing system for calculating cohesive strength and inherent friction angle. The study of shale mechanical properties is veryimportant for well completion and stimulation in shale gas reservoirs. Thus, a systematic experiments was performed on Paleozoic marine shale samples collected from Lower Yangtze Basin, and the microscopic structure,mineral compositions and the geomechanical properties of marine shale samples were studied. Testing result shows that except for shale sample with natural fractures,both the values of Youngs modulus and Poissons ratio increase with the increase of confining pressure. But in the unloading condition, the Young s modulus increases with the decrease of confining pressure,whereas the Poisson s ratio is greater than that in its loading condition. The inherent friction angle is within approximately 40°and the shale sample with high brittleness index tends to crack as fracture network according to the multi-stage triaxial compression test. This research is greatly helpful for the study of shale mechanical properties,and provides technical parameters for well completion design and stimulation.

Optimization of Completions in Unconventional Reservoirs

This article, written by Assistant Technology Editor Karen Bybee, contains highlights of paper SPE 143066, ’Optimization of Completions in Unconventional Reservoirs for Ultimate Recovery - Case Studies,’ by Daniel J. Snyder, SPE, and Rocky Seale, SPE, Packers Plus Energy Services, originally prepared for the 2011 SPE EUROPEC/EAGE Annual Conference and Exhibition, Vienna, Austria, 23-26 May. The paper has not been peer reviewed. Over the last decade, an industry-wide shift to unconventional plays has been made possible by advances in technology, allowing the recovery of previously uneconomic reserves. The primary objective of completions in these unconventional reservoirs is to increase the effective surface area of the well to maximize reservoir contact. The full-length paper provides an introduction to unconventional reservoirs, describes the main methods of horizontal multistage completions, and discusses how the choice of method can affect good fracturing practices as well as long-term production. Introduction Unconventional Reservoirs. Over the last decade, an industrywide shift to unconventional plays has occurred as a result of the depletion of mature conventional reservoirs, increased demand, and advances in technology. Unconventional reservoirs have been defined as formations that cannot be produced at economic flow rates or that do not produce economic volumes of oil and gas without stimulation treatments or special recovery processes and technologies (Fig. 1). Types of unconventional reservoirs include those with poor fluid-flow characteristics because of small inter-pore connections and/or with stacked pay units. The primary objective of completions in these unconventional reservoirs is to increase the effective surface area of the well to maximize reservoir contact. Horizontal drilling and multistage fracturing are two technologies that accomplish this. The two main methods of horizontal multistage completions currently used in unconventional reservoirs are cemented liner “plug and perf” and openhole multistage-fracturing systems. Although both methods have the same goal of increasing access to the reservoir by the induction of fractures along the entire length of the horizontal wellbore, they differ significantly from an operational perspective. Cemented-Liner Multistage-Fracturing Method. This type of completion involves cementing production casing in the horizontal wellbore and plug-and-perf stimulation. Mechanical isolation in the liner is accomplished by setting bridge plugs using pump-down wireline or coiled tubing (CT), followed by perforating and then fracturing the well to provide access to the reservoir. The cement provides the mechanical diversion in the annulus, while the bridge plug provides the mechanical diversion inside the liner. This process then is repeated for the number of stimulations desired for the horizontal wellbore. After all stages have been completed, CT is used to drill out the composite plugs, thus re-establishing access to the toe of the horizontal wellbore. Although an effective method of creating diversion along the horizontal section for discrete-stage stimulation, the inherent cost of multiple interventions with CT, perforating guns, and deployment of fracturing equipment needed for each stage is extremely high, not to mention being very inefficient and time consuming. Production using this method also can be limiting because cementing the wellbore closes many of the natural fractures and fissures that would otherwise contribute to overall production.

Effects of ozonized water and heat treatment on the papaya fruit epidermis

This study examined the effects of O3 and hot water treatments on the epidermis of Golden papaya fruit. Heat treatments were applied in a hot water brushing (HWB) system. Papayas were brushed under a pressurized hot water rinse stage at 45, 55 and 65°C for 60s. In the HWB treatment, 4ppm ozone was applied to the papayas for 1 or 2min. The results show that ozone applications did not affect the fruit's cuticular surface, while heat treatments allowed natural fissures on the fruit epidermis to recover. Several crystalloid forms were identified on the epidermis of the papayas after the heat treatments. The predominant crystalloid forms on papayas are tubular and there is a positive response to temperature; the higher the temperature, the larger and more frequent the tubular crystalloids.

Low-Damage Massive Hydraulic Fracturing Technique in Tight Gas Formations With High Temperature and High Pressure

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper SPE 114303, "The Study and Application of Low-Damage and Massive Hydraulic-Fracturing Technique in Tight Gas Formations With High Temperature and High Pressure," by Lei Qun, Tingxue Jiang, SPE, Xu Yun, SPE, Yunhong Ding, SPE, Yongjun Lu, SPE, Cai Bo, Yuhua Shu, and Yaoyao Duan, PetroChina, prepared for the 2008 SPE Gas Technology Symposium, Calgary, 16-19 June. The paper has not been peer reviewed. Many tight gas formations in the southern Songliao basin in northeast China have high pressure/high temperature (HP/HT) conditions. However, it is very difficult to conduct successful fracturing treatments in the deep wells (deeper than 4200 m) with temperatures greater than 150°C and pressures greater than 60 MPa. A study was conducted to overcome these difficulties. Introduction There are many difficulties related to hydraulic-fracturing design and treatment in tight HP/HT gas formations, including formation fines, initiation and propagation of the hydraulic fracture, selection of a low-damage and highly viscous elastic fluid, selection of a high-strength proppant that is transported easily, and that many fracturing-treatment failures result from early tip screenout. The commonly used fracturing technique included ordinary guar fluid with relative high polymer concentration and high residue content; medium proppant size of 20/40 mesh; a common proppant-pumping schedule such as 180, 360, 540, 720, and then 900 kg/m3; and longer shut-in time (at least 2 hours). Consequently, the post-fracturing production rate was disappointing. Formation Evaluation For fracturing design, it is critical to understand the targeted formation in both macro- and microperspectives. Macroparameters include sediment, perforation data, permeability, porosity, thickness, saturations, rock mechanics, in-situ stress magnitude and azimuth, and the distribution of these parameters. Macroparameters may be available from drilling, logging, and well-testing data. Microparameters include mineral components and sensitivities of micropore structure such as pore and throat diameter, along with natural fissures and their distribution. Microparameters may be obtained from test data of core samples in the laboratory. In fracturing-stimulation design, macroparameters may be used to optimize fracture length, conductivity, and proppant selection, while microparameters are used mainly to choose low-damage fluid additives and determine their mixture, optimize use of 100-mesh proppant or any other solids-loss reducers in case of natural fissures, and optimize the time and velocity of flowing back fracturing fluid in case of stress and velocity sensitivity.

Characterisation of sunflower root colonisation by Phoma macdonaldii

Phoma macdonaldii, the causal agent of black stem disease of sunflower (Helianthus annuus), also attacks roots and collars of the plants, resulting in early death. Totally resistant lines do not exist for infection of the aerial parts, but tolerant lines have been characterised. This paper presents a study on colonisation of a partially resistant and a susceptible sunflower line by P. macdonaldii. The fungus was transformed with a constitutively expressed reporter gene encoding the jellyfish green fluorescent protein via Agrobacterium tumefaciens, and colonisation of sunflower roots by this transformed strain was studied by various microscopy techniques including confocal and scanning electron microscopy. The results show that penetration of the fungus into the root occurred through natural fissures or through the epidermis and was similar in both lines. In contrast, the colonisation rate of the stele was reduced in the partially resistant line, and the morphology of the fungal hyphae was also affected. The effect on hyphal morphology was strongest in the stele, indicating a localised production of defence compounds in this line.

Regional Variation in Non-Timber Forest Product Harvest Strategies, Trade, and Ecological Impacts: the Case of Black Dammar (Canarium strictum Roxb.) Use and Conservation in the Nilgiri Biosphere Reserve, India

Varghese, A., and T. Ticktin. 2008. Regional variation in non-timber forest product harvest strategies, trade, and ecological impacts: the case of black dammar (Canarium strictum roxb.) use and conservation in the Nilgiri Biosphere Reserve, India. Ecology and Society 13(2): 11. https://doi.org/10.5751/ES-02555-130211

Figurations de l’amas stellaire des Pléiades sur deux roches gravées de la région du Mont Bego Z IX. GII. R 4 et Z IX. GIII. R 6

Two engraved rocks are situated 140 m from each other at an altitude of about 2250 m. One of them is called “female dancer”, and the other, “the Pleiads”, and both show a group of seven small pitted areas, of which one is smaller than the others and ‘ identified as the “Pleiads stellar cluster”, often depicted or mentioned during Antiquity and also throughout various historical periods. On each of these rocks, a large halberd, whose handle is oriented east-west, was traced along a natural fissure in the rock and engraved in the center of the composition. The “Pleiads stellar cluster” is represented on each of the two rocks beside the halberd : although situated to the west above the halberd blade on the “female dancer” rock, it is placed to the south and to the left of the halberd handle on “the Pleiads” rock. This difference may mark two distinct calendar data. The position of the different figures in the compositions illustrated on these two rocks, in particular inversions in the representation of some of them may indicate two distinct periods of the agricultural yearly cycle: on the rock called “female dancer”, the “heliacal raise” at summer's end, marking the beginning of the harvest and, on the rock called “the Pleiads”, the “heliacal setting”, just before winter, after the end of the harvest, when the rains soaks the ground and it is time to plow.

The influence of structure on the behaviour of London Clay

An intensive investigation is described into the London Clay units from Heathrow Terminal 5. Intrinsic properties and composition were established, and relating the behaviour of intact and reconstituted samples allowed the effects of the clay's natural structure to be identified at all depths. Structure varied between units, but some general features emerged that have not been seen in other stiff clays. In particular, intact samples follow paths under isotropic or K0 compression that fail to provide well-defined gross yield points, or converge with the unit's intrinsic compression lines. Structure contributes to the enhanced shear strength of intact unfissured clay and affects the initial stiffness relationships. Some identifiable features of the intact units’ fabric correlated directly with their behaviour. Natural fissures within the clay, the most important mesofabric feature, had an important impact on shear strength and led to an unusual pattern of directional dependence, and particle orientation trends identified by scanning electron microscopy governed the strong elastic stiffness anisotropy. The potential for destructuration through swelling to low effective stresses was also studied and found significant for subsequent volumetric compression behaviour, but not for shearing. Hight et al. synthesise the data from this and companion papers presented by the authors, and discuss the practical consequences of the results obtained.

Penetration ability and microleakage of a fissure sealant applied on artificial and natural enamel fissure caries

This study investigated the sealing ability of a current available unfilled fissure sealant applied over sound (n=80), artificially created (n=80) and naturally carious fissures (n=80) under different humidity conditions (90+/-2 and 45+/-2% relative humidity) and etching times (40 and 60s). All samples were submitted to 5000 thermal cycles and examined by light microscopy after sectioning. Microleakage, penetration ability, fissure type, fissure entrance angle, sealant occlusal length, caries location and caries depth were assessed. The significantly longer sealant occlusal length and larger entrance angle exhibited by shallow fissures, contributed to their higher microleakage and smaller amounts of unfilled areas compared to deep fissures. Sealant microleakage was significantly influenced by the condition of the enamel (sound, artificial and natural caries) and the caries location in the fissures, but not by enamel caries depth (D1 and D2), etching time, or humidity condition. Natural caries exhibited significantly higher microleakage than sound or artificially created carious fissures. Based on the results of this study, it can be concluded that location of caries in the fissure rather than its depth should be taken into account when applying a fissure sealant. When the borders of the fissure sealant are on carious enamel, a significantly higher microleakage must be expected. The artificial caries model was not a suitable method to assess the behavior of natural fissure caries.

Continuous time random walks for analyzing the transport of a passive tracer in a single fissure

The selection of the correct model for describing contaminant transport in fractured media remains a challenging problem in subsurface hydrology. In this work, the experimental data corresponding to nonsorbing tracer runs in natural fissures of Moreno et al. (1985) are analyzed. The advection dispersion equation (ADE) model yields a poor fit in the late time regions of the experimental breakthrough curves denoting the existence of “anomalous” or “non‐Fickian” transport. Continuous time random walks (CTRW) are proposed for describing this kind of transport using two of the most studied forms for the transition rate probability: the asymptotic and truncated power law models. The CTRW approach produces better fits to the experimental data than the ADE model. In all the simulations a moderately dispersive transport was found which is interpreted as being as a result of the effects of the small‐ and intermediate‐scale heterogeneities.

Self-adjusted elastic action and its CBM pool-forming effect of the high rank coal reservoir

The coal reservoir is a kind of geologic body with considerable elasticity, and its response to stress is more sensitive than the routine ones. In the pool-forming process of the coalbed methane, (CBM) the action of many external geodynamic factors in the coal reservoir is represented by the ability of CBM’s diffusion and migration in the coal reservoir. Therefore, the occurrence of the natural fissures in the coal reservoir becomes a key that determines whether the CBM pool can be formed or not. Based on the principle, the authors have designed a comprehensive method of physical modeling to study the elasticity of the coal matrix block with different coal ranks in the light of the solid to fluid coupling, have established the model of the volume deformation (selfadjusted elastic effect) of the coal reservoir under the condition of the effective stress-adsorption/desorption, and have obtained a correct understanding of the law of the elastic deformation. Afterwards, a new viewpoint, named as the self-closing elastic effect for forming the CBM pool in the high rank reservoir, is put forward, providing an initial point and a scientific basis for a further investigation into its dynamic factors, possible mechanism and role in the CBM energy-balancing system.

English

Numerous abandoned gas wells drilled during the late 1800's through the mid 1900's in the Clarion River watershed are acting as conduits for the artesian flow of iron-polluted waters to the surface. These shallow wells are located near surface mines, which were mined during the 1940's through the 1970's and had little if any surface reclamation. The geochemistry of the artesian well discharges suggests that they are originating in the open pit mine spoils located at the headwaters of tributaries to the Clarion River. Surface water filters through exposed mine spoils and weathers pyrite (FeS2) producing water with low pH and elevated sulfate, acidity, and Al. The polluted water flows down through the fractured pit pavement into lower stratigraphic units and then flows laterally and down the synclinal structures through moderate to high productivity aquifers. The contaminated groundwater artesians to the surface through natural fissures or abandoned gas wells. Samples collected from twenty artesian discharges had pH values of 4.7 to 6.1, alkalinity concentrations of 26 to 110 mg/L as CaCO3, sulfate concentrations of 33 to 1254 mg/L, and iron concentrations of 10 to 215 mg/L. Aluminum concentrations were less than 1 mg/L. Eighteen of the twenty samples were strongly acidic due to the presence of high concentrations of Fe. The change in chemistry between the surface mines and the artesian discharges is attributed to reaction with iron carbonate minerals such as siderite. The effect of plugging efforts on eight artesian flowing gas wells was monitored. Four wells were successfully plugged. Flow shifted rapidly from plugged wells to unplugged wells. The rapid response suggests that the wells drain a shallow contaminated aquifer. Because of the flow transfer, the plugging program had minimal remedial effect on the targeted watershed.

Propagation of In Situ Horizontal Fractures in Shale Due to Steam Injection

Abstract Thermal recovery processes, such as cyclic steam stimulation and steam assisted gravity drainage, involve the injection of large volumes of steam into oil sand formations. Dilatation of oil sand formations due to steam injection induces stresses and deformations in the shale overburden. Natural horizontal fissures or extensive fractures with no tensile and cohesive strength are commonly found in the shale formation. New fractures will be initiated at these in situ horizontal fracture tips if the stresses and deformation induced by the steam injection are excessive. Reactivation and propagation of these in situ fractures in the shale formation could not only cause casing impairment problems, but could also cause an environmental hazard. This paper presents an analytical model to investigate the propensity for fracture propagation in shale due to steam injection under tensile (mode I) and shear (model II) fracturing. Practical numerical examples are presented along with a risk assessment and implications. Introduction Heavy oil and bitumen are major energy resources in Canada, and have become a major focus for the oil and gas industry. The heavy oil deposits of Canada contain 30% of the world's recoverable oil(1). The challenge in developing this resource is the difficulty in recovering these highly viscous substances. Steam stimulation is one of the viable thermal recovery methods to extract bitumen from the oil sand ores buried in deep overburden. In this steam-based recovery method, large volumes of steam at high temperatures and pressures (300 °C and 10 MPa) are injected into the oil sand formation at depths of 450 - 500 m through wells in rows(2, 3). Steam injection produces stress and thermal dilatation of oil sand. Because oil sands are dense uncemented sands, the resulting deformation induced during the recovery processes could be excessive and detrimental to surface and subsurface facilities(4). Surface heave of up to 20 cm has been recorded(5). Overlying the oil sand formation are low-permeability clay shales forming an impermeable barrier against the migration of fluid. Natural horizontal fissures or fractures are commonly found in these shale formations(6, 7). These fractures have been formed or been subjected to a large shearing process during glaciation. Therefore, there is no tensile strength or small residual strength remaining along these fractures. One of the geomechanical-related problems is the question of whether these pre-existing fractures will propagate under steam injection. Intercepting these fractures with subsurface well casings could lead to casing impairment or rupture (see Figure 1). The main objective of the present paper is to evaluate the potential of initiation and propagation of in situ fractures in shales induced by cyclic steam stimulation in an oil sand reservoir using a simple analytical model(8). This model analytically considers the stress intensity factors at a crack parallel to the free surface of a half-plane under the action of a centre of dilatation. It is proposed that the introduction of steam in the oil sand formation can be modelled by introducing a centre of dilatation (dipole) in a two-dimensional homogenous isotropic elastic half-plane (see Figure 1).

Geochemistry, Hydrogeology, and effects from the plugging of Artesian Flows of Acid mine drainage: Clarion River Watershed, Northwestern Pennsylvania

Numerous abandoned gas wells drilled during the late 1800's through the mid 1900's in the Clarion River watershed are acting as conduits for the artesian flow of iron-polluted waters to the surface. These shallow wells are located near surface mines, which were mined during the 1940's through the 1970's and had little if any surface reclamation. The geochemistry of the artesian well discharges suggests that they are originating in the open pit mine spoils located at the headwaters of tributaries to the Clarion River. Surface water filters through exposed mine spoils and weathers pyrite (FeS2) producing water with low pH and elevated sulfate, acidity, and Al. The polluted water flows down through the fractured pit pavement into lower stratigraphic units and then flows laterally and down the synclinal structures through moderate to high productivity aquifers. The contaminated groundwater artesians to the surface through natural fissures or abandoned gas wells. Samples collected from twenty artesian discharges had pH values of 4.7 to 6.1, alkalinity concentrations of 26 to 110 mg/L as CaCO3, sulfate concentrations of 33 to 1254 mg/L, and iron concentrations of 10 to 215 mg/L. Aluminum concentrations were less than 1 mg/L. Eighteen of the twenty samples were strongly acidic due to the presence of high concentrations of Fe. The change in chemistry between the surface mines and the artesian discharges is attributed to reaction with iron carbonate minerals such as siderite. The effect of plugging efforts on eight artesian flowing gas wells was monitored. Four wells were successfully plugged. Flow shifted rapidly from plugged wells to unplugged wells. The rapid response suggests that the wells drain a shallow contaminated aquifer. Because of the flow transfer, the plugging program had minimal remedial effect on the targeted watershed.

Re‐equilibration of fluid inclusions in diagenetic‐anchizonal rocks of the Ciñera‐Matallana coal basin (NW Spain)

AbstractThermally re‐equilibrated fluid inclusions are reported in natural fissure quartz (qtz1) from polymineralic veins in the diagenetic‐anchizonal clastic sedimentary rocks of the Ciñera‐Matallana coal basin (Variscan, NW Spain). Euhedral quartz formed during early fissure opening from an immiscible fluid mixture composed of a low salinity aqueous solution and a CH4‐rich vapour phase, at temperatures of about 110–120°C and pressures ranging from 15 to 56 MPa. Five textural types of re‐equilibration are recognised in progressive order of inclusion modification: scalloped, hairy, annular‐ring shaped, haloes and decrepitation clusters. These textures resulted from a combination of brittle fracturing and dissolution and re‐precipitation of quartz, with preferential loss of water. The thermal peak was short‐lived, but was high enough to induce extensive decrepitation of fluid inclusions in vein quartz throughout the entire basin. Enhanced temperatures can be related to the intrusion of diorites in the basin. Careful analysis of textural features in fluid inclusions from diagenetic and very low‐grade metamorphism environments constitutes a useful tool for recording basin thermal history.

Thrown Away Like Rubbish - Disposal of the Dead in Ancient Greece

<!--[if gte mso 9]><xml> <w:WordDocument> <w:View>Normal</w:View> <w:Zoom>0</w:Zoom> <w:PunctuationKerning /> <w:DisplayHorizontalDrawingGridEvery>0</w:DisplayHorizontalDrawingGridEvery> <w:DisplayVerticalDrawingGridEvery>2</w:DisplayVerticalDrawingGridEvery> <w:ValidateAgainstSchemas /> <w:SaveIfXMLInvalid>false</w:SaveIfXMLInvalid> <w:IgnoreMixedContent>false</w:IgnoreMixedContent> <w:AlwaysShowPlaceholderText>false</w:AlwaysShowPlaceholderText> <w:Compatibility> <w:SpaceForUL /> <w:BalanceSingleByteDoubleByteWidth /> <w:DoNotLeaveBackslashAlone /> <w:ULTrailSpace /> <w:DoNotExpandShiftReturn /> <w:AdjustLineHeightInTable /> <w:BreakWrappedTables /> <w:SnapToGridInCell /> <w:WrapTextWithPunct /> <w:UseAsianBreakRules /> <w:DontGrowAutofit /> <w:UseFELayout /> </w:Compatibility> <w:BrowserLevel>MicrosoftInternetExplorer4</w:BrowserLevel> </w:WordDocument> </xml><![endif]--><!--[if gte mso 9]><xml> <w:LatentStyles DefLockedState="false" LatentStyleCount="156"> </w:LatentStyles> </xml><![endif]--> <!-- /* Font Definitions */ @font-face {font-family:PMingLiU; panose-1:2 1 6 1 0 1 1 1 1 1; mso-font-alt:"Arial Unicode MS"; mso-font-charset:136; mso-generic-font-family:auto; mso-font-format:other; mso-font-pitch:variable; mso-font-signature:1 134742016 16 0 1048576 0;} @font-face {font-family:TimesNewRoman; panose-1:0 0 0 0 0 0 0 0 0 0; mso-font-charset:0; mso-generic-font-family:auto; mso-font-format:other; mso-font-pitch:auto; mso-font-signature:3 0 0 0 1 0;} @font-face {font-family:"\@PMingLiU"; panose-1:0 0 0 0 0 0 0 0 0 0; mso-font-charset:136; mso-generic-font-family:auto; mso-font-format:other; mso-font-pitch:variable; mso-font-signature:1 134742016 16 0 1048576 0;} @font-face {font-family:TimesNewRomanPS-ItalicMT; panose-1:0 0 0 0 0 0 0 0 0 0; mso-font-charset:0; mso-generic-font-family:roman; mso-font-format:other; mso-font-pitch:auto; mso-font-signature:3 0 0 0 1 0;} /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman"; mso-fareast-font-family:PMingLiU; mso-ansi-language:EN-GB; mso-fareast-language:EN-US;} /* Page Definitions */ @page {mso-page-border-surround-header:no; mso-page-border-surround-footer:no;} @page Section1 {size:612.0pt 792.0pt; margin:72.0pt 90.0pt 72.0pt 90.0pt; mso-header-margin:36.0pt; mso-footer-margin:36.0pt; mso-paper-source:0;} div.Section1 {page:Section1;} --> <!--[if gte mso 10]> <style> /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman"; mso-ansi-language:#0400; mso-fareast-language:#0400; mso-bidi-language:#0400;} </style> <![endif]--> <p class="MsoNormal"><span style="font-size: 8pt; font-family: TimesNewRoman;" lang="EN-US">In this article, the literary and archaeological evidence for burial practices that can be associated with the English expression ‘to be disposed of like rubbish’ are discussed. These disposal methods (</span><em><span style="font-size: 8pt; font-family: TimesNewRomanPS-ItalicMT;" lang="EN-US">átaphon rhíptesthai</span></em><span style="font-size: 8pt; font-family: TimesNewRoman;" lang="EN-US">) include the exposure of corpses to carrion animals, to the elements, as well as the disposal of corpses into the sea, pits or natural fissures without burial rites. They also include cases in which graves were dug up in order to throw their contents out. Here, the Greek expressions for the English phrase ‘to be thrown away like rubbish’ are explored, as well as its relation to Morris’ (1987) influential concept of the ‘non-formal burial’. The analysis of the symbolism of various disposal methods has been based on both literary and archaeological sources. Also addressed are issues such as the intersection of the exclusion from full and proper burial procedures with social status and social groups. Lastly, the dangers for the living and the dead associated with casually disposed of human remains are briefly tackled, including the transformation of the souls of the deceased into spirits and their loss of human-ness.</span><span lang="EN-GB"></span>

Modeling transport in a single crack by the dual-porosity concept with a boundary layer at the interface

A model for contaminant transport along a discrete fracture in a porous rock matrix is developed and solved analytically. The focus here is on the dynamics of solute exchange between the matrix and a single crack and its effect on solute transport within the crack and the chemical distribution with time at any depth. A laminar boundary layer of near stagnant fluid exists at the interface between the fracture and the matrix through which a rate-limited mass transfer takes place. The flow and the dissolved chemical concentration normal to the flow direction are essentially uniform in the crack except for the boundary layer. Chemical concentration in the immobile porosity varies with time and space in the lateral direction. The driving force for the dissolved chemical exchange through this layer is the difference between the fluid concentration in the crack and the matrix concentration at the interface, both varying with time and space. The dissolved chemical concentration in the crack is modeled by the kinematic wave equation and the diffusion equation is used to model the dissolved chemical transport in the matrix. Exact analytical solutions for the matrix and crack equations are obtained in the Laplace domain and an approximate solution in the time domain for the case where ζε/ s is sufficiently small. ζ is the dimensionless distance along the crack, ε is a dimensionless parameter obtained when dimensionless variables were introduced into the differential equations and boundary conditions, and s is the Laplace transformation variable. The deviations between the approximate and exact solutions for different values of ε and other variables, calculated in the Laplace domain, enable us to evaluate the cases where the approximate solution can be satisfactorily used. The solution obtained by the current model was verified by its comparison with BTCs measured by Neretnieks et al. (Neretnieks, I., Eriksen, T., Tahtinen, P., 1982. Tracer movement in a single fissure in granitic rock: some experimental results and their interpretation. Water Resour. Res. 18, 4, pp. 849–858) for a granite core with a natural fissure parallel to its axis. A very good agreement was obtained between the measured and predicted BTCs. The physical meaning of the fitted parameters has been discussed. The relative role of the two rate-limited processes, namely film transfer and diffusion in the stagnant matrix solute, on the overall chemical exchange and BTC shape was analyzed by the non dimensional version of the mass balance equations. The displacement duration has been divided into two stages. Soon after its initiation, the chemical transfer through the stagnant film controls the chemical exchange between the preferential path and matrix. The duration of this stage depends on different properties of the system. Subsequently, the matrix–diffusion controls the chemical exchange between the two domains and the model can then be simplified by replacing the rate-limited transfer by a local equilibrium. For cases for which the current study is dealing with, the preferential flow is very fast and the rate-limited transfer through the stagnant film dominates the BTC shape.

Design, Execution, and Evaluation of Acid Treatments of Naturally Fractured Carbonate, Oil Reservoirs of the North Sea

SummaryThis paper discusses damage removal in naturally fractured carbonate, oil reservoirs of the central North Sea, located in the vicinity of salt domes. The reservoir rock is the well-known Tor chalk, the mechanical properties of which have been greatly modified by the proximity of diapirs. The matrix rock is much harder (similar to a limestone) and extensively fissured. Wells drilled through these reservoirs suffer from very severe damage as a result of the invasion of the natural fractures by large amounts of drilling mud. Productivity is restored by high-rate damage-removal treatments alternating stages of crosslinked gel, customized acid formulations, and ball sealers. Pre- and postjob well performances demonstrate huge productivity-index increases as a result of the cleanup of the natural fissures. This paper emphasizes mud-loss survey during drilling and perforation strategies; candidate selection, i.e., pre- and postjob productivity based on both rock (matrix and fissures) and damage properties; treatment execution (as per actual North Sea jobs); and treatment evaluation and diversion efficiency.

Xylem colonization of the legume Sesbania rostrata by Azorhizobium caulinodans

A novel pathway of invasion of the legume Sesbania rostrata by Azorhizobium caulinodans is described that involves colonization of the root xylem, possibly following entry into the natural fissures created during emergence of lateral roots. Azorhizobia were detected microscopically, and their presence confirmed by the expression of a lacZ reporter gene. We have shown that rhizobial Nod factors are not required for either xylem colonization or for crack-entry of lateral roots. We discuss the extent to which this discovery of xylem colonization by azorhizobia is likely to improve our understanding of both symbiosis and of pathogenicity in plant–bacterial interactions.

Discussion on ‘The Chalk as a karstic aquifer: evidence from a tracer test at Stanford Dingley, Berkshire, UK’

M. Price writes: Banks et al. (1995) address the nature of the permeability of parts of the Chalk aquifer, provide useful data from a tracer test, and draw attention to the potential dangers of disposing of agricultural and road run-off to swallow holes. The paper includes a calculation of fissure conductivity and aperture from the results of the tracer test. In this it has to be emphasized that the calculations relate to Darcian flow in an equivalent smooth, plane, parallel-plate opening, not the more likely turbulent flow in a natural fissure. The true average aperture of the fissure is therefore likely to be significantly greater than that calculated (Price 1987, 1996). The situation described at Stanford Dingely is one where drainage originating from impermeable Tertiary strata flows onto the Chalk and sinks into the aquifer. The majority of active Chalk sinks appear to be of this type; the drainage sinking into them originates as run-off from other strata. Rain falling anywhere on the outcrop of the Chalk is normally able to infiltrate, so water flowing across the Chalk outcrop is almost invariably allogenic drainage or water that has infiltrated the Chalk and emerged as baseflow. Drainage to sinks is therefore a minor component of recharge to the Chalk. The tracer test undertaken into at Stanford Dingley involved introducing tracer into a known point of entry in the aquifer, and observing its arrival at a known point of emergence. Such tests almost inevitably measure the speed of groundwater movement along a