Large Core Samples Research Articles

Heating enhanced methane desorption of large coal cores at various methane pressures and confining pressures

ABSTRACT Heating coal seams or injecting heat flow into coal seams is a potential enhanced coalbed methane recovery technique. However, methane desorption characteristics of coal seams under combined effect of confining pressure, methane pressure, and applied heat is complex. In the present work, we investigated the combined effect on methane adsorption on different types of coal. Through comparing the desorption capacity and its influencing factors of two samples (bituminous coal and anthracite coal) at different combination of methane equilibrium pressure (1 MPa, 3 MPa, and 5 MPa) and confining pressure (8 MPa, 10 MPa, and 12 MPa) under heating, we found that the cumulative desorption capacity of methane is positively correlated with gas pressure and negatively correlated with confining pressure. Under the same conditions, the cumulative desorption capacity of anthracite is significantly larger than that of bituminous coal. Methane desorption amount under heating is higher than that without heating, while methane desorption amount of large core sample is smaller than that of coal powder. These results indicate that raising the coal seam temperature while capturing methane is a promising method for obtaining higher coalbed methane recovery rates, reducing greenhouse gas emissions, and improving mining safety.

Transforaminal Endoscopic Approach for Large-Sample Tumor Biopsy using Beveled Working Channel for Core Technique: A Technical Note

Identifying the histopathological diagnosis of a spinal tumor is the necessary step prior to pursuing subsequent treatment. Both minimally invasive and open spinal procedures have been described as useful methods of obtaining tumor tissue for diagnosis but differ by their limitations. Minimally invasive techniques, such as computed tomography-guided biopsies, can expose the patient to radiation, and the tissue obtained may be nondiagnostic. Tubular and open procedures require collateral soft-tissue damage and may require bony removal leading to iatrogenic injury. Endoscopic approaches to the spine can be employed to avoid treatment delay in diagnosis, decrease length of stay, and provide adequate tissue for diagnosis. We describe the surgical planning, tumor localization, and transforaminal endoscopic approach for tissue diagnosis of a lumbar spinal mass in a patient with a known history of Hodgkin lymphoma and non-Hodgkin lymphoma after a nondiagnostic computed tomography- guided biopsy. Final histopathological diagnosis of the lumbar spinal mass was consistent with large B-cell non-Hodgkin lymphoma. We demonstrate the application of an endoscopic transforaminal approach in spine oncology. We also describe our technique on how we use a beveled working channel to obtain a large tissue core sample for definitive diagnosis.

Multiscale modeling algorithm for core images.

Computed tomography (CT) images of large core samples acquired by imaging equipment are insufficiently clear and ineffectively describe the tiny pore structure; conversely, images of small core samples are insufficiently globally representative. To alleviate these challenges, the idea of a super-resolution reconstruction algorithm is combined with that of a three-dimensional core reconstruction algorithm, and a multiscale core CT image fusion reconstruction algorithm is proposed. To obtain sufficient image quality with high resolution, a large-scale core image is used to provide global feature information as well as information regarding the basic morphological structure of a large-scale pore and particle. Then the texture pattern and the tiny pore distribution information of a small-scale core image is used to refine the coarse large-scale core image. A blind image quality assessment is utilized to estimate the degradation model of core images at different scales. A multilevel pattern mapping dictionary containing local binary patterns is designed to speed up the pattern matching procedure, and an adaptive weighted reconstruction algorithm is designed to reduce the blockiness. With our method, images of the same core at different scales were successfully fused. The proposed algorithm is extensively tested on microstructures of different rock samples; all cases of the reconstructed results and those of the actual sample were found to be in good agreement with each other. The final reconstructed image contains both large-scale and small-scale information that can provide a better understanding of the core samples and inform the accurate calculation of parameters.

Reconstruction of in-situ porosity and porewater compositions of low-permeability crystalline rocks: Magnitude of artefacts induced by drilling and sample recovery

Geological site characterisation programmes typically rely on drill cores for direct information on subsurface rocks. However, porosity, transport properties and porewater composition measured on drill cores can deviate from in-situ values due to two main artefacts caused by drilling and sample recovery: (1) mechanical disruption that increases porosity and (2) contamination of the porewater by drilling fluid. We investigated the effect and magnitude of these perturbations on large drill core samples (12–20cm long, 5cm diameter) of high-grade, granitic gneisses obtained from 350 to 600m depth in a borehole on Olkiluoto Island (SW Finland). The drilling fluid was traced with sodium–iodide. By combining out-diffusion experiments, gravimetry, UV-microscopy and iodide mass balance calculations, we successfully quantified the magnitudes of the artefacts: 2–6% increase in porosity relative to the bulk connected porosity and 0.9 to 8.9vol.% contamination by drilling fluid.The spatial distribution of the drilling-induced perturbations was revealed by numerical simulations of 2D diffusion matched to the experimental data. This showed that the rims of the samples have a mechanically disrupted zone 0.04 to 0.22cm wide, characterised by faster transport properties compared to the undisturbed centre (1.8 to 7.7 times higher pore diffusion coefficient). Chemical contamination was shown to affect an even wider zone in all samples, ranging from 0.15 to 0.60cm, in which iodide enrichment was up to 180mg/kgwater, compared to 0.5mg/kgwater in the uncontaminated centre.For all samples in the present case study, it turned out that the magnitude of the artefacts caused by drilling and sample recovery is so small that no correction is required for their effects. Therefore, the standard laboratory measurements of porosity, transport properties and porewater composition can be taken as valid in-situ estimates. However, it is clear that the magnitudes strongly depend on site- and drilling-specific factors and therefore our results cannot be transferred simply to other locations. We recommend the approach presented in this study as a route to obtain reliable values in future drilling campaigns aimed at characterising in-situ bedrock properties.

Ecosite-based predictive modeling of black spruce (Picea mariana) wood quality attributes in boreal Ontario

Enhanced forest resources inventory systems delineate and define polygons based on fundamental ecological units such as ecosites, which are standard combinations of vegetation and substrate types. Our study objective was to model wood quality characteristics of individual black spruce (Picea mariana (Mill.) B.S.P.) trees across a representative boreal forest landscape in northeastern Ontario, Canada, based on relationships to ecosite and other stand-level variables. A total of 127 large (12 mm) increment core samples were extracted at breast height from dominant or co-dominant black spruce trees in forest stands representing a gradient from dry sandy to wet mineral and organic ecosites. Sample cores were prepared, processed, and analyzed using standard SilviScan protocols. Hierarchical classification models were then fitted using Random Forests to predict density and latewood percentage for black spruce stems at a reference age of 50 years. These models each explained over 32% of variance, with estimated root mean squared errors of 40.4 kg·m−3 and 5.6% for density and latewood percentage, respectively. Among tree-, site-, and stand-level covariates, ecosite group was the most important predictive variable. Knowledge of ecosite – wood quality relationships could support efficient planning for black spruce management by including an indication of potential use as a modeled variable in a forest inventory system.

Scotia Arc deep-water bivalves: composition, distribution and relationship to the Antarctic shelf fauna

Abstract Agassiz trawl, epibenthic sledge and large box core samples were made in the Scotia and northern Weddell Seas during the 2002 ANDEEP expeditions with R.V. Polarstern at 21 locations (774–6348 m depth). The deep-water bivalve fauna sampled was species rich; in total 40 species of bivalves belonging to 17 families were found. At least seven of these species are new to science. Per location species richness varied from 5 to 15 species. Kelliella sirenkoi was the most common and abundant species, occurring at 17 locations (1121–6348 m), followed by Genaxius sp.1 occurring at 12 locations. The epibenthic sledge hauls were characterised by low abundances, varying from 1 to 68 individuals 1000 m−2 in depths greater than 1000 m. In comparison with the shelf fauna of the Scotia Arc, the deep-water bivalve community showed similar species richness. This indicates that there is no diversity cline with depth in Antarctic bivalves, but it does provide evidence for underestimated species richness in deep water because of lack of sampling.

Fracture toughness measurements on igneous rocks using a high-pressure, high-temperature rock fracture mechanics cell

A sound knowledge of mechanical properties of rocks at high temperatures and pressures is essential for modelling volcanological problems such as fracture of lava flows and dike emplacement. In particular, fracture toughness is a scale-invariant material property of a rock that describes its resistance to tensile failure. A new fracture mechanics apparatus has been constructed enabling fracture toughness measurements on large (60 mm diameter) rock core samples at temperatures up to 750°C and pressures up to 50 MPa. We present a full description of this apparatus and, by plotting fracture resistance as a function of crack length, show that the size of the samples is sufficient for reliable fracture toughness measurements. A series of tests on Icelandic, Vesuvian and Etnean basalts at temperatures from 30 to 600°C and confining pressures up to 30 MPa gave fracture toughness values between 1.4 and 3.8 MPa m 1/2. The Icelandic basalt is the strongest material and the Etnean material sampled from the surface crust of a lava flow the weakest. Increasing temperature does not greatly affect the fracture toughness of the Etnean or Vesuvian material but the Icelandic samples showed a marked increase in toughness at around 150°C, followed by a return to ambient toughness levels. This material also became tougher under moderate confining pressure but the other two materials showed little change in toughness. We describe in terms of fracture mechanics probable causes for the changes in fracture toughness and compare our experimental results with values obtained from dike propagation modelling found in the literature.

Measurement of Acoustical and Mechanical Properties of Porous Road Surfaces and Tire and Road Noise

The absorption coefficients of dense and porous road surfaces have been measured in the laboratory with core samples with 4- and 6-in.-diameter impedance tubes and with an impedance tube mounted vertically in situ on the pavement surfaces. The 6-in. tube allows the absorption of a large core sample surface to be determined, but only up to a frequency of about 1,250 Hz. The 4-in. tube allows the absorption coefficient to be determined up to a frequency of about 1,950 Hz. The two different-diameter impedance tubes also were mounted vertically on some of the same pavement types, and the absorption coefficients of these pavement types were measured in this way too. The measured peak sound absorption coefficients of the fine- and coarse-mix aggregate porous surfaces suggest that the first peak frequency and peak absorption coefficient magnitude are only slightly different for the two types of porous surfaces. Because the fine-mix aggregate porous surface is smoother, it is preferred because it should result in less tire-tread impact noise and thus lower overall tire noise than the coarse aggregate surface. A porous surface between 1.5 and 2.0 in. thick is recommended for the type of porous surface examined, if a peak absorption frequency of about 1,000 Hz is desired, so as to be most effective at reducing the Interstate highway noise of automobiles.

A non-destructive sampling method for dendrochronology in hardwood species

ABSTRACT Core sampling in indigenous hardwood species is not a common practise. A field method LOUS developed to obtain a large enough sample without permanently damaging the trees. A Milwaukee Dymo 2,3 k W electric drill fitted with a 2-speed gearbox and powered by a generator was used. A core drill bit (100 mm x 350 mm) fitted with tungsten tips was designed to fit the electric drill. Core samples of mature trees of unknown age were collected according to height and diameter classes in the Kalahari Gemsbok National Park. This nondestructive method was found to be suitable for collecting large core samples of hardwood species.

X-ray computed tomography to quantify tree rooting spatial distributions

Poor root development due to constraining soil conditions could be an important factor influencing health of urban trees. Therefore, there is a need for efficient techniques to analyze the spatial distribution of tree roots. An analytical procedure for describing tree rooting patterns from X-ray computed tomography (CT) data is described and illustrated. Large irregularly shaped specimens of undisturbed sandy soil were sampled from various positions around the base of trees using field impregnation with epoxy resin, to stabilize the cohesionless soil. Cores approximately 200 mm in diameter by 500 mm in height were extracted from these specimens. These large core samples were scanned with a medical X-ray CT device, and contiguous images of soil slices (2 mm thick) were thus produced. X-ray CT images are regarded as regularly-spaced sections through the soil although they are not actual 2D sections but matrices of voxels ∼0.5 mm×0.5 mm×2 mm. The images were used to generate the equivalent of horizontal root contact maps from which three-dimensional objects, assumed to be roots, were reconstructed. The resulting connected objects were used to derive indices of the spatial organization of roots, namely: root length distribution, root length density, root growth angle distribution, root spatial distribution, and branching intensity. The successive steps of the method, from sampling to generation of indices of tree root organization, are illustrated through a case study examining rooting patterns of valuable urban trees.

Carbon and peat accumulation over the past 1200 years in a landscape with discontinuous permafrost, northwestern Canada

Apparent recent carbon and peat accumulation rates over the past 1200 years were measured in five peat landforms in the discontinuous permafrost zone near Fort Simpson, Northwest Territories, Canada. The White River volcanic ash layer was used as a chronostratigraphic horizon to ensure a consistent time span of peat deposition among peat cores and to allow a large core sample size (n = 20 cores in each landform) without the expense of radiocarbon dating. Apparent recent carbon accumulation rates were not significantly different (p>0.05) among rich fen (13.58 ± 1.07 g C m−2yr−1), peat plateau (13.31 ± 2.20 g C m−2yr−1) and collapse fen (13.54 ± 1.50 g C m−2yr−1). Poor fen and ombrotrophic bog accumulation rates were 20.34 ± 2.86 and 21.81 ± 3.25 g C m−2yr−1, respectively, and were not significantly different from each other. Variation within the poor fen and ombrotrophic bog cores is attributed to microtopography, with hollows accumulating carbon at significantly greater rates than hummocks. Vertical peat accumulation rates vary significantly in the poor fen, with hummocks showing a greater annual vertical accumulation rate than hollows. Vertical peat accumulation rates ranged from 0.282 ± 0.052 mm yr−1in the peat plateau to 0.563 ± 0.070 mm yr−1in the ombrotrophic bog. Variations in mean core bulk density were also significant and ranged from 0.071 ± 0.011 g cm−3(collapse fen) to 0.102 ± 0.011 g cm−3(poor fen). A regional survey incorporating measurements from other parts of the southwestern Northwest Territories and the southeastern Yukon show rates similar to those near Fort Simpson. These rates are significantly lower than published rates from other parts of northern Canada, Finland, and the former Soviet Union. Low and variable summer precipitation in the region may contribute to the low carbon accumulation rates through decreased plant production and/or increased aerobic decomposition.

A modified hydropneumo‐elutriation apparatus for quantitative root separation from large soil core samples

Abstract An apparatus was designed to separate roots automatically from large soil samples (>20 kg). The apparatus (1.50 m height) was constructed of polyvinyl chloride pipes (diameter = 100 mm). The roots were separated from soil mineral particles at the base of the apparatus by a high energetic hydrovortex, and then transfered to a 200‐μm sieve by a flow of water and small air bubbles. The inlet flow of both water and air were ajusted to obtain roots similar to those separated by hand (control). The statistical analysis indicated that 7 out of 42 tested pairs of water and air flows gave results not significantly different from the control. The inlet water flow is fixed to 3 L/min and the air inlet to 100 units for routine analysis. The washing cycle is completed in 5 minutes for 200 g of soil, but for larger soil samples, it could be extended over several hours after evacuating the mineral particules from the base of the apparatus.

Taking Large Core Samples Made Easy With a Shop Vacuum

Core sampling filter media can be a difficult and time‐consuming task if a large amount of media must be removed. However, “wet‐or‐dry” vacuum cleaners can reduce the time and effort spent. This technique was developed in the process of obtaining core samples of anthracite coal from a full‐scale filter bed for a pilot‐plant project.

Tillage effects on measured soil hydraulic properties

The effect of no-tillage (NT), ridge tillage imposed on long-term NT (NT/RT), moldboard plow (MBD), and chisel tillage (CHT) treatments on soil water retention and movement on three soils was studied using field and laboratory measurements. Field measurements of saturated hydraulic conductivity ( K fs) were made with a Guelph permeameter; laboratory measurements of saturated hydraulic conductivity ( K sat) were made using the constant head method on 30 and 7.5 cm diameter cores. The geometric mean of K sat from 30 cm cores was greater in NT than in MBD for both the Ap and B horizons of Nicollet clay loam (fine-loam, mixed, mesic Aquic Hapludoll) and Rozetta silt loam (fine-silty, mixed, mesic Typic Hapludalf); however, K sat from 7.5 cm cores was not significantly different for the two tillage treatments. The K sat for the Ap horizon of Seaton silt loam (fine-silty, mixed mesic, Typic Hapludalf) in NT/RT was lower than in CHT, possibly because of surface layer compaction produced during manure injection. A greater number and total area of stained macropores were found in NT than in MBD. Comparisons between methods of saturated hydraulic conductivity measurements showed that K sat values from 30 cm cores were the greatest for all treatments and depths, which may be attributed to the role of continuous macropores in large core samples. The K fs values obtained from the Guelph permeameter ( α = 12 m −1) were smaller than K sat values from 30 and 7.5 cm cores. Unsaturated hydraulic conductivity was measured with a disk permeameter both in the field and laboratory. For water potential values from −30 to −150 mm, the unsaturated hydraulic conductivity ( K suc) values were similar for the NT and the MBD treatments and were much lower than the K sat values. To include the effects of macropores, larger core samples are preferred.

Preparation of Large Core Samples from Stony Soils

AbstractA method was developed to take large, undisturbed soil cores in stony soils. An undisturbed soil core was surrounded with concrete, frozen to −22°C and cut to shape with a diamond circular saw, leaving only core sample. The core sample was surrounded with paraffin to maintain its shape.

Limitations of the Instantaneous Profile Method for Field Measurement of Unsaturated Hydraulic Conductivity

AbstractTechnical problems and soil profile characteristics may limit the applicability of the instantaneous profile method for field measurement of unsaturated hydraulic conductivities. A modified procedure for tensiometer installation and different methods for measuring moisture contents are discussed. Good agreement was found between moisture contents determined in situ with the neutron‐probe and those indirectly derived from moisture retention curves obtained from measurements of large core samples in a closed assembly. Sloping soils with slowly permeable horizons or with lateral water movement cannot be characterized adequately with this method. The use of the crust test procedure is recommended.

Determination of Some Frozen and Thawed Properties of Permafrost Soils

Mackenzie Valley Pipe Line Research Limited has undertaken a significant amount of full-scale testing at its test site near Inuvik, N.W.T. Large diameter high ice content permafrost core samples were taken from this site to controlled laboratory conditions, and tested in both frozen and thawed states so that proposed predictive methods for pipeline performance could be evaluated.This paper describes procedures for sampling, sample transportation at controlled temperatures, and sample preparation in the laboratory. Methods for thaw-settlement and thaw-strength are also described. The results of these tests are presented and analyzed.

Marine palynology: Possibilities, limitations, problems

In general, pollen and spores are present in the sediments of the deep ocean basins, particularly in deposits of terrigenous origin. Pollen spectra of abyssal sediments reflect the vegetation of adjacent land masses. Deposits of abyssal plains and oceanic rises with relatively little local relief, situated in the temporate zones, present the most favorable opportunities for obtaining a continuous history of vegetational and climatic changes during the Quaternary. The very slow rate of deposition in the ocean basins and the need to have relatively large core samples in order to obtain a sufficient number of pollen grains impose a limit on the detail with which reconstruction of vegetation and climate can be accomplished. Occurrence of reworked plant microfossils presents difficulties particularly where pre-Quaternary sediments are exposed on the continental shelf or slope.

The Effect of Fluid-Flow Rate and Viscosity on Laboratory Determinations of Oil-Water Relative Permeabilities

Published in Petroleum Transactions, AIME, Volume 213, 1958, pages 36–43. Abstract The effect of fluid-flow rate and fluid viscosity on oil-water relative permeability determinations was studied using the "dynamic flow technique." In this work relative permeability curves were obtained for homogeneous small core samples from several sandstone outcrop formations. Radio-tracers were used for the determination of fluid saturation and for the detection of saturation gradients. Cobalt–60 in the form of cobaltous chloride was used as a water-phase tracer in some of the experiments. Iodine–131 in the form of iodobenzene and Mercury–203 in the form of mercury diphenyl were used as oil-phase tracers in other experiments. Flow rates for each phase were varied within a range of 2.5 to 140.6 ml/hr. Oil-phase viscosities under flowing conditions were varied from 0.398 to 1.683 cp. The relative permeabilities obtained were found to be solely a function of saturation and independent of flow rate, provided there was no saturation gradient induced in the core sample by "boundary effect." Even though equilibrium with respect to flowing conditions was obtained at the lower flow rates, where a saturation gradient exists, this equilibrium is of a "contingent" -type rather than the "steady-state" equilibrium implicit in the relative permeability concept. The only effect of increasing the oil or non-wetting phase viscosity was to decrease the flow rate required for the elimination of the boundary effect. Fairly good agreement between experimentally determined and calculated values of the boundary effect was obtained when the non-wetting oil phase was the only flowing phase. Introduction In the characterization of reservoir rock, as well as in the solution of reservoir production problems, it is most desirable to have reliable relative permeability measurements for the rock and fluids of interest. Many techniques have been developed for the laboratory determination of the relative permeability of both large and small core samples. In varying degree, difficulties attend the use of all of the methods. Each of the methods requires the metered flow of fluids of known viscosity through the core sample under conditions wherein the pressure drop in the individual flowing phases can be measured or closely approximated. Since the relative permeability is a function of the saturation and distribution of the flowing fluids, some means of obtaining such information is also required.

Recent Laboratory Investigations of Water Flooding in California

Abstract Laboratory flood pot testing of California sands has progressed to aconsiderable extent in the past 18 months. Flood evaluations have been carriedout on over 200 large core samples. Many of these were heavy oil sands of highpermeability and completely unconsolidated in nature. The oil frequently formeda bank, though some of the oil was recovered in the subordinate phase of theflood, by viscous drag. Flood pot recoveries as high as 1400 bbl/ acre ft havebeen recorded. Reservoir analysis suggests a conformance factor of 0.4 toreduce laboratory recovery to probable field practice. Oils with viscosities upto 1800 cp have been successfully handled in flood pot evaluations. Theshallow, loose sands are not well adapted to the application of high pressuresto offset the high viscosities. Introduction Secondary recovery may be said to have started 60 years ago when accidentalfloods occurred in the Bradford sand in Pennsylvania; About 1921 artificiallyconducted water drives came into extensive use and since that time the greatBradford field has been almost completely subjected to water flooding. Duringthe last 30 years, most of the known medium and deeper production in Californiahas been discovered and is being exploited by primary recovery methodssupplemented in some instances by high pressure gas injection. The Californiaarea is just beginning to feel the need for secondary recovery in view of anunprecedented market demand and the rapidly rising cost of new pooldiscoveries. With the presently recognized desirability of secondary recovery inCalifornia, there must also be appreciated a number of serious differencesbetween the water flooding problems here as compared to the territory east ofthe Rockies. California sands are generally thicker, and are frequently softand argillaceous. The oils are often heavier and asphaltic. Much of the oil isbelow 15?API, occurs at shallow depth, is cool and free from appreciabledissolved gas, which results in relatively high reservoir oil viscosity.Secondary recovery is particularly beneficial where primary recovery has beenpoor and where no natural water drive exists. These conditions applyparticularly to the heavy, shallow, clean production from soft, oftenargillaceous California sands so abundantly found at depths less than 1500feet. Often, too, there is a totally insufficient supply of water ofsatisfactory quality to inject at a reasonable cost. Also, the crude oils arepriced far below the premium Bradford crude. T.P. 3640