Academic literature on the topic 'Direct in situ high-pressure preconcentration'

Abstract. We have developed a field-deployable gas chromatograph (GC) with thermal desorption preconcentration (TDPC), which is demonstrated here with automatic detector switching between two high-resolution time-of-flight mass spectrometers (TOF-MSs) for in situ measurements of volatile organic compounds (VOCs). This system provides many analytical advances, including acquisition of fast time–response data in tandem with molecular speciation and two types of mass spectral information for each resolved GC peak: molecular ion identification from Vocus proton transfer reaction (PTR) TOF-MS and fragmentation pattern from electron ionization (EI) TOF-MS detection. This system was deployed during the 2018 ATHLETIC campaign at the University of Colorado Dal Ward Athletic Center in Boulder, Colorado, where it was used to characterize VOC emissions in the indoor environment. The addition of the TDPC-GC increased the Vocus sensitivity by a factor of 50 due to preconcentration over a 6 min GC sample time versus direct air sampling with the Vocus, which was operated with a time resolution of 1 Hz. The GC-TOF methods demonstrated average limits of detection of 1.6 ppt across a range of monoterpenes and aromatics. Here, we describe the method to use the two-detector system to conclusively identify a range of VOCs including hydrocarbons, oxygenates, and halocarbons, along with detailed results including the quantification of anthropogenic monoterpenes, where limonene accounted for 47 %–80 % of the indoor monoterpene composition. We also report the detection of dimethylsilanediol (DMSD), an organosiloxane degradation product, which was observed with dynamic temporal behavior distinct from volatile organosiloxanes (e.g., decamethylcyclopentasiloxane, D5 siloxane). Our results suggest DMSD is produced from humidity-dependent heterogeneous reactions occurring on surfaces in the indoor environment, rather than formed through gas-phase oxidation of volatile siloxanes.

Abstract. Important information about the biogeochemical cycle of nitrous oxide (N2O) can be obtained by measuring its three main isotopomers, 14N15N16O, 15N14N16O, and 14N14N16O, and the respective site-specific isotope ratios δ15Nα and δ15Nβ. Absorption laser spectroscopy in the mid-infrared is a direct method for N2O isotopomer analysis, yet not sensitive enough for atmospheric N2O concentrations (320 ppb). To enable a fully-automated high precision N2O isotopomer analysis at ambient concentrations, we built and optimized a liquid nitrogen-free preconcentration unit to be coupled to a quantum cascade laser (QCL) based spectrometer. Rigorous tests were conducted, using FTIR and quantum cascade laser absorption spectroscopy (QCLAS), to investigate recovery rates, conservation of isotopic signatures and spectral interferences after preconcentration. We achieve quantitative N2O recovery of >99% with only minor, statistically not significant isotopic fractionation and no relevant spectral interferences from other atmospheric constituents. The developed preconcentration unit also has the potential to be applied to other trace gases and their isotopic composition.

Abstract. Important information about the biogeochemical cycle of nitrous oxide (N2O) can be obtained by measuring its three main isotopic species, 14N15N16O, 15N14N16O, and 14N14N16O, and the respective site-specific relative isotope ratio differences δ15Nα and δ15Nβ. Absorption laser spectroscopy in the mid-infrared is a direct method for the analysis of the 15N isotopic composition of N2O, yet not sensitive enough for atmospheric N2O mixing ratios (320 ppb). To enable a fully-automated high precision analysis of N2O isotopic species at ambient mixing ratios, we built and optimized a liquid nitrogen-free preconcentration unit to be coupled to a quantum cascade laser (QCL) based spectrometer. During standard operation 10 l of ambient air are preconcentrated on a HayeSep D trap and desorbed in 50 ml of synthetic air. Rigorous tests were conducted, using FTIR, quantum cascade laser absorption spectroscopy (QCLAS), GC-FID and component-specific ozone and oxygen analysers to investigate recovery rates, conservation of isotopic signatures and spectral interferences after preconcentration. We achieve quantitative N2O recovery of >99% with only minor, statistically not significant isotopic fractionation and no relevant spectral interferences from other atmospheric constituents. The developed preconcentration unit also has the potential to be applied to other trace gases and their isotopic composition.

In situ high-pressure synchrotron X-ray powder diffraction studies of trigonal α-ZrMo2O8, zirconium molybdate, have been performed from ambient conditions to 1.9 GPa, over the α–δ phase transition at 1.06–1.11 GPa. The monoclinic structure of δ-ZrMo2O8, stable between 1.1 and 2.5 GPa at 298 K, has been solved by direct methods and refined using the Rietveld method. Significant distortions of the ZrO6 and MoO4 polyhedral elements are observed for δ-ZrMo2O8, as compared to the ambient conditions of the α-phase, while the packing of anions becomes more symmetric at high pressure.

Abstract The three dimensional (3D) displacement induced by fluid injection was measured during two fault reactivation experiments conducted in carbonate rocks at the Rustrel Low Noise Underground Laboratory (LSBB URL), France, and in shale rocks at the Mont Terri Rock laboratory, Switzerland. The faults were activated by injecting high pressure fluid and using the Step-Rate Injection Method for Fracture In-Situ Properties, which allows a coupled pressure-flowrate-3D displacement monitoring in boreholes. Both experiments mainly show complex aseismic deformation of preexisting fractures that depend on (1) the fluid pressure variations related to chamber pressurization and leakage into the formation and (2) irreversible shear slip and opening of the reactivated fractures. Here we detail the processing of the 3D displacement data from both experiments to isolate slip vectors from the complex displacement signal. Firstly, we explain the test protocol and describe the in situ hydromechanical behavior of the borehole/fault system. Secondly, we define the methodology of the displacement data processing to isolate slip vectors with high displacement rates, which carry information about the key orientation of fault reactivation. Finally, we discuss which slip vectors can potentially be used to solve the stress inversion problem.

In situ characterization of catalysts gives direct insight into the working state of the material. Here, the design and performance characteristics of a universal in situ synchrotron-compatible X-ray diffraction cell capable of operation at high temperature and high pressure, 1373 K, and 35 bar, respectively, are reported. Its performance is demonstrated by characterizing a cobalt-based catalyst used in a prototypical high-pressure catalytic reaction, the Fischer–Tropsch synthesis, using X-ray diffraction. Cobalt nanoparticles supported on silica were studied in situ during Fischer–Tropsch catalysis using syngas, H2 and CO, at 723 K and 20 bar. Post reaction, the Co nanoparticles were carburized at elevated pressure, demonstrating an increased rate of carburization compared with atmospheric studies.

Afin d’accroître les connaissances sur les composés traces présents dans les biogaz et biométhane et de garantir l’intégration durable de ces gaz dans le mix énergétique européen, une chaîne analytique complète a été développée dont un élément central est un dispositif d’échantillonnage de terrain permettant la préconcentration directe in situ des composés traces en prélevant ces gaz à leur pression actuelle (≤ 200 bara). Les composés traces ciblés dans ce travail incluent : alcanes (linéaires, cycliques, polycycliques), aromatiques, terpènes, alcènes, espèces organiques halogénées, espèces organiques oxygénées (alcools, aldéhydes, esters, éthers, cétones), siloxanes, composés soufrés organiques et inorganiques.L’état de l’art des techniques de prélèvement de gaz et de préconcentration pour la détermination de composés traces dans des matrices gazeuses a premièrement été réalisé. Sur base de cette étude, il fut choisi d’effectuer la préconcentration sur des tubes d’adsorbants multi-lits (TAM) assemblés manuellement. Le système de préconcentration fut élaboré et optimisé au laboratoire en sélectionnant des adsorbants commerciaux; les procédures d’assemblage et de conditionnement des nouveaux TAM furent établies; l’efficacité de quatre configurations de TAM à adsorber et libérer des composés traces ciblés fut testée en utilisant des mélanges de gaz synthétiques certifiés contenant des composés à l’état de traces (1 ppmmol) dans une matrice N2 ou CH4. Les analytes préconcentrés sur les TAM sont récupérés par désorption thermique (DT) des tubes au moyen d’un nouveau prototype de DT pour être analysés par chromatographie en phase gazeuse (CG) couplée à la spectrométrie de masse (SM).Deuxièmement, la méthode analytique et le prototype de DT ont été validés. Il fut démontré que le pouvoir résolutif du prototype de DT était plus élevé que celui obtenu par d’autres techniques de préconcentration ou d’autres méthodes d’injection en CG, telles que la microextraction en phase solide ou l’injection directe de gaz. Par ailleurs, les paramètres de CG-SM furent optimisés pour détecter le large spectre de composés traces potentiellement présents dans le biogaz et biométhane.Troisièmement, un prototype haute-pression innovant fut évalué, permettant le prélèvement de gaz pressurisés (≤ 200 bara) à travers les TAM pour la préconcentration directe et sous haute-pression des composés traces présents dans ces gaz. Ce prototype fut validé au laboratoire au moyen de mélanges de gaz synthétiques pressurisés avant d’être utilisé sur le terrain pour prélever du biométhane à 40 bara au niveau d’un poste d’injection dans le réseau de gaz naturel.Ensuite, la chaîne d’échantillonnage fut assemblée pour mener 6 campagnes de prélèvement durant lesquelles 6 flux différents de biogaz et biométhane furent prélevés sur une installation de stockage de déchets non dangereux et deux sites de méthanisation valorisant divers intrants. Les composés traces de ces gaz furent qualitativement déterminés via la méthode de DT-CG-SM élaborée. En un unique prélèvement et utilisant des volumes de gaz réduits (0.5 – 2 LN), un large spectre de composés traces issus de diverses familles chimiques (alcools, aldéhydes, alcènes, aromatiques, alcanes, esters, éthers, halogénés, cétones, soufrés, siloxanes et terpènes) furent identifiés. Des variations de composition en composés traces furent observées dans les différents gaz et les corrélations potentielles entre intrants, procédés de traitement des gaz et composés traces identifiés, furent discutées. La génération du mono-terpène p-cymène et d’autres terpènes dans les méthaniseurs digérant surtout des résidus alimentaires, a notamment été mise en évidence. La procédure de préconcentration haute-pression in situ développée dans ce travail peut certainement contribuer à faciliter les opérations de prélèvements de gaz sur le terrain pour déterminer les composés traces dans des matrices gazeuses telles que le biogaz et le biométhane
In pursuance of enhancing knowledge on biogas and biomethane’s trace compounds to help guarantee their sustainable integration in today’s European energy mix, a field sampling set-up enabling direct in situ preconcentration of non-metallic trace compounds in such gas samples at their pipe working pressure (up to 200 bara) was developed. Non-metallic trace compounds targeted in this work included alkanes (linear, cyclic, polycyclic), aromatics, terpenes, alkenes, halogenated organic species, oxygenated organic species (alcohols, aldehydes, esters, furans and ethers, ketones), siloxanes, organic and inorganic Sulphur-compounds. Firstly, state-of-the-art gas sampling and preconcentration techniques for the determination of trace compounds in gaseous matrices were reviewed. Based on this review, preconcentration was chosen to be performed on self-assembled multibed adsorbent tubes (MAT). The preconcentration system was elaborated and optimized in the laboratory: convenient commercial adsorbents were selected; procedures for the assembly and conditioning of new MAT were established; four MAT configurations were tested on their efficiency in adsorbing and releasing targeted trace compounds using certified synthetic gas mixtures containing targeted species at trace concentrations (1 ppmmol) in CH4 or N2 matrices. Analytes preconcentrated on MAT were recovered for analysis by thermal desorption (TD) of the tubes using a new TD prototype followed by gas chromatography (GC) hyphenated with mass spectrometry (MS) (TD-GC-MS). Secondly, the analytical method, and in particular the new TD prototype, was validated. The chromatographic resolution power of the new TD prototype was proved to be higher than that obtained from other well established preconcentration or GC-injection methods such as solid phase microextraction or direct headspace gas injection. Besides, GC-MS parameters were optimized to detect the broad range of trace compounds potentially found in biogas and biomethane.Thirdly, the use of a novel high-pressure tube sampling (HPTS) prototype was evaluated for the circulation of pressurized gases (up to 200 bara) through MAT for the direct high-pressure preconcentration of trace compounds from such gases. The HPTS was first validated in the laboratory using pressurized certified synthetic gas mixtures, and then used on field to sample compressed biomethane at a natural gas grid injection station at 40 bara.Subsequently, the field sampling chain was set-up and 6 field sampling campaigns were conducted where 6 different streams of landfill gas, biogas and biomethane were collected at a landfill plant and two anaerobic digestion plants treating diverse feedstocks. Trace compounds were qualitatively determined in all gas samples via the developed TD-GC-MS method. In a single sampling run and using limited gas volumes ranging 0.5 – 2 LN, a wide range of trace compounds in a variety of chemical families (alcohols, aldehydes, alkenes, aromatics, alkanes (linear, cyclic and polycyclic), esters, furans and ethers, halogenated species, ketones, Sulphur-compounds, siloxanes and terpenes) were identified. Variations in trace compounds composition were observed in the different gases sampled and potential correlations between feedstocks nature, implemented gas treatment processes and trace compounds determined were discussed. In particular, the substantial generation of the mono-terpene p-cymene and of other terpenes was evidenced for anaerobic digestion plants treating principally food-wastes. It is believed the shortened and high-pressure-proof field preconcentration procedure developed in this work can contribute facilitating field sampling operations for the determination of trace compounds in complex gas matrices such as biogas and biomethane

In-situ inert gas high pressure vessels for neutron scattering for pressures of up to 1.0 GPa, and temperatures as low as 1.5 K, pose a particular problem due to the P × T phase diagram of the pressure media. Hydrostatic pressure under constant pressure and volume, passing through the pressure versus temperature phase diagram (P × T) of the gas to achieve low temperatures (1.5 K < T < 30 K) will cause an overall pressure reduction at base temperatures of at most 25% of the pressure read at the P × T. A methodology for pressurization to ensure minimal pressure loss as temperature falls below the pressure media phase change and at the same time minimizing pressure inhomogeneity throughout the length of the sample is presented within this work. The technique proved to reduce the isochore loss of pressure by a factor of 5. Moreover, for the first-time direct experimental quantitative evidence of the reduction in pressure inhomogeneities across large samples is reported here, and the average inhomogeneity reduction in pressure across top and bottom of a 45 mm long sample is better than a factor of 3.

Abstract Fatigue test specimens were prepared and tested with an API 5L X70 spiral welded pipe steel and girth weld. For a few selected specimens, two unloading compliance techniques (elastic compliance and back-face strain compliance) were applied simultaneously to a single specimen for direct comparisons of in-situ crack size estimation. This paper also includes fatigue crack growth rate (FCGR) data of other pipe steels and welds available in the literature. It was observed that most FCGR curves of pipeline steels (X65∼X100) remained within the BS 7910 mean and upper bound design curves in the Paris region. On the contrary, the fatigue crack growth rate of the X42 pipeline steel from a reference was high — a very steep slope of the FCGR curve, crossing over the BS 7910 design criteria. It was noted that the FCGR of austenitic stainless pipe steel and girth weld obtained from Arora et al. (2014) showed a very excellent fatigue property.

Some recent results obtained using three quite different experimental approaches to fast in-situ surface metallization are presented. One of the goals is to make high density interconnects for multichip modules with metal contact width, height and pitch respectively of the order of 10, 5 and 25 μm. Direct writing speeds should be in excess of 1 cm/s. The first approach tried is to push classical pyrolytic laser chemical vapor deposition of copper from its bis-hexafluoroacetylacetonate Cu(hfa)2 to its limits. This is done by increasing the Cu(hfa)2 vapor pressure and by seeding the transparent surface of our substrate with a thin layer of a strongly light-absorbing substance. Speeds in the order of a few mm/s have already been obtained with good electrical properties and adhesion. The second approach tested implies metallization by thermal in-situ decomposition of a metal complex layer on a surface with a laser beam. The precursors used in this work are metal cluster coordination complexes, in particular au55(pɸ3)12c16 (ɸ stands for phenyl group -C6H5). Such molecules have a high metal content and advantageous thermal decomposition properties which enable writing speeds in excess of 1 cm/s while maintaining acceptable electrical properties of the metal lines. Finally, in a third approach, the fast in-situ step is limited to deposition of a thin metal line on the surface. These lines of only a few Å height are then "developed" in a second step to much high (of the order of one μm) and better conducting metal lines. This second step may be relatively slow, as many devices which have been patterned on their surface with the thin metal "prenucleation" lines can subsequently be developed simultaneously in a parallel processing step. An example of this approach is surface seeding using metals like Pt, W or Ir, followed by development by either selective low pressure CVD of copper from Cu(hfa)2, selective decomposition of a copper formate solid surface film, or selective electroless deposition from a copper bath. Possibilities of processing with much higher resolution using focussed charged particle beams are also briefly discussed.

Abstract The in-situ stress, and in particular the minimum principal stress, is a major controlling parameter for many subsurface engineering issues, such as safe injection and injection pressure limitation, wellbore stability, fractured injection and stimulation, and completions optimization. In addition to these more ‘traditional’ field development decisions, in-situ stress has direct influence on the rapidly growing CCS industry, where storage volumes of CO2 are highly dependent on the initial minimum effective stress margins available in the sealing caprock(among other factors). In this work we investigate a unique in-house stress database, obtained through decades of dedicated stress testing, to better understand and quantify the relationship of in-situ stress versus depth and its relation to pore pressure. Focus is primarily on the Norwegian Continental Shelf but global results from additional passive continental margin areas are also incorporated and compared. We find that, almost regardless of the geographic area, when hydrostatic pore pressure conditionsapply, relatively simple linear relationships exist of stress versus depth and that the assumption of normally-stressed/relaxed stress regimes can be applied with a good degree of certainty. Further, where overpressure conditions are present, relationships dependent on the degree of overpressure are defined, both regionally and globally. The resulting overpressure relationship is found todiffer fromthose commonlyaccepted andused throughout industry, e.g. Breckels and van Eekelen 1982. Finally, the resulting stress trends versus depth are investigated to better identify the potential presence of high stress environments such as deeper strike-slip to reverse faulting regimes that can complicate field development decisions. While of interest to the hydrocarbon industry in general, the results of this work are highly valuable to under-explored areas where in-situ stress data is not yet available, e.g. saline aquifer prospects targeted for eventual CCS development.

Abstract Fatigue Crack Growth Rates (FCGRs) of austenitic stainless steels can be significantly enhanced when tested in a high temperature water environment compared to those tested in air. Existing FCGR models are based on simple isothermal waveform loading. Recent work has highlighted that there may be a potential benefit into taking account of plant realistic loading waveforms in fatigue assessments as these may be less damaging than predictions based on simple loading conditions. As a result, new methods to account for these plant realistic loads have been developed to reduce excess conservatism of existing methods for predicting FCGRs. To provide confidence in these methods, a previous UK thermomechanical fatigue testing programme has been conducted on Compact Tension (C(T)) specimens subjected to plant realistic loads, with the crack length and Crack Growth Rates (CGRs) being monitored in-situ using the Direct Current Potential Drop (DCPD) technique. This paper utilizes three different methodologies to evaluate the CGR of samples that underwent corrosion fatigue in different conditions namely; DCPD, post-mortem measurement of crack advance using Scanning Electron Microscopy (SEM), and the measurement of the spacing between striations to infer CGR. It was found that DCPD provided a good global average of FCGRs at the crack front but does not capture local changes associated with the local microstructure. Overall, it was shown that post-mortem examination for stage measurements can be reliably applied to infer CGR on samples that were not instrumented with DCPD.

The Small Punch (SP) test technique is an innovative, powerful technique based on tests using miniaturized specimens. At present, it is the only existing method capable of providing experimental characterization of service exposed materials of components. It is non invasive and provides direct measured material properties. It provides a significant technology capability that facilitates assessing power plant operating equipment for structural integrity and operational condition. The SP Testing facility supported by the in situ sampling for test specimens provides utility members an attractive option to interrogate equipment for making run/inspect/repair/replace decisions. It is supported by EPRI Software, NDE and Metallography facilities, to define guidelines for components life assessment cross the sector, serving both utilities, and constructors. It addresses the industrial need for personalized material and welds data required for: - lifing of plant, consumed life and residual life of components, - convenience of repairing, replacing, life of the new welds on old components, - cost of component deterioration, cost of normal service, - characterizations and qualifications of blade repairs, of coating materials-methods, - fast determination of new casts strength produced by Electron Beam. The sampling and test facility provides low temperature test data including transition temperature and fracture toughness (KIc, JIc) measurements with minimal empiricism, to a high-temperature material property data including tensile, creep and creep rupture properties. The materials used for components in power generation industry are presented along with the test facility and specific applications in the subject field.

Abstract The effect of an LWR environment on fatigue life is currently assessed using methods (such as NUREG/CR-6909) that may be excessively conservative when applied to plant components and loading transients. To reduce this conservatism, the ASME Working Group for Environmental Fatigue Evaluation Methods (WG-EFEM) has proposed the development of an improved assessment methodology for environmental fatigue based on a Total Life Prediction approach that would be adequately, but not excessively, conservative. Such an approach necessitates the development of analytical methods for the various stages of crack nucleation, short crack growth and long crack growth. Hence, there is a requirement to undertake testing within the short crack growth regime that would bridge the gap between fatigue nucleation and long crack growth (Paris Law) enabling better prediction of total life measured by fatigue endurance. Previous negative R long crack growth testing using corner-crack specimens measured the effects of crack closure under compressive loading, and has been used to address some of the conservatism in existing assessment methods. This methodology has been developed further to enable negative R short crack growth testing with in-situ monitoring using DCPD. Testing has been undertaken in both high temperature air (300°C) and a simulated PWR primary water chemistry at 300°C on both cold-worked and non-cold-worked stainless steel specimens at a load ratio of R = −1. One heat of stainless steel has been tested, with another heat of different grain size to be tested imminently, in order to investigate the effect of grain size on short crack growth rates. FEA modelling has been undertaken to both correlate Direct Current Potential Drop (DCPD) response with crack growth measurements, and to determine the effective stress intensity factor ranges applied under the loading conditions based on the specific material properties. This paper describes the methodology and findings from this negative R short crack growth test programme. Crack growth rates have been compared to ASME Code Sec. XI and Code Case N-809 reference curves and results from material specific in-house testing to assist the understanding of the behaviour of mechanically short cracks.

Leakage in oil and gas infrastructure, often cause significant financial losses, severe damage to the environment and raises public concern. In order to minimize the impact of spills, quick detection of a leak and a rapid response are needed. The systems currently employed to detect pipeline leakage range from simple visual checking to complex hardware and software systems such as mass balance, pressure point analysis, flow deviation, acoustic emission systems, and fibre-optic-based sensing technologies. These methods are useful, but there are certain limitations. The main drawback of the majority of these leak detection technologies is that they detect leakage indirectly, often unable to detect the leakage until the major spill. The preventive monitoring system and direct detection of hydrocarbon leakage are urgently needed to enable fast response and timely repairs with less deleterious effects. Research is being conducted for the development of a functional prototype and environmental testing of in-situ carbon nanotube (CNT) nanocomposite based sensors for hydrocarbon leakage detection. The CNT nanocomposite offers a unique approach to the direct hydrocarbon leakage detection in pipelines and aboveground storage tanks (ASTs). Expanding the study from the previous report of sensor characteristics under the optimal ambient condition, it was further investigated to identify the sensor performance under harsh conditions such as the underground (exposed to the soil) with compost and moisture, high pressure, changing temperature and long-term exposure to the outdoor environment. Investigation of the sensor behavior is studied, and a performance matrix is developed that accounts for the change in sensor response to various environmental conditions. Results showed that the proposed CNT nanocomposite sensor was applicable under given conditions with immediate responses while maintaining high sensitivity to the hydrocarbon leakage. Once a list of sensor detection specifications is defined, it is anticipated that the CNT sensor technology is applicable as part of a robust, reliable and accurate early detection system for the pipeline industry.

Abstract The authors provide an update on the normalized soil parameter (NSP) procedure for in-situ undrained shear strength evaluation in clay soils known as the SP (Strength- Pressure) - SPW (Strength- Pressure-Water) method. A modification is recommended for the SPW aspect of the method that will improve results for undrained shear strength interpretation. The SP-SPW method was initially developed in the year 2000 from a database of 172 CKoU direct simple shear tests and has proven to be very useful to practitioners in undrained shear strength interpretation over the past 23 years. The current investigators now have a database of over 2500 CKoUDSS tests. Analyses of this larger database of laboratory tests has led them to modify the SPW aspect of the shear strength interpretation method to yield more consistent and reliable results of in-situ undrained shear strength. Additionally, the current authors will present lessons gleaned from employing this NSP procedure over the past 23 years in a variety of clay soil types and stress histories. Analysis of the large database of CKoUDSS tests requires that practitioners keep in mind important aspects of soil behavior regarding consolidation pressure, particularly at the lower pressure range and at pressures exceeding a relatively high pressure threshold. Additionally, the recommended modification to the SPW aspect of shear strength evaluation leads to more consistent results. In the original 2000 paper, examples of application of the SP-SPW method were limited to a normally consolidated clay site and a second site that was normally consolidated to lightly overconsolidated. In this paper, the authors present examples of application in the following clay profiles: (1) very underconsolidated; (2) normally consolidated to lightly overconsolidated; (3) lightly to heavily overconsolidated; and (4) highly plastic, lightly overconsolidated due to aging. The approach presented here has proven to be priceless in assisting the practitioner in evaluating in-situ undrained shear strength, particularly when standard laboratory strength tests yield disturbed strength measurements. The examples of application of the method in the variety of soil profiles presented in the paper will demonstrate the reasonableness of the strength values obtained and allow the practitioner to avoid being unnecessarily conservative in evaluating in-situ undrained shear strength. When the SP-SPW method was first proposed almost 23 years ago (Quiros et al, 2000), the authors noted the following significant findings: No reliable cu/σ’vc – Ip correlation was discernible for the database of soils studied. Consolidation pressure clearly has a profound effect on the ratio and should be considered when planning SHANSEP-type laboratory programs as well as when evaluating test results. A remarkably good correlation was found to exist between laboratory shear strength, cu and consolidation pressure, σ’vc. The SPW method, which introduced water content into the correlation between shear strength and consolidation pressure, proved to be a useful tool for evaluating in-situ undrained shear strength. Subsequently, this method has been employed in hundreds of geotechnical site investigations, and the results have corroborated the forementioned conclusions of the original study. In following sections of this paper, we will briefly discuss the SP- SPW method, present the updated database, discuss modification to the SPW aspect of the procedure, and then demonstrate results of the method at four different sites.

Abstract Carbonate reservoir rocks usually have complex pore systems of broad size distributions, which determine many aspects of oil exploitation, from petrophysical properties to oil/water displacements. An accurate and complete description of these pore systems remains a challenge. A single technique often gives one measurement of complicated microscopic pore space. The new techniques (i.e., micro-CT and NMR) are utilized together with conventional methods (e.g., MICP, BET) to capture a more accurate and complete picture of pore structures. MICP measures the pore throat while the NMR T2 mainly measures the pore body. Micro-CT provides a 3D image of a limited sample size. Recently, NMR DDIF (decay due to diffusion in the internal field) for direct pore body size is extended from high to low magnetic field, which overcomes many limitations in pore system characterization. This study obtains pore throat size distributions from in-situ centrifuge capillary pressure and pore body size distributions from low field DDIF measurement and verifies them with micro-CT and BET/T2 in different types of carbonate rocks. The pore throat size distribution of the conventional sample is obtained from in-situ centrifuge capillary pressure. The major features of both macro and micro pore throat size distributions are captured. Pore size distributions are directly obtained from glass beads and carbonate rocks without calibration. Combined analysis of the pore size distribution from two methods reveals the underlying causes of their different petrophysical properties. The pore throat size distribution from in-situ centrifuge capillary pressure and pore size distribution from NMR DDIF can be employed to obtain a better understanding of conventional carbonate pore systems.

Abstract CO2 foam holds promising potential for conformance improvement and mobility reduction of CO2 injection in fractured systems. However, there still exists two main issues hampering its wide application and development, 1. Instability of CO2 foam lamellae under reservoir conditions, and 2. Uncertainties of foam flow in fracture systems. To address these two issues, we previously developed a series of functional nanocellulose materials to stabilize the CO2 foam (referred to NCF-st-CO2 foam), while the primary goal of this paper is to thoroughly elucidate foam generation, propagation and sweep of NCF-st-CO2 foam in fractured systems by using a self-designed visual heterogeneous fracture network. We found that NCF-st-CO2 foam produced noticeably greater pressure drop (ΔP) than CO2 foam during either co-injection (COI) or surfactant solution-alternating-gas (SAG) injection, and the threshold foam quality (fg*) was approximately 0.67. Foam generation was increased with total flow rate for CO2 foam and stayed constant for NCF-st-CO2 foam in fracture during COI. CO2 breakthrough occurred at high flow rates (&gt;8 cm3/min). For SAG, large surfactant slug could prevent CO2 from early breakthrough and facilitate foaming in-situ. The increase in sweep efficiency by NCF-st-CO2 foam was observed near the producer for both COI and WAG, which was attributed to its better foaming capacity. Film division and behind mainly led to foam generation in the fracture model. Gravity segregation and override was insignificant during COI but became noticeable during SAG, which caused the sweep efficiency decreased by 3~9% at 1.0 fracture volume (FV) injected. Due to the enhanced foam film, the NCF-st-CO2 foam was able to mitigate gravitational effect, especially in the vicinity of producer.