bluuebunny/crossref_metadata_2025_split huggingface dataset:
Shear Modulus and Damping Ratio of Unsaturated Kaolin Measured by New Suction-Controlled Cyclic Triaxial Device
Authors: Biglari Mahnoosh , Jafari Mohammad Kazem , Shafiee Ali , Mancuso Claudio , d’Onofrio Anna 
Published: July 2011

Abstract
The cyclic triaxial test is the most widely used way to measure the cyclic stress–strain properties of saturated soils because of its availability in most geotechnical laboratories. Further, it can be viewed as a suitable tool with which to analyze the cyclic behavior of unsaturated soils in a wide strain range. In this study, a new stress path suction-controlled cyclic triaxial device is presented. It is fitted for suction-controlled testing by the axis-translation technique. Pore-air and pore-water pressures are applied at the top and bottom of the specimen by using two electro-pneumatic regulators. The capability of the new apparatus is demonstrated in this paper with the results of some suction-controlled cyclic triaxial tests. The tests are carried out on compacted specimens of lean clay that are prepared in the same initial condition and tested following different stress paths. The stress paths include suction equalization, constant suction ramped isotropic compression, series of constant suction cyclic loading, and post-cyclic constant suction ramped isotropic compression stages. Volumetric behavior and evolution of the yield curves along suction equalization, constant suction ramped isotropic compression, and post-cyclic compression stages are discussed on the basis of the Barcelona Basic Model elasto-plastic framework. The stiffness and damping ratio of the specimens are subsequently presented, highlighting the dependency of the Young’s modulus (E), shear modulus (G), and damping ratio (D) on the shear strain amplitude, number of cycles, and suction. The results show that E and G increase, whereas D decreases significantly by increasing suction at similar strain levels and number of cycles.
An Adapted Ring Shear Apparatus for Testing Partly Saturated Soils in the High Suction Range
Authors: Merchán Vladimir , Romero Enrique , Vaunat Jean 
Published: July 2011

Abstract
The paper presents an adapted experimental setup to study the residual shear strength properties of clays under unsaturated state conditions. This issue is of geotechnical concern in stability analysis of slopes in fissured rocks with unsaturated clayey fills and also, in a more fundamental way, as an indicator of microstructural changes of clays undergoing drying paths. To this end, a commercial ring shear apparatus (Bromhead type) was instrumented and adapted to control total suction in a wide range by using vapor transfer technique. In addition, by using simulation-aided techniques, the time evolution of suction at local state and axial deformation was studied to overcome the experimental difficulty associated with the determination of the suction equalization time. The simulated equalization period agreed well with the experimental information based on a mechanical stabilization criterion (time required to attain vertical strain rates lower than 0.1%/day). Relevant test results showing the main capabilities of the adapted apparatus are presented, which bring up the important changes observed in residual friction angle when testing a clayey soil at different hydraulic states (total suctions ranging from nearly 0 up to 140 MPa).
Joint Inference of Population Assignment and Demographic History
Authors: Choi Sang Chul , Hey Jody 
Published: July 2011

AbstractA new approach to assigning individuals to populations using genetic data is described. Most existing methods work by maximizing Hardy–Weinberg and linkage equilibrium within populations, neither of which will apply for many demographic histories. By including a demographic model, within a likelihood framework based on coalescent theory, we can jointly study demographic history and population assignment. Genealogies and population assignments are sampled from a posterior distribution using a general isolation-with-migration model for multiple populations. A measure of partition distance between assignments facilitates not only the summary of a posterior sample of assignments, but also the estimation of the posterior density for the demographic history. It is shown that joint estimates of assignment and demographic history are possible, including estimation of population phylogeny for samples from three populations. The new method is compared to results of a widely used assignment method, using simulated and published empirical data sets.
A Conserved Long Noncoding RNA Affects Sleep Behavior inDrosophila
Authors: Soshnev Alexey A , Ishimoto Hiroshi , McAllister Bryant F , Li Xingguo , Wehling Misty D , Kitamoto Toshihiro , Geyer Pamela K 
Published: July 2011

AbstractMetazoan genomes encode an abundant collection of mRNA-like, long noncoding (lnc)RNAs. Although lncRNAs greatly expand the transcriptional repertoire, we have a limited understanding of how these RNAs contribute to developmental regulation. Here, we investigate the function of the Drosophila lncRNA called yellow-achaete intergenic RNA (yar). Comparative sequence analyses show that the yar gene is conserved in Drosophila species representing 40–60 million years of evolution, with one of the conserved sequence motifs encompassing the yar promoter. Further, the timing of yar expression in Drosophila virilis parallels that in D. melanogaster, suggesting that transcriptional regulation of yar is conserved. The function of yar was defined by generating null alleles. Flies lacking yar RNAs are viable and show no overt morphological defects, consistent with maintained transcriptional regulation of the adjacent yellow (y) and achaete (ac) genes. The location of yar within a neural gene cluster led to the investigation of effects of yar in behavioral assays. These studies demonstrated that loss of yar alters sleep regulation in the context of a normal circadian rhythm. Nighttime sleep was reduced and fragmented, with yar mutants displaying diminished sleep rebound following sleep deprivation. Importantly, these defects were rescued by a yar transgene. These data provide the first example of a lncRNA gene involved in Drosophila sleep regulation. We find that yar is a cytoplasmic lncRNA, suggesting that yar may regulate sleep by affecting stabilization or translational regulation of mRNAs. Such functions of lncRNAs may extend to vertebrates, as lncRNAs are abundant in neural tissues.
emb-1 Encodes the APC16 Subunit of the Caenorhabditis elegans Anaphase-Promoting Complex
Authors: Shakes Diane C , Allen Anna K , Albert Kelsey M , Golden Andy 
Published: July 2011

Abstract
In the nematode Caenorhabditis elegans, temperature-sensitive mutants of emb-1 arrest as one-cell embryos in metaphase of meiosis I in a manner that is indistinguishable from embryos that have been depleted of known subunits of the anaphase-promoting complex or cyclosome (APC/C). Here we show that the emb-1 phenotype is enhanced in double mutant combinations with known APC/C subunits and suppressed in double mutant combinations with known APC/C suppressors. In addition to its meiotic function, emb-1 is required for mitotic proliferation of the germline. These studies reveal that emb-1 encodes K10D2.4, a homolog of the small, recently discovered APC/C subunit, APC16.
Sand on Demand: A Laboratory Investigation on Improving Productivity in Horizontal Wells Under Heavy-Oil Primary Production
Authors: Meza-Díaz Brígida , Sawatzky Ronald , Kuru Ergun , Oldakowski Kaz 
Published: July 2011

Summary
The cold-production recovery process, also known as cold heavy-oil production with sand (CHOPS), is a method for enhancing primary heavy-oil production by aggressively producing sand (massively and persistently). It is a successful commercial recovery process in western Canada using vertical (or slanted or deviated) wells. Applications of cold-production technology with aggressive sand production in horizontal wells, however, have not met with commercial success.
This paper presents the results of experiments performed to assess the feasibility of applying cold heavy-oil production with horizontal wells using less-aggressive (i.e., controlled) sand-production strategies. Specifically, the effects of slot size, confining stress, fluid velocity, and sand-grain sorting on sand production have been investigated.
Preliminary results indicate that slot-size selection is critical for establishing "sand on demand." For proper slot-size selection, it is essential to know the grain-size distribution of the sand—in particular, attributes such as the size of the coarsest fraction of the sand and the sorting (uniformity coefficient) of the sand. For example, it was observed in the sand-production experiments that the critical pressure gradient for maintaining continuous sand production is much lower for well-sorted sands (narrow size distribution) than for poorly sorted sands (wide size distribution). Ultimately, poorly sorted sands may require criteria different from those for well-sorted sands for slot-size selection.
Flow rates are also crucial for managing sand production because a critical pressure gradient is required for initiating sand production and maintaining continuous sand production. The critical pressure gradient decreases as the slot width or confining pressure increases. Large permeability increases were observed in the sand-production region. Persistent sand production led to the growth of a channel and/or the presence of a dilated zone that had an elliptic shape.
Method for Determining the Bioconcentration Factor of Linear Alcohol Ethoxylates
Authors: Fraser Greig 
Published: July 2011

Summary
Determination of the potential of surfactants to bioaccumulate in marine species has long been problematic in the chemical-hazard and environmental-impact assessments performed for offshore operations. Recently, this issue has become increasingly significant because regulators have invoked the precautionary principle and assume that all surfactants with molecular weight of less than 700 will bioaccumulate, leading to an increased number of oilfield-chemical products labeled as environmentally unacceptable.
The relationship between the bioconcentration factor (BCF) of nonsurfactant substances and their corresponding octanol/water partition coefficient (Pow) value is well studied, and many relationships have been developed. Log Pow is generally, therefore, used as a surrogate for the BCF of nonsurfactant substances.
This methodology cannot be applied directly to surfactants because the formal log Pow of such substances is difficult, if not impossible, to determine accurately. By their very nature, surfactants tend to form emulsions or accumulate at interfaces; therefore, the standard OECD 107 [Test No. 107: Partition Coefficient (n-octanol /water): Shake Flask Method 1995] or OECD 117 [Test No. 117: Partition Coefficient (n-octanol /water), HPLC Method 2004] protocols cannot be used.
This paper describes a simple method for accurately determining the BCF of linear alcohol ethoxylates (LAEs), an important group of nonionic surfactants that are commonly used in the oil industry. Quantitative structure-activity relationship (QSAR) software built on fragment contributions averaged over a large number of mostly nonsurfactant substances is initially used to calculate a "log pseudoPow" value. This hydrophobic parameter is then correlated to BCF values determined in flow-through experiments, with excellent agreement (R2 &gt; 0.99). The method involves no animal testing, is inexpensive to set up and perform, is accessible to all, is quick and easy to use and verify, and gives clear output.
Laboratory Study of Diversion Using Polymer-Based In-Situ-Gelled Acids
Authors: Gomaa A.M. M , Mahmoud M.A.. A. , Nasr-El-Din H.A.. A. 
Published: July 2011

Summary
In-situ-gelled acids that are based on polymers have been used in the field for several years and were the subject of many laboratory studies. These acids are used in stages to block the treated zone and force the next regular-acid stages to the untreated zones. An extensive literature survey reveals that there are conflicting opinions about using these acids. On one hand, these acids were used in the field, with mixed results. On the other hand, recent laboratory work indicated that these acids can cause damage under certain conditions.
The ability of polymer-based in-situ-gelled acids to divert regular acids was studied using a parallel-coreflood setup. The sequence of the injection involved in-situ-gelled acid at 5 wt% hydrochloric acid (HCl) stage followed by regular acid at 15 wt% HCl until acid breakthrough. Experimental results show that flow was initially distributed between the two cores according to the preacid permeability ratio. Permeability grew slightly faster in the higher-permeability core until breakthrough occurred. Therefore, diversion was needed for all acid treatments. At an injection rate of 1 cm3/min, in-situ-gelled acid plugged the two cores. For low permeability contrast (1:2), polymer was able to divert the acid, with permeability enhancement in both cores.
For high permeability contrast (1:20 up to 1:25), in-situ-gelled acid was able to divert the acid only at an injection rate less than 10 cm3/min. However, at higher injection rates, in-situ-gelled acid was not able to build enough pressure to force the regular acid into the low-permeability core. Increasing the injection rate reduced the viscosity of the in-situ-gelled acid. Therefore, acid-injection rate should be determined on the basis of the expected fluid viscosity in the formation. The results obtained can be used to design acid treatments in carbonate reservoirs better.
Methods for Enhancing Far-Field Complexity in Fracturing Operations
Authors: East Loyd , Soliman M.Y.. Y. , Augustine Jody 
Published: July 2011

Summary
For decades, the oil industry has struggled to overcome nearwellbore-fracture complexity during fracturing treatments, particularly in low-permeability, naturally fractured hard-rock reservoirs. A number of techniques have been created to diagnose and remediate these conditions to enable the extension of created fractures and successful placement of proppant deep in the reservoir. Microseismic-fracture-mapping (MSFM) technology has revealed the creation of far-field complex fracture networks in hard-rock reservoirs during fracture extension. This revelation offers the opportunity to hydraulically connect to a much larger volume of rock, provided that appropriate treatment techniques are applied to ensure the fracture network is adequately connected to the main fracture. Additionally, techniques have been developed and can be applied during the fracture treatments to facilitate and enhance the fracture-network creation. Net fracture-extension pressure analysis combined with real-time MSFM allows for identification of the degree of fracturing-network creation and provides a decisionmaking tool for engineers to modify treatment schedules or apply complexity-enhancing methods on the fly on the basis of desired treatment objectives and rock responses to the fracture treatment.
This new approach to fracture stimulation requires a new focus on rock mechanics that includes defining the brittleness of the rock matrix, determining the existence and magnitude of the principal-stress anisotropy, designing the optimum spacing between fractures, and defining the optimum fracture-treatment parameters. Once the completion design is implemented, the designed treatment parameters can be adjusted in real time to meet the objectives of the completion on the basis of actual rock responses to the treatment. These rock responses are measured in real time using net fracture-extension pressure and MSFM diagnostics. Adjustments made to the fracture treatment are varied and include treatment-rate adjustments, proppant concentration, proppant-slug placement, diversion techniques to ensure opening of natural fractures, viscous-fluid spacers, acid spacers, and incremental stop/start pumping schedules. The proppant-concentration adjustments are enabled for immediate downhole changes through a unique coiled-tubing (CT) fracturing process that incorporates liquid/sand concentrate slurries.
Examples of actual completion designs of these applications are discussed.
Optimum Injection Rate of A New Chelate That Can Be Used To Stimulate Carbonate Reservoirs
Authors: Mahmoud M.A.. A. , Nasr-El-Din H.A.. A. , De Wolf C.A.. A. , LePage J.N.. N. 
Published: July 2011

Summary
Different chelating agents were used as alternatives for hydrochloric acid (HCl) in matrix acidizing to create wormholes in carbonate formations. Previous studies demonstrated the use of ethylenediaminetetraacetic acid (EDTA), hydroxy ethylenediaminetriacetic (HEDTA), and glutamic acid-N,N-diacetic acid (GLDA) as standalone stimulation fluids to stimulate carbonate reservoirs. The main problem of using EDTA and HEDTA is their low bio-degradability.
GLDA was introduced as a standalone stimulation fluid for deep carbonate reservoirs where HCl can cause corrosion and face dissolution problems. In this study, calcite cores 1.5 in. in diameter and 6 or 20 in. in length were used to determine the optimum conditions where the GLDA can break through the core and form wormholes. GLDA solutions with pH values of 1.7, 3, and 3.8 were used. The optimum conditions of injection rate and pH were determined using coreflood experiments. Damköhler number was determined using the wormhole length and diameter from the CT scan 3D and 2D images. GLDA was compared with chelates that are used in the oil industry such as EDTA and HEDTA. GLDA also was used to stimulate parallel cores with different permeability ratios (up to 6.25).
GLDA was found to be very effective in creating wormholes at pH = 1.7, 3, and 3.8; at different injection rates; and at temperatures up to 300°F. Increasing the temperature increased the reaction rate and less volume of GLDA was required to break through the core and form wormholes. Unlike HCl, in GLDA there was no face dissolution or washout in the cores even at low injection rates (0.5 cm3/min). An optimum injection rate and Damköhler number were found at which the pore volume (PV) required to create wormholes was the minimum. GLDA at pH 1.7 and 3 created wormholes with a small number of PV (at 1 cm3/min, GLDA at pH 1.7 required 1.5 PV at 300°F, and at pH 3 it required 1.8 PV). Compared with acetic acid, the volume of GLDA at pH 3 required to create wormholes was less than that required with acetic acid at the same conditions. GLDA was found to be effective in stimulating parallel cores up to 6.25 permeability contrast (final permeability/initial permeability).
New Perspective on Gas-Well Liquid Loading and Unloading
Authors: Veeken C.A.M.. A.M. , Belfroid S.P.C.. P.C. 
Published: July 2011

Summary
This paper discusses the multiphase-flow mechanism responsible for gas-well liquid loading. It shows that the conventional idea of droplet-flow reversal (Turner et al. 1969) does not fully describe reality and that liquid-loading observations appear more compatible with film-flow reversal. This paper subsequently explores how film-flow reversal changed views on existing gas-well liquidunloading techniques such as continuous foam injection, and it discusses new methods of gas-well deliquefication that specifically aim to delay film-flow reversal. The benefits of different types of tubing-wall modification have been evaluated through small-scale laboratory testing. Most promising, hydrophobic coating of tubing reduces the gas rate below which liquid loading occurs by approximately 50%. The benefits of hydrophobic coating are translated to representative field conditions.
Stochastic Analysis of Resource Plays: Maximizing Portfolio Value and Mitigating Risks
Authors: Allan Paul D. 
Published: July 2011

Summary
This paper outlines a method for applying stochastic representations of key macroeconomic parameters and risks in evaluating the portfolio value of resource plays. Stochastic pricing, costs forecasts, and regulatory uncertainties are often neglected or are applied improperly when evaluating what are typically considered to be low-risk resource opportunities. Portfolio allocation and project-development timing may be critically dependent upon these macroeconomic variables, particularly given the long production life and operationally intensive nature of many resource opportunities. The techniques described in this paper will allow corporate planners and exploration-and-production (E&P) executives to better leverage their opportunity inventory and ensure that resource-play development plans are in alignment with stochastic pricing or other macroeconomic forecasts. A model of a typical E&P portfolio with numerous resource plays will be used to demonstrate the basic methodologies and the insights made possible through application of these techniques. This will include analysis of leasing options, pilot-project evaluation, development-timing and -pacing options, and portfolio balance under various macroeconomic conditions. The characteristics of project-level analysis will be contrasted to the decisions and insights made possible through a holistic portfolio-based approach.
Net CO2 Stored in North American EOR Projects
Authors: Faltinson John E. , Gunter Bill 
Published: July 2011

Summary
One promising method for reducing carbon dioxide (CO2) emissions when storing CO2 in oil reservoirs is CO2 enhanced oil recovery (EOR). In order to make a significant contribution to mitigating climate change from emissions of greenhouse gases (GHGs), CO2 EOR must actually reduce CO2 emissions by storing net positive volumes of CO2. This requires that CO2-EOR schemes store more CO2 in the subsurface than the execution of the project emits (net positive storage of CO2). Fugitive emissions associated with CO2 EOR primarily include the burning of fossil fuels (fuel gas) to power CO2-injection compressors and the on-site consumption of electric power, which results in CO2 emissions off site, where the power was generated. Evaluating the effectiveness of CO2 EOR in reducing CO2 emissions must be conducted in an unbiased way in which only relevant fugitive emissions that are directly connected with the CO2-EOR project are deducted. It has been suggested that fugitive emissions from downstream oil refining and consumption of the transportation products should be deducted from the net CO2 stored by CO2-EOR projects. This presumes that these emissions (refining and consumption) are incremental to world aggregate oil-consumption emissions and would not occur if the EOR project was not executed. World oil production is determined by world oil demand and if CO2-EOR projects were not undertaken, some other source of oil would step forward and fill the gap. Therefore, executing CO2-EOR projects will not result in incremental aggregate refining and consumption emissions. When downstream-refining and product-consumption fugitive emissions are excluded from the calculation of project-life-cycle CO2-EOR storage, it is clear that CO2 EOR does result in net positive CO2 storage.