bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Field Study in Optimizing Completion Strategies for Fracture Initiation in Barnett Shale Horizontal Wells
Authors: Ketter A. A. , Heinze J. R. , Daniels J. L. , Waters G. 
Published: August 2008

Summary
The Barnett shale is an unconventional gas reservoir that currently extends over an estimated 54,000 sq miles. In an effort to improve well economics and to reduce the number of surface locations in populated areas, the number of wells being drilled and completed has rapidly increased. With this change in development strategy, operators and service companies alike have had to search for innovative solutions to overcome challenges faced in horizontal completions.
Inefficient fracture initiation is the largest reoccurring problem encountered when completing horizontal Barnett shale wells. These difficulties have manifested themselves as high-fracture initiation and propagation pressures, which lead to low injection rates and high treating pressures. These losses reduce the efficiency of proppant placement and stimulation. As drilling activity has increased over the past couple of years, fracture-initiation problems are now a substantial source of expense and downtime.
This field study examines 256 horizontal Barnett shale wells in an effort to identify the causes of these near-wellbore issues and to offer corrective solutions for future completions. The goal of this study is to recommend an optimized completion strategy to minimize these near-wellbore problems, increase stimulation coverage, and decrease unplanned completion expenses.
In 2005, 19% of the stages in horizontal wells examined encountered near-wellbore difficulties. This field study inspects the major contributors to fracture initiation, specifically focusing on cccemented vs. uncemented laterals, horizontal-stress anisotropy, perforation strategy, cementing strategy, and stimulation design.
The paper offers statistics on which changes have had the greatest effect on stimulation placement. These problems can cost operators an additional 25% per stage or more. Using these optimized strategies has reduced by 74% the number of stages in which fracture-initiation difficulties have been encountered.
Reaction of Gelled Acids With Calcite
Authors: Nasr-El-Din H. A. , Al-Mohammed A. M. , Al-Aamri A. D. , Al-Fuwaires O. 
Published: August 2008

Summary
Hydrochloric (HCl) acid is used to stimulate carbonate formations in both matrix and fracturing treatments. However, the reaction rate of the acid with calcite is fast. In addition, the viscosity of regular HCl solutions is relatively low. Acid-soluble polymers are usually added to the acid to increase its viscosity, which is needed to enhance acid diversion during matrix acidizing and reduce acid leakoff rate during acid fracturing. Gelled acids are extensively used in matrix and acid-fracturing treatments performed in carbonate formations. However, a few studies examined the impact of these polymers on the reaction of HCl acids with calcite.
This paper used a rotating disk instrument to measure the dissolution rate of calcite by use of gelled acids. Measurements were conducted over a temperature range of 25 to 65°C, a pressure of 1,000 psi, and rotational speeds of 100 to 1,000 rpm. Acid formulations that are typically used in the field were examined. Polymer concentration was varied from 0.5 to 2 wt%. The apparent viscosity of the gelled acid was measured with a Brookfield viscometer. Measurements were done for the same solutions tested with the rotating disk instrument. The temperature was varied from 25 to 100°C, while the pressure was maintained at 300 psi. The shear rate was varied from 57 to 1,700 s−1.
Evidence of reverse and toroidal flows was noted for the first time by examining the etching patterns of the reacted disks. The etching pattern on the surface of the disk depended, among other factors, on the disk rotational speed and polymer concentration.
There was a significant increase in the apparent viscosity of gelled acids and a major decrease in the dissolution rate as the polymer concentration was increased from 0.5 to 1.5 wt%. The reaction of gelled acids with calcite was controlled by a surface reaction at 25°C, and by mass transfer at 65°C. Temperature increased the dissolution rate of calcite at all conditions examined. It did also reduce the viscosity of the gelled acid, which affected the way the acid reacted with calcite.
Squeeze Chemical for HT Applications—Have We Discarded Promising Products by Performing Unrepresentative Thermal-Aging Tests?
Authors: Wat Rex , Hauge Lars-Even , Solbakken Kåre , Wennberg Kjell Erik , Sivertsen Linda Merete , Gjersvold Berit 
Published: August 2008

Summary
Selecting an effective scale inhibitor for squeeze application at 170°C is not a simple task. The traditional thermal-stability test of aging the chemical in bulk is often perceived to be too harsh. This results in many promising products being rejected because of their apparent degradation at temperature. The alternative of conducting the aging test inside core materials, which is more representative of the downhole conditions, is not a novel idea. However, to date, no definitive data are available to substantiate such a process and quantify the difference between the two methods. This is mainly because of the difficulties and complexity in conducting such an experiment at a high temperature over a long period of time. In this paper, the results from a recent investigation are presented. We describe the detailed procedures of the planning and execution stages, lessons learned, and pitfalls that must be avoided. A scale inhibitor was aged with two different methods: one in bulk, as commonly practiced in the industry, and one inside a sandstone core. The aging period varied between 45 days for the bulk and 110 days for the last desorbed sample from the core. The samples that were aged inside the core retained much of their inhibition efficiency, while those aged by the traditional method (bulk) lost nearly all their effectiveness. These results demonstrate clearly that the conventional method of thermal aging in bulk is unrepresentative and that the loss in performance can be quantified. A novel finding from this study is the evidence of an unexpected relationship between desorption and inhibition effectiveness. The findings from this study could have great impact on selecting chemicals for high-temperature (HT) applications, even more so in those environmentally sensitive regions where the use of "yellow" (biodegradable) squeeze chemicals is mandatory. Many of these chemicals have been rejected because of their apparent thermal degradation, which has now proved to be unrepresentative.
Production Optimization by Use of the Capillary Technology in the Loma La Lata Field
Authors: Cabral P. , Giérega C. R. , Costanza P. , Suriano A. A. 
Published: August 2008

Summary
Ever since its discovery in 1977, the Loma La Lata field, located in the Neuquén basin, has been considered one of the most important gas fields in South America.
During the last decade, the progressive reduction in the reservoir pressure has led to successive changes in the field's operation conditions: from high to medium pressure, and, most recently, to low pressure.
As the reservoir pressure depletes, the subsequent reductions in the gas velocities bring about changes in the flow regimes and increasing liquid flow rates. These liquids produced at the wellbore and/or generated by vapor condensation through the production string contribute to increase the pressure drop along the tubing as well as the flowing bottomhole pressure, and will eventually reduce or prevent production.
In most cases, not only does liquid loading arise as a consequence of these changes in operation conditions, but also other production problems, such as mineral scales and organic deposits, and the difficulty to implement corrosion prevention conventional batch treatment programs aimed at extending the life of the production strings.
In addition to these factors, the increasing hydrocarbon demand, Argentina's energy policy, and economic restrictions are also matters of relevance when it comes to implementing conventional solutions that imply several shutdown hours per treated well.
The aforementioned problems have encouraged the operating and services companies to search for technological alternatives providing not only technical solutions but also economical benefits.
After 1 year since a novel capillary string system that allows for the injection of chemical products, and/or the deployment of special devices such as memory gauges at the desired depth was introduced in the country, the results obtained in several tests show a very promising future.
This paper summarizes the first-year results achieved using the capillary string technology as a tool for production enhancement and optimization in the Loma La Lata field.
Lifting Liquids From Natural Gas Wells by Aggressive Formation of Small Droplets
Authors: Christiansen Richard L. 
Published: August 2008

Abstract
When initially completed, many natural gas wells are capable of lifting liquids to the surface. But, with depletion of the reservoir pressure, there comes a time when liquids can no longer be lifted to the surface and they begin to accumulate in the bottom of the well, dramatically inhibiting or stopping gas production. The cause of diminished liquid-lifting ability is the decline of liquid droplet production as gas flow rates pass below the Turner-Hubbard-Dukler critical velocity. In this research, a variety of devices were tested for enhancing droplet production and liquid lifting at low gas flow rates. The devices included vibrational, rotational, and two-fluid means for droplet production. Tests in a flow loop showed that the vibrational devices are most promising for commercial application. A correlation for droplet size as a function of frequency was extended for application at any frequency of interest. Tests with a flow loop show that 3 micron drops can be transported easily at low flow rates. Heuristics in the literature on droplet transport lead to the expectation that droplets with diameters less than 30 microns can be transported from the bottom of a well to the surface without significant difficulty. An energy analysis shows that a barrel of water can be converted to 30-micron droplets for 3 to 30 cents.
Lifestyle incongruity, stress and immune function in indigenous Siberians: The health impacts of rapid social and economic change
Authors: Sorensen Mark V. , Snodgrass James J. , Leonard William R. , McDade Thomas W. , Tarskaya Larissa A. , Ivanov Kiundiul I. , Krivoshapkin Vadim G. , Alekseev Vladimir P. 
Published: August 2008

AbstractThe purpose of this study was to investigate the impact of economic and cultural change on immune function and psychosocial stress in an indigenous Siberian population. We examined Epstein‐Barr virus antibodies (EBV), an indirect biomarker of cell‐mediated immune function, in venous whole blood samples collected from 143 Yakut (Sakha) herders (45 men and 98 women) in six communities using a cross‐sectional study design. We modeled economic change through the analysis of lifestyle incongruity (LI), calculated as the disparity between socioeconomic status and material lifestyle, computed with two orthogonal scales: market and subsistence lifestyle. EBV antibody level was significantly negatively associated with both a market and a subsistence lifestyle, indicating higher cell‐mediated immune function associated with higher material lifestyle scores. In contrast, LI was significantly positively associated with EBV antibodies indicating lower immune function, and suggesting higher psychosocial stress, among individuals with economic status in excess of material lifestyle. Individuals with lower incongruity scores (i.e., economic status at parity with material resources, or with material resources in excess of economic status) had significantly lower EBV antibodies. The findings suggest significant health impacts of changes in material well‐being and shifting status and prestige markers on health during the transition to a market economy in Siberia. The findings also suggest that relative, as opposed to absolute, level of economic status or material wealth is more strongly related to stress in the Siberian context. Am J Phys Anthropol, 2009. © 2008 Wiley‐Liss, Inc.
Behavioral adaptations to heat stress and water scarcity in white‐faced capuchins (Cebus capucinus) in Santa Rosa National Park, Costa Rica
Authors: Campos Fernando A. , Fedigan Linda M. 
Published: August 2008

AbstractWe examined thermoregulatory behaviors in a wild population of white‐faced capuchins (Cebus capucinus) inhabiting a highly seasonal dry forest in Santa Rosa National Park (SRNP), Costa Rica. The dry season in SRNP lasts ∼5 months and is characterized by high ambient temperatures regularly exceeding 37°C, low relative humidity, and the near absence of precipitation. This study demonstrates that capuchins rest more and travel shorter distances during the hottest and driest hours of the day, and suggests that they extend their tongues to lower body temperature via evaporative cooling. Seasonal weather patterns and group movement data reported here are based on 940 h of observations on three social groups of capuchins (wet season: 370 h, dry season: 570 h). In the dry season, the proportion of time spent resting increased at higher temperatures whereas the proportion of time spent traveling decreased. Distance traveled between location points taken at half‐hour intervals decreased significantly as temperature increased, although the correlation was not strong. Capuchins exposed their tongues during hot, dry, windy conditions, and this behavior was much more frequent in the dry season. Temperature was significantly higher and humidity significantly lower for “tongue‐out” events than expected for a random event in the dry season. Finally, as surface water became scarce, home‐range areas of heavy use became increasingly centered on the remaining permanent water sources. These results suggest that heat stress and water scarcity are significant influences on the behavior of capuchins in hot, dry conditions. Am J Phys Anthropol, 2009. © 2008 Wiley‐Liss, Inc.
Surnames in Siberia: A study of the population of Yakutia through isonymy
Authors: Tarskaia L. , El'chinova G.I. , Scapoli C. , Mamolini E. , Carrieri A. , Rodriguez‐Larralde A. , Barrai I. 
Published: August 2008

AbstractWe studied the isonymic structure of the Republic of Sakha (Yakutia), in the Russian Federation, using the surname distributions of 491,259 citizens above 18 years registered as residents in 2002. These were distributed in 35 districts and 497 towns and settlements of the Republic. The number of different surnames was 44,625. Matrices of isonymic distances between the 35 districts were tested for correlation with the geographic distance between the population centers of gravity of thedistricts. We found that, for the whole of Yakutia, Nei's distance was correlated with geographic distance (r = 0.693 ± 0.027). A dendrogram of the 35 districts was built from the distance matrix, using the UPGMA method. The clusters identified by the dendrogram correlate with the geographic position of the districts. The correlation of random inbreeding calculated from isonymy, FST, with latitude was positive and highly significant but weak (r = 0.23). So, inbreeding was highest in the Arctic districts, and lowest in the South. Average α for 497 towns was 107, for 35 districts it was 311, and for the Republic 433. The value of α was higher for Russian than for the local languages. The geographical distribution of α, high in the Center and South‐East and lower in the North‐West, is compatible with the settlement of groups of migrants moving from the South‐East toward the center and the North of Yakutia. It is proposed that low‐density demic diffusion of human populations results in high inbreeding and may have been a general phenomenon in the early phases of human radiations. Am J Phys Anthropol 2009. © 2008 Wiley‐Liss, Inc.
Adsorption for metal ions of chitosan coated cotton fiber
Authors: Zhang Guoyuan , Qu Rongjun , Sun Changmei , Ji Chunuan , Chen Hou , Wang Chunhua , Niu Yuzhong 
Published: August 2008

AbstractA kind of adsorbent for metal ions, cotton fiber coated by high loading of chitosan (SCCH) was prepared. Its structure was characterized by elemental analysis, scanning electronic microscopy (SEM), Fourier transform infrared spectrum (FTIR), and wide‐angle X‐ray diffraction (WAXD). The adsorption properties of SCCH for Cu2+, Ni2+, Pb2+, Cd2+, such as saturated adsorption capacities, static kinetics, and isotherm were investigated. The adsorption for Ni2+, Pb2+, and Cd2+ was controlled by liquid film diffusion, but by particle diffusion for Cu2+. The adsorption process for Cu2+, Ni2+, Cd2+ could be described with Langmuir or Freundlich equation, but only with Freundlich equation for Pb2+. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Properties of a poly(L‐lactic acid)/poly(D‐lactic acid) stereocomplex and the stereocomplex crosslinked with triallyl isocyanurate by irradiation
Authors: Quynh Tran Minh , Mitomo Hiroshi , Zhao Long , Tamada Masao 
Published: August 2008

AbstractA poly(L‐lactic acid) (PLLA)/poly(D‐lactic acid) (PDLA) stereocomplex was prepared from an equimolar mixture of commercial‐grade PLLA and PDLA by melt processing for the first time. Crosslinked samples were obtained by the radiation‐induced crosslinking of the poly(lactic acid) (PLA) stereocomplex mixed with triallyl isocyanurate (TAIC). The PLA stereocomplex and its crosslinked samples were characterized by their gel behavior, thermal and mechanical measurements, and enzymatic degradation. The crosslinking density of the crosslinked stereocomplex was described as the gel fraction, which increased with the TAIC content and radiation dose. The maximum crosslinking density was obtained in crosslinked samples of PLA/3% TAIC and PLA/5% TAIC irradiated at doses higher than 30 kGy. The stable crosslinking networks that formed in the irradiated PLA/TAIC substantially suppressed the segmental mobility for the crystallization of single crystals as well as stereocomplex crystals. The crosslinking network also significantly improved the mechanical properties and inhibited the enzymatic degradation of crosslinked PLA/3% TAIC. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008
In situ encapsulation of tetradecane droplets in oil‐in‐water emulsions using amino resins
Authors: Sgraja Martin , Blömer Jan , Bertling Jürgen , Jansens Peter J. 
Published: August 2008

AbstractMicrocapsules of tetradecane enclosed by a polymeric wall of amino resin were synthesized by the in situ polymerization using melamine‐formaldehyde precondensates. It was found that resin concentrations of 60–240 g L‐1 for a phase volume fraction of 0.14 and 0.29 and concentrations of 50–240 g L‐1 for a phase volume fraction of 0.43 lead to stable microcapsules. Furthermore, the dependence of the shell thickness from the resin concentration for a phase volume fraction of 0.29 was investigated whereas the shell thickness was calculated from the density and the mean diameter of the capsules. It was found that below a concentration of 100 g L−1 the density and thus the shell thickness increases linear with the resin concentration whereas at higher concentrations it almost remains constant and only the amount of the resin precipitated in solution increases. Additionally, it was shown that the mean droplet size (which is almost equal to the capsule size) in dependence of the stirring speed can be derived from the theory of droplet disruption. Thereby the coherence beginning with the stirring speed and the mean diameter to the total surface and the shell thickness is described. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Preparation of Carmustine‐loaded PLA ultrasmall‐nanoparticles by adjusting micellar behavior of surfactants
Authors: Yan Cheng‐hu , Yuan Xu‐bo , Kang Chunsheng , Zhao Yun‐Hei , Liu Jie , Guo Yanshuang , Lu Jian , Pu Peiyu , Sheng Jing 
Published: August 2008

AbstractCarmustine‐loaded poly(lactic acid) (PLA) nanoparticles were prepared with a spontaneous emulsification‐solvent diffusion method by using Pluroinc F68 as emulsifying agent, and the influence of micellar behavior of surfactant in aqueous solution on the sizes of the nanoparticles was studied. The results revealed that F68 dissolved as unimers in water or sodium acetate‐acetic acid buffer with pH value ranged from 5.0 to 5.5, resulting in larger PLA particles (226 nm) or clumps. In acidic media with pH of 4.0 and 4.5, however, F68 aggregated into micelles over the concentration of 3.7 and 4.8 mg/mL, as a result, ultrasmall nanoparticles with a size 50 and 80 nm could be obtained, respectively. The change in size had less effect on the drug content and entrapment efficiency, and the nanoparticles strongly enhanced the cytotoxic effect of the loaded drug in vitro, and this effect being more relevant for prolonged incubation times. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Stability studies on blends of a lactic acid‐based hot melt adhesive and starch
Authors: Inkinen Saara , Stolt Mikael , Södergård Anders 
Published: August 2008

AbstractThe stability of 70 : 24 : 6 w/w/w blends of a lactic acid‐based hot melt adhesive (LHM), oxidized potato starch (dried or nondried), and polyethylene glycol (PEG) was studied. Pure LHM was used as a reference material. The methods used included tensile testing, water absorption, and scanning electron microscopy (SEM). During the ageing period of 56 days at ambient conditions (23± 1°C and 42 ± 4% RH), the tensile properties of the blends were close to each other, and all of the studied materials had relatively low Young's moduli, compared to reported PLA‐starch blends. In the water absorption experiment (23 ± 1°C), the blends reached significantly higher maximum values than the LHM. The blends also started to disintegrate already after 3 days in water, while the water absorption of pure LHM could be studied for 49 days without detectable disintegration. The SEM images showed that the tensile testing fractures occurred via the continuous LHM matrix in the blends. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Encapsulation efficiency and release behaviors of bovine serum albumin loaded in alginate microspheres prepared by spraying
Authors: Zhang Jie , Li Xiaohui , Zhang Daijia , Xiu Zhilong 
Published: August 2008

AbstractSpraying and spraying with an electrostatic field (SEF) were employed to prepare alginate microspheres for delivering proteins, especially for intestinal digestive enzymes and cytokines. The encapsulation efficiency (EE) of a model protein [bovine serum albumin (BSA)] at a pH value lower than the isoelectric point was 20% higher than that at a natural pH. Moreover, for the microspheres prepared by SEF, EE improved significantly with increasing electric voltage. The interactions between BSA and the alginate microspheres were identified with Fourier transform infrared spectroscopy. The release profiles in vitro showed a controlled and pH‐responsive release manner for the encapsulated BSA. A first‐order release equation was postulated and modified to describe the release kinetics with an obviously initial burst release related to the eroded porous matrix. The equation fit the release data well when the pH value and composition of the release media were changed. The analysis of the release kinetics indicated that the drug release rate was in an inverse ratio to the diameter of the microspheres. Increasing the gas flow rate or electric voltage decreased both the mean diameter and size distribution of the microspheres significantly and enhanced the release rate of loaded drugs from alginate microspheres. Sodium dodecyl sulfate/polyacrylamide gel electrophoresis analysis revealed that BSA kept its structural integrity during the encapsulation and release process. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008