bluuebunny/crossref_metadata_2025 huggingface dataset:
A Unique, Large-Scale Computer Tomography Scanner: Investigation of Fracture Cleanup with Different Materials
Authors: Cheremisin Alexey N. , Zinchenko Alexey , Lecerf Bruno , Pavlova Svetlana , Thompson Karsten E. , Lane Nathan
Published: January 2011

Hydraulic fracturing is a widely used technique for production enhancement. One critical property of a hydraulic fracture is the fracture conductivity, which has a direct impact on the productivity and hence, the economics of the stimulated well. Several laboratory techniques have been developed to characterize the materials that are placed in the fracture and influence its conductivity. Conductivity laboratory measurements have become a routine experiment with well-established procedures and setups aimed at simulating downhole conditions. However, correlating the performance of materials in a conventional laboratory setup with their performance in real conditions is not straightforward. This problem occurs because conventional laboratory setups are of limited length scale and fail to capture processes and variations that occur at a scale of the order of, or exceeding, the dimensions of the conductivity cell. Also, even if conventional setups provide accurate and reproducible measurements, they fail to provide fundamental, in-depth understanding of the actual processes that occur at the pore scale, occur in the fracture, and influence the fracture conductivity.

A unique, large-scale X-ray computer tomography (CT) setup improves understanding of the factors influencing fracture conductivity. The state-of-the-art setup allows taking high-resolution scans of a proppant pack under conditions similar to an actual fracture. The setup provides unique insight into static and dynamic phenomena occurring at the proppant and the pore scale. The use of imaging software then provides an accurate 3D image over the entire length of the proppant pack. Computer models of flow in porous media can then be used to predict the flow and its parameters in the propped fracture and its porous network specified by the high-resolution images. Moreover, the setup scale (1 m long) is much larger than that of a conventional conductivity cell (20 cm long). The larger dimensions are adequate to capture heterogeneous processes such as fracture cleanup.

The performance of the new setup was validated using baseline proppant pack conductivity and non-Darcy flow coefficients experiments. An example was also shown where the unique X-ray CT setup was used for investigating fracture cleanup of new, elongated rod-shaped nondeformable high-strength proppant compared with conventional spherical proppant. The CT images show how the new proppant provides a better fracture cleanup compared with spherical proppant. For both cases, images showing the distribution of residual gel saturation highlight how pore volume geometry affects fracture cleanup.
Enhanced Reservoir Characterization Using Hydraulic Fracture Microseismicity
Authors: Maxwell S. C. , Cho D. , Pope T. , Jones M. , Cipolla C. , Mack M. , Henery F. , Norton M. , Leonard J.
Published: January 2011

Microseismic measurements were integrated with seismic reservoir characterization and injection data to investigate variability in the hydraulic fracture response between three horizontal wells in the Montney shale in NE British Columbia, Canada. When wells were close enough, hydraulic fractures were found to interact with pre-existing faults, which acted as a barrier to fracture growth, and resulted in relatively large-magnitude microseismicity. Pre-existing faults were identified by edge detection/ant tracking algorithms applied to seismic reflection data, as well as from advanced analysis of the microseismicity, including microseismic deformation levels, magnitude-frequency characteristics and composite failure mechanism analysis. In cases where the wells were far from pre-existing faults simple, planar hydraulic fractures were observed, although there was a tendency to grow towards regions of low Poisson’s ratio based on amplitude versus offset inversion of the seismic reflection data. The tendency for the hydraulic fractures to be asymmetric and grow preferentially towards the low Poisson’s ratio region is attributed to material property changes and associated lower stresses in these regions. Insight from the enhanced reservoir characterization with integrated microseismic and treatment data is being used for better well placement, improved completion designs and increased production.
Marcellus Shale Hydraulic Fracturing and Optimal Well Spacing To Maximize Recovery And Control Costs
Authors: Edwards Krisanne L. , Weissert Sean , Jackson Joshua , Marcotte Donna
Published: January 2011

EQT wants to maximize recovery and control development costs in its Marcellus shale development program, which consists of multi-stage fractured horizontal wells. To achieve this objective the asset team considered tighter well spacing. But at what distance do fracture-stimulated wells directly interact? Microseismic data implies that the radius of influence is greater than 1,000 ft. However, after 6 months of production, a study using a nodal analysis software model suggests an effective frac half-length less than half of this, a finding that has been supported in other EQT wells across Pennsylvania and West Virginia.

To test this concept for horizontal wells with multi-stage slickwater, sand-propped frac completions in the Marcellus shale—where well spacing is typically 1000-1200 ft—well spacing was reduced to just 500 ft, in three different areas of the Marcellus. The goal was to better understand: How do the hydraulic fractures interact? Are the closer spaced wells more likely to share reserves? Does the frac design need to be adjusted for tighter spaced wells?

To answer these questions, 500-ft and 1000-ft offset wells were monitored during completion with microseismic, radioactive tracers, chemical tracers, and pressure gauges. Production logging was initially scheduled to begin 4-6 months after production, however, had to be postponed.

With more than 6 months of production data in the first of the three development areas, the 500-ft-spaced wells and 1000- ft-spaced wells are performing similarly, despite frac communication during the completion of the 500-ft wells. Estimates of effective frac half-length from the nodal analysis model support this conclusion.

A unique, comprehensive data set is collected across the Marcellus shale to document how hydraulic fracturing influences well performance, and the study attempts to reconcile conflicting frac half-length interpretations to identify optimal well spacing. The results to date support tighter spacing, which maximizes recovery and facilitates multiple wells to be drilledfrom the same pad, thereby minimizing the footprint for "greener" operations.
An Alternative Interpretation of Microseismic Events during Hydraulic Fracturing
Authors: Dahi Taleghani Arash , Lorenzo Juan M.
Published: January 2011

It is common practice in industry to monitor hydraulic fracturing jobs by picking major, micro-earthquake events in seismograms whose source locations form a spatial pattern used for interpreting induced fractures. Surprisingly, controversy still surrounds the interpretation of these scattered, discrete events. Many authors conclude that hydraulic fractures are generated by shear failure events rather than tensile failures. This interpretation contradicts our common understanding of fracture mechanics, which describes the hydraulic fracture process as taking place predominantly in mode-I failure (pure tension). We propose that band-width limited instrumentation during seismic field recording may be partly to blame. Low-frequency (<;5 Hz) tensile-source events which are expected to occur continuously between shear events are largely ignored. Herein, we try to compare the total energy of detected shear events with the total energy of expected low-frequency tensile events in the background in order to justify the main (tensile) mechanism of fracturing. Major, shear-mechanism events may not describe accurately the temporal and spatial pattern of induced fractures in the subsurface. Shear events may only represent the locations where hydraulic fractures intersect pre-existing discontinuities. Therefore, by only considering shear events, we may not be able to make a correct estimation of the orientation and extension of the hydraulic fractures. We suggest that only by recording silent (low frequency) events, we will truly be able to describe induced subsurface fracture geometries.
Simulating Hydraulic Fracturing in Real Fractured Rocks - Overcjavascript:iterm()oming the Limits of Pseudo3D Models
Authors: Nagel Neal , Gil Ivan , Sanchez-nagel Marisela , Damjanac Branko
Published: January 2011

With the huge growth in the stimulation of naturally fractured formations, it is clear that the industry needs new hydraulic fracturing simulation tools beyond the limits imposed by pseudo3D fracturing model. Discrete element models (DEM), in which both matrix block behavior and fracture behavior are explicitly modeled, offer one option for the specific modeling of hydraulic fracture creation and growth in naturally fractured formation without, for example, the assumption of bi-planar fracture growth.

In this paper, we show the results of the successful realistic simulations of fluid injection into a given NFR using the 3DEC DEM model. The simulations included coupled fluid flow-deformation analysis, failure type and extent calculations, as well as a series of parametric analyses. The parameters investigated included: 1) injection rate and its effect on the overall injection results, and 2) fluid viscosity, which had a significant influence on the ratio of tensile (mode 1) failure versus shear failure.
Challenges of Designing Multi-Stage Frac Packs in the Lower Tertiary Formation - Cascade and Chinook Fields
Authors: Haddad Ziad , Smith Mike , De Moraes Flavio Dias
Published: January 2011

The Cascade and Chinook fields are located in the Gulf of Mexico (GOM), 250 miles south of New Orleans in ultra deepwater depths between 8200 ft and 8900 ft. The oil producing reservoir is in the Lower Tertiary Wilcox formation with a gross sand thickness of 1200 ft. The reservoir mid-point is at anaverage depth of 25, 600’ TVD with a bottomhole pressure of 19,500 psi and a bottomhole temperature of 260°F. The reservoir is comprised of vertically stacked thin beds of sand and fine grained siltstone intervals with effectively no vertical permeability. Additional information on this project can be found in a paper written by Moraes el al (2010).

Multiple limitations were considered during the initial design phase of the frac pack program. Thefracs were designed taking into account the use of a Single-Trip Multi-Zone sand control system. Although this system was not crucial in the overall implementation of the frac program, it added additional complexity from an operation stand point due to a continuous, multi-stage frac operation. Some ofthe operation limitations included service tool erosion limitations due to maximum pump rates and proppant volumes, overall frac vessel capacity, boat-to-boat fluid transfers and crew fatigue. The geological complexities of the reservoir were another major challenge in completing this very thick interval. Perforation intervals had to be placed to avoid a fault (and thus a potential early screenout), avoid a water contact, comply with tool spacing limitations and still maximize contact with net pay.

This paper addresses the approach taken to develop a fracture stimulation program for the Lower Tertiary formation in the Cascade and Chinook fields. Some of the major questions addressed during thisprocess include the following: how many fracture treatments are needed, what is the optimum fracture geometry, what is the desired conductivity, how to effectively position the perforation intervals, what is the desired pump rate and is a high-density fluid needed to fracture this deep, high- pressure formation? The approach, the answers and the treatment are discussed along with responses to additional questions that arose during the actual fracturing operations.

Along with the Lower Tertiary in the GOM, the industry faces similar challenges around the world. These include reservoirs with potentially large reserves but much lower permeability (due to depth and in-situ stresses) where fracturing is required for both stimulation and potential formation collapse sand control. Careful planning is necessary to avoid costly learning curves in these environments.
Life-Cycle Decline Curve Estimation for Tight/Shale Reservoirs
Authors: Ambrose Ray J. , Clarkson C. R. , Youngblood Jerry , Adams Rod , Nguyen Phuong , Nobakht M. , Biseda Brent
Published: January 2011

Low-permeability (tight) and shale (gas and oil) reservoirs have emerged as a significant source of energy in North America. Recent advances in technology, such as long horizontal lateral/multi-lateral drilling combined with hydraulic fracturing, and new surveillance techniques, have enabled commercial production from ultra-low permeability reservoirs, previously considered source or cap-rock, not reservoirs. Forecasting well production for reserves estimation, hydraulic fracture stimulation optimization, and development planning remains a challenge because of complex reservoir behavior and flow geometries associated with current wellbore architectures/stimulation treatments used to exploit tight formations. Depending on the completion design, transient flow periods can last for weeks to years, and hence traditional methods requiring boundary-dominated flow are strictly inapplicable for most of the commercial life of many wells completed in tight formations.

Recently, several analytical (type-curve, flow-regime analysis and simulation) and empirical approaches have been introduced to match and forecast tight reservoir production. The challenge is to develop routine techniques that can be used to forecast tight formation production, while adequately addressing the complex physics of the problem.

In this work, we build on recent attempts to combine analytical and empirical methods ("hybrid" methods) for forecasting tight/shale gas reservoirs completed with multi-fractured horizontal wells. We forecast the homogenous completion (equal hydraulic fracture length) case using established analytical procedures for transient linear flow (pre fracture interference), combined with the Arps decline curve for late-time (boundary-dominated) flow. We also examine the heterogeneous completion (unequal hydraulic fracture length) case to establish the impact of heterogeneities on decline characteristics post fracture-interference. Finally, we present an innovative method for designing hydraulic fracture and well spacing.
Gel Degradation Studies of Oxidative and Enzyme Breakers to Optimize Breaker Type and Concentration for Effective Break Profiles at Low and Medium Temperature Ranges
Authors: Sarwar M. U. , Cawiezel K. E. , Nasr-El-Din H. A.
Published: January 2011

Chemical breakers are used in hydraulic fracturing fluids to reduce the molecular weight of guar polymers which reduces fluid viscosity and facilitates the flowback of residual polymer providing rapid recovery of polymer from the proppant pack. Ineffective breakers or misapplication of breakers can result in screenouts or flowback of viscous fluids both of which can significantly decrease the well productivity.

Breaker activity of low to medium temperature range oxidative and enzymatic breaker systems was evaluated, including ammonium persulfate, sodium persulfate, calcium and magnesium peroxides, and galactomannanase enzyme in linear gel fluids at temperatures from 75 oF-300 °F. Low temperature and high temperature viscometers were used to generate linear gel- break curves with time at desired temperature. The amount of unbroken gel and residue, generated at different temperatures and breaker concentrations, was also determined using a "residue-after-break test (RAB)," for two oxidizers and one enzyme breaker, all used for similar temperature applications in the field.

Viscosity measurement showed that reduction in the gel viscosity depends on both the breaker concentration and temperature. Also, increasing breaker concentration does not necessarily mean more reduction in viscosity. This paper provides a guideline of oxidative and enzyme breaker optimum use concentrations for specific temperatures in the form of breaker activity "S" curves. Enzyme breakers were found to provide a more homogeneous break and generate less residue compared to the oxidztive breakers in the resdiue-after-break (RAB) tests.
Practical Data Mining: Lessons Learned from the Barnett Shale of North Texas
Authors: LaFollette Randy F. , Holcomb William D.
Published: January 2011

This paper documents a data-mining study of well, hydraulic fracture treatment, and production parameters for horizontal wells in the north Texas Barnett Shale play. In this study, the authors have analyzed well and production data from more than 13,400 producing Barnett wells. A subsample of over 3,300 horizontal wells was characterized with respect to detailed well architecture data such as drift direction and angle, lateral length, perforations, etc. The study uses Geographical Information System pattern-recognition techniques in conjunction with more traditional statistical techniques to interpret hidden trends in otherwise scattered data sets. This work provides a case study in the practical use of data-mining techniques to address questions of best practices in Shale Gas reservoirs. It is made possible because the availability and quality of public domain well and production data has increased significantly in the past few years. Simple cross plotting of production data against well and treatment variables normally leads to broad scattering of results. This study takes advantage of the largest, richest well and production data set available from the gas shales and identifies key lessons-learned. Relevant trends, such as the impact of toe up versus flat versus toe down, horizontal well length, and drift angle variability on gas production rate are presented. This work is significant in that it shows that the application of practical data-mining methods to a large Shale Gas data set can result in learning key lessons that may not be apparent when working with small data sets. This work is also significant in the use of merged reservoir quality proxies, well architecture data, completion data, and stimulation data, against which production results are placed in geographical perspective for improved interpretation.
Single Versus Multiwell Microseismic Recording: What Effect Monitoring Configureation Has On Interpretation
Authors: Seibel Margaret , Baig Adam
Published: January 2011

Three monitoring wells with permanently installed 3C geophones were used to locate the microseismicity induced from a steam production cycle. This dataset of 52 high signal-to-noise ratio events were used to examine the location of events by progressively decimating the number sensor arrays. The three-array solutions were contrasted with different array combinations achieved by turning off one or two of the arrays. Event locations revealed the nature and magnitude of the limitations having incomplete coverage of the treatment zone.

Most steam and fracture treatments are monitored by a single observation well. Parameters, such as stimulated reservoir volume fracture azimuth and fracture dimensions in treatments like CSS, hydraulic fracturing, SAG-D, are estimated from the distribution of microseismic event locations. By taking three array locations as ground truth, the array configurations that most accurately reflect the actual fracture geometry are determined.

The observed distributions of the events relocated with decimated arrays show significant changes in overall fracture trend, geometry, and location accuracy. Progressive decimation of the number of arrays increases the inaccuracies of event locations, which results in the scatter of event locations. Decimation of the number of arrays changes the dimensions and azimuth of fractures, which are readily apparent upon comparison with the three-array solutions. The least biased decimated solutions are those using two arrays, one on either side of the treatment zone. Single array solutions show the most scatter, with the recording distance also controlling the degree of event mislocation.

This array decimation analysis shows how the array configuration and number for arrays affect the interpreted fracture volumes, geometries, and accuracy of event location. The different viewing angles from the single and dual array decimated subsets, as well as the different distances from the event clusters to the geophones are important considerations in mitigating the biases due to limiting the recording coverage.
Soft Rock Fracturing Geometry And Failure Mode In Lab Experiments
Authors: Olson Jon E. , Holder Jon , Hosseini S. Mehran
Published: January 2011

Hydraulic fracturing of uncemented sand was investigated with theoretical calculations and physical laboratory experiments to investigate crack tip mechanics for soft rock applications. The mechanics of soft rock fracturing is an important topic for the better understanding of injection operations in weakly or unconsolidated sands. Fracpack treatments, waste injection, and steam injection for heavy oil recovery are all applications for which the application of standard elastic hydraulic fracturing models may be inadequate due to expected nonelastic deformation components.

Analytical calculations indicate that shear associated with hydraulic fracturing is likely in unconsolidated sands at depth, but cases of high overpressure promote tensile mode fracturing. An expression is derived to predict the rock strength required in terms of UCS to achieve tensile fracture. Preliminary physical experiments were performed to ascertain failure mode in uncemented sand at low confining stress and to investigate shear failure under high viscosity injection. Physical specimens were created using sand ranging from 100 to 300 micron in diameter, compacted with wet vibration. Preliminary fracture opening experiments performed using solid wedging were imaged with a CT-scanner and demonstrated near-tip shear failure propagating diagonally away from the crack tip, but not along the in-plane propagation direction. Injection experiments indicated complex fracture propagation geometries involved fracture plane segmentation and curving. Preliminary results indicate fracture propagation mode is predominantly tensile and not shear, although deformation in the vicinity of the hydraulic fracture showed evidence of shear. Higher stress anisotropy is anticipated to increase the likelihood of shear failure over tensile failure.
Design of Multiple Transverse Fracture Horizontal Wells in Shale Gas Reservoirs
Authors: Song Bo , Ehlig-Economides Christine , Economides Michael J.
Published: January 2011

The game changing technology enabling economic natural gas production from shale is the multiple fracture well (MFTW), a horizontal well with multiple transverse fractures. The well itself can create a stimulated reservoir volume (SRV) that delineates sufficient gas reserves to payout the well and provide continued return for several decades. This paper shows the importance of permeability and adsorbed gas in ensuring a well design that will achieve these objectives.

In this paper we base decisions about the number and size of fractures and the horizontal well length (and therefore the fracture spacing) first on the physics of production and then on investment economics. Current practices using a repetitive well template applied to all wells in a given shale gas play result in some wells doing far better than expected while others barely pay out. We show that linear flow is likely to dominate production behavior until pressure interference occurs between adjacent fractures and that the time of inter-fracture interference predicted by linear flow pressure penetration is prolonged by desorption.

The shale permeability and the adsorbed gas parameters are used to design an economically successful well while ensuring at least 50% gas recovery in the SRV within a specified period of time. Field data from several shale gas formations are used to provide examples of the well design approach. The gas adsorption characterization typically comes from laboratory analysis, which we use to develop what we have called the adsorption index. Because the gas recovery factor depends on lowering the average pressure in the SRV, permeability and the adsorption index are used to estimate the time of inter-fracture interference, which in turn indicates the optimal spacing between fractures. This paper provides insights on the effective exploitation of a shale gas reservoir by optimizing the fracture and well architecture.
Integration of Production Analysis and Rate-Time Analysis via Parametric Correlations — Theoretical Considerations and Practical Applications
Authors: Ilk D. , Rushing J. A. , Blasingame T. A.
Published: January 2011

Well performance analysis in unconventional reservoirs is a challenging task because of the non-uniqueness associated with estimating well/formation properties. In addition, estimation of reserves is often uncertain due to very long transient flow periods. Recently, new semi-empirical rate-time relations (Ilk et al. 2008 and 2010) have been shown to properly model the rate-time behavior for wells in unconventional reservoirs. The success of these new rate-time relations has led us to focus on finding theoretical and empirical relationships between rate-time model parameters with well/formation properties.

This work attempts to integrate model-based production analysis (i.e., semi-analytical/analytical solutions) and rate-time analysis by using parametric correlations. We perform production analysis and rate-time analysis for various tight gas and shale gas wells, and then correlate the various model parameters from the rate-time equations with the well/formation properties estimated using full (model-based) production data analysis.

We demonstrate the application of the proposed methodology by using a sample of wells producing in tight gas and shale gas reservoirs. We can show that the integration of production analysis and rate-time analysis via parametric correlations is highly-dependent on the size of data sample (i.e., the number of wells) and the data quality. When high-quality data and ample production data are available, formation permeability and fracture half-length are well-correlated with the model parameters of the rate-time relations.
First Downhole Application of Distributed Acoustic Sensing (DAS) for Hydraulic Fracturing Monitoring and Diagnostics
Authors: Molenaar Mathieu M. , Hill David , Webster Paul , Fidan Erkan , Birch Bill
Published: January 2011

The first E&P downhole field trial of Distributed Acoustic Sensing (DAS) fibre optic technology was conducted by Shell Canada during the completion of a tight gas well in February 2009.

DAS is a novel technology that allows the detection, discrimination and location of acoustic events on a standard telecom single-mode fibre of several kilometres in length. Using a combination of the measurement of backscattered light and advanced signal processing, the DAS interrogator system segregates the fibre into an array of individual "microphones". To date the technology has been mainly applied in the defense and security industries. One of the most exciting applications for downhole application of DAS is in the area of hydraulic fracturing of tight sand and shale gas reservoirs. Balancing the cost of hydraulic fracture stimulation versus the production benefit is crucial in a tight sand and shale gas developments as, after drilling costs, the completion is the largest single cost component of the well.

Recordings were made while tools were run in hole, bridge plugs set, perforations shot and during the fracture stimulation treatment(s). The technology proved sufficiently reliable and sensitive to detect and monitor these in-well activities. The fidelity of the recordings made during hydraulic fracturing and flow back operations, provided a step-change improvement in the ability to perform real-time and post-job diagnostics & analyses of the stimulation.

The different case studies presented in this paper will illustrate how, even in its earliest form, DAS has the potential to enhance the capability of monitoring and understanding in-wellbore activities. The technology enables the optimization of hydraulic fracturing design and execution, which could drive down completion costs and lead to increased well productivity and ultimate recovery.
Experimental Validation of Microseismic Emissions from a Controlled Hydraulic Fracture in a Synthetic Layered Medium
Authors: Roundtree Russell , Miskimins Jennifer L.
Published: January 2011

Experiments using acoustic sensors to monitor stress changes and hydraulic fracture propagation in moderate size, layered rock samples are described in this paper. The results show that microseismic event locations closely follow the actual growth of the hydraulic fracture, especially near the well bore. More events are detected and localized near the acoustic transducers indicating that signal attenuation is significant. In the work performed, event location based on automated picking techniques is not yet accurate enough to make diagnostic conclusions about fracture propagation near and through the different layered materials. Advanced processing techniques being developed in industry may well have the additional resolution necessary to focus some of these more subtle events at the laboratory scale. The conducted experiments indicated that controlling hydraulic fracture growth in laboratory-sized samples is difficult in small and moderate sized samples, and dynamically changing flap jack pressures, and injection rates and pressures is mandatory to slow the fracture growth for proper analysis once it has initiated. A key outcome of the work is the recognition that rocks emit substantial amounts of acoustic energy when stressed at incremental pressure levels of only a few psi, which corroborates a model of rocks as being meta-stable materials and explains frequently observed field phenomena. Further advancements in the use of acoustic monitoring at the laboratory scale are warranted and significant breakthroughs are possible for non-invasive investigations of solid and layered materials under stress.
Advancements in Efficiency in Horn River Shale Stimulation
Authors: Demong Karl , Hands Ron , Affleck Brad
Published: January 2011

In the remote Horn River Shale of North East British Columbia, Canada the key challenge operators’ face is high costs related to completions in the horizontal wells. A strategy was developed to focus on efficiency improvements to make a positive impact on the economics. Previous projects were examined and a two prong approach was developed: first we needed to procure as many extra resources as could be anticipated to ensure continuous operations, and second we would have to have more than one critical path operation simultaneously so that costly activities could continue uninterrupted.

The resource planning includes the drilling of multiple wells on the pad and having most of the wells available for operations during the stimulation campaign. It also includes specially designed equipment such as bulk sand handling equipment, water handling, slurry handling, wellhead protection, SCADA systems and custom flow back equipment. In addition, new ways of managing the human resources at the site were implemented. To manage the critical path activities, a protocol was developed to manage surface and down hole interactions. A safety system was developed to support the integration of these challenging operations. An offsite real time operations room was employed were all the sensor data from the site was available, including frac data, water and sand supply, pressure and H2S.

The resulting impact on efficiency will be discussed in detail, including reaching a field frac efficiency record for the Horn River.
Analysis of Differentially Expressed Genes in LNCaP Prostate Cancer Progression Model
Authors: Xie Bang‐Xiang , Zhang Hui , Wang Jian , Pang Bo , Wu Rui‐Qin , Qian Xiao‐Long , Yu Lan , Li Shan‐Hu , Shi Qing‐Guo , Huang Cui‐Fen , Zhou Jian‐Guang
Published: January 2011

ABSTRACT: The LNCaP/C4‐2 human prostate cancer progression model was established to mimic phenotypic and genotypic changes during prostate cancer development from androgen dependence to androgen independence, from nonmetastasis to metastasis. In this study, cDNA microarrays were performed using a microarray chip from Affymetrix to characterize and compare gene expression profiles in LNCaP and C4‐2, which may provide novel insight into the molecular mechanism mediating prostate cancer progression. Three hundred eighteen genes consistently exhibited differential expression in LNCaP and C4‐2 in 2‐time microarray data. Based on their function, the differentially expressed genes can be grouped into several subcategories, including growth factors and signal transducers, oncogenes and tumor suppressors, tumor‐specific antigens, transcriptional factors, transporters, and factors involved in invasion, metastasis, and metabolism. Some genes are novel and unexplored in prostate cancer progression and are of potential interest for follow‐up investigation. Reverse transcription–polymerase chain reaction (RT‐PCR) and real‐time RT‐PCR were performed to corroborate the microarray results, and 76 differentially expressed genes were validated out of 104 candidates. Expression pattern analyses were performed in these 76 differentially expressed genes, and a series of genes was found to be positively or negatively correlated to prostate cancer progression in the LNCaP prostate cancer progression model and to possess predominant prostate cell specificity. ELF5/ESE‐2b and long‐chain acyl coenzyme A dehydrogenase (ACADL) expressions were found to be positively associated with malignant progression in LNCaP, C4‐2, and C4‐2B, and predominantly expressed in prostate cancer cells. Functional evaluation revealed that ELF5/ESE‐2b and ACADL expressions contributed to the malignant phenotypes of prostate cancer cells. Accordingly, our microarray data may provide clues for finding novel genes involved in prostate cancer progression to androgen independent and metastasis, and shed light on finding new targets for diagnosis and therapy of prostate cancer.
The Evaluation of Saphenofemoral Insufficiency in Primary Adult Varicocele
Authors: Koyuncu Hakan , Ergenoglu Mehmet , Yencilek Faruk , Gulcan Nilay , Tasdelen Neslihan , Yencilek Esin , Sarica Kemal
Published: January 2011

ABSTRACT: The aim of this study was to evaluate the possible relationship between varicocele and saphenofemoral insufficiency in patients diagnosed with primary varicocele. A total of 70 patients with the primary diagnosis of varicocele were included into the study. A total of 30 age‐matched healthy adults were also included in the study as a control group. Varicocele was diagnosed by palpation and observation of each spermatic cord in standing position before and during a valsalva maneuver. Additionally, scrotal Doppler and lower extremity venous Doppler ultrasonography were performed. Patients who were with spermatic varicose vein larger than 3.0 mm were included in the study group as a varicocele patient. At the lower extremity venous Doppler ultrasonography, a retrograde flow lasting longer than 0.5 seconds during normal breathing or at the valsalva maneuver was considered to be meaningful for saphenofemoral junction insufficiency. Thirty‐six (51.35%) patients had insufficiency in saphenofemoral junction in the study group (6 [8.5%] bilateral, 30 [42.85%] unilateral) whereas 8 (26.6%) had insufficiency in the control group (2 [6.6%] bilateral, 6 [20%] unilateral insufficiency). The patients with primary varicocele had a statistically significant (P = .02) higher rate of venous insufficiency in their saphenofemoral junctions when compared with the control group. In the present study, the rate of saphenofemoral insufficiency has been found to be statistically higher in patients with primary varicocele compared with healthy men. Depending on the common presence of valvular insufficiency, we believe that the presence of varicocele should be investigated in the young population suffering from saphenofemoral junction insufficiency.
The Exposure of Urologists and the Treatment for Male Factor Infertility on the Web Sites of ART Centers in Taiwan
Authors: Hsiao Fu‐Yin , Huang William J. , Chen Kuang‐Kuo
Published: January 2011

ABSTRACT: Couples with male factor disorders can have their own biologic offspring nowadays via in vitro fertilization or intracytoplasmic sperm injection technologies. Because infertile couples commonly seek treatment options through public Web sites on the Internet, an appropriate exposure of urologic opinions on male factor infertility is important. It was therefore of interest to survey the extent of urologists' exposure on the official Web sites of the assisted reproductive technology (ART) centers. We surveyed the official Web sites of all 74 qualified ART centers in Taiwan. Web sites of these centers were evaluated for their information on male factor infertility and varicoceles, especially treatment suggestions for varicocele and attitudes toward urologist referral. Among the 74 centers, only 69 had established official Web sites. Forty‐eight Web sites (69.6%) provided information regarding infertility, whereas only 42 Web sites (60.9%) mentioned male factor infertility and 23 (33.3%) had descriptions of varicoceles. The quantity and quality of disclosed information varied, 11 (15.9%) sites provided treatment opinions for varicocele, and only 4 (5.8%) supported surgical intervention. Most Web sites of ART centers in Taiwan had content on male factor infertility, but the vast majority did not mention urologist referral or varicocele treatment. Urologists' opinions are relatively less exposed on the Web sites of fertility services. Further efforts should be made by urologists to provide comprehensive information to the public and to reinforce the importance of urologist referral in male factor infertility.
Increased Risk of Benign Prostatic Enlargement Among Patients With Liver Cirrhosis: A Nationwide Population‐Based Study
Authors: Chung Shiu‐Dong , Lin Herng‐Ching
Published: January 2011

ABSTRACT: There have been several post mortem studies focusing on the association between liver cirrhosis and benign prostate hyperplasia; however, the results are controversial. The aim of this study was to estimate the risk of benign prostatic enlargement during a 5‐year follow‐up period following a liver cirrhosis diagnosis, using nationwide population‐based data and a retrospective cohort design. We used the “Longitudinal Health Insurance Database,” derived from the Taiwan National Health Insurance program. The study cohort comprised 661 patients who had received treatment for liver cirrhosis between 1997 and 2001; the comparison cohort was composed of 3305 randomly selected patients. Stratified Cox proportional hazard regressions were performed as a means of comparing the 5‐year benign prostatic enlargement survival rate for the 2 cohorts. Of the sampled patients, 808 patients (20.4%) developed benign prostatic enlargement during the follow‐up period (ie, 163 individuals from the study cohort [24.7% of the patients with liver cirrhosis] and 645 individuals from the comparison cohort [19.5% of comparison cohort patients]). The log‐rank test indicated that patients with liver cirrhosis had significantly lower 5‐year benign prostatic enlargement–free survival rates than the controls (P < .001). The adjusted hazard ratios for benign prostatic enlargement following diagnosis with liver cirrhosis were 1.41 during the 5‐year follow‐up period. We conclude that the risk for benign prostatic enlargement increased after a diagnosis of liver cirrhosis. Further studies are needed to identify the underlying pathophysiology.
Determination of Kinetic Parameters for Enzymatic Cellulose Hydrolysis Using Hybrid Differential Evolution
Authors: Chen Yu-Ting , Wang Feng-Sheng
Published: January 2011

A kinetic model could provide a dynamical description of mechanism in that it is required for analysis, design, optimization and control. Temperature and pH could affect the cellulose activity. In this study, we have introduced the kinetic model, which includes temperature and pH effects, to describe dynamic behaviors of the enzymatic hydrolysis of cellulose to glucose. A commercial enzyme was applied to the hydrolysis process. Various batch time-series observations were collected and used to estimate the model parameters of the kinetic model. Hybrid differential evolution with a geometric mean mutation was applied to determine optimal estimates, and then such estimates were used as the initial starting for a gradient-based method to obtain the refined solution. The approach is capable of predicting the dynamic behaviors of the cellulose hydrolysis process as observed extra experimental validations. Furthermore, the time-average sensitivities were applied to evaluate accuracy and robustness of the mathematical model.
Non-aqueous titrimetric assay of gabapentin in capsules using perchloric acid as titrant
Authors: Abdulrahman Sameer , Basavaiah Kanakapura
Published: January 2011

Two simple, rapid, accurate and inexpensive methods using visual and
potentiometric titrimetric techniques are described for the determination of
gabapentin (GBP) in bulk drug as well as in capsules. The methods are based
on the neutralization reaction of the primary amino group of GBP with acetous
perchloric acid as titrant in anhydrous acetic acid medium. The end point was
detected either visually using crystal violet as indicator or
potentiometrically using modified glass electrode SCE electrode system. Both
methods are applicable over the range 1.0-16.0 mg of GBP and the titration
reaction follows a 1:1 stoichiometry. The methods were successfully applied
to the determination of GBP in capsules. The validity of the proposed methods
was further ascertained by parallel determination by a reference method and
by recovery studies via standard-addition technique.
Design, synthesis and antibacterial activity of new phthalazinedione derivatives
Authors: Khalil El-Galil , Berghot Moged , Gouda Mostafa
Published: January 2011

Dibenzobarrelene (1) was utilized as the key intermediate for the synthesis
of some new 2-substituted (1,4-dioxo-3,4,4e,5,10,10ahexahydro-
1H-5,10-benzeno-benzo[g]phthalazine: 2, 5a-d, 8a-c and 10. Condensation of 2
with benzaldehyde or anisaldehyde gave the corresponding acrylonitrile
derivative 3a, b, respectively. Thiophene derivatives 4a, b were obtained via
the Gewald reaction of 2 with cyclohexanone or pentanone, respectively.
Treatment of 5d with acetyl chloride or p-toluenesulfonyl chloride afforded
the corresponding esters 6, 7, respectively. Cyclization of 8a-c with
formalin afforded the corresponding triazine derivatives 9a-c. Ring opening
of 10 with sodium hydroxide gave the corresponding triazole derivative 11,
which when alkylated with pentyl bromide afforded the pentylsulfanyl
derivative 12. Representative compounds of the synthesized products were
established and evaluated as antibacterial agents.
The Origin of Abandon and Random
Authors: Diensberg Bernhard
Published: January 2011

The Origin of Abandon and Random

Modern English ban and related lexemes will be shown to have their origin in common with abandon, the latter of disputed etymology. This applies to a still greater extent to random, for the origin of which a plausible solution will be presented. A last paragraph is devoted to the etymology of Modern English PLAN.
Teaching Punctuation in Early Modern England
Authors: Rodríguez-Álvarez Alicia
Published: January 2011

Teaching Punctuation in Early Modern England

Much has been written on the punctuation practice of late sixteenth- and seventeenth-century English writers in order to work out the ultimate function of marks of punctuation. The main point of discussion has almost ever been whether punctuation indicated syntactic relationships or represented speech pauses either to give emphasis in oral delivery or just to be able to breathe. The focus of this paper, however, is the theory rather than the practice, in particular, the set of rules and conventions used by schoolmasters to guide students in their use of stops. Thus, textbooks used at the time to teach reading and writing will constitute our main sources of information to achieve the following aims: (i) to offer a classification of the different marks of punctuation described, (ii) to establish the functions schoolbooks assigned to punctuation marks in general, and (iii) to assess the importance schoolmasters gave to pointing. The results of this study - which follows the works by Ong (1944) and Salmon (1962, 1988) - will contribute to shed light on the ever-lasting debate on the principles guiding Early Modern English punctuation usage.
The Bases of Derivation of Old English Affixed Nouns: Status and Category
Authors: Torres Elisa
Published: January 2011

The Bases of Derivation of Old English Affixed Nouns: Status and Category

The aim of this journal article is to carry out a complete analysis of the category, status and patterns of the bases of derivation of Old English affixal nouns. The results of the analysis are discussed in the light of the evolution from stem-formation to word-formation. The corpus of analysis of this research is based on data retrieved from the lexical database of Old English Nerthus, which contains 30170 predicates. 16694 out of these are nouns, of which 4115 are basic and 12579 qualify as non-basic. Within non-basic nouns there are 3488 affixed nouns (351 by prefixation and 3137 by suffixation) and 9091 compound nouns. The line of argumentation is that, under certain circumstances, the existence of more than one base available for the formation of a derivative does not reinforce the explanation of invariable bases; on the contrary, it goes in the direction of variable bases produced by inflectional processes and made ready for derivation. The following conclusions are reached. In the first place, the importance is underlined of formations on stems in Old English, involving, at least, nouns. Secondly, the analysis evidences that the importance of stem-formation in Old English might be higher than has been acknowledged by previous studies. If Old English made extensive use of words as bases of derivation, a single base should be available; if, on the contrary, Old English is still dependent on stem-formation, more than one base is likely to be found for a single derivative. Such alternative bases of derivation reflect stemformation that may result from inflectional means and be eventually used for derivational purposes.
Measuring Specificities of Dissipation Factor of Electrical Equipment in Substations
Authors: Gavrilovs Gerards , Vītoliņa Sandra
Published: January 2011

Measuring Specificities of Dissipation Factor of Electrical Equipment in Substations

Measuring techniques of dielectric losses tanδ of high voltage equipment are discussed and compared in this paper. There are several methods for determining tanδ and capacitance values in high voltage substation on site.

Simple measuring methods like GST and UST can be put into practice without result corrections in ideal conditions. However electrical field in substation originates negative affect on measuring results, therefore different connection schemes of measuring methods have to be used.