bluuebunny/crossref_metadata_2025_split huggingface dataset:
Crestal Bone Changes at Teeth and Implants in Periodontally Healthy and Periodontally Compromised Patients. A 10‐Year Comparative Case‐Series Study
Authors: Rasperini Giulio , Siciliano Vincenzo Iorio , Cafiero Carlo , Salvi Giovanni E. , Blasi Andrea , Aglietta Marco 
Published: November 2013

Background: Limited data exist on the longitudinal crestal bone changes around teeth compared with implants in partially edentulous patients. This study sought to compare the 10‐year radiographic crestal bone changes (bone level [BL]) around teeth and implants in periodontally compromised (PCPs) and periodontally healthy (PHPs) patients.Methods: A total of 120 patients were evaluated for the radiographic crestal BL around dental implants and adjacent teeth at time of implant crown insertion and at the 10‐year follow‐up. Sixty patients had a previous history of periodontitis (PCPs), and the remaining 60 were PHPs. In each category (PCP and PHP), two different implant systems were used. The mean BL change at the implant and at the adjacent tooth at the interproximal area was calculated by subtracting the radiographic crestal BL at the time of crown cementation from the radiographic crestal BL at the 10‐year follow‐up.Results: At 10 years after therapy, the survival rate ranged from 80% to 95% for subgroups for implants, whereas it was 100% for the adjacent teeth. In all eight different patient categories evaluated, teeth demonstrated a significantly more stable radiographic BL compared with adjacent dental implants (teeth BL, 0.44 ± 0.23 mm; implant BL, 2.28 ± 0.72 mm; P <0.05). Radiographic BL changes around teeth seemed not to be influenced by the presence or absence of advanced bone loss (≥3 mm) at the adjacent implants.Conclusions: Natural teeth yielded better long‐term results with respect to survival rate and marginal BL changes compared with dental implants. Moreover, these findings also extend to teeth with an initial reduced periodontal attachment level, provided adequate periodontal treatment and maintenance are performed. As a consequence, the decision of tooth extraction attributable to periodontal reasons in favor of a dental implant should be carefully considered in partially edentulous patients.
Magnetic Resonance to Identify Permeability in Shale Reservoirs
Authors: Smith Charles H. , Ramakrishna Sandeep , Bray Jim 
Published: November 2013

Abstract
Unconventional reservoirs require a rigorous set of decision principles to achieve cost-effective and efficient completions. The oilfield definition of "unconventional reservoirs" includes any that exhibit permeability in the 0.01 md and tighter range. These permeability definitions become very tight as the reservoir includes a greater component of shale. Ultimately, shale resource reservoirs have permeability in the nanodarcy range, several orders of magnitude less than other unconventional resources.
Nuclear magnetic resonance (NMR) relaxation, or T2 measurement, has been used to establish permeability by direct application of the Bray-Smith permeability. There have been numerous comparisons of these permeability calculations to laboratory permeability and production rates. These comparisons have included wells in the unconventional range. The results have been quite favorable.
This paper explores the possibility that this calculation of permeability can be extended from the millidarcy to the nanodarcy range, proving useful in shale reservoirs worldwide. The basis of work was accomplished by comparing NMR results to laboratory core results. Additional refinement to the changes of calculation was performed using comparison to production rates from wells in the study.
The results illustrate the changes required to derive a useful solution of permeability directly from the NMR data in these shale reservoirs. A comparison of core results to this calculated permeability is also included.
Challenges of Refracturing Horizontal Wells in Unconventional and Tight Reservoirs
Authors: Strother David , Valadares Rodrigo , Nakhwa Amit D. , Pitcher Jason 
Published: November 2013

Abstract
The use of horizontal wells and multistage fracturing that is currently common in unconventional reservoirs first became popular during the early 2000s. Since then, the effectiveness and efficiency of horizontal wells has continued to be recognized. Because of the large number of these horizontal wells, significant opportunities for refracturing exist. Restimulation of these wells can allow the operator to increase production, as well as recoverable reserves, generally more economically than by installing new laterals or by infill drilling. An important challenge in refracturing these wells is to understand the rock system in which the well and the hydraulic fracture system are placed.
The major hurdle for net returns on any restimulation is effective candidate selection. This process involves not only choosing the right well, but also choosing the best zones within that well. Often, either a well (or zone) has not produced adequately or has been prolific and is in decline. However, there is no model that can predict production as accurately from unconventional reservoirs as from conventional ones. There are, however, measurable parameters that, when analyzed together, can indicate the relative potential of one zone to another. Therefore, to perform this analysis, any available data on the reservoir should be gathered. Then, well diagnostics are run to fill in the inevitable gaps in these data.
This paper discusses using a novel combination of cased-hole logging tools to gather these data. Using this combination to log the well after the first hydraulic fracturing treatment, the optimum restimulation candidate(s) can be determined. Then, whether to use existing perforation locations or to perforate new areas to cover non-stimulated rock can be decided; thus, optimizing the refracturing process. This selectivity of both candidates and zones during the refracture design can save time, costs, and resources, increasing the economic efficiency of the operation.
Coal Fractures and Present-Day Stress: Integration of Borehole Images and Sonic Anisotropy, Bowen and Surat Basins, East Australia
Authors: Halwa Leon , Donald Adam , Jones Anthony 
Published: November 2013

Abstract
Operators in the Bowen and Surat basins commonly use borehole images and to a lesser degree acoustic anisotropy to infer permeability anisotropy for use in field development; however it is not until now that other information from these technologies are fully unified to have potential to predict permeability. An ongoing challenge in these wells is to understand coal fractures and their relationship to present-day stress, as these geological factors define the permeability and ultimately production.
Borehole images are used to identify near-wellbore fracture discontinuities / fractures (coal cleats, tectonic fractures, and drilling-induced fractures), which can show a high density with a wide variation in azimuth. The polarization direction of the fast shear from borehole sonic logs will be a result of the dominant mechanism of stress and fractures in the far field; which is a net result of both fractures and present-day stress. It is uncertain, however whether the anisotropy is dominated by coal fractures or in-situ stress.
An improved method to characterize the complex relationship between fracture discontinuities and stress anisotropy has been applied to define the dominant mechanism. Orientations of coal fractures (cleats, tectonic fractures, and drilling-induced features) from near-wellbore imaging are combined and used to predict the far-field shear anisotropy direction from borehole sonic, and a comparison is made to the fast shear azimuth. Discrepancies between the direction of the fast shear and the fracture directions are then used to understand the net effect of fractures and present-day stress.
Preliminary results from comparing the anisotropy direction with the directions of stress and fractures in the study have shown that where anisotropy direction matches the fracture direction, there was lower permeability compared to when the anisotropy matches the maximum stress direction. Stress-dominated anisotropy, and in particular coals with a net contribution from both stress and fractures, showed higher permeability.
CBM Development in the Qinshui Basin: Hydraulic Fracture Complexities Revealed by Modeling Analysis and Microseismic Monitoring
Authors: Wu Jianguang , Sun Hansen , Liu Xinghui , Mayerhofer Mike , Zhang Ping , Wu Xiang , Zuo Jingluan 
Published: November 2013

Abstract
The Qinshui basin covers an area of approximately 42,000 km2 with coal resources and is one of the important regions for coal production and coalbed methane (CBM) exploitation in China. There are two major coalbeds that are important for CBM development. These coalbeds are laminated among sand, shale, and limestone formations and are located approximately from 200 to 1100 m in depth across the basin, with an average thickness between 3 and 6 m. This paper presents a case history of fracture evaluation for a CBM development project in the basin. In this study, fracture growth behavior was evaluated using fracture modeling and microseismic monitoring techniques. The instantaneous shut-in pressure (ISIP) for some treatments in the area of this study was well above the formation overburden stress. Closure stress obtained from diagnostic injection tests was high but lower than the overburden stress. Microseismic mapping results indicated significant fracture complexities, ranging from both confined and excessive height growth to asymmetric fracture growth and multidirectional fracture growth. An abundance of microseisms were detected, but most of them were located in the brittle sand and shale formations below and above the target coalbed. The complex fracture growth is believed to be caused by complex stress regimes and geologic settings in the study area. Fracture closure stress analysis from offset wells confirmed that stress variation was the primary reason for asymmetric fracture growth. Fracture modeling revealed that viscous fluids provided better fracture conductivity in the target coalbed than KCl water, as most proppant would settle below the target coalbed because of the poor transport capacity of water when KCl water was used alone. Based on the results from this study, improvements in fracture treatment design and well spacing should be considered. This paper demonstrates the benefits of an integrated approach to understanding hydraulic fracture growth behavior, which is important for developing a new CBMreservoir.
Influence of In-Situ Stresses on Fracture Stimulations in the Surat Basin, Southeast Queensland
Authors: Flottman Thomas , Brooke-Barnett Sam , Trubshaw Rod , Naidu Sai-Krishna , Kirk-Burnnand Elliot , Paul Pijush , Busetti Seth , Hennings Peter 
Published: November 2013

Abstract
The contribution investigates the relationship between in situ stress regimes, natural fracture systems and the propagation of induced hydraulic fractures in APLNG's (Australia Pacific Liquid Natural Gas) acreage within the Jurassic to Cretaceous Surat Basin in southeast Queensland. On a regional scale the data suggest that large basement fault systems have significant influence on the lateral and vertical interplay between geomechanical components which ultimately control permeability distribution in the area. At a local scale we show several case studies of significant in-situ stress variations (changes in tectonic regime from reverse to strike-slip, changes in horizontal stress orientation as well as changes in differential horizontal stress magnitude) which are identified from wireline image log interpretations and geomechanical models constructed from wireline sonic and density data. These variations are reflected in hydraulic fracture propagation, which is monitored through microseismic monitoring, tiltmeter monitoring. Reverse stress regimes result in the propagation of horizontal fractures; in areas of higher differential stress linear hydraulic fracture orientations are common, whereas in regions of lower differential stress the orientation of hydraulic fractures appears influenced by both stress and pre-existing fractures. The paper is relevant for fracture simulation in areas with complex in-situ stress regimes. The major technical contribution of the study is the use of geomechanical modelling for predicting hydraulic fracture propagation styles.
Knowing Where To Start: Assessment of Methane Resources with Petroleum Systems Modeling
Authors: Neber Alexander , Fuchs Thomas , Hantschel Thomas , Kadir Zailani , Rottke Wolf , Wygrala Björn 
Published: November 2013

AbstractGas hydrates are typically pressure- and temperature-controlled accumulations of mostly methane that occur in sediments at relatively shallow depths. They contain significant amounts of gas, perhaps more than any other conventional or unconventional source, and could ensure energy supplies for many years. Their production has not yet proved to be commercial, but recent progress in developing appropriate production methods is encouraging. There is, therefore, an increasing need to understand and predict gas hydrate distributions and resources; this can be done using a new module developed for industry-recognized petroleum systems modeling software.Petroleum systems modeling software was designed to simulate the generation, expulsion, migration, accumulation, and loss of hydrocarbons in conventional petroleum systems. Recent technological advances in this software have produced a new hydrate module that can be applied to assess unconventional hydrocarbon resources. Pressure and temperature modeling is the core task of petroleum systems models, so they are also obviously suited to gas hydrate modeling.The numerical simulation of accumulations in marine and permafrost environments is done with algorithms describing (1) the physical, thermodynamic, and kinetic properties of gas hydrates; (2) a kinetic model for the microbially mediated, low-temperature degradation of particulate organic carbon in sediments; and (3) the transport of dissolved and free-phase constituents in the pore fluid. In contrast to the resolution of conventional resource assessments, the temporal and spatial resolutions have been increased to enable simulation timesteps of 100 years and a minimum cell thickness of one decimeter.The gas hydrate module was tested on the petroleum systems model of the Alaska North Slope region, where the hydrates have been drilled in fine-grained sand layers in marine and permafrost environments. Hydrate saturations and the methane source rock are well known in the drilled well. Simulations were run to predict the thickness of the Gas Hydrate Stability zone, the generation and migration of biogenic and thermogenic methane gas, the formation and dissociation of gas hydrates under marine and permafrost conditions, and the evolution of these properties over the geological past. The module is now being used by E&P companies and gas hydrate research centers in Japan, Korea, China, Germany, Norway, and the USA.
Characterisation of Fracture Permeability at Cow Lagoon-1, McArthur Basin, Northern Territory, Australia and Recommendations for Development of the Greater Cow Lagoon Structure
Authors: Mildren Scott , Clark Rachael , Holford Simon , Titus Luke 
Published: November 2013

Abstract
Resistivity image log interpretation of Armour Energy's Cow Lagoon-1 well in the Batten Trough of the McArthur Basin identified conductive and resistive fractures and faults throughout the interval. The 423 fracture surfaces and 55 faults interpreted display a dominant strike direction approximately 150°N and secondary fracture populations striking east-west around 060°N. Two borehole breakouts were also determined from image logs and used to constrain the mean maximum horizontal stress direction to 133°N. Contemporary stress distribution in the well is variable and fundamentally linked to the elastic properties of the sampled stratigraphy. Both strike-slip and extensional regimes are represented by the data.
Fracture susceptibility models indicate that the minimum ∆P to initiate a fracture is relatively high in all formations and generally exceeds 25 MPa. This reflects high strength calculated for these units and implies that creation of new fractures under the contemporary stress conditions is unlikely. Reactivation of existing fracture planes is more likely, with minimum ∆P exceeding 7 MPa in each model generated. Observations imply that many of the fractures are optimally oriented to be open or hydraulically conductive in the far field stress field.
Fracture density was shown to vary across the interpreted interval and also strongly correlates with stratigraphy. Steeper bedding dips consistently correlate with an increase in fracture density. Fault count was attributed to the stress conditions and modes of failure. Low fault count correlates with tensile failure, whilst high fault count implies shear failure.
Systematic analysis of the Cow Lagoon-1 data concludes that NNW striking fractures are critically oriented for shear reactivation in the far field stress environment. Such fractures correspond with high fault density and preferentially occur within low strength, low Young's Modulus, low differential stress units.
Integrating Reservoir and Geomechanical Models to Compare the Productivity of Shale Reservoirs Using Different Fracture Techniques
Authors: Lakshminarayanan S.. , Jayakumar R.. , Safari M. R. , Huang Jian , Rai R.. , Christian S.. , Mutlu U.. 
Published: November 2013

AbstractThe ultra-tight nature of shale gas reservoirs has made hydraulic fracturing inevitable. Whilst most of the gas industry is driven by the success of hydraulic fracturing, alternate fracturing techniques have repeatedly been overlooked. In hydraulic fracturing, only 20–30% of the injected water is recovered during clean-up, and this causes a concern over the fracture efficiency. Additionally, the overbalanced pressure during fracturing poses a threat towards damaging the fracture sand face. A potential alternative to eliminate these drawbacks is a forgotten technology-pulsed gas fracturing. The pulsed fracturing (through high pressure gas) also makes the clean-up much faster/simpler. Although the stimulated reservoir volume (SRV) resulting from pulsed fracturing might not be comparable to the one resulting from hydraulic fracturing, it is suspected that the former technique would be more efficient especially in ductile shale where the industry lacks efficient stimulation technique as hydraulic fracturing fails to be successful.Hydraulic fracturing involves a relatively slow loading rate and this usually results in bi-wing fracture geometries. On the other hand, explosive fracturing involves very rapid loading of formation that can trigger multiple fractures. However, due to extreme stress/heat that is generated during the explosion, near wellbore region may reach the plastic limit which inhibits fracture growth away from the wellbore. The pulsed fracturing loading rate and peak load (via high energy gas or propellants) lies in between hydraulic and explosive fracturing processes. This technique has the potential to shatter ductile shale(s): in particular by triggering a ductile to brittle transition: at an optimized pulse rate at a certain depth.Through coupling of geomechanical and reservoir models, a workflow to predict the generated fracture networks and to quantify the productivity/efficiency of the same has been established. Additionally, in order to account for the various phenomena that are expected to occur during transient production, parameters such as desorption and stress dependent permeability have been considered and are presented in this paper.This paper serves as a platform to compare the models depicting the established process of hydraulic fracturing versus an alternate fracturing technique like pulsed gas fracturing.
Does SFAS No. 151 Trigger More Overproduction?
Authors: Young Chaur-Shiuh , Peng Chih-Wei , Chien Chin-Chen , Tsai Liu-Ching 
Published: November 2013

ABSTRACT
This study explores whether SFAS No. 151 affects firms' production-level decisions. Although the change from ARB No. 43 (FASB 1953) to SFAS No. 151 (FASB 2004) seems trivial at first glance, using a sample of U.S. manufacturing firms from the Compustat database (SIC 2, 3) for the period 2003–2008, we document that abnormal production costs significantly increased after SFAS No. 151 became effective in 2005. The empirical evidence substantiates our hypothesis that the explicit expensing and reporting of idle facilities, as stipulated in SFAS No. 151, inadvertently further induces opportunism for excess production. Moreover, we find that firms that have limited options to indulge in accruals management, and those that have pressures to boost income, will have higher excess production after the adoption of SFAS No. 151. Supplementary analyses indicate that our results are robust with regard to controlling for sales manipulation, and to alternative explanations for excess production as well as alternative overproduction measures.
Sickle Cell Disease: Management options and challenges in developing countries
Authors: Ansong Daniel , Osei-Akoto Alex , Ocloo Delaena , Ohene-Frempong Kwaku Ohene-Frempong 
Published: November 2013

Sickle Cell Disease (SCD) is the most common genetic disorder of haemoglobin in sub-Saharan Africa. This commentary focuses on the management options available and the challenges that health care professionals in developing countries face in caring for patients with SCD. In developing countries like Ghana, newborn screening is now being implemented on a national scale. Common and important morbidities associated with SCD are vaso-occlusive episodes, infections, Acute Chest Syndrome (ACS), Stroke and hip necrosis. Approaches to the management of these morbidities are far advanced in the developed countries. The differences in setting and resource limitations in developing countries bring challenges that have a major influence in management options in developing countries. Obviously clinicians in developing countries face challenges in managing SCD patients. However understanding the disease, its progression, and instituting the appropriate preventive methods are paramount in its management. Emphasis should be placed on newborn screening, anti-microbial prophylaxis, vaccination against infections, and training of healthcare workers, patients and caregivers. These interventions are affordable in developing countries.