bluuebunny/crossref_metadata_2025 huggingface dataset:
From the Backyard Dune to Fracturing a Highly Tectonically Complex Formation in Saudi Arabia
Authors: Bartko K. M. , Arnaout I. H , Asiri K. S. , McClelland K. M. , Mulhim N. I. , Tineo R. , Gurmen M. N. , Al-Jalal Z. , Pantsurkin D. , Emelyanov D. Y.
Published: January 2017

Sand in Saudi Arabia is easily accessible through surface mining or excavating large dunes that are API approved, but like many sands around the world, lacks the necessary strength for fracturing high stress formations. To exploit the sand, a novel engineered workflow, enabled by the flow channel fracturing technique was established for qualifying and implementing Saudi Arabian sand to fracture stimulate the tectonically complex ultra-tight "T" carbonate formation.

Channel fracturing does not depend on the proppant pack to provide conductivity, rather on the creation of stable, open flow channels. Therefore, carefully selected sand that can keep the channel structure open under stress can be a viable material to replace up to 80% of the ceramic proppant materials. The local sand used was qualified through unique lab testing procedures to understand the pack behavior under stress, the pillar erosion under stress, and the effects of stress on long-term conductivity. Once qualified, a design methodology was applied to optimize the fracture geometry and pillar placement for the initial field test in Well-A, a horizontal lateral where high strength proppant (HSP) is traditionally used.

A total of six channel fracturing stages with local sand — 40% of the total stages — were placed as per design in two sections of the 15-stage lateral along with four conventional and five channel fracture stages using HSP. A multi-month cleanup and well test period resulted in Well-A being one of the best producing wells in the basin — 26% higher initial production than the next best well. A production log showed sand stages to be producing an average of 15% higher total production than HSP stages. An oil tracer analysis revealed sand stages produced an average of 62% more condensate than HSP stages. This initial production response confirms at least par production with no detrimental effects for channel fracturing with local sand compared to techniques using HSP, with the potential for improved production.

This qualified and field tested completion methodology allows for the potential replacement of a significant portion of imported ceramic proppant with locally sourced sand, an abundant and accessible resource inside the Kingdom of Saudi Arabia and beyond. The benefits of this technology include cost reduction, placement improvement, at least par production and the maximizing of in-country content and value.
Observations and Modeling of the Relation Between Effective Reservoir Stress and Hydraulic Fracture Propagation Pressure
Authors: Pater C. J. , Prabhakaran R. , Shaoul J. R.
Published: January 2017

Accurate prediction of net hydraulic fracture propagation pressure is often impossible. Under some conditions the pressure drop along the fracture dominates while in other cases the pressure at the tip determines the net pressure. Properly scaled lab tests and modeling indicate that effective stress determines the tip propagation pressure, but this is hard to confirm with field data in specific cases.

We therefore gathered a large data base of fracture treatments from many areas to investigate the correlation between net pressure and effective stress. In order to avoid any spurious effect from fluid friction, tortuosity and height containment we limited the data to relatively small injections with water or linear gel in vertical wells. All treatments were in conventional clastic reservoirs, but over a large range of permeability, rock stiffness and geological age.

The data show a remarkably good correlation between net pressure and effective reservoir stress, with a slope of 0.46. Lower net pressure of 200-300 psi was found in over pressured reservoirs and higher net pressure of about 1500 psi was seen in depleted reservoirs. We checked that this is not due to another underlying parameter, such as modulus or depth, which could explain the correlation. It is concluded that the correlation is due to a true relation between net pressure (controlled by fracture propagation) and effective stress. Simulation of representative treatments with a new model that includes a cohesive zone at the fracture tip shows excellent agreement with the observed correlation, supporting a physical relation.

The relation between net pressure and effective stress in the reservoir can contribute to improved treatment design in green fields and also will aid in understanding fracture height growth, since effective stress will differ between formation layers. Calibrated models will still be important in view of lack of detailed formation knowledge, but a correct description of the physics of fracture propagation, based on effective stress at the tip, will facilitate more accurate model predictions.
Reservoir and Completion Considerations for the Refracturing of Horizontal Wells
Authors: Barree R. D. , Miskimins J. L. , Svatek K. J.
Published: January 2017

Horizontal well developments, focused on transverse hydraulic fracture stimulation, have evolved rapidly over the past decade. Many of these completions may have missed or bypassed significant reserves that were intended to be produced from the well. This paper discusses the potential reasons for these inefficient completions, candidate selection for refracturing, and the impacts of offset depletion/infill wells on refracturing.

Rate transient post-treatment stimulation analysis is a powerful tool that can help to determine if and when a horizontal well is receptive to refracturing. Such analysis can help to determine if a well is underperforming, and if that underperformance is due to an inefficient completion or due to reservoir conditions. The paper discusses the importance of appropriate well conditioning/unloading prior to determining if a refracturing may or may not be successful. The impacts of "bashing" into offset depletion during refracturing treatments is also discussed, along with appropriate design considerations to minimize such impacts.

Refracturing can be an important tool to the industry and deserves the attention that it is currently receiving. However, success of such treatments is not guaranteed in every well and the criteria for candidate selection should be a top focus when evaluating such a program.
Comparison of Multi-Stage Fracture Placement Methods for Economic Learning and Unconventional Completion Optimization: A Case History
Authors: Singh Amit , Soriano Lori , Lal Manish K.
Published: January 2017

The two most popular fracture placement methods in unconventional shale with multiple stages fracturing completion are wireline plug-n-perf and pinpoint perforating / fracturing using coiled tubing. The debate regarding which method is better is still unresolved, as each method has its performance and economic advantages, which make the selection decision very challenging for practitioners and decision makers.

In the Antelope Shale reservoir in Monterey Formation, each of these two fracture placement methods were implemented for multi-stage fracturing in 4 vertical offset wells to evaluate the benefits and associated risks, and to identify the preferred method for a full field development plan. The plug-n-perf method had multiple clusters perforated with wireline for each frac stage, whereas the coil tubing method utilized sand-jets to create pinpoint perforation holes with single cluster.

In this paper, we discuss the lessons learned and results from application of both fracture placement methods in Antelope Shale using key performance and economic indicators, including time efficiency, cost, production, fracture geometry and zonal coverage. The multitude of operational events experienced during these completion executions demonstrated both the associated benefits related to improved efficiency (efficient completion execution without trouble, record number of completions in single day, etc.) and disadvantages in terms of delayed operation (perforation guns not firing, CT parting, multiple fishing operations during drill out of plugs, ineffective perforation cutting, depth control of CT, etc). The results from various diagnostics such as microseismic, tiltmeters, Diagnostic Fracture Injection Test (DFIT), tracers, etc. were used to compare the effective pay zone coverage with multiple fracture stages, fracture geometry and well productivity for both fracture placement methods.

For multi-stage fracturing completions in tight rock, an understanding of risks, rewards, and economic impact of both methods is crucial to completion and stimulation strategy.
A Fully-Coupled, Poro-Elasto-Plastic, 3-D Model for Frac-Pack Treatments in Poorly Consolidated Sands
Authors: Lee Dongkeun , Sharma Mukul M.
Published: January 2017

Frac-pack completions have been used as a technique for well stimulation and sand control. Conventional hydraulic fracturing models based on linear elastic fracture mechanics often lead to inaccurate predictions of fracture geometry and fracturing pressure response due to large inelastic deformations and strong fluid-solid coupling. We present a fully-coupled, three-dimensional hydraulic fracture model in poro-elasto-plastic materials using a finite volume cohesive zone model for frac-pack applications.

Our model is capable of capturing the high net fracturing pressure commonly observed during frac-packing operations. The 3-D model simulates both shear and tensile failure around the fracture and computes the stresses and displacements around the fracture. We observe that plasticity causes lower stress concentration around the fracture tip which shields the tip of the propagating fracture from the fracturing pressure. High leak-off can also lead to shear failure around the fracture and ahead of the tip due to pore pressure diffusion. The low cohesion sands tend to fail in shear first then in tension if sufficient pore pressure and poroelastic backstress build up. We use a three-dimensional numerical computation of fluid leak-off using a fracture-reservoir domain coupling in this model to overcome the limitation of linear, one-dimensional leak-off models. Higher pressure gradients due to lower permeability, higher viscosity and injection rate results in a faster fracture propagation rate.

LEFM models inherently predict lower net fracturing pressure, smaller fracture widths and longer lengths in soft formations than observed in the field. In many instances, such models are used to fit the net pressure data by manipulating input parameters beyond physically reasonable values. The model presented here provides a much more physically realistic approach to model fracture growth in unconsolidated reservoirs with lab measured mechanical properties. The model has allowed us to design and analyze hydraulic fracturing stimulations much more accurately than LEFM models used in the past.
Elliptical Flow Regimes in Horizontal Wells with Multiple Hydraulic Fractures
Authors: Apte S. S , Lee W. J
Published: January 2017

The paper demonstrates that the transient flow regime in multi-fractured horizontal wells, often interpreted as linear flow, is more likely elliptical flow. Elliptical flow often cannot be distinguished from linear flow at earliest times, but the apparent transition between transient linear flow and boundary-dominated flow may, in fact, be strongly affected by elliptical flow prior to being influenced by interference between adjacent fractures. Taking the elliptical flow regime into account can often improve our interpretation of production histories and our ability to forecast future production, thus improving economic evaluation and reserves estimation.

We verified elliptical flow regimes by comparing production forecasts from existing semi-analytical and analytical solutions for multi-fractured horizontal wells. We then used asymptotic approximations to elliptical flow solutions to identify important flow regimes and to validate our model.

On the basis of this work, we proposed new methods to determine reservoir properties and explored the parameters influencing the productivity of a multi-fractured horizontal well in a tight shale formation. Finally, we demonstrated, with a field example, the utility and applicability of our elliptical models and work flows for data analysis based on them.

We emphasize our conclusion that transient linear models appear to be mere approximations of the more complete elliptical models during early flow periods in multi-fractured horizontal wells and thus open a question for debate: Is transient linear flow a myth (a mere approximation) or a real flow regime?
Impairment of Fracture Conductivity in the Eagle Ford Shale Formation
Authors: Guerra Jesse , Zhu D. , Hill A. D.
Published: January 2017

Fracture conductivity in shale formations can be greatly reduced due to water-rock interactions. The mechanisms of water damage to fracture conductivity include clay swelling, surface softening, excessive proppant embedment, and fines migration due to fracture surface spalling and failed proppant particles. Fracture conductivity is influenced by closure stress, bulk and surface rock mechanical properties, fracture surface topography, fracture surface elemental composition, rock mineralogy, proppant type and concentration, among other factors. This paper presents a study considering several of the aforementioned factors, centered primarily on saline water induced fracture conductivity impairment of the Eagle Ford shale formation and its five vertical lithostratigraphic units.

Laboratory experiments were conducted to investigate the effect of flowback water on fracture conductivity for Eagle Ford shale samples. The majority of test samples were obtained from an outcrop located in Antonio Creek, Terrell County, Texas; while the remaining samples were obtained from downhole core provided by an industry partner. Saline water with a similar chemical composition to the typical field flowback water was utilized.

Fracture conductivity measurements were conducted in three stages. In the first stage, dry nitrogen was flowed to ascertain the undamaged initial fracture conductivity. In the second stage, the saline solution was injected into the fracture until steady state behavior was observed. In the third and final stage, dry nitrogen was once again flowed to quantify the recovered fracture conductivity. Reported mechanical properties from the same outcrop rock samples, consisting of Poisson's ratio and the Brinell hardness number, were considered in this study. Additionally, reported mineralogy obtained using X-ray powder diffraction (XRD) microscopy was taken into consideration. The elemental composition along the fracture surface was obtained using X-ray fluorescence (XRF) microscopy, and fracture surface topography was obtained using a laser surface scanner and profilometer.

Results support findings that bulk and surface mechanical properties influence fracture conductivity, as well as surface topography and related attributes such as fracture surface area. Furthermore, the bulk mineralogical composition of the rock and the elemental composition of the rock fracture surface have a significant impact on fracture conductivity when flowing saline water in order to simulate flowback. Clay content was observed to directly influence fracture conductivity. The results of this study show a loss of fracture conductivity for Eagle Ford formation ranging from approximately 4 to 25 % after flowing saline water, when compared to the initial conductivity measured by flowing dry nitrogen before saline water exposure. This is not a large loss in conductivity due to water damage, and suggests that water damage may not be the major cause of the large early decline rates observed in most Eagle Ford shale producing wells.
Comparison among Fracture Calibration Test Analysis Models
Authors: Ehlig-Economides Christine A. , Liu Guoqing
Published: January 2017

Recent papers show new models for matching the injection falloff response to a fracture calibration test, also known as minifrac or the diagnostic fracture injection test (DFIT), one numerical and one analytical. Both models address variable compliance, but they disagree on the value for minimum stress. The analytical model provides a way to estimate the effective permeability from the after-closure response that can be compared to an existing methodology for permeability estimation from the before closure behavior.

The objective of this work is to assess where the existing interpretation models agree or disagree and the limitations on where the various approaches apply. The McClure numerical model for variable compliance results in exactly one closure instance, after which all observed behavior is matched with after closure variable fracture compliance. The Liu analytical decoupled fracture model identifies and matches multiple closure events, with variable fracture compliance and/or variable fracture surface area. The Craig model couples before and after closure behavior by treating the fracture closure as storage and matching with against a family of type curves.

The original Mayerhofer method for before closure permeability estimation has clear potential advantage over techniques that require the after-closure response. If before and after closure permeability estimates are sufficiently similar, the need for acquiring after closure data is reduced to pore pressure estimation.

Field examples are used to illustrate the application of the four models. The parameter values estimated from these analyses are essential to design of the main fracture treatment(s). Discrepancies in the value estimates may have profound impact on the treatment design and execution.
Accelerating Completions Concept Select in Unconventional Plays Using Diagnostics and Frac Modeling
Authors: Azad Ali , Somanchi Kiran , Brewer Jim R. , Yang Daniel
Published: January 2017

Data pads in unconventional plays have shown significant value when they are carefully designed to tackle specific problems or concerns. This includes the use of diagnostics to cross-validate development concepts such as stimulation design, well architecture, frac and well spacing, and numerous other variables. In this paper, it is demonstrated how various diagnostics technologies together with subsurface data can be used to calibrate a frac model. The model can then be coupled with a reservoir simulator to accelerate completions concept select decisions in unconventional plays. This process (a) eliminates multiple field trial costs, (b) tests different completions and stimulation designs, and (c) assists in de-risking various field development planning scenarios. This paper focuses on a real-life case-study where integrated diagnostics and modeling were applied to de-risk multiple completions scenarios. An intermediate planar frac model was calibrated and used to lower the uncertainty of key frac parameters including frac geometry and conductivity. In addition, subsurface parameters such as in-situ stresses and rock properties were tuned. The results from the integrated modeling effort were used to propose future development options for the play.
A Causation Investigation for Observed Casing Failures Occurring During Fracturing Operations
Authors: Adams N. J. , Mitchell R. F. , Eustes A. W. , Sampaio J. H. , Antonio A. O.
Published: January 2017

The objective of this paper is to present findings from a causation investigation of casing failures occurring during fracturing operations. The study analyzed case histories and examined post-failure laboratory results. Outcomes from casing failures include blowouts, pollution, injuries/fatalities, and loss of the well with associated costs. This work has not been previously published nor is this type of work available in the public domain literature.

This study cataloged pertinent data from fourteen (14) land-based case histories of casing failures while fracturing. The case histories were analyzed with the use of photographic evidence of recovered casing, well reports, fracturing treatment data, drilling records, and laboratory testing of recovered casing when available. Failure causes were identified. Preliminary guidelines are provided to avoid casing failures and mitigate the damages. Recovery guidelines are presented.

A model was developed to evaluate axial loads under several considerations associated with fracturing. The model accounted for the casing's in-air load, buoyancy effects from wellbore fluids, piston effect, bending, erosion, and temperature decreases. The combined loads were compared to the casing's yield strength.

The failures were not systemic but included cracking related to fatigue, hydrogen and sulfide stress embrittlement, and erosion at ERW weld lines. The failures were observed at various well depths, both in the cemented and uncemented hole sections. Results address common casing sizes and couplings involved with each failure, weight and grade, failure location and causation identification of other factors contributing to the failure. A goal of this investigation and on-going work is to develop a thorough understanding of casing failures and the myriad of contributing factors in order to develop a comprehensive predictive model for land and offshore fracturing operations.
Effect of Geological Layer Properties on Hydraulic Fracture Initiation and Propagation: An Experimental Study
Authors: AlTammar Murtadha J. , Sharma Mukul M.
Published: January 2017

Hydraulic fracture initiation and propagation in the presence of multiple layers with different mechanical and flow properties are investigated experimentally utilizing a novel fracturing cell. Mixtures of plaster, clay and other materials are used to cast sheet-like test specimens in layers with different mechanical properties. The specimen is placed between two transparent plates that allow us to take videos of the speckled rock sample surfaces to facilitate digital image processing of rock displacement. In order to control fracture orientation, a far-field differential stress is applied to the specimen via pneumatic jacks. Hydraulic fracture growth during the experiment is recorded using a high resolution digital camera. Key frames are subsequently analyzed using Digital Image Correlation (DIC) to reveal micro-cracks, strains and other features that are difficult to detect with the naked eye. Experiments are conducted for fracture propagation across layered porous media in different stress states.

It is clearly shown that a fracture initiating in the vicinity of a layer interface may exhibit a range of behaviors including propagation straight through the layer interface, forming secondary fractures, fracture kinking, and fracture propagation along or parallel to the interface. Straight/plane fracture propagation is observed across an interface when going from a hard to a soft layer. Conversely, crossing from a soft to a hard layer, a fracture tends to kink at a slight angle as it approaches the interface. The angle at which the fracture turns increases as the contrast in Young's modulus and fracture toughness between the layers increases and/or the differential stress decreases. Tensile stresses on the intact (hard) side of the interface can also develop a secondary fracture at an offset to the parent fracture with localized interface opening resulting in a fracture step-over. Given a choice of multiple layers, fracture propagation into a harder layer is favored over a softer layer. The effect of hard inclusions that can act as fracture barriers is also investigated. Fractures tend to initiate and propagate parallel to the bounding interfaces when the fracture initiation layer is relatively thin or in the case of an isotropic stress state and propagate along the interfaces when the bonding between the layers is weak. A fracture approaching a dipping, harder layer tends to kink towards the low side of the interface. The experiments, for the first time, clearly demonstrate and quantify experimentally the factors that control fracture propagation across geological layers. The observed turning and branching of the fractures can have a profound effect on fluid leakoff and proppant transport.
Stacked Height Model to Improve Fracture Height Growth Prediction, and Simulate Interactions With Multi-Layer DFNs and Ledges at Weak Zone Interfaces
Authors: Cohen Charles-Edouard , Kresse Olga , Weng Xiaowei
Published: January 2017

Commercial hydraulic fracture software are generally based on the planar 3D model (PL3D) or the Pseudo 3D model (P3D). The PL3D model is more accurate but very CPU intensive, which makes it unsuitable to simulate complex hydraulic fracture networks due to the interaction with natural fractures. The pseudo-3D model is faster but considers separately the vertical and horizontal propagation of the fractures. In recent years, a sophisticated P3D-based complex hydraulic fracture network model, the Unconventional Fracture model (UFM) was developed that can simulate complex physical mechanisms such as interaction with natural fractures, stress shadow and the proppant placement in the complex fracture network. However, one of the main challenges still faced by such simulators is to accurately predict the height growth in formations with heterogeneous mechanical and stress properties.

One assumption of the P3D model is the fracture is being initiated and extended in a lower stress layer than the adjacent layers. In practice, the assumption is not always satisfied, leading to inaccurate or unstable height growth. A comparison of these two models through examples illustrates the situations where P3D model works well and where it does not, and the difficult compromise between accuracy and computational efficiency.

A better compromise can be achieved through a new Stacked Height Growth model (SHG). This model is an enhancement to the P3D model, consisting of multiple rows of elements vertically stacked, to more precisely account for the effect of vertical stress heterogeneity, and to allow multiple horizontal propagation fronts. The width profile and stress intensity factors at the top and bottom depend on the stress and pressure profiles along the stack of elements. The theoretical background of the model is presented. Comparison shows good agreement with the PL3D model for cases that the P3D model cannot accurately simulate, and at a fraction of the computational cost of PL3D. A particularly interesting feature of the SHG model is its flexibility to transition smoothly from a 1D cell-based model such as the P3D model, to a fine scale 2D gridding in the fracture plane. This feature greatly facilitates the implementation of other modeling features into the fracturing simulator.

For example, the SHG model can be used to simulate interaction of hydraulic fractures with Multi-layer Discrete Fracture Networks (MDFN), to better model naturally fractured reservoirs. The SHG model can also be used to model offsets of hydraulic fractures through weak interfaces called ledges. The model can capture the influence of these discontinuities on the proppant placement. Another example, is how a fine 2D gridding using the SHG model can predict proppant placement as accurately as a PL3D model. These extensions of the SHG model have been implemented into the UFM model and are illustrated in this paper through several examples.
Far-Field Proppant Detection Using Electromagnetic Methods - Latest Field Results
Authors: Palisch T. , Al-Tailji W. , Bartel L. , Cannan C. , Zhang J. , Czapski M. , Lynch K.
Published: January 2017

Over 100 billion lbm of proppant are placed annually in wells across the globe, with the majority in unconventional reservoirs. The location of the proppant in these horizontal wells and formations is critical to understanding reservoir drainage, well spacing and stage spacing. However, for many years proppant detection has primarily been limited to near-wellbore measurements. A novel method to detect proppant in the far-field has been developed and is the subject of this paper.

The method to detect proppant that has been developed utilizes electro-magnetic methods. This technology entails using a transmitter source and an array of electric- and magnetic-field sensors located at the surface. A current signal with a unique wave form and frequency is transmitted to the bottom of the wellbore via a standard electric line unit. In addition, an electrically conductive proppant is pumped into the stage(s) of interest. The electric- and magnetic-fields are measured both before and after the detectable proppant stages, and a novel analysis method is then employed to process and invert this differenced data to create an image of the propped reservoir volume.

This technology is the product of years of development of computer models capable of forward modeling this technique. Once this modeling was completed, an initial field test was performed in west Texas, with a preliminary analysis of this work presented in a previous paper. Since that paper, however, additional processing of the data has yielded a much more detailed image of the proppant location in this Bone Springs well. In addition, a subsequent field application has been performed in a major basin in the Northeast US. Multiple stages received detectable proppant of varying stage volumes and the analysis has shown a detailed image of the proppant location in that wellbore also. In addition, the initial west Texas field test employed only electric-field sensors, while this latest test employed both electric- and magnetic-field receivers. Numerical simulations and field results indicate the percentage difference between pre- and post-frac results are two times higher using magnetic versus electric field sensors.

This paper will review the technology development and methods, it will present the latest imaging from the initial west Texas test, and it will describe the latest learnings from the most recent field test. This paper should be beneficial to all completions and development personnel who are interested in knowing where proppant is located in their fractures. This technology has the potential to assist in understanding well drainage and spacing, stage and perf cluster spacing, vertical fracture coverage as well as the impact of fracture design changes.
Immediate results of aortic arch surgery in patients with mild hypothermic circulatory arrest and different types of cerebral perfusion
Authors: Mikhailov A. , Ziyatdinov D.
Published: January 2017

Aim. Emphasis in the study was placed on the analysis of the immediate results of interventions on the aortic arch in patients operated under antegrade/retrograde cerebral perfusion and mild hypothermic circulatory arrest.Methods. Data on 49 patients who underwent intervention on the aortic arch with antegrade (24 patients – group 1) or retrograde (25 patients – group 2) cerebral perfusion and moderate hypothermic circulatory arrest over a period from 2011 to 2015 was collected and analyzed retrospectively. 26.5 % (13) of patients were treated for acute type I aortic dissection. Bicuspid aortic valve was present in 33 % (16), Marfan syndrome was in 4 % (2), aortic regurgitation grade II and III accounted for 56 % (27).Results. The mean age of patients was 58±11 and 58±12 years (р=0.9), males amounted to 83 % and 76 % (р=0.524), NYHA functional class was 2.9±0.5 and 2.8±0.8 (р=0.689) in group 1 and group 2, respectively. Cardiopulmonary bypass time amounted to 190±44 and 207±50 min (р=0.227), aortic cross-clamp time ran to 119±32 and 113±26 min (р=0.503), circulatory arrest lasted 21±12 and 21±15 min (р=0.968) in group 1 and group 2, respectively. Postoperative mortality, prolonged ICU time, complications, stroke were 0 and 8 % (р=0.157), 71 and 48 % (р=0.182), 67 and 64 % (р=0.831), 12.5 and 12 % (р=0.955) in group 1 and group 2, respectively. Conclusion. Antegrade and retrograde cerebral perfusion under a short mild hypothermic circulatory arrest during aortic arch surgery showed comparable immediate results. Antegrade cerebral perfusion should be used in most cases as more physiological.Received 7 September 2016. Accepted 14 November 2016.Funding: The study had no sponsorship.Conflict of interest: The authors declare no conflict of interest.Author contributionsAll authors meet ICMJE authorship criteria and contributed equally at all stages of the research.
Replacement of ascending aorta and aortic arch combined with implantation of bare stent Djumbodis® Dissection System as a treatment of type I aortic dissection
Authors: Komarov R. , Belov Yu. , Karavaykin P. , Soborov M.
Published: January 2017

Aim. The aim of this study is to show the outcomes of an open intervention on the ascending aorta and arch combined with stenting of aorta in type I aortic dissection.Methods. 6 patients with type I aortic dissection underwent implantation of Djumbodis® Dissection System bare stents at I.M. Sechenov First Moscow Medical University’s Aortic and Cardiovascular Surgery Clinic. In 4 patients, aortic stenting was combined with ascending aorta replacement, in 1 patient, hemiarch ascending aorta and arch replacement was performed and in 1 patient aorta and arch replacement was complemented with a Sun procedure.Results. Total operation time, cardiopulmonary bypass time, cross clamp time and hypothermic circulatory arrest time were just similar to those performed in conventional open surgery. There were no intraoperative deaths in this series. 30-day mortality was 16.7 % (1 patient). The patient died because of progressive respiratory and cardiovascular failure, encephalopathy, and gastrointestinal bleeding. 1 patient had acute renal failure and left leg ischemia because of the false lumen thrombosis, 1 patient suffered from cardiac tamponade and 1 patient underwent prolonged mechanical ventilation. Total false lumen thrombosis developed in 1 patient, 4 patients had partial false lumen thrombosis, and in 1 patient the false lumen remained patent.Conclusion. Stenting of aortic arch and descending aorta is a good alternative to aortic arch replacement in type I aortic dissection. It promotes stabilization of false and true lumen diameters and global aortic diameter.Received 18 October 2016. Accepted 7 November 2016.Funding: The study had no sponsorship.Conflict of interest: The authors declare no conflict of interest.Author contributionsConceptualization and study design: Komarov R.N., Soborov M.A.Material acquisition and analysis: Karavaykin P.A. Project curation: Komarov R.N., Belov Yu.V.Article writing: Karavaykin P.A. Review & editing: Komarov R.N., Belov Yu.V., Soborov M.A.
Una especie nueva de Diospyros (Ebenaceae) del municipio de Morelia, estado de Michoacán (México)
Authors: Madrigal-Sanchez Xavier , Rzedowski J.
Published: January 2017

Se describe Diospyros xolocotzii sp. n., planta arbórea de frutos comestibles, al menos superficialmente similiar a D. palmeri Eastw., del NE de México, y a D. bumelioides Standl., dada a conocer de Belice. Solo pudieron contarse 20 individuos en la localidad tipo, que se encuentra intensamente perturbada, por lo cual parece ser grande su peligro de extinción.
Desarrollo del gametofito de Elaphoglossum petiolatum (Sw.) Urban (Lomariopsidaceae)
Authors: Perez Garcia Blanca , Reyes Jaramillo Irma
Published: January 2017

En este trabajo se describe el desarrollo del gametofito de Elaphoglossum petiolatum (Sw.) Urban y se hace una breve comparación de su morfología, con respecto a las especies estudiadas por Stokey y Atkinson (1957) del mismo género.
El gametofito de E. petiolatum varía de forma acintada a cordiforme y presenta pelos unicelulares tanto superficial como marginalmente; puede ser anteridiado, arquegoniado o formar anteridios con desarrollo ulterior de arquegonios.
Las diferencias básicas encontradas entre esta especie y las estudiadas por los autores antes mencionados radican en la duración del período de germinación y en la forma del protalo.
Nuevas observaciones taxonómicas y etnomicológicas en Psilocybe s.s. (Fungi, Basidiomycota, Agaricomycetidae, Agaricales, Strophariaceae) de México, África y España
Authors: Guzmán Gastón
Published: January 2017

Se presenta una nueva emendación de Psilocybe zapotecorum, basada en un re-estudio del holotipo y en la descripción de los pseudocistidios, pleurocistidios y queilocistidos, antes confusamente descritos. Se discute la numerosa sinonimia de este hongo, con base en el estudio de los holotipos y su amplia distribución en el neotrópico. Se analizan sus usos tradicionales como hongos sagrados y se hace una revisión de códices y piezas antropológicas, en donde se identifica a esta especie o sus afines: P. muliercula y P. moseri. Se establece una relación entre el culto de Quetzalcóatl y el uso de tales hongos. Se analizan las palabras “teonanácatl” de Sahagún y “teotlaquilnanácatl” de Guzmán. Se discuten las relaciones de P. mairei con los murales prehistóricos de Tassili en el Desierto del Sahara. Se presenta el primer estudio de materiales auténticos de P. mairei de Argelia, de donde se designa un neotipo. Finalmente se tratan las relaciones entre un mural prehistórico en España y P. hispanica.
Datos para la apreciación de la flora fanerogámica del bosque tropical caducifolio de México
Authors: Rzedowski Jerzy , Calderón de Rzedowski Graciela
Published: January 2017

Se integra una enumeración de 749 géneros de fanerógamas que contienen al menos una especie que habita exclusiva o preferentemente en el bosque tropical caducifolio (btc) de México. Tal lista indica que la familia Leguminosae es la mejor representada en este tipo de vegetación; le siguen en importancia las Compositae y Gramineae y en seguida Malvaceae, Orchidaceae y Apocynaceae. La composición florística del btc de nuestro país con frecuencia discrepa mucho de una localidad a otra. De acuerdo con lo encontrado en la literatura, al menos 96 géneros de árboles se registran con especies dominantes o cuantitativamente importantes en los censos realizados en diferentes partes del país. Las afinidades geográficas de la flora del btc indican estrechos vínculos con las de Centro y Sudamérica. De acuerdo con este inventario, 7.9% de los géneros son endémicos a los límites políticos de la República y esta cifra sube a 19.2% si se toma como referencia también a Centroamérica. La existencia del btc en México data al menos desde Cenozoico Temprano y su flora actual, sin menoscabo de haberse nutrido mediante intercambios de fuentes diversas, es primordialmente el resultado de largos e intensos procesos evolutivos realizados en su propio seno.
Las plantas vasculares acuáticas estrictas y su conservación en México
Authors: Mora-Olivo Arturo , Villaseñor José Luis , Martínez Mahinda
Published: January 2017

Con base en el análisis de la riqueza y distribución de las hidrófitas vasculares estrictas, se identificaron las entidades federativas más relevantes para la conservación de los humedales de México y su flora asociada. Se registraron 240 especies distribuidas en 106 géneros y 62 familias, incluyendo 227 nativas y 13 introducidas, lo que representa 24% del total de las plantas acuáticas estimadas para México, incluyendo 8.3% de endemismo. Los estados que registran la mayor cantidad de especies son Veracruz (145 especies), Jalisco (123), Michoacán (115) y Tamaulipas (113). Un análisis iterativo indica que es necesario involucrar a 13 estados para la conservación de 100% de la flora acuática nativa.
Afinidades florísticas y fitogeográficas de la vegetación del municipio de San José Iturbide, Guanajuato, México
Authors: Gutiérrez Jorge , Solano Eloy
Published: January 2017

Se realizó un estudio florístico y se establecieron los patrones de distribución geográfica y ecológica de las especies que conforman la flora vascular del municipio de San José Iturbide, Guanajuato. Este municipio se ubica en el Altiplano Mexicano. El área de estudio cubre una superficie de 538 km2. Se censaron 661 especies, incluidas en 361 géneros y 101 familias. Se encontraron dos nuevos registros para el estado de Guanajuato, Osmunda regalis var. spectabilis y Anoda pentaschista. Se estimó que el inventario integra cerca de 70% de los taxa presentes en el área. El 41% de las especies son endémicas de México, 114 de ellas son propias del centro del país, siete de éstas solo se distribuyen en áreas cercanas al municipio y una es endémica del mismo. La flora vascular de la zona tiene afinidad con la de los matorrales xerófilos del centro de México, y comparte un gran número de especies con la vegetación de clima árido del Altiplano Mexicano. San José Iturbide contiene 12% de las 5500 especies estimadas para la región que abarca el proyecto “Flora del Bajío y de Regiones Adyacentes”, y 22% de las calculadas para el estado de Guanajuato, por lo tanto, su riqueza florística es alta si se considera su pequeña superficie.
Inventario micobiótico de la región de Tapalpa, Jalisco, México
Authors: Gándara Etelvina , Guzmán Dávalos Laura , Guzmán Gastón , Rodríguez Olivia
Published: January 2017

Se presentan 233 taxa (especies y variedades) de hongos (229 macromicetes y cuatro micromicetes) de la región de Tapalpa, Jalisco. El material estudiado fue recolectado en los años 2000 al 2003, principalmente en bosques de Pinus y Quercus. Se examinaron además otros ejemplares depositados en el Herbario IBUG provenientes de dicha área. Se registran por primera vez de Jalisco 21 taxa. Doscientos cinco especies (88%) pertenecen a Basidiomycota, 22 (9.5%) a Ascomycota y 6 (2.5%) a Myxomycota. Éste constituye el primer inventario micológico de la zona.
Las plantas vasculares y vegetación de la barranca Tepecapa en el municipio de Tlayacapan, Morelos, México
Authors: Hernández Cárdenas Rodrigo Alejandro , Cerros Tlatilpa Rosa , Flores Morales Alejandro
Published: January 2017

El área de estudio, la Barranca Tepecapa de aproximadamente 3.5 km de longitud, se ubica dentro de la zona núcleo “Las Mariposas” en el Corredor Biológico Chichinautzin del estado de Morelos. Se realizaron colectas periódicas durante un año y medio, de octubre 2009 a abril 2011. Se colectaron 1018 ejemplares de Pteridofitas y afines, Gimnospermas y Angiospermas, pertenecientes a 99 familias, 266 géneros y 434 especies. Las familias mejor representadas son: Asteraceae, Fabaceae, Poaceae, Orchidaceae, Pteridaceae, Solanaceae y Bromeliaceae. Asimismo, se registran y describen tres tipos de vegetación para el área de estudio. Dos géneros (Amyris y Dasylirion) y 16 especies son nuevos registros para el estado de Morelos.
Una nueva especie de Hechtia (Bromeliaceae; Hechtioideae) del estado de Morelos, México
Authors: González-Rocha Edith , López-Ferrari Ana Rosa , Cerros-Tlatilpa Rosa , Espejo-Serna Adolfo
Published: January 2017

Se describe e ilustra Hechtia montis-frigidi, nueva especie de Morelos, México. El nuevo taxon se compara con H. chichinautzensis y H. podantha, especies con características similares.
Sistemática de Lonchocarpus sección Punctati (Fabaceae: Milletiieae), basada en datos morfológicos y moleculares, con la descripción de nueve especies nuevas
Authors: Sousa Mario , Sotuyo Solange , Pedraza-Ortega Euler
Published: January 2017

Se realizó un análisis filogenético de la sección Punctati (27 accesiones) de Lonchocarpus y géneros hermanos empleando caracteres moleculares y morfológicos. La sección Punctati es monofilética y consiste de tres clados correlacionados geográficamente (México, México-Sudamérica y las Antillas), dichos clados están caracterizados por diferentes tipos de plántulas. Se describen e ilustran nueve especies nuevas: Lonchocarpus adamsii, L. antioquiensis, L. brachyanthus, L. crassicalyx, L. grandifoliolatus, L. gyroides, L. major, L. sumiderensis y L. tenorioi, basándose principalmente en caracteres morfológicos incluyendo los de las plántulas.
La familia Juncaceae en México
Authors: Balslev Henrik , Duno de Stefano Rodrigo
Published: January 2017

Se presenta un tratamiento de la familia Juncaceae Juss. para la flora de México. La familia incluye dos géneros en dicho país: Juncus L. yLuzula DC. El primero comprende 31 especies y el segundo cinco. Se proporciona una clave para la identificación de los taxones, descripciones morfológicas, notas taxonómicas e información sobre la distribución geográfica, así como ilustraciones de algunas especies. Una especie es endémica: Juncus chiapasensis Balslev crece exclusivamente en el estado de Chiapas. Otra, J. textilis Buchenau, es un endemismo local que se encuentra en el estado de Baja California y en el estado de California en los Estados Unidos de América.
Cambio climático y sus efectos en la vegetación de Veracruz, México: una aproximación mediante modelado de nicho ecológico
Authors: Estrada-Contreras Israel , Equihua Miguel , Castillo-Campos Gonzalo , Rojas-Soto Octavio
Published: January 2017

De acuerdo con el último informe del Panel Intergubernamental sobre Cambio Climático, las actividades humanas son las principales responsables del calentamiento global observado en las últimas décadas y se debe al incremento en la concentración atmosférica de gases de efecto invernadero. Este proceso ya está causando cambios en la distribución geográfica de las especies, así como alteraciones en la fenología. En tal contexto, es interesante estudiar las posibles tendencias de cambio que podrían presentar la flora y fauna para hacer frente a las nuevas condiciones del medio ambiente. En este trabajo se exploran los posibles cambios en la composición de los principales tipos de vegetación en el estado de Veracruz, México, ante un escenario de cambio climático, mediante el análisis de los patrones de alteración geográfica y ecológica de un grupo de 51 especies comúnmente asociadas al bosque tropical perennifolio, el bosque de coníferas y el bosque mesófilo de montaña, presentes en el estado. El enfoque adoptado se basa en la técnica de modelado de nicho ecológico realizado con el Algoritmo Genético para la Producción de grupos de Reglas (GARP) y variables climatológicas estimadas para un escenario A2 que corresponde a una humanidad que genera emisiones medias-altas y derivan de proyecciones hechas a partir de las condiciones actuales hacia el año 2050. Los resultados obtenidos para la superficie actual de la vegetación del estado de Veracruz sugieren una afectación potencial de 53% del área de distribución para el bosque tropical perennifolio, de 16% para el bosque de coníferas y de 49% para el bosque mesófilo de montaña. Además, apuntan a que algunas especies tienen alta probabilidad de resultar extirpadas de la entidad bajo las condiciones esperadas en el 2050, mientras que otras encontrarán las condiciones adecuadas para incrementar su distribución.
Helechos y licofitos epífitos de Veracruz, México: riqueza y distribución
Authors: Mendoza-Ruiz Aniceto , Ceja-Romero Jacqueline , Pérez-García Blanca
Published: January 2017

Con base en la revisión de material de herbario y literatura especializada, así como en la recolección de ejemplares botánicos, obtuvimos la información correspondiente a la riqueza, distribución por municipio, tipo de vegetación e intervalo altitudinal de los helechos y licofitos epífitos que habitan en el estado de Veracruz. Se registraron para el área de estudio 11 familias, 33 géneros, 173 especies con al menos un ejemplar de respaldo y 23 citadas en la literatura. Las familias mejor representadas a nivel específico fueron Polypodiaceae, Hymenophyllaceae y Dryopteridaceae, mientras que los géneros con mayor número de taxa fueron Polypodium, Asplenium, Elaphoglossum y Trichomanes. La mayoría de las plantas se distribuyen en los bosques mesófilo de montaña, tropical perennifolio y de Quercus, en un intervalo altitudinal que va de los 751 a los 1750 m.