bluuebunny/crossref_metadata_2025 huggingface dataset:
Refining Discrete Fracture Networks With Surface Microseismic Mechanism Inversion and Mechanism-Driven Event Location
Authors: Cornette Brian M. , Telker Cherie , De La Pena Alejandro
Published: December 2012

Microseismic event analysis is a valuable source of information that can play a pivotal role in optimizing well completion and spacing. This analysis can be taken a step further with the generation of discrete fracture networks (DFNs) from microseismic events. While DFNs can be modeled with microseismic event locations only, source mechanisms inverted from near surface-acquired microseismic data provide greater constraints for the DFN model so that the orientation of failure planes responsible for events can be explicitly assigned. The differences between such DFN realizations based on event locations only and source-mechanism constrained DFN realizations are evident in areas with significant geological complexity.

Three iterations of a DFN model were produced from a microsesimic monitoring project in the Barnett shale. The fracture network of the first iteration is modeled stochastically using only basic geologic assumptions for the area and microseismic event locations and the orientations of trends formed by the events. The second iteration is refined by deterministically locating fractures in the model and defining the fracture orientations using a source mechanism determined from the microseismic point set. The third iteration uses the results from a mechanism scan on an event per event basis to determine the best source mechanism that fits the polarity reversal signature observed on the surface array.

Refining the model by determining the mechanism of individual events can identify multiple fracture orientations within the point set. In this data set two distinct mechanisms were identified, further analysis of which identified separate event energy distributions for the two mechanisms.

The changes in the model can be quantitatively evaluated with analysis of flow properties generated from the DFN and output to the stimulated reservoir volume (SRV). While changes in the SRV and total fracture volume for models presented in this study are most significant between the first two iterations, the total permeability change across the geocellular volume is significant between all three iterations.
Fracture Shadowing: A Direct Method for Determination of the Reach and Propagation Pattern of Hydraulic Fractures in Horizontal Wells
Authors: Daneshy Ali , Au-yeung Jessica , Thompson Trevor , Tymko Dean
Published: December 2012

This paper reports the results of field measurements carried out in four horizontal wells all of which were fractured in the course of this investigation, with a total of 68 fractures. The engineering basis for these measurements was detection of fracture shadowing (created by a combination of stress and pressure shadowing) created by the extending fractures. The results are used to develop a field-based engineering foundation for determination of fracture orientation and extent, spacing between wells, and the optimum number and spacing between fracture stages. Two of the four wells served as observation wells throughout the project while the other two were actively being fractured. Pressure gages were installed in each of the two observation wells.

Our findings show that we were able to detect fracture shadows generated by every stage of active fracturing. All the created fractures had a consistent northeast-southwest orientation, many were asymmetrical with respect to the wellbore, their propagation pattern was off-balance, and none of them intersected any of the many other existing fractures within the experiment domain. Some of the fractures had intersected and extended beyond the adjacent cased horizontal holes. The results also provided working approximations of the created fracture lengths.

A fortuitous coincidence of events allowed us to detect fractures created during the measurement period from another nearby well more than 1000 ft away. The fact that through fracture shadowing we were able to detect fractures so far away is quite remarkable. Furthermore, the general fracture growth pattern was consistent with the findings from the other four wells. The major advantage of the proposed approach is simplicity of operations, ease of analysis, and the high quality of results.
Modeling of Interaction of Hydraulic Fractures in Complex Fracture Networks
Authors: Wu R. , Kresse O. , Weng X. , Cohen C. , Gu H.
Published: December 2012

A recently developed unconventional fracture model (UFM) is able to simulate complex fracture network propagation in a formation with pre-existing natural fractures. Multiple fracture branches can propagate simultaneously and intersect/cross each other. Each open fracture exerts additional stresses on the surrounding rock and adjacent fractures, which is often referred to as "stress shadow" effect. The stress shadow can cause significant restriction of fracture width, leading to greater risk of proppant screenout. It can also alter the fracture propagation path and drastically affect fracture network patterns. It is hence critical to properly model the fracture interaction in a complex fracture model.

A method for computing the stress shadow in a complex hydraulic fracture network is presented. The method is based on an enhanced 2D Displacement Discontinuity Method with correction for finite fracture height. The computed stress field is compared to 3D numerical simulation in a few simple examples and shows the method provides a good approximation for the 3D fracture problem. This stress shadow calculation is incorporated in the UFM. The results for simple cases of two fractures shows the fractures can either attract or repel each other depending on their initial relative positions and compares favorably with an independent 2D non-planar hydraulic fracture model.

Additional examples of both planar and complex fractures propagating from multiple perforation clusters are presented, showing that fracture interaction controls the fracture dimension and propagation pattern. In a formation with small stress anisotropy, fracture interaction can lead to dramatic divergence of the fractures as they tend to repel each other. However, even when stress anisotropy is large and fracture turning due to fracture interaction is limited, stress shadowing still has a strong effect on fracture width, which affects the injection rate distribution into multiple perforation clusters, and hence overall fracture network geometry and proppant placement.
The Quest to Exclusive Use of Environmentally Responsible Fracturing Products and Systems
Authors: Brannon Harold D. , Daulton Daniel J. , Post Matthew A. , Hudson Harold G. , Jordan Andrew K.
Published: December 2012

Hydraulic fracturing processes have recently been the subject of increasing scrutiny with particular concern directed towards protection of water resources. Operators and fracturing services companies in the United States have been targeted by both federal and state legislators and the EPA with audits, inquiries, and regulations requiring disclosure of the chemicals pumped in fracturing treatments and banning the use of certain chemistries, such as diesel oil. Much effort has been expended to identify alternative, more environmentally acceptable products which maintain the needed material performance characteristics and cost basis.

A new quantitative process based upon the Globally Harmonized System for Classification and Labeling of Chemicals (GHS) has been employed to evaluate and rank the hazards posed by various treating fluid additives and potential alternatives. The GHS is a process is which has been adopted by the United Nations to standardize information regarding the hazards and toxicities of chemicals. Once the respective material hazards have been quantified, they may be ranked for comparison with like-purposed additives for their anticipated safety, health, and environmental impact. The best candidates by that measure may then be assessed for performance and cost. The process has become a valuable tool to guide fracturing R&D and oilfield chemical suppliers toward development of more environmentally acceptable products and systems.

The progress towards the objective of full implementation of environmentally acceptable chemistries in fracturing applications is documented. Working examples of the more acceptable chemical additive selections resulting from the applications of the hazard assessment process are provided. Furthermore, the migration to more environmentally responsible fracturing processes through quantification of hazardous risk "removed" from applications by replacement with more favorable alternatives is discussed.

The fruits of the process will be discussed in this endeavor, providing working examples of the chemical additive selection. Furthermore, the progress to more environmentally responsible fracturing processes through quantification of hazardous risk ‘removed’ from applications, i.e. amount of hazardous material removed by replacement with more favorable alternatives.
Proppant and Fluid Selection To Optimize Performance of Horizontal Shale Fracs
Authors: Penny Glenn , Zelenev Andrei , Champagne Lakia , Crafton James
Published: December 2012

The productivity and economics of horizontal wells are governed by the ability of the transverse fractures to communicate efficiently with the wellbore, which is strongly controlled by the conductivity of the proppant bed and the effectiveness of the fluid additives. These impact the relative permeability, the capillary pressure and the effective conductivity in the proppant bed. When time at temperature, stress cycling, embedment, multi-phase flow and non-Darcy effects are considered, the effective conductivity can be reduced 100-fold. Another investigated parameter is the impact of the wellbore location relative to the propagated fracture. If the wellbore is high in the fracture, gravity segregation will cause liquid removal from the lower portion of the fracture to be very difficult. In low conductivity proppant beds, capillary pressure will tend to retain high water saturations, thus lower conductivity even for the portions of the fracture above the wellbore.

Laboratory experiments have addressed these issues for proppants with a range of permeabilities from 10 to 100 Darcies; 100 mesh to 20/40 mesh and ceramics. The relative permeability to gas can be as low as 0.01, with as much as a 70-fold improvement when suitable proppants and additives are employed. Evaluation of the production performance of 240 wells, 98 with effective additives and 142 without, and covering a similar range of proppant types and sizes, shows a similar benefit to the wells’ normalized 30 day recovery and gross value. These results clearly demonstrate that economic expediency can be detrimental to a well’s ultimate value and hydrocarbon recovery.
Data Driven Modeling Improves the Understanding of Hydraulic Fracture Stimulated Horizontal Eagle Ford Completions
Authors: Shelley Robert , Saugier Luke , Al-Tailji Wadhah , Guliyev Nijat , Shah Koras , Godwin Jonathan
Published: December 2012

The subject of this paper is the results from a data driven modeling effort to derive best practices for the completion of hydraulically fractured horizontal Eagle Ford wells. The well, reservoir and production information used in this evaluation were provided by an operator, and are from a five county area in Texas consisting of Karnes, Gonzales, Atascosa, Dewitt and Live Oak.

Hydraulically fractured horizontal completions pose significant modeling and evaluation challenges. This is primarily due to two issues; 1) lack of well specific data about the reservoir/rock properties and 2) unrealistic assumptions used in the modeling process. As shown in this paper, a data driven approach to modeling these completions provides a much needed pragmatic perspective, identifies high impact parameters and provides direction about how to improve the effectiveness of these complex completions.

Sensitivities performed on the predictive model developed from Eagle Ford data indicate that well to well variation in reservoir quality and geology has a dominant effect on Eagle Ford production. In addition, issues such as fracture spacing, frac volume, perforation distribution, proppant selection and wellbore length also effect well production and economics. A ranking of controllable (Completion and Frac) and non-controllable (Reservoir and Geology) parameters that affect Eagle Ford production is included in this paper. This information can be used to derive best practices and is useful in explaining well to well variation in Eagle Ford production by quantifying the effect of reservoir quality, completion and frac methodology on results.
Engineering Guide to the Application of Microseismic Interpretations
Authors: Cipolla C. , Maxwell S. , Mack M.
Published: December 2012

abstract

Microseismic monitoring (MSM) of hydraulic fracture treatments is routine in North America and has added significantly to our understanding of fracture growth. The interpretation of microseismic images is advancing steadily, extracting more information from event patterns, temporal evolution, and acoustic waveforms. The increasing amount of information from MSM provides significant opportunities to improve stimulation designs, completion strategies, and field development. However, the applications of microseismic interpretations are many times ill-defined, overlooked, or not applied properly. Numerous applications of microseismic measurements have been documented in technical publications, typically in the form of case histories focused on specific applications. The industry has lacked a compilation and comprehensive discussion of microseismic applications. This paper presents a practical guide for the engineering application of microseismic interpretations, documenting reliable application workflows while highlighting the consequences of misapplication of microseismic interpretations.

The application of MSM starts with a reliable interpretation of fracture geometry and complexity, but the real value is in the application of the interpretation. This paper divides microseismic applications into three categories, real-time, completion strategies & stimulation design, and field development. The MSM interpretation requirements for each category are documented and a comprehensive guide to properly applying these interpretations is presented. Applications issues such as determining the "effective" fracture surface area, the relationship between microseismic behavior and well performance, and fracture model calibration are addressed.

There is a growing interest in advanced processing such as moment tensor inversion (MTI) and b-values to determine focal mechanisms, source parameters, and failure mechanisms associated with the microseismic events. However, the engineering application of these interpretations is not well understood. This paper includes a discussion of the applications of advanced processing results, emphasizing how the limitations and uncertainties of the processing affect the subsequent applications.
Field Study Compares Fracture Diagnostic Technologies
Authors: Grae Abram D. , Duenckel Robert J. , Nelson Jordan R. , Smith Harry D. , Han Xiaogaag , Palisch Terry T.
Published: December 2012

Traditional proppant placement evaluation in hydraulically induced fractures utilize detection of radioactive (R/A) tracers such as iridium 192, scandium 46 and antimony 124, which are manufactured in nuclear reactors, and then shipped to the wellsite and pumped downhole with the frac slurry. Although this technique has proven useful, it involves environmental, safety, and regulatory concerns/issues. Recently a new technology has become available that offers a viable alternative to radioactive tracers. Field examples of the application of this technology and its usefulness to the operator are presented in this paper, along with a field comparison to the results from R/A tracers.

The new technology utilizes a non-radioactive ceramic proppant (CEP) that contains a high thermal neutron capture compound (HTNCC). This high thermal neutron capture compound is inseparably incorporated into each ceramic proppant grain during manufacturing in sufficiently low concentration so as not to affect proppant properties. The non-radioactive proppant is detected using standard compensated neutron and/or pulsed neutron tools, with detection based on the high thermal neutron absorptive properties of the proppant relative to downhole constituents.

Multiple zones in two wells in Wyoming were hydraulically fractured utilizing the non-radioactive detectable ceramic proppant. In addition, multiple zones in a well in Utah were fractured utilizing the non-radioactive detectable proppant and the results are compared to results from an R/A tracer utilized in another well in the same field. These field results and comparisons will aid the frac engineer in choosing appropriate proppant detection techniques.
Evaluating Horizontal Well Completion Effectiveness in a Field Development Program
Authors: Cherian Bilu V. , Stacey Edwin S. , Bressler Stephen , Iwere Fabian O. , Heim Robin Noel , Higgins-Borchardt Shannon
Published: December 2012

In field development programs where large variations in reservoir and completion parameters exist, the evaluation of reservoir performance to determine the optimal completion strategy can be a challenging task. This paper presents findings from a recent integrated cross-discipline analysis of a pilot program performed in the Bakken and Three Forks Formations (Williston Basin, North Dakota) to evaluate the impact of petrophysical and geomechanical properties on hydraulic fracture lengths, reservoir connectivity, well performance and well spacing.

Microseismic, geological, geomechanical, completions, engineering and production data were integrated in single and multi-well modeling approaches to provide an objective method to evaluate and compare well performance. Results and conclusions from various disciplines were validated by integrating operational observations with the modeling. The application of the proposed workflow allows one to (1) understand and evaluate the effect of fracturing parameters (length/conductivity) on well performance, (2) characterize reservoir and fracture properties using hydraulic fracture pressure and production history matching techniques (3) relate fracture parameters to reservoir, geology and mechanical properties and, (4) provide a methodology to understand key drivers controlling the development strategy of an asset.
Discrete Fracturing of a Deep, Unconventional Shale Play Using Multilateral Technology
Authors: Durst Doug G. , Vento Mario , Tucker Gary , MacDonald Mike
Published: December 2012

Drilling, completing, and fracturing unconventional formation wells in North America are now commonplace and will play a major role in the future of natural-gas production on which the nation will depend. What is not as common, however, is to drill, complete, and fracture multiple lateral branches from a single main wellbore. Multilateral wells have been routinely drilled for a number of applications, and shale plays are a natural progression for its use. Augmenting a multilateral well with selective fracturing of each leg is as straightforward as fracturing a single horizontal well.

Using conventional equipment and techniques, a multilateral well (with any number of laterals) can accommodate any type of fracturing system and program with pressures up to 12,500 psi and complete isolation of the lateral junction(s). In this project, a plug-and-perf system was used to address 10+ intervals in each leg, with average stimulation pressures up to 9,000 psi. By employing multilateral completion systems in unconventional wells, operators can lower drilling and completion costs, lower risk, help avoid non-productive time, reduce well count and surface footprint by combining two or more targets into one well, and maximize the net-pay-per-foot drilled ratio.

This paper will discuss the implementation and execution of this project as the first dual lateral well by any operator in the Granite Wash at vertical depths over 12,000 ft and measured depths reaching beyond 17,000 ft. This well targeted two different sections of the Granite Wash (a complex series of sands, shales, and siltstones that run from the Northern Texas Panhandle into Oklahoma) from a single main wellbore with commingled production rates doubling typical single horizontal well performance. Additionally, significant cost savings were achieved in contrast to drilling two separate single horizontal wells.
Openhole Multistage Hydraulic Fracturing Systems Expand the Potential of the Giddings Austin Chalk Field
Authors: Callarotti Gian F. , Millican Steven F.
Published: December 2012

The Austin Chalk formation has seen several active development booms over the past 35 years due to new technologies. Recently, a program was undertaken to test multistage fracturing technology in the Giddings Austin Chalk field to determine if sufficient additional reserves could be unlocked to spark another development boom. This paper highlights the challenges encountered during the project from the initial reservoir simulation and well candidate selection through system design and installation and treatment design.

The Austin Chalk formation has seen considerable horizontal development across Texas as operators chased areas of concentrated natural fractures. Significant quantities of hydrocarbons are apparently trapped in the tight carbonate matrix between the widely spaced fractures along the proven productive edge of the field. Many of the wells in these areas have poorly drained the Austin Chalk due to limited natural fracturing. Multistage fracturing has the potential to reach the insufficiently drained matrix blocks by isolating portions of formation between the natural fractures.

A total of 16 openhole multistage hydraulic fracturing completion systems have been run in the Giddings Austin Chalk field across four different counties in an effort to increase EUR’s from existing wells and to extend the economic boundaries of the formation.

Simulation work done at the outset of the project pointed towards economic incremental recoveries from multistage hydraulic fracturing. This work also helped validate initial candidate selection. It was found that openhole multistage systems can be run into the Austin Chalk, but it was learned that due to high formation friction factors, careful design work was necessary to ensure that the completion equipment could be run to the desired depth. Results to date have shown that multistage fracturing can increase recovery from existing wells in poorly fractured areas as well as allow for economic development of previously uneconomic fringe areas.
Permeability Anisotropy and Dilation Due to Shear Failure in Poorly Consolidated Sands
Authors: Manchanda Ripudaman , Olson Jon E. , Sharma Mukul M.
Published: December 2012

Shear failure plays an important role in fracture propagation in poorly consolidated formations. In past work, the effect of shear failure on the permeability and porosity of sands has been inconclusive. In this paper, a three-dimensional discrete element model is used to estimate changes in porosity and permeability due to mechanical deformation of sand-packs. Using pore network fluid flow simulations, the effect of shear failure and stress anisotropy on the permeability anisotropy and dilation of the granular specimens is analyzed.

Mechanical deformation data from experiments conducted on cylindrical sand packs is used to calibrate the simulations. Using these calibrated models, anisotropic stress regimes are modeled to mechanically deform the simulated samples. Post-processing tools have been developed to observe the preferential orientation of failure planes. Pore network fluid simulations describe the orientation of the permeability tensor. The principal permeability values of an anisotropically stressed sample are described in 3-D.

Deformation of the samples induces shear failure planes, which are preferentially oriented along the maximum horizontal stress direction. Deformed samples with the same minimum horizontal stress (50 psi) but increasing maximum horizontal stresses (50 psi to 300 psi) show an increase in the permeability in the maximum horizontal stress direction by 28-38%. An increase in horizontal stress anisotropy is shown to result in an increase in permeability in all directions due to dilation and failure. The effect of confining pressure, grain size distribution and sorting on failure, permeability anisotropy and dilation is also studied.

The resultant permeability anisotropy induced by shear failure and dilation is of vital significance for simulating fracturing and flow processes in soft rock formations.
New Physics-Based 3D Hydraulic Fracture Model
Authors: Hsu Yun , Dang Xinglai , Chilton Warren , Chang Philemon , Stelin Igor , Gusain Deepak , Northington Neill , De Pater Hans
Published: December 2012

We present a fully 3D planar fracture model based on a finite element solution for fracture opening and a finite difference solution for slurry transport in the fracture. The new model can be used in cases with sufficient data gathered from logs, cores and micro-fracs. It can also be used in conjunction with fracture mapping to develop calibrated models that are based on the fundamental physics of fracturing.

Using novel numerical methods for the elasticity solution, we obtain an accurate description of the stress near the fracture tip. Combined with the physics of the cohesive zone model, this provides an appropriate description of fracture propagation. Benchmarking the model against laboratory tests shows a favorable comparison between modeling and observations.
Impact of Completion System, Staging, and Hydraulic Fracturing Trends in the Bakken Formation of the Eastern Williston Basin
Authors: Lafollette Randy F. , Holcomb William D. , Aragon Jorge
Published: December 2012

In this study, the authors have analyzed well and production data beginning with more than 400 wells in the greater Sanish-Parshall area of the Bakken. The study used Geographical Information System pattern-recognition techniques along with other data-mining techniques to interpret trends in the data sets. The study was made possible by combining data sets from the North Dakota Industrial Commission Oil and Gas Division, public data, and in-house proprietary data.

The study was designed to search for relevant trends in the distribution of production results for wells completed with fracturing sleeves and packers, plug and perforated, or complex completions to determine whether differences in productivity existed and needed to be factored into completion recommendations.

Trends examined in the project in addition to completion type included treatment parameters such as fracturing fluid types and quantities, proppant types and quantities, number of completion stages and stage lengths, perforation cluster spacing and length, and calculated perforation friction drop. All parameters analyzed were examined for statistical importance.

This work is significant in that it shows that the application of practical data-mining methods to an intermediate-size Shale Oil (light, tight oil) well data set can result in learning key lessons that may not be apparent when working with small data sets. This work is 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 of the Bakken Formation for improved interpretation. The work is also significant in that it may be used to allow selection of completion systems on the basis of completion time and cost balanced against concerns over differences in well production impact of one system over another, e.g., frac sleeves versus plug and perf type and complex completion systems.
High Pressure Testing of Borate Crosslinked Fracturing Fluids
Authors: Marquez M. , Tonmukayakul N. , Schafer L. , Zielinski M. , Lord P. , Goosen T.
Published: December 2012

Successful hydraulic fracturing requires proper proppant placement within an adequate fracture length. To accomplish this, one must design a fracturing fluid that can achieve effective proppant placement and retain desirable fluid properties under hydraulic fracturing conditions within the reservoir. Recently, there have been reports that increased pressure on the fluid may reduce the viscosity of borate-crosslinked fracturing fluids. Depending on fluid composition and operating temperature, the effects of applied pressure vary from slightly influencing to completely reducing the viscosity of the crosslinked sample to its un-crosslinked state (linear gel). Thus, a good understanding of the impact of applied pressure on viscosity of fracturing fluids in the laboratory is critical to designing and tailoring fluid formulations. This work describes the equipment and experimental procedures for high pressure rheology testing of selected seawater and higher density brine-based borate crosslinked fracturing fluids in the shear rate range of 20 to 80 s-1, up to 20,000 psi and 180°F.
Optimizing Hydraulic Fracture Spacing in Unconventional Shales
Authors: Morrill Jonathan C. , Miskimins Jennifer L.
Published: December 2012

"Stress shadowing," where the stress field around an induced hydraulic fracture reorients from its far field directions by up to 90 degrees, is a major factor in designing and executing multiple hydraulically fractured, horizontal well completions. This is especially true as the number of hydraulic fractures increase for a given lateral length. Often the number of fracture stages is determined by well analogues without considering how stress shadows alter fracture properties. In this paper, the main objective is to determine what properties are most important in determining the minimum distance needed between hydraulic fractures to avoid stress interference. A finite element model of a horizontal wellbore with a transverse hydraulic fracture is constructed in order to perform numerical simulations of the stress around the fracture. The model is used to perform sensitivities on various mechanical and reservoir properties to investigate how and why the stress field changed.

The simulation results show that the ratio of minimum to maximum horizontal stress is the most important parameter to know in order to determine the optimal fracture spacing. Changes in this ratio show an exponential change in fracture spacing, affecting spacing requirements by up to 81%. Poisson's ratio, Biot's parameter, and net fracture pressure were also important.

It can be concluded that fracture spacing cannot be determined by looking only at one or two properties. The fracture spacing must be determined by looking at all the important variables and identifying those that are most variable for the reservoir in question. The sensitivity of the "stress shadow" to various properties is an indication that obtaining good data is key to proper completion design.
Hydraulic Fracturing 101: What Every Representative, Environmentalist, Regulator, Reporter, Investor, University Researcher, Neighbor and Engineer Should Know About Estimating Frac Risk and Improving Frac Performance in Unconventional Gas and Oil Wells.
Authors: King George E.
Published: December 2012

Identification of risk, the potential for occurrence of an event and impact of that event, is the first step in improving a process by ranking risk elements and controlling potential harm from occurrence of a detrimental event. Hydraulic Fracturing has become a hot environmental discussion topic and a target of media articles and University studies during development of gas shales near populated areas. The furor over fracturing and frac waste disposal was largely driven by lack of chemical disclosure and the pre-2008 laws of some states.

The spectacular increase in North American natural gas reserves created by shale gas development makes shale gas a disruptive technology, threatening profitability and continued development of other energy sources. Introduction of such a disruptive force as shale gas will invariably draw resistance, both monetary and political, to attack the disruptive source, or its enabler; hydraulic fracturing.

Some "anti-frack" charges in media articles and university studies are based in fact and require a state-by-state focused improvement of well design specific for geology of the area and oversight of overall well development. Other articles have demonstrated either a severe misunderstanding or an intentional misstatement of well development processes, apparently to attack the disruptive source.

Transparency requires cooperation from all sides in the debate. To enable more transparency on the oil and gas side, both to assist in the understanding of oil and gas activities and to set a foundation for rational discussion of fracturing risks, a detailed explanation of well development activities is offered in this paper, from well construction to production, written at a level of general public understanding, along with an initial estimation of frac risk and alternatives to reduce the risk, documented by literature and case histories. This discussion is a starting point for the well development descriptions and risk evaluation discussions, not an ending point.
The Impact of Dipping Velocity Models on Microseismic Event Locations
Authors: Cabarcas C. , Saugier L. , Haas G. , Le Calvez J. , Woerpel J. C.
Published: December 2012

Once a microseism is detected, its source location can relatively easily be identified if the velocity characteristic of the medium traversed by the recorded waveforms is known. Unfortunately, this is rarely the case. Velocity models are used to estimate, with some degree of confidence, microseismic event locations. This work shows how a simple modification to the velocity model, accounting for a 4.5-degree dip supported by geological data, significantly impacts the event final locations during a borehole-based hydraulic fracturing monitoring job. Overall geometry of the hydraulically-induced fracture system interpreted (e.g. height) is the most affected. For instance, when a preliminary event location is selected without introducing the observed structural component of the beds, these measurements could change by as much as fifty percent. For the reservoir engineer, sometimes unaware of the assumptions made at the microseismic processing level, these differences could imply major changes to the field development plans. These results underscore the importance of integrating all available data and implementing well known quality controls before using microseismic monitoring data for reservoir analysis.
Sequential versus Simultaneous Multi-zone Fracturing in Horizontal Wells: Insights from a Non-planar, Multi-frac Numerical Model
Authors: Olson Jon E. , Wu Kan
Published: December 2012

Successful shale gas and tight oil applications require multiple hydraulic fracture treatments in a given horizontal well. Key design considerations are the spacing between injection zones, the size of the treatments, and the injection parameters (primarily rate and viscosity). Other important parameters are whether to inject into multiple zones simultaneously or sequentially, and whether to coordinate fracturing between multiple adjacent horizontal wells. We investigate various injection scenarios using two different "pseudo-3d" boundary element, displacement discontinuity method based hydraulic fracture simulators. A single fracture model couples the injection of non-Newtonian fluid, Carter leak-off behavior, arbitrary non-planar propagation, and height growth in a 3-layered media. The second model is designed to be more computational efficient and stable by simplifying the fracture fluid flow calculation. Fracture pressure variation through time is approximated by summing the inverse of width cubed over the created fracture network, and wellbore pressure is equated to the predicted summative pressure drop in the system. Results indicate that sequential fracturing geometries are highly dependent on injection zone spacing relative to fracture height – when fractures are closely spaced relative to stress shadow size, fracture path diversion and intersection as well as net pressure effects are likely. This strong mechanical interaction scenario promotes fracture complexity (which can be an advantage in some formations), but reduces the penetration distance of fracture wings away from the wellbore. Simultaneous fracturing of multiple stages is also strongly influenced by the spacing to height ratio – the closer the spacing the more difficult it is to get substantial growth from all completed zones.
Case History of the Fayetteville Shale Completions
Authors: Harpel J. , Barker L. , Fontenot J. , Carroll C. , Thomson S. , Olson K.
Published: December 2012

Since 2004 Southwestern Energy (SWN) has completed more than 2,000 wells in the Fayetteville shale with thousands of wells remaining to be drilled and completed. The Fayetteville is a world-class shale play stretching across central Arkansas that encompasses more than 2-million acres. Current SWN gross daily operated production is more than 1.9 BCF/D and at December 31, 2010 its proved net reserves booked in the Fayetteville were 4.3 TCF.

This paper will discuss the progression of the completions from the beginning to their current best practices. It will review the different types of completions, stimulation optimization, high efficiency operations, and well performance.
Implications of Fracturing Pressure Data Recorded during a Horizontal Completion on Stage Spacing Design
Authors: Roussel Nicolas P. , Manchanda Ripudaman , Sharma Mukul M.
Published: December 2012

Horizontal completions have changed considerably in the last few years in an effort to substantially improve the drainage of shale gas reservoirs. The spacing of fracture stages and perforation clusters are among the most crucial completion decisions that impact well productivity and EUR. Yet, the decision regarding stage spacing is rarely guided by an engineering process, as it remains a challenge to tie production performance and completion design. In this paper, we offer some insight on the impact of fracture spacing on the propagation direction of multiple transverse fractures, and consequently the expected performance of the horizontal well.

Stress-shadow effects, related to the mechanical interference induced by a proppant-filled fracture, can cause fractures initiated from a horizontal well to deviate toward or away from previous fractures. A three-dimensional geomechanical model of the combined stress interference from multiple transverse fractures has been applied to typical wells in three shale gas reservoirs: Bakken, Barnett and Eagle Ford.

The existence of an optimum spacing is demonstrated, where fracture stages remain transverse even when subject to stress-shadow effects. Below the optimum spacing, induced fractures may intersect previous fractures, and re-stimulate previously fractured regions of the reservoir, while leaving undrained portions of the reservoir un-stimulated. Such behavior is highly dependent on the mechanical properties of the shale, in particular the Young’s modulus.

Our modeling results suggest that the net fracturing pressure data measured in the field reflects the propagation direction of the fractures induced from the horizontal wellbore. A monotonic increase in net pressure, going from one stage to another, would indicate transverse fracture propagation during all stages. On the other hand, an up-and-down trend in the net pressure data is an indication that the mechanical stress interference is causing the later stage fractures to intersect fractures from previous stages. The net pressure data can, therefore, be used to investigate fracture-to-fracture interference and can be used to optimize the spacing of fracture stages in horizontal completions.
The Relationship between Psychological Factors, Inflammation, and Nutrition in Patients with Chronic Renal Failure Undergoing Hemodialysis
Authors: Wang Liang-Jen , Wu Mai-Szu , Hsu Heng-Jung , Wu I-Wen , Sun Chiao-Yin , Chou Chia-Chi , Lee Chin-Chan , Tsai Chi-Ren , Tsai Yi-Chieh , Chen Chih-Ken
Published: December 2012

Objective:

Hemodialysis has an adverse impact on the immunological, nutritional, and emotional status of patients. The biochemical markers of inflammation and nutrition were studied as well as the relationship of these factors to emotional symptoms.

Method:

One hundred and ninety-five patients undergoing hemodialysis were enrolled. The mean age was 58.5 years. Emotional symptoms were assessed using the Mini International Neuropsychiatric Interview, Hospital Anxiety and Depression Scale, Chalder Fatigue Scale, and Short-form Health-related Quality of Life. Venus blood was collected for laboratory assessment of serum hemoglobin, albumin, ferritin, C-reactive protein, interleukin (IL) 1β), IL-6, and tumor necrosis factor a.

Results:

Among the 195 subjects (92 men and 103 women), 47 (24.1%) fulfilled the criteria for a major depressive disorder (MDD). The IL-6 level in patients with a MDD was significantly higher than in the patients without a MDD. Significant correlation was observed among the following factors: IL-6, fatigue, and quality of life for both physical and mental components. The albumin levels showed a significant correlation with the IL-6 and depression scores.

Conclusions:

These results show that the serum levels of albumin and IL-6 might be laboratory markers associated with the expression of emotional symptoms in patients undergoing hemodialysis. Prospective studies are needed to determine the causal relationships among these variables.
Specific Personality Traits and Coping Styles Predict Affective Symptoms in Early Post Acute Coronary Syndrome Inpatients
Authors: De Fazio Pasquale , Caroleo Mariarita , Rizza Paolo , Cerminara Gregorio , De Serio Daniela , Indolfi Ciro , Segura-García Cristina
Published: December 2012

Objective:

Affective symptoms have adverse effects in hospital and long-term cardiac outcomes of post Acute Coronary Syndrome (ACS) patients. This study aims to identify personality traits and maladaptive coping strategies that could predict affective symptoms in early post-ACS patients.

Methods:

Seventy patients undergoing revascularization procedures were examined within a week after their admission by means of the Hospital Anxiety-Depression Scale. Personality was analyzed through the Type D Personality Scale and the Coping Inventory for Stressful Situation. Multiple logistic regression analysis was used to determine independent predictors of anxiety and depressed mood.

Results:

A high rate of depressive and anxious symptoms was found and 76% of patients resulted Type D personality. Depression was associated with b-blocker therapy, Type D personality, and specific coping strategies. Unmarried status, low education, unstable angina, Type D personality, emotion, and avoidance oriented coping independently predicted anxiety.

Conclusion:

These findings underlie the importance of assessment for Type D personality and coping strategies that could be useful to identify post-ACS patients at higher risk for affective symptoms. Using these brief instruments, as sensitive screening measures, we investigated the prevalence of depressive and anxiety symptoms in patients with ACS, we identified personality traits and coping strategies used to manage stress and estimated independent predictors of affectivity disorders after ACS.
The Impact of Media Reports on the 2008 Outbreak of Hydrogen Sulfide Suicides in Japan
Authors: Nakamura Mitsuhiro , Yasunaga Hideo , Toda Alexis Akira , Sugihara Toru , Imamura Tomoaki
Published: December 2012

Objective:

Japan experienced a nationwide outbreak of hydrogen sulfide suicides (HSS) between April and May 2008. The annual number of HSS skyrocketed from 19 in 2007 to 1,056 in 2008. However, the factors affecting this enormous increase remain unknown. The present study aimed to examine the effect of media coverage of the incidents on the subsequent epidemic of HSS.

Method:

We collected time series data from the 1st week of February to the last week of September 2008 (34 weeks), including the number of HSS (St), the number of articles on HSS published in the five major newspapers (Nt), and the number of Internet searches with the keyword “hydrogen sulfide suicide” (Gt). The generalized method of moments was applied to model the concurrent effects of Nt and Gt on St.

Results:

The increase in the number of newspaper articles significantly induced the increase in HSS (coefficient, 0.84; 95% confidence interval (CI), 0.28–5.3), while the number of Internet searches did not significantly affect the number of HSS (coefficient, −0.75; 95%CI, −19.3–0.45).

Conclusions:

Exposure to information on HSS from newspaper articles could have directly affected the subsequent increase in the number of suicides. On the other hand, the number of the Internet searches did not have a direct influence on HSS.
The Use of Clonidine in the Treatment of Nightmares among Patients with Co-Morbid PTSD and Traumatic Brain Injury
Authors: Alao Adekola , Selvarajah Jennifer , Razi Syed
Published: December 2012

Objective:

To describe the successful treatment of PTSD associated nightmares in two patients with PTSD.

Case Summaries:

The report of the successful use of clonidine to treat PTSD associated nightmares among two Veterans following combat exposure.

Discussion:

Clonidine, a centrally acting alpha-agonist agent used to treat hypertension, stimulates alpha-adrenoreceptors in the brain stem. This action results in reduced sympathetic outflow from the central nervous system. We hypothesize that this central mechanism of action is why clonidine may be more effective in treating nightmares among patients with PTSD when compared with other agents.

Conclusion:

Clonidine should be considered as an alternative in the treatment of nightmares among patients with PTSD.
Body Mass Index of Inpatients with Schizophrenia in Japan
Authors: Inamura Yukiko , Sagae Toyoaki , Nakamachi Kenichi , Murayama Nobuko
Published: December 2012

Objective:

Many studies reported that obesity rate in the Western countries is higher in schizophrenia patients than in general population. In this study, we surveyed nationwide Body Mass Index (BMI) status of hospitalized Japanese schizophrenia patients.

Methods:

Subjects included 15,171 patients (7,897 men and 7,274 women) hospitalized for schizophrenia, who were sampled from all 47 administrative divisions in Japan. The BMI data of these patients were compared to those of the general population in the 2009 National Health and Nutrition Survey conducted by the Japanese Ministry of Health.

Results:

The median BMI value in the patients was 21.6 kg/m2 (first quartile, 19.1; third quartile, 24.5). The percentages of BMI in obese, normal-weight, and underweight patients were 21.6%, 58.2%, and 20.2%, respectively. In the Japanese male patients, frequency of obesity was lower, and underweight was higher than those in the general population. In female patients, frequency of both obesity and underweight were higher than those in the general population.

Conclusions:

Our results provided evidence that underweight as well as obesity is a characteristic in Japanese schizophrenia inpatients.