bluuebunny/crossref_metadata_2025_split huggingface dataset:
Openhole Multistage Hydraulic Fracturing Systems Expand the Potential of the Giddings Austin Chalk Field
Authors: Callarotti Gian F. , Millican Steven F. 
Published: December 2012

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
"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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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.