bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparison of Flowback Aids: Understanding Their Capillary Pressure and Wetting Properties
Authors: Howard Paul R. , Mukhopadhyay Sumitra , Moniaga Nita , Schafer Laura , Penny Glenn , Dismuke Keith 
Published: May 2009

Abstract
Flowback aids are usually surfactants or cosolvents added to stimulation treatments to reduce capillary pressure and water blocks. As the gas reservoirs being stimulated become tighter, the perceived value of these additives has grown. This value must be balanced with the cost of the additives, which can be significant in slickwater fracturing treatments. There is a range of different flowback additives containing water-wetting nonionic to amphoteric, microemulsion, and oil-wetting components. Determining the best additive for a specific reservoir is not a simple matter for the end user, and the existing literature is full of conflicting claims as to which one may be most appropriate.
This paper compares four different flowback aids: microemulsion, two water-wetting flowback additives, and an oil-wetting additive. Careful laboratory testing was done to look at surface tension and contact angle for each flowback aid using the recommended concentrations. Imbibition and drainage tests were done, which allowed calculating the capillary pressures for the three additives. Drainage tests were performed on 1–3 and 0.1 mD cores. Capillary tube rise testing was also done as a check of the core flood testing capillary pressures. This provided several different methods to determine capillary forces for the flowback aids. In addition, fluid loss testing was done to determine if the flowback additives could improve fluid loss.
All the flowback aids demonstrated low surface tension (~30 dyne/cm), but each was different in terms of surface wettability and adsorption in the rock. In all cases the flowback aids reduced capillary pressure to similar levels 70% lower than water alone. One of the water-wetting additives had much stronger adsorption in the core material than the other additives. The microemulsion and the oil-wetting additive had improved fluid loss in a fully formulated fracturing fluid. In spite of the low capillary pressures, the additives had little effect on clean-up or return permeability on cores above 1 mD.
There are several implications of these results for the operator. Different flowback additives have a tradeoff of properties, and depending on the reservoir, selecting one that leaves the formation with certain wettability may be advantageous. Our testing indicated that understanding the reservoir is important in selecting the appropriate flowback aid.
New Methodology of Mini-Fall-Off Test to Optimize Hydraulic Fracturing in Unconventional Reservoirs
Authors: Ceccarelli R. L , Ciuca A. , Tambini M. 
Published: May 2009

Abstract
Operative and economical optimization of hydraulic fracture stimulation designs requires accurate reservoir description.
For unconventional tight gas reservoirs is it commonly difficult obtain reliable results from conventional build up analysis after flow testing a well because the time required to reach the IARF (Infinite Acting Radial Flow) could be much longer than normal rig time operations will practically allow. In many cases the impossibility of the well to produce after perforation makes the scenario even worst.
Mini-Fall-Off injection test is economical and efficient technical solution to solve this problem providing an excellent starting point to understand unconventional plays and optimize the entered process of hydraulic fracturing technique.
The scope of this work is to present an optimal operative processes which allow understand how, when and where is recommended apply this technology giving a key point to optimize the hydraulic fracture stimulation. Following a theoretical description to this new methodology is provided.
In addition, this work includes a detailed guideline for planning execution and interpretation of the falloff pressure to obtain reliable reservoir transmissibility, reservoir pressure and closure pressure.
Finally, the results of two cases were evaluated and it was determined that a simple field implementation could be adopted as a standard to be used in conventional pre-frac pumping procedures.
Acid-Fracture Conductivity Correlation Development Based on Acid-Fracture Characterization
Authors: Pournik M. , Zhu D. , Hill A. D. 
Published: May 2009

Abstract
Acid fracturing is a stimulation process in which the dissolution of formation rock leaves unevenly etched fracture faces that creates lasting conductivity after fracture closure. The success of acid fracturing depends on the conductivity created and retained under overburden stress in addition to the length of conductive fracture. In order to have sufficient conductivity after fracture closure, the fracture face must be non-uniformly etched by the acid while the strength of the rock is still maintained at high levels to withstand the closure stress.
A systematic experimental study to investigate the effect of etching pattern and rock strength on the resulting fracture conductivity was conducted in a laboratory facility designed to perform acid fracture conductivity characterization. Detailed etched surface characterization and rock strength measurement were performed on acid etched fracture faces in order to correlate to resulting conductivity.
Resulting fracture conductivities clearly show the importance of characterizing acid etching patterns. In evaluating the measured fracture conductivities, we distinguished between those tests in which a prominent channel was created along the middle of the rock samples from those tests in which more uniformly distributed roughness features were created on the fracture faces. The channels developed in small scale laboratory tests are likely artifacts of the apparatus and cannot be expected to scale to field conditions.
For the roughly etched fracture faces, statistical parameters describing the surface roughness in addition to average fracture width were needed to accurately predict measured conductivities. Both etched pattern characterization and resulting conductivity measurements suggested the need to model conductivity of limestone and dolomite samples separately. New conductivity correlations were developed both for limestone and dolomite formations which matched the experimental results better than previous correlations.
Fluid Diversion Monitoring: The Key to Treatment Optimization
Authors: Glasbergen Gerard , Yeager Valerie , Reyes Robert , Everett Don 
Published: May 2009

Abstract
In stimulation and injection treatments for removing or preventing formation damage, placement of the injected fluids is essential. Throughout the years, several diversion and placement techniques have been applied to obtain a desired fluid placement. A recent development is the application of distributed temperature sensing (DTS) to monitor the temperature profiles along the wellbore in real time during these treatments. Recent case histories showed that fluid placement can be quantified. Quantification of fluid distribution enables one to determine the flow distribution both before and after a diverter stage so that the diversion effect can be quantified.
This paper discusses several case histories where DTS was applied to quantify the effectiveness of different diverters. The effects of chemical diverters, such as relative permeability modifiers (RPM) and in-situ crosslinked acids (ICAs), and more traditional diverters, such as rock salt, are discussed. Because of the advanced monitoring used with the temperature profiles, both the immediate and the sustained effect of the diverters can be measured. The changes in the flow distribution are not limited to diverters. Reactive fluid or changes in flow rate can change the flow distribution as well. These effects were measured during the stimulation treatments.
The post-treatment analysis of the measured temperature profiles in combination with treatment pressures and flow rate information resulted in accurate knowledge of the effectiveness of the different diverters and stimulation effects over time. This knowledge will be used in future treatments to help optimize volumes, rates, fluid systems, and the selection of the appropriate diverter.
Understanding the Near-wellbore Phenomena for Hydraulically Fractured wells: A Comprehensive Inflow Performance Numerical Model
Authors: Jimenez Maria-Alejandra , Chavez Juan Carlos 
Published: May 2009

Abstract
Comprehensive hydraulic fracture simulation models have been used to predict fracture propagation behaviour, geometry and conductivity. Extensive studies have been made in order to calibrate and assess the accuracy of these predictions; this has made possible the development of highly accurate models such as the 3D fracture simulation programs currently in use. However, when estimating the production performance of the hydraulically fractured wells, an essential step during hydraulic fracture designs, in most cases analytical approaches are used, which have the limitation that they that cannot reproduce the complexities associated with flow from the near wellbore area into the well.
The introduction of formation damage (skin) factors to account for the complexities associated with the flow in the near wellbore area further limits understanding as to how the sand-face completion and final fracture design interact, limiting the ability to provide an optimum implementation that maximises the well performance.
A comprehensive numerical model, which considers Computational Fluid Dynamics (CFD), was used to estimate the inflow performance of single and multiple fractured wells, taking into consideration reservoir heterogeneities and completion characteristics. Porous media inertial and viscous effects were accounted for, considering different sets of values for the formation and the fracture(s) domains. 3D CFD was used to identify the impact of the perforation strategy, multilayer reservoir fracture intersection, multiple fractures and petrophysical heterogeneities on well performance for oil reservoirs. The study demonstrates, through the detailed understanding of the inflow in the near wellbore area, that it is possible to optimize the sand-face completion design and has been applied on a field re-development project on a multilayer reservoir system.
The use of CFD supported by today's available computational capabilities, provides the base platform to increase the understanding of the near wellbore flow behaviour in fractured wells leading to optimum sand-face completion and final production performance.
New Fundamental Insights into Perforation-Induced Formation Damage
Authors: Heiland Juliane , Grove Brenden , Harvey Jeremy , Walton Ian , Martin Andrew 
Published: May 2009

Abstract
Shaped charge perforating subjects the formation to shock-loading and large impact stresses, causing damage to the rock surrounding the perforation tunnel. This damage can lead to reduced productivity and to an enhanced risk of sand production, both of which are undesirable. The impact stresses fracture sand grains in the vicinity of the perforation tunnel, resulting in a zone of reduced permeability called the crushed zone. Additionally, the impact stresses plus the outward traveling shock wave severely weaken the rock matrix by de-bonding the cohesive inter-granular cementation, leading to the creation of a zone of reduced strength called the damage zone. As a result, the damage zone extends to a greater depth than the crushed zone. This weakened damage zone is an important factor in crushed zone removal and in the onset of sand production.
An essential first step in modeling perforation clean-up is to characterize the extent and magnitude of both the permeability and strength impairment. An indirect measure of the amount of permeability impairment created by the perforating process is obtained from perforation flow experiments, where the post-shot production flow is compared to an idealized flow measurement in the virgin rock. Direct measurement of the extent of the crushed and damaged zones, and the degree to which strength and permeability damage occurred has received very little attention. In this paper new methods are described to directly determine the extent of the strength and permeability damage caused by shaped-charge penetration. The crushed zone permeability impairment is characterized using thin section analysis and the strength damaged zone is characterized using a Scratch-Tester. These methods allow the quantitative assessment of both damage zones,. The implications of the results for productivity impairment and sand production will be discussed.
Leksell's posteroventral pallidotomy in the treatment of Parkinson's disease
Authors: Laitinen Lauri V. , Bergenheim A. Tommy , Hariz Marwan I. 
Published: May 2009

✓ Between 1985 and 1990, the authors performed stereotactic posteroventral pallidotomies on 38 patients with Parkinson's disease whose main complaint was hypokinesia. Upon re-examination 2 to 71 months after surgery (mean 28 months), complete or almost complete relief of rigidity and hypokinesia was observed in 92% of the patients. Of the 32 patients who before surgery also suffered from tremor, 26 (81%) had complete or almost complete relief of tremor. The L-dopa-induced dyskinesias and muscle pain had greatly improved or disappeared in most patients, and gait and speech volume also showed remarkable improvement. Complications were observed in seven patients: six had a permanent partial homonymous hemianopsia (one also had transient dysphasia and facial weakness) and one developed transitory hemiparesis 1 week after pallidotomy.
The results presented here confirm the 1960 findings of Svennilson, et al., that parkinsonian tremor, rigidity, and hypokinesia can be effectively abolished by posteroventral pallidotomy, an approach developed in 1956 and 1957 by Lars Leksell. The positive effect of posteroventral pallidotomy is believed to be based on the interruption of some striopallidal or subthalamopallidal pathways, which results in disinhibition of medial pallidal activity necessary for movement control.
Current results of the retrosigmoid approach to acoustic neurinoma
Authors: Ebersold Michael J. , Harner Stephen G. , Beatty Charles W. , Harper C. Michel , Quast Lynn M. 
Published: May 2009

✓ Since 1984 when cranial nerve monitoring became routinely performed at the Mayo Clinic, 255 patients have undergone 256 procedures using the retrosigmoid approach for the removal of acoustic neurinomas. Of these, 221 patients had some hearing before surgery and 52 maintained hearing following surgery. The anatomical continuity of the facial nerve was preserved in 237 of these 256 procedures. It was possible to perform a primary end-to-end anastomosis in seven of the remaining 19 patients, and one patient had a cable graft inserted. Thus, 95.7% of these patients were believed to have potential for spontaneous facial nerve function. Of the 11 patients in whom this was not possible, seven underwent early spinal accessory facial anastomosis, in two hypoglossal-facial anastomosis was performed, and two had no facial nerve procedures and have paralysis of the facial nerve.
There were two deaths from a pulmonary embolus in the early postoperative period, both 4 days following otherwise uneventful surgery. The most common postoperative complication was cerebrospinal fluid leakage, which has not resulted in significant permanent morbidity although early repair for this problem is now routinely recommended. Other complications were quite rare and have generally not resulted in any major change in patient lifestyle or activity level. This review reconfirms that the retrosigmoid surgical treatment of acoustic tumors continues to be an acceptable treatment option.
Reconstruction of the third through sixth cranial nerves during cavernous sinus surgery
Authors: Sekhar Laligam N. , Lanzino Giuseppe , Sen Chandra N. , Pomonis Spiros 
Published: May 2009

✓ Sixteen reconstruction procedures of the third through sixth cranial nerves were carried out in 14 patients during operations on 149 tumors involving the cavernous sinus. A direct end-to-end anastomosis was performed in five nerves, whereas in 11 cases the nerve stumps were bridged by means of an interposing nerve graft. The sixth cranial nerve was most frequently reconstructed (nine cases). In four cases, the fifth nerve or root was repaired. The third nerve was reconstructed in two patients, and the fourth nerve was repaired in only one case.
Recovery of function, either partial or complete, was observed in 13 nerves: the third in two instances, the fourth in one, the fifth in three, and the sixth in seven. No return of function occurred in three nerves. In patients with a successful recovery of cranial nerve function, either binocular function or the cosmetic result was improved. These results suggest that repair of the third through sixth cranial nerves injured during surgery should be pursued in suitable patients.
Patient-interactive, computer-controlled neurological stimulation system: clinical efficacy in spinal cord stimulator adjustment
Authors: North Richard B. , Fowler Kim , Nigrin Daniel J. , Szymanski Richard 
Published: May 2009

✓ Over the past 20 years, continuing technical advances have rendered spinal cord stimulation an easily implemented low-morbidity technique for the management of chronic intractable pain in properly selected patients. Percutaneous methods for the insertion of arrays of multiple epidural electrodes, which are driven by noninvasively programmable “multichannel” implanted devices, have been among the most important of these technical improvements. The same implanted electronics may be used with peripheral nerve or intracerebral electrodes.
If the capabilities of this new hardware are to be used to full advantage, a major investment of time and effort is required to adjust the system postoperatively for optimum effect. Ideally, these adjustments should be based upon psychophysical data, obtained in a manner that minimizes influences such as potential operator bias or stimulus presentation-order effects.
These requirements have been met by the development of a computerized system designed for direct patient interaction and for greater ease of operation than the standard external devices used with these implants. The system has been tested clinically in 25 patients with spinal cord stimulation for pain. It rapidly tests the available electrode combinations and stimulus pulse parameters at a rate comparable to or greater than that of a skilled human operator using the standard device. It records detailed graphic data and patient analog ratings at varying thresholds and implements “pain drawing” methods with novel input and analytical techniques.
This patient-interactive computerized system has proved to be safe and effective clinically. The time required by the average patient working with this system to adjust the stimulator is comparable to or less than the time required by the same patient working with a physician's assistant. Psychophysical data collected by the system may be correlated with clinical observations. Ongoing development will permit delivery of novel pulse sequences and protocols to assess the mechanisms by which stimulation affords relief from pain.
Clinical outcome of radiosurgery for cerebral arteriovenous malformations
Authors: Steiner Ladislau , Lindquist Christer , Adler John R. , Torner James C. , Alves Wayne , Steiner Melita 
Published: May 2009

✓ The clinical outcomes are described for 247 consecutive cases of arteriovenous malformation (AVM) treated with the gamma knife between April, 1970, and December 31, 1983. Headache resolved in 65 (66.3%) of the 98 patients presenting with this symptom and improved in an additional nine (9.2%). Of 59 patients admitted with seizures, 11 (18.6%) became seizure-free without anticonvulsant medication and an additional 30 patients (50.8%) became seizure-free with anticonvulsant medication. Pre-existing neurological deficits improved or totally disappeared following radiosurgery in 56.7% of affected cases. This improvement presumably occurred within the frame of the natural history.
The protective effect of the ionizing beams against hemorrhage in incompletely obliterated AVM's is analyzed. To assess the rate of rebleeding, probability estimates were calculated using both the person-year method and the Kaplan-Meier life table. With the person-year method the actual rebleed rate is not too different from the values observed in the natural history of the disease (2% to 3%/yr). Analysis by Kaplan-Meier life-table estimates demonstrated a risk of nearly 3.7%/yr until 60 months after radiosurgery. Five years following treatment, the life table ends in a plateau which could be interpreted as an indication of decrease in the risk of hemorrhage. However, long flat regions at the right end of the life table do not imply that the real risk of rebleeding is negligible unless a large number of patients have been followed well into or beyond the flat region.
The effect of changes in cerebral perfusion pressure upon middle cerebral artery blood flow velocity and jugular bulb venous oxygen saturation after severe brain injury
Authors: Chan Kwan-Hon , Miller J. Douglas , Dearden N. Mark , Andrews Peter J. D. , Midgley Susan 
Published: May 2009

✓ Middle cerebral artery blood flow velocity and jugular bulb venous oxygen saturation (SJO2) were measured by transcranial Doppler (TCD) ultrasonography and continuous venous oximetry, respectively, in 41 severely brain-injured patients. The purpose of the study was to examine the relationships between TCD flow velocity, SJO2, and alterations in blood pressure (BP), intracranial pressure (ICP), and cerebral perfusion pressure (CPP).
In these patients, CPP was reduced either by rising ICP or by falling BP. Both forms of reduction of CPP resulted in a greater fall in diastolic flow velocity than other flow parameters. As CPP decreased below a critical value of 70 mm Hg, a progressive increase in TCD pulsatility index (PI) was observed (r = −0.942, p < 0.0001), accompanied by a fall in SJO2 (r = 0.78, p < 0.0001). At pressures above 70 mm Hg, there was no correlation of either PI or SJO2 with CPP. The relationship between PI and CPP held true in patients with both focal and diffuse pathologies and was the same whether changes in CPP resulted from alterations in ICP or BP. The PI and SJO2 correlated better with CPP than with ICP or BP.
Transcranial Doppler ultrasonography can identify states of reduced CPP. Decreases in SJO2 with falling CPP suggested progressive failure of cerebral blood flow to meet metabolic demands. Monitoring of TCD and SJO2 may be used to define the optimum CPP level for management of severely brain-injured patients.