bluuebunny/crossref_metadata_2025 huggingface dataset:
Rates of Parent-Centered Developmental Screening: Disparities and Links to Services Access
Authors: Bethell Christina , Reuland Colleen , Schor Edward , Abrahms Melinda , Halfon Neal
Published: June 2011

BACKGROUND:

In 2006, the American Academy of Pediatrics recommended developmental screening of young children with a standardized screening tool as a routine component of well-child care.

OBJECTIVES:

To assess the national and state prevalence of standardized, parent-completed developmental screening (DS-PC) in the previous 12 months and evaluate associations between screening and receipt of an early-intervention plan or mental health services for children at higher risk.

METHODS:

Data from the 2007 National Survey of Children's Health were used. Nested t tests were used to compare each state to national prevalence. Logistic and multilevel regression models evaluated variations and associations with DS-PC.

RESULTS:

Nationally, 19.5% of children received a DS-PC in the previous 12 months, although the figure varied from 10.7% to 47% across the United States. Prevalence did not rise above 26.7% for any socioeconomic subgroup of children and was highest for younger, black, and publicly insured children and lowest for uninsured children and children with gaps in insurance coverage. Equally high-risk children varied twofold in their probability of receiving early intervention or needed mental health services according to whether they had received a DS-PC.

CONCLUSIONS:

There is a significant gap between the developmental screening that is recommended and what is reported nationally. When children are not screened consistently, opportunities for early identification, intervention, and treatment may be delayed. Gaps in screening and wide variations across states present considerable opportunities for cross-state learning to improve quality on this critical component of preventive pediatric care. Measurement systems for assessing prevalence and impact of screening require continued evaluation and development.
Sexual History Documentation in Adolescent Emergency Department Patients
Authors: Goyal Monika , McCutcheon Marin , Hayes Katie , Mollen Cynthia
Published: June 2011

OBJECTIVES:

To determine the frequency of physician-documented sexual histories in female adolescents who presented to an emergency department (ED) with symptoms suggestive of a sexually transmitted infection (STI). Our secondary objectives were to determine if physician-documented sexual history is associated with increased STI testing and to compare the concordance of physician-elicited sexual histories with patient-documented sexual histories by using confidential questionnaires.

METHODS:

We conducted a secondary analysis of a prospective study of female adolescents who presented to a pediatric ED with chief complaints of lower abdominal pain and/or genitourinary complaints. Patient charts were abstracted for the presence or absence of documented sexual histories and demographics. A subset of patients completed a questionnaire pertaining to sexual health.

RESULTS:

The study population comprised 327 patients; 269 (82%) patients had a physician-documented sexual history, of which 204 (76%) reported being sexually active to the physician. Patient age (odds ratio [OR]: 2.6 [95% confidence interval (CI): 1.3–5.3]) and black race (OR: 2.0 [95% CI: 1.1–3.7]) were associated with physician-documented sexual history. The documentation of a sexual history was associated with increased STI testing (OR: 3.9 [95% CI: 2.0–7.6]). In the patients (n = 109) who completed the questionnaire, physician-elicited sexual histories were highly concordant with patient-documented sexual histories on questionnaire (Spearman r = 0.90; P < .001).

CONCLUSION:

These results indicate that ED physicians should obtain sexual histories from symptomatic patients, because it may increase STI testing and subsequent detection. In future studies factors should be evaluated that affect physicians' willingness to assess sexual history in the ED patient.
Targeting Inflammation to Prevent Bronchopulmonary Dysplasia: Can New Insights Be Translated Into Therapies?
Authors: Wright Clyde J. , Kirpalani Haresh
Published: June 2011

Bronchopulmonary dysplasia (BPD) frequently complicates preterm birth and leads to significant long-term morbidity. Unfortunately, few therapies are known to effectively prevent or treat BPD. Ongoing research has been focusing on potential therapies to limit inflammation in the preterm lung. In this review we highlight recent bench and clinical research aimed at understanding the role of inflammation in the pathogenesis of BPD. We also critically assess currently used therapies and promising developments in the field.
Academy of Pediatric Education and Leadership: Preparing Leaders for Educational Innovation
Authors: Hobson Wendy L. , Carey John C. , Bale James F.
Published: June 2011

Faculty development has been identified as a critical need if we hope to advance competency-based education. Despite the small number of participants at a single institution, the model presented here has the possibility for making a significant contribution to future faculty development initiatives for two reasons. First, by supporting the time of the scholars, the program makes a statement about the value of medical education and the recognition that it requires a skill set to become an educator. While the need for requisite skill sets has long been recognized for training sub-specialists, this has not been the case for those taking on major roles in education and training. Second, despite a rich literature, little has been published about the effects on the learners of those who participated in the faculty development programs. By supporting a cadre of individuals to acquire the skills needed to be an educator as well as the skills needed to perform educational research to study the impact of applying those skills, this project serves as a model for developing a much needed community of medical education leaders.

Carol Carraccio, MD, MA
Uso da Classificação Internacional de Doenças na análise do absenteísmo odontológico
Authors: Togna Gisele dos Reis Della , Crosato Edgard , Melani Rodolfo Francisco Haltenhoff , Michel-Crosato Edgard , Biazevic Maria Gabriela Haye
Published: June 2011

OBJETIVO: Comparar o uso das codificações da classificação de doenças e agravos em solicitações de afastamento do trabalho por motivo odontológico. MÉTODOS: Foram analisadas 240 solicitações emitidas em um serviço público federal entre janeiro de 2008 e dezembro de 2009. O uso da Classificação Estatística Internacional de Doenças e Problemas Relacionados à Saúde - Décima Revisão (CID-10) foi comparado ao sistema de Classificação Internacional de Doenças em Odontologia e Estomatologia (CID-OE). Foi determinada a especificidade da codificação nas solicitações de afastamento, bem como da codificação atribuída por peritos oficiais em inspeções indiretas, perícias e juntas odontológicas. RESULTADOS: Do total de atestados, 22,9% não apresentaram a CID, 7,1% apresentaram a CID-9, 3,3% a CID-OE e 66,7% a CID-10. A maioria das codificações foi concordante (55,1%), com maior especificidade nas codificações atribuídas após avaliação dos cirurgiões-dentistas peritos oficiais. CONCLUSÕES: É necessário aperfeiçoar a utilização da CID-10 entre os profissionais de Odontologia e perícia odontológica no trabalho. Sugere-se a incorporação do uso da CID-OE e da Classificação Internacional de Funcionamento, Incapacidade e Saúde para a análise dos afastamentos do trabalho, fornecendo dados relevantes para o monitoramento do absenteísmo por motivo odontológico.
Irrompimento do primeiro molar permanente em crianças de 5 e 6 anos de idade: implicações da análise longitudinal para prevenção da cárie oclusal
Authors: Frazão Paulo
Published: June 2011

O tempo de irrompimento dentário é essencial para o planejamento de medidas de prevenção da cárie oclusal. Com a ampliação do ensino fundamental de oito para nove anos de duração, um número maior de crianças entre cinco e seis anos de idade é incluído na primeira série do ensino fundamental. OBJETIVO: O objetivo foi estimar as tendências do irrompimento dos primeiros molares permanentes em meninos e meninas de 5 e 6 anos de idade. MÉTODOS: Em estudo longitudinal, espaços dentários de 497 crianças de 60 meses e mais de idade foram examinados quatro vezes por um dentista calibrado (kappa > 0,97) durante 18 meses. O primeiro molar permanente foi considerado irrompido quando qualquer parte de sua superfície podia ser tocada por uma sonda de ponta esférica. A idade dos participantes foi medida em meses. Intervalos para 95% de confiança dos valores de prevalência e incidência foram apurados conforme o sexo para três coortes etárias: 60,0 a 65,9; 66,0 a 71,9; 72,0 a 77,9 meses. A razão entre as taxas de incidência foi estimada por meio de análise de regressão de Poisson. RESULTADOS: A maioria das crianças entre 66,0 e 71,9 meses e entre 72,0 e 77,9 meses tem pelo menos um molar permanente irrompido. No grupo de 66,0 a 71,9 meses, de cada três crianças pelo menos uma apresentou os quatro primeiros molares permanentes irrompidos. CONCLUSÃO. As tendências de irrompimento observadas justificam a necessidade da adoção de medidas de vigilância e de proteção específica em relação à lesão de cárie oclusal.
The Effect of HIV Field-Based Testing on the Proportion of Notified Partners Who Test for HIV in New York City
Authors: Renaud Tamar C. , Wong Melissa R. , Bocour Angelica , Udeagu Chi-Chi N. , Pickett Leonard , Alt Elizabeth N. , Sepkowitz Kent A. , Begier Elizabeth M.
Published: June 2011

HIV partner services can effectively reach populations with high HIV prevalence. However, located and notified sex and needle-sharing partners of persons infected with HIV often fail to test. Field testing may increase the proportion of notified partners who test for HIV. In 2008, New York City's health department incorporated field testing into partner services. After the introduction of field testing, the proportion of notified partners who tested for HIV rose from 52% to 76% (P<.001). HIV prevalence fell slightly among notified partners who accepted testing (12% to 9%, P=.82), but we identified more than double the number of new positives (11 vs 25). All positive and 97% of negative results were received by the person tested.
Alternatives to Minimize Scale Precipitation in Carbonate Cores Caused by Alkalis in ASP Flooding in High Salinity/High Temperature Applications
Authors: Bataweel M. A. , Nasr-El-Din H. A.
Published: June 2011

Studying formation damage caused by chemical enhanced oil recovery (EOR) in a high-temperature/high-salinity (HT/HS) reservoir will help in developing guidelines to improve EOR performance during alkaline/surfactant/polymer (ASP) flooding by minimizing negative interactions between chemicals and reservoir components. Formation brines that have high concentrations of Ca2+ and Mg2+ can interact with injected fluid and cause precipitation and loss of injectivity. Operators during some ASP field studies have noticed negative interactions between injected chemicals with formation rock and fluids that resulted in scaling after initiation of ASP flooding.

Several alkalis were evaluated to assess their scaling potential in high salinity formation brines and seawater as mixing brine at high temperatures. Four alkalis were evaluated; three inorganic alkalis sodium hydroxide, sodium carbonate, and sodium metaborate, and one organic alkali.

In this study we evaluate the application of two novel alkalis and include scale inhibitor in the chemical slug to minimize precipitation of the sodium carbonate (alkali) when mixed with formation brine. Using organic alkali eliminates the need to soften the mixing brine and will result in expanding the ASP application to more challenging applications and reduce the softening cost for the mixing water. Including the scale inhibitor did assist in reducing the permeability loss as expected.
Service for Dynamic Scale Removal of Barium Sulfate in Perforation Tunnels
Authors: Harive Kevin , Le Cam , Abdel Khalek Mohamed
Published: June 2011

There has been a substantial decline in production of wells drilled in Libya over the last 30 years. This sharp, early decline suggests that significantly increased drilling will be necessary in the near future to sustain the country's oil and gas production. With the increasing cost of drilling and completing new wells, attention was focused on the depletion rates and the reasons behind them.

Through offset well data and extensive field knowledge, the producer concluded that the most likely scenario was scale buildup. Data indicated that the scale was barium sulfate (BaSO4), which accumulated in the perforation tunnels, impeding the flow of the hydrocarbons to the production string and, in essence, to the surface facilities.

A cost-effective intervention method to restore the production to the previous producing rates was requested. The intervention would have to be done without suspending the well as well as have the ability to bring back samples of the scale for further testing.

This paper presents a case history of the successful removal of barium sulfate (BaSO4) without killing the well or costly chemical intervention. The method harnesses the effects of dynamic underbalance, sound engineering interpolation, and the versatility of the SurgePro™ software to optimize the job design.
The Effect of Fracture Face Matrix Damage on Productivity of Fractured Wells with Infinitive and Finite Fracture Conductivities in Shale Gas Reservoirs
Authors: Guo Boyun , Ganjy Ershad , Gao Deli , Ai Chi
Published: June 2011

Producing natural gas from shale gas reservoirs presents a great challenge to the petroleum engineers because of the low permeability nature of this type of gas reservoirs. Large scale and expensive hydraulic fracturing operations are often required for enhancing gas well productivity. Due to the shally characteristics of the reservoir rock, the hydraulically fractured gas wells are very vulnerable to the damage by the fracturing fluids. However, the significance of the formation damage due to different causes in fractured wells is still not clear. It is highly desirable to have a simple method for predicting the degree of fracture face matrix damage and optimizing fracturing treatment. This paper fills the gap.

A new mathematical model was developed in this study to predict the effect of fracture face matrix damage on productivity of fractured gas wells in shale gas reservoirs. A unique feature of the new model is that it considers reservoir-fracture crossflow in finite conductivity fractures. Results of the model analyses were sensitized to reservoir properties and facture face matrix skin properties determined by the fracturing fluid properties and treatment conditions. Large ranges of possible leak-off coefficient and spurt-loss coefficient were investigated. We concluded that the significance of fracture face matrix damage to well productivity depends on reservoir properties (porosity and permeability) and fracturing fluid properties (leak-off coefficient, spurt loss coefficient, and viscosity). Reservoir properties determine the vulnerability of formation damage, while fluid properties controls the degree of formation damage. The productivity index ratio (PIR) for describing the significance of formation damage drops non-linearly with leak-off coefficient and damage permeability ratios. In the practical range of the leak-off coefficient, the PIR analysis reveals that well productivity should drop by less than 15% even the residual permeability is 5% of the virgin reservoir permeability in the damage zone. Accurate prediction of the effect of fracture face matrix damage on well productivity with this model requires conducting laboratory test to determine the residual permeability in the damaged zone for a given shale gas reservoir.
Comparison of Skin Factors for Perforated Completions Calculated with Computational Fluid Dynamics Software and a Semi-Analytical Model
Authors: Sun Datong , Li Baoyan , Gladkikh Mikhail , Satti Rajani , Evans Randy
Published: June 2011

There are many factors affecting flow performance of perforated completions. These factors include perforation tunnel geometry, drilling and perforation damage, formation anisotropy, etc. The combined effect of these factors is usually accounted for via a single parameter – total skin factor, which is an important input parameter for Inflow Performance Relationship (IPR) prediction and reservoir simulation. The commonly used semi-analytical skin factor model assumes total skin factor can be expressed as a linear combination of horizontal skin, vertical skin considering anisotropy, perforation-damaged-zone skin, and other skins. The purpose of this study is to investigate the validity of the semi-analytical model in the realistic operational range of perforating parameter values.

For this purpose, we use computational fluid dynamics (CFD) software to simulate the production flow of a cased-and-perforated well in a representative 3D geometric formation. We consider three effects: drilling damage, perforation damage (crushed zone around the perforation tunnel), and anisotropy, assuming no pressure drop along the interior of perforation tunnel. All combinations of the three effects are considered. Computed skins are compared with the semi-analytical skin model used in the industry.

Computed results show good comparisons between skin factors calculated using CFD software and the model for most cases. However, significant deviations in skin factor comparisons are observed when both perforation damage and formation anisotropy exist. We also conclude that an additional skin factor term, related to the ratio of modified wellbore radius to the original wellbore radius, should be explicitly listed in the model for the case of perforations tunnel extending beyond the drilling damage zone.

Calculated CFD skin factors can be used as a database for predictive pre-job analysis. Deviation between skin factors calculated using CFD and the model highlights the need for improving industry methods to estimate skin factor in perforated completions.
Optimizing Fracture Geometry and Productivity in High Permeability Reservoirs
Authors: Armirola F. , Pinto C. , Machacon M. , Lastre M. , Milne A. , Bravo O.
Published: June 2011

In the Llanos basin of Colombia, there are shallow, highly permeable, poorly consolidated sandstone reservoirs close to oil-water contacts. The Carbonera formation is typical—several small, highly permeable (600 to 3000 mD) producing sands, with poorly defined barriers. High production rates and low bottom hole flowing pressures (BHFP) result in water coning and sand production. One solution is a stacked frac-pack completion.

In these applications, conventional cross-linked fracturing fluids have limitations. High polymer concentrations and viscosity are required to control fluid leak-off and create a sufficiently wide hydraulic fracture to admit proppant. High fluid viscosity has led to uncontrolled fracture growth into oil-water contacts, while the high polymer concentration decreases fracture conductivity and effective half-length.

A linear fluid comprised of polyacrylamide and polysaccharide polymers has proved an effective solution. The polyacrylamide greatly enhances fluid efficiency and elasticity, while reducing friction pressures and horsepower requirements. Fluid elasticity ensures adequate proppant transport. Fluid efficiency is determined by the polyacrylamide concentration and adjusted to achieve the required fracture geometry. The use of this fluid along with a geomechanical model and pseudo 3D fracturing simulator ensures that the propped fracture remains within the producing sand, with increased effective fracture half-length and conductivity. The polyacrylamide reduces the effective permeability to water and limits potential conning, when the well is produced.

Wells completed with frac-packs using the linear fluid produce an average of 1420 bbl/day of fluid with 20% water-cut. The fluid efficiency during the treatments varies between 30% and 15% as a function of permeability. Offset conventionally gravel packed wells with a lower bottom hole flowing pressure (BHFP) average 980 bbl/day of fluid with 60% water-cut.

Frac-packs, using an efficient linear fluid together with a geomechanical model and a pseudo 3D fracturing simulator have greatly improved the economics of producing these highly permeable reservoirs—maximizing production and recoverable reserves, while minimizing water production.
Combining Matrix Stimulation and Gravel Packing Using a Non-acid Based Fluid
Authors: Armirola F. , Machacon M. , Pinto C. , Milne A. , Lastre M. , Miquilena E.
Published: June 2011

The CaraCara field in the Los Llanos area of Colombia is a highly permeable (1 − 3 Darcy) sandstone with more than 10% total clay content, producing heavy crude. Gravel packing is required to avoid sand production. However, the Productivity Index after conventional gravel packing is only 50% of the open-hole potential due to drill-solids—calcium carbonate —plugging the matrix and fines migration. Non-acid and acid based preflushes have been used to dissolve the drill-solids and fines in the critical near wellbore matrix respectively. However, corrosion, uncontrolled filter cake dissolution, sludging with heavy crude and disposal of spent acid limits the use of acid pre-flushes.

A recently developed non-acid based fluid capable of stimulating high temperature sandstone formations was taken as the starting point to develop a customized solution to remove formation damage and control fines migration for this particular application. The base fluid is chelant such as diammonium EDTA (DAE) to which a low concentration of HF acid is added, most commonly in the form of ammonium bifluoride. The HF acid greatly increases the dissolution of aluminosilicates, while the chelant prevents the precipitation of silica gel. The addition of boric acid effectively retard the dissolution rate of the fluid as boric acid the reacts with the HF acid to form fluoroboric acid (HBF4) which slowly hydrolyses to release HF acid. Fluroboric acid also provides an effective means of fines migration control. By adjusting the concentration of acid salts in the fluid as a function of temperature the fluid can provide effective controlled filter cake removal, matrix stimulation and fines migration control, at temperatures between 120 and 300°F.

The newly developed non-acid fluid system provides some unique advantages for gravel packing and matrix stimulation applications in highly permeable heavy oil reservoirs 1) A single carrier fluid, eliminating the need for preflushes 2) Controlled filter cake dissolution ensuring circulation is maintained while gravel packing horizontal wells. 3) Effective fines migration control. 4) Scale inhibition. 5) Crude compatibility and negligible corrosion rates.

In one field the average productivity index of vertical wells completed using this fluid increased from 0.2 bbl/psi to 0.9 bbl/psi. The final skin values were close to zero and the production remained stable for an extended period of time. A similar fluid when used in horizontal well applications reduced the cleanup time from days to hours. The ability to stimulate while gravel packing optimizes the productivity of dirty sandstones while minimizing the cost.
Engineering Drill-in Fluids to Improve Reservoir Producibility
Authors: van Zanten Ryan , Horton David , Tanche-Larsen Per-Bjarte
Published: June 2011

Preventing formation damage is the primary objective of a drill-in fluid. Damage can occur through many different mechanisms including emulsion blocks, water blocks, polymer/filtrate/particle invasion, precipitates, and improper wetting of the formation. Damage can be remediated by stimulating the formation through fracturing, acidizing or improving flow-back with chemical treatments; however, these post-drilling treatments can significantly increase well construction costs.

Ideally a reservoir drill-in fluid will be tailored to prevent formation damage and protect the producibility of the well. Current methods such as viscosifying filtrate can be engineered to minimize filtrate invasion along with utilizing acid-degradable fluid loss control polymers/bridging particles. Verifying compatibility between the drill-in fluid and formation fluids can help prevent blockages from precipitates or scale. Although it can be minimized, filtrate invasion in water-based drill-in fluids is typically higher than in oil-based drill-in fluids, and such invasion can adversely impact producibility.

This paper investigates the effect of chemical treatments added to the fluid that alter formation wettability and/or eliminate emulsion blocks in oil wells or water blocks in gas wells whilst being penetrated during the drilling process. By applying these treatments, water- and brine-based fluids can achieve return permeabilities similar to oil-based drill-in fluids. The invading aqueous filtrate can be used as a production enhancement tool, allowing us to achieve improved formation producibility. This paper describes the development of a unique technique to chemically alter the drill-in fluid such that the invading filtrate alters the producing rock to optimize production. This can reduce or eliminate the need for remedial treatments and can decrease damage from certain fluid additives such as lubricants and corrosion inhibitors.
Understanding Drill in Fluid Invasion into Multi Layer Reservoirs Satured by Compressible Fluids
Authors: Waldmann A. T. , Martins A. L. , Dannenhauer C.
Published: June 2011

Minimizing fluid invasion is a major issue while drilling reservoir rocks. Large invasion may create several problems in sampling reservoir fluids in exploratory wells. Besides, drilling fluid invasion may also provoke irreversible reservoir damage reducing its long term productivity. A common practice in the industry is the addition of bridging agents in the drilling fluid composition, such as calcium carbonates. Such products would form a low permeability layer at the well walls which would control invasion.

This paper presents a radial model, based on Darcy's law to predict the drilling fluid invasion profile into a multi-layer reservoir rock saturated with a compressible fluid. Results highlight that the differential pressure, the fluid compressibility, the filter cake permeability and the rock properties are important parameters that affect significantly the invasion profile. The proposed methodology is a tool to optimize drilling fluid design to be used in the drilling of reservoir sections in both exploratory and development wells in offshore Brazil fields. The process analysis is illustrated with a series of case studies in offshore exploratory wells drilled in Brazil. The analysis highlights the importance of filtration control and of a dedicated drilling fluid designed for each specific reservoir.
Return to Basics and Proper Planning Opens the Possibility to Acid Stimulate a Difficult Chalk Formation
Authors: Van Domelen Mary , Talib Noor , Glasbergen Gerard
Published: June 2011

In the Danish Central Graben, the Lower Cretaceous reservoir contains significant in-place oil volumes. This formation historically has posed a real challenge to develop because of the extremely low permeability. The low permeability is compounded by the fact that the formation is soft, highly heterogeneous, and can have significant clay content in some areas. Although the Lower Cretaceous chalks represent a wide spread play in the central North Sea, there are no producing analogs.

Thicker Lower Cretaceous reservoir sections in the Valdemar field have been successfully proppant fracture stimulated. Acid stimulation is preferred for the thinner sections; however, early attempts at matrix acid stimulation were very disappointing. Recently, the need to re-enter a well for maintenance allowed three zones to be selectively restimulated using improved execution techniques and a more appropriate acid formulation. Production increase following restimulation of this first well was very encouraging and the lessons learned were applied to a second well; this time a newly drilled well completed in the Tyra Lower Cretaceous reservoir.

This paper summarizes the lessons learned, starting with a review of the previous acid stimulations. Wormhole testing with Lower Cretaceous core material provided important insight toward the selection of the most appropriate acid formulation. Computer modeling was used to determine the most effective perforation patterns, based upon variable formation characteristics along the long, horizontal wellbore. Treatment execution and monitoring included diagnostic injection tests and real-time calculations of acid coverage during the limited-entry perforated completions.

The results of these two wells has been very encouraging and has opened up the possibility for continued testing of acid stimulation techniques in both the Valdemar and Tyra Lower Cretaceous reservoirs.
Mechanically Induced Fracture Face Skin – Insights from Laboratory Testing and Numerical Modeling
Authors: Reinicke Andreas , Blöcher Guido , Zimmermann Günter , Huenges Ernst , Dresen Georg , Stanchits Sergei , Legarth Björn , Makurat Axel
Published: June 2011

In context of this work, a new formation damage mechanism is proposed: the mechanically induced fracture face skin (FFS). This new mechanism results from mechanical interactions between the proppants and the reservoir rock, due to the increasing stress on the rock-proppant system during production. Proppant embedment into the fracture face and proppant crushing leads to fines production and may impair the fracture performance. In order to achieve sustainable, long-term productivity from a reservoir, it is indispensable to understand the hydraulic and mechanical interactions in rock-proppant systems. Permeability measurements on sandstones with propped fractures under stress using different flow cells were performed, allowing localizing and quantifying the mechanical damage at the fracture face. The laboratory experiments identified a permeability reduction at the fracture face up to 90 %. The mechanical damage at the rock-proppant interface begins immediately with loading the rock-proppant system and for fracture closure stresses below 35 MPa; the damage is localized at the fracture face. Microstructure analysis identified quartz grain crushing, fines production and pore space blocking at the fracture face causing the observed mechanically induced FFS. At higher stresses, damage and embedment of the ceramic proppants further reduces the fracture permeability. Numerical modeling of the rock-proppant system identified highly inhomogeneous stress distributions in the granular system of grains and proppants. High tensile stress concentrations beneath the area of contact between quartz grains and proppants are observed even at small differential stress applied to the rock-proppant system. These high stress concentrations are responsible for the early onset of damage at the fracture face. Therefore, even low differential stresses, which are expected under in-situ conditions, may affect the productivity of a hydraulically fractured well.
Formation Damage Caused by Improper Mn3O4-based Filter Cake Cleanup Treatments
Authors: Al Moajil Abdullah M. , Nasr-El-Din Hisham A.
Published: June 2011

Cleanup of filter cake is a difficult task and becomes more challenging when dealing with weighting materials such as manganese tetraoxide. Mn3O4 is a strong oxidizing agent and can be used as a catalyst due to its active phase, which will result in complex interactions with most cleaning fluids.

The reaction of selected organic acids and chelating agents with Mn3O4 particles as a function of time and temperature were studied. Atomic absorption was used to measure manganese concentrations and X-ray diffraction to analyze solids remaining after the reaction.

White precipitate of manganese citrate was produced following the reaction of citric acid with Mn3O4 up to temperatures of 284°F. The amount of precipitation increased with temperature and initial chelate concentration. GLDA reacted with Mn3O4 particles completely at 190°F. However, a large amount of white precipitation produced. Similarly, a white precipitation was observed with oxalic and tartaric acids. The reaction of DTPA with Mn3O4 particles in glass reactor produced Mn(silicates) at 212 and 284°F. This study will help drilling/completion engineers to avoid using such chemicals to prevent formation damage after filter cake removal treatments.
Mitigation of Fines Migration Using a New Clay Stabilizer: A Mechanistic Study
Authors: El-Monier I. A. , Nasr-El-Din H. A.
Published: June 2011

Fines migration is a well known problem in sandstone formations, where clay particles are released when come in contact with fresh water or high pH fluids. In its nature state, each clay platelets is surrounded by an atmosphere of cations. These positive charges neutralize the negative charges of the platelets and hold the platelets in electrostatic equilibrium. Beside the electrostatic interactions between colloidal entities, dispersion forces often called the London-van der Waals forces, which are always attraction forces, exist between particles. To mitigate the migration problem, it was required to control these forces.

A new inorganic Al/Zr-based clay stabilizer was used to mitigate fines migration problem. Its effectiveness was proven experimentally in Berea sandstone cores with permeability of 65–100 md, Berea sandstone is rich in kaolinite. It showed also great effectiveness when come in contact with high pH fluids. Coreflood tests were conducted at various temperatures up to 300°F. Effluent samples were collected, and the concentrations of different cations were measured using ICP.

Experimental results showed that the stabilizer was effective in mitigating fines migration in Berea cores up to 300°F. The amount of Al/Zr retained in the core effluent was found to be a function of clay content. Various forces acting on clay particles were defined using Derjaguin and Landau, Verwey and Overbeek theory. The mechanism of stabilizing clay using the new chemical is well explained by DLVO theory. The results of this work will help production engineers to design clay stabilizer treatment used in the field.
Measurement of Acid Placement with Temperature Profiles
Authors: Tan X. , Tabatabaei M. , Zhu D. , Hill A. D.
Published: June 2011

Optimum fluid placement is crucial for a successful acid stimulation treatment, both for horizontal wells where there is a broad variation of reservoir properties along the wellbore, and for vertical wells with multiple zones and/or extensive productive intervals. Recently, distributed temperature sensing technology has enabled us to observe dynamic temperature profiles along a wellbore during and after an acid treatment. This technology allows us to monitor and evaluate treatments in real-time by capturing a sequence of temperature profiles at different times and evaluating temperature response to acid injection.

We have developed mathematical models to simulate the temperature behavior along a wellbore, horizontal or vertical, during and shortly after an acid treatment. This approach couples a wellbore model and a near-wellbore thermal model considering the effects of both mass and heat transfer between the wellbore and the formation. The models account for all significant thermal processes involved during a treatment, including heat of reaction, conduction and convection. An inversion procedure is applied to interpret the acid distribution profiles from the measured temperature profiles.

For horizontal wells, the results indicate that the distribution of stimulation fluid along a lateral and the effectiveness of diversion processes during an acid treatment can be quantified in real-time using distributed temperature measurements. The model shows that the relative injectivities into different zones can be interpreted from the temperature response measured during injection. For vertical wells, we have focused on diagnosing the volume of acid placed in each zone from the flow back temperature history. During the flow back period, the zones that have taken more acid volume will show more heating because of reaction, and will have higher temperature when entering the wellbore. This provides a mechanism to quantitatively determine the acid distribution. The methods developed from this study can help to diagnose and optimize acidizing design, and improve the efficiency of acid stimulation.
Protect and then Inject: Optimized Well Fluids Successfully Drill Depleted Reservoirs to Store Gas
Authors: Vickers Stephen , Bruce Stephen , Hutton Alistair , Nunzi Paolo
Published: June 2011

A major operator has initiated the data acquisition campaign in the Southern North Sea for a future storage facility capable of holding 5 billion m3 of gas. It is estimated this venture will double the existing gas supplies stored in the UK and represent over 5% of its annual gas demand. As North Sea gas production decreases and the UK becomes more dependent on imports, the ability to store gas has become an important part of the UK energy policy.

Drilling into depleted reservoirs for gas storage produces several major technical problems and issues that must be addressed. This field is a pressure-depleted reservoir with a differential pressure equivalent to 7.3 lb/gal between the drilling fluid's hydrostatic pressure and the reservoir pressure. This differential must be controlled to eliminate the risk of differential sticking, downhole losses, and hole collapse.

Due to the reservoir depletion, it would be impossible to backflow and clean up the near-wellbore region without a post drill-in treatment fluid to remove the fluid filter cake and water-wet all the surfaces for gas injection. To ensure project success and usable fluid designs, reservoir conditions were simulated in the laboratory and fluid parameters were altered to provide the optimum properties to minimize the future risks.

The paper discusses in full the laboratory design process, the verification of the drill-in and treatment fluids as being fit-for-purpose, and their successful application in the field. Initial well testing suggested the expected injection rates of 500 scf/min at 300 psi were exceeded, with rates of 750 scf/min at 280 psi reported.
Modeling Non-Matrix Flow and Seals Integrity in Soft Sand Reservoirs
Authors: Onaisi Atef , Ochi Jalel , Mainguy Marc , Souillard Phillipe
Published: June 2011

Most of oil reservoirs operated by Total in West African deep offshore are multi layered highly unconsolidated sands. Burial depths, below the mud line, ranges from 500 to 2500mTVD. Sea water injection is done for pressure maintenance in deviated and horizontal wells equipped with sand control. Polymers injection for EOR and PWRI are also practiced.

In theory, the very high permeability of soft sand reservoirs should allow injecting in matrix mode at high rates with small differential pressure. In reality, declining injectivity over time requires injecting in non-matrix mode, at much higher pressures than anticipated, hence the concerns about the confinement of the injection. The mechanisms of injectivity restoration by increasing the pressure in soft sands and the subsequent risks of cap rock failure have to be understood. Their incorporation in modeling tools is crucial for predicting the operating pressure range and designing the surface and wells facilities accordingly. Standard tensile fracturing models commonly applied to consolidated reservoir rocks do not seem to be adapted to soft materials which behavior is dominated by shear failure and resulting in dilation. This paper will present modeling approaches aimed at predicting the responses of soft sands and of the cap rock to produced water injection taking into account the coupling between geomechanics, flow and formation damage. Field observations are presented and confronted with model predictions.
Selective Stimulation and Water Control in High-Water-Cut Wells: Case Histories from Upper Magdalena Valley Basin in Colombia
Authors: Rodriguez E. , Duarte C. , Martinez W. , León J. , Ortega A. , Lastre M. , Milne A. , Navarro C.
Published: June 2011

A brownfield located in the southwest region of Colombia, in the Upper Magdalena Valley Basin, produces from shallow marine sandstones of the Upper Cretaceous-aged Monserrate Formation. Net pay varies from 50 to 150 ft, with porosity between 17 and 22%, and permeability of 80 to 360 mD. The wells in this field, which has been under water injection since 1997, produce with a high water-cut, which in most cases exceeds 90%.

Water injection has led to inorganic scale, organic scale, asphaltene deposition, fines migration, and the need to treat the wells using hydraulic fracturing and/or matrix acidizing techniques. Conventional matrix stimulation treatments require the use of straddle packers to ensure complete zonal coverage and frequently result in increased water production with no significant increase in oil production, making the treatments uneconomical.

To reduce the cost of and increase the success rate of matrix treatments, a Combined Diverter and Conformance Control (CDCC) fluid was introduced. This allowed the stimulation to be performed when mechanical diversion was not possible due to wellbore restrictions. The CDCC fluid is pumped in alternating stages with the acid system to divert the treating fluid and provide water conformance control.

A recent stimulation campaign, using the CDCC fluid in this field, resulted in a 30% increase in oil production while reducing the water cut by 10%. The average cost of the treatments was reduced by 27%, when compared to conventional treatments. This has led to a reassessment of the economics of the field, with the possibility of recovering an additional ~3% of the reserves in place. The plan is to treat routinely underperforming wells, irrespective of the water cut.

The ability to increase economically the oil production in this marginal field has led to a reassessment of other similar fields approaching their economic limit.
Bring Back Bentham: "Open Courts," "Terror Trials," and Public Sphere(s)
Authors: Resnik Judith
Published: June 2011

The identification of courts as open and public institutions is commonplace in national and transnational conventions. But even as those attributes are taken for granted, the privatization of adjudication is underway. This Article explores howduring the last few centuriespublic procedures came to be one of the attributes defining certain decision-making institutions as courts. The political and theoretical predicates for such practices can be found in the work of Jeremy Bentham, a major proponent of what he termed publicity, a practice he commended by detailing the architecture for various entitiesfrom the Panopticon for prisoners to the Parliament for legislators and courts for judges. Bentham argued the utility of publicity in enhancing accuracy, public education, and judicial discipline.Moving forward in time, I examine various contemporary techniques in several jurisdictions that shift the processes of adjudication toward privatization. Included are the devolving adjudication to less-public government entities such as administrative agencies; outsourcing to private providers; and reconfiguring the processes of courts to render them more oriented toward settlement.For those appreciative of the role courts play in developing and protecting human rights, these new practices are problematic because adjudication can itself be a site offering opportunities to engage in democratic practices. The odd etiquette entailed in public adjudication under democratic legal regimes imposes obligations on government and disputants to treat each otherbefore an observant and often times critical publicas equals. Public and private power can be constrained by such performative requirements. When decision making takes place in public, the application of law to fact can engender normative contestation predicated on popular input. This claim of public adjudications democratic potential and utilities is, however, not an argument that the judgments provided and the norms developed will necessarily advance a shared view of the public welfare. Hence, while eager to re-engage Bentham, I offer different claims for publicity and less optimism about its consequences.
Private Policing and Human Rights
Authors: Sklansky David A
Published: June 2011

Very little of the expanding debate over private policing has employed the language of human rights. This is notable not just because private policing is a distinctly global phenomenon, and human rights have become, as Michael Ignatieff puts it, the lingua franca of global moral thought. It is notable as well because a parallel development that seems in many ways related to the spread of private policingthe escalating importance of private military companieshas been debated as a matter of human rights.This Article asks whether discussions of private policing have been impoverished by their failure to employ the language of human rights. It begins by discussing the dramatic rise, over the past several decades, in the size and significance of private policing. It then summarizes the academic and public policy debates about that development and considers what, if anything, the language of human rights could add to those debates, and whether the addition would be welcome. One strand of the Article compares the debate over private policing with the debate over private military companies. Another strand compares private policing with private prisons, in light of the recent ruling by the Supreme Court of Israel declaring private prisons unconstitutional. The Article concludes that the benefits of introducing the language of human rights into debates about private policing are far from clearwith one exception. Human rights, particularly as codified in international treaties, do seem a promising way to get traction on a particular aspect of police privatization that has received less attention than it deserves: the way in which widespread reliance on private security firms may weaken public commitment to providing everyone with a minimally acceptable degree of protection against private violence.