bluuebunny/crossref_metadata_2025 huggingface dataset:
Mapping the Epistatic Network Underlying Murine Reproductive Fatpad Variation
Authors: Jarvis Joseph P , Cheverud James M
Published: November 2010

Genome-wide mapping analyses are now commonplace in many species and several networks of interacting loci have been reported. However, relatively few details regarding epistatic interactions and their contribution to complex trait variation in multicellular organisms are available and the identification of positional candidate loci for epistatic QTL (epiQTL) is hampered, especially in mammals, by the limited genetic resolution inherent in most study designs. Here we further investigate the genetic architecture of reproductive fatpad weight in mice using the F10 generation of the LG,SM advanced intercross (AI) line. We apply multiple mapping techniques including a single-locus model, locus-specific composite interval mapping (CIM), and tests for multiple QTL per chromosome to the 12 chromosomes known to harbor single-locus QTL (slQTL) affecting obesity in this cross. We also perform a genome-wide scan for pairwise epistasis. Using this combination of approaches we detect 199 peaks spread over all 19 autosomes, which potentially contribute to trait variation including all eight original F2 loci (Adip1-8), novel slQTL peaks on chromosomes 7 and 9, and several novel epistatic loci. Extensive epistasis is confirmed involving both slQTL confidence intervals (C.I.) as well as regions that show no significant additive or dominance effects. These results provide important new insights into mapping complex genetic architectures and the role of epistasis in complex trait variation.
Bladder Exstrophy-Epispadias-Cloacal Exstrophy Complex: A Contemporary Overview
Authors: Baradaran Nima , Gearhart John P.
Published: December 2010

Bladder exstrophy-epispadias complex (BEEC) is a spectrum of rare congenital malformations involving the urinary, genital, and musculoskeletal systems in which the bladder remains open through a lower abdominal defect with wide pubic separation. Treatment is primarily surgical and usually is performed in multiple stages. Goals of treatment include closing the bladder and abdominal defect while maintaining renal function, achieving urinary continence, maintaining sexual function, and providing cosmetically appealing external genitalia. Several long-term complications of this challenging condition in pediatric urology require a multidisciplinary treatment approach.
Core Concepts: Neonatal Glomerular Filtration Rate
Authors: Su Sharon W. , Stonestreet Barbara S.
Published: December 2010

Although the placenta is the primary organ responsible for fetal clearance and electrolyte homeostasis, fetal kidneys contribute to amniotic fluid production and fetal hemodynamics. Maternal factors can significantly influence fetal urinary output and blood pressure. Maturation of neonatal glomerular filtration rate (GFR) depends on the development of renal blood flow (RBF). After birth, a marked increase in systemic blood pressure and decrease in renal vascular resistance results in elevated RBF and consequent increases in GFR. Vasoactive factors, including renin, angiotensin II, glucocorticoids, nonsteroidal anti-inflammatory drugs, nitric oxide, prostaglandins, bradykinin, and endothelin, each play vital roles in the regulation and development of neonatal GFR. Prematurity and intrauterine growth restriction (IUGR) may affect renal endowment and place infants at risk for hypertension and accelerated loss of renal function later in life.
Hyperkalemia Complicating Propranolol Treatment of an Infantile Hemangioma
Authors: Pavlaković Helena , Kietz Silke , Lauerer Peter , Zutt Markus , Lakomek Max
Published: November 2010

Propranolol treatment was recently reported to be successful for the management of severe infantile hemangioma. Known adverse effects of propranolol treatment include transient bradycardia, hypotension, hypoglycemia, and bronchospasm (in patients with underlying spastic respiratory illnesses), which led to a general recommendation to gradually increase propranolol dosage and closely monitor patients' hemodynamics at the onset of therapy. To date, no serious or unexpected adverse effects that required specific intervention have been reported. In this report, we describe the case of a 17-week-old female preterm infant who presented with a large, ulcerated, cutaneous-subcutaneous hemangioma of the right lateral thoracic wall, which we treated successfully with propranolol. A few days into therapy, a potentially life-threatening adverse effect, severe hyperkalemia, was observed and required treatment with loop diuretics, fluids, and nebulized salbutamol to normalize her serum potassium levels. This therapy could be gradually tapered and finally discontinued only after several weeks of propranolol treatment. Our case report indicates that, at least during the initial phase of the propranolol treatment of infantile hemangioma, close monitoring of serum electrolytes, besides the monitoring of hemodynamics and blood glucose, is necessary.
Pentavalent Rotavirus Vaccine in Developing Countries: Safety and Health Care Resource Utilization
Authors: Christie Celia D. C. , Duncan Newton D. , Thame Kirk A. , Onorato Matthew T. , Smith Hyacinth D. , Malcolm Lavern G. , Itzler Robbin F. , DiNubile Mark J. , Heaton Penny M.
Published: November 2010

OBJECTIVE:

In the international, placebo-controlled, Rotavirus Efficacy and Safety Trial, the pentavalent rotavirus vaccine reduced the rate of rotavirus-attributable hospitalizations and emergency department visits by 95%. This study investigated the effect in Jamaica.

METHODS:

The vaccine effect on rates of hospitalizations and emergency department visits in Jamaica was evaluated in both modified intention-to-treat and per-protocol analyses. Rates of serious adverse events, including intussusception, also were compared between groups.

RESULTS:

A total of 1804 Jamaican infants, 6 to 12 weeks of age at entry and primarily from low/middle-income families of African heritage, received ≥1 dose. During the first year after dose 1, there were 2 and 11 hospitalizations or emergency department visits attributable to rotavirus gastroenteritis involving any serotype among 831 evaluable vaccine recipients and 809 evaluable placebo recipients, respectively (rate reduction: 82.2% [95% confidence interval: 15.1%–98.0%]). In the per-protocol analysis, all 8 G1 to G4 rotavirus-attributable events that occurred ≥2 weeks after dose 3 were in the placebo group (rate reduction: 100% [95% confidence interval: 40.9%–100%]). Of the 1802 subjects included in the safety analyses, intussusception was confirmed for 1 vaccine recipient (115 days after the third dose) and 3 placebo recipients. One vaccine recipient and 3 placebo recipients died during the follow-up period, but none of the deaths was considered to be vaccine-related.

CONCLUSIONS:

In this posthoc subgroup analysis, the vaccine reduced health care resource utilization attributable to rotavirus gastroenteritis, without increased risk of intussusception or other serious adverse events, among infants in a resource-limited country.
Developing Culturally Responsive Approaches With Southeast Asian American Families Experiencing Developmental Disabilities
Authors: Baker Dian L. , Miller Elizabeth , Dang Michelle T. , Yaangh Chiem-Seng , Hansen Robin L.
Published: December 2010

OBJECTIVE:

Southeast Asian American families are underrepresented among recipients of special education and social services for people with developmental disabilities. Our aims were to use a community-based participatory research approach to examine Hmong and Mien families' perceptions of developmental disabilities and understand barriers to and facilitators of service provision among families experiencing developmental disabilities. We describe here a case study of a successful attempt to engage marginalized and underserved communities to understand their needs to improve access and services for persons with developmental disabilities.

METHODS:

We conducted 2 focus groups with 11 key informants and 1 focus group with 10 family members of persons with developmental disabilities, as well as in-depth interviews with 3 shamans. Using a thematic analysis approach, we coded notes and transcripts to assess community members' understanding of developmental disabilities, experiences negotiating educational and health care systems, and barriers to high-quality care.

RESULTS:

A predominant theme was the perception that reliance on governmental support services is not appropriate. Common barriers identified included lack of accurate information, language difficulties, lack of trust, and limited outreach. These perceptions and barriers, combined with limited access to services, interfere with community acceptance and use of available support services. Despite these barriers, participants indicated that with education, outreach, and culturally responsive support, families would likely accept services.

CONCLUSIONS:

Community-based participatory methods are effective for eliciting root causes of health inequities in marginalized communities. Outreach to community-based organizations and an inclusive research practice identified social and cultural reasons for low service uptake and provided a pathway for the community to improve services for persons with developmental disabilities.
Narrative Coherence and the Trauma Experience: An Exploratory Mixed-Method Analysis
Authors: Freer Benjamin D. , Whitt-Woosley Adrienne , Sprang Ginny
Published: November 2010

The current study examines trauma narratives from 28 survivors of interpersonal violence. A mixed-method approach assessed coherence and explored narrative characteristics among differentially exposed groups. The quantitative analysis revealed: (1) exposure to repetitive interpersonal violence was described with greater perception of severity and emotional tone than single interpersonal violence episodes, and (2) exposure to interpersonal violence in childhood was described with greater emotional tone than exposure to interpersonal violence in adulthood. The qualitative analysis revealed: (1) traumatic events were connected to proceeding adverse experiences, (2) attempted avoidance of memories of the violence, (3) an altered view of the self, and (4) lacked recognition that the violence was abnormal. The study supports the “dose-response relationship” of trauma exposure, and the life-altering, transformative nature of trauma exposure.
Culturally Specific Treatment for Partner-Abusive Latino Men: A Qualitative Study to Identify and Implement Program Components
Authors: Welland Christauria , Ribner Neil
Published: November 2010

Research based on a demographic survey and qualitative interviews of Latino intimate partner violence perpetrators in Southern California forms the basis of a Spanish-language treatment program designed to be culturally appropriate for Latino immigrant men, and piloted for 4 years with their input. Culturally-specific topics emphasized by participants and integrated into the program are: effective parenting skills for men; gender roles; discussion of discrimination towards immigrants and women; immigration and changing gender roles; marital sexual abuse; and spirituality as related to violence prevention. Attention is given to alcohol abuse and childhood trauma. Results suggest the desirability of an empathic and culturally-sensitive approach, without diminishing responsibility. This program was designed to help clinicians refine their skills and effectiveness in working with this rapidly expanding population.
Domestic Violence and South Korean Women: The Cultural Context and Alternative Experiences
Authors: Kim Bitna , Titterington Victoria B. , Kim Yeonghee , Wells William Bill
Published: November 2010

The present research contributes to the growing body of cross-cultural research on domestic violence. This is accomplished by answering the question of how severity of intimate partner abuse varies for (1) women incarcerated for the homicides of their male partners (2) abused women who sought domestic violence shelter, short of killing their intimate assailants, and (3) a group of South Korean females outside of domestic violence shelters or prison. The article concludes with a discussion of potential policy implications of the findings as well as promising directions for future research.
Factor Analyses of Condom Attitudes, Norms, and Self-Efficacy Measures in Diverse Samples
Authors: Pratte Katherine , Whitesell Nancy , McFarlane Mary , Bull Sheana
Published: November 2010

Measurement of condom attitudes, norms, and self-efficacy is variable, reducing research generalizability. The purpose of this study was to assess reliability and construct validity of measures of condom attitudes, norms, and self-efficacy across 3,989 youth. Data were collected at computer kiosks and on the Internet. Analyses included internal consistency reliability assessments and exploratory and confirmatory factor analyses of three constructs in a 32-item a priori instrument. Reliability estimates ranged between 0.68 and 0.89, and goodness of fit indices all exceeded 0.90. Factor analysis results supported the compatibility of the items from the three subscales with their conceptual domains. Final scales include measures of positive and negative outcome expectancies related to condom use, peer and partner condom norms, self-efficacy for condom negotiation, and self-efficacy for condom use. These measures of condom attitudes, norms, and self-efficacy can be employed for assessments to improve standardization of measures and generalizability of research, particularly related to HIV prevention.
DISCRIMINATED FUNCTIONAL COMMUNICATION: A PROCEDURAL EXTENSION OF FUNCTIONAL COMMUNICATION TRAINING
Authors: Kuhn David E. , Chirighin Anna E. , Zelenka Katrina
Published: December 2010

A limitation associated with communication‐based interventions for problem behavior is the potential for requesting reinforcement at high rates. Multiple‐schedule arrangements have been demonstrated to be effective for controlling rates of responding (Hanley, Iwata, & Thompson, 2001). In the current study, we extended previous research by teaching individuals to attend to naturally occurring discriminative stimuli (e.g., caregiver behavior) instead of arbitrary stimuli (e.g., picture cards). Following successful treatment with functional communication and extinction, 2 participants were taught to request attention differentially based on whether the caregiver was engaging in a variety of “busy” (e.g., talking on the phone) or “nonbusy” (e.g., reading a magazine) activities. Following training, each participant engaged in communication primarily when caregivers were engaged in nonbusy activities.
INCREASING RESPONSE DIVERSITY IN CHILDREN WITH AUTISM
Authors: Napolitano Deborah A. , Smith Tristram , Zarcone Jennifer R. , Goodkin Karen , McAdam David B.
Published: December 2010

Repetitive and invariant behavior is a diagnostic feature of autism. We implemented a lag reinforcement schedule to increase response diversity for 6 participants with autism aged 6 to 10 years, 4 of whom also received prompting plus additional training. These procedures appeared to increase the variety of building‐block structures, demonstrating that an intervention that includes differential reinforcement can increase response diversity for children with an autism spectrum disorder.
THE EFFECTS OF CONSTANT VERSUS VARIED REINFORCERS ON PREFERENCE AND RESISTANCE TO CHANGE
Authors: Milo Jessie‐Sue , Mace F. Charles , Nevin John A.
Published: December 2010

Previous research has demonstrated that factors such as reinforcer frequency, amount, and delay have similar effects on resistance to change and preference. In the present study, 4 boys with autism made choices between a constant reinforcer (one that was the same food item every trial) and a varied food reinforcer (one that varied randomly between three possible food items). For all 4 boys, varied reinforcers were preferred over constant reinforcers, and they maintained higher response rates than constant reinforcers. In addition, when a distraction (a video clip) was introduced, responding maintained by varied reinforcers was more resistant to distraction than responding maintained by constant reinforcers. Thus, the present experiment extended the generality of the relation between preference and resistance to change to variation in reinforcer quality.
Joint Updating of Petrophysical Properties and Discrete Facies Variables From Assimilating Production Data Using the EnKF
Authors: Agbalaka Chinedu C. , Oliver Dean S.
Published: November 2010

The ensemble Kalman filter (EnKF), is a sequential data-assimilation technique that has been shown to work quite well in obtaining conditional facies models from assimilating production data. Because the problem of history matching geological facies is quite complex, most efforts at solving this problem typically assume that facies properties are constant and spatially homogeneous. In this paper, we propose a method for updating both the categorical facies variables and the spatially heterogeneous and nonuniform properties of the facies in a consistent manner within the EnKF framework. Tests of our proposed approach on two representative examples with different features of nonstationarity resulted in satisfactory history-match solutions and geologically consistent estimates of the nonuniform and heterogeneous petrophysical properties.
Sixty Days Ahead of Schedule: Reducing Drilling Risk at Valhall Using Computational Geomechanics
Authors: Kristiansen Tron Golder , Flatebø Roar Egil
Published: November 2010

The Valhall field is an overpressured, undersaturated Upper Cretaceous chalk reservoir located in the Norwegian sector of the North Sea. The reservoirs consist of weak chalk. The weak chalk results in significant reservoir compaction, exceeding 10 m in places, and corresponding seafloor subsidence, exceeding 6 m above the center of the field. Previous papers have documented the increasing drilling challenges in the shale overburden at Valhall because of the subsidence. This paper presents the computational-geomechanics technology developed and implemented to assist drilling into the highly depleted and compacted crest from the new water-injection platform at Valhall. The work focuses on handling the stress changes occurring in the overburden above a compacting reservoir and not the more traditional situation associated with depletion-induced fracture-gradient changes in the reservoir itself. The technology is based on a history-matched full-field finite-element-based geomechanics model to calculate stresses, strains, and displacements. The results are exported from the finite-element model (FEM) to a geological modeling software to perform wellbore-stability calculations using BP best practices for prediction of wellbore stability. In this environment, one can also easily use as supporting data 4D seismic from the permanent life-of-field seismic array at Valhall. By calculating the operational mud-weight window over a high risk interval in the overburden, a good correlation to historical nonproductive time (NPT) was found. The methodology is used in detailed well planning where moving the well 50 m in one direction is the difference between problem-free drilling or huge drilling challenges. The paper presents the first application of this technology on a new water injector delivered 60 days ahead of schedule with reduced costs of approximately USD 20 million and with avoidance of a potential "train wreck" that could have cost USD 60 million.
Petrophysical Analysis Method to Identify "Sweet Spots" in Tight Reservoirs: Case Study From Punta Rosada Formation in Neuquen Basin, Argentina
Authors: Naides C.
Published: December 2010

One of today challenges to increase reserves and gas production in Argentina is to develop low permeability reservoirs, with particular characteristics regarding reservoirs considered as conventional.

Therefore assessment and characterization of tight gas reservoirs should be conducted differently from conventional reservoirs, adapting data acquisition, processing and interpretation to these low permeability reservoirs.

In a tight gas field operated by Petrobras in the Neuquen basin, an adapted methodology is implemented for analysis and integration of data in order to identify the best areas of the reservoir, called "sweet spots", to assess their potential and optimize completion programs.

The field has 7 wells with data acquired from the 70's to recent days. Petrophysical analyses on rock samples are scarce and unrepresentative related to the total sand thickness of Punta Rosada Formation, and were conducted with an inappropriate methodology for this type of reservoir. The set of logs shows strong variation both in used technology and in the acquisition.

Thus in new wells it has been decided to acquire new logs and rock samples in order to characterize these tight gas reservoirs with an adapted methodology allowing the identification of the "sweet spots".

This paper shows the results obtained with this methodology that uses information from petrophysical laboratory analysis and well-logs (including conventional logs, image logs and NMR). This "tight gas" methodology is based on the integration among capillaries pressures with NMR logs and interpreted data from conventional logs. Finally, to validate this petrophysical characterization, the rock types obtained with the new methodology are compared with the results of production tests and PLT logs.
Impact of Organic Acids/Chelating Agents on the Rheological Properties of an Amidoamine-Oxide Surfactant
Authors: Li Lingling , Nasr-El-Din Hisham A. , Crews James B. , Cawiezel Kay E.
Published: November 2010

Surfactant-based acids have been used for diversion because they are less damaging to the formation. Amphoteric viscoelastic surfactant (VES) is the main type of surfactant being used today. Low viscosity is observed in the live-acid systems, whereas significantly increased viscosity is found when HCl reacts with carbonate and generates divalent salts. The surfactant/acid system can be broken after acid treatments by mixing with reservoir hydrocarbons, or by using an external or internal breaker.

Amidoamine oxide, an amphoteric surfactant, was examined in this work. The prepared surfactant-based live-acid system contained 20 wt% HCl, 4 wt% surfactant, and 1 wt% corrosion inhibitor. Different organic acids/chelating agents were added to live and spent acids. Calcium carbonate particles were used to neutralize live acids. The objective was to examine how these organic acids/chelating agents affected the rheological properties of spent-acid systems. Measurements were made at temperatures from 75 to 200°F at a shear rate of 10 sec–1 and a pressure of 300 psi. Several simple organic acids (formic, acetic, propionic, and butyric) and chelating agents [glycolic acid, lactic acid, gluconic acid, citric acid, tetrasodium ethylenediamine tetraacetic acid (EDTA), tetrasodium L-glutamic acid, N, N-diacetic acid (GLDA), and disodium L-glutamic acid, N, N-diacetic acid (HEIDA)] that are used in the field were examined.

Experimental results indicated that the addition of simple organic acids or chelating agents reduced the viscosity of spent acids significantly. This reduction in viscosity increased with the number of carbon atoms in the organic acid. The addition of organic acids reduced the temperature range in which the surfactant can be used. Chelating agents (α-hydroxy carboxylic acids and amino carboxylic acids) also tended to break the surfactant gel if enough chelant was used. On the basis of the results obtained, organic acids can be used to break surfactant gel. Transmission electron microscopy (TEM) tests were first conducted to examine how organic acids/chelating agents interfered with the formation of rod-like micelles in the surfactant-based acid. The results showed that the addition of organic acids to the spent acid generated a fewer elongated micelles and resulted in less apparent viscosity. In addition, if chelating agents or simple organic acids are used, then the concentration of the surfactant should be increased to compensate for the loss of viscosity induced by the addition of the organic acids.
New Insights Into Polymer Rheology in Porous Media
Authors: Seright R.S.. S. , Fan Tianguang , Wavrik Kathryn , de Carvalho Balaban Rosangela
Published: November 2010

This paper clarifies the rheology of xanthan and partially hydrolyzed polyacrylamide (HPAM) solutions in porous media, especially at low velocities. Previous literature reported resistance factors (effective viscosities in porous media) and an apparent shear thinning at low fluxes that were noticeably greater than what is expected on the basis of viscosity measurements. The polymer component that causes the latter behavior is shown to propagate quite slowly and generally will not penetrate deep into a formation. Particularly for HPAM solutions, this behavior can be reduced or eliminated for solutions that experience mechanical degradation or flow through a few feet of porous rock. Under practical conditions where HPAM is used for enhanced oil recovery (EOR), the degree of shear thinning is slight or nonexistent, especially compared to the level of shear thickening that occurs at high fluxes.
Two Novel Multistage Fracturing Processes for Unconventional Reservoirs: Unique Approach for Branch-Fracturing Stimulation
Authors: Stanojcic M. , Rispler K.
Published: December 2010

Shales, tight-gas reservoirs, and coal beds are the main sources of what are generally known as unconventional oil and gas reservoirs. Unconventional oil and gas are now a core business of many large, independent producers and a growing number of major operating companies. The reservoirs are becoming more complex and well designs are becoming more complicated and costly. The need to develop and commercialize new, more effective wellsite technologies that can help meet the increasing demand for energy, despite the dwindling domestic resource base, has been pursued by many operators. A number of unique technologies and methods have been developed to help operators produce unconventional oil and gas profitably. The objective of this work was to assess each existing stimulation technology and seek ways of combining the best available capabilities into a new stimulation technique capable of setting a new level of multizone-stimulation efficiency and effectiveness. The successful development and exploitation of unconventional reservoirs has relied on innovative technologies, such as horizontal drilling, multistage completions, modern multistage fracturing, and fracture mapping to pursue economic completions. Simulations demonstrate that shale reservoirs with ultralow permeability require an interconnected fracture network of moderate conductivity (branch fractures) with a relatively small spacing between fractures to obtain reasonable recovery factors. In this paper, two new methods and two existing methods for a wide variety of unconventional-reservoir applications are presented, to include: Fracturing preperforated, cemented horizontal liners, and isolating intervals with straddle packers. (The straddle-packer method has advantages that include the opportunity to fracture stimulate a large number of closely spaced, preperforated intervals in a horizontal well.)Hydrajet perforating with annular path (HPAP) fracturing with a more efficient method of providing sand-plug diversion. (A new BHA increases efficiencies of current application of this technique.)Using the HPAP method for high-rate, slickwater techniques. (Using the HPAP method for high-rate, slickwater- fracturing treatments can improve the effectiveness of unconventional-reservoir stimulation.)Fracturing using a method of mechanically shifted sleeves that use an unconventional approach to interval sequence to maximize fracture-network complexity.An overview of a newly developed hybrid rig that can extend reach and improve efficiencies for all of the above methods using both jointed and coiled tubing (CT).
The Influence of the Production Lines Pressure Drop in the Definition of the Oilfield Drainage Strategy
Authors: Bento Débora F. , Schiozer Denis J.
Published: December 2010

The success of an oil field drainage project depends on the production strategy, defined by an optimization process that maximizes the project Net Present Value (NPV). Considering the complexity of the process, the industry tends to simplify the numerical simulations used, mainly by separating behaviour analysis of the reservoir and production facilities. The pressure drop in the production facilities, for instance, is not generally considered in the selection of number and position of the wells. The main objective of this work is to verify if these simplifications have significant influence on the final result of the production strategy selection process. For this purpose, three studies have been done, with different operational conditions and fluid types. For each case, two production optimization processes of an oil field drainage project have been made, considering a simplified and a dynamic pressure drop calculation. The simplified pressure drop analysis consists in a bottom-hole pressure definition that allows the fluid to rise to the platform. In the dynamic option, it is necessary to define the production line geometry and the fluid conditions to calculate the bottom-hole pressure for each configuration, and the pressure drop is calculated dynamically, at each time step. With the result of both processes, the number and position of wells and performance of the optimized production strategies were compared. Significant differences were observed in the two cases tested, showing that the pressure drop influences the definition of the production strategy, although this influence should be minimized by operational conditions. It was also observed that the greater influence occurs on the heavy oil reservoir and that the locations are more influenced by the reservoir particularities.
A Finite-Mixture Approach for Drilling Optimization Using Formation Density Information
Authors: Li Gang , Bai Mao
Published: December 2010

Understanding formation strength and its mechanical properties has become increasingly important with continued development of horizontal/directional oil-and-gas well drilling and with more wells being drilled in locations under complicated geological conditions. Well coring is typically only carried out at certain depths of interest and is generally considered to be expensive and time consuming. In practice, sonic measurements are always used to estimate mechanical properties of formations, which are then adopted for further drilling or completion analysis. However, in many cases, sonic data may not be available while only formation density logs exist. Therefore, in this study, we first investigate correlations between density and sonic logs under different circumstances, and a best practice for estimating formation velocity based on density log is recommended for various areas.

A finite-mixture procedure considering various factors, such as porosity, clay volume, and pore pressure, is adopted to develop formation strength and mechanical properties. A new approach for drilling optimization using formation density information is developed. The new finite-mixture procedure illustrates a great improvement in describing correlations between velocity and density. As a result of an example of drilling optimization analysis, by considering the influence of GR as a lithology indicator, we can greatly improve the accuracy of our geomechanical analysis in different geological conditions.

The solution can lead to significant improvements in mechanical behavior prediction for drilling and completion, especially when only density logs exist. The same procedure could also be applied to other rock property-related logs.
Mercury Removal Process is Applied to Crude Oil of Southern Argentina
Authors: Salvá C. , Gallup D.
Published: December 2010

The presence of elemental mercury and mercury compounds has been reported in some produced hydrocarbons from southern fields in South America.

Although mercury removal from natural gas is a common industrial practice, that is not the case for crude oil. Mercury is a trace contaminant that is known to have severe associated problems in the petroleum industry, whose consequences may have impact on both environmental and facilities integrity/safety with undesirable costs.

Petrobras Argentina has worked in a mercury removal project that has been implemented with success. The process treatment is being applied to crude oil from E&P Petrobras Argentina concessions areas. As a result, a purified oil with much lower mercury concentration is achieved. Crude oil having acceptable mercury content is now commercialized in the market, with no restrictions.
Long Horizontal Gravel Pack With the Lightest Gravel Ever Used
Authors: Trujillo H. , Tengono J. A. , Hernández A. , Castaño R. , Ortiz E. , Charry W. , Anaya L. A. , Portela F. , Castillo R. , López M. , Calderón C.
Published: December 2010

Hocol Colombia operates in Ocelote field at the eastern part of Colombia, a land called as Llanos Orientales (Eastern Plains). In this field Hocol produced from Carbonera formation observing problems with formation deconsolidation. Normally, gravel packs jobs are performed on vertical wells with sustained good results.

However, new reservoir studies showed that horizontal wells with regular length extension (around 1000 ft) would be more profitable for this field. In order to get this objectives, Hocol design a horizontal wells Program to drill and test alternatives to get good completion of these wells. The first well was completed and gravel packed using conventional technologies and a 35% of pack efficiency was achieved.

The objective for the second well was to get at least 75% of packing efficiency. In a synergetic team effort, service companies proposed operator company new technologies that are used in other places but never were applied in Colombia. After simulations and technical meetings, the Operator decided to test two new technologies to try to get their operative and technical objective.

This paper presents the technical and operative fundamental used to support these changes and the results obtained with theses applications.
Laboratory Evaluation of Acid Refracturing Performance
Authors: Pournik M. , Smith B. T. , Li L. , Wang G. , Nasr-El-Din H. A.
Published: December 2010

Acid fracturing is a stimulation process in which the dissolution of the fracture faces creates conductivity after fracture closure. The resulting fracture conductivity depends highly on the amount and pattern of etching in addition to the strength of asperities. Various field acid fracturing treatments have shown sharp reduction in conductivity with production with almost no significant conductivity after some time. As a result, wells are refractured with the attempt of restoring or enhancing the conductivity of initial fracture. However, performance of acid refracturing treatments has not been studied and the conditions that result in success of refracturing operations are not understood.

A systematic experimental study was conducted to investigate the performance of acid refracturing process. Indiana limestone samples were treated with three typical field HCl systems of gelled, viscoelastic, and plain HCl. Conductivity measurement was performed on acid-etched core faces up to various levels of closure stress and then the samples were acid refractured again under the same conditions as the initial acid fracture. The re-etched fractures were once again placed under closure stress and conductivity measurement taken at different loads.

Experiments clearly show that acid refracturing performance is influenced by the acid system. Enhancement of conductivity with acid refracturing depended upon the acid system with greatest enhancement with plain HCl and even a deterioration with gelled acid system. While acid refracturing process did not result in significant increase in etched volume as compared to the initial treatment, it did usually cause greater enhancement in etching pattern.

There have been many developments in enhancing the performance of acid fractured wells. However the major reason for lack of success of refractured well is limited understanding of conditions that control success rate. In order to understand the controlling factors for success of acid refracturing process, systematic experimental work must be performed. Based on the findings of important parameters for success rate of acid refracturing, acid refracturing treatments can be better designed to always lead to enhanced productivity.
World's First Fracturing-Stimulation Application Through Selective-Injection Completion: Casabe Field
Authors: Olarte P. , Amaya R. , Cortes G. , Artola P. , Yeguez R.
Published: December 2010

This document presents a new fracturing application carried out through pre-existing selective completions in non-stimulated water injection wells from the Casabe field in Colombia. The technique was created as part of the revitalization strategy of this mature field, to improve the injection performance.

Selective water injection completions were implemented in the Casabe field in 2006 in order to address the low vertical efficiency of the injection, stemming from the high vertical heterogeneity of the formation, made of a large number of intercalated sands and shales, when using conventional, non-selective completion strings. In spite of the implementation of selective injection as mitigating measure, several reservoirs or sand layers were still not flooded by water, while these sands hold important remaining reserves of oil.

The new stimulation technique focused on the further improvement of vertical sweep efficiency by fracturing those low water admission layers through the selective injection strings already installed in the wells. A pilot application was successfully carried out, proving the technique as a highly profitable, rig-less operation, which minimizes operating costs and risks. As a result of this novel fracturing application, the injection rates in the stimulated wells increased over seven times and vertical sweep improved between 70% and 100%.

In comparison with conventional fracturing, the operating time with the new fracturing technique was reduced by 50%, resulting in cost savings approximately of 1MMUSD per well. This fracture technique has shown an 80% of success and it is intended to apply it widely in all preexisting and future injection wells completed selectively in the field.

This world's first successful application is consistent with the permanent industry needs to implement technically sound and viable secondary recovery techniques or methodologies for increasing profitably oil production, and for boosting recovery factors, in a fluctuating oil price environment.
A Study of the Impact of 4D-Seismic Data on TSVD-Based Schemes for History Matching
Authors: Dickstein F. , Goldfeld P. , Pfeiffer G. T. , Amorim E. P. , dos Santos R. W. , Gómez S. G.
Published: December 2010

We discuss a TSVD (truncated singular value decomposition) optimization scheme for history matching. We are particularly interested in studying the performance of TSVD under integration of P-wave velocity data. We compare the structure of the main singular value triplets with or without time-lapse seismics. We then analyze the impact of introducing the seismics in a synthetic two-phase model problem. We observe in our experiments a strong regularization of the inversion algorithm due to the seismics. At the same time, we obtain much better reservoir descriptions when 4D seismics is available.
3D Geomechanical Modeling for the Apiay and Suria Oil Fields Llanos Orientales Basin, Colombia: Insights on the Stability of Reservoir-Bounding Faults
Authors: Fernández-Ibáñez F. , Cardona F. , Holland M. , Araujo E. , Brudy M. , Alvarellos J. , Ordóñez Y. , Mateus D.
Published: December 2010

Understanding the spatial variation of stresses and rock mechanical properties is the key to optimize strategies for field development. In geologically complex regions, as faulted and folded domains or areas of lateral facies changes, integration of the geologic structure is crucial to better predict geomechanical attributes. This has been done in an area located in the Llanos Orientales Basin (Colombia) by means of a three-dimensional geomechanical model. The model integrates knowledge of the geological structure and regional stratigraphy, data collected in more than 40 wells, and the drilling experience acquired over 20 years. The result is a high resolution 3D model, easy to handle and to update, with a number of immediate applications that go from field exploration to harvesting and abandoning.

Seismically resolvable faults and horizons have been brought into three-dimensions to build a structural model of the Apiay- Suria region. The structural framework has been used to propagate the geomechanical attributes of a number of wells using geostatistical algorithms. As a result, we have built a 3D model comprising the magnitudes and orientations of the three principal stresses, the pore pressure regime, and rock mechanical properties as uniaxial rock strength, internal friction or Poisson's ratio.

The resulting 3D model provides a high resolution database that maps any lateral variation of the geomechanical attributes across the field and can be used to assess wellbore stability for any future well trajectory and location. The 3D numerical geomechanical model has been also used to determine the stress conditions near the main faults. The stress tensor is here combined with a failure criterion to assess the potential for fault instability. This study provides a valuable insight on the risk of losses while drilling through these faults and the possibility of seal rupture and leakage during injection and hydraulic fracturing activities.
Environmental Governance in Oil-Producing Developing Countries: The Case of Peru
Authors: Alba E. Mayorga
Published: December 2010

This paper reports the results of a survey of 27 oil-producing countries conducted by The World Bank to compare environmental and social governance against a benchmark standard representing a compendium of best practices for minimizing environmental impacts of oil and gas development.

Countries surveyed have in place a largely theoretical environmental policy and legal framework. However, the effectiveness of this framework is compromised by the lack of organized administrative structures that enable regulatory compliance. Human and financial resources needed for environmental governance are generally missing.

Most countries have adopted an EIA process. However, the emphasis appears directed toward approval of projects, rather than reflecting a life cycle management approach to environment and social issues. In general control and enforcement mechanisms after approval are rather limited.

Governments may consult, but disclose little to the public and affected stakeholders. Consultation is more about informing stakeholders about proposed projects once the operator is selected rather than involving them in project related decisions. There are barriers to disclosing project information and the social environments in which they occur, and to implementing a centralized information system.

Governments pay little to issues regarding liability and decommissioning of facilities. Efforts to involve private operators in applying internationally accepted practices to minimize impacts of industry development could be improved.

The paper describes the survey themes, the bench mark countries and derived standards and the evaluation process. It provides an overview of the results focusing in the Latin American countries and Peru, in particular.

Recommendations comprise: Undertake a gap analysis as a further refinement.Improve capacity in EIA monitoring and follow-up through training, workshops, and case studies; and use of qualified consultants.Improve consultation and outreach processes to build trust between industry, governments, and local communities through regional livelihood development programs.Support the development of regional information systems for disseminating environmental and social information relating to oil and gas projects.Support an approach for managing environmental liabilities including a regulatory and accounting framework; determination of liability costs and their assignment; and a better understanding of decommissioning procedures.
Seismic Innovation Challenges for Developing Stratigraphically Complex Mature Oil Fields: An Example From VMM, Colombia
Authors: Reyes-Harker A. , Agudelo W. M. , Guevara S. E. , Sandoval J. R.
Published: December 2010

Spatial distribution of sand bodies with the capacity of storing hydrocarbons follows complex patterns in reservoirs deposited in fluvial environments. Understanding this distribution is one of the most important factors to consider in the planning and management of any development strategy.

Usually, a vertical distribution of the sand bodies is obtained from well logs, core description, and outcrops added with sedimentation and depositional modeling using different techniques. This information is transferred to 2D and 3D stratigraphic models in correlations and stratigraphic panels. Despite of model depuration and tuning with development information, uncertainty is still very high. The acquisition of 3D multi-component seismic information was defined as the tool to reduce this uncertainty in the volumetric distribution of sand bodies and their connectivity, to build the geometry of the reflectors with the wave field P, identifying the lithology and the presence of fluids.

A pilot of this technology was designed in the Tenerife field (Middle Magdalena Valley Basin, Colombia) focused in obtaining information of the Mugrosa formation, of Oligocene age, composed basically by sandstone deposited in thin fluvial channels, primarily meandering. To obtain the planned outcome, a high density design (480,000 traces / km2) was developed to allow a sufficient relation signal/noise in the S wave. Non conventional field tests allowed the design of the parameters of charge from the energy source and the depth of the receptors. For the static solutions, multi-component "upholes" and the description of the shot point (SP) where tested to allow a geological model of the strata that could be related with the velocities of the P wave and S wave.

The innovative design for the management of the combination of seismic attributes of the S wave and P wave has shown considerable advantages in the definition of the sand bodies in fluvial environments as heterogeneous as this case. This innovation opens immense possibilities for the development of similar fields in the Middle Magdalena Valley Basin as in other regions of the world with similar deposits.