bluuebunny/crossref_metadata_2025 huggingface dataset:
Philogynous Masculinities
Authors: Groes-Green Christian
Published: December 2011

Masculinity studies in Africa have often highlighted young men’s tendencies to be dominant, violent, and selfish in relation to female peers. This article introduces the concept of “philogynous masculinities” as part of an exploration of more gender equitable tendencies among young men in secondary schools in Maputo, the capital of Mozambique. Findings from fieldwork in schools and student’s neighborhoods reveal that understanding alternative notions of manhood requires sensitivity to the contexts in which these are accentuated. While the bom pico notion, stressing men’s sexual satisfaction of women, received emphasis in the context of sex education, the ndota notion of restraint and antiviolence was activated under homely circumstances. Discussing multiple male subjectivities across contexts rather than classifying individual men allows for alternative configurations without ignoring their contradictory manifestations. The article urges masculinity studies to move beyond dichotomies between modern and traditional forms and to explore entanglements of hegemonic and alternative masculinities.
Sticking My Finger up at Evolution
Authors: Terry Gareth , Braun Virginia
Published: December 2011

Men’s interest in the contraceptive and reproductive spheres is often considered to be minimal, with management of these domains traditionally constructed as “feminine.” Despite this, some men, who have no interest in having children, choose to take a higher degree of control over their reproductive bodies, voluntarily seeking a “preemptive” vasectomy. This article reports on interview data with twelve men who had preemptive vasectomies, describing the shared meaning making (and subject positions) many of these men took up in relation to the operation. The subject positions can be identified by (1) descriptions of themselves and/or their lifestyles as “selfish,” and (2) descriptions of themselves and/or their lifestyles as “unconventional.” While these self-descriptors might be construed negatively, an indication of marginalization, the authors would argue that the men were able to put a positive spin on these features using neoliberal discourses of choice and personal responsibility. Access to such discourses might be seen as an indication of the men’s privileged rather than marginalized status, allowing them to make such a decision “easier” than it might be for many women. The authors would also suggest that having a preemptive vasectomy might be seen as a rejection of contemporary modes of involved fatherhood.
The Effect of Gang Membership on Victimization
Authors: Barnes J. C. , Boutwell Brian B. , Fox Kathleen A.
Published: December 2011

The current study represents the first attempt to examine how genetic and environmental factors work in concert to influence gang membership, victimization, and the effect of gang membership on victimization experiences. Using data drawn from the National Longitudinal Study of Adolescent Health, the present study employs behavioral genetic modeling (i.e., the ACE model and the DeFries-Fulker model) to examine these associations. The findings indicate that gang affiliation is influenced significantly by both genetic factors and environmental factors that are uniquely experienced by the individual. Controlling for heritable influences, gang membership increased the risk of victimization over time. The latter finding suggests that gang membership operates as a nonshared environmental influence on victimization.
Targeted 'Next-Generation' sequencing in anophthalmia and microphthalmia patients confirms SOX2, OTX2 and FOXE3 mutations
Authors: Lopez Jimenez Nelson , Flannick Jason , Yahyavi Mani , Li Jiang , Bardakjian Tanya , Tonkin Leath , Schneider Adele , Sherr Elliott H , Slavotinek Anne M
Published: December 2011

Background

Anophthalmia/microphthalmia (A/M) is caused by mutations in several different transcription factors, but mutations in each causative gene are relatively rare, emphasizing the need for a testing approach that screens multiple genes simultaneously. We used next-generation sequencing to screen 15 A/M patients for mutations in 9 pathogenic genes to evaluate this technology for screening in A/M.

Methods

We used a pooled sequencing design, together with custom single nucleotide polymorphism (SNP) calling software. We verified predicted sequence alterations using Sanger sequencing.

Results

We verified three mutations - c.542delC in SOX2, resulting in p.Pro181Argfs*22, p.Glu105X in OTX2 and p.Cys240X in FOXE3. We found several novel sequence alterations and SNPs that were likely to be non-pathogenic - p.Glu42Lys in CRYBA4, p.Val201Met in FOXE3 and p.Asp291Asn in VSX2. Our analysis methodology gave one false positive result comprising a mutation in PAX6 (c.1268A > T, predicting p.X423LeuextX*15) that was not verified by Sanger sequencing. We also failed to detect one 20 base pair (bp) deletion and one 3 bp duplication in SOX2.

Conclusions

Our results demonstrated the power of next-generation sequencing with pooled sample groups for the rapid screening of candidate genes for A/M as we were correctly able to identify disease-causing mutations. However, next-generation sequencing was less useful for small, intragenic deletions and duplications. We did not find mutations in 10/15 patients and conclude that there is a need for further gene discovery in A/M.
Phase II, Open-Label, Randomized, Multicenter Study Comparing the Efficacy and Safety of Olaparib, a Poly (ADP-Ribose) Polymerase Inhibitor, and Pegylated Liposomal Doxorubicin in Patients With BRCA1 or BRCA2 Mutations and Recurrent Ovarian Cancer
Authors: Kaye Stan B. , Lubinski Jan , Matulonis Ursula , Ang Joo Ern , Gourley Charlie , Karlan Beth Y. , Amnon Amit , Bell-McGuinn Katherine M. , Chen Lee-May , Friedlander Michael , Safra Tamar , Vergote Ignace , Wickens Mark , Lowe Elizabeth S. , Carmichael James , Kaufman Bella
Published: December 2011

Purpose

Olaparib (AZD2281), an orally active poly (ADP-ribose) polymerase inhibitor that induces synthetic lethality in BRCA1- or BRCA2-deficient cells, has shown promising clinical efficacy in nonrandomized phase II trials in patients with ovarian cancer with BRCA1 or BRCA2 deficiency. We assessed the comparative efficacy and safety of olaparib and pegylated liposomal doxorubicin (PLD) in this patient population.

Patients and Methods

In this multicenter, open-label, randomized, phase II study, patients with ovarian cancer that recurred within 12 months of prior platinum therapy and with confirmed germline BRCA1 or BRCA2 mutations were enrolled. Patients were assigned in a 1:1:1 ratio to olaparib 200 mg twice per day or 400 mg twice per day continuously or PLD 50 mg/m2 intravenously every 28 days. The primary efficacy end point was Response Evaluation Criteria in Solid Tumors (RECIST) –assessed progression-free survival (PFS). Secondary end points included objective response rate (ORR) and safety.

Results

Ninety-seven patients were randomly assigned. Median PFS was 6.5 months (95% CI, 5.5 to 10.1 months), 8.8 months (95% CI, 5.4 to 9.2 months), and 7.1 months (95% CI, 3.7 to 10.7 months) for the olaparib 200 mg, olaparib 400 mg, and PLD groups, respectively. There was no statistically significant difference in PFS (hazard ratio, 0.88; 95% CI, 0.51 to 1.56; P = .66) for combined olaparib doses versus PLD. RECIST-assessed ORRs were 25%, 31%, and 18% for olaparib 200 mg, olaparib 400 mg, and PLD, respectively; differences were not statistically significant. Tolerability of both treatments was as expected based on previous trials.

Conclusion

The efficacy of olaparib was consistent with previous studies. However, the efficacy of PLD was greater than expected. Olaparib 400 mg twice per day is a suitable dose to explore in further studies in this patient population.
Summary Report on the Graded Prognostic Assessment: An Accurate and Facile Diagnosis-Specific Tool to Estimate Survival for Patients With Brain Metastases
Authors: Sperduto Paul W. , Kased Norbert , Roberge David , Xu Zhiyuan , Shanley Ryan , Luo Xianghua , Sneed Penny K. , Chao Samuel T. , Weil Robert J. , Suh John , Bhatt Amit , Jensen Ashley W. , Brown Paul D. , Shih Helen A. , Kirkpatrick John , Gaspar Laurie E. , Fiveash John B. , Chiang Veronica , Knisely Jonathan P.S. , Sperduto Christina Maria , Lin Nancy , Mehta Minesh
Published: December 2011

Purpose

Our group has previously published the Graded Prognostic Assessment (GPA), a prognostic index for patients with brain metastases. Updates have been published with refinements to create diagnosis-specific Graded Prognostic Assessment indices. The purpose of this report is to present the updated diagnosis-specific GPA indices in a single, unified, user-friendly report to allow ease of access and use by treating physicians.

Methods

A multi-institutional retrospective (1985 to 2007) database of 3,940 patients with newly diagnosed brain metastases underwent univariate and multivariate analyses of prognostic factors associated with outcomes by primary site and treatment. Significant prognostic factors were used to define the diagnosis-specific GPA prognostic indices. A GPA of 4.0 correlates with the best prognosis, whereas a GPA of 0.0 corresponds with the worst prognosis.

Results

Significant prognostic factors varied by diagnosis. For lung cancer, prognostic factors were Karnofsky performance score, age, presence of extracranial metastases, and number of brain metastases, confirming the original Lung-GPA. For melanoma and renal cell cancer, prognostic factors were Karnofsky performance score and the number of brain metastases. For breast cancer, prognostic factors were tumor subtype, Karnofsky performance score, and age. For GI cancer, the only prognostic factor was the Karnofsky performance score. The median survival times by GPA score and diagnosis were determined.

Conclusion

Prognostic factors for patients with brain metastases vary by diagnosis, and for each diagnosis, a robust separation into different GPA scores was discerned, implying considerable heterogeneity in outcome, even within a single tumor type. In summary, these indices and related worksheet provide an accurate and facile diagnosis-specific tool to estimate survival, potentially select appropriate treatment, and stratify clinical trials for patients with brain metastases.
Association of Obesity With DNA Mismatch Repair Status and Clinical Outcome in Patients With Stage II or III Colon Carcinoma Participating in NCCTG and NSABP Adjuvant Chemotherapy Trials
Authors: Sinicrope Frank A. , Foster Nathan R. , Yoon Harry H. , Smyrk Thomas C. , Kim George P. , Allegra Carmen J. , Yothers Greg , Nikcevich Daniel A. , Sargent Daniel J.
Published: December 2011

Purpose

Although the importance of obesity in colon cancer risk and outcome is recognized, the association of body mass index (BMI) with DNA mismatch repair (MMR) status is unknown.

Patients and Methods

BMI (kg/m2) was determined in patients with TNM stage II or III colon carcinomas (n = 2,693) who participated in randomized trials of adjuvant chemotherapy. The association of BMI with MMR status and survival was analyzed by logistic regression and Cox models, respectively.

Results

Overall, 427 (16%) tumors showed deficient MMR (dMMR), and 630 patients (23%) were obese (BMI ≥ 30 kg/m2). Obesity was significantly associated with younger age (P = .021), distal tumor site (P = .012), and a lower rate of dMMR tumors (10% v 17%; P < .001) compared with normal weight. Obesity remained associated with lower rates of dMMR (odds ratio, 0.57; 95% CI, 0.41 to 0.79; P < .001) after adjusting for tumor site, stage, sex, and age. Among obese patients, rates of dMMR were lower in men compared with women (8% v 13%; P = .041). Obesity was associated with higher recurrence rates (P = .0034) and independently predicted worse disease-free survival (DFS; hazard ratio [HR], 1.37; 95% CI, 1.14 to 1.64; P = .0010) and overall survival (OS), whereas dMMR predicted better DFS (HR, 0.59; 95% CI, 0.47 to 0.74; P < .001) and OS. The favorable prognosis of dMMR was maintained in obese patients.

Conclusion

Colon cancers from obese patients are less likely to show dMMR, suggesting obesity-related differences in the pathogenesis of colon cancer. Although obesity was independently associated with adverse outcome, the favorable prognostic impact of dMMR was maintained among obese patients.
A Fractional Calculus for Nonlinear Energy Sink Used in Vibration Absorption System
Authors: Li Song , Fang Bo , Yang Tianzhi , Huang Wenhu
Published: December 2011

The phenomenon of energy pumping, in which vibratory energy is transferred irreversibly within a nonlinear, multi-degree-of-freedom system with the goal of reducing the transient response of the primary substructure, has recently been investigated analytically and through numerical simulations. The dynamics of single degree of freedom linear subsystem with attached nonlinear energy sink is investigated. The response of a linear oscillator attached to nonlinear energy sink with relatively small mass under external forcing in a vicinity of main resonance is studied analytically and numerically. It is possible that targeted energy could transfer from linear oscillators to the nonlinear energy sink in this system. Analytical model is verified numerically and a fairly good correspondence is observed. Fractional calculus offers a powerful tool to describe the dynamic behavior of real vibration absorption. A version of the fractional derivative models is presented and investigated in this paper for analyzing vibration absorption behavior of nonlinear energy sink. It is shown that the fractional-order system is in a stronger position than the traditional nonlinear energy sink coupled to the linear oscillator.
Innovation Networks in Logistics-Management and Competitive Advantages
Authors: Wirtz Harald
Published: December 2011

Networks have become an important organization form for creating and disseminating innovations in many sectors. Innovation networks can help to cope with the demands of increasing competition and rapidly changing markets. This view has established also in the logistics sector. The objective of this treatise is to help readers understand the management of innovation networks based on a case study that examines how the DHL Group, one of the world's largest providers of logistics services, organizes its innovative activities with its network partners. The special focus is the network management and competitive advantages for DHL resulting form the network. The network of DHL Solutions & Innovations (DSI), a business unit in which the DHL Group bundles and coordinates its innovation activities, is described and analyzed. DSI utilizes a large international network of heterogeneous partners, which is largely being controlled through focal means and which is configured dynamically. Functions selection, allocation, regulation and evaluation are stringently organized within this innovation network and are highly formalized. The advantages of the chosen organizational format for the network are explained on the basis of the resource oriented approaches and the transaction cost theory.
A Simplified Model for Analysis of End-plate Connections Subjected to Fire
Authors: Huang Zhaohui
Published: December 2011

In this paper a robust 2-noded connection element has been presented for modelling the bolted end-plate connections between steel beam and column at elevated temperatures. The connection element allows the element nodes to be placed at the reference plane with offset and the non-uniform temperature distributions within the connection. In this model the connection failure due to bending, axial tension, compression and vertical shear are considered. The influence of the axial tensile force of the connected beam on the connection is also taken into account. This model has the advantages of both the previous simple and component-based models. A series of numerical studies was carried on a 2D steel frame under ISO834 and Natural fires. The results indicated that the deflections of beams are significantly affected by using different types of the connections. However, the axial forces of the connected beam are less significantly affected by different types of the connections. Another finding is that the axial tensile force in the beams generated due to catenary action is relative small compared to the forces caused by the thermal shrinkage of the beam during cooling phase of the real fire.
Experimental and Numerical Investigations of Steel and Concrete Composite Floors Subjected to ISO Fire Condition
Authors: Zhao B. , Roosefid M.
Published: December 2011

The very positive membrane action of steel and concrete composite floor systems (concrete slabs connected to steel beams by means of headed studs) has been clearly demonstrated through various Cardington real fire tests. However, little evidence is established for fire performance of such structural system exposed to ISO fire condition, the lack of which still constitutes an obstacle for certain national authorities to accept totally the application of the design concept derived from above real fire tests, in particular for long duration ISO fire.

On the basis of the above situation and in order to enlarge the application of the design concept based on membrane action to all types of fire, CTICM, within the scope of two different research projects FRACOF and COSSFIRE, performed successively two full scale ISO fire tests, both of which lasted for more than 120 minutes, with two different steel and concrete composite floor systems designed according to Eurocode. The observed fire performance of these floor systems during the tests was extremely satisfactory and revealed a solid robustness of such type of structure systems in fire situation. Considering the fact that the fire test of FRACOF project has been already presented in detail during SiF'08 and Eurosteel2008 conferences, this paper is focused especially on the comparison of above two tests with regard to structural configuration, loading condition, structural behaviour and failure modes.

In addition, these tests have been subjected to a specific numerical investigation with help of a 3D hybrid structural FE model. It is illustrated through this numerical investigation that the actual advanced modelling technique is accurate enough to reproduce precisely the fire behaviour of complex structural systems and may be applied to fire safety engineering with high level of confidence.
Integrated Optimization of Procurement, Processing, and Trade of Commodities
Authors: Devalkar Sripad K. , Anupindi Ravi , Sinha Amitabh
Published: December 2011

We consider the integrated optimization problem of procurement, processing, and trade of commodities in a multiperiod setting. Motivated by the operations of a prominent commodity processing firm, we model a firm that procures an input commodity and has processing capacity to convert the input into a processed commodity. The processed commodity is sold using forward contracts, while the input itself can be traded at the end of the horizon. We solve this problem optimally and derive closed-form expressions for the marginal value of input and output inventory. We find that the optimal procurement and processing decisions are governed by price-dependent inventory thresholds. We use commodity markets data for the soybean complex to conduct numerical studies and find that approximating the joint price processes of multiple output commodities using a single, composite output product and using the approximate price process to determine procurement and processing decisions is near optimal. Compared to a myopic spread-option-based heuristic, the optimization-based dynamic programming policy provides significant benefits under conditions of tight processing capacities and high price volatilities. Finally, we propose an approximation procedure to compute heuristic policies and an upper bound to compare the heuristic against, when commodity prices follow multifactor processes.
Shadow-Routing Based Control of Flexible Multiserver Pools in Overload
Authors: Stolyar Alexander L. , Tezcan Tolga
Published: December 2011

We consider a general parallel server system model with multiple customer classes and several flexible multiserver pools, in the many-server asymptotic regime where the input rates and server pool sizes are scaled up linearly to infinity. Service of a customer brings a constant reward, which depends on its class. The objective is to maximize the long-run reward rate. Our primary focus is on overloaded systems. Unlike in the case when the system is not overloaded, where the main decision is how to allocate resources to incoming customers, in this case it is also crucial to determine which customers will be admitted to the system. We propose a real-time, parsimonious, robust routing policy, SHADOW-RM, which does not require the knowledge of customer input rates and does not solve any optimization problem explicitly, and we prove its asymptotic optimality. Then, by combining SHADOW-RM with another policy, SHADOW-LB, proposed in our previous work for systems that are not overloaded, we suggest policy SHADOW-TANDEM, which automatically and seamlessly detects overload and reduces to one of the schemes, SHADOW-RM or SHADOW-LB, accordingly. Extensive simulations demonstrate a remarkably good performance of proposed policies.
Efficient Simulation of Value at Risk with Heavy-Tailed Risk Factors
Authors: Fuh Cheng-Der , Hu Inchi , Hsu Ya-Hui , Wang Ren-Her
Published: December 2011

Simulation of small probabilities has important applications in many disciplines. The probabilities considered in value-at-risk (VaR) are moderately small. However, the variance reduction techniques developed in the literature for VaR computation are based on large-deviations methods, which are good for very small probabilities. Modeling heavy-tailed risk factors using multivariate t distributions, we develop a new method for VaR computation. We show that the proposed method minimizes the variance of the importance-sampling estimator exactly, whereas previous methods produce approximations to the exact solution. Thus, the proposed method consistently outperforms existing methods derived from large deviations theory under various settings. The results are confirmed by a simulation study.
From the Editor: Reflections on the Last Six Years
Authors: Simchi-Levi David
Published: December 2011

David Simchi-Levi, Operations Research editor-in-chief, reflects on the last six years.
I-SAVE Study: Impact of Sedation, Analgesia, and Delirium Protocols Evaluated in the Intensive Care Unit: An Economic Evaluation
Authors: Awissi Don-Kelena , Bégin Cindy , Moisan Julie , Lachaine Jean , Skrobik Yoanna
Published: December 2011

BACKGROUND:

Intensive care units (ICUs) account for considerable health care costs. Adequate pain and sedation management is important to clinical care.

OBJECTIVE:

To determine whether implementing a protocol for management of analgesia, sedation, and delirium in the ICU would save costs.

METHODS:

With data from the I-SAVE (Impact of Sedation, Analgesia and Delirium Protocols Evaluated in the Intensive Care Unit: an Economic Evaluation) study, a prospective pre- and postprotocol design was used. Between the 2 periods, protocols for systematic management of sedation, analgesia, and delirium were implemented. Cost-effectiveness was calculated by associating the variation of cost and effectiveness measures (proportion of patients within targeted pain, sedation, and delirium goals). Total costs (in 2004 Canadian dollars), by patient, consisted of the sum of sedation, analgesia, and delirium drug acquisition costs during the ICU stay and the cost of the ICU stay.

RESULTS:

A total of 1214 patients, 604 in the preprotocol group and 610 in the postprotocol group, were included. The mean (SD) ICU length of stay and the duration of mechanical ventilation were shorter among patients of the postprotocol group compared with those of the preprotocol group (5.43 [6.43] and 6.39 [8.05] days, respectively; p = 0.004 and 5.95 [6.80] and 7.27 [9.09] days, respectively; p < 0.009). The incidence of delirium remained the same. The proportion of patients with Richmond Agitation and Sedation (RASS) scores between −1 and +1 increased from 57.0% to 66.2% (p = 0.001), whereas the proportion of patients with a numeric rating scale (NRS) score of 1 or less increased from 56.3% to 66.6% (p < 0.001). The mean total cost of ICU hospitalization decreased from $6212.64 (7846.86) in the preprotocol group to $5279.90 (6263.91) in the postprotocol group (p = 0.022). The cost analyses for pain and agitation management improved; the proportion of patients with RASS scores between −1 and +1 or NRS scores of 1 or less increased significantly in the postprotocol group while costing, on average, $932.74 less per hospitalization.

CONCLUSIONS:

Establishing protocols for patient-driven management of sedation, analgesia, and delirium is a cost-effective practice and allows savings of nearly $1000 per hospitalization.
Avoiding Losses in Depleted and Weak Zones by Constantly Strengthening Wellbores
Authors: van Oort E. , Friedheim J. , Pierce T. , Lee J.
Published: December 2011

Drilling depleted or weak zones has always been a challenge, but with the aging of fields and the desire to drill to deeper in-field plays, the situation is becoming more exacerbated. The typical problems associated with drilling these types of intervals are lost circulation, stuck pipe, and wellbore instability, resulting in significant and expensive nonproductive time (NPT) and costly remediation operations. Conventional lost-circulation remedies (e.g., pumping lost-circulation pills and squeezing) have given way to popular wellbore-strengthening solutions. Our approach to strengthening, based on beneficial manipulation of fracture- propagation pressure and continuous application of specialized wellbore-strengthening additives, has had tremendous success in reducing downhole mud losses by more than 80% in Gulf of Mexico (GOM) deepwater operations and dropping the cost of these incidents out of the top 10 contributors to NPT.

This paper focuses on the various theories and approaches to wellbore strengthening and what the available field and literature data actually support. Building upon this, the approach of gaining wellbore fortification through fracture-propagation-resistance (FPR) enhancement is introduced, for which experimental results, field data, and case histories are shared. Central to our application of FPR to drill-challenging deepwater production wells is the notion of providing continuous wellbore protection through a novel and unique solids-recovery and reintroduction method that allows for drilling with high concentrations of wellbore-strengthening materials (WSMs) in the drilling fluid.
Limitations of Current Method-of-Characteristics (MOC) Methods Using Shock-Jump Approximations To Predict MMPs for Complex Gas/Oil Displacements
Authors: Ahmadi Kaveh , Johns Russell T. , Mogensen Kristian , Noman Rashed
Published: December 2011

An accurate minimum miscibility pressure (MMP) is one of the key factors in miscible-gasflood design. There is a variety of experimental and analytical methods to determine the MMP, but the most-reliable methods are slimtube experiments, 1D slimtube simulations, mixing-cell models, and the fast key-tie-line approach using the method of characteristics (MOC). Direct comparisons of all these methods generally agree well, but there are cases in which they do not. No explanation has yet been given for these anomalies, although the MMP is critically important to recovery.

The focus of this paper is to explain when current MOC results assuming that shocks exist from one key tie line to the next may not be reliable, and how to identify when this is the case. We demonstrate, using fluid characterizations from Middle East oils, that the MMPs using this MOC method can be more than 6,500 psia greater than those calculated using a recently developed mixing-cell method. The observed differences in the MMP increase substantially as the API gravity of the oil decreases, likely the result of the onset of L1-L2-V behavior. We show that the key tie lines determined using this MOC method do not control miscibility for such cases. We explain the reasons for these differences using simplified pseudoternary models and show how to determine when an error exists. We also offer a way to correct the MMP predictions using the MOC for these complex gas/oil displacements without solving for the complete compositional path.
Waxy-Crude Production Management in a Deepwater Subsea Environment
Authors: Suppiah Sitham , Ahmad Afidah , Alderson Christopher , Akbarzadeh Kamran , Gao Jinglin , Shorthouse James , Khan Ifadat Ali , Forde Chris , Jamaluddin Abul
Published: December 2011

Systematic experimental and modeling approaches to designing a safe operating strategy for a 5-km deepwater-subsea-flowline case study are presented to address unplanned shutdown and restart events for waxy-crude production. The measurements confirmed that the fluid behaves like Bingham plastic when it is allowed to become gel at the seabed temperature of 4°C. The cool-down period was modeled using the transient simulator validated by measurements and was predicted to take 21 hours. The restart pressure was then modeled for both stock-tank and at-line pressure conditions. These restart pressure requirements were found to be 2,500 and 2,100 psi, respectively, for stock-tank and at-line pressure conditions. Also, the use of pour-point depressants demonstrated that the fluid would not form gel at the seabed temperature of 4°C. However, the current shut-in wellhead pressure of 2,500 psi is deemed adequate to restart the lines in the event of unplanned shutdown without the use of chemicals. The presence of a subsea pig-launching pump provides a safety factor for restart in case the line pressure is released to atmospheric conditions. Hence, the operating strategy does not require injection of pour-point depressants at the current state. However, in future when the shut-in wellhead pressure falls below 2,500 psi, the operating strategy is expected to be modified accordingly.
Predicting Effective Permeability to Oil in Sandstone and Carbonate Reservoirs From Well-Logging Data
Authors: Anand V.. , Freedman R.. , Crary S.. , Minh C.C.. C. , Terry R.L.. L.
Published: December 2011

This paper discusses a new method for predicting continuous logs of effective permeability to oil in sandstone and carbonate formations from well-logging data. This important problem in formation evaluation has remained previously unsolved because the conventional approach used to predict reservoir properties from well-log data relies on simple empirical equations and idealized models of reservoir rocks. The use of such equations and models to predict a complex reservoir property (e.g., effective permeability) can result in an inaccurate representation of the formation.

This paper shows that accurate values of effective permeability to oil can be predicted using model-independent mapping functions constructed from Gaussian radial basis functions (RBFs), which can be derived from a laboratory database of measurements on partially saturated core samples. The mapping functions replace the empirical equations used in the conventional approach and are model-independent representations of the database measurements. Once the mapping functions are constructed from the database, there are no adjustable parameters.

In this study, mapping functions for sandstones and carbonates were derived from a worldwide database of laboratory measurements made on 79 sandstone and 25 carbonate core samples. The laboratory measurements available on each sample included irreducible water saturation, effective permeability to oil, porosity, and nuclear-magnetic-resonance (NMR) T2 distributions. The mapping functions can be used to predict effective permeability to oil of reservoirs at irreducible water saturation from input measurements of porosity, T2 distribution, irreducible water saturation, and knowledge of rock lithology (e.g., sandstone or carbonate).

The methodology for deriving the mapping functions is explained in detail. The mapping functions are applied to the database itself to show the accuracy of the effective-permeability predictions on core samples. The method is also applied to log data from both sandstone and carbonate formations in three wells from different parts of the world. The predicted effective permeabilities to oil are shown to be consistent with oil mobilities measured in the formations by fluid-sampling tools.
Which Reservoirs in China Are Best for Underbalanced Drilling?
Authors: Yao Yanhua , Xie Gangping , Nas S.W.. W. , Boutalbi S.. , Du Heli
Published: December 2011

As the underbalanced-drilling (UBD) technique develops, the benefits for eliminating formation damage and improving productivity have been well received by Chinese national oil companies. Potential candidates for UBD reservoirs are tight sandstone and volcanic rock, as well as other low-permeability hard rocks. Not all candidates are ultimately suitable. Experience in China suggests that inappropriate application of underbalanced reservoir drilling may have an adverse effect on protecting reservoirs, which in turn increases drilling risks. To achieve successful application of the technique, it is essential first to fully evaluate the suitability of the reservoir for UBD. Furthermore, it has been observed that there is a lack of research when it comes to evaluation of reservoir suitability with respect to UBD opportunities in China. Most current basin studies in China focus on geographic distributions and reservoir lithology characterizations rather than geomechanical properties.

This paper addresses these gaps by presenting the result of a China UBD basins study. We have applied our reservoir-screening process to reservoirs in 382 oil and gas fields and 17 onshore basins of China to determine whether or not these reservoirs are practical for UBD. Candidacy is determined by evaluating a number of formation-damage mechanisms and related operational risks within the reservoir-screening process. The research then identifies formation-damage mechanisms of the UBD reservoir candidates and also presents a ranking from high-potential to low-potential reservoirs for the suitability of UBD, and establishes the highest production potential by application of the UBD technique.

Also, the objective of the research is to evaluate and rank the suitability of reservoirs for exploitation by UBD compared with conventional drilling and completion processes. Proper identification of UBD opportunities will minimize drilling risks for Chinese national oil companies.
Interpretation of Immiscible WAG Repeat Pressure-Falloff Tests
Authors: Stenger B.A.. A. , Al-Kendi S.A.. A. , Al-Ameri A.F.. F. , Al-Katheeri A.B.. B.
Published: December 2011

This paper reviewed the interpretation of repeat pressure-falloff (PFO) tests acquired in two vertical pattern injectors operating in a carbonate reservoir undergoing full-field development. Enhanced vertical-sweep conformance through phase mobility control in the presence of strong reservoir heterogeneity was the major expected benefit from an immiscible water-alternating-gas (WAG) displacement mechanism.

PFO tests were carried out during the monophasic injection phase to determine well injectivity and reservoir properties, and were subsequently acquired at the end of each 3-month injection cycle. Analytical falloff-test interpretation relied on the use of the two zone radial composite model. Multiple falloff-test interpretations indicated that the two pattern vertical injectors behaved differently even though both had been fractured. The difference in behavior was linked to different perforated intervals and reservoir properties. Gas- and water-injection rates were showing differences between both pattern injectors as a consequence. Injected gas banks had a small inner radius and were almost undetectable at the end of the subsequent water cycle. Changes in the pressure-derivative slope at the end of the subsequent water-injection cycle indicated most likely the creation of an effective mixing zone of injected gas and water in the reservoir.

Numerical finite-volume simulation was required to account for potential injected-fluid segregation and the heterogeneous multilayered nature of the reservoir. Repeat saturation logs acquired in observation wells monitored the saturation distribution away from the injection wells. Fluid saturations derived from the simulation model were showing a good agreement with the analytical results in general, although the need to account for gas trapping was confirmed. Eight planned development WAG injectors were repositioned as a consequence of WAG 1 and WAG 2 pattern performance.
Laboratory Investigation of the Impact of Injection-Water Salinity and Ionic Content on Oil Recovery From Carbonate Reservoirs
Authors: Yousef Ali A. , Al-Saleh Salah , Al-Kaabi Abdulaziz , Al-Jawfi Mohammed
Published: December 2011

The impact of brine salinity and ion composition on oil recovery has been an area of research in recent years. Evidence from laboratory studies, supported by some field tests targeting mainly sandstones, has distinctly shown that injecting low-salinity water has a significant impact on oil recovery. Although the potential for carbonates has not been thoroughly investigated, some reported studies have excluded carbonates from this effect. The main objective of this paper is to investigate the potential of increased oil recovery by altering the salinity and ionic composition of the injection water for carbonate reservoirs, define the recovery mechanisms, and eventually transform the emerged trend to full-fledged reservoir technology.

This paper presents the results of different laboratory studies to investigate the impact of salinity and ionic composition on oil/brine/rock interactions and draws conclusions on potential recovery mechanisms. Also, it provides a laboratory coreflooding study conducted using composite rock samples from a carbonate reservoir to investigate the impact of salinity and ionic composition on oil recovery. The experimental parameters and procedures were well designed to reflect the reservoir conditions and current field injection practices, including reservoir pressure, reservoir temperature, and salinity and ionic content of initial formation water and current types of injected water.

The experimental results revealed that substantial tertiary oil recovery beyond conventional waterflooding can be achieved by altering the salinity and ionic content of field injected water. The new emerged trend is distinct from what has been addressed in previous reported studies on topics of low-salinity waterflooding for sandstones or seawater injection into high-temperature chalk reservoirs. On the subject of recovery mechanisms, the results showed that altering the salinity and ionic composition of the injected water has a significant impact on the wettability of the rock surface. Also, nuclear-magnetic-resonance (NMR) measurements indicated that dilution of seawater can cause a significant alteration in the surface relaxation of the carbonate rock and also can enhance connectivity among pore systems because of rock dissolution. The results, observations, and interpretations addressed in this study provided compelling evidence to suggest that the key mechanism for the emerged trend is wettability alteration.
Development of Simple-To-Use Predictive Tool for Rapid Prediction of n-Alkanes Surface Tension
Authors: Bahadori Alireza
Published: December 2011

One of the most striking demonstrations of intermolecular forces is the tension at the surface of liquid n-alkanes. The prediction of surface tension is important in the design of distillation towers, extraction units, and tower internals such as bubble caps and trays because it has a considerable influence on the transfer of mass and energy across interfaces. Surface-tension data are needed wherever foaming emulsification, droplet formation, or wetting are involved. They are also required in a number of equations for two-phase-flow calculations and for determining the flow regime. Petroleum engineers are especially interested in the surface tension in the extraction of crude oil where adding surfactants to modify the interfacial properties between crude oil and the geological reservoir can improve production and increase oil yields. In this work, a simple predictive tool using Arrhenius-type asymptotic exponential function, the Vandermonde matrix, and Matlab (Matlab 2008) technical computing language is developed for the estimation of surface tension of paraffin hydrocarbons as a function of molecular weight and temperature. The surface tension is calculated for temperatures in the range of 250 to 440 K and paraffin hydrocarbon molecular weights between 30 and 250. Estimations are found to be in excellent agreement with the reliable data in the literature, with average absolute deviation being less than 2%.
Safety-Management Programs and Standardized Application Equipment Minimize Risks of Nonconventional Chemical Usage
Authors: Horaska D.D.. D. , San Juan C.M.. M. , Bonnivier B.M.. M. , Dickinson A.L.. L. , Conaway J.L.. L.
Published: December 2011

Acrolein (2-propenal) is a highly effective microbiocide and sulfide scavenger that has been commercially available since 1960 and has been used widely in the oil- and gas-production industry. Acrolein is a liquid product supplied in and applied from specialized containers, eliminating potential releases from transfers between tanks. The acrolein containers are built to comply with international transportation regulations. This paper will cover the development of a safety-management program and standardization of application equipment that allow the usage of acrolein for applications with a risk comparable to, or in some cases lower than, that for conventional chemical products.

Standardized operating procedures, closed-system application equipment [verified by industrial hygiene (IH) monitoring], and redundant safety devices are built into the system to prevent chemical exposures or misapplications. Applications are performed by trained and certified personnel who have completed a specific competency evaluation under field conditions. A detailed and customized safety-management program is completed and implemented for each application with extensive client participation.

This paper will cover the core of the safety-management program, which focuses on developing site-specific elements, including process safety information, process hazard analysis, operating procedures, employee and contractor training, applicator competency and field evaluation, prestartup safety reviews, management of change, and emergency planning and response procedures. A safety audit program is also implemented to ensure that the completed safety management program complies with each element. Audits are conducted at the actual location during the course of the chemical application.

A strong safety-management program and standardized application system have been shown to reduce personnel and environmental risks by lowering the potential for misapplications or equipment failures. These systems have allowed successful treatment programs on numerous global production assets. To validate this, a series of case histories will be presented that highlight the best practices that enable the safe application of acrolein.
Managed Pressure Drilling Enables Drilling Beyond the Conventional Limit on an HP/HT Deepwater Well in the Mediterranean Sea
Authors: Kernche F. , Hannegan D. , Peña C. , Arnone M.
Published: December 2011

This paper describes the successful application of Managed Pressure Drilling on a deep exploration well drilled offshore Egypt in the Nile Delta. Building upon successful experience utilizing MPD on a HPHT jack-up well, the Operator transferred the experience across to a deepwater exploration project. This represented the first known use of MPD on a floating rig in this water depth and HPHT environment. Water depth was 1100 m, and the well was drilled to over 6000 m with BHP of 17,000 psi.

Extensive engineering, training and development of procedures were carried out prior to spud. MPD was utilized to drill four hole sections. Specific techniques were developed to handle floating drilling operations. The resulting benefits associated with MPD led to improvements in drilling performance, and eliminated many of the traditional problems faced on other HPHT wells in the area. MPD has now become an integral part of the well operating philosophy and has established new standards for drilling wells of this type.

The well was a rank wildcat with considerable pore pressure unknowns, coupled with narrow pore-fracture drilling window characteristic of HPHT conditions in the Nile Delta. MPD was able to minimize the problems faced on the well by enabling various techniques to be utilized. These techniques included the use of pressure build up analysis to quantify formation pressures, the application of dynamic flow checks, dynamic formation strength limits, and the application of constant bottom hole pressure during dynamic and static drilling fluid circulation conditions. The planning, development and execution phases of the MPD project are detailed in this technical paper.
Well Control When Drilling With a Partly-Evacuated Marine Drilling Riser
Authors: Falk K. , Fossli B. , Lagerberg C. , Handal A. , Sangesland S.
Published: December 2011

The Low Riser Return System (LRRS) is a method used for managing wellbore pressure during offshore drilling operations by adjusting the mud level in the marine riser by returning mud and cuttings to surface via a subsea pump in a separate conduit. It is a single mud gradient, open MPD system particularly designed for subsea drilling.

The LRRS can be used in two application modes. The first has a full riser during static conditions using conventional mud weights and the capability to lower the fluid level to compensate for the ECD effect during circulation and drilling as needed. With this technique, conventional well control procedures are used. The second technique involves using higher than conventional mud weights and lower fluid levels for both static and dynamic (circulating) operations. With this technique, modified well control procedures must be used. Both of these methods improve safety margins, allow for better pressure control, and increase efficiency for most well operations.

This paper focuses on the well control issues of drilling with a partially evacuated marine drilling riser. Two cases using data from deepwater US GoM wells illustrate how the LRRS gradient fits well inside the drilling window. Kick margins and kick detection are improved compared to conventional drilling operations, and riser margin can be achieved even for relatively deep water, which allows for safer disconnections. Improved cementing by compensating for density and ECD effects is another important result of applying this system.

We conclude that this technology can greatly improve safety in drilling of deepwater exploration and production wells as well as for infill drilling in depleted fields; enabling safe access to more reserves and improving recovery.
Offshore Underbalanced Drilling With a Closed-Loop Circulating System
Authors: Gough G. , Talbot S. , Moos H.
Published: December 2011

This paper reviews an offshore underbalanced drilling project in the Danish sector of the North Sea, undertaken during the summerof 2010. Two oil wells were drilled from a jack-up drilling rig, with produced oil and gas transferred to the accompanying production platform. A closed-loop circulating system was employed, to mitigate against the potential for release of gas vapours, completely bypassing the rig’s pits and shakers. Crude oil was initially selected as the drilling fluid for the reservoir section to reduce the baseline coefficient of friction and minimise the potential for emulsions. A bespoke disc-stack centrifuge was utilised to control the composition of drilling fluid injected into the standpipe by removing fine chalk solids and separating the oil from any produced water.

Underbalanced drilling was identified as an enabling technology to combat conventional drilling challenges due to variations in pressure profile along lengthy horizontal sections.