bluuebunny/crossref_metadata_2025_split huggingface dataset:
Predicting the Onset of Condensate Accumulation Near the Wellbore in a Gas Condensate Reservoir
Authors: Krukrubo G. J. , Gringarten A. C. 
Published: June 2009

Abstract
A gas condensate reservoir usually displays retrograde behavior when the bottomhole pressure falls below the fluid dew point pressure during production. A two-phase mixture of gas and liquid condensate forms and creates regions of different mobilities in the reservoir. These yield a fluid induced composite behavior on well test data.
Reservoir permeability, relative permeability curves, critical condensate saturation and production rate history are some of the factors which determine when the condensate starts to accumulate and when it becomes mobile. The conditions when the condensate bank becomes visible as a composite behavior on the build up derivative response are, however, much less understood. These are addressed in the present paper.
Compositional simulations of simple drawdown-build up sequences were conducted for various drawdown durations, critical condensate saturations, reservoir absolute permeabilities, oil and gas end point relative permeabilities and gas miscibility. Simulated drawdown and build up well test derivative responses were then compared and analyzed.
It was found that, whereas the change in gas mobility is reflected in the drawdown pressure derivative response as soon the pressure falls below the dew point pressure, it is delayed significantly in the build up derivative and only appears when the ratio of the mobility at the start of the build up to that at the end of the drawdown reaches a critical value. This critical value varies little with the parameters investigated in this study (1.7 to 2.1).
The relationship between the time when the mobility change first appear in the build up derivative and the drawdown rate can be represented in all cases investigated by power equations which can then be used to predict when the condensate bank might be seen on the build up derivative for different rates of production and for different reservoir parameters.
Real Options Analysis in Petroleum Exploration and Production: A New Paradigm in Investment Analysis
Authors: Jafarizadeh B. , Bratvold R. B. 
Published: June 2009

Abstract
More than three decades have passed since Stewart Myers coined the term "real options" and introduced this new paradigm into investment science. In the following years a number of publications in both the finance and decision analysis literature hailed the benefits and power of Real Options for corporate investment decisions. In 2001 Copeland stated that "In ten years, real options will replace NPV (Net Present Value) as the central paradigm for investment decisions." Now, eight years hence, the dominating valuation paradigm in the exploration and production industry still seems to be the classical NPV approach. Why?
In the time period following the initial applications of real option valuation to oil & gas investments, a number of approaches were proposed for calculating the value of an uncertain investment. Unfortunately, the assumptions underlying these various approaches and the conditions that are appropriate for their application are often not spelled out. Where they are spelled out or can be inferred, they differ widely from approach to approach and are even contradictory. Furthermore, the difficulties in implementing these approaches are rarely discussed and the pros and cons of alternative approaches are not explained.
Here we will attempt to help remedy this situation by comparing different real option approaches using a relevant oil & gas investment case. The paper concludes with observations about the relative strengths and weaknesses of the proposed approaches, and offers specific recommendations on which ones to use in what circumstances.
Surface Control System Design for Remote Wireless Operations of Intelligent Well Completion System: Case Study
Authors: Ajayi Arashi , Oluwatosin Adedeji , Fasasi Toyin , Giuliani Corrado , Smith Robert , Erumwunse Courage , Cervini Fabio 
Published: June 2009

Abstract
Application of intelligent well technology varies across different locations. In remote areas, the technology has the benefit of providing access to exploiting hydrocarbon assets in hard to reach location. In order to fully utilize the benefit of intelligent well completion for remote control, there must be adequate power and communication infrastructure. These infrastructures are often major constraints in such locations.
This paper describes a case study for the design and implementation of a surface control system and supervisory application of a 3-zone intelligent well completion. The well of interest is located in a remote area of the Niger Delta in Nigeria with limited infrastructure. The design utilizes a wireless system in controlling and optimizing the hydraulically operated downhole interval control valves (ICV) installed in the well.
The surface control system for the 3-zone intelligent well system is an automated, low power surface hydraulic system designed for single well with integrated permanent downhole gauge data acquisition capability. The system is remotely monitored and operated by means of a field management supervisory application located in a controlled environment away from the well location. The system was customized to accommodate power and communication infrastructure constraints available in the field. The system is integrated with a wireless communication system that provides direct control of the installed downhole components. The supervisory application was designed to handle future wells that might be drilled in the field. It serves as a single point of control for all intelligent wells proposed for the field.
The surface hydraulic system and associated components is located on the well platform. The system is protected by a customized external enclosure. The system is powered by a specialized thermoelectric generation unit located in a protective enclosure. The power generation system consists of a battery package that provides current peak / inrush at motor start up and designed to provide 7 days back-up power for the entire system.
The entire system was tested during the system integration test (SIT) to establish system specification before the actual field deployment.
This paper describes the challenges with the design and implementation of low power hydraulic system and methodology for the integration of hydraulically controlled system with wireless technology. The information presented by the authors can be used to design similar systems to develop assets in hard to reach locations.
Effective Stress Coefficient and Biot's Coefficient of Chalk from the Valhall Field, North Sea
Authors: Alam Mohammad Monzurul , Christensen Helle Foged , Fabricius Ida Lykke 
Published: June 2009

Abstract
Deformation of a hydrocarbon reservoir can ideally be predicted by estimating the effective stress acting on it. The effective stress is the difference between the total stress and a fraction (effective stress coefficient) of pore pressure. The effective stress coefficient is thus relevant for studying reservoir deformation and for evaluating 4-D seismic. The effective stress coefficient, α, of chalk from the reservoir zone of the Valhall field, North Sea was estimated from mechanical tests. The coefficient α was compared to Biot's coefficient, β (the dynamic effective stress coefficient) as calculated from density and sonic velocity data. The parameter α is highly relevant for effective stress prediction, as it is directly related to mechanical strain, whereas β is easy to estimate from logging data. Unexpectedly, our data indicate that β measured prior to deformation forms an upper rather than a lower bound for α, so that α cannot be assumed equal to one. During elastic deformation caused by pore pressure drawdown, β predicts α well.
Numerical Modeling of Fully Coupled Hydraulic Fracture Propagation in Naturally Fractured Poro-elastic Reservoir
Authors: Rahman M M , Aghighi Ali , Shaik Abdul Ravoof 
Published: June 2009

Abstract
The effect of a pre-existing natural fracture on the extension of a hydraulically induced fracture has been modeled based on poro-elastic behavior. The approach of Warpiniski and Teufel was adopted to evaluate the fracture propagation that would occur after an induced fracture intersects an existing natural fracture. This two dimensional numerical model will simulate the interaction between an induced propagating fracture and natural fracture.
The model departs radically from current models in that poro-elastic behavior is not used, uniform pressure inside the natural fracture was used in practice this is not true and effect of fracture toughness ignored. A modified leak-off model for intersecting fracture based on poro-elasticity is introduced as the leak-off is increased in the intersection. Besides these previous model used startup solution using PKN model. In this model a triple system of wellbore-fracture-formation is considered and the fracture will initiate first then propagate some extent then interact with natural fracture. A poro-elastic solution for the stresses in the interaction zone has been used as a basis for hydraulic/natural fracture interaction criteria. The criteria compares favorably with the experimental results.
Comparison of the numerical results with experimental results has shown that the main effect of the natural fractures is the width constriction that occurs when the induced fracture propagates into the natural fracture. Numerical and experimental studies for such propagation indicate a near wellbore width and effective length reduction due to the additional normal stress acting on the plane of the induced fracture.
ApoCIII-Enriched LDL in Type 2 Diabetes Displays Altered Lipid Composition, Increased Susceptibility for Sphingomyelinase, and Increased Binding to Biglycan
Authors: Hiukka Anne , Ståhlman Marcus , Pettersson Camilla , Levin Malin , Adiels Martin , Teneberg Susanne , Leinonen Eeva S. , Hultén Lillemor Mattsson , Wiklund Olov , Orešič Matej , Olofsson Sven-Olof , Taskinen Marja-Riitta , Ekroos Kim , Borén Jan 
Published: June 2009

OBJECTIVE
Apolipoprotein CIII (apoCIII) is an independent risk factor for cardiovascular disease, but the molecular mechanisms involved are poorly understood. We investigated potential proatherogenic properties of apoCIII-containing LDL from hypertriglyceridemic patients with type 2 diabetes.

RESEARCH DESIGN AND METHODS
LDL was isolated from control subjects, subjects with type 2 diabetes, and apoB transgenic mice. LDL-biglycan binding was analyzed with a solid-phase assay using immunoplates coated with biglycan. Lipid composition was analyzed with mass spectrometry. Hydrolysis of LDL by sphingomyelinase was analyzed after labeling plasma LDL with [3H]sphingomyelin. ApoCIII isoforms were quantified after isoelectric focusing. Human aortic endothelial cells were incubated with desialylated apoCIII or with LDL enriched with specific apoCIII isoforms.

RESULTS
We showed that enriching LDL with apoCIII only induced a small increase in LDL-proteoglycan binding, and this effect was dependent on a functional site A in apoB100. Our findings indicated that intrinsic characteristics of the diabetic LDL other than apoCIII are responsible for further increased proteoglycan binding of diabetic LDL with high-endogenous apoCIII, and we showed alterations in the lipid composition of diabetic LDL with high apoCIII. We also demonstrated that high apoCIII increased susceptibility of LDL to hydrolysis and aggregation by sphingomyelinases. In addition, we demonstrated that sialylation of apoCIII increased with increasing apoCIII content and that sialylation of apoCIII was essential for its proinflammatory properties.

CONCLUSIONS
We have demonstrated a number of features of apoCIII-containing LDL from hypertriglyceridemic patients with type 2 diabetes that could explain the proatherogenic role of apoCIII.
Association Between Osteoprotegerin G1181C and T245G Polymorphisms and Diabetic Charcot Neuroarthropathy
Authors: Pitocco Dario , Zelano Giovanni , Gioffrè Giuseppina , Di Stasio Enrico , Zaccardi Francesco , Martini Francesca , Musella Tittania , Scavone Giuseppe , Galli Marco , Caputo Salvatore , Mancini Lorena , Ghirlanda Giovanni 
Published: June 2009

OBJECTIVE
Charcot neuroarthropathy is a disabling complication of diabetes. Although its pathogenesis remains unknown, we suppose that genetics may play a relevant role.

RESEARCH DESIGN AND METHODS
We performed a case-control study with 59 subjects with diabetic Charcot neuroarthropathy (Ch group), 41 with diabetic neuropathy without Charcot neuroarthropathy (ND group), and 103 healthy control subjects (H group) to evaluate the impact of two single nucleotide polymorphisms (SNPs) of the osteoprotegerin gene (G1181C and T245G) on the risk of Charcot neuroarthropathy.

RESULTS
Regarding the SNPs of G1181C, we found a significant linkage between the G allele and Charcot neuroarthropathy (Ch vs. ND, odds ratio [OR] 2.32 [95% CI 1.3–4.1], P = 0.006; Ch vs. H, 2.10 [1.3–3.3], P = 0.002; and ND vs. H, 0.90 [0.7–1.9], P = 0.452); similarly, we found a linkage with the G allele of T245G (Ch vs. ND, 6.25 [2.2–19.7], P &lt; 0.001; Ch vs. H, 3.56 [1.9–6.7], P = 0.001; and ND vs. H, 0.54 [0.6–5.7], P = 0.304), supporting a protective role for the allele C and T, respectively. For this reason we investigated the frequency of the protective double homozygosis CC + TT (7% in Ch) that was significantly lower in Ch compared with H (0.18 [0.06–0.5], P = 0.002) and with ND (0.17 [0.05–0.58], P = 0.006), whereas there was no difference between H and ND (1.05 [0.43–2.0], P = 0.468). In a multivariate logistic backward regression model, only weight and the lack of CC and TT genotypes were independently associated with the presence of Charcot neuroarthropathy.

CONCLUSIONS
This is the first study that shows an association between genetic regulation of bone remodeling and Charcot neuroarthropathy.
TSH-Lowering Effect of Metformin in Type 2 Diabetic Patients
Authors: Cappelli Carlo , Rotondi Mario , Pirola Ilenia , Agosti Barbara , Gandossi Elena , Valentini Umberto , De Martino Elvira , Cimino Antonio , Chiovato Luca , Agabiti-Rosei Enrico , Castellano Maurizio 
Published: June 2009

OBJECTIVE
To assess the interplay between metformin treatment and thyroid function in type 2 diabetic patients.

RESEARCH DESIGN AND METHODS
The acute and long-term effects of metformin on thyroid axis hormones were assessed in diabetic patients with primary hypothyroidism who were either untreated or treated with levothyroxine (L-T4), as well as in diabetic patients with normal thyroid function.

RESULTS
No acute changes were found in 11 patients with treated hypothyroidism. After 1 year of metformin administration, a significant thyrotropin (TSH) decrease (P &lt; 0.001) was observed in diabetic subjects with hypothyroidism who were either treated (n = 29; from 2.37 ± 1.17 to 1.41 ± 1.21 mIU/l) or untreated (n = 18; 4.5 ± 0.37 vs. 2.93 ± 1.48) with L-T4, but not in 54 euthyroid subjects. No significant change in free T4 (FT4) was observed in any group.

CONCLUSIONS
Metformin administration influences TSH without change of FT4 in patients with type 2 diabetes and concomitant hypothyroidism. The need for reevaluation of thyroid function in these patients within 6–12 months after starting metformin is indicated.
Tubular and Glomerular Injury in Diabetes and the Impact of ACE Inhibition
Authors: Nielsen Stine E. , Sugaya Takeshi , Tarnow Lise , Lajer Maria , Schjoedt Katrine J. , Astrup Anne Sofie , Baba Tsuneharu , Parving Hans-Henrik , Rossing Peter 
Published: June 2009

OBJECTIVE
We studied tubular and glomerular damage in type 1 diabetic patients by measuring urinary–liver fatty acid binding protein (U-LFABP) and albuminuria. Subsequently, we evaluated the effect of ACE inhibition on U-LFABP in patients with diabetic nephropathy.

RESEARCH DESIGN AND METHODS
We studied Caucasians with type 1 diabetes: 58 with normoalbuminuria (urinary albumin &lt;30 mg/24 h), 45 with persistent microalbuminuria (30–300 mg/24 h), and 45 with persistent macroalbuminuria (≥300 mg/24 h). A control group consisted of 57 healthy individuals. The groups were matched by sex and duration of diabetes. In addition, U-LFABP was measured in 48 type 1 diabetic patients with diabetic nephropathy in a randomized crossover trial consisting of 2 months of treatment with 20, 40, and 60 mg lisinopril once daily in random order.

RESULTS
In the cross-sectional study, levels of U-LFABP were significantly higher in normoalbuminuric patients versus those in the control group (median 2.6 [interquartile range 1.3–4.1] vs. 19 [0.8–3.0] μg/g creatinine, P = 0.02) and increased with increasing levels of albuminuria (microalbuminuric group 4.2 [1.8–8.3] μg/g creatinine and nephropathy group 71.2 [8.1–123.4], P &lt; 0.05 for all comparisons). U-LFABP correlates with the urinary albumin-to-creatinine ratio (R2 = 0.54, P &lt; 0.001). In the intervention study, all doses of lisinopril significantly reduced urinary albumin excretion rate and U-LFABP from baseline. The reductions in U-LFABP were 43, 46, and 40% with increasing doses of lisinopril (NS).

CONCLUSIONS
An early and progressive increase in tubulointerstitial damage as reflected by increased U-LFABP levels occurs in type 1 diabetic patients and is associated with albuminuria. Furthermore, ACE inhibition reduces the tubular and glomerular damage and dysfunction.
Characterization of edema by diffusion-weighted imaging in experimental traumatic brain injury
Authors: Ito Junki , Marmarou Anthony , Barzó Pál , Fatouros Panos , Corwin Frank 
Published: June 2009

✓ The objective of this study was to use diffusion-weighted magnetic resonance imaging (DWI) to help detect the type of edema that develops after experimental trauma and trauma coupled with hypotension and hypoxia (THH). Reduction in the apparent diffusion coefficients (ADCs) is thought to represent cytotoxic edema. In a preliminary series of experiments, the infusion edema model and middle cerebral artery occlusion models were used to confirm the direction of ADC change in response to purely extracellular and cytotoxic edema, respectively. The ADCs increased (p < 0.05) in the case of extracellular edema and decreased (p < 0.001) in cytotoxic edema.Following these initial experiments, a new impact acceleration model was used to induce traumatic brain injury. Thirty-six adult Sprague-Dawley rats were separated into four groups: sham, trauma alone, hypoxia and hypotension (HH), and THH. Following trauma, a 30-minute insult of hypoxia (PaO2of 40 mm Hg) and hypotension (mean arterial blood pressure (MABP) of 30 mm Hg) were imposed and the animals were resuscitated. The DWI was carried out at four 1-hour intervals postinjury, and MABP, intracranial pressure (ICP), cerebral perfusion pressure (CPP), and cerebral blood flow (CBF) were monitored. The ADCs in the control and HH groups remained unchanged. The ADCs in the THH group rapidly decreased from a control level of 0.68 ± 0.05 × 10−3mm2/second to 0.37 ± 0.09 3 10−3mm2/second by 3 hours posttrauma (p < 0.001). In this group, the decreased CBF and CPP during secondary insult remained low despite resuscitation, with the ICP increasing to 56 6 7 mm Hg by 3 hours. In the trauma alone group, the rise in ICP reached a maximum value (28 ± 3 mm Hg) at 30 minutes with a significant and sustained increase in CBF despite a gradual decrease in CPP. The ADCs in this group were not significantly reduced. The data lead the authors to suggest that the rise in ICP following severe trauma coupled with secondary insult in this model is predominately caused by cytotoxic edema and that ischemia plays a major role in the development of brain edema after head injury.
Treatment of lumbar spinal stenosis by extensive unilateral decompression and contralateral autologous bone fusion: operative technique and results
Authors: diPierro Charles G. , Helm Gregory A. , Shaffrey Christopher I. , Chadduck James B. , Henson Scott L. , Malik Jacek M. , Szabo Thomas A. , Simmons Nathan E. , Jane John A. 
Published: June 2009

✓ A new surgical technique for the treatment of lumbar spinal stenosis features extensive unilateral decompression with undercutting of the spinous process and, to preserve stability, uses contralateral autologous bone fusion of the spinous processes, laminae, and facets. The operation was performed in 29 patients over a 19-month period ending in December of 1991. All individuals had been unresponsive to conservative treatment and presented with low-back pain in addition to signs and symptoms consistent with neurogenic claudication or radiculopathy. Nine had undergone previous lumbar decompressive surgery. The minimum and mean postoperative follow-up times were 2 and 2 1/2 years, respectively. The mean patient age was 64 years; only two patients were younger than 50 years of age.Of the patients with neurogenic claudication, 69% reported complete pain relief at follow-up review. Of those with radicular symptoms, 41% had complete relief and 23% had mild residual pain that was rated 3 or less on a pain—functionality scale of 0 to 10. For the entire sample, this surgery decreased pain from 9.2 to 3.3 (p < 0.0001) on the scale. Sixty-nine percent of patients were satisfied with surgery. Low-back pain was significantly relieved in 62% of all patients (p < 0.0001). Low-back pain relief correlated negatively with number of levels decompressed (p < 0.05). To assess fusion, follow-up flexion/extension radiographs were obtained, and no motion was detected at the surgically treated levels in any patient.The results suggest that this decompression procedure safely and successfully treats not only the radicular symptoms caused by lateral stenosis but also the neurogenic claudication symptoms associated with central stenosis. In addition, the procedure, by using contralateral autologous bone fusion along the laminae and spinous processes, can preserve stability without instrumentation.
Randomized, double-blind, vehicle-controlled trial of tirilazad mesylate in patients with aneurysmal subarachnoid hemorrhage: a cooperative study in Europe, Australia, and New Zealand
Authors: Kassell Neal F. , Haley E. Clarke , Apperson-Hansen Carolyn , Alves Wayne M. , _ _ 
Published: June 2009

✓ Tirilazad mesylate, a nonglucocorticoid 21-aminosteroid, has been shown in experimental models to reduce vasospasm following subarachnoid hemorrhage (SAH) and to reduce infarct size from focal cerebral ischemia. To test whether treatment with tirilazad would reduce ischemic symptoms from vasospasm and improve overall outcome in patients with ruptured aneurysms, a prospective randomized, double-blind, vehicle-controlled trial was conducted at 41 neurosurgical centers in Europe, Australia, and New Zealand. One thousand twenty-three patients were randomly assigned to receive 0.6, 2, or 6 mg/kg per day of intravenously administered tirilazad or a placebo containing the citrate vehicle. All patients were also treated with intravenously administered nimodipine. Patients receiving 6 mg/kg per day of tirilazad had reduced mortality (p = 0.01) and a greater frequency of good recovery on the Glasgow Outcome Scale 3 months after SAH (p = 0.01) than similar patients treated with vehicle. There was a reduction in symptomatic vasospasm in the group that received 6 mg/kg per day tirilazad; however, the difference was not statistically significant (p = 0.048). The benefits of treatment with tirilazad were predominantly shown in men rather than in women. There were no material differences between the outcomes in the groups treated with 0.6 and 2 mg/kg tirilazad per day and the group treated with vehicle. Tirilazad was well tolerated at all three dose levels.
These observations suggest that tirilazad mesylate, at a dosage of 6 mg/kg per day, is safe and improves overall outcome in patients (especially in men) who have experienced an aneurysmal SAH.