bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rock Strength from Core and Logs, Where We Stand and Ways to Go
Authors: Khaksar A. , Taylor P. G. , Fang Z. , Kayes T. , Salazar A. , Rahman K. 
Published: June 2009

AbstractKnowledge of accurate rock strength is essential for in situ stress estimation, wellbore stability analysis, sand production prediction and other geomechanical applications. Reliable quantitative data on rock strength can only be obtained from cores. However, cores are limited, discontinuous and often biased. Consequently, rock strength evaluation is primarily based on log strength indicators, calibrated where possible against limited core measured values. There are a number of published log-core strength correlations that can be used for rock strength modelling. These empirical relationships are developed for specific rock type, age, depth range and field. Their general applications, therefore, need to be critically assessed on a case by case basis. This paper briefly: (i) outlines the best practice for obtaining quality rock strength data from core tests; (ii) presents common empirical rock strength equations for sedimentary rocks and (iii) discusses ways of improving rock strength estimates.While some equations such as porosity-based or sonic log-based rock strength models work reasonably well, rock strength variations within individual rock properties show considerable scatter, indicating that most of the empirical models are not sufficiently generic to fit all rocks in the database. Like any other physical rock properties, the variation in rock strength in a given sedimentary rock is controlled by mineralogy, sedimentology and micro-structure of the rock and simple log-derived rock strength models need further modification and classification incorporating these geological characteristics.This paper has shown that when sufficient core rock strength data exists, applications of computing techniques, such as fuzzy logic and cluster pattern recognition, coupled with sedimentary facies analysis and diagenetic classification can improve strength estimation. Semi-continuous impact energy logs using portable non-destructive testing tools can be correlated with petrophysical logs to generate mechanical facies and improved sampling for conventional rock testing.
Partial Movement of Asphaltene in Presence of Connate Water in Vapex Process
Authors: Ardali M. , Kharrat R. , Rostami B. , Derakhshanfar M. 
Published: June 2009

AbstractVapor extraction (VAPEX) process is solvent analogue of SAGD process in which low molecular weight solvent are used to reduce the viscosity of heavy oil and bitumen. This process may be a good candidate to be applied in problematic reservoirs in which thermal methods are not efficient due to severe heat losses.Asphaltene precipitation as a result of compositional alteration of solvent/bitumen has substantial effects on performance of VAPEX. In this process if operating pressure is very close to dew point pressure, asphaltene precipitation occurs. In-situ deasphalting of heavy oil and bitumen reduces the viscosity of the produced oil and creates the oil that is more easily refined, but the main concern is whether this advantage can outweigh reduced permeability and plugging of formation caused by adsorption and precipitation of asphaltenes.In current work experiments have been conducted in low permeability sandpacks in both dry and non-dry systems to assess the performance of Vapex process when asphaltene precipitation occurs. Experiments are carried out in a 2D visual cell using highly asphaltenic heavy oil from one of Iranian reservoirs (Kuh-e-Mond) and propane as a solvent.The results show that performance of Vapex process increases when asphaltene precipitation occurs provided that optimal pressure has been designed to prevent extensive asphaltene deposition and subsequent plugging of porous media. It has been observed that adsorption of asphaltenes has considerably decreased in non-dry systems. Movement of precipitated asphaltene and less adsorption in non-dry experiments results in a more stable and efficient Vapex process while in dry experiments higher adsorption of asphaltenes resulted in plugging of low permeability porous medium.
Increased Rates, Reserves, and Revenues From Heavy Oil Reservoir Using ESP Technology: A Suriname Case Study
Authors: Anthony E. , Grauwde G. , Domangue Michael 
Published: June 2009

Abstract
Wells producing heavy oil (16° API), completed in shallow, high permeability, low-dipping, and very unconsolidated reservoirs experienced very early water breakthrough, short-circuiting significant reserve potential. Wells were completed as vertical open-hole gravel packs and produced ‘water-free’ at rates 150 – 300 bopd for a few months, then plummeted to 25 – 50 bopd when water broke through. Progressing Cavity Pumps were the primary Artificial Lift method used in 5.5" casing completions. In an attempt to restore some of the lost oil production after water breakthrough, efforts to reduce the flowing BHP were made by using high-volume PC pumps. Fluid withdrawal rates were increased from ±350 bpd to ±700 bpd with no significant change in fluid level (FBHP), watercut, or oil production. The Electrical Submersible Pump (ESP) was then used to reduce the FBHP sufficiently to stimulate increased oil production to the wellbore. Fluid withdrawal rates were taken to ±2200 bpd which achieved approximately 100 psi(25%) reduction in FBHP.
Sustained oil production increases between 100% and 400% were realized. Watercuts increased by no more than 3%. Dynamic fluid levels in surrounding wells showed a temporary reduction, but increased and stabilized at original levels after 2-3 months, indicating a very active edge-water drive mechanism. Infill wells with 7" production casings are planned to accommodate larger volume ESP's. No sand production has been observed to date indicating no deterioration of the gravel pack at these elevated extraction rates. At prevailing oil prices, project investments were recovered within 4 months.
Under the conditions of low GOR, low dipping, high permeability, edge-water drive, heavy oil reservoirs, increased fluid extraction rates can result in significant increase in oil production rates and producible reserves, even though wells may have experienced early water breakthroughs.
Well Production Forecasting by Extrapolation of the Deconvolution of Well Test Pressure Transients
Authors: Whittle Tim , Hui Jiang , Young Stuart , Gringarten Alain 
Published: June 2009

Abstract
The deconvolution of well test pressure transient data provides a constant rate pressure response that applies for the duration of the test. By extrapolating this response in time, the future performance of a well can be predicted.
The extrapolation can include constraints defined by estimates of the volume of reservoir connected to the well but otherwise, relies only on information that is normally available at the time of testing. Uncertainty in either the deconvolution or the connected volume will result in a variety of extrapolations that defines the range of expected well performance. The advantage of this procedure is that a well's future production profile can be estimated very quickly and easily. Such a scoping exercise helps to understand a well's potential and to define the expected range of outcomes from more detailed modelling. Furthermore, it can be an efficient method for screening prospects when time and resources are limited.
By monitoring the actual well performance against its prediction, underperforming wells can be identified for work-over. If permanent downhole pressure gauge data are available, the deconvolution can be continuously updated thus improving the production forecast.
Where a production well is planned that is of a different type to the tested well (e.g. a horizontal or hydraulically fractured well instead of a normal vertical well), a technique is described to modify the tested well's deconvolved response to account for the change in well type whilst preserving the pressure transient response due to the reservoir and its boundaries.
Two field examples of gas well tests are presented which demonstrate the method and the predicted production profiles are compared with observed data.
Hydrate Problem in the Oil Production Industry
Authors: Buzatoiu B. , Popp V. V. , Loas I. R. 
Published: June 2009

Abstract
The paper briefly presents some important aspects related to natural gas hydrates.
Some theoretical aspects in connection with the thermodynamic and kinetic mechanisms of hydrates formation are reviewed, following which the methods for controlling their generation during drilling, gas production, transportation and processing are mentioned.
At the end of the paper the possibilities for hydrate utilization in connection with natural gas storage are being considered.
Genetic Disruption of Myostatin Reduces the Development of Proatherogenic Dyslipidemia and Atherogenic Lesions In Ldlr Null Mice
Authors: Tu Powen , Bhasin Shalender , Hruz Paul W. , Herbst Karen L. , Castellani Lawrence W. , Hua Ning , Hamilton James A. , Guo Wen 
Published: June 2009

OBJECTIVE
Insulin-resistant states, such as obesity and type 2 diabetes, contribute substantially to accelerated atherogenesis. Null mutations of myostatin (Mstn) are associated with increased muscle mass and decreased fat mass. In this study, we determined whether Mstn disruption could prevent the development of insulin resistance, proatherogenic dyslipidemia, and atherogenesis.

RESEARCH DESIGN AND METHODS
C57BL/6 Ldlr−/− mice were cross-bred with C57BL/6 Mstn−/− mice for &gt;10 generations to generate Mstn−/−/Ldlr−/− double-knockout mice. The effects of high-fat/high-cholesterol diet on body composition, plasma lipids, systemic and tissue-specific insulin sensitivity, hepatic steatosis, as well as aortic atheromatous lesion were characterized in Mstn−/−/Ldlr−/− mice in comparison with control Mstn+/+/Ldlr−/− mice.

RESULTS
Compared with Mstn+/+/Ldlr−/− controls, Mstn−/−/ Ldlr−/− mice were resistant to diet-induced obesity, and had greatly improved insulin sensitivity, as indicated by 42% higher glucose infusion rate and 90% greater muscle [3H]-2-deoxyglucose uptake during hyperinsulinemic-euglycemic clamp. Mstn−/−/Ldlr−/− mice were protected against diet-induced hepatic steatosis and had 56% higher rate of hepatic fatty acid β-oxidation than controls. Mstn−/−/Ldlr−/− mice also had 36% lower VLDL secretion rate and were protected against diet-induced dyslipidemia, as indicated by 30–60% lower VLDL and LDL cholesterol, free fatty acids, and triglycerides. Magnetic resonance angiography and en face analyses demonstrated 41% reduction in aortic atheromatous lesions in Ldlr−/− mice with Mstn deletion.

CONCLUSIONS
Inactivation of Mstn protects against the development of insulin resistance, proatherogenic dyslipidemia, and aortic atherogenesis in Ldlr−/− mice. Myostatin may be a useful target for drug development for prevention and treatment of obesity and its associated type 2 diabetes and atherosclerosis.
Glucagon-Like Peptide-1 Receptor Activation Modulates Pancreatitis-Associated Gene Expression But Does Not Modify the Susceptibility to Experimental Pancreatitis in Mice
Authors: Koehler Jacqueline A. , Baggio Laurie L. , Lamont Benjamin J. , Ali Safina , Drucker Daniel J. 
Published: June 2009

OBJECTIVE
Clinical reports link use of the glucagon-like peptide-1 receptor (GLP-1R) agonists exenatide and liraglutide to pancreatitis. However, whether these agents act on the exocrine pancreas is poorly understood.

RESEARCH DESIGN AND METHODS
We assessed whether the antidiabetic agents exendin (Ex)-4, liraglutide, the dipeptidyl peptidase-4 inhibitor sitagliptin, or the biguanide metformin were associated with changes in expression of genes associated with the development of experimental pancreatitis. The effects of Ex-4 when administered before or after the initiation of caerulein-induced experimental pancreatitis were determined. The importance of endogenous GLP-1R signaling for gene expression in the exocrine pancreas and the severity of pancreatitis was assessed in Glp1r−/− mice.

RESULTS
Acute administration of Ex-4 increased expression of egr-1 and c-fos in the exocrine pancreas. Administration of Ex-4 or liraglutide for 1 week increased pancreas weight and induced expression of mRNA transcripts encoding the anti-inflammatory proteins pancreatitis-associated protein (PAP) (RegIIIβ) and RegIIIα. Chronic Ex-4 treatment of high-fat–fed mice increased expression of PAP and reduced pancreatic expression of mRNA transcripts encoding for the proinflammatory monocyte chemotactic protein-1, tumor necrosis factor-α, and signal transducer and activator of transcription-3. Sitagliptin and metformin did not significantly change pancreatic gene expression profiles. Ex-4 administered before or after caerulein did not modify the severity of experimental pancreatitis, and levels of pancreatic edema and serum amylase were comparable in caerulein-treated Glp1r−/− versus Glp1r+/+ mice.

CONCLUSIONS
These findings demonstrate that GLP-1 receptor activation increases pancreatic mass and selectively modulates the expression of genes associated with pancreatitis. However, activation or genetic elimination of GLP-1R signaling does not modify the severity of experimental pancreatitis in mice.
Prevention of Diabetes Self-Management Program (PREDIAS): Effects on Weight, Metabolic Risk Factors, and Behavioral Outcomes
Authors: Kulzer Bernhard , Hermanns Norbert , Gorges Daniela , Schwarz Peter , Haak Thomas 
Published: June 2009

OBJECTIVE
To evaluate the efficacy of the group program PREDIAS for diabetes prevention.

RESEARCH DESIGN AND METHODS
PREDIAS consists of 12 lessons and aims at lifestyle modification. The control group received written information about diabetes prevention. In this study, a total of 182 persons with an elevated diabetes risk participated (aged 56.3 ± 10.1 years, 43% female, and BMI 31.5 ± 5.3 kg/m2).

RESULTS
After 12 months, weight loss was significantly higher (P = 0.001) in PREDIAS than in the control group (−3.8 ± 5.2 vs. −1.4 ± 4.09 kg). There were also significant effects (P = 0.001) on fasting glucose (control group 1.8 ± 13.1 mg/dl vs. PREDIAS −4.3 ± 11.3 mg/dl), duration of physical activity per week (control group 17.9 ± 63.8 min vs. PREDIAS 46.6 ± 95.5 min; P = 0.03), and eating behavior.

CONCLUSIONS
PREDIAS significantly modified lifestyle factors associated with an elevated diabetes risk.
Nitric oxide mediation of chemoregulation but not autoregulation of cerebral blood flow in primates
Authors: Thompson B. Gregory , Pluta Ryszard M. , Girton Mary E. , Oldfield Edward H. 
Published: June 2009

✓ The authors sought to develop a model for assessing in vivo regulation of cerebral vasoregulation by nitric oxide (NO), originally described as endothelial-derived relaxing factor, and to use this model to establish the role of NO in the regulation of cerebral blood flow (CBF) in primates. By using regional intraarterial perfusion, the function of NO in cerebral vasoregulation was examined without producing confounding systemic physiological effects. Issues examined were: whether resting vasomotor tone requires NO; whether NO mediates vasodilation during chemoregulation and autoregulation of CBF; and whether there is a relationship between the degree of hypercapnia and hypotension and NO production. Twelve anesthetized (0.5% isoflurane) cynomolgus monkeys were monitored continuously for cortical CBF, PaCO2, and mean arterial pressure (MAP), which were systematically altered to provide control and experimental curves of chemoregulation (CBF vs. PaCO2) and autoregulation (CBF vs. MAP) during continuous intracarotid infusion of 1) saline and 2) an NO synthase inhibitor (NOSI), either l-n-monomethyl arginine or nitro l-arginine.
During basal conditions (PaCO2 of 38–42 mm Hg) NOSI infusion of internal carotid artery (ICA) reduced cortical CBF from 62 (saline) to 53 ml/100 g/per minute (p < 0.01), although there was no effect on MAP. Increased CBF in response to hypercapnia was completely blocked by ICA NOSI. The difference in regional (r)CBF between ICA saline and NOSI infusion increased linearly with PaCO2 when PaCO2 was greater than 40 mm Hg, indicating a graded relationship of NO production, increasing PaCO2, and increasing CBF. Diminution of CBF with NOSI infusion was reversed by simultaneous ICA infusion of l-arginine, indicating a direct role of NO synthesis in the chemoregulation of CBF.
Hypotension and hypertension were induced with trimethaphan camsylate (Arfonad) and phenylephrine at constant PaCO2 (40 ± 1 mm Hg). Autoregulation in response to changes in MAP from 50 to 140 mm Hg was unaffected by ICA infusion of NOSI.
In primates, cerebral vascular tone is modulated in vivo by NO; continuous release of NO is necessary to maintain homeostatic cerebral vasodilation; vasodilation during chemoregulation of CBF is mediated directly by NO production; autoregulatory vasodilation with hypotension is not mediated by NO; and increasing PaCO2 induces increased NO production.
Multilevel anterior thoracic discectomies and anterior interbody fusion using a microsurgical thoracoscopic approach
Authors: Dickman Curtis A. , Mican Camilla A. 
Published: June 2009

✓ A video-assisted thoracoscopic microsurgical approach was performed to treat a myelopathic patient with a severe kyphotic deformity caused by chronic nonunion of compression fractures of the T7–9 vertebrae. The kyphotic deformity was treated by combined operative procedures. First, an anterior release was performed using a thoracoscopic technique, sectioning the anterior longitudinal ligament and performing multilevel thoracic discectomies. Next, a posterior reduction and internal fixation of the deformity was achieved using hook-rod instrumentation. Finally, bone graft harvested during the posterior approach was used for interbody fusion via a thoracoscopic approach.
Microsurgical thoracoscopic techniques potentially can be used in a variety of spinal surgeries. Compared to transthoracic and posterolateral approaches, this technique presents distinct advantages to treatment of anterior spinal pathology. The small incisions made into the intercostal spaces without retracting the ribs may reduce postoperative pain, shorten the length of hospitalization, and allow early return to activity.
The operative techniques used in this case are described in detail. This report demonstrates that thoracoscopic discectomies and interbody fusion are technically feasible and can be effectively performed with acceptable results.
Dural arteriovenous fistula of the posterior fossa developing after surgical occlusion of the sigmoid sinus
Authors: Sakaki Toshisuke , Morimoto Tetsuya , Nakase Hiroyuki , Kakizaki Toshio , Nagata Kiyoshi 
Published: June 2009

✓ In this article, the authors present five cases of dural arteriovenous fistula (AVF) that developed in the transverse—sigmoid sinus 2 to 6 years after sacrifice of the sigmoid sinus because of tumor involvement. The original tumor was meningioma in two patients and neurinoma, glomus jugulare tumor, and ameloblastoma in one patient each. The involved sigmoid sinus was resected along with the tumor and ligated at the normal edge; all that remained of the sigmoid sinus was a small stump on the retrosigmoid portion. Serial angiography performed before and after tumor surgery revealed no abnormal arteriovenous communications or dural AVF in any of the cases.
Although many reports have suggested that sinus thrombosis is a precipitating factor in the pathogenesis of dural AVFs, this has been difficult to verify because of the small number of cases in which serial angiography was performed before the development of a dural AVF. In all of the cases presented in this article, surgical resection of a dural AVF and histological examination were performed. Subintimal fibrous thickening was marked, and the sinus wall was found to contain many dural vessels. Organized thrombosis with neovascularization was seen in only two patients. These cases demonstrate that subintimal fibrous thickening and a hypertrophied sinus wall secondary to increased intrasinus pressure or sinus thrombosis occurring after sinus occlusion can provoke the development of a dural AVF within the course of a lifetime. Maintenance of intrasinus blood flow may be very important to prevent this late postoperative complication.
Microvascular anatomy of dural arteriovenous abnormalities of the spine: a microangiographic study
Authors: McCutcheon Ian E. , Doppman John L. , Oldfield Edward H. 
Published: June 2009

✓ Although most vascular abnormalities of the spinal cord are now ascribed to an abnormal communication between a dural artery and a medullary vein on the dura near a sensory nerve root, these lesions are too small for their anatomy to be demonstrated directly by spinal arteriography. Thus, it is unknown whether the site of dural arteriovenous shunting is an arteriovenous malformation (AVM), implying a congenital origin, or is a direct arteriovenous fistula (AVF), implying an acquired etiology.
The authors treated six patients by en bloc resection of the involved dural root sleeve, proximal nerve root, and adjacent spinal dura. All of the patients presented with myelopathy and their arteriograms were consistent with a spinal dural vascular malformation. The lesions occurred between T-6 and T-12, levels at which clinical deficits from such resection are minimal. The dural artery or medullary vein associated with the vascular malformation was cannulated and a dilute solution of barium sulfate was injected during sequential fine-grain radiography. In all of the lesions the artery split into daughter vessels that coalesced one to three times to form a skein of arterial loops in the dura that invariably emptied into a medullary vein without an intervening capillary plexus. Several medium-to-small collateral vessels arising from adjacent intercostal or lumbar arteries were commonly present in the dura and converged at the site of the AVF to join a single medullary vein.
These results show that spinal dural AVMs are direct AVFs that link the dural branch of the radiculo-medullarydural artery with the intradural medullary vein. They also provide an anatomical explanation for the presence of a multiple segmental arterial supply and a single draining medullary vein of spinal dural AVFs, and the propensity for reestablishment of flow through the arteriovenous shunt after embolic occlusion.