bluuebunny/crossref_metadata_2025_split huggingface dataset:
Veslefrikk Scale Control Strategy and Economic Implications: Revisited 7 Years Later—Did We Improve?
Authors: Tjomsland Tore , Sæten Jens Olav , Vikane Olav , Zettlitzer Michael , Chen Ping 
Published: May 2008

Abstract
The Veslefrikk field, located in block 30/3 of the Norwegian sector of the North Sea, has been on production since 1989 and is in the decline phase. Due to seawater injection, commingled production and high reservoir temperature, severe tendency towards deposition of sulphate and carbonate scale has been observed. The economic consequences of scale and the benefit from scale control work had been assessed quantitatively and presented at the 2001 SPE Third International Symposium on Oilfield Scale (Tjomsland et al., 2001). The study showed that the scale control strategy had been an economic success. However, annually more than 4% of the well productivity was still lost due to scale deposition, and in consequence it was recommended to intensify the scale management procedures. A task force involving scale control experts from the licence partners was established. In co-operation with service companies, the group systematically assessed new scale control measures for use at Veslefrikk. In 2006 a benchmark against the 2001 study was performed to investigate if the scale control work had been improved. The results showed that the scale potential was approximately the same in the second period (June 1999-2005) as in the first (1993- May1999), but a significant improvement in downhole scale control was now obtained through a more aggressive use of preventive scale inhibitor squeezes and the implementation of new technology. However, the study also concluded that scale inhibitor squeezes themselves in some cases caused formation damage, most likely due to the formation of water blocks. Recently a mutual solvent that can be incorporated as part of the squeeze pre-flush was qualified for use on Veslefrikk. This has not only reduced the risk of formation damage, but in some cases even increased productivity has been observed.
Precipitation of Iron and Calcium Carbonate in Pipelines at Varying MEG Contents
Authors: Flaten Ellen Marie , Watterud Geir , Andreassen Jens-Petter , Seiersten Mario 
Published: May 2008

Abstract
Injection of inhibitors for gas hydrate formation during transportation of wet gas/condensate in pipelines strongly affects the tolerance for produced formation water. The use of monoethylene glycol (MEG) as hydrate inhibitor can be combined with pH increase (pH stabilisation) as corrosion control for carbon steel pipelines. The pH increase promotes precipitation of iron carbonate which forms a protective layer for corrosion at the steel surface. However, the elevated alkalinity downstream of the MEG injection point, combined with calcium ions from produced formation water, might result in the precipitation of calcium carbonate. The Fe2+ formed by corrosion will accumulate in the aqueous phase down the pipeline. Even with low corrosion rate, the Fe2+ concentration at the pipeline outlet is typically 10 – 100 ppm.
This work presents the impact of MEG on the precipitation rate of calcium- and iron carbonate, and how small amounts of Fe2+ affects calcium carbonate precipitation. The induction time for precipitation of both iron- and calcium carbonate are significantly prolonged by increased concentration of MEG. This effect is a result of retarded crystal growth and not reduced nucleation rates. The presence of 1-40 ppm Fe2+ also prolongs the induction time for calcium carbonate precipitation and the effect increases with concentration.
The presence of MEG and Fe2+ also affects the polymorphism of CaCO3. Vaterite forms at high MEG concentration (&gt;90 wt%). Its growth is retarded by the presence of traces of Fe2+ and the induction time for precipitation increases with increasing iron. Lower MEG concentrations give aragonite mainly. Iron also lowers the growth rate of this polymorph, although not to such an extent as for vaterite.
Design and Field Deployment of Scale Inhibitors for Reducing the Risk for Chalk Influx Post Squeeze Treatments in Multiple Fractured Horizontal Wells in BP Valhall
Authors: Thingvoll Torgrim T. , Heath Steve , Flatebø Roar , Madland Merete , Clark Graham , Strachan Catherine , Vorland Kim Andre Nesse , Korsnes Reidar I. 
Published: May 2008

Abstract
Valhall is a fractured chalk reservoir in the Norwegian sector of the North Sea which has been producing mainly under compaction and solution gas drive since 1982. Seawater injection in the crestal area started early 2006. Due to high porosity and low permeability the risk for chalk influx is high. It takes approximately one year from when a new well is put on production before it is fully open on the choke. It is also believed that the chalk has been weakened by compaction due to loss of cohesion.[7] The mitigation strategy to stop scale from forming on seawater breakthrough in the Valhall producers was based upon downhole scale inhibitor squeeze treatments. A scale inhibitor qualification program was put in place to find a non-damaging squeeze chemical that will stop the wells from scaling. The qualification program involved creep tests in a triaxial coreflood rig to monitor the chalk weakening effect, dynamic tube blocking tests and core flooding to test inhibitor performance. A robust analysis method for residual scale inhibitor based upon HPLC has also been developed.
It is well established that water itself will weaken the chalk significantly. A significant extra weakening effect was seen on the chalk when tested against traditional scale inhibitors. It is believed that the pH of the scale inhibitor has a significant contribution to the extra weakening seen, probably due to dissolution of the chalk. Non-aqueous versions have been lab tested without success due to high pressure build up during injection into the core. The water based scale inhibitor that was eventually chosen for field trial was a chemical that had a proven track record in chalk reservoirs and was pH neutralized, compatible with seawater and formation water and demonstrated good scale inhibition performance. The experience so far is that the chemical performs very well in terms of preventing scale from forming. The scale treatment itself increases the risk for chalk influx significantly due to the increased pore pressure in the influx area due to the pumping operation itself, the introduction of water and squeeze chemical and by rough opening of the well post squeeze treatment (needed to get the well back on production).
Improvement of Scale Management Using Analytical and Statistical Tools
Authors: Scheck Michael , Ross Gill 
Published: May 2008

Abstract
Scale formation in the near-wellbore area, the tubing and in topsides facilities is one of the major challenges associated with oil production and so must be managed. The objective of scale management is to maximise value with respect to the risks to production from scale, balanced against the cost, downtime and potential damage from any treatment. Chemical treatments to mitigate against scale and to dissolve scale are frequently applied and costly. Shell U.K. Limited Production Chemistry has applied two methods in order reach the goal of an optimised scale management system. These are Environmental Scanning Electron Microscopy/Energy Dispersive X-Ray (ESEM/EDX) and Principal Component Analysis (PCA).
ESEM/EDX can be used to determine if scale is actually formed in the well or near wellbore area. Several wells in a Shell field showed a decline in barium figures and consequently were considered to produce in a scaling regime. ESEM/EDX analysis clearly showed that there was no scale formation in the well or near wellbore area, enabling continued production and avoiding shutting in these wells.
Single ion analysis is often not accurate enough to demonstrate what is happening downhole, e.g. if seawater breakthrough (SWB) has occurred or not. PCA is a powerful tool with which one can resolve subtle yet significant changes in produced water and thus predict injection water breakthrough earlier and with higher accuracy. PCA was used in one case to prove that there was seawater breakthrough occurring in a well, although the reservoir model did not support this and single ion analysis did not give a clear message. The subsequently undertaken scale dissolver and scale squeeze not only saved the well from scaling up, but also led to a significant production gain. In another case it was possible to calculate if SWB had occurred or not much more accurately. Before the statistical analysis the suspicion was that 18 wells had undergone SWB and subsequently were treated with scale squeezes. With this analytical technique the number of wells thought to have SWB was reduced from 18 to 3 with 3 more where SWB is expected soon. Due to this, the amount of scale squeezes in one campaign was reduced from 18 to 6.
Shell U.K Limited's operations in the North Sea have benefited considerably from the use of PCA and ESEM/EDX.
Modelling the Impact of Diesel vs Water Overflush Fluids on Scale Squeeze Treatment Lives Using a Two-Phase Near-Wellbore Simulator
Authors: Vazquez O. , Mackay E. , Jordan Myles 
Published: May 2008

Abstract
This paper describes the development of a two-phase near-wellbore simulator to predict the impact on squeeze lifetime of the overflush fluid type. In the past, a single aqueous phase model was used for both brine and hydrocarbon overflush treatments. The new model enables a more accurate description of the displacement process if a hydrocarbon fluid (eg diesel) is used, and the impact on inhibitor transport through the formation and retention onto the rock matrix.
Field data is presented, with various treatments where either seawater or diesel are applied as displacement fluids being considered. In each case, the well was treated with the same aqueous scale inhibitor. The initial squeeze treatments used a diesel overflush. However, subsequent treatments utilised the same inhibitor but with seawater as the overflush fluid. It is clear from the field returns that the use of seawater rather than marine diesel improved chemical placement and extended treatment life. The theory behind this phenomenon is outlined, so allowing for more accurate treatment designs.
The process followed involved first deriving an isotherm using a single-phase squeeze model based on the water overflush treatment. This is the established conventional approach used in many hundreds of cases worldwide. This isotherm was then used to model the same treatment using the new two-phase model, which accounts for saturation changes during the treatment. A good match was achieved using the isotherm, giving confidence that the two models agree for purely aqueous treatments. A diesel overflush treatment was then simulated using the two phase model and the same isotherm, and again a good match was achieved. However, modelling the diesel overflush treatment in the single-phase model required a different isotherm to achieve the match. This clearly indicates that diesel overflush treatments may be accurately modelled using the two-phase model. Additional sensitivity calculations were performed to investigate the impact of splitting the overflush volume into separate diesel and water stages to improve well clean up while reducing the logistic challenges associated with pumping large volumes of diesel..
Ferrous Carbonate Nucleation and Inhibition
Authors: Yean Sujin , Al Saiari Hamad , Kan Amy T. , Tomson Mason B. 
Published: May 2008

Abstract
In this research, the nucleation kinetics and inhibition of ferrous carbonate (siderite) were investigated in a batch reactor under rigorously anoxic conditions in the absence of reducing agents. The nucleation kinetics of ferrous carbonate in 0.01 m NaCl solutions was measured from 25°C to 65°C at constant supersaturation. A decrease in temperature slows down ferrous carbonate nucleation rate. Similarly an increased ionic strength and a decreased saturation index result in a slower ferrous carbonate nucleation. Then, citrate and two common calcite (CaCO3) scale inhibitors such as phosphinopolycarboxylic acid (PPCA) and bis-hexamethylene triamine-penta(methylene phosphonic) acid (BHPMP) were examined in inhibition experiments. Our results reveal that common calcite scale inhibitors are not effective at preventing ferrous carbonate precipitation, whereas citrate is. The effectiveness of citrate as a ferrous carbonate nucleation inhibitor depends strongly temperature. This work suggests that citrate may have important implications in municipal, industrial, and natural waters in controlling ferrous concentrations.
First Application of Scale Inhibitor During Hydraulic Fracturing Treatments in Western Siberia
Authors: Cheremisov K. , Oussoltsev D. , Butula K. K. , Gaifullin Albert , Faizullin Ildar , Senchenko Dmitry 
Published: May 2008

Abstract
Problems related to inorganic scale precipitation are common in oil fields across Russia. The predominantly calcium carbonate scale rapidly precipitates from the produced water and causes reduction in reservoir permeability, restricts fluid flow in tubing and perforation, fails electric submersible and rod pumps, and plugs surface equipment. Local industry offers a number of inhibitors to prevent scale deposition. Although regular and planned injection of inhibitors into producing and injector wells is the most common method of scale precipitation prevention, no successful attempt to enhance scale prevention in conjunction with a stimulation treatment has been documented.
This paper describes the first application of a combined scale inhibitor and hydraulic fracturing treatment in Western Siberia. It allowed the operator to place significant amount of scale inhibitor within the propped fracture and into the adjacent formation. The case history delineates the detailed sampling and pretreatment analysis of several oil fields with high-water-cut wells. In some of the fields, as many as 26% of the production wells experience scale-related problems. Up to 33% of electrical submersible pumps (ESP) failures are related to inorganic scales. Further, the candidate selection process provided ground for detailed lab testing to optimize the inhibitor type and volumes required for the first scale-inhibited hydraulic fracturing application in the Novogodnee field.
The pilot project wells that were hydraulically fractured with the addition of scale inhibitor yielded a threefold increase in productivity and similar initial fluid production rates. The scale-inhibited wells did though provide sustained rates over a 3-month monitoring period compared to rapid decline in production on the non-inhibited wells. At the same time, the wells treated with scale inhibitor have provided not only sustained production but also a fourfold reduction in operating cost, confirming the success of the pilot project.
Diabetes, Fasting Glucose Levels, and Risk of Ischemic Stroke and Vascular Events
Authors: Boden-Albala Bernadette , Cammack Sam , Chong Ji , Wang Culing , Wright Clinton , Rundek Tatjana , Elkind Mitchell S.V. , Paik Myunghee C. , Sacco Ralph L. 
Published: May 2008

OBJECTIVE—There is insufficient randomized trial data to support evidence-based recommendations for tight control of fasting blood glucose (FBG) among diabetic subjects in primary stroke prevention. We explored the relationship between FBG among diabetic subjects and risk of ischemic stroke in a multiethnic prospective cohort.
RESEARCH DESIGN AND METHODS—Medical and social data and FBG values were collected for 3,298 stroke-free community residents: mean age ± SD was 69 ±10 years; 63% were women, 21% were white, 24% were black, and 53% were Hispanic; and follow-up was 6.5 years. Baseline FBG levels were categorized: 1) elevated FBG: history of diabetes and FBG ≥126 mg/dl (7.0 mmol/l); 2) target FBG: history of diabetes and FBG &lt;126 mg/dl (7.0 mmol/l); or 3) no diabetes/reference group. Cox models were used to calculate hazard ratios (HRs) and 95% CI for ischemic stroke and vascular events.
RESULTS—In the Northern Manhattan Study, 572 participants reported a history of diabetes and 59% (n = 338) had elevated FBG. Elevated FBG among diabetic subjects was associated with female sex (P &lt; 0.04), Medicaid (P = 0.01), or no insurance (P = 0.03). We detected 190 ischemic strokes and 585 vascular events. Diabetic subjects with elevated FBG (HR 2.7 [95% CI 2.0–3.8]) were at increased risk of stroke, but those with target FBG levels (1.2 [0.7–2.1]) were not, even after adjustment. A similar relationship existed for vascular events: elevated FBG (2.0 [1.6–2.5]) and target FBG (1.3 [0.9–1.8].
CONCLUSIONS—This prospective cohort study provides evidence for the benefits of tighter glucose control for primary stroke prevention.
Distinct Component Profiles and High Risk Among African Americans With Metabolic Syndrome
Authors: Taylor Herman , Liu Jiankang , Wilson Gregory , Golden Sherita H. , Crook Errol , Brunson Claude D. , Steffes Micheal , Johnson William D. , Sung Jung Hye 
Published: May 2008

OBJECTIVE—Health of African Americans is seriously threatened by unremitting epidemics of diabetes and cardiovascular disease (CVD). However, the role of metabolic syndrome in the African-American population has not been investigated widely. This study examined the prevalence of metabolic syndrome and assessed its cross-sectional relationship to CVD in the Jackson Heart Study (JHS) cohort.
RESEARCH DESIGN AND METHODS—A total of 5,302 participants aged ≥21 years who were recruited at baseline during 2000–2004 were analyzed for this study. Adjusted odds ratios (ORs) were estimated in a logistic regression analysis for coronary heart disease (CHD) and cerebrovascular disease (CBD) in those with and without coexisting metabolic syndrome. Diabetic participants were excluded.
RESULTS—Among those aged 35–84 years, metabolic syndrome prevalence was 43.3% in women and 32.7% in men. Elevated blood pressure (70.4%), abdominal obesity (64.6%), and low HDL cholesterol (37.2%) were highly prevalent among those with metabolic syndrome. Prevalence rates for CVD, CHD, and CBD were 12.8, 8.7, and 5.8%, respectively. After adjustment for age and sex, metabolic syndrome was associated with increased age- and sex-adjusted ORs for CVD (OR 1.7 [95% CI 1.4–2.1]), CHD (1.7 [1.4–2.2]), and CBD (1.7 [1.3–2.3]) compared with those without CVD, CHD, or CBD.
CONCLUSION—Metabolic syndrome prevalence in the JHS is among the highest reported for population-based cohorts worldwide and is significantly associated with increased ORs for CVD, CHD, and CBD. Abdominal obesity, increased blood pressure, and low HDL cholesterol (without triglyceride elevation) are surprisingly prominent. A high prevalence of low HDL emerges as a leading contributor to metabolic syndrome among African Americans in this large African-American cohort.
Rarefaction of the Peripheral Nerve Network in Diabetic Patients Is Associated With a Pronounced Reduction of Terminal Schwann Cells
Authors: Reinisch Christina M. , Traxler Hannes , Piringer Stefanie , Tangl Stefan , Nader Alexander , Tschachler Erwin 
Published: May 2008

OBJECTIVE—Peripheral neuropathy is the most frequent neurological complication in diabetic patients. The diagnosis is established by both clinical neurological examination and demonstration of reduced epidermal nerve fibers in skin biopsies (1). Whereas the decrease of free nerve endings has been extensively studied in diabetic patients (2,3), no data are available on possible changes of terminal Schwann cells. Besides their role as scaffold for peripheral nerves, they also play an important role in supporting survival and function of peripheral nerves (4).
RESEARCH DESIGN AND METHODS—We analyzed the subepidermal nerve plexus in dermal sheet preparations of deceased diabetic and nondiabetic patients by immunostaining for detection of the neural cell adhesion molecule and quantification of the subepidermal nerve plexus.
RESULTS AND CONCLUSIONS—The subepidermal nerve plexus, comprising nerve fibers and ensheathing Schwann cells, was significantly reduced in diabetic patients. Whether the reduction in terminal Schwann cells is cause or consequence of the loss of peripheral nerve fibers remains to be investigated.
Markers of Endothelial Dysfunction and Inflammation in Type 1 Diabetic Patients With or Without Diabetic Nephropathy Followed for 10 Years
Authors: Astrup Anne Sofie , Tarnow Lise , Pietraszek Lotte , Schalkwijk Casper G. , Stehouwer Coen D.A. , Parving Hans-Henrik , Rossing Peter 
Published: May 2008

OBJECTIVE—We evaluated the association of biomarkers of endothelial dysfunction and inflammation with all-cause mortality and cardiovascular mortality and morbidity and decline in glomerular filtration rate (GFR) in type 1 diabetic patients.
RESEARCH DESIGN AND METHODS—We prospectively followed 199 type 1 diabetic patients with diabetic nephropathy and 192 patients with persistent normoalbuminuria. Biomarkers were measured at baseline.
RESULTS—We constructed two Z scores: the mean inflammatory Z score combined C-reactive protein, interleukin-6, soluble intercellular adhesion molecule (sICAM-1), and secreted phospholipase A2 and the mean Z score for endothelial dysfunction combined soluble vascular cell adhesion molecule 1, plasminogen activator inhibitor-1, and sICAM-1. The mean Z score of inflammatory biomarkers was associated with mortality and the combined end point in patients with diabetic nephropathy after multivariate adjustment (hazard ratio 1.7 [95% CI 1.1–2.6]; P = 0.025 and 1.5 [1.1–2.2]; P = 0.017). The mean Z score for endothelial dysfunction biomarkers was associated with mortality in a model adjusting for age and sex in patients with diabetic nephropathy (1.6 [1.0–2.3]; P = 0.031). The mean Z score for endothelial dysfunction correlated with decline in GFR (r = −0.243; P = 0.001); the correlation persisted after multivariate adjustment (coefficient −1.38 [95% CI −2.27 to −0.50]; P = 0.002).
CONCLUSIONS—Mean Z scores of inflammatory biomarkers are significantly associated with all-cause mortality and cardiovascular morbidity and mortality in patients with nephropathy after multivariate adjustment. These data suggest that the high risk of cardiovascular disease in type 1 diabetes may be explained in part by inflammatory activity. Mean Z score of endothelial dysfunction correlated after multivariate adjustment with the rate of decline in GFR.