bluuebunny/crossref_metadata_2025_split huggingface dataset:
Permeability of Laboratory-Formed Methane-Hydrate-Bearing Sand: Measurements and Observations Using X-Ray Computed Tomography
Authors: Kneafsey Timothy J. , Seol Yongkoo , Gupta Arvind , Tomutsa Liviu 
Published: October 2010

Summary
Methane hydrate was formed in two moist sands and a sand/silt mixture under a confining stress in an X-ray-transparent pressure vessel. Three initial water saturations were used to form three different methane-hydrate saturations in each medium. X-ray computed tomography (CT) was used to observe location-specific density changes caused by hydrate formation and flowing water. Gas-permeability measurements in each test for the dry, moist, frozen, and hydrate-bearing states are presented. As expected, the effective permeabilities (intrinsic permeability of the medium multiplied by the relative permeability) of the moist sands decreased with increasing moisture content. In a series of tests on a single sample, the effective permeability typically decreased as the pore space became more filled in the order of dry, moist, frozen, and hydrate-bearing. In each test, water was flowed through the hydrate-bearing medium and we observed the location-specific changes in water saturation using CT scanning. We compared our data to a number of models, and our relative permeability data compare most favorably with models in which hydrate occupies the pore bodies rather than the pore throats. Inverse modeling (using the data collected from the tests) will be performed to extend the relative permeability measurements.
Characterizing Natural-Fracture Permeability From Mud-Loss Data
Authors: Huang Jinsong , Griffiths D. V. , Wong Sau-Wai 
Published: October 2010

Summary
Liétard et al. (1999, 2002) have provided important insight into the mechanism and prediction of transient-state radial mud invasion in the near-wellbore region. They provided type curves describing mud-loss volume vs. time that allow the hydraulic width of natural fractures to be estimated through a curve-matching technique. This paper describes a simpler and more direct method for estimating the hydraulic width by the solution of a cubic equation, with input parameters given by the well radius rw, the overpressure ratio Δp/τy, and the maximum mud loss volume (Vm)max.
A New Method To Predict Performance of Horizontal and Multilateral Wells
Authors: Tabatabaei M.. , Ghalambor A.. 
Published: October 2010

Summary
Production enhancement and ultimate recovery improvement have given horizontal wells the edge over vertical wells in many marginal reservoirs. However, it is more expensive to drill and complete a horizontal well than a vertical one. Therefore, to determine the economical feasibility of drilling a horizontal well, engineers need reliable methods to estimate its productivity.
After a broad literature review, a simple semianalytical model has been developed in this study for predicting the productivity of horizontal oil wells. This model couples flow from a box-shaped drainage volume to flow in the wellbore. Along with friction, acceleration, and fluid-inflow effect, change in flow regime from laminar to turbulent is also taken into account to describe flow in the wellbore. The reservoir-inflow model used in this productivity model represents flow in the reservoir using a combination of 1D and 2D models and also considers varying skin along the wellbore to account for the heterogeneity of the near-wellbore region because of drilling-fluid invasion into the formation. In addition, reservoir-permeability anisotropy and convergence of flow to the wellbore have been taken into account in this inflow model. Comparison of this model with three existing models using field data reveals that the proposed model is more accurate because of more-realistic modeling of reservoir inflow and wellbore flow.
The semianalytical nature of this coupling model makes it comprehensive and applicable to reservoirs with varying conditions, especially heterogeneous reservoirs. Moreover, this productivity model can be extended easily to estimate the deliverability of multilateral wells by coupling the inflow performance of individual laterals with hydraulics in buildup sections and the main vertical section. A logical procedure for calculating the deliverability of multilateral wells by using this productivity model is described in this paper.
Inhibition of Calcium Sulfate and Strontium Sulfate Scale in Waterflood
Authors: BinMerdhah Amer Badr 
Published: October 2010

Summary
One of the most common methods of preventing downhole and topside mineral-scale formation in oil fields is through the use of chemical-scale inhibitors. Several aspects of the brine composition may affect the performance of the various scale inhibitors used in oilfield applications. This study was conducted to investigate the permeability reduction caused by deposition of calcium sulfate (CaSO4) and strontium sulfate (SrSO4) in Malaysian sandstone and Berea cores from mixing injected Malaysian seawaters (SW) (Angsi and Barton) and formation water (FW) that contain a high concentration of calcium and strontium ions at various temperatures (50 to 95°C) and differential pressures (75 to 200 psig). Scale-inhibition efficiency was determined in both the bulk jar and the core tests by using scale inhibitors methylene phosphonic acid (DETPMP), polyphosphino carboxylic acid (PPCA), and phosphorus-based scale inhibitor (PBSI) at various temperatures (50 to 95°C) and concentrations. The results showed a large extent of permeability damage caused by calcium and strontium sulfates that deposited on the rock pore surface. At higher temperatures, the rate of CaSO4 and SrSO4 precipitation increases because the solubilities of CaSO4 and SrSO4 scales decrease with increasing temperature. At 90°C temperature, PBSI was the best inhibitor because it reduced more scale deposition compared to the DETPMP and PPCA inhibitors.
A Mathematical Improvement to SAGD Using Geomechanical Modelling
Authors: Azad A. , Chalaturnyk R.J. 
Published: October 2010

Summary
Steam assisted gravity drainage (SAGD) is a thermal oil recovery technique which has been used mostly for Alberta's unconventional oil sands reservoirs. Roger Butler, known as the father of SAGD, was the first one to establish a theory and an analytical model for SAGD. His model is a rigorous solution and is widely referred to as a SAGD fast flow simulator. However, geomechanics, which has been shown to be a relevant part of SAGD's physics, has not been included in the model. When rock properties are influenced by geomechanical behaviour, the Butler theory is not able to capture the complete physics of the SAGD process. In such cases, the model must adopt unrealistic or high values for rock properties.
In this study, a classical theory in the field of geotechnical engineering (limit equilibrium) is employed to act as the geomechanical module for SAGD's mathematical coupled simulation. The Butler/Reis model has also been improved using a model of slices for flow simulation. Methodology of combining these two models in a single coupled mathematical simulator is presented in this paper. The solver is a fast and realistic proxy and can be used as a low-order tool for history matching. The results of coupled simulations show that the model is able to predict permeability and porosity of the reservoir closer to real values than uncoupled (flow only) modelling.
Calculation of Permeability Tensors for Unstructured Gridblocks
Authors: Hassanpour R.M. , Manchuk J.G. , Leuangthong O. , Deutsch C.V. 
Published: October 2010

Summary
Geostatistical models of reservoir properties are high resolution with many grid cells; it is impractical to use them directly in flow simulation because of computational costs. Upscaling techniques are applied to average small-scale permeability values to larger flow simulation blocks. In cases where unstructured grids are used or the geological features inside the gridblock are not aligned with the block geometry, symmetric or full-permeability tensors arise instead of a simple diagonal tensor. A method is presented to calculate the permeability tensor for an unstructured gridblock to account for the small-scale heterogeneity information inside the gridblock. Single-phase flow-based upscaling is performed based on random boundary conditions and the effective tensor permeability is found through an optimization technique. Full, symmetric and diagonal permeability tensors are calculated for 2D and 3D blocks and sensitivity analysis is performed.
A 3D Analytical Model for Wellbore Friction
Authors: Aadnoy Bernt S. , Fazaelizadeh Mohammad , Hareland Geir 
Published: October 2010

Summary
This paper presents a new friction model for application in petroleum wells. Although very simple, it applies for all wellbore shapes such as straight sections, drop-off bends, build-up bends, side bends or a combination of these. The drillstring is modelled as a soft string. In high tension the string weight is negligible as compared to the tension. This leads to simplified equations where the friction caused by the weight is negligible. For this case the friction in a bend is formulated in terms of the 3D dogleg. The same model therefore applies for 2D and 3D wellbores.
The entire well can be modelled by two sets of equations, one for straight wellbore sections and one for curved wellbores. The latter is based on the absolute directional change, or the dogleg of the wellbore.
Three worked examples are given in the paper: a 2D well, a 3D well and combined hoisting and rotation in the 3D well.
One main purpose of this paper is to provide a simple explicit tool to model and to study friction throughout the well by separating gravitational and tensional friction effects.
Improved Drilling Efficiency Technique Using Integrated PDM and PDC Bit Parameters
Authors: Motahhari H.R. , Hareland G. , James J.A. 
Published: October 2010

Summary
In this paper, a new drilling optimization procedure is presented that is designed to improve the drilling efficiency with positive displacement motors (PDMs) and PDC bits. This developed optimization method is based on predicting rate of penetration (ROP) from PDM outputs for any PDC bit design. More specifically, optimization is done for a hole section and optimum values of weight on bit (WOB) and surface RPM are obtained for the section. For given flow rates, estimated values of optimum WOB and surface RPM are used to calculate the corresponding motor differential pressures and the foot by foot ROP values. Also, the method is used to show how improper operational parameter selection can affect total drilling time. A case study was done to consider different PDMs with different lobe configurations and a set of fixed operational parameters.
The presented method is verified by generating a confined rock strength log based on drilling data for a previously drilled well in Alberta. This foot-by-foot strength log is compared to a confined rock strength log generated as a follow-up analysis by a commercially available drilling simulator package. Also, a PDM differential pressure log is generated and compared to field-recorded on-bottom differential pressure values.
The method's application is best demonstrated by simulating the drilling operation of the Alberta well with three different PDMs. It is shown that consideration of PDM performance/selection in the drilling planning phase will help to perform a safe and cost-effective operation by preventing motor stalls and maintaining highest average ROP for the section. It is also shown that by optimizing WOB and surface RPM values for a constant mud flow rate and predefined bit wear at total depth, a maximum average ROP for the section can be reached for any PDM.
Experimental Study of Stability and Integrity of Cement in Wellbores Used for CO2 Storage
Authors: Tarco Jose C. , Asghari Karoosh 
Published: October 2010

Summary
This paper examines the results obtained from several sets of experimental work conducted on cement deterioration in environments similar to those found in CO2 injection and storage projects.
In order to investigate various changes in macroscopic and microscopic properties and behaviour of cement in presence of sulphate ions and CO2, several sets of experiments were conducted.
The study consisted of preparing and investigating the behaviour of several hundred samples of cement in presence of various concentrations of sulphate, from 0.1 wt% up to 6%, as well as CO2 at 15160 kPa and 55ºC. The effect of sulphate ions on cement was studied at 30ºC, 55ºC and 75º C. The two common classes of cement of Type 10 and Class G were tested during this study. A total of 300 identical cubic and 400 identical cylindrical samples were tested. The change in permeability, compressive strength, and shear and hydraulic bonding strength for these samples were monitored after 2, 4, 6, 8, 10 and 12 months.
Laboratory results showed that sulphate ions and CO2 improve the performance of cement during the first few months. However, the effect is reversed under prolonged experiments. The highest reduction in performance was observed for hydraulic shear bonding, which indicates that the highest risk of CO2 leakage is through pathways between the cement and casing.
Scaling Analysis of Wells With Downhole Water Loop Completion for Bottomwater Control
Authors: Jin Lu , Wojtanowicz Andrew Krzysztof , Afonja Gbolahan , Li Wenjing 
Published: October 2010

Summary
The theoretical paper presents development and verification of dimensionless groups describing a novel "smart?? well completion with downhole water loop (DWL) that stimulates wells affected by water coning. A well producing from an oil reservoir with bottomwater coning is completed at the top of oil for oil inflow and lifting, below the oil/water contact (OWC) for water drainage and deeper in the same aquifer for water injection. The two lower completions are hydraulically isolated from the top completion and work as a "water loop?? by draining the water to control OWC deformation (water cone) and injecting the drained water into the same aquifer. To date, computer simulations and field trials have shown that the wells with bottomwater drainage would produce more oil, and sooner, by removing water invasion to the oil-producing completion. However, addition of the water injection component makes the well's completion more complex and controlled by a multitude of well system parameters and reservoir and fluid properties. Therefore, dimensionless analysis is needed to simplify the system's description using only few dimensionless groups.
The study employs the inspectional analysis (IA) method to confirm known and define new dimensionless groups specific for DWL wells. Then, the resulting cluster of dimensionless groups has been reduced by verifying the groups for redundancy and interdependence.
Further reduction of the number of groups - from 14 to seven - has been accomplished by testing sensitivity of the recovery factor to the groups. Of the final seven, four dimensionless groups uniquely describe the DWL system.
Continuous Flow Peritoneal Dialysis
Authors: Raaijmakers Renske , Schröder Cornelis H. , Gajjar Priya , Argent Andrew , Nourse Peter 
Published: October 2010

Summary

Background and objectives
Acute renal failure can be treated with different dialysis modalities, depending on patient characteristics and hospital resources. Peritoneal dialysis (PD) can be first choice in situations like hypotension, disturbed coagulation, or difficult venous access. The main disadvantage of PD is the relatively limited efficacy. The aim of this study was to investigate whether continuous flow peritoneal dialysis (CFPD) is a more effective treatment than conventional PD in acute renal failure.

Design, setting, participants, & measurements
A pilot study was performed at The Red Cross University Hospital in Cape Town in six patients. Patients were treated with both CFPD and conventional PD for 8 to 16 hours. CFPD was performed with two bedside-placed catheters. After initial filling, dialysate flow rate (100 ml/1.73 m2 per minute) was maintained with an adapted continuous venovenous hemofiltration machine. Ultrafiltration flow rate was set at 2.5 ml/1.73 m2 per minute.

Results
Mean ultrafiltration was 0.20 ml/1.73 m2 per minute with conventional PD versus 1.8 ml/1.73 m2 per minute with CFPD. Mean clearances of urea and creatinine were 5.0 and 7.6 ml/1.73 m2 per minute with conventional PD versus 15.0 and 28.8 ml/1.73 m2 per minute with CFPD, respectively. No complications occurred.

Conclusions
In this first report of CFPD in six pediatric patients with acute renal failure, CFPD was on average three to five times more effective for urea and creatinine clearance and ultrafiltration than conventional PD, without any complications observed. CFPD has the ability to improve therapy for acute renal failure .
Effects of Dietary Phosphate and Calcium Intake on Fibroblast Growth Factor-23
Authors: Vervloet Marc G. , van Ittersum Frans J. , Büttler Rahel M. , Heijboer Annemieke C. , Blankenstein Marinus A. , ter Wee Piet M. 
Published: October 2010

Summary

Background and objectives
Little is known about the influence of dietary phosphate intake on fibroblast growth factor-23 (FGF23) and its subsequent effects on vitamin D levels. This study addresses changes in intact FGF23 (iFGF23) and C-terminal FGF23 (cFGF23), phosphaturia, and levels of vitamin D on high and low phosphate and calcium intake.

Design, setting, participants, & measurements
Ten healthy subjects adhered to a diet low or high in phosphate and calcium content for 36 hours each with a 1-week interval during which subjects adhered to their usual diet. Serum phosphate, calcium, vitamin D metabolites, parathyroid hormone (PTH), and FGF23 levels (cFGF23 and iFGF23) were measured several times a day. Phosphate, calcium, and creatinine excretion was measured in 24-hour urine on all study days.

Results
Serum phosphate levels and urinary phosphate increased during high dietary phosphate intake (from 1.11 to 1.32 mmol/L, P < 0.0001 and 21.6 to 28.8 mmol/d, P = 0.0005, respectively). FGF23 serum levels increased during high dietary phosphate/calcium intake (cFGF23 from 60 to 72 RU/ml, P < 0.001; iFGF23 from 33 to 37 ng/L, P = 0.003), whereas PTH declined. 1,25-Dihydroxyvitamin D (1,25D) showed an inverse relation with FGF23.

Conclusions
Variation in dietary phosphate and calcium intake induces changes in FGF23 (on top of a circadian rhythm) and 1,25D blood levels as well as in urinary phosphate excretion. These changes are detectable the day after the change in the phosphate content of meals. Higher FGF23 levels are associated with phosphaturia and a decline in 1,25D levels.
The Association between Abnormal Birth History and Growth in Children with CKD
Authors: Greenbaum Larry A. , Muñoz Alvaro , Schneider Michael F. , Kaskel Frederick J. , Askenazi David J. , Jenkins Randall , Hotchkiss Hilary , Moxey-Mims Marva , Furth Susan L. , Warady Bradley A. 
Published: October 2010

Summary

Background and objectives
Poor linear growth is a well described complication of chronic kidney disease (CKD). This study evaluated whether abnormal birth history defined by low birth weight (LBW; <2500 g), prematurity (gestational age <36 weeks), small for gestational age (SGA; birth weight <10th percentile for gestational age), or intensive care unit (ICU) at birth were risk factors for poor growth outcomes in children with CKD.

Design, setting, participants, & measurements
Growth outcomes were quantified by age-sex-specific height and weight z-scores during 1393 visits from 426 participants of the Chronic Kidney Disease in Children Study, an observational cohort of children with CKD. Median baseline GFR was 42.9 ml/min per 1.73 m2, 21% had a glomerular diagnosis, and 52% had CKD for ≥90% of their lifetime.

Results
A high prevalence of LBW (17%), SGA (14%), prematurity (12%), and ICU after delivery (40%) was observed. Multivariate analyses demonstrated a negative effect of LBW (−0.43 ± 0.14; P < 0.01 for height and −0.37 ± 0.16; P = 0.02 for weight) and of SGA (−0.29 ± 0.16; P = 0.07 for height and −0.41 ± 0.19; P = 0.03 for weight) on current height and weight. In children with glomerular versus nonglomerular diagnoses, the effect of SGA (−1.08 versus −0.18; P = 0.029) on attained weight was more pronounced in children with a glomerular diagnosis.

Conclusions
LBW and SGA are novel risk factors for short stature and lower weight percentiles in children with mild to moderate CKD independent of kidney function.
Construct Validity of the Assessment of Balance in Children Who Are Developing Typically and in Children With Hearing Impairments
Authors: De Kegel Alexandra , Dhooge Inge , Peersman Wim , Rijckaert Johan , Baetens Tina , Cambier Dirk , Van Waelvelde Hilde 
Published: October 2010

BackgroundChildren with hearing impairments have a higher risk for deficits in balance and gross motor skills compared with children who are developing typically. As balance is a fundamental ability for the motor development of children, a valid and reliable assessment to identify weaknesses in balance is crucial.ObjectiveThe purpose of this study was to investigate the construct validity of posturography and clinical balance tests in children with hearing impairments and in children who are developing typically.MethodsThe study involved 53 children with typical development and 23 children with hearing impairments who were between 6 and 12 years of age and without neuromotor or orthopedic disorders. All participants completed 3 posturography tests (modified Clinical Test of Sensory Interaction of Balance [mCTSIB], unilateral stance, and tandem stance) and 4 clinical balance tests (one-leg stance with eyes open and with eyes closed, balance beam walking, and one-leg hopping).ResultsThree conditions of the mCTSIB, unilateral stance, and 2 clinical balance tests were able to distinguish significantly between the 2 groups. Children with hearing impairments showed more difficulties in balance tasks compared with children who were developing typically when 1 or 2 types of sensory information were eliminated or disturbed. The study showed only low to moderate correlations among the different methods of evaluating balance.ConclusionsClinical balance tests and posturography offer different but complementary information. An assessment protocol for balance consisting of posturography and clinical balance tasks is proposed. Static and dynamic balance abilities could not be differentiated and seem not to be a valid dichotomy.