bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reservoir Modeling in Support of Shale Gas Exploration
Authors: Schepers K. C. , Gonzalez R. J. , Koperna G. J. , Oudinot A. Y. 
Published: May 2009

AbstractShale gas and other unconventional gas plays have become an important factor in the United States energy market, and are often referred to as statistical plays due to their high heterogeneity. They present real engineering challenges for characterization and exploitation, and their productivity depends upon an inter-related set of reservoir, completion and production characteristics.Shale gas plays are generally characterized by low geologic risk and a high commercial risk. Extensive and continuous deposits of tight, usually naturally-fractured shale provide the duality of a potentially-productive reservoir being the hydrocarbon source. Commercial production is a huge unknown in these plays, and reservoir modeling as well as production predictions involve considerable uncertainty. Because of the large number of unknowns, a merely deterministic approach is often incapable of capturing the complete impact of all interdependencies present in a shale gas resource play.Consequently, one must take into account multiple scenarios to find better exploitation plans. Tools are therefore needed to identify the most important geologic and engineering factors, and to quantify the range of variability in uncertain variables. Reservoir simulation coupled with stochastic methods, i.e., Monte Carlo and geostatistical procedures, have provided excellent means to predict production profiles with a wide variety of reservoir character and producing conditions.Defining and representing uncertainties with a quantitative understanding of their respective impacts on commercial achievability is crucial to subsequent decisions involving continued investment for commercial purposes.This paper describes a systematic process employed in the evaluation of a new prospect area (a shale gas play) with very limited available data. In order to properly model the problem with uncertainty, geological and engineering issues were framed within conventional Monte-Carlo procedures and geostatistical characterization algorithms to identify key production parameters so that relevant data can be collected. This process also allows for the investigation of how the combination of a nested natural fracture system, appropriate wellbore design and stimulation are necessary to drive productivity, and provide project results in terms of ranges of outcomes and associated probabilities. Consequently, managers can be in a better position to make informed decisions regarding the uncertainty of such projects.
Effect of Some Physicalchemical Variables on the Formation and Stability of Foam in an Oil-Air System and Their Correlation With the Formation of Foamy Crude Oil
Authors: Marcano L. , Gutierrez X. , Perez B. , Martínez E. 
Published: May 2009

Abstract
There are crude oil reservoirs, in Venezuela, where the foam generation or production combined with the crude oil has become a problem. Consequently the net volume of produced crude oil decreases and the problem is more severe in some reservoirs than in others. So far any effective techniques or methods have not been created in order to solve this problem. Neither there has been any systematic study which may explain why the foamy crude oil is produced, or why some foamy crude oil are more stable than others. The purpose of this paper was to find out the mechanism of formation and stabilization of the foam in the crude oil. The initial investigation was related to study a engine oil (Diesel)-air system which simulated the crude oil-gas system and the formation and stabilization variables, which affect the foam production. Finally the results were correlated with the crude oil-gas system, through exposition of hypothesis. Afterward we will work with the crude oil-gas systems. The method used to create or produce foam consisted in bubbling air in the engine oil phase containing surfactant, alcohol and water different concentrations. The tests basically were carried out to different air flow in order to determine the static stability or the lifetime of the foam produced. The foamability and stability foam were plotted as a function of the air flow. The results indicated that the foam production in the oil is not affected by the increase in the surfactant concentration, but it is improved with the increase of the dispersed water content in the oil. However, the favorable effect of the dispersed water on the foamability is related to the alcohol concentration dissolved in the oil. The most important conclusion is that the presence of dispersed water in the oil is responsible of the foam formation.
Definition of Reservoir Compartmentalization Applying Compositional Gradients: Mugrosa B Formation in Middle Magdalena Valley Basin, Lisama Field, Colombia
Authors: Castro R. H. , Canas-Marin W. , Osorio R. , Soto C. 
Published: May 2009

Abstract
Lisama is an oil field operated by ECOPETROL S.A. located in the east side of Middle Magdalena Valley basin in Colombia. The reservoir is a stratigraphic-structural combined trap and the oil comes from the Tertiary, mainly from the formations Mugrosa and Colorado.
A methodology of Integrated Fluid Analysis is applied. The methodology includes fluid sampling analysis, PVT test quality control and reservoir fluids representativeness. Then, a cubic Equation of State is developed to match the best PVT data. Finally, compositional gradients are built so that they can describe properly the variation of PVT properties with depth.
There are 16 PVT studies in Lisama Field. However, after applying the procedure described above, only the results from four PVT reports are found to be both reliable and representative. Afterwards, Peng-Robinson Equation of State is fitted against PVT depletion data applying a non linear regression technique in order to change systematically internal parameters of the equation of state such as binary interaction coefficients, critical pressures, critical temperatures, volume shifts, and critical Z factors. Finally, isothermal compositional gradients based on reliable compositions are built and a gas-oil contact (GOC) analysis is developed.
The results obtained by applying this methodology indicate that fluids in Lisama field's northwest sector, known as the Corridor of Gas, have a different behavior in comparison with those of the remaining area, particularly in relation to the location of the respective gas – oil contacts. That is, the two GOC values predicted for the fluid system in the Corridor of Gas are located within the Mugrosa formation, while the GOC value for the fluids of the remaining area are predicted out of this formation. Therefore, this would mean that the corridor of Gas is isolated from the rest of the Lisama area.
This study is a fundamental support for the initialization of the reservoir simulation model and the prediction of new development strategies that would lead to optimize the recovery of fluids in the area.
Improving MEOR Performance by a Selection Methodology in Mature Oilfields
Authors: Segovia G. C. , Huerta V. A. , Guitierrez G. C. 
Published: May 2009

Abstract
Microbial Enhanced Oil Recovery (MEOR) is a technique that uses bacterias and by-products, either as an organic formation damage removing mechanism to increase oil production, or as an agent to reduce residual oil saturation, and eventually increase ultimate recovery factor, specially in mature oilfields.
Successful applications reported in Argentina, United States, China and Venezuela were the main driving force to Peruvian local companies, which decided to implement some MEOR Projects in Talara oilfields, with positive and negative results. Consequently, it has been prepared a rigorous analytical and pragmatic methodology by integrating: Well Performance Evaluation, Reservoir Engineering Analysis, Physicochemical Characterization, Rheological Analysis and Sensitivity to Biotreatability Tests.
A flowchart including general criteria, as well as, fluid and reservoir properties application ranges was prepared to optimize oil wells and reservoirs selection to MEOR. This flow chart allowed us to recommend two wells of the MEOR pilot project recently implemented in a marginal oilfield of Talara, Peru; preliminary results showed in both wells, improvements in fluid properties (less oil viscosity and higher API°) and initial increase of more than 30% in oil production.
Unconventional Abandonment of Gavilan 1W Well
Authors: Lopez Davila A. M. , Farfan Collazos L. E. 
Published: May 2009

Abstract
Gavilan 1W Well was drilled in 1970 by Texas Petroleum, in Colombia, near to border's Ecuador. Final depth 7.700 ft. – 41 API, 1% BSW, Q = 25 BFPD. Well was closed, without conventional abandonment. In 2001, We identified an illegally exploited well with a gas leak from the wellhead (THP= 1.000 psi). Ecopetrol S.A. installed a clamp and control gas leak without exit in well control, in this place there is a permanent presence of guerrilla and there isn't road to arrive the location, we did all operations by Helicopter
In 2008, after Colombia Army's Operations, We found a crater near to wellhead, the well was in illegally exploited and the environment contaminated; after many operations with brines (plus sealant material), mud and cement, was possible seal leak's tubing-casing, and closed the crater
Water-Gas Migration Control and Mechanical Properties Comparison With a Quick-Setting Slurry Design QSSD to Be Applied in a Production Cementing Job for Ecuador
Authors: Ramirez H. B. , Santra A. , Martinez C. , Ramos X. 
Published: May 2009

Abstract
A slurry design based on Sorel cement technology with a median particle size of 5 to 10 microns has been optimized without using Portland cement. This mechanically modified slurry with quick-setting technology is designed to withstand the operational changes that may play a crucial role in the performance of the cement sheath once the well is drilled, completed, and in production. Two additional mechanically modified slurries were designed using local Class "G" cement for comparison.
The control of gas migration can be enhanced by obtaining a transition time value of less than 30 minutes. Transition time is defined as the length of time it takes for the static gel strength (SGS) to change from 100 lb/100 ft2 to 500 lb/100 ft2. The SGS tests were performed under simulated downhole pressure and temperature conditions. A value of 10 minutes for transition time was obtained. SGS tests were carried out with a static gel strength measuring device (SGSMD). It is important to mention that the zero gel time (ZGT), is defined as the amount of time the slurry can remain static after placement time and still transfer almost full hydrostatic-pressure from fluids before reaching an SGS of 100 lb/100 ft2; it can also be adjusted in regards to the cementing job.
The mechanical properties of this quick-setting slurry design (QSSD) were comparable and in some aspects were improved. The results included a Young's modulus around 5E+05-psi, Poisson ratio of 0.23, and a tensile strength of 250-psi. The bottomhole circulating temperature (BHCT) was 172°F and bottomhole static temperature (BHST) at MD was 208°F. Cylindrical samples were cured at 208°F and 2,000-psi for seven days and were used for measurement of mechanical properties.
This slurry design was developed for Ecuador to solve three major problems on production liners: Water-gas migration throughout the annulusLong waiting-on-cement time (WOC) to develop compressive strengthImprovement of the mechanical properties to minimize the effect of failure mechanisms on the cement (cracking, debonding, shear failure) that can result in poor cement bond logs and remedial cementing jobs
IPI Method: A Subsurface Approach to Understand and Manage Unfavorable Mobility Waterfloods
Authors: Elphick J. J. , Marquez L. J. , Amaya M. 
Published: May 2009

Abstract
Oil viscosities of about 2 cP and above (under downhole conditions) are common and often exhibit poor end-point mobility ratios when displaced by water in fields under waterflood or with active aquifers. This causes a triple hit on the recovery factor: Poor displacement efficiencyPoor areal sweepPoor vertical sweep
This is made worse by reservoir heterogeneity.
The commonly used concepts of productivity index (PI) and injectivity index (II) are not particularly useful when the mobility ratio is high since they require the use of a nominal drainage radius, whereas a two-fluid system with a moving fluid is more appropriate.
The novel concept of the injectivity productivity index (IPI) has been developed to consider a pair of wells comprising an injector and producer, and replaces the use of II and PI. The IPI method helps to quantify waterflood issues in the presence of poor mobility.
This paper will cover three main areas: The simple background theory of IPI.The consequences of IPI for breakthrough, sweep, and even sanding.The implication of IPI for an example waterflood field, Casabe, which has these challenges and required a new understanding of the waterflood.
Ultra-Low Invasion Fluids: A Viable Technical Solution to Drill in Eastern Venezuela
Authors: Arbizu A. G. , Reid P. , Moreno J. G. , Avila A. A. , Urbaneja N. 
Published: May 2009

Abstract
One of key tasks of he drilling fluids industry for many years has been to develop a fluid with as low invasion characteristics as possible. These are often referred to as low invasion or ultra-low invasion fluids. If we could sop invasion by the drilling fluid completely, it would be possible to eliminate several forms of wellbore instability, lost circulation and differential pressure sticking. In addition, well productivity improvements will be expected as there will be little or no formation damage from the drilling fluid. This scenario of zero invasion is not achievable with a fluid used in an overbalanced condition, at least not in the near future. However, the industry is working to understand the benefits of he next best thing: Ultra-Low Invasion Fluids (ULIF).
This paper presents the application of this technology to drill a development well in the San Joaquín field of Eastern Venezuela.
Numerical and Experimental Modeling of Relative Permeability in Heavy Oil Reservoirs
Authors: Castillo A. F. , Perez E. R. , Rojas J. A. , Zapata J. F. 
Published: May 2009

Abstract
Understanding of high viscous fluid flow in porous media is very important in the accurate development plan for heavy oil reservoirs. Viscous fingering and effects of unstable flow are phenomenon that must be considered during displacements of heavy oil by water in reservoirs.
Experimental problems in rock tests with high viscous fluids (due to exaggerated increases in pressure differential, early breakthrough times, large differences in mobility ratios) are some of the technical difficulties showed during the acquisition of relative permeability curves by unsteady state in heavy oil reservoirs. At the same way, difficulties in conventional interpretation (JBN interpretation is supposing uniform displacement) are challenges that numerical interpretations must be try to solve for modeling accurately what is happening inside rock.
This paper presents a number of "best practices" for defining a reliable relative permeability curve in heavy oil reservoirs related to numerical modeling and experimental modeling. Description of phenomenon in a Colombian heavy oil reservoir field are shown for three petrophysical quality rocks (less than 500 mD, around 5000 mD and larger than 10000 mD). Capillary pressure effects are included in the modeling and its importance in the displacement is analyzed.
Finally, results of sensibilities to different mobility ratios in crudes with different viscosities (5, 25, 100 and 1000 cp) are presented in the same group of rocks mentioned previously. The results of this study help to understand the influence of viscosity and its impact in total recovery.
Borel Reductibility and Classification of von Neumann Algebras
Authors: Sasyk Román , Törnquist Asger 
Published: June 2009

AbstractWe announce some new results regarding the classification problem for separable von Neumann algebras. Our results are obtained by applying the notion of Borel reducibility and Hjorth's theory of turbulence to the isomorphism relation for separable von Neumann algebras.
Degrees of rigidity for Souslin trees
Authors: Fuchs Gunter , Hamkins Joel David 
Published: June 2009

AbstractWe investigate various strong notions of rigidity for Souslin trees, separating them under ⟡ into a hierarchy. Applying our methods to the automorphism tower problem in group theory, we show under ⟡ that there is a group whose automorphism tower is highly malleable by forcing.
On bounded arithmetic augmented by the ability to count certain sets of primes
Authors: Woods Alan R. , Cornaros Ch. 
Published: June 2009

AbstractOver 25 years ago, the first author conjectured in [15] that the existence of arbitrarily large primes is provable from the axioms IΔ0(π) + def(π), where π(x) is the number of primes not exceeding x, IΔ0(π) denotes the theory of Δ0 induction for the language of arithmetic including the new function symbol π, and def(π) is an axiom expressing the usual recursive definition of π. We prove a modified version in which π is replaced by a more general function ξ that counts some of the primes below x (which primes depends on the values of parameters in ξ), and has the property that π is provably Δ0(ξ) definable.
Low upper bounds of ideals
Authors: Kučera Antonín , Slaman Theodore A. 
Published: June 2009

AbstractWe show that there is a lowT-upper bound for the class ofK-trivial sets, namely those which are weak from the point of view of algorithmic randomness. This result is a special case of a more general characterization of ideals inT-degrees for which there is a lowT-upper bound.
Biphasic Insulin Aspart 30/70: Pharmacokinetics and Pharmacodynamics Compared With Once-Daily Biphasic Human Insulin and Basal-Bolus Therapy
Authors: Heise Tim , Heinemann Lutz , Hövelmann Ulrike , Brauns Bianca , Nosek Leszek , Haahr Hanne L. , Olsen Klaus J. 
Published: June 2009

OBJECTIVE
Pharmacological profiles of biphasic insulin aspart 30/70 (BIAsp 30) once daily (OD), twice daily (b.i.d.), and three times daily (t.i.d.) were compared with other insulin regimens in two crossover glucose clamp studies of insulin-treated type 2 diabetic patients.

RESEARCH DESIGNS AND METHODS
Study 1 consisted of BIAsp 30 OD, b.i.d., and t.i.d. versus biphasic human insulin 30/70 (BHI 30), OD (n = 24). Study 2 examined BIAsp 30 t.i.d. versus basal-bolus therapy (insulin glargine OD plus insulin glulisine t.i.d.) (n = 24). Pharmacokinetics/pharmacodynamics (PK/PD) were investigated over 24 h.

RESULTS
Study 1: PK and PD were markedly different between BIAsp 30 OD and BHI 30 OD: the maximum insulin concentration and glucose infusion rate (GIR) were higher for BIAsp 30; time to maximum metabolism was 1.7 h sooner for BIAsp 30. Study 2: both regimens showed three distinct prandial-related GIR peaks. GIR 24-h area under the curve for BIAsp t.i.d. was higher than for basal-bolus therapy: 2,585.2 vs. 2,289.2 mg/kg.

CONCLUSIONS
BIAsp had pharmacological advantages over BHI. BIAsp t.i.d. had a similar PD profile to basal-bolus therapy.
Hypoglycemia Unawareness in Older Compared With Middle-Aged Patients With Type 2 Diabetes
Authors: Bremer Jan P. , Jauch-Chara Kamila , Hallschmid Manfred , Schmid Sebastian , Schultes Bernd 
Published: June 2009

OBJECTIVE
Older patients with type 2 diabetes are at a particularly high risk for severe hypoglycemic episodes, and experimental studies in healthy subjects hint at a reduced awareness of hypoglycemia in aged humans. However, subjective responses to hypoglycemia have rarely been assessed in older type 2 diabetic patients.

RESEARCH DESIGN AND METHODS
We tested hormonal, subjective, and cognitive responses (reaction time) to 30-min steady-state hypoglycemia at a level of 2.8 mmol/l in 13 older (≥65 years) and 13 middle-aged (39–64 years) type 2 diabetic patients.

RESULTS
Hormonal counterregulatory responses to hypoglycemia did not differ between older and middle-aged patients. In contrast, middle-aged patients showed a pronounced increase in autonomic and neuroglycopenic symptom scores at the end of the hypoglycemic plateau that was not observed in older patients (both P &lt; 0.01). Also, seven middle-aged patients, but only one older participant, correctly estimated their blood glucose concentration to be &lt;3.3 mmol/l during hypoglycemia (P = 0.011). A profound prolongation of reaction times induced by hypoglycemia in both groups persisted even after 30 min of subsequent euglycemia.

CONCLUSIONS
Our data indicate marked subjective unawareness of hypoglycemia in older type 2 diabetic patients that does not depend on altered neuroendocrine counterregulation and may contribute to the increased probability of severe hypoglycemia frequently reported in these patients. The joint occurrence of hypoglycemia unawareness and deteriorated cognitive function is a critical factor to be carefully considered in the treatment of older patients.
Adherence to the DASH Diet Is Inversely Associated With Incidence of Type 2 Diabetes: The Insulin Resistance Atherosclerosis Study
Authors: Liese Angela D. , Nichols Michele , Sun Xuezheng , D'Agostino Ralph B. , Haffner Steven M. 
Published: June 2009

OBJECTIVE
The Dietary Approaches to Stop Hypertension (DASH) diet has been widely promoted; however, little is known about its impact on type 2 diabetes.

RESEARCH DESIGN AND METHODS
We evaluated the association of the DASH diet with incidence of type 2 diabetes among 862 participants of the Insulin Resistance Atherosclerosis Study (IRAS) who completed a 1-year food frequency questionnaire at baseline. Type 2 diabetes odds ratios (ORs) were estimated at tertiles of the DASH score.

RESULTS
An inverse association was observed in whites (tertile 2 vs. tertile 1, OR 0.66 [95% CI 0.29–1.48]) that became significant for the most extreme contrast (tertile 3 vs. tertile 1, 0.31 [0.13–0.75]), with adjustment for covariates. No association was observed in blacks or Hispanics (tertile 2 vs. tertile 1, 1.16 [0.61–2.18 ]; tertile 3 vs. tertile 1, 1.34 [0.70–2.58 ]).

CONCLUSIONS
Adherence to the DASH dietary pattern, which is rich in vegetables, fruit, and low-fat dairy products, may have the potential to prevent type 2 diabetes.
Changes in Basal Insulin Infusion Rates With Subcutaneous Insulin Infusion
Authors: Heinemann Lutz , Nosek Leszek , Kapitza Christoph , Schweitzer Matthias-Axel , Krinelke Lars 
Published: June 2009

OBJECTIVE
Evaluation of the time required until a change in the basal insulin infusion rate with an insulin pump induces subsequent changes in the metabolic effect.

RESEARCH DESIGN AND METHODS
In this euglycemic glucose clamp study, 10 male subjects with type 1 diabetes received three different subcutaneous insulin infusion rates (0.5, 1.0, and 2.0 units/h; for 4 h each) of insulin lispro (IL) with insulin pumps.

RESULTS
An increase in insulinemia occurred within 15–30 min after changing the infusion rate. While the serum IL levels reached a steady state at the end of the infusion period, the glucose infusion rates did not always reach steady-state levels with the higher infusion rates. However, an increase in the glucose consumption occurred within 30–60 min after switching the infusion rate.

CONCLUSIONS
Several hours are required until a new steady state in the metabolic effect is achieved after a significant change in basal insulin infusion.