bluuebunny/crossref_metadata_2025_split huggingface dataset:
Computation of Test Area of Investigation in Nonradial Geometries
Authors: Ehlig-Economides C. A. 
Published: December 2007

ABSTRACT
Average pressure and permeability values from formation and well tests apply within the area or volume investigated. To integrate these measurements with each other and with other measurements sensitive to permeability and reservoir heterogeneity, it is essential to understand where these values are meaningful. From the practical point of view, the pressure gauge sensitivity is also a consideration.
The conventional approach for a well test is computation of the test radius of investigation. This technique has no application for tests that terminate in a nonradial geometry. Field data that have been published illustrate tests that have terminated in spherical flow (partially completed well), linear or bilinear flow (hydraulically fractured or horizontal well), pseudoradial flow (hydraulically fractured or horizontal well, well near a linear boundary), linear flow (well in elongated reservoir), and pseudosteady state flow. The test radius of investigation concept is equally unworkable for formation tests.
Simple formulas extend the concept of test radius of investigation to nonradial flow geometries. This approach permits meaningful integration of transient test interpretation results (permeability and average pressure estimates, and characterization of inner and outer boundary geometries) in reservoir characterization and in well productivity evaluation.
Current Water-Control Treatment Designs
Authors: Dahl J. A. , Nguyen P. D. , Dalrymple E. D. , Rahimi A. B. 
Published: December 2007

ABSTRACTDespite significant improvements in completion technology, water production problems associated with encroachment, channeling, and coning still prevail in' many wells. In this paper, different types of water-producing wells are classified corresponding to their onset mechanisms. Various applications of polymers and cements in minimizing water-oil ratio are reviewed. Methods and limitations of current water control processes are evaluated. A general procedure for designing water-control treatments is presented. This paper also addresses difficulties existing in design and performance of water-control treatments. These include (1) lack of an extensive production history and knowledge of prior stimulation of wells requiring treatment, (2) lack of a systematic approach in treatment design, and (3) improper recovery techniques when returning the well to production. Results of wells treated in various fields are evaluated with respect to methods and chemicals used.Information presented in this paper will provide the completion engineer a broad knowledge of water-control treatment design parameters and chemical applications currently available within the industry.
Influence of Liquid Hydrocarbons on Gas Hydrate Equilibrium
Authors: Becke Peter , Kessel Dagobert , Rahimian Iradj 
Published: December 2007

ABSTRACT
Experimental investigations on hydrate equilibrium conditions in multiphase mixtures incorporating a gas phase, a liquid hydrocarbon (LHC) phase and an excess water phase were performed. Measurements were conducted in a stirred autoclave at pressures up to 12 MPa and a temperature range of 275 to 295 K.
The gas phase consisted of both pure hydrocarbon gases (methane, ethane and propane) and their mixtures. The LHC phase consisted of pure alkanes, cyclo-alkanes, aromatics, their mixtures, and crude oils. In some experiments methanol was added as hydrate inhibitor. The measurements were performed in the hydrate decomposition mode. They aimed at obtaining data for estimating the influence of crude oils on hydrate equilibrium, and at determining their impact on the inhibiting effect of methanol.
For a constant pressure the presence of liquid hydrocarbons leads to decreasing the onset temperature of hydrate decomposition. Generally, their influence on pure gases is insignificant while it is severe on gas mixtures. The equilibrium temperature reduction increases with decreasing molecular weight and with increasing volume of the liquid hydrocarbons. Some cyclo-alkanes were incorporated into the hydrate structure. The inhibition with methanol is not influenced by any of the liquid hydrocarbons; the temperature depression appears to be additive. These findings are interpreted to depend on the preferential solubility of ethane and propane in the oil phase.
Methods and Results of Risk Assessment for Sour Gas Production Systems
Authors: Fischer Franz 
Published: December 2007

Abstract
In view of the toxic effects of hydrogen sulphide sour gas production systems must be carefully installed and safely operated. Investigation and assessment of greatest possible – although rare-accidents, such as a well blowout or a pipeline rupture, are necessary for the determination of safe distances and selection of appropriate measures for the minimization of potential effects. The calculation methods applied as well as the computer models used and the results obtained are described.
A General Solution of Gas/Water Coning Problem for Horizontal Wells
Authors: Guo Boyuh , Molinard J-E. , Lee R. L. 
Published: December 2007

ABSTRACT
Development of horizontal well technology offers a new approach to reducing gas/water coning effect during oil production. However, further improvement of the oil production rate of horizontal wells is still limited by the encroachment of the water cone when bottom water exists. This paper provides reservoir engineers with a general solution of the gas/water coning problem for horizontal wells. The objectives of this investigation include: (1) to determine the location of the stable water/gas cone, (2) to estimate the critical oil production rate, and (3) to find out the optimum placement of the horizontal wellbore so that the maximum critical oil rate can be obtained.
Using conformal mapping method, the location of the stable water/gas cone is determined as a function of oil rate and wellbore location. The critical oil rate is estimated by examining the profile development of the stable cone. It is found that the critical rate is directly proportional to the effective permeability (kh kv), thickness of the oil reservoir, and density contrast between oil and the coning fluid, and inversely proportional to the oil viscosity. The critical oil rate also depends upon the wellbore location in the oil reservoir and takes its maximum value when the horizontal wellbore is placed at about 70 % of reservoir thickness from the unwanted fluid.
Modified Methods for the Determination of Polyacrylic/Phosphinopolycarboxylic Acid and Polyvinylsulphonic Acid Scale Inhibitors in Oilfield Brines
Authors: McTeir M. D. K. , Ravenscroft P. D. , Rudkin Christopher 
Published: December 2007

ABSTRACT
The use of squeeze treatments to deploy scale inhibitors requires accurate determination of inhibitor concentrations in the returned fluids. This information is used, in conjunction with water chemistry and production data, to determine when to re-squeeze a well. In addition, with tightening environmental legislation becoming more probable, the concentration of production chemicals (including scale inhibitors) which are disposed of in produced waters need to be closely monitored. Current analysis techniques, especially for polymers, have proved problematic in field situations. Two spectrophotometric methods have been modified to analyse for polyacrylic acid, polyvinylsulphonic acid and phosphinopolycarboxylic acid scale inhibitors. The improved techniques have been tested in real oilfield brines and are simple, rapid, reliable and sensitive at the low concentrations found in oilfield situations.
Mathematical Model for the Scale-Inhibitor Squeeze Process Based on the Langmuir Adsorption Isotherm
Authors: Shuler P. J. 
Published: December 2007

SUMMARY
This paper presents a mathematical model for the scale inhibitor squeeze process. This particular model incorporates the Langmuir adsorption isotherm to describe retention/release of the inhibitor with the reservoir rock. This complements a previous, similar squeeze model based instead on the Freundlich adsorption isotherm. The analytical solution for a simplified version of both models requires only minimal computational effort.
Both models calculate the scale inhibitor concentration in the produced brine versus the cumulative produced water volume (and hence the squeeze lifetime). The Langmuir-based model appears to describe inhibitor return data and squeeze lifetime better for reservoirs containing a significant amount of clays and carbonate minerals. The Freundlich-based model better matches field data from cleaner formations such as are found in the North Sea.
Similar to the previous model, the Langmuir-based formulation illustrates the importance of the retention/release properties on squeeze lifetime. Parameter studies indicate the total amount of inhibitor injected is the most important design parameter controlling squeeze lifetime.
Scleroglucan Behavior in Flow Through Porous Media: Comparison of Adsorption and In-Situ Rheology With Xanthan
Authors: Huang Y. , Sorbie K. S. 
Published: December 2007

ABSTRACT
Scleroglucan is a nonionic polysaccharide biopolymer which has excellent viscosifying power in a wide variety of reservoir brines, shows high shear resistance and possesses good thermal stability. All of these properties are very important for polymer flooding applications. In order to apply this polymer in the field it is also necessary to develop a good understanding of its transport, retention and in situ (porous medium) theological properties.
This paper follows previous Work on the adsorption and the in situ rheology of xanthan biopolymer. An important aspect of the present work is the comparison of biopolymer characteristics between scleroglucan and xanthan. This comparison highlights some clear differences in the effects of polymer concentration and pH on the in situ rheological behaviour, owing to the different ionic nature of these two polysaccharides. The main new results presented in this paper relate to scleroglucan dynamic adsorption/retention and its effect on the in situ rheological behavior of this biopolymer, both in ballotini glass bead packs and in sand packed porous media. It is found that the general adsorption level is lower and adsorption effect on in situ rheology is negligible for relatively homogeneous, higher permeability ballotini packed porous media. However, the behaviour is very different for lower permeability sand packed porous media where scleroglucan shows very high levels of retention and a clear effect of this retention on polymer in situ rheology. The latter case indicates that there are still concerns on the propagation (filterability) of scleroglucan although these may not be a problem at higher temperatures under field flooding conditions.
Partially Hydrolyzed Polyacrylamide (PHPA) Mud Systems for Gulf of Mexico Deepwater Prospects
Authors: Hale A. H. , Mody F. K. 
Published: December 2007

ABSTRACT*
For exploration and development drilling of deepwater prospects in the Gulf of Mexico, operators have primarily utilized a high salt (20 percent w/w), partially hydrolyzed Polyacrylamide (PHPA) mud system. This system has been used for many years as one of the most inhibitive water-based mud systems commercially available to the industry. Observations from both the laboratory and the field indicate that shale is stabilized by the presence of PHPA. In this report, laboratory evidence is presented which investigates possible mechanisms by which PHPA influences cuttings as well as wellbore stability. In addition, results are presented which dictate requirements for maintaining an effective concentration of PHPA for shale stabilization and the impact of thinners on shale stabilization.
Asphaltene Stabilization in Alkyl Solvents Using Oil-Soluble Amphiphiles
Authors: Chang Chia-Lu , Fogler H. S. 
Published: December 2007

ABSTRACT
Asphaltene plugging is a known cause of near well-bore formation damage. The stability of asphaltenes is predominantly controlled by the thermodynamic state of crude oil. Changes of temperature, pressure and compositions of crude oil can result in the precipitaion of asphaltene components. In this study, the stability of asphaltenes in alkane solvents was investigated using a series of alkyl benzene-derived amphiphiles. The results indicate that the effectiveness of amphiphiles on asphaltene stabilization are strongly influenced by their chemical structure, including the polarity of head groups, the length of alkyl tails and the existence of extra polar groups. These results also provide the information about the interactions of asphaltenes and resin molecules in the crude oil. The small-angle X-ray scattering technique was used to investigate the physical structure of asphaltenes in the amphiphile/alkane solutions. The results indicate that solubilized asphaltenes can interact with each other or with amphiphiles to form associated colloids. The phenomena of precipitation and dissolution of asphaltenes in the porous media was investigated using visual micromodel experiments. In a dissolution experiment, the oil-soluble amphiphile/alkane solutions were proved to be capable of removing asphaltene deposits from porous media.
The Effect of Structure on Performance of Maleic Anhydride Copolymers as Flow Improvers of Paraffinic Crude Oil
Authors: Son A. J. , Graugnard R. B. , Chai B. J. 
Published: December 2007

ABSTRACT
The study was conducted to generate a mechanistic understanding of treating problematic paraffinic crude oils so that chemical treatments can be designed easily and applied more universally. Two crude oils, sampled from two continents, with very different wax contents and paraffin distributions were used to observe the influence of chemical structure on performance of various flow modifiers. In the industry, there is no known "universal" flow enhancer, however, a great number of wax-treating chemicals are derivatives of maleic anhydride. The study was focused on this widely used chemistry as the results would immediately benefit the industry. The performance of various esters of copolymers of maleic anhydride was compared using laboratory tests designed to simulate field conditions. A correlation between the wax content, the wax composition, the type of copolymer backbone, pendant groups and ester functionalities was found which can be explained through basic principles of solubility and steric hindrance.
Crude Oil Characterization Using Gas Chromatography and Supercritical Fluid Chromatography
Authors: Stadler M. P. , Deo M. D. , Orr F. M. 
Published: December 2007

Abstract
The carbon number distributions of 26 stock tank oils were determined by simulated distillation using gas chromatography and supercritical fluid chromatography using high-pressure CO2 as the carrier fluid. Carbon number distributions determined by the two methods were equivalent within normal experimental scatter. Comparison of the fraction of each crude oil eluted in the GC and SFC analyses indicates that for most oils, a significantly larger fraction of the oil elutes in an SFC analysis. In fact, essentially 100% of the hydrocarbons present in light oils elute from the column. In such cases, the internal standard analysis can be eliminated from SIMDIS without loss of accuracy. Another advantage of SIMDIS by SFC is that there is no danger of hydrocarbon decomposition at high temperature.
The Influence of Crude-Oil Composition on Mineral Adsorption and Wettability Alteration
Authors: Wolcott J. M. , Groves Frank , Lee Hyo-Guk 
Published: December 2007

Abstract
Berea sandstone cores were contacted with six different crude oils to determine the effects of oil composition on mineral adsorption and wettability alteration. The crude oils employed in the study encompassed a wide range of chemical and physical properties. Three different types of Berea sandstone cores were contacted with each crude: dry, untreated cores; cores that contained an initial brine saturation prior to contact with oil; and cores that were treated with potassium hydroxide (KOH) for clay stabilization and contained an initial brine saturation prior to contact with oil. The Amott method was used to evaluate wettability alteration. Thin-sections, total organic carbon (TOC), and Rock-Eval analyses were performed to assess the extent and nature of adsorbed organics.
Positive correlations were noted between wettability alteration and oil resin and asphaltene content, and between the extent of adsorption and oil resin and base content. The extent of adsorption was also found to be inversely related to the oil saturate content. There was little correlation between extent of adsorption and wettability alteration.
Effect of Nonproduced Fluids on Produced Water Treatment Equipment Efficiency
Authors: Bansal K. M. 
Published: December 2007

Abstract
With increasingly stringent environmental limitations on the disposal of treated produced water in offshore operations, it has become even more important to gain a better understanding of the process upsets which contribute to poor disposal water quality. One such process upset is caused by the handling of the non-produced fluids (fluids resulting from well stimulation or remedial operations and from miscellaneous processes such as deck drainage) in water treatment equipment (e.g. flotation cells, hydrocyclones etc.). This paper discusses the results of the field tests with various chemicals, normally present in non-produced fluids, on the performance of a bench model flotation cell. These results are not limited to flotation cells but are also applicable to other water treating equipment such as hydrocyclones. An approach to minimize the impact of the non-produced fluids on produced water treatment equipment efficiency is presented in the paper.
Filter-Cake Formation of Fracturing Fluids
Authors: Prud’homme R. K. , Wang J. K. 
Published: December 2007

ABSTRACT
The buildup of a polymer filter cake on the fracture face during hydraulic fracturing results in a decrease in the rate that water leaks off into the formation. The ability to predict this fluid loss is crucial to correctly design pumping schedules and to predict fracture geometry. It is also critical for the interpretation of the pressure and flow rate logs during fracture treatment. Laboratory tests of dynamic fluid loss are time consuming, and it is not possible to simulate in the laboratory the filter cake characteristics that occur far from the well bore. We have begun a fundamental study of filter cake formation that considers the micro-scale processes that govern cake formation. Filter cake formation is determined by the polymer concentration dependence of the permeability, osmotic pressure, and yield stress in the filter cake --all of which can be independently measured. This model will predict the polymer concentration profile in the filter cake, filter cake thickness, and fluid leakoff as a function of pressure drop across the filter cake. To verify this model we have developed a single fiber fluorescence probe to directly measure the polymer concentration in situ during filter cake deposition. Measurements of the concentration profile are presented for dilute HPG (hydroxypropyl guar) solutions and for 0.48 wt% (40 lb/Mgal) solutions.
Crosslinking of Hydroxypropyl Guar with Metal Ions
Authors: Clark P. E. , Balakrishnan M. , Sundram L. 
Published: December 2007

Abstract
Crosslinking of guar and hydroxypropyl guar (HPG) with metal ions is used extensively in the oilfield to increase the viscosity and thermal stability of solutions made from these polymers. Guar and HPG molecules have cis-hydroxyl groups that can react with metal ions or metal ion agglomerates to form crosslinks between polymer molecules. Crosslinking results in a viscous, gel-like solution that is difficult to characterize rheologically.
In this study, data generated with a cone and plate rheometer equipped with a special flow-through test fixture is used to demonstrate how the reaction rate and order change with shear rate. These data are used to develop a model for the reaction that explains not only the observations made in this laboratory, but also the observations made in a number of other research studies. In general, the reaction is fast at low shear rates and almost stops at high shear rates. Reaction rates and orders are a function of shear rate and the reaction product is also shear rate sensitive. Experimental evidence points to a shift from inter- to intramolecular reactions at high shear rates.
Laboratory Acidization of an Eolian Sandstone at 380°F
Authors: Wehunt C. D. , Van Arsdale Howard , Warner J. L. , Ali S. A. 
Published: December 2007

Abstract
Formation damage was simulated by injecting completion fluid into cores and conditioning at 380°F (193°C) overnight. Low hydrofluoric (HF) acid concentrations from 0.05- to 0.1% blended with 10% acetic (HAc) effectively removed the damage. Some other acid systems we tested also worked well. Acidizing did not reduce the measured compressive strengths of the cores; however, microscopic analyses showed layers within the cores may have been seriously weakened.
Divalent Ion-Resistant Polymer Gels for High-Temperature Applications: Syneresis Inhibiting Additives
Authors: Albonico Paola , Lockhart T. P. 
Published: December 2007

ABSTRACT
This paper introduces a new strategy for improving the high temperature stability of acrylamide polymer solutions and gels in aqueous solutions containing the divalent cations Ca2+ and Mg2+. Specifically, certain low molecular weight compounds capable of complexing with the divalent cations are shown to reduce significantly their negative impact on the solubility of acrylamide polymers and on the stability of crosslinked acrylamide polymer gels with regard to syneresis. Where the inhibitor-divalent ion complexes formed are soluble, it should be possible to propagate their polymer or gelant solutions through matrix rock; where insoluble divalent ion-inhibitor complexes are formed, these inhibitors may still be compatible with gel placement in fractured reservoirs or in the immediate vicinity of the wellbore. The results obtained offer the possibility to extend the upper temperature limit for the use of polyacrylamides and acrylamide copolymers in brines in both polymer flooding and polymer gel treatments.
Related studies show that pH is a key factor influencing the solubility of acrylamide polymers in the presence of divalent cations. This fundamental variable has been overlooked in earlier studies correlating PAAm solubility with the degree of polymer hydrolysis, divalent cation concentration, and temperature.
Weak Gel Formulations for Selective Control of Water Production in High-Permeability and High-Temperature Production Wells
Authors: Kohler Norbert , Rahbari Ramine , Han Ming , Zaitoun Alain 
Published: December 2007

ABSTRACT
Two gelling systems involving a thermally stable biopolymer-namely, polysaccharide G- and two different crosslinkers-namely, X-linker A and X-linker B- have been tested in the lab for water control applications. The methodology involved tube tests to check the phase diagrams, kinetics and stability of the gel under various temperature, salinity and pH conditions. The gel formed with X-linker B was shown to be much more stable and easier to control than the gel formed with X-linker A. With the X-linker B / Polysaccharide G system, at neutral pH, the kinetics of gelation was extremely slow at room temperature, but quicker above 70°C. Such a system can thus be mixed in surface facilities without any risk of premature gelling and behaves like a single polymer solution during the injection phase. In high-permeability cores, the weak gel formed with X-iinker B / Polysaccharide G was shown to induce a drop in the relative permeability to water an order of magnitude greater than the single polymer, while maintaining very good permeability to oil.