bluuebunny/crossref_metadata_2025_split huggingface dataset:
Two-Dimensional Polymer Flood Simulation
Authors: Slater George E. , Ali S.M. Farouq 
Published: December 2007

Abstract
The present experimental and theoretical investigation was concerned with the oil recovery and sweep efficiency obtained in a two-dimensional polymer flood. Both single phase (brine displaced polymer flood. Both single phase (brine displaced by polymer solution) and two-phase (oil and brine displaced by polymer) displacement studies were conducted. The mathematical models developed utilize the concept of the polymer resistance factor, and its variation with throughput past any given point in the flow pattern. The models were validated on the basis of good agreement observed between the predicted and the experimental results.
Experimental displacement studies were carried out in both homogeneous and heterogeneous two-dimensional transparent models, representing the quadrant of a five-spot pattern. The models were packed with glass beads of different sizes in a predetermined manner. Prior to a polymer flood, the porous medium was saturated with brine, or with brine and a refined oil, depending on the type of run. Next a polymer solution, containing a dye, was injected into the model. Effluent samples were collected, and the flood fronts were photographed at regular intervals.
For the purpose of simulation, resistance factors under two-phase flow conditions were determined, and it was shown that the average mobility of the displacing phase across a linear element of the porous medium used can be calculated-as a function of throughput across this element. This technique was generalized for areal elements, and was incorporated into the mathematical models.
The single phase, two-dimensional model considered a flow system in which the mobility of the displacing liquid was changing with time behind the flood front. The pressure distribution in the flow system at each time step was obtained, and was used to compute the sweep patterns for comparison with the experimentally patterns for comparison with the experimentally determined patterns.
The two-phase, two-dimensional model involved the simultaneous solution of the two-phase flow differential equations, incorporating the resistance factor concept in the solution scheme. An implicit-explicit technique was employed for solving the finite difference equations obtained.
Good agreement was observed between the predicted and the experimental polymer floods. predicted and the experimental polymer floods. Under the experimental conditions involved the improvement due to the use of polymer was approximately 10% for oil recovery, and 5 to 15% for sweep efficiency.
Assessing Political Risk for Foreign Investments
Authors: Downey Marian W. 
Published: December 2007

Abstract
Political risk assessment provides a prediction of the likelihood that future foreign government actions will deteriorate the return on a planned foreign investment. Such political risk predictions are commonly provided with great assurance by political experts. Political risk assessments are frequently quantified to two or three significant figures, so that comparisons can be made between various countries, at various times in the future. It is the contention of this paper that most of such quantifications and predictions are nonsense; that the political future is not being accurately predicted.
It is useful to describe some general axioms on predicting the future: (1) Future events can be predicted in a rigorous manner only if they represent expected outcomes of physical laws; (2) Future events can be predicted with some statistical confidence if they represent a modest extrapolation of consistent history into the future; (3) The farther into the future one predicts, the less reliable history-based predictions should be; (4) Predictions become less certain as more parameters influence the event; (5) Predictions must be less certain as more precision is required; and (6) Predictions of singular future complex political events are merely guesses, no matter how they may be swaddled in statistical mumbo-jumbo.
For proper analysis of political risk it is important to create multiple scenarios of the future, to be well acquainted with foreign politics, and to understand the economic fundamentals of the country where you are considering investments.
Such approaches allow management to look for possible flexibilities in investments, to consider insurance, hedging, and other risk abatement techniques against some of the most likely negative political/economic outcomes. The proper investor question is … "what can I do to mitigate possible future country risk?" … not, "what is the proper discount factor to allow for future country risk?" Wise investors need to take positive actions early in the investment cycle so that they may alter, rather than hope to measure, political risk in foreign investments.
Geophysical Reserve Classification Proved, Probable, and Possible
Authors: Schlagenhauf Mark , Jaynes Earl 
Published: December 2007

Abstract
The development of 3-D seismic is the single most important technological breakthrough in many years1. Some guidelines to separate reserves into the traditional classification of proved, probable, and possible using seismic methods have been developed and refinements to the current definitions proposed. These guidelines supplement the SPE reserve definitions and the SPEE (Society of Petroleum Evaluation Engineers) guidelines, which were published in the 80's and do not detail the use of seismic data in classification of reserves. Since the oil and gas industry is increasing the use of 3-D seismic, it is lime for the SPE to recognize the usefulness of 3-D seismic data in classifying reserves. Use of 3-D seismic data is especially important in classifying reserves in complex structural and stratigraphic traps with limited well and production data. The seismic methodology and thought process and typical interpretation steps are illustrated in two simulated case studies. Smarter, faster, cheaper, more profitable oil and gas development and reserve evaluation result from the use of 3-D seismic.
Financial Incentives for Marginal Oil and Gas Production
Authors: Terzian G. A. , Enright J. M. , Brashear J. P. 
Published: December 2007

Abstract
Congress and the Administration are considering Federal tax incentives to improve the economics of marginal oil and gas wells. The effectiveness of these incentives will depend on the specific provisions of the incentive, primarily whether they can be used by the large percentage of marginal well operators in AMT or without taxable income. Comprehensive assessment of Federal marginal well incentives requires a methodology that accounts for the diversity of marginal production operations. This paper presents a marginal well database, model, and methodology designed specifically to assess the costs and benefits of Federal tax incentives for marginal wells. Selected results are presented, along with general conclusions about Federal marginal well tax incentives based on numerous analyses.
An Alternative Concept of Investment for Improved Profitability Measures
Authors: Clapp Robert V. 
Published: December 2007

Summary
Discounted cash flow methods for evaluating investment opportunities enjoy wide use in the petroleum industry. The two most popular measures are net present value and internal rate of return. While these two measures are generally suitable as accept/reject criteria, they are not so useful in capital rationing situations, where a ranking of projects is required. Decades ago authorities suggested that the net present value divided by the initial outlay is a better measure for ranking projects.
This kind of measure becomes more difficult to apply correctly when ail the capital costs in a project are not incurred up front, but are spread over a number of years. It is common practice to discount these future capital outlays back to the present and include them in investment (the divisor in the index). Simple examples demonstrate, however, that some obviously erroneous rankings can result from this procedure. By using an alternative definition of project investment, based only on the project net cash flows and the discount rate, we can avoid these pitfalls and obtain a better profitability measure for ranking projects.
An Assessment of Perforating Performance for High Compressive Strength Non-Homogeneous Sandstones
Authors: Blosser W. R. 
Published: December 2007

ABSTRACT
This paper presents the basis, approach, results, and conclusions from a study undertaken to evaluate perforation skin within an environment of high compressive strength non-homogeneous sandstone. It incorporates and integrates both field and laboratory data in an effort to better understand what component completion perforating skin contributes to total mechanical skin in the presence of drilling damage.
A Laboratory Evaluation of Acid Propagation in Relation to Acid Fracturing: Results and Interpretation
Authors: Bazin B. , Roque C. , Bouteca M. 
Published: December 2007

ABSTRACT
To design acid fracturing treatments, acid fracturing models require acid leakoff values including experimental coefficients such as acid propagation rate and acid penetration distance into the formation.
This paper presents an experimental study aiming at defining a methodology for the acquisition of these parameters. The pressure variation curve obtained during a conventional acid injection experiment in a Hassler cell is analysed in relation with the dissolution mechanism. X Ray Computerized Tomography is applied to characterize the dissolution patterns. Influence of core length, acid concentration and acid flow rate are considered. Critical values are found above which the filtration process is dominated by the wormholing mechanism.
Critical lengths and rates are interpreted in terms of the Damkohler Number, i.e. the ratio of the acid brought by transport to the acid consummed by the chemical reaction. In addition, from the interpretation of the experimental results, a new methodology is proposed for the measurement of acid propagation rates and distances.
Visualisation of Drilling-Induced Formation Damage Mechanisms using Reservoir Conditions Core Flood Testing
Authors: Francis P. A. , Eigner M. R. P. , Patey I. T. M. 
Published: December 2007

ABSTRACT
Reservoir conditions core flood tests have been carried out to examine the damage arising from overbalanced drilling-in operations. Gannet field cores were exposed to a number of water- and oil-based field muds currently in use by Shell Expro. Results showed that the initial permeabilities to crude oil were dramatically reduced after exposure to overbalanced mud and subsequent back production of crude oil. Thin section petrography and SEM/XRD analysis of the cores clearly showed the source of impairment in all cases to be a thin layer of mud solids plugging pores and throats exposed to the wellbore face, forming an effective permeability barrier that was not dislodged by crude drawdown under realistic drawdown. The results were confirmed by trimming of 1 cm from the wellbore face of the core that led to a restoration of initial permeability.
An Integrated Experimental Approach for Evaluating Formation Damage Due to Drilling and Completion Fluids
Authors: Longeron D. , Argillier J. -F. , Audibert A. 
Published: December 2007

ABSTRACT
The paper describes an experimental approach to study the formation damage induced by drilling muds in oil bearing formations. This approach includes i) static and dynamic invasion tests on long core samples performed either under CT Scanning or with specific equipment allowing pressure measurements along the core sample, and ii) characterization of both external and internal mud cakes by means of Cryo-SEM examinations.
A series of seven water-based mud invasion experiments has been conducted on high permeability clayey sandstones. The amount and the extent of formation damage have been quantified. The results show that global oil return permeabilities vary from 44% to 90% of initial permeability depending on oil viscosity and overbalance pressure.
Hysteresis of saturations due to retention of invaded aqueous filtrate was always observed, up to 17 saturation units. This induced an adverse relative permeability effect which may significantly contribute to oil permeability impairment.
Stress Sensitivity in the Dulang Field - How it is Related to Productivity
Authors: Bin Tajul Amar Zarool Hassan , Altunbay Mehmet , Barr Duncan 
Published: December 2007

ABSTRACT
All rocks are sensitive to changes in stress. In the Dulang Field sandstones, stress sensitivity is affected by differences in texture, mineralogy and clay type. In this study, we present the results of a study that shows how stress sensitivity is related to the make up of a rock and how it affects the productivity. The sensitivity of permeability - and therefore transmissivity - to stress in the Dulang Field strongly correlates with the general classification of reservoir quality with better quality rocks showing lesser sensitivity to stress. However, there are some anomalies in the stress sensitivity of porosity. While the sensitivity of permeability to stress increases with decreasing rock quality, the same does not hold for the sensitivity of porosity to stress. These deviations are explained by changes in cementation, clay type, clay morphology and clay locations in the pore structure.
Understanding why stress sensitivity changes in the Dulang Field is essential for its future development. Knowing the reasons behind reservoir behaviour allows better prediction and control of future production. Some zones will compact differently from others as the field produces. Differences in compaction are due to the different make up of the reservoir rocks. Heterogeneity in compaction affects the productivity irregularly, and therefore, the economics of the field. By knowing which zones are likely to compact first, production rates and scheduling can be adjusted to reduce the stress-induced damage. The findings of this study can be used to make more realistic prediction of future production rates via numerical simulators, thus providing a tool for improving field management and company profits. This is important not only for the Dulang Field, but also for any field where changes in stress are likely to affect production due to heterogeneous compaction of the reservoir.
Factors Affecting Proppant Flowback with Resin Coated Proppants
Authors: Almond S. W. , Penny G. S. , Conway M. W. 
Published: December 2007

ABSTRACT
Resin coated proppants (RCP's) have been used to prevent proppant flowback for several years in the hydraulic fracturing of oil and gas wells. Proppant flowback problems, however, still exist with the commercially available RCP's and several operators report failures around the world under a variety of well conditions. To date, a clear explanation of the RCP failure mechanisms and the conditions under which failure occurs has not been presented in the industry.
A correlation between the unconfined compressive strength (UCS) of RCP materials and the proppant flowback potential has been previously presented by Vreeburg, et al11. This paper will present the results of a study on a variety of factors which effect the proppant flowback of a number of commercially available RCP materials. These factors include 1) the effect of fluid pH (7 to 12) and fluid type (KCL, seawater and a HPG/Borate fracturing fluid), 2) the effect of fluid/proppant slurry shear, 3) the effect of closure pressure during RCP curing, 4) the effect of stress cycling and 5) the effect of downhole flow conditions on proppant flowback.
New Breaker Technology for Fracturing High-Permeability Formations
Authors: Norman Lewis , Vitthal Sanjay , Terracina John 
Published: December 2007

Abstract
Regained permeability studies with HEC polymer in high-permeability cores revealed that persulfate-type oxidizing breaker and enzyme breaker do not adequately degrade the polymer. Use of high concentrations of acid or peroxide breakers did show improved breaking, but additional work is needed to apply high concentrations of these breakers properly. Sodium persulfate breaker was found to be thermally decomposed, and its decomposition was accelerated by formation minerals. Enzyme breaker adsorbed onto the formation, but still partly functioned as a breaker. Dynamic fluid-loss tests with reduced-pH, borate-crosslinked gels suggest that accelerated leakoff away from the wellbore could be obtained through the use of a delayed-release acid. Rheological measurements confirmed that a soluble delayed-release acid could be used to convert a borate-crosslinked fluid into a linear gel. This conversion was visually confirmed by tests involving a delayed-release acid and a borate-crosslinked fluid in a single-pass flow loop apparatus. Higher concentrations of breaker were placed in a borate-crosslinked fluid by encapsulating the breaker, and controlled viscosity reduction was obtained.
A simulation using a 3D commercial simulator showed improved cumulative oil production when increased fluid loss from a soluble delayed-release acid was applied.
Low Permeability Gas Reservoir Production Using Large Hydraulic Fractures
Authors: Holditch Stephen Allen , Morse R.A. 
Published: December 2007

Abstract
There has been relatively little work published on recovering hydrocarbon gas from published on recovering hydrocarbon gas from low permeability reservoirs. Recently several nuclear projects have explored the feasibility of creating a cavity and a fractured zone in such a formation to stimulate production. One such test, Gasbuggy, was begun Dec. 10, 1967, with the detonation of a 26-kt nuclear device in the Pictured Cliffs formation, Rio Arriba Co., N. M.
This paper presents a study of stimulating low permeability reservoirs by the creation of long hydraulic fractures. A two-dimensional, two-phase numerical model was used. The reservoir properties of the model approximated those published for the Pictured Cliffs formation. The situations simulated were both vertical and horizontal fractures extending up to 3,000 ft from the producing well. Also, a model simulating a nuclear cavity was designed. This model simulated a well containing an 80-ft radius cavity with a fractured zone of 100 times the reservoir permeability, extending 200 ft past the cavity. The situation simulated was for production with a constant wellbore pressure. Production rate and cumulative gas produced were monitored as functions of time. From these parameters an economic evaluation of each system was prepared. The results of this study showed that all fractures of greater than 1,000-ft radius had greater productivity and greater cumulative gas productivity and greater cumulative gas produced than did the nuclear cavity. It produced than did the nuclear cavity. It appears that large hydraulic fractures may provide an economic means of producing gas from provide an economic means of producing gas from very low permeability reservoirs.

Introduction
There are large quantities of known hydrocarbons in place that are not being produced because the formation containing the produced because the formation containing the oil or gas has a permeability too low to allow economic production rates. In order to produce this type reservoir, some form of stimulation is required. There has been relatively little information published on the stimulation of low permeability reservoirs. In the past few permeability reservoirs. In the past few years, some projects have been conducted concerning the application of contained nuclear explosions for increasing the productivity in tight formations. The purpose of nuclear stimulation has been to create a large cavity with a radial fractured zone extending past the cavity, or in effect increasing the radius of the wellbore.
Another stimulation method is hydraulic fracturing. The purpose of fracturing is usually to improve the formation capacity near the wellbore, offsetting the damage that occurred while drilling. However, another use of fractures presented by L. E. Wilsey provided the basis for this work. provided the basis for this work.
An Innovative Technique for Damage By-Pass in Gravel Packed Completions Using Tip Screen-Out Fracture Prepacks
Authors: Montagna James N. , Saucier R. J. , Kelly Pete 
Published: December 2007

ABSTRACT
An innovative completion technique is being used in wells that require sand control to help eliminate high skins and increase pay, or effective kh, and thus improve well productivity. The success of this technique lies in concentrating high conductivity proppants in the near-wellbore region. This is accomplished by creating and propping a properly designed, length limited, hydraulically-induced fracture in conjunction with an annular water gravel pack. The result is a highly conductive flow path from virgin formation, through the near-wellbore damaged zone, and into the wellbore that also controls formation sand.
The limited fracture is designed with the intent of preserving the integrity of the near well gravel pack since this aspect is critical to realizing the full benefits of the fracture. Industry data indicates that optimum gravel packing is achieved with a brine proppant carrier. In some cases, the entire operation (limited fracture and gravel pack) may be completed with brine. However, in other cases, as discussed here, the high leak-off associated with brine is reduced by a product developed to overcome the excessive fluid leak-off. Brine following this material provides the carrier medium for proppant placement in the fracture and for the gravel pack.
The process is described and examples of field applications and results will be presented.
Specific Selection Criteria and Testing Protocol Optimize Reservoir Drill-in Fluid Design
Authors: Donovan Joseph P. , Jones Tom A. 
Published: December 2007

Abstract
Proper test and evaluation methodology for reservoir drill-in fluids is an important step in the construction design of a producing wellbore. Drill-in fluids are specifically designed to meet drilling and completion objectives, simplify reservoir cleanup and maximize production rates in open hole completions. New protocols developed by drilling fluid and completion laboratories have proven to be effective tools for evaluating fluid designs that optimize production.
Drill-in fluid selection begins with an initial screening process taking into account qualifying issues such as environmental acceptability, reservoir temperature, physical limitations, and chemical compatibility between the fluid and the reservoir. The final fluid formulation should minimize formation damage, fluid leak-off rates, breakout pressures, and wellbore cleanup of drill-in and completion operations, thus maximizing the productivity of the well.
Formation damage risks can be minimized if laboratory testing procedures parallel specific reservoir conditions. Case studies confirm that a methodology based on laboratory data that incorporates drilling fluid, completion, and workover operation protocols is effective in lowering completion costs and increasing production.
Prediction of Asphaltene Deposition During Production - Model description and Experimental Details
Authors: Takhar S. , Ravenscroft P. D. , Nicoll D. C. A. 
Published: December 2007

Abstract
Asphaltene deposition can arise during normal production causing formation damage, precipitation in tubing, difficulties in wireline operations, stuck valves and lost production.
Identifying which type of crudes will display this behaviour, prior to full production, enables the operator to make remedial plans.
A short description of a thermodynamic model to predict the onset parameters (temperature, pressure) will be described along with the essential experimental data required as input for subsequent modelling studies. This will be supported via model validation from real field data from two of BPX's North Sea fields.
A key conclusion of the findings is the ability to predict the deposition of asphaltenes downhole without the need for generating data from expensive single phase downhole samples.