bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermal Reservoir Simulation Model of Production from Naturally Occurring Gas Hydrate Accumulations
Authors: Swinkels Wim J. A. M. , Drenth Rik J. J. 
Published: December 2007

Abstract
Interest in the potentially large deposits of natural gas hydrates and hydrate capped gas reservoirs is increasing. This interest is fuelled by foreseen requirements for large volumes of natural gas as a clean hydrocarbon fuel and by increasing deepwater and Arctic exploration and drilling experience. Analytical models are not sufficient any longer for developing production concepts for natural gas hydrate accumulations. We have applied a conventional thermal reservoir simulator to model production from natural gas hydrates and hydrate capped gas reservoirs.
Reservoir behavior of a hydrate-capped gas reservoir is modeled using a 3-D thermal reservoir simulator. The model incorporates a description of the phase behavior of the hydrates, heat flow and compaction in the reservoir and the hydrate cap.
Results help in understanding reservoir pressure and temperature behavior and allow matching of experimental data. The model also allows the calculation of well productivity, evaluation of well configurations, including horizontal wells and screening of production options. It shows the potentially self-sealing nature of the hydrate cap.
Production scenarios were also investigated for production from the solid hydrate layer itself, using horizontal wells and various ways of dissociating the naturally occurring gas hydrates. Important findings from these investigations are the role of excessive water production and the requirement for water handling facilities.
The paper concludes that thermal reservoir simulators can be used to build models of hydrate associated gas reservoirs. It is also concluded, that a dedicated data acquisition program is needed to obtain reservoir parameters for gas hydrate accumulations. Such parameters include relative phase permeability, heat capacity and thermal conductivity of the hydrate-filled formations, compaction parameters and rate of hydrate formation and decomposition in the reservoir.
Insights obtained from building these models help in acquiring the relevant reservoir data, interpreting observed reservoir behavior and in designing production scenarios for economical evaluation.
A New Efficient Averaging Technique for Scaleup of Multimillion-Cell Geologic Models
Authors: Li D. , Beckner B. , Kumar A. 
Published: December 2007

Abstract
Increased resolution in reservoir characterization is driving the need for efficient and accurate upscaling techniques for reservoir simulation on which reservoir performance prediction relies. Unfortunately, the existing averaging methods (i.e. harmonic, arithmetic, power law, geometric or a combination of harmonic and arithmetic methods) are only applicable under the circumstances of perfectly layered or perfectly random heterogeneity distributions, which realistic reservoirs are not. This paper presents a new averaging method that improves the upscaling averaging methods for realistic reservoirs and can substitute for the orders-of-magnitude slower performance of direct simulation methods, such as pressure solver techniques. The new averaging method first calculates the upper and lower bounds of the effective properties based on the nature of geology and then employs a new correlation, scaling, and rotation technique to estimate the effective properties for the upscaled grid. The approach not only preserves the accuracy of the time consuming simulation methods but also retains the speed of the traditional averaging methods.
Five real sandstone and carbonate reservoir geologic models (of which, three of them are multimillion cell models) from Africa, North America, and South America were employed as benchmark and working data sets to develop and validate the new technique. The technique has the advantage of suiting the more irregular geometries i.e. pinchouts, faults, and flexible simulation grids compared to the pressure solver methods which are more suited for relatively simple flow geometries.
Water Saturation Modeling: An Upscaling Point of View
Authors: Ekrann S. 
Published: December 2007

Abstract
The paper addresses some mathematical aspects of water saturation modeling. The upscaling problem, i.e., the substitution of an equivalent homogeneous medium for the real heterogeneous one, is shown to have a simple solution. This solution ensures reproduction of observed effective saturation in wells, and suggests methods to distribute saturation between wells. Elements of common practice are shown to be questionable. In particular, attempts to correlate effective saturation with effective permeability may preclude reproduction of observed saturation, and may lead to significant errors between wells.
Rigsite Measurement of Cuttings Weight Equipment: Method to Analyze the Data and Extended-Reach Field Test
Authors: Thonhauser Gerhard , Maidla Eric , O'Leary Paul , Millheim Keith 
Published: December 2007

Abstract
The technology for addressing the issue of hole cleaning is presented and two field tests have documented the successful results.
The technology includes a new mass flow rate equipment placed at the end of the shale shakers, a hole cleaning simulator, and a trend analysis methodology to diagnose hole cleaning problems.
The optimization of the drilling process is also addressed with the objective of minimizing the hole cleaning time.
Microbeads as Lubricant in Drilling Muds Using a Modified Lubricity Tester
Authors: Skalle P. , Backe K. R. , Lyomov S. K. , Kilaas L. , Dyrli A. D. , Sveen J. 
Published: December 2007

Abstract
Particles like barite and cuttings influence the friction properties of a mud. The standard API lubricity tester, however, cannot measure friction of fluids containing particles, and to overcome this problem it was modified with a cam setup. It was found that particles indeed alter the friction.
Large beads are being used to reduce friction. They are, however, filtered out in the solids control equipment and to avoid this, we have investigated smaller polymer microbeads which will pass unhindered. The microbeads reduce the friction in water based muds with around 40% which is significantly better than four commercial lubricants.
An Integrated Solution of Extended-Reach Drilling Problems in the Niakuk Field, Alaska: Part II- Hydraulics, Cuttings Transport and PWD
Authors: Green M. D. , Thomesen C. R. , Wolfson L. , Bern P. A. 
Published: December 2007

Abstract
The extended-reach drilling (ERD) program in the Niakuk field, North Slope, Alaska, was suspended in January 1998 due to hole problems in the 8.5-in sections on two ERD wells. An integrated study was undertaken to identify and address the problems. The areas examined included wellbore stability, drilling fluid optimisation, hydraulics and cuttings transport, operational practices, and pressure-while-drilling (PWD) tool utilisation. In the previous paper, the wellbore stability study determined the optimum salinity, down-hole mud density and limits for the equivalent circulation density (ECD) to minimise wellbore damage. To minimise the ECD, a low viscosity fluid with adequate cuttings transport was required. In this paper, the hydraulics and cuttings transport models used to optimise the rheology are discussed. An additional rheological concern was to minimise barite sag. Laboratory tests were performed to determine the fluid formulation to meet the rheological and barite sag requirements. Operational practices were also implemented to enhance cuttings transport in the long, high angle intervals, and to reduce surge and swab pressures on connections, when reaming and during trips.
The optimised drilling fluid and drilling practices were successfully applied to a medium ERD well in June 1998. Real-time PWD data analysis was essential to the operation. The effects of rotation and annular cuttings loading on the ECD were quantified through PWD tests in cased hole prior to drilling the interval. The ECD was monitored and controlled within the required limits during drilling. The hydraulic models, drilling fluid design and operational practices were further refined after that well. In August 1998, one of the problem ERD wells was re-entered. Using the techniques determined in the above studies, the well was successfully drilled with no hole-related problems. In this paper, the aspects integral to the success of these wells are discussed.
Flow Experiments on Concentrated Hydrate Slurries
Authors: Andersson V. , Gudmundsson J. S. 
Published: December 2007

Abstract
Natural gas hydrates have been proposed to capture associated gas produced from offshore marginal oil fields. To evaluate slurry based hydrate technology, the flow properties of both water-based and oil-based hydrate slurries were investigated for different hydrate concentrations. This paper summarizes the production of oil-based hydrate slurries and the flow experiments performed on these slurries. The flow experiments were carried out in laminar and turbulent flow in a high-pressure pipe viscometer in the hydrate laboratory at the Norwegian University of Science and Technology (NTNU).
Interdependencies Among E&P Projects and Portfolio Risk Management
Authors: Brashear Jerry Paul , Becker Alan B. , Gabriel Steven A. 
Published: December 2007

Abstract
Risk management through portfolio optimization requires the avoidance of positive correlation and exploitation of negative correlation among the individual assets in the portfolio. In developing a portfolio of E&P projects, some such interdependencies arise from geotechnical factors that are generally recognized, such as projects in the same play or trend being likely to have similar geologic uncertainties (e.g. source or seal) or correlated reservoir properties. Other correlations, however, are more difficult to recognize, let alone quantify. These include such above-ground uncertainties as: changes in environmental or operating regulations at the national and state levels; changes in the transportation network, processing or refining capacities, or end-use demand; evolution of exploration and recovery technologies; and changes in fiscal regimes or the policies of countries in the same market. Any of these can enhance or detract from the project's ability to compete with other projects, so can directly influence their viability. A new method for estimating the interdependencies that arise from such factors, based on reservoir-on-reservoir competition as evaluated by summary simulation of actual reservoir properties, technologies, costs, logistics, etc., is described, along with worked examples to demonstrate the changes in optimal choices attributable to consideration of above-ground uncertainties and the interdependencies they create.
The Quality Map: A Tool for Reservoir Uncertainty Quantification and Decision Making
Authors: da Cruz P. S. , Horne R. N. , Deutsch C. V. 
Published: December 2007

Abstract
The parameters that govern fuid flow through heterogeneous reservoirs are numerous and uncertain. Even when it is possible to visualize all the parameters together, the complex and non-linear interaction between them makes it difficult to predict the dynamic reservoir responses to production. A flow simulator may be used to evaluate the responses and make reservoir management decisions, but normally only one deterministic set of parameters is considered and no uncertainty is associated with the responses or taken into account for the decisions.
This paper introduces the concept of a "quality map", which is a two-dimensional representation of the reservoir responses and their uncertainties. The quality concept may be applied to compare reservoirs, to rank stochastic realizations and to incorporate reservoir characterization uncertainty into decision making, such as choosing well locations, with fewer full field simulation runs.
The data points necessary to generate the quality map are obtained by running a flow simulator with a single well and varying the location of the well in each run to have a good coverage of the entire horizontal grid. The "quality" for each position of the well is the cumulative oil production after a long time of production.
The geological model uncertainty is captured by multiple stochastic realizations. One quality map is generated for each realization and the difference between the realization maps is a measure of the uncertainty in the flow responses. For each cell, the lower quartile of the local distribution of quality is extracted to build a map, which can be used for decision making accounting for uncertainty.
The methodology for building the quality map is presented in detail and the applications of the map are demonstrated with fifty realistic reservoir models.
State-of-the-Art Simulator for Field Applications of Gas-Liquid Cylindrical Cyclone Separators
Authors: Gomez Luis E. , Mohan Ram S. , Shoham Ovadia , Marrelli Jack D. , Kouba Gene E. 
Published: December 2007

Abstract
The Gas-Liquid Cylindrical Cyclone (GLCC©1) is an example of a compact separator which is simple, lightweight, and having low capital and operational costs. The GLCC© has a wide variety of potential applications, varying from only partial to complete phase separation. This paper presents a state-of-the-art simulator for GLCC© design and analysis, based on an improved mechanistic model, written in an Excel Visual-Basic® platform. The simulator has two components namely, design wizard code and performance code. The design wizard is used for performing the preliminary design of the GLCC©, and the performance code enables detailed prediction of the complex hydrodynamic flow behavior in the GLCC©. This user-friendly simulator incorporates the best available technology for the design of GLCC© separators for the industry. The simulator has been used to design over 100 GLCC© units operating in the USA and around the world. Details of successful field application of GLCC© separator for offshore Lake Maracaibo, PDVSA, Venezuela, (multiphase flow-metering loop), PETROBRAS, Brazil, (external pre-separation) ARCO, Alaska (gas knockout) and Minas, CPI, Indonesia (bulk separation/metering), are presented and discussed. These examples demonstrate the potential, advantages, and benefits offered by the GLCC© simulator for enhancing the utilization of compact separators in both offshore and onshore environments.
Openhole Stability and Sanding Predictions by 3D Extrapolation from Hole Collapse Tests
Authors: Ewy R. T. , Ray P. , Bovberg C. A. , Norman P. D. , Goodman H. E. 
Published: December 2007

Abstract
Wellbore failure is best simulated in the laboratory by subjecting a model hole to simulated in-situ stresses. This can be routinely done on available core by performing a hole collapse test. This test uses a hollow cylinder with an outer diameter of 1.5 inches and a hole diameter of 0.5 inches. The jacketed sample is subjected to increasing pressure on the outer surface until collapse of the hole occurs. This provides a direct measure of the stress required to cause hole failure in that particular formation interval. To predict hole stability and sanding, a method is required for applying this measured strength to the downhole situation. Equations are necessary to account for the fact that the downhole stress situation is more complex than that in the hole collapse test. These equations must include the three-dimensional nature of rock strength. A three-dimensional analytic model is presented that is applicable to both stability and sanding of open wellbores. This model uses a Modified Lade failure criterion which properly accounts for the effect of the intermediate principal stress on rock failure. The Modified Lade rock strength parameters are extracted from the measured hole collapse strength and are then combined with the in situ stresses and formation pore pressure using one of two sets of equations: The first set determines required mud weight for stability while drilling, while the second set determines allowable drawdown pressure for prevention of sand production.
Roughness of Hydraulic Fractures: The Importance of In-Situ Stress and Tip Processes
Authors: van Dam D. B. , de Pater C. J. 
Published: December 2007

AbstractThe surface roughness of hydraulic fractures reflects the fracturing process at the tip. We did an experimental study of hydraulic fracture propagation, in which a characteristic roughness pattern was observed. This roughness developed without shear- or torsional loading in the plane of the penny-shaped fracture. The roughness showed to be determined by material properties and the externally applied stresses on the sample, which represent the effective in-situ stresses. We quantified the roughness, and showed that it correlated well with a measure of the plastic zone size around the fracture tip. New explanations for fracture surface roughness that develops under mode I loading conditions are presented.
Incorporating Crossflow and Spurt-Loss Effects in Filtration Modeling Within a Fully 3D Fracture-Growth Simulator
Authors: McGowen James M. , Barree Robert D. , Conway Michael W. 
Published: December 2007

Abstract
A practical numerical fracturing-fluid filtration model has been successfully incorporated into a fully three-dimensional (3D) fracture-growth simulator. This filtration model incorporates four principal filtration mechanisms: (1) compressibility and flow of the reservoir fluid, (2) invasion of non-Newtonian filtrate, (3) filter-cake deposition, and (4) quasi-equilibrium of filter-cake thickness with the fluid shear stress. When this filtration model is used with a numerical 3D fracture-growth simulator, the impact of these filtration mechanisms on fracture-treatment design can be evaluated. Because the 3D fracture-growth simulator allows the filtration properties to vary spatially, the simulator can accurately evaluate the impact of changing filtration parameters such as filtration pressure, shear rate, fluid rheological properties, and fluid composition.
Before evaluation in the fracture simulator, the results of this new filtration model are first verified against laboratory-generated filtration data, and then compared to the classical filtration theory. The fully 3D fracture-growth simulator is then used to verify the impact of the fluid-leakoff model. The comparisons show that this filtration model can have a pronounced effect on treatment design when spurt loss is significant, and in treatments in which the quasi-equilibrium filter-cake formation (caused by fluid flow over the filter cake) causes dramatic deviations from classical filtration models. The simulations highlight concerns about the accuracy of present minifracturing analysis and treatment-design techniques.
High Propagation Pressures in Transverse Hydraulic Fractures: Cause, Effect, and Remediation
Authors: Deeg W. F. J. 
Published: December 2007

Abstract
Highly deviated or horizontal wells completed in tight formations are frequently aligned with the minimum principal formation stress and completed with evenly spaced, transverse hydraulic fractures. When a transverse hydraulic fracture is created, unexpectedly high fracture-propagation pressures are often encountered. The hydraulic fracture-growth simulators currently available cannot explain these high treating pressures. Therefore, the pressures have been attributed to complex fracture geometries.
Another likely cause of unexpectedly high fracture-treating pressures is the fracturing-fluid flow regime under which transverse hydraulic fractures are created. In transverse fractures, fluid flows radially outward from a fipoint sourcefl (the wellbore). Flow is not linear, as implicitly assumed and hard-coded in many of today™s hydraulic-fracturing models or simulators.
Where radial flow exists under a constant injection rate, fluid velocities are much greater near the wellbore than out in the fracture. This condition causes high near-wellbore pressure gradients, which result in relatively high fracturing-fluid pressures in and near the wellbore, compared with pressures out in the hydraulic fracture.
This pressure-profile effect on fracture-propagation pressure and created fracture dimensions is demonstrated with analytical calculations. The pressure profiles analyzed include a constant pressure throughout the fracture (the equilibrium base case) and a parabolic pressure decay along the length of the fracture (the most severe case considered).
The calculations show that, for severe hydraulic-fracture pressure profiles, the fracture-propagation pressure in the wellbore can be more than 12 times greater than the propagation pressure required for constant pressure throughout the fracture. The more severe the pressure drop in the near-wellbore region, the wider and shorter the hydraulic fracture will be.
Results from these calculations suggest procedural changes for minimizing the effects of adverse pressure profiles. They also demonstrate that current hydraulic-fracturing models and simulators must be modified to account for the pressure profiles expected under radial-flow conditions.
Injection of Lean Gases into Light Oil Reservoirs: Interfacial Aspects
Authors: Lakatos I. , Bauer K. , Lakatos-Szabó J. , Puskás S. , Palásthy Gy. , Trömböczki S. , Kosztin B. 
Published: December 2007

Abstract
Application of lean gases, particularly a methane rich gas, nitrogen, carbon dioxide, air and their mixtures in an ultra light oil bearing reservoir located in Southern Hungary, is in an advanced stage. The relevant studies and mathematical simulations have definitely indicated a substantial surplus oil production and it was also revealed that gravity segregation and vaporization of light hydrocarbons were the main elements of the displacement mechanism. However, well founded arguments have arisen about anomalous interfacial phenomena and precipitation of some oil constituents during the recovery process since the oil was strongly paraffinic and the predicted vaporization was high. Therefore, a detailed laboratory study were commenced to determine the effect of nitrogen, carbon dioxide and lean methane on surface and interfacial properties. On the basis of the experimental results it was concluded that the well known surface and interfacial effects, like enrichment of asphaltenes, resins and heavy hydrocarbons at interfaces, can be neglected when lean and non-reactive gases are injected into an ultra light bearing reservoirs. On the other hand, the precipitation of paraffins and other waxes at oil/water interface may take place even at very low vaporization in both the reservoir space and the surface facilities. Since that inter-facial, probably catalyzed phenomena is newly recognized, further laboratory and field studies are needed to elucidate its detrimental effects on recovery efficiency, well performance and surface technology.