bluuebunny/crossref_metadata_2025_split huggingface dataset:
Molecular Structure and Aggregation of Asphaltenes and Petroleomics
Authors: Mullins O. C. 
Published: December 2007

Abstract
Tremendous strides have been made recently in asphaltene science. Many advanced analytical techniques have been applied recently to asphaltenes elucidating many asphaltene properties. The inability of certain techniques to provide correct asphaltene parameters has also been clarified. Longstanding controversies have been resolved. For example, molecular structural issues of asphaltenes have been resolved, in particular, asphaltene molecular weight is now known. The primary aggregation threshold has recently been established by a variety of techniques. Characterization of asphaltene interfacial activity has advanced considerably. The hierarchy of asphaltene aggregation has emerged into a fairly comprehensive picture - essentially in accord with the Yen model with the additional inclusion of certain constraints. Crude oil and asphaltene science is now poised to develop proper structure-function relations that are the defining objective of the new field - Petroleomics. The purpose of this paper is to review of these developments in order to present a more clear and accessible picture of asphaltenes - especially considering that the asphaltene literature is a bit opaque.
Reservoir Initialization in Two-Phase Hydrocarbon Reservoirs from Well PVT Data
Authors: Nasrabadi H. , Firoozabadi A. 
Published: December 2007

Abstract
In a reservoir with a gas cap and an oil column, natural convection can play a significant rule in species distribution in both gas and oil phases. In this work, we are interested in computing the species distribution in such reservoirs based on a given pressure and composition from a well in addition to permeability and temperature profiles. We present the formulation of the problem and take into account thermal, molecular and pressure diffusion in addition to natural convection. Results from numerical calculations show that the location of the GOC is significantly affected by both natural convection and diffusion. Numerical results also reveal that the distribution of species is affected by both natural convection and thermal diffusion.
Achieving True Sandstone Reservoir Stimulation in Deepwater Horizontal Wells
Authors: Mendez A. , Neumann L. F. , de Almeida Pinto E. , Torres R. , Farias R. , Acosta M. 
Published: December 2007

Abstract
In offshore horizontally completed wells, an acid job is usually pumped to remove the filter cake, previously created to allow sand control equipment and gravel be placed across the entire extended section. When such wells are acidized to remove the filter cake with a hydrochloric: hydrofluoric acid mixture, the resulting skin values are still in the positive range.
An improved HF acid system has been introduced in the Campos Basin-offshore Brazil with outstanding results. The HF acid system uses an organophosphonic acid complex to control the generation of HF and to dramatically reduce potentially damaging secondary and tertiary precipitates.
This paper describes the results of field treatments showing truly stimulated wells with negative skins - a first in this Campos Basin field for deepwater horizontal wells. Case histories with conventional regular hydrochloric: hydrofluoric acid mixture and with the improved acid system used will be presented. Laboratory core flow tests were performed in advance of the field program with seven different acid blends.Only one acid blend resulted in complete mud damage removal and true stimulation. Innovative equipment design, a state-of-the-art vessel with real-time monitoring capabilities, improved placement techniques and environmentally-friendly materials, are helping to transform acidizing into a valuable method in the quest for optimum performance from every injector, oil and gas well asset.
Optimal Well Completions Using Radial Profiling of Formation Shear Slownesses
Authors: Sinha B. , Vissapragada B. , Kisra S. , Sunaga S. , Yamamoto H. , Endo T. , Valero H. P. , Renlie L. , Bang J. 
Published: December 2007

Abstract
Borehole sonic data can be useful for various design decisions in the oil and gas industry; e.g., well planning, wellbore stability, and reservoir management. Optimal well completions require both the detection and estimation of the radial extent of near-wellbore alteration in reservoir intervals. We have analyzed borehole sonic data from a new tool that contains 8 azimuthal receivers at 13 axial positions with an inter-receiver spacing of 6 in. The large number of receivers together with new processing algorithms enables reliable modal decomposition and slowness dispersion estimates. We present results from the Backus-Gilbert inversion of cross-dipole and Stoneley dispersions that yields radial profiles of three shear slowness in the three orthogonal planes. We show theoretical validation of the dipole and Stoneley radial profiling of the shear slowness algorithms using synthetic dispersions for known variations in the compressional and shear slownesses. The inversion algorithms account for the sonic tool effects on dispersion data. Inversion of cross-dipole dispersions yields radial profiles of the fast and slow dipole slownesses averaged over the two opposite quadrants. In contrast, the Stoneley radial profiling algorithm outputs azimuthally averaged shear slowness in the cross-sectional plane of the borehole. Inversion of cross-dipole and Stoneley dispersions yields three shear slowness logs at various radial positions away from the borehole surface.Near-wellbore softening and stiffening are characterized by larger and smaller shear slownesses than those in the far-field. Identification of near-wellbore softening caused by mechanical damage aids depth selection for wireline pressure measurements to avoid sections that are prone to seal failures. In addition, it can help identify mechanically competent depth intervals for stimulation. We illustrate shear slowness profiling results from sonic data acquired in a few wells in the North Sea. This study has demonstrated a consistent correlation between a negligibly small difference between the near-wellbore Stoneley and dipole shear slownesses and negligibly small fluid mobility implying tight zones where fluid samples could not be extracted. The radial extent of mobility impairment is estimated from radial profiles of both the Stoneley and dipole slownesses that help in designing optimal perforation tunnels extending beyond the damaged annulus.
Near-wellbore Alteration and Formation Stress Parameters using Borehole Sonic Data
Authors: Sinha B. , Bratton T. , Cryer J. , Nieting S. , Ugueto G. , Bakulin A. , Hauser M. 
Published: December 2007

AbstractHighly depleted reservoirs exhibit sharply lower pore pressures and horizontal stress magnitudes than in the overlying shaly formation. Drilling through such depleted reservoirs can cause severe fluid loss and drilling-induced wellbore instability.Accurate and reliable estimates of horizontal stresses can provide early warning of impending drilling problems that may be mitigated by appropriate drilling fluid design and drilling practices. We have developed a new multi-frequency inversion algorithm for the estimation of maximum and minimum horizontal stress magnitudes using cross-dipole dispersions. Borehole sonic data for the case study presented in this paper was acquired by a cross-dipole sonic tool in a deep-water well, offshore Louisiana in the Gulf of Mexico (GOM). The logged interval spans 1000 ft below the casing shoe. In addition, the Modular Dynamic Tester (MDT)1 mini-frac tests were performed at three depths in shale, yielding two minimum horizontal stress magnitudes. The borehole sonic data was suitable for inversion of cross-dipole dispersions at three depths in shale and also at a depth in a highly depleted sand reservoir. There was one depth in shale above the depleted sand where we could estimate the minimum horizontal stress magnitude using both the MDT mini-frac tests and inversion of borehole sonic data.The results of the two techniques are consistent, providing encouragement for further validation of the multi-frequency inversion of cross-dipole dispersions to estimate horizontal stresses. Even though the overburden stress is expected to increase with depth, both the maximum (SHmax) and minimum (Shmin) horizontal stresses obtained from the inversion of borehole sonic data are significantly smaller in the depleted sand than in the overburden shale. However, both the horizontal stress magnitudes increase again in the shale below the depleted sand. Such rapid variations in horizontal stress magnitudes cause large fluctuations in the safe mud weight window. This challenge in drilling through the depleted sand was successfully handled by using special drilling fluid to mitigate seepage losses and differential sticking in the depleted sand and overlying shale.We have also performed Dipole Radial Profiling (DRP) of formation shear slownesses using the measured cross-dipole dispersions at three depths in shale and one in the highly depleted sand. Analysis of radial profiles in the two orthogonal directions indicates plastic yielding or stiffening of rock in the near-wellbore region. While plastic yielding increases the shear slowness, stiffening would reduce the shear slowness.
The Russian Experience in Reserves Submissions to the SEC
Authors: Gochenour D. T. 
Published: December 2007

Abstract
This paper looks at the historical experience of Russian oil companies in converting their reserves standards to those of the SPE or SEC to conform with the requirements of Western investors.The experience has not been a happy one, and has demonstrated some of the pitfalls of how the SEC administers its standards and definitions.It also shows that while the SPE is going down the path of probabilistic reserves definitions, the SEC is promoting an even more arbitrary deterministic and literal rules based approach which is getting farther away from a scientific definition.
Dynamic Modeling of Invasion Damage and Impact on Production in Horizontal Wells
Authors: Suryanarayana P. V. , Wu Z. , Ramalho J. , Himes R. 
Published: December 2007

Abstract
We present a novel approach that combines dynamic reservoir simulations and special core tests to model the extent of invasive damage and its impact on flow-back during production. A radially adaptive 3D "micro" simulator is used to estimate the extent and impact of filtrate invasion on near-wellbore saturation and reservoir pressure.The lateral extent of the model is limited only to the invasive zone, and time-varying reservoir exposure is used to simulate the acts of drilling, tripping, completions and workovers. Extremely fine, core-scale grids are used to capture saturation and pressure in the invasion zone. Special core tests using a specially-designed core holder are conducted on the subject reservoir core.Test results are interpreted to obtain an estimate of end-point relative permeabilities at irreducible saturation, dynamic mud cake effect on filtrate loss, and impact of solids invasion on return permeability. Both overbalanced and underbalanced tests are conducted with different drilling fluids. The tests are used to describe the mud cake effect in the invasion model. The saturation and pressure profiles from this model are then used as initial conditions in a sector-scale simulator with near-wellbore fine-gridding to model flow-back effects.Absolute permeability damage is modeled using the core test results as an incremental and hyperbolically recovering effect during flow-back simulations. A near-wellbore fine grid overlay is used to capture the near wellbore effects from the micro-simulator results. Several sensitivities, including initial reservoir pressure, degree of overbalance (during drilling) and drawdown (during production), heterogeneity, anisotropy, and mud cake effect are examined.Equivalent skin factors that vary with time and depth are developed to enable comparison with full-field simulations. A horizontal well example is used to illustrate the results of the study. Results illustrate stark and often under-appreciated effects of invasive damage on flow-back and therefore on production performance. The methods described in this work can be used in reservoir-specific studies to model formation damage and aid in the selection of mud types, drilling techniques and remediation methods required to improve performance. It is hoped that this work bridges the typically empirical damage characterization methods with dynamic reservoir simulations.
The Dry Coal Anomaly – The Horseshoe Canyon Formation of Alberta, Canada
Authors: Hoch O. 
Published: December 2007

Abstract
The Horseshoe Canyon coal formation in Alberta, Canada is an anomaly for coals. It is dry, for the most part producing no formation water. Therefore, no dewatering is required. In fact, it is severely damaged by water influx. Normal permeability injection tests and conventional hydraulic fracturing techniques, even foams, have been unsuccessful in this environment. The best part of this reservoir has an areal extent in excess of 12,000 square miles containing 1-2 BCF per square mile of recoverable gas. Commercial development of this resource is a very appealing prospect.
Numbers of coal seams vary from 5 to 30 per well, spread out over 600 – 1,300 ft. Individual seam thicknesses vary from 1 to 13 ft. Most seams are discontinuous over a large area. The better part of the formation has permeability in the range of 1 – 100 md. This makes it difficult to avoid damaging the formation during drilling and cementing operations, hence some type of stimulation is required.
Nitrogen hydraulic fracturing is the only stimulation process that has had any success in this formation to date. The treatments involve pumping nitrogen at high rates, without proppant, through coiled tubing (CT) and a selective cup-type packer (SCP), isolating each coal seam while treating it. Bottomhole treating gradients vary greatly with an average of approximately 2.2 psi/ft.
Whether these nitrogen treatments are in fact fracturing the formation or just having the damage flushed out has been a matter for speculation. Over 1,600 wells have been treated in this way and more continue to be added on an everyday basis.
This paper describes the formation characteristics and geology of the Horseshoe Canyon coal and presents case histories of hydraulic fracturing treatments performed including production results.
Dynamic Petrophysics-Applications of Time-Lapse Reservoir Monitoring in Saudi Arabia
Authors: Ma S. M. , Al-Hajari A. A. , Kelder O. , Al-Muthana A. S. , Srivastava A. , Ramamoorthy R. 
Published: December 2007

Abstract
In reservoir management, accurately measuring remaining oil saturation and monitoring its change with time are conducted with time-lapse reservoir monitoring, including production logs and reservoir saturation logs.Interpreting these reservoir-monitoring logs requires advanced knowledge of multi-disciplines in petroleum engineering.Formation evaluation is dynamic, and data integration is a critical step of the evaluation.Dynamic petrophysics provides the basis for engineers to make critical reservoir-management decisions, such as water shut-off.
In this paper, examples of time-lapse reservoir monitoring are shown to demonstrate the concept of dynamic petrophysics for a well, from initial openhole formation evaluation to intermittent and late-stage, time-lapse reservoir monitoring.All reservoir-monitoring logs were run through production tubing and logged across openhole or casedhole reservoir intervals. Formation water salinity, mixed with different injected waters, was characterized with bottomhole and surface samples.Resistivity logs were interpreted considering both drainage and imbibition petrophysics.Resistivity and carbon-oxygen logs were integrated to provide final oil saturation. Results of this study show that residual oil in water-swept intervals is very low, indicating excellent sweep.
In summary, dynamic petrophysics, based on time-lapse reservoir monitoring, is the basis of reservoir management. Integration of petrophysical, geological, reservoir, and production data is the key to successful dynamic reservoir diagnostics.
Predicting Pump-Out Volume and Time Based on Sensitivity Analysis for an Efficient Sampling Operation: Prejob Modeling Through a Near-Wellbore Simulator
Authors: McCalmont S. , Onu C. , Wu J. , Kiome P. , Sheng J. J. , Adegbola F. , Rajasingham R. , Lee J. 
Published: December 2007

Abstract
Recently, advanced wireline formation testers are being utilized to obtain clean formation samples more often than in the past. Because obtaining clean samples requires a long pumping operation, knowing the required pump-out volume and time for the given formation condition is very important for an efficient and safe operation. This paper shows an application of a new near wellbore simulator to prejob modeling of sampling jobs to assist selecting sampling depth, pumping rate, and minimum-required time and volume to reach a target contamination level.
Advanced formation testers are equipped with sensors that can distinguish the formation hydrocarbon from mud filtrate. The operation may require extended pumping, which may cause problems like tool sticking, mud weight control, inefficient or prohibitive pumping time, or a slim possibility of good samples due to deep invasion. These problems are more pronounced in deep, extended reach wells offshore where rig costs are high. Therefore, careful planning is required to obtain clean formation samples, either hydrocarbon or water. It is especially important for sampling of formation oil when oil-based mud or synthetic mud is used.
To facilitate optimum sampling operations, a newly developed near wellbore simulator is applied for a prejob modeling sensitivity analysis. The simulator is based on a black oil reservoir simulator and can handle a three dimensional, multi-phase flow in the near-wellbore area by incorporating wellbore and formation tester tool factors. Under the given formation parameters of porosity, capillary pressure, and relative permeability, the effects of permeability, anisotropy, formation thickness, pumping rate, probe depth relative to the formation thickness, and invasion depth are investigated.
Field application results for a gas condensate sampling and a formation water sampling are presented in the paper. The pump-out volume and time under various formation conditions to reach a 5- percent contamination level were estimated during the prejob planning stage, and a near infrared spectrometer sensor was used for fluid identification in the actual pumping operation. The prejob modeling results match very well with the sensor responses and the laboratory analysis results further confirm the excellent sample quality with very low contamination. The success of the sampling operation demonstrated the benefits and importance of the well planned, prejob modeling work.
Influx of Advanced Drilling Technologies Maximizing Productivity of Mature Region
Authors: Simonton S. , Seigrist L. , Huizenga Robert , Janwadkar S. , Isbell M. 
Published: December 2007

Abstract
Economical development of oil and gas reserves in Kiowa and Washita counties of Southwestern Oklahoma requires drilling complex structural features with faulted formations and highly dipping beds.To address these challenges, many operators employ packed hole and/or conventional directional motor assemblies to keep inclination to a minimum drilling the production section.While this type of bottom hole assembly has improved directional control, in many cases it still leads to unacceptable angle building tendencies (ie bit walk) and high dogleg severity.This type of BHA has also led to poor vertical hole quality resulting in additional directional issues in subsequent hole sections.In addition, the conventional directional assembly increases well costs due to multiple deviation correction runs with different BHA configurations resulting in more flat time, lower cumulative bit penetration rate, and more bits/runs per hole section.
To reduce drilling costs and maximize production in the region, a service company conducted a detailed analysis of drilling performance, mud logs and wireline data from offset wells. The in-depth study helped engineers identify key problems limiting drilling performance.This led the operator to set new objectives for the production hole section of achieving the highest possible rate of penetration while maintaining a near-vertical wellbore.An implementation strategy was outlined that had two main components including a vertical deviation control system and new PDC bit technology.
This strategy has been implemented to drill 17 wells with excellent results (Operator had previously drilled over 55 wells in the area with the old BHA).The new BHA combination has minimized directional deviation (inclination) and reduced dogleg severity.It has also reduced torque and drag helping deliver a smooth, high quality wellbore and has totally eliminated costly correction runs and increased efficiency and quality of cementing operations.This has allowed the operator to log and set tubulars without incident.
Application of a New Grain-Based Reconstruction Algorithm to Microtomography Images for Quantitative Characterization and Flow Modeling
Authors: Thompson K. E. , Willson C. S. , White C. D. , Nyman S. , Bhattacharya J. , Reed A. H. 
Published: December 2007

Abstract
X-ray computed microtomography (XMT) is used for high-resolution, non-destructive imaging and has been applied successfully to geologic media. Despite the potential of XMT to aid in formation evaluation, currently it is used mostly as a research tool. One factor preventing more widespread application of XMT technology is limited accessibility to microtomography beamlines. Another factor is that computational tools for quantitative image analysis have not kept pace with the imaging technology itself.
In this paper, we present a new grain-based algorithm used for computer reconstruction and analysis of granular materials (e.g., consolidated or unconsolidated sands) and subsequent network generation. The algorithm differs significantly from other methods because the first step is to extract the fundamental granular structure from a 3D data set, which provides a wealth of information such as grain sizes, aspect ratios, orientations, surface areas, etc. Knowledge of the basic granular structure serves as a foundation for characterizing the void morphology and creating physically representative pore networks. The algorithm is applied to a sample of sandstone from the Frontier Formation in Wyoming, USA, which was imaged using synchrotron XMT. Morphologic and flow-modeling results are presented.
Network Modeling of Drainage and Imbibition in Microfractured Porous Media
Authors: Wilson R. , Rodríguez F. 
Published: December 2007

Abstract
This paper investigates two-phase flow in microfractured porous media. We obtain relative permeabilities and capillary pressure curves for drainage and imbibition processes using a two-dimensional microfracture network model. The system of microfractures is composed of interconnected parallel plates of varying apertures, lengths and pre-established orientation.
Fluid flow in each microfracture unit is described by the paralle plate flow model. Capillary pressure for individual microfractures is obtained as a function of fracture aperture. The model takes into account capillary and viscous forces, thus the model allows for the analysis of different configurations of fluids on the network obtained with different capillary numbers and viscosity ratio. Relative permeabilities and capillary pressures are obtained as a function of the average saturation of the fluids in the network and the effect of different flow conditions on these curves is presented.