bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modeling Conformance as Dispersion
Authors: Coats K. H. , Whitson C. H. , Thomas L. K. 
Published: December 2007

Summary
For decades the effect of physical dispersion (in-situ mixing) in porous media has been of interest in reservoir engineering and groundwater hydrology. Dispersion can affect the development of multi-contact miscibility and bank breakdown in enriched gas drives and miscible solvent floods of any mobility ratio.
The magnitude or extent of dispersion is quantified by the rock property physical dispersivity (α) which is the order of 0.01 ft for consolidated rocks and several times smaller for sand-packs, from many laboratory measurements.
Numerical studies of the effect of dispersion on enriched gas drives and field tracer tests often use input values of dispersivity 100 to 1000 or more times larger than ~0.01 ft. These large input dispersivity values stem from large apparent dispersivities (αa) determined by matching the one-dimensional convection-diffusion (1D CD) equation to production well effluent tracer concentration profiles observed in field tracer tests.
The large apparent dispersivities reflect conformance or other behavior not governed by the 1D CD equation and should not be used to justify large physical dispersivity as input to numerical studies. This paper shows that large apparent dispersivities observed in field tests can result with physical dispersivity no larger ~0.01 ft lab-measured value.
Heterogeneity alone (no physical dispersivity or molecular diffusion) causes no in-situ mixing and cannot explain observed large apparent echo dispersivities. Large apparent echo dispersivities for two reported field tracer tests are shown to result from the effect of drift alone with no dispersion.
The widely reported scale-dependence of apparent dispersivity is a simple and necessary consequence of mis-applying the 1D CD equation, with its single parameter of Peclet number L/α, to conformance it does not describe. Apparent dispersivity is scale-dependent but physical dispersivity is a rock property independent of scale and time.
Maximizing Effective Proppant Permeability under High-Stress, High Gas-Rate Conditions
Authors: Dusterhoft Ron , Nguyen Philip , Conway Mike 
Published: December 2007

Abstract
Work reported in this paper shows that fracture-pack permeability and conductivity are impacted by the mobility of formation-generated fines plugging under high-stress and high gas flow-rate conditions. The authors examine two approaches to (1) prevent formation fines from entering the proppant pack and (2) provide higher sustained fracture-pack permeability and conductivity under severe production conditions. The paper further shows that significant improvements can be obtained in both the short term and the long term, and how these improvements can be used to provide sustained gas production.
The results of laboratory testing are reviewed in detail, including the mechanisms by which fines are immobilized and the conductivity is maintained. The mechanisms involve an on-the-fly, direct coating of proppant with surface- modification agents (SMA) just before the proppant is blended with the carrier fluid. The chemical properties of the SMA can be varied widely to meet downhole conditions and production flow rates. The treatment renders the formation sand and fines immobile so that migration and plugging do not occur. In addition to fines stabilization, SMA can be formulated using liquid resin to consolidate the proppant pack, making it useful in controlling proppant flowback at high production rates, and in providing long-term pack stability. The effects of non-darcy flow are also examined and compared to baseline data.
Field studies are reviewed to evaluate how actual productivity can be affected, both short-term and long-term, by controlling fines damage to provide long-term fracture conductivity.
Multicomponent Processing and Fracture Characterization Analysis at Pinedale Field and Washakie Basin, Wyoming
Authors: Gaiser James E. , Van Dok Richard R. 
Published: December 2007

Abstract
Multicomponent 3-D surveys provide a practical means for analyzing fracture properties where downgoing compressional (P) waves convert to upgoing shear (S) waves at interfaces. The unique characteristics of S-wave azimuthal anisotropy induced by vertical fracturing may provide valuable information for delineating naturally fractured reservoirs and monitoring production performance. In the presence of fractured media, S-waves split into a fast wave that is polarized parallel to fractures and a slow wave that is polarized normal to fractures. The amount of splitting (time difference between the two S-waves) is proportional to fracture intensities. To investigate this phenomenon, we utilize a wide range of source-receiver azimuths in the processing and analyze the fast and slow S-waves to extract fracture information.
Two 3D three-component (one vertical and two horizontal geophones) surveys from Wyoming are presented: one acquired over the southern tip of the Pinedale Field in the Antelope area and the other in the Washakie Basin. The targets are naturally fractured gas sand reservoirs. From the analysis of fast and slow S-waves, the same regional direction of anisotropy was observed in both areas. Layer-based analyses measured anisotropy in the overburden, which required compensation during the processing to isolate the variations at reservoir depths. Eight limited-azimuth volumes were created for the two horizontal geophone components. These volumes were analyzed to determine the time-variant anisotropy within the surveys and the volumes indicated areas of increased fracturing in the overburden as well as at target levels.
Practical Optimization: Working with the Realities of Decision Management
Authors: Haskett William , Better Marco , April Jay 
Published: December 2007

Abstract
Portfolio management tools are designed to aid senior management in the development and analysis of portfolio strategies, however, most of the commercial portfolio optimization packages are relatively inflexible. Most are not able to answer the key questions posed by senior management. Additionally, most senior managers are unfamiliar with the power and advantages provided by a true comprehensive portfolio tool. In order for management to make decisions and to set strategic objectives, these portfolio tools must first provide practical, goal oriented output. This output must be applicable and directly pertinent to the decisions and issues faced by company. The output must provide information that allows decisions to be made that take into account optimization of all scarce resources in the context of the evolving longer-term portfolio.
Practical portfolio optimization requires the efficient spending of all scarce resources: Capital, Time, and Human Resources. A real data set is used to show the results of different ranking and optimization methods, from Markowitz to Meta-heuristics, for a portfolio having prospects at various stages of maturity. The prospects transition along a development path from "pre-identified lead" stage to "targeted effort" stage and then on to "capital allocated" stage where they prove success and capture value. It is vital that this evolution of prospects be captured in any optimization method.
The example portfolio includes optimization of technical and business development personnel. The inclusion of personnel cycle time (varied by functional area), spin-up, and skill set development enables optimal human resource management within the context of longer-term strategy implementation and risk balanced value maximization. Disconnecting the time dependent prospect generation and acquisition activities from the optimal portfolio composition may provide the optimal mix now at the expense of the future prospect development cycle. The preferred optimization methodology must be able to handle strategic business search activities as a portion of the portfolio even though these activities are seldom rigorously quantifiable.
Frequency Dispersion Effects on LWD Shear Sonic Measurements in Acoustically Slow Environments
Authors: Haugland S. Mark 
Published: December 2007

Abstract
This paper presents a study of the sensitivity of LWD shear velocity estimates in acoustically slow environments to the parameters that govern the dispersive borehole-guided waves from which the shear slowness is estimated. This type of analysis is useful for assessing the relative importance of various algorithm parameters and to bound the accuracy of an LWD slow shear wave log given bounds on the accuracy of the parameters associated with the dispersion correction algorithm.
It is assumed that the slowness of a given borehole-guided wave is known. Any errors in the associated shear slowness estimate are ascribed to uncertainty in the parameters that govern the slowness of the borehole-guided wave, and are not associated with individual logging devices and waveform processing algorithms. The possibility that a mode is misregistered is also considered by examining shear slowness errors that result from processing a given mode under the assumption that it is a different mode. This issue seems to be acknowledged in the literature, where some LWD sonic devices have been characterized by terms such as "pseudo-dipole" and "pseudo-monopole."
The analysis is based on a new analytical forward model suitable for calculating the dispersion of borehole-guided waves such as Stoneley, flexural, and screw waves even in the presence of an eccentered metallic mandrel. When the mandrel is eccentered, the flexural and screw modes each split into two unique modes. One mode is referred to as a fast mode and the other is referred to as a slow mode.
Over the parameter range considered in this paper, the fast flexural mode and both of the screw modes appear to be superior to the slow flexural and Stoneley mode when the mandrel is eccentered.
Dual-Energy CT-Scanning Applications in Rock Characterization
Authors: Siddiqui Shameem , Khamees Aon A. 
Published: December 2007

Abstract
The use of dual-energy CT-scanning for evaluating reservoir rocks is not a new technique. It involves scanning the same location within the rock twice, using a different X-ray energy each time. Wellington and Vinegar, in a 1987 paper stated that one image proportional only to bulk density and another proportional to atomic number can be obtained by scanning the sample at high (above 100 kV, Compton scattering dominant) and low (well below 100 kV, Photoelectric absorption dominant) X-ray energies. They generated CT slices showing density and atomic number variations. Although dual-energy scanning has been used quite successfully in fluid flow visualization studies, especially in the case of three-phase flow, its use has been limited in the field of petrophysical core characterization. Part of the problem is due to the unavailability of appropriate software and procedures to generate the bulk density and atomic number images from the high and low-energy CT data and part is due to the lack of necessary steps to utilize the density and atomic number data to characterize the cores. Commercially available software can now allow generating the density and atomic number images from the dual-energy data. This paper describes some techniques to utilize the density and atomic number data to better characterize the reservoir rocks. This technique was first applied to small plug samples of known petrophysical properties for validation purposes. After that, it was applied to a 60 ft-long section of preserved core from an Upper Jurassic carbonate reservoir in Saudi Arabia, which was CT-scanned at two different X-ray energies at 5 cm (2 inch) intervals. Interesting qualitative results were obtained that can improve our understanding of the carbonates. This paper also shows step-by-step instructions for calculating porosity values from the approximate mineral compositions.
The Significance of Non-Darcy and Multiphase Flow Effects in High-Rate, Frac-Pack Gas Completions
Authors: Lolon E. P. , Chipperfield S. T. , McVay D. A. , Schubarth S. K. 
Published: December 2007

Abstract
Hydraulic fracturing combined with gravel packing in high-permeability gas reservoirs (frac-packing, or F&P) is currently considered the most reliable completion technology for offshore Gulf of Mexico (GoM) completions. Such treatments are designed to bypass damage near the wellbore and prevent formation sand production. Despite the relative maturity of this technology, there has been insufficient focus on non-Darcy flow, particularly in the fracture, in F&P wells in the literature.
Previously published work, based on single-phase inflow equations, acknowledged that a very high pressure drop exists near the wellbore in F&P completions, but this has been usually attributed to a limited number of effective perforations. In this work, we used reservoir simulation and an inflow equation for pressure drop across the perforation tunnels to quantify the relative pressure drop contributions in the reservoir, fracture, and gravel pack system. We considered both non-Darcy and multiphase flow in our evaluation.
We found that non-Darcy flow in the fracture and perforation tunnels results in substantial near-wellbore pressure drops for typical F&P gas wells with gas rates greater than 0.2 to 3 MMscf/D/ft. Increasing fracture conductivity and fracture lengths and using proppants with lower non-Darcy flow coefficients can help in reducing non-Darcy pressure drops and optimizing F&P completions.
Deepwater DST Planning and Operations From a DP Vessel
Authors: Stomp Robert J. , Fraser Graham J. , Actis Stephen C. , Eaton Luke F. , Freedman Kerry C. 
Published: December 2007

Abstract
ConocoPhillips (COPC) is developing the Magnolia field with a Tension Leg Platform (TLP) in 4674 feet of water at Garden Banks (GB) block 783 in the Gulf of Mexico (GOM). The field was discovered in 1999 and appraisal wells were drilled in 2000 and 2001. Field development approval was obtained in 2001. The approved depletion plan and well construction strategy included drilling and casing wells prior to the installation of the TLP (pre-drilling), pre-completing and testing one well during the pre-drilling program, and completing the remaining wells from a completion rig installed on the TLP.
The GB783 A2ST3BP1 well was successfully drill-stem tested (DST) from the Ensco 7500 dynamically positioned (DP) semi-submersible drilling vessel in June 2003 as part of the Magnolia field development. The pre-completion and DST operations overcame a number of challenges which included the frac-packing of a thick, fine-grained interval, and well testing from a DP semi-submersible drilling rig while simultaneously transferring produced hydrocarbons to a transportation barge moored to the rig.
The objectives of the pre-completion/DST were to plan and execute the operations safely, validate the sand control design, determine well performance and reservoir properties, and verify the effectiveness of the completion procedures prior to the TLP rig completion program.
This paper will focus on the extensive planning process and the operational aspects of performing a DST in a deepwater environment.
An Experimental and Numerical Investigation of Crossflow Effects in Two-Phase Displacements
Authors: Cinar Y. , Jessen K. , Berenblyum R. , Juanes R. , Orr F. M. 
Published: December 2007

AbstractIn this paper we present flow visualization experiments and numerical simulations that demonstrate the combined effects of viscous and capillary forces and gravity segregation on crossflow that occurs in two-phase displacements in layered porous media.We report results of a series of immiscible flooding experiments in two-dimensional, two-layered glass bead models. Favorable mobility ratio imbibition and unfavorable mobility ratio drainage experiments were performed. We used preequilibrated immiscible phases from a ternary isooctaneisopropanol- water system, which allowed control of the interfacial tension (IFT) by varying the isopropanol concentration. The experiments performed had a wide range of capillary and gravity numbers. The experimental results illustrate the transitions from flow dominated by capillary pressure at high IFT to flow dominated by gravity and viscous forces at low IFT. The experiments also illustrate the complex interplay of capillary, gravity, and viscous forces that controls crossflow. The experimental results confirm that the transition ranges of scaling groups suggested by Zhou et al.7 are reasonable.We report also results of simulations of the displacement experiments by two different numerical techniques: finite difference and streamline methods. The numerical simulation results agreed well with experimental observations when gravity and viscous forces were most important and less well for capillary-dominated flows.
Quantification of Hydrocarbon Saturation in Carbonate Formations Using Simultaneous Inversion of Multiple NMR Echo Trains
Authors: Fang Sheng , Chen Songhua , Tauk Raj , Fornage Philippe , Georgi Dan 
Published: December 2007

Abstract
Simultaneous inversion of multiple echo trains (SIMET) is a technique for processing and interpreting Nuclear Magnetic Resonance (NMR) log data that exhibit relaxation, polarization, and/or diffusion contrasts. SIMET is a forward-modeling-based inversion technique that utilizes known correlations between NMR responses and fluid properties, thereby reducing the parameter space dimensions and consequently improving fluid volumetrics and saturation estimates. It is robust when relaxation, polarization, and diffusion contrasts between the fluids are large. However, it is more challenging when the contrasts are small or only a limited amount of different TE (inter-echo time) and/or TW (wait-time) data is available. In such cases, it is especially critical to consider secondary effects, such as those attributable to restricted diffusion or internal gradients. Such information can be added as a prior constraint. An NMR log example is used to illustrate the necessity of correcting for the restricted diffusion effect so that correct oil and water intrinsic relaxation time distributions can be derived, which is the key to the improvement in the final interpretation. For the example, the fluid saturations and viscosity estimated with the SIMET processing are confirmed by the production data.
Determination of Arps' Decline Exponent From Gas Reservoir Properties, and the Efficacy of Arps' Equation in Forecasting Single-Layer, Single-Phase Gas Well Decline
Authors: Voelker Joe 
Published: December 2007

Abstract
This paper presents conclusions as to the ability of Arps’ rate-time decline equation1 to predict boundary dominated gas well rate decline. A correlation of Arps equation parameters, to initial and boundary reservoir conditions, is also presented, enabling the equation to be used to forecast gas well production rates, prior to first production.
The conclusions are derived from a numerical study, consisting of 39 radial flow simulations. The simulations predicted rate declines, against constant bottomhole well pressures, in a single-layer, single-phase, bounded, volumetric gas reservoir model.
The 39 simulations include initial reservoir pressures ranging from 1000 to 10000 psia, flowing bottomhole well pressures from 100 to 7500 psia, and gas gravity from 0.56 to 0.8.
The approach is semi-analytical in that the non-linear differential equation that describes the process, is linearized with a function that approximates the change in viscosity-compressibility product in dimensionless time. The function is integrable and thereby directly yields a closed form solution, of which the Arps equation is a particular case.
The coefficients of the function, which are the Arps parameters, as well as coefficients in a generalized form of Arps’ equation, were optimized to generate rate declines that matched those from the simulation models. Correlation to reservoir and well conditions was then constructed.
It is concluded that Arps’ equation adequately predicts constant pressure, gas well rate decline, over the entire range of conditions enumerated above.
It was also found that Arps’ decline exponent is correlated to reservoir, well, and gas properties. The correlation is aided by Carter's Drawdown Parameter,2 and under certain conditions, the Arps decline exponent is a simple linear function of Carter's Drawdown Parameter.
A determination of the decline exponent from initial reservoir and well conditions, allows the field engineer to forecast depletion (boundary dominated) gas well decline rates, for wells producing against constant bottomhole pressure, without historical decline. The closed form equation precludes the need for reservoir simulation, or specialized commercial software.
The procedure for gas well forecasting using these results is demonstrated.
Analysis of Efficient High-Power Fiber Lasers for Well Perforation
Authors: Gahan Brian C. , Batarseh Samih , Sharma Bhargav , Gowelly Sherif 
Published: December 2007

Abstract
According to many in the laser industry, fiber lasers are now a serious alternative to solid-state and carbon dioxide lasers for industrial material-processing applications. Over the past two years, commercially available fiber lasers have increased in power from several watts to kilowatts. They are now capable of efficiently delivering requisite power via fiber optics to targets downhole, and have rapidly evolved into the leading candidate for on-site applications in well construction and completion. When compared to conventional industrial lasers, fiber lasers offer an order of magnitude greater wall plug efficiency, better beam quality, increased mobility due to their considerably smaller footprint, and essentially maintenance-free operations over their lifetime. Their use as an alternative method to conventional explosive charges could reduce or eliminate perforation damage and significantly boost production rates, cumulative production and overall economic returns.
Since 1997, GTI and its research partners have investigated the application of high-power laser energy for well construction and completion. Early qualitative investigations were performed utilizing weapons-grade military "Star Wars" lasers to demonstrate well construction feasibility. A more quantitative approach followed applying early 1990's laser technology to determine the energy required to break various rock lithologies. Beginning in 2003, GTI advanced its downhole perforation application research using the most recent evolution of high-power lasers: a 5.34 kW Ytterbium-doped multiclad fiber laser.
This paper will provide a description of the fiber laser system, experimental procedures and data analysis used for perforation applications on rock samples. Experiments focus on improvements to rock properties and rock removal efficiency targeting a one foot cube of Berea sandstone. Results from this test will also determine that megawatt-class "Star Wars" military lasers are not required to achieve improvements in near- tunnel permeability. High-power fiber lasers represent a recent technological breakthrough upon which a rugged, deployable system for non-explosive wellbore perforations can be based.