bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the Calculation and Interpretation of NMR Relaxation Time Distributions
Authors: Dunn Keh-Jim , LaTorraca G. A. , Warner J. L. , Bergman D. J. 
Published: December 2007

ABSTRACT
We analyzed NMR relaxation time data using a multi-exponential model. The inversion of NMR data using such a model is an ill-posed problem. The answer is often not unique and requires subjective judgement We studied two methods of regularization. One uses norm smoothing based on an article by Butler et al. We found that optimal norm smoothing depends on the input of measurement errors. The second method uses curvature smoothing which minimizes variations in the second derivative. The latter is more effective for suppressing fluctuations in the relaxation time distribution, but doesn’t directly account for data quality. We studied NMR T1 data at full and partial saturations with desaturation pressures ranging from 15 to 400 psi (air/brine). As a general guideline, we found that the relaxation time cutoff which corresponds to irreducible water saturation is about 33 ms. For a limited number of samples, we found that the T1 relaxation time distribution has very little dependence on the frequency from 200 down to 1 MHz. We also found that T2 could be correlated to permeability.
NMRI Characterization of Fractures and Multiphase Transport in Fractured Porous Media
Authors: Chen Songhua , Yao Xiaoli , Qiao Jinli , Watson A. T. 
Published: December 2007

Abstract
The use of nuclear magnetic resonance imaging (MRI) for characterizing fractures and flow in fractured media is investigated. A relaxation-weighted imaging technique is developed and demonstrated for use with fractured porous media. The new technique can be used to selectively highlight either fracture or porous matrix regions. Considerable advantages over standard spin-density techniques for characterizing fractured media are demonstrated. Its use to speed image acquisition is also demonstrated. MRI technique is also used to monitor imbibition and drainage displacement experiments in fractured porous media. Multislice images show that the fractures can have profound effects on the fluid distributions in multiphase flow.
Pressure-Transient Behavior for a Horizontal Well Intersecting Multiple Random Discrete Fractures
Authors: Guo Genliang , Evans R. D. , Chang Ming Ming 
Published: December 2007

ABSTRACT
New analytical pressure-transient solutions for a horizontal well intersecting multiple random discrete fractures in both an infinite and a bounded reservoir are presented. The horizontal well is assumed to penetrate multiple randomly distributed vertical fractures. The infinite reservoir containing the horizontal well is bounded at the top and at the bottom. For the case of a bounded reservoir, all exterior boundaries are non-flow boundaries. New source functions for a random vertical fracture are first derived. The pressure-transient solutions are then obtained using the derived source functions, as well as superposition principles. A uniform flux is assumed along all fracture faces. An averaging technique is used to approximate the wellbore pressure.
The new solutions provide a theoretical basis for the analysis of the pressure transient behavior of a horizontal well intersecting multiple random discrete fractures. Different flow regimes are identified. The effects of fracture characteristics, such as fracture orientation and length, on the pressure transient behavior of a horizontal well are investigated. New evaluation techniques using the derived pressure-transient solutions can be developed to determine reservoir properties and fracture characteristics from horizontal well test data.
New Insights in Pressure-Transient Analysis for Stress-Sensitive Reservoirs
Authors: Zhang M. Y. , Ambastha A. K. 
Published: December 2007

Abstract
Deep-seated low-permeability petroleum or geothermal reservoirs usually exhibit stress-sensitive permeability. For such reservoirs, pressure-transient analysis based on constant rock properties, especially permeability, can lead to significant errors in parameter estimation. Recently, an approximate analytical solution has been published to analyze pressure-transient tests in stress-sensitive reservoirs using the concept of "permeability modulus". However, because of the non-linear character of the partial differential equation for stress-sensitive reservoirs, application of superposition to model buildup tests is not straightforward.
Using the concept of "permeability modulus", this study presents numerical solutions for stress-sensitive reservoirs. Pressure transient solutions with wellbore storage, skin, permeability modulus, and outer boundary effects have been studied in detail. Both drawdown and buildup solutions have been investigated. Solutions presented in this study also include multiple permeability modulus values for a given situation, where permeability modulus changes with respect to stress level in the reservoir in a stepwise mode.
This study has pointed out inaccuracies involved in previous analytical solutions, especially for wellbore storage and skin effects, and buildup tests. Previously, it has been stated that stress-sensitive permeability effects can cause wellbore storage early-time unit slope line to be masked. This investigation shows that, irrespective of the severity of stress sensitivity, wellbore-storage-dominated unit-slope line always appears at early time. We also show that the use of multiple permeability modulus values to study pressure-transient analysis for stress-sensitive reservoirs is consistent with available laboratory measurements of permeability as a function of stress.
Improving Formation Evaluation by Resolving Differences Between LWD and Wireline Log Data
Authors: Jackson C. E. , Heysse D. R. 
Published: December 2007

Abstract
Wireline logs and logging-while-drilling (LWD) logs are important pieces of the formation evaluation puzzle. They are often the basis for the initial economic evaluation of a prospect and serve as references for monitoring reservoir depletion. As the data from the LWD devices approaches wireline quality, it becomes feasible for oil companies to consider replacing wireline data with LWD data.
Unfortunately, these logs are not directly interchangeable. In addition to differences in basic tool responses, changes in logging environment between LWD and wireline logging runs can cause significant variation between similar measurements (resistivity, density, neutron, gamma ray) that affect subsequent reservoir evaluation. The importance of resolving these differences cannot be overemphasized. Small errors in petrophysical parameters can result in a multimillion dollar difference in the calculation of economic reserves.
This examination of the differences between LWD and wireline logs and consideration of how these differences affect formation evaluation focuses on the following topics: Differences in sensor physicsBasic reference standardsEnvironmental correctionsFiltrate invasion effectsFormation alteration
The outcome is a consistent procedure for making meaningful comparisons between these logs.
Case Histories of MWD and Wireline Density Log Comparisons: An Improved Understanding of Density Log Response
Authors: Spross R. L. , Ball M. S. , Zannoni S. A. 
Published: December 2007

Abstract
With the advent of Measurement-While-Drilling (MWD) density tools in 1987, a new alternative to wireline for obtaining formation bulk density was introduced. As with any such introduction and evolution, comparative evaluations were made in order to assess the quality and quantitative nature of the MWD density data.
Analysis of MWD and comparable wireline density data show that the two can have different responses for several reasons. These include differing instrument designs, different logging environments, and evolving reservoir conditions. MWD and wireline density responses may also differ due to standoff, mudcake, mud density, hole rugosity, drilling dynamics, formation exposure time, and time dependent invasion profiles. Comparative evaluations show that without careful analysis, mis-interpretation of the data can frequently occur.
The ability to obtain and understand quantitative MWD density data greatly enhances the value of Formation-Evaluation-While-Drilling (FEWD) with resulting well cost savings and increased operational efficiency. While a case may be made for wireline replacement applications, it is often true that obtaining data in the MWD and wireline time domains may provide complementary views of changing reservoir conditions thereby enhancing the characterization of the reservoir.
Stochastic Description of Multiphase Flow in Heterogeneous Porous Media
Authors: Chang Y. C. , Mohanty K. K. 
Published: December 2007

Abstract
Typical field simulation grid-blocks are internally heterogeneous. The objective of this work is to scale-up multiphase flow properties of field simulation grid-blocks from core-scale properties and represent them by flow equations involving stochastic terms, if necessary. Heterogeneity is modelled here as a correlated random field parameterized in terms of its variance and two-point variogram. Variogram models of both finite (spherical) and infinite (fractal) correlation length are included as special cases. Local core-scale porosity, permeability, capillary pressure function, relative permeability functions, and initial water saturation are assumed to be correlated. Capillary pressure and relative permeability hysteresis are modelled at the core-scale. Water injection is simulated and effective flow properties (not pseudo-functions) and flow equations are calculated. Conditions under which stochastic terms are necessary and the form of the stochastic term are identified. For strongly water-wet media and small variance in permeability, flow can be described by an effective relative permeability without including a stochastic term. A stochastic term is, however, needed to describe multiphase flow in water-wet grid-blocks of large permeability variance; effective relative permeabilities can describe the average front movements. In fractal media, effective relative permeabilities cannot even describe the average front movements. In oil-wet systems, the saturation front movement is less stabilized and has more fluctuations than similar water-wet cases.
The Effects Of Sedimentary Heterogeneities On Production From A Shallow Marine Reservoir - What Really Matters ?
Authors: Kjønsvik Dagrun , Doyle James , Jacobsen Torgrim , Jones Alistair 
Published: December 2007

ABSTRACT
This paper investigates the impact of sedimentary heterogeneities on performance of waterflooding in shallow marine reservoirs. Reservoir simulation models are developed from detailed geological models based on a four-level sedimentary architectural hierarchy ranging from sedimentary structures (wave ripples, hummocky cross-stratification) up to parasequences. Single- and two-phase flow properties are upscaled to capture the effects of small scale heterogeneities on performance. The relative influence of 12 heterogeneity factors is determined using experimental design and analysis of variance. The analysis identified large scale features (parasequence thickness and stacking patterns) to be of primary importance for waterflood performance. These features control the relative proportion of fades belts in the reservoir, which correlates with recovery. Other important, though secondary, heterogeneities include interfingering of facies belts, and small scale bedding.
New Correlations To Predict Non-Darcy Flow Coefficients at Immobile and Mobile Water Saturation
Authors: Frederick D. C. , Graves R. M. 
Published: December 2007

Abstract
Several empirical correlations were developed relating the inertial, sometimes called the non-Darcy flow, coefficient (β) to permeability, porosity and water saturation. The correlations were developed using 407 data points taken on 24 cores over confining stress which was varied from 1000 psi to 5000 psi. The permeability range investigated was from 0.00197 to 1230 md. Previously published work1 on proppants extend the correlation to 350,000 md with a coefficient of determination of 98%. Water saturation has a significant effect on the coefficient. Confining stress effects are accounted for in the porosity and permeability values which decrease at elevated stress.
The Influence of Stress Anisotropy on Horizontal Well Performance Predicted Via Special Core Analysis Under True Triaxial Conditions
Authors: Crawford B. R. , Smart B. G. D. 
Published: December 2007

Abstract
For optimisation of recovery, a thorough understanding of reservoir heterogeneity and anisotropy on as detailed a scale as possible is a prerequisite. Despite recent developments in probe permeametry enabling quantification of sedimentary heterogeneity down to the lamina-scale, no parallel advance has been evident in the field of core analysis with regard to improving the realism of the applied stress field. The conventional "triaxial" method can only achieve vertical stress anisotropy and is limited to axisymmetric uniform radial pressure. Thus it is incapable of adequately simulating the in situ rock stress field, σv≠σH≠σh. Accordingly, a new true triaxial cell and servo-control system has been developed which is capable of applying independent and unequal radial stresses to the curved surface of a cylindrical core plug. Pulse decay permeability experiments have been conducted on three reservoir sandstone analogues showing different degrees of geological heterogeneity. Permeabilities were measured under both true triaxial and conventional "triaxial" conditions, for the purposes of comparison. In terms of mean stresses, (σv+σH+σh)/3, stress-sensitive permeability profiles were very much influenced by lithology. Complex interaction between stress anisotropy and rock fabric resulted in a non-systematic variation in permeability with mean stress for the laminated, heterolithic rock type. For the scenario of a horizontal wellbore drilled parallel to the minimum principal stress, σh, the measured permeabilities were used to calculate β-factors (β=kh/kv) for simple productivity evaluation. This sensitivity analysis indicated that well performance curves were also susceptible to the degree of stress anisotropy. The effect was evident in discrepancies of up to several hundred feet in calculated horizontal wellbore lengths required to achieve desired levels of productivity.
Laboratory Investigation of Constitutive Property Scaling Behavior
Authors: Tidwell V. C. 
Published: December 2007

Abstract
Property scaling becomes an issue whenever heterogeneous media properties are measured at one scale but applied at another (i.e., data is collected at the core scale but analysis is conducted at the grid block scale). A research program has been established to challenge current understanding of property scaling with the aim of developing and testing models that describe scaling behavior in a quantitative manner. Scaling of constitutive rock properties is investigated through physical experimentation involving the collection of gas-permeability data measured over a range of discrete scales. The approach is to systematically isolate those factors that influence property scaling and investigate their relative contributions to overall scaling behavior. Two blocks of rock, each exhibiting differing heterogeneity structure, have recently been examined. The two samples were found to yield different scaling behavior, as exhibited by changes in the distribution functions and semi-variograms. Simple models have been fit to the measured scaling behavior that are of similar functional form but of different magnitude.
An Application of Idealized Carbonate Depositional Sequences for Reservoir Characterization
Authors: Shao Hongbin , Brimhall R. M. , Ahr W. M. , Wu C. H. 
Published: December 2007

Abstract
This paper presents an application of idealized carbonate depositional sequences in reservoir characterization for the San Andres/Grayburg reservoirs of the Central Basin Platform (CBP) and the Northern Shelf (NS) in West Texas. The ramp and shelf sequences represent two typical carbonate deposits. An idealized progradational ramp sequence with a progressive ramp sequence leads to develop a ramp reservoir model for characterizing the reservoirs of CBP. An idealized progradational shelf sequence with a progressive shelf sequence leads to develop a shelf reservoir model for characterizing the reservoirs of NS. The reservoir models explain variations in the lumping lateral depositional energy, recovery efficiencies, and vertical variation of reservoir permeability.
Velocity and Turbulence Intensity Profiles for Newtonian Annular Flows and the Effect of Mechanical Aids on These Profiles
Authors: Buckingham J. C. , Grimley T. A. , Buckingham J. P. 
Published: December 2007

Abstract
Primary cementing operations, especially those associated with horizontal wells, have encountered many problems that have resulted in poor cementing. During the cementing operation, the complete removal of drilling mud, drill solids, and filter cake (left in the wellbore annulus from the drilling operation) is of utmost importance. The oil industry has attempted to solve the problems of displacing the mud, solids, and filter cake by many means, including the use of mechanical aids attached to the casing. The objective of these aids is to modify the flow in the wellbore annulus to provide a better distribution of the wash material or cement around the casing, and thus better displace the contaminants.
The objective of this joint industry program was to establish, through flow visualization and flow measurements (using non-intrusive, laser Doppler velocimetry techniques), the change in annular flow characteristics produced by various mechanical aids for various casing positions, flow regimes, and fluid types. The initial testing was to be performed with a Newtonian fluid (water), and the most promising mechanical aids were tested with a non-Newtonian slurry with Theological properties similar to typical cements.
This paper summarizes the Newtonian fluid testing effort, including a description of the full-scale annular test facility, measurement of the baseline characteristics of the test facility, and the results of the mechanical aids screening tests.
Parametric Study of Gas Entry into Cemented Wellbores
Authors: Sabins Fred , Wiggins Michael L. 
Published: December 2007

Abstract
A cement slurry is placed in a wellbore to harden into an impermeable mass that seals the annulus from fluid flow and protects the casing from corrosion for the life of the well. If fluid flow does occur in the form of gas migration, expensive remedial squeeze cementing techniques are generally required.
The objective of the work covered in this paper was to study the parameters that affect entry of gas into a cemented annulus. This research incorporated a detailed study of the factors that contribute to gas influx from the time of initial placement of the slurry, through the gelation or transition state of the slurry, to the set condition. Based on the understanding of the processes involved in gas entry, a simulator was developed that can predict the amount of gas that enters a cemented wellbore and can identify the critical parameters that affect the gas entry.
This study concerns itself with a portion of the gas flow problem: the entry of gas into a cemented annulus only—not the flow of the gas up through the cement and the formation of a gas channel.
This study will provide insight to the following issues: What cement properties are important to minimize gas entry?What role does fluid loss play in minimizing gas influx?What well parameters affect gas entry?
Hydrates Formed in Unprocessed Wellstreams
Authors: Tohidi Bahman , Danesh Ali , Burgass R. W. , Todd A. C. 
Published: December 2007

Abstract
Production and transportation of unprocessed wellstreams is economically an attractive option and may significantly enhance the development of many marginal oil and gas fields. These pipelines may however be prone to hydrate formation which potentially can block the pipe and lead to serious operational problems. These can be avoided by either preventing hydrate formation or allowing the formation of hydrates, but preventing their aggregation and transporting them as slurry.
The first approach is the current practice in the industry and it can be more cost effective by determining the hydrate phase boundary more reliably. In the oil and gas industry, n-butane is generally regarded as the heaviest hydrate forming compound, and anything heavier than that as a non-hydrate former. Oil and gas condensate systems contain a significant amount of intermediate/heavy hydrocarbon compounds which recently have been found to be hydrate formers. The water produced with oil also contains dissolved salts which inhibit hydrate formation to some extent. If the formation of hydrates is to be avoided, information on the effect of heavy compounds and salts on the hydrate boundary is required.
Recent studies suggest that some chemicals at low concentrations may modify the growth of hydrate crystals, preventing their aggregation and hence allowing their transportation as slurry. If the use of crystal growth modifiers are to be considered, it is required to determine the amount of hydrates to be transported as a slurry.
This paper reviews briefly the effect of electrolyte solutions, benzene, and methyl cyclo-pentane (MCP) on the hydrate free zone and concentrates on new methods and equipment for measuring the amount and composition of different phases in hydrate forming conditions. An in house numerical model was successfully used for prediction of the hydrate free zone and compositional data. The developed model can be used as an engineering tool to determine the hydrate free zone for transportation of unprocessed well streams in sub-sea pipelines and gathering networks and also the amount of hydrates to be transferred as slurry where the use of growth modifiers is considered as an option.
Wax Deposition of Waxy Live Crudes Under Turbulent Flow Conditions
Authors: Hsu J. J. C. , Santamaria M. M. , Brubaker J. P. 
Published: December 2007

Abstract
Laboratory test methods have been developed to measure wax deposition of waxy live crudes under turbulent flow conditions. This high pressure wax deposition turbulent flow loop is rated up to 1500 psia and from 32 to 240 °F. The apparatus has been used to study impact of flow regimes, oil composition, water, and paraffin inhibitors.
Under turbulent flow conditions the pseudoplastic non-Newtonian behavior of a cold waxy crude significantly affects wax deposition rate. Wax deposition from a waxy crude can be reduced significantly under turbulent flow conditions. The flow turbulence depresses the temperature at which maximum wax deposition rate occurs.
The sloughing effect generated under turbulent flow conditions has significant impact on wax deposition rate and can not be neglected in wax deposition modeling.
Oil composition is a factor affecting wax deposition. Usually, wax deposition rate decreases with increasing oil bubble point pressure under turbulent flow conditions.
The wax hardness and carbon number of the wax deposited on the pipe wall increase with retention time.
The high pressure wax deposition turbulent loop has been used to evaluate wax inhibitors, and study optimum flow conditions and oil compositions to prevent wax problems for designing subseapipelines in the North Sea. The results are critical for potential cost savings derived from optimum design for waxy crude transport conditions.