bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hysteresis of Methane/Coal Sorption Isotherms
Authors: Bell Gregory J. , Rakop Karen C. 
Published: December 2007

ABSTRACT
Methane production from coal seams has been actively pursued in the U.S. since the mid-1970's. This resource is regarded as an unconventional natural gas supply due to several unique characteristics of the reservoir, including: two-phase (water and gas) flow, low effective permeability to gas, and the majority of the methane being held in an adsorbed state on the internal surfaces of the microporous coal structure rather than as compressed or dissolved gas within the pores.
In a virgin coal reservoir with ideal conditions the adsorbed methane concentration is in equilibrium with the initial reservoir pressure. Production of gas from the coal bed depends on the release of this adsorbed methane to a free state, which then flows through the natural fracture system of the coal towards the wellbore. Release of the adsorbed methane is accomplished by dewatering the reservoir which decreases the local pressure and thereby upsets the equilibria.
In the past, researchers have utilized laboratory-measured adsorption isotherms to model the gas concentration/reservoir pressure equilibrium relationship. In the current study both adsorption (pressure increasing) and desorption (pressure decreasing) isotherms were determined for several coal samples. It was found that there are hysteresis effects which cause the two sorption modes to be different. The desorption isotherms were more non-linear than the adsorption isotherms. In terms of reservoir performance this means that coalbed reservoirs must be drawn down to pressures lower than those indicated by adsorption isotherms to achieve the same degree of methane release.
This paper presents a review of methane/coal adsorption phenomena and compares results of the present work with those of previous investigators. Experimental procedures are given along with error analyses and substantiation of repeatability. Variability of gas content within the coal seam is determined for a deep western coal from the Piceance Basin in Colorado. The effect of moisture content on methane sorptive capacity is investigated for an eastern coal from the Black Warrior Basin in Alabama. All samples and funding were provided from Gas Research Institute's R&D field sites.
Mud and Cement for Horizontal Wells
Authors: Zurdo C. , Georges C. , Martin M. 
Published: December 2007

ABSTRACT
High-angle and horizontal well bores raise many questions concerning the characteristics of mud and cement. This paper is a summary of our knowledge and work on these two subjects.
For all research carried out, large or full-scale laboratory test plants were used.
Cutting transport is not only a problem in horizontal conditions but hole angles of 25 to 65° can be even more critical when parameters such as mud rheological properties and velocities are not optimized.
Drilling a long horizontal drain creates a dynamic annulus pressure unbalance. This can lead to a loss and kick situation. Two test benches were thus used to obtain a good understanding of the inefficiency of conventional plugging methods and of the difficult ies of gas migration control in subhorizontal well bores. High concentrations of LCM, high rheological properties of fluids and low flow rates increase the chances of solving the first problem. The results of the second bench demonstrate the difficulties of annulus gas evacution for angles varying from 90 to 100 degrees, or from over-gauged sections in horizontal holes.
Cementing horizontal casing strings is still a fairly new practice. However a good casing/formation cement bond is certainly the best means of obtaining correct well productivity. A successful horizontal cement job should prevent the formation of mud, water and gas channels and of a free water channel on the upper part of the drain hole.
Therefore, several full-scale test benches (25 to 300 m in length) were set up in order to study the following cement placement parameters: casing-hole eccentricity, drilling fluid rheological behaviour, hole geometry, spacer design (rheology and density), flow rate, etc. Furthermore, slurries without free-water were studied for varying downhole conditions.
Successful High Angle Drilling in the Statfjord Field
Authors: Wilson R. C. , Willis D. N. 
Published: December 2007

ABSTRACT
The original drilling design criteria for Statfjord field development set an upper limit on wellbore inclination of 60°. This figure was derived by considering the special drilling problems found on Statfjord and technological limitations.
By developing engineering operational procedures and introducing new technology, wells can be drilled routinely at sail angles between 60° – 70°.
This paper, therefore, elaborates upon the special drilling problems encountered in the area and describes engineering and operational solutions which were developed to extend the maximum reach of wells. In addition, it describes the evolution of drilling on Statfjord and documents the impact of advances.
Wellbore Inertial and Frictional Effects on Drillstem Tests From Naturally Fractured Reservoirs
Authors: Saldana M. A. , Brigham W. E. , Ramey H. J. 
Published: December 2007

ABSTRACT
A mathematical formulation is presented in this paper which includes wellbore inertial and frictional effects during a slug test or the flow period of a drillstem test from naturally fractured reservoirs. This formulation is obtained by coupling a wellbore equation and the diffusivity equation for double-porosity reservoirs. The wellbore equation represents a transient momentum balance relating liquid level in the wellbore and bottomhole pressure. Wellbore storage and skin effect are considered in the coupling conditions. A simplified formulation resulting from the assumptions of a small slug and friction losses for laminar flow in the wellbore is solved by applying the Laplace transformation with numerical inversion.
Solutions obtained in this study show a distinctive double-porosity behavior for some naturally fractured reservoirs. For those naturally fractured reservoirs with double-porosity behavior, an estimate of the interporosity flow parameter, λ, and of the storativity ratio, ω, can be obtained in addition to fissures transmissivity, kfh/µ, and skin effect factor, s. On the other hand, during the practical range of time, the response of other naturally fractured reservoirs follow either the response for a single-porosity reservoir with the properties of the fracture system or the response of a single-porosity reservoir with the combined properties of the fractures and matrix blocks.
Criteria to estimate the magnitude of wellbore inertial and frictional effects for practical systems are developed from an analysis of results obtained in this study. Also, the solution method proposed in this paper can be used to forecast or match bottomhole flowing pressures during a drillstem test from estimates of the properties that describe a naturally fractured reservoir.
A North Sea Application of Slug Testing for Quick Reservoir Analysis
Authors: Waller H. N. , Krase L. D. 
Published: December 2007

ABSTRACT
The application of slug testing in the Valhall Field, a North Sea reservoir, is presented. Specific field examples are given which show this pressure transient testing method to be a quick and reliable way to determine reservoir flow capacity and wellbore skin factor. Some of these examples show confirmation of a channel behind pipe that was indicated by a cement bond log. A review of the theoretical basis of the method is also given.
Although this method has found wide application in ground water hydrology, it has been used on a very limited basis in the petroleum industry. As applied here, the test is conducted on an isolated zone at the time of perforating underbalanced with the well filled with diesel. The primary advantage of this test is the extremely short time required to collect sufficient data for analysis, even when permeability is relatively low or skin factor is high. The test also eliminates problems associated with wellbore storage. Therefore, both required rig time and the production deferred due to data collection are minimized. This advantage is especially important in costly offshore applications and should lead to use of the technique in many other fields worldwide.
A Combined Condensing/Vaporizing Mechanism in the Displacement of Oil by Enriched Gases
Authors: Zick A. A. 
Published: December 2007

ABSTRACT
Experimental observations, combined with equation-of-state predictions, indicate that a combined condensing/vaporizing-gas drive mechanism, rather than the traditionally believed condensing-gas drive mechanism, may be responsible for displacements of reservoir oil by enriched gases. Apparent minimum miscibility pressures and minimum solvent enrichments are observed with this mechanism, even though true miscibility is probably not developed.
CO2 Huff-Puff Simulation Using a Compositional Reservoir Simulator
Authors: Hsu H. -H. , Brugman R. J. 
Published: December 2007

ABSTRACT
Increased field application of the CO2 Huff-Puff process has resulted in increased laboratory and numerical simulation activity. This paper focuses on numerical simulation of the CO2 Huff-Puff process in a light oil reservoir, using a fully-compositional reservoir simulator.
A simulation model is first validated by successfully history-matching production data from two huff-puff cycles. A performance prediction is then conducted for a third cycle. A number of parametric runs are performed to determine oil recovery as affected by: The number of cycles,The timing of injection, soak and back-production operations, andThe quantity and composition of the injected sol vent.
The following conclusions can be made based on the results of the CO2 Huff-Puff simulation: The simulation of a CO2 Huff-Puff process is possible through the use of a compositional reservoir simulator. A successful history match of oil, water, and GOR was conducted for two cycles of a CO2 Huff-Puff project in Paradis Field, Louisiana. The model is suitable for design, evaluation and prediction of a CO2 Huff-Puff project. It can also assist engineers in gaining insight into the oil recovery mechanisms in a CO2 Huff-Puff project.The simulation results from the Paradis project indicate that, The primary CO2 effects on oil recovery appear to be vaporization of intermediate components, oil viscosity reduction and oil phase swelling,A significant drop in incremental oil recovery occurred between the first and second cycles for this particular project. A third cycle would probably not be attractive,Variation in soak time from 5 to 40 days has little effect on oil recovery,The most important parameter affecting oil recovery appears to be the quantity of injected solvent, andContamination of a pure CO2 solvent with up to 20 mole percent N2 or CH4 has little effect on oil recovery.
General Spectral Theory for the Onset of Instabilities in Displacement Processes in Porous Media
Authors: Scheidegger A.E. 
Published: December 2007

Abstract
The problem of penetration of a fluid into a porous medium containing a more viscous liquid is investigated. It is known that the displacement front may become unstable in this case because it may break up into "fingers". The problem of inception of fingers has been treated previously in the literature by describing the displacement front in terms of its Fourier transform. In the present paper, we generalize earlier procedures by making allowance for an arbitrary elemental growth law. Furthermore, we assume that the phenomenon of fingering is not solely governed by the prevailing flow potentials, but also by the spectrum of heterogeneities in the porous medium. This is achieved by introducing a constant characteristic of the frequency of the heterogeneities in the porous medium. It then turns out that the maximum rate of growth as a function of wave length is considerably shifted from that predicted in the literature. At the same time it is also shown that the difficulty encountered by other workers, which consists of small wave lengths growing at an infinitely high rate, is being avoided.

Introduction
When a fluid enters a porous medium displacing a more viscous liquid, an interesting kind of instability may occur at the displacement front. Protuberances may arise which shoot through the porous medium at relatively great speed, leaving behind the large amounts of the liquid intended to be displaced. This phenomenon is commonly referred to as "fingering".
The problem of fingering is an extremely involved one owing to the complexity of the phenomenon. To treat it theoretically, drastic simplifications have to be made. One way to do this is to confine one's attention to the very beginning of the occurrence of the instabilities. The displacement equations can then be linearized, the displacement front can be described by its Fourier transform and the growth law for each spectral component can be deduced.
An attempt along these lines has recently been published by Chuoke, et al., who showed how the prevailing flow potentials affect the various spectral components of a displacement front on the verge of instability. Chuoke's formula contains a capillary pressure term as an essential feature; if the limit is taken with this term being set equal to zero, a disconcerting difficulty arises. The spectral components with the smallest wave lengths are found to grow at the fastest rate; in fact, the rate becomes infinite for the wave length approaching zero.
Gas Well Decline Analysis Incorporating Real-Gas Behavior and Non-Darcy Flow
Authors: Schmidt S. H. , Caudle B. H. , Miller M. A. 
Published: December 2007

ABSTRACT
Through the application of the real gas potential and non-Darcy flow analysis, type curves have been developed which model decline behavior of real gases producing from a closed drainage volume. It was determined that both reservoir permeability (in relation to the turbulence factor) and initial average reservoir pressure at the start of the decline period significantly contribute to type curve response and should not be neglected from gas well decline analysis.
The result is a simplified and improved method for forecasting gas well performance and for estimating gas in place. Using the same dimensionless variables as those derived by Fetkovich1, a direct comparison of type curves, including the effects of varying reservoir parameters, is presented. Results from several case studies involving both single well and whole field data are also provided.
Application of Superposition and Pseudo-Steady State Concepts to Thermal Recovery Pressure Tests
Authors: Onyekonwu M. O. , Ramey H. J. , Brigham W. E. 
Published: December 2007

ABSTRACT
The liquid flow equations have generally been adapted for use in gas flow applications even though the gas flow equations are non-linear. This follows from earlier studies in which it was concluded that although superposition is correct only for linear partial differential equations, nevertheless there is a close check between linearized real gas solutions and the liquid flow solutions. However, these earlier studies were carried out at uniform reservoir temperature.
This paper discusses the application of superposition and pseudo-steady state concepts to gas reservoirs with non-uniform temperature such as thermal recovery systems. The paper is in two parts. The first part discusses verification of the finite-difference thermal simulator used for this study while the second part discusses application of the superposition and pseudo-steady state concept to thermal oil recovery falloff tests.
Results from this study show that effective pressure, compressibility and temperature are required for interpretation of thermal oil recovery falloff tests. The effective pressure is the same as the average pressure while the effective temperature is usually lower than the average temperature based on an energy balance. It may also be inferred from this study that non-linearity in the equations due to non-uniform temperature effects may be mild. This is because linear equations were successfully used to analyze cases with non-uniform reservoir temperature.
Field Application of Lignosulfonate Gels to Reduce Channeling, South Swan Hills Miscible Unit, Alberta, Canada
Authors: Wagner O. R. , Weisrock W. P. , Patel C. 
Published: December 2007

ABSTRACT
Following initiation by Amoco in 1973 of a secondary miscible (WAG) flood in the South Swan Hills Unit, tracer performance indicated severe channeling of solvent and water, particularly in the northwest quarter of the Unit. In 1975 and 1977, problem zones at 9 injectors were isolated and selectively treated with chrome-lignosulfonate time-set gels in an attempt to reduce solvent and water cycling. The treatment volumes varied between 8500 and 14,000 bb1s (1350 and 2225 m3) per well.
As part of an evaluation of the gel treatments, incremental oil production responses observed at a number of the 56 producers offset to the 9 treated injectors were examined. The responses which could not be explained by other contributory factors, such as the drilling of infill seam injection wells, well workovers (e.g. acid jobs and asphaltene treatments), casing repairs, and pump changeouts, were considered to be the result of improved sweep due to the gel treatments.
Thirteen of the 56 offset producers (23%) were found to have responded to the gel treatments, and these were rated as to the duration of response. Response durations of up to 18 months were rated as "good," and those lasting longer were rated as "excellent."
Although a detailed economic analysis was not performed, a comparison of the total cost of the 9 injector gel treatments with the gross revenues generated by the total calculated incremental oil from the 13 responding producers indicates that the treatments were an economic success.
Drillstring Torsional Vibrations: Comparison Between Theory and Experiment on a Full-Scale Research Drilling Rig
Authors: Halsey G. W. , Kyllingstad A. , Aarrestad T. V. , Lysne D. 
Published: December 2007

Abstract
This paper presents a mathematical method for the computation of torsional resonance frequencies in a drillstring. The torsional resonance frequencies in a drillstring are readily calculated from the nominal drillstring dimensions. A high degree of accuracy is achieved when a correction factor to the torsional propagation velocity in drillpipe due to the offsets at the drillpipe joints is incorporated into the calculations. The theory and computer program were tested against data recorded in a 1000m deep, nearly vertical well. Torsional spectra were recorded with the bit off bottom at 450m, 550m, and 1000m and while drilling. Well defined torsional resonances were observed for frequencies up to 40 Hz. The calculated resonance frequencies are in very good agreement with all experimental data.
Front-Tracking of Three-Dimensional Piston-Like Displacements in Porous Media
Authors: Kocberber S. , Miller M. A. 
Published: December 2007

ABSTRACT
In this study, a front-tracking method for three-dimensional piston-like displacement is described. Many reservoir processes develop distinct fronts (discontinuities) that move through the reservoir. When the width of the discontinuity is smaller than realistic computation mesh sizes, standard methods are not always adequate. By tracking frontal movement, accurate representation of the front location is provided.
This is accomplished by approximating the flow domain as regions of homogeneous properties separated by sharp, distinct fronts. Flow is treated as a succession of steady-states based on incompressible fluids. With these assumptions, the potential equation is solved by finite-element methods, and the front moved accordingly. Elements are originally aligned with streamlines based on single-phase flow so that mesh orientation effects are minimized. As the front moves, elements are reformed to represent the discontinuity at the front accurately.
The validity of the model is tested against data available in the literature. The model provides an inexpensive and accurate solution for problems such as coning, gravity under- and over-ride, fluid displacements, and movement of chemical reaction or gas condensation fronts, in which movement of the front is of primary concern. The method is applicable to two fluids of any mobility and density contrasts.
An Investigation Into the Application of Expert Systems to Matrix Treatment Design
Authors: Cram R. S. , Hendrickson A. R. 
Published: December 2007

ABSTRACT
The design of a Matrix Treatment can be an involved procedure requiring considerable knowledge and experience in order to maximize return on investment and improve the success of the treatment.
Some of the major decisions which must be made during the design process include the selection of the optimum base fluid followed by the choice of the required additives and the size of the proposed treatment. All of these decisions are crucial to the success or failure of the treatment and a great deal of expertise is required to ensure that the best choices are made.
The total number of possible combinations of base fluids and additives available to the design engineer are numbered in the hundreds. In many cases however certain additives are either not compatible with other additives or they are not compatible with materials in the formation. This can result in the total failure of a matrix treatment in the event that such a possibility is overlooked.
The introduction of expert system shells has made it possible to develop expert systems which can be used to guide and advise design engineers in selecting the best type of treatment for a given set of circumstances so reducing the possibility of important factors being overlooked. This can lead to reduced costs and an increase in the assurances of a successful job. A second advantage for large corporations lies in the fact that, since many of the expert systems can be run on relatively inexpensive micro computers, headquarters engineering personnel can be sure that all of their location technical staff can have the same guidelines to follow for treatment design.
This paper examines several different types of expert system shells and includes examples of how the different systems lend themselves to establishing guidelines in selecting the best fluids (acid and non-acid base) in treatment design.
Drag Bit Performance Modeling
Authors: Warren T. M. , Sinor A. 
Published: December 2007

ABSTRACT
Models for the forces required to remove a fixed volume of rock with a single cutter have been applied to different polycrystalline Diamond Compact (PDC) bit designs. The integration of the forces for each cutter over the bit face gives the torque and weight-on-bit (WOB) required for a particular rate-of-penetration (ROP).
This paper presents the results of comparing such a model to laboratory drilling tests for four radically different bit designs in four different rocks. The geometry of each cutter on the bit was determined by detailed measurements of the bit with a 3-axis coordinate measuring machine.
Drilling tests were conducted by "reaming" rock with an 8-1/2" bit that had been previously drilled with a 6-1/4" bit. Only the peripheral cutters engaged the rock during the reaming. Additional tests were conducted where the WOB and torque were recorded while drilling a pilot hole into the top of a flat rock and drilling through two different bed boundaries with constant ROP. The model predictions compared well to the measured data for both the reaming tests and the pilot hole tests.