bluuebunny/crossref_metadata_2025 huggingface dataset:
Microemulsion Phase Behavior: A Thermodynamic Modeling of the Phase Partitioning of Amphophilic Species
Authors: Prouvost Laurent , Pope Gary A. , Rouse Bruce
Published: December 2007

A thermodynamic model is presented for modeling the partitioning of amphiphilic species between the different phases of systems typically used for chemical flooding. The model, an extension of the pseudophase model by Biais et al.1 that can analyze only a four-component system, can work with five-component systems, including two partitioning amphiphilic species (e.g., two alcohols or one alcohol and a partitioning cosurfactant species).

The self-association of alcohol in the organic phases, which results in a variable alcohol partition coefficient, is considered.

Experiments to determine thermodynamic constants (which are entered into the model) are described for four-component systems, including one alcohol. The salinity dependence of these parameters is also studied. Brine/ decane/isobutanol/TRS 10-410 as well as brine/nonane/ isopropanol/TRS 10-80 systems are considered.

Some computations of pseudophase compositions for the five-component model and for various overall compositions are included. This partitioning model has been included in the chemical-flooding simulator developed at the U. of Texas; the results of this model have been presented in another paper.2 The model used for the binodal surface that is required to calculate phase compositions from pseudophase compositions is presented in this paper, as well as comparisons with experimental data for both four- and five-component systems. Reservoir simulation results are presented in Ref. 3.
Miscible Flood Forecasting Technique at Judy Creek
Authors: Biberdorf O. C.
Published: December 2007

A simplified forecasting technique was developed to predict the recovery performance of a hydrocarbon miscible flood in the Judy Creek Beaverhill Lake (BHL) A Pool in Alberta. This technique incorporates the physics of the hydrocarbon miscible-displacement process as well as the complex geological reservoir description across the entire pool. The advantages of the technique over conventional three-dimensional (3D) reservoir simulation include cost-effectiveness, speed, and flexibility of parametric evaluations.

A single-layer areal reservoir simulation model described the areal sweep; oil recovery performance as a function of injection and solvent bank size; and solvent, chase gas, and postmiscible water breakthrough times. A cross-sectional reservoir model determined the effect of gravity override. A geological model provided the porosity and permeability distribution for every 0.6-m [2-ft] interval in each injection pattern as well as the continuous PV-i.e., the volume that is available for miscible displacement. These results were combined into a simplified algorithm (the Forecast Model) to predict tertiary recovery. The Forecast Model adds the tertiary recovery forecast to the waterflood forecast developed from decline analysis to generate a total oil forecast under miscible flooding. This miscible flood forecast is physically reasonable and predicts recovery levels consistent with observed performance of large-scale miscible projects. This technique is being extended for use in other reservoirs that are candidates for miscible flooding.
Trends in Engineering Education Indicate Need for Five-Year Curricula
Authors: Langenheim R.L. , Guerrero E.T.
Published: December 2007

In the training of engineers, engineering education has and continues to perform a major role. This paper analyzes trends in engineering education and accreditation and points out the role that educators and professional engineers must assume in guiding it. Curricula in chemical, mechanical, and petroleum engineering are presented for 1925 and 1958 in order to show significant trends that have occurred in the past 33 years.

The 1958 curricula are compared with the ASEE and ECPD accreditation recommendations and the differences discussed. The authors express personal views regarding current accreditation procedures and the emphasis placed on the humanities and number of semester hours included in curricula.

It is concluded that engineering education should be recognized as a five-year program and that engineering societies should join educators and participate actively in determining future trends.

Introduction

Engineering can generally be defined as the application of science to machines, vehicles, processes and procedures for the improvement of living conditions. It is through engineering that scientific discoveries are applied and the necessity for additional investigation discovered. Science and engineering are strongly interdependent, yet are distinct fields of endeavor. A vast new source of energy has been discovered through nuclear fission yet it remains for engineers to find practical uses for it. In the training of engineers, engineering education has and continues to perform a major role. It is the objective of this article to analyze trends in engineering education and accreditation and to point out the role that educators and professional engineers must assume.

Typical Engineering Curricula

Engineering curricula vary in content depending upon where the work is offered and the major field of concentration. In order to use some degree of quantitative interpretation in this discussion, mechanical, chemical, and petroleum engineering curricula of three major universities were selected. These are shown in Table 1 with the most current and late 1920's curricula included. Note that in the basic sciences, chemical and petroleum show an increase in physics requirements and a decrease in chemistry. Petroleum also shows a decrease in geology.
A New Approach to Instability Theory in Porous Media
Authors: Bernsen R. G.
Published: December 2007

Early work in the area of instability theory is limited in that it is based on first-order perturbation theory and the concept of a velocity potential. Thus, while it can deal with an incipient finger, it cannot deal with the subsequent growth of a finger. This paper develops a new approach to the instability theory that overcomes this limitation. The new approach, like earlier work, is based on the assumption that the immiscible displacement of one fluid by another can be treated as a moving-boundary problem. Therefore, two solutions arise, one for each side of the plane interface that initially separates the two fluids. Because the new approach makes use of a force potential rather than a velocity potential, it is possible to impose several new conditions on these two solutions. As a consequence, further extensions to the stability theory have been obtained. In particular, it is now possible to predict the steady-state velocity at which a finger propagates and, consequently, the breakthrough recovery obtained not only when the displacement is stable, but also when it is pseudostable.
An Integral Approach for Discretizing the Reservoir Flow Equations
Authors: Nghiem Long
Published: December 2007

An approach for discretizing the integral form of the flow equations in porous media is proposed. The method has the advantage of providing the correct block volume calculations and steady-state flow in curvilinear coordinates. The harmonic mean for permeability is also obtained from the discretization. The equations are developed for a general orthogonal curvilinear grid system in terms of the components of the metric tensor.
Geothermal Reservoir Evaluation Considering Fluid Adsorption and Composition
Authors: Economides M. J. , Miller F. G.
Published: December 2007

The concept that adsorbed water is a major source of production fluid in vapor-dominated geothermal reservoirs is presented. The implications of adsorption on material-balance calculations and on well test analysis are determined by incorporation of adsorption effects into existing models. New analysis methods introduced here provide a more realistic estimate of the nature and extent of the vapor-dominated zone. The methods result in a considerable reduction in the estimated formation thickness and suggest that fracture porosity has been underestimated with conventional models for a naturally fractured reservoir.

The presence of noncondensable gases in the geothermal fluid has a profound effect on the thermodynamics associated with vapor/liquid equilibrium and adsorption. Noncondensable gases can cause the dewpoint pressure of a noncondensable gas/water mixture to be elevated substantially, above the vapor pressure for pure water at reservoir temperature. Hence, the presence of gas in geothermal steam extends the pressure range where vapor adsorption phenomena are in effect. Monitoring of gas production in the produced geothermal fluids provides additional data useful in evaluating adsorption effects.

The adsorption phenomenon in reserve estimation is of considerable importance. This work shows that a reserve estimate based on geologic evidence and the thermodynamic properties of steam could be as much as an order of magnitude lower than the actual mass of water present.
Geology of Devonian Shale Oil and Gas in Pleasants, Wood, and Ritchie Counties, West Virginia
Authors: Filer J. K.
Published: December 2007

The Upper Devonian shale play of western West Virginia is an area of active development of unconventional oil and gas reserves. It is unconventional in that production is from fine-grained fractured reservoirs. Examination of recent drilling results has led to a more detailed understanding of the structure and stratigraphy of the area, which in turn can explain some of the production trends observed. Areas of greater fracture density and therefore higher productivity are related to areas of shearing motion in the Burning Springs thrust sheet. Open flows after stimulation in these wells can be very high, but first-year decline is rapid. It is uncertain at this time how long a production life these wells will have.
Silica Removal From Steamflood-Produced Water: South Texas Tar Sands Pilot
Authors: Thomas S. A. , Yost M. E. , Cathey S. R.
Published: December 2007

Steamflood-produced waters commonly contain suspended solids, oil, hardness-causing minerals, sulfide, and silica. Removal of these contaminants would make many of these waters suitable for recycling as steamer feedwater. Reuse of steamflood-produced waters increases steamer feedwater supplies and reduces water disposal requirements.

This paper describes a field pilot study of silica removal from steamflood-produced water in the south Texas tar sands region. A hot-lime precipitation process was used to reduce dissolved silica (SiO2) concentrations from 400 to less than 50 mg/L SiO2 in Mary R. Saner Ranch produced water. Most water systems using hot-lime precipitation for silica removal require the addition of magnesium salt, as well as lime, to enhance silica removal. In this field study, however, addition of magnesium salt did not improve silica removal efficiency. Hydrated lime, Ca(OH)2, alone was sufficient to attain desired silica residual, 50 mg/L SiO2. The dissolved silica adsorbed onto the CaCO3 crystals formed by lime reacting with the alkalinity present in the produced water. Required lime dosage was approximately 900 mg/L Ca(OH)2.

Residual silica concentration was found to be strongly related to both precipitator effluent pH and calcium ion concentration. Therefore, on-line pH and hardness monitoring may be used to estimate and to control residual silica concentration. A 50,000-B/D [7950-m3/d] produced-water treating plant has been designed from the results of this pilot study.
Performance of a Beryllium Copper Nonmagnetic Drill Collar Alloy
Authors: Dunlevey F.
Published: December 2007

Laboratory characterization and extensive field service show the advantages of beryllium copper Brush Alloy 25 for use in nonmagnetic drill collars (NMDC)'s, stabilizers, and subs. Beryllium copper is resistant to stress-corrosion-cracking (SCC) failures at elevated temperatures and pressures in the presence of H2S and dissolved chloride solutions. The alloy is more resistant than stainless steel to galling failure in threaded joints. Its magnetic permeability is lower than stainless steel and is unaffected by service conditions.
Profitable Application of Well Logs
Authors: Kirby J.E. , Culver R.C. , Mattei J.B.
Published: December 2007

The well logging phase of a coordinated formation evaluation program can improve the quality of basic reservoir data while reducing the need for extensive coring and drill-stem testing. The quantitative data to be determined from log analyses are formation porosity, fluid saturation and formation water resistivity. In order for these data to be obtained successfully, the proper logging devices must be selected, accurate data on the borehole conditions must be obtained and quality control measures regarding logging techniques must be exercised. The use of core analyses and drill-stem test data on a key-well basis to confirm log calculations is a necessary requirement to assure maximum dependability of quantitative log interpretation for reservoir analysis purposes.

Introduction

Well logging is one of the most useful of the various types of open-hole formation evaluation methods. When properly applied, present techniques of well logging and interpretation can provide substantial reductions in the costs of evaluation, development and exploitation of petroleum reservoirs. The initial benefit from a good logging program is that better well completions can be made. A second and more important benefit is that a reliable calculation of oil in place can be made for reservoir analysis purposes from the location of water contacts, reservoir boundaries and the calculation of formation porosity and water saturation data. Necessary formation evaluation data can be obtained at a much lower cost by using log information to extend key-well core analyses and drill-stem test data for coverage of the entire reservoir instead of using an extensive coring and testing program.

A logging program cannot be considered successful and profitable unless the basic reservoir data obtained from the logs are valid and complete. This objective can be reached, however, if the logging program is properly planned and coordinated with the other formation evaluation methods used. It is worthy of note that even the qualitative value of logs is doubtful unless proper planning is used in the selection of the types of logs to be run and unless suitable quality control measures are followed in logging techniques.
Application of the Pseudolinear-Flow Model to the Pressure-Transient Analysis of Fractured Wells
Authors: Cinco-Ley H. , Samanlego-V F. , Rodriguez F.
Published: December 2007

The theoretical basis for the pseudolinear-flow model is established. It is demonstrated by use of an analytical model that the linear-flow graph (p vs. t) can be extended to the analysis of pressure data of fractured wells intersected by an intermediate- or high-conductivity fracture (CfD > 5π). It appears that the fracture-conductivity effect during the pseudolinear-flow period can be handled as pseudoskin pressure drop that adds to the pressure drop caused by fluid-loss damage. The combination of the pseudolinear-flow analysis with other interpretation techniques is illustrated through examples of field cases.
Reservoir Compaction Loads on Casings and Liners
Authors: Wooley Gary R. , Prachner W.
Published: December 2007

Pressure drawdown resulting from production causes compaction of the reservoir formation, which induces axial and radial loads on the wellbore. Reservoir compaction loads increase during the production life of a well and are greater for deviated wells. Presented here are casing and liner loads at initial and final reservoir pressures for well deviation angles of 0 to 45° [0 to 0,79 rad].
Effect of Phase Behavior on CO2 Displacement Efficiency at Low Temperatures: Model Studies With an Equation of State
Authors: Nghiem L. X. , Li Y. K.
Published: December 2007

In this paper, we examine the use of an equation of state (EOS) to predict the phase behavior of CO2/crude-oil systems at low temperatures. An adequate match of the experimental pressure/composition diagrams of a dead oil and two recombined oils from the Wasson field at 90°F [32°C] is obtained. The incorporation of three-phase flash calculations in a compositional model is described. The model is used to simulate CO2 slim-tube displacements and yields results that are consistent with experimental observations.
Temperature-Stable Polymeric Fluid-Loss Reducer Tolerant to High Electrolyte Contamination
Authors: Son Adelina J. , Ballard Thomas M. , Loftin Royal E.
Published: December 2007

The suitability of a synthetic copolymer for drilling deep, hot wells was demonstrated through laboratory and field testing. The polymer provided fluid-loss control at 400°F [204°C] to clay-free saturated-salt laboratory muds and to low-solids, nondispersed field muds contaminated with drill solids and sodium and calcium salts. High-temperature/high-pressure (HTHP) filtrate was kept at ≤15 cm3/30 min after 400°F [204°C] heat-aging of a 19-lbm/gal [2277-kg/m3] saturated-salt mud. Weighted (>18-lbm/gal [>2157-kg/m3]) potassium muds treated with the polymer showed heat stability and solids and green-cement tolerance.

The polymer was successfully field-tested in two offshore wells where bottomhole temperatures (BHT's) reached 400°F [204°C] and salt and calcium chloride flows were encountered.
Bottom-Water and Edge-Water Effects on Low Gravity Oil Production
Authors: Knopp Charles R.
Published: December 2007

Water encroachment into low gravity oil reservoirs tends to be irregular because of three mechanisms -selective encroachment,water-leg tonguing andindividual well coning.

An investigation was made of 31 wells that were completed in low gravity oil sands with bottom water present in the base of the well-sand interval. It was found that initial water cuts occurred rapidly. Current average recovery for each of the 31 original completions is 10,184 bbl (31 per cent) clean oil and 22,542 (69 per cent) wet oil. Fourteen (45 per cent) of the 31 original completions have either been recompleted to other sands or are not feasible to produce because of high water-cut production. Average cumulative recovery for each original completion is now only 32,726 bbl of oil.

Four low gravity oil reservoirs with well defined fault boundaries and original oil-water contacts were studied to ascertain the effects of irregular edge-water encroachment. This study showed that initial water cuts have rapidly occurred in all 12 (including the most up-dip) wells completed in the four reservoirs; only two of these wells were completed with an original water-leg extension in the base of the well-sand interval. Comparative clean and wet oil recovery from these four reservoirs has been 419,100 bbl (34 per cent) clean oil vs 810,500 bbl (66 per cent) wet oil.

Ultimate recovery from the abandoned MG–30 reservoir is 1.9 per cent of the 8 million STB of oil initially in place. It is concluded that selective encroachment of edge water along thin, highly permeable, stratum has acted to reduce ultimate recoveries in the four reservoirs from 7 per cent - the recovery that would be expected if solution gas drive were the depletion mechanism.

Two basic remedial techniques offer a possible solution for eliminating adverse (irregular) edge-water encroachment. One of these is gas pressure maintenance. The second technique embodies the production of water from the more down-dip areas of the reservoir to balance water influx from the associated aquifer.
Microscopic Distribution of Wetting and Nonwetting Phases in Sandstones During Immiscible Displacements
Authors: Yadav G. D. , Dullien F. A. L. , Chatzis I. , Macdonald I. F.
Published: December 2007

A novel technique has been developed and used to study the microscopic distribution of wetting and nonwetting phases in reservoir rocks during immiscible displacements. The underlying principle is the use of appropriate fluids, serving as the wetting and the nonwetting phases, that can be solidified in situ, one at a time, without altering to any significant extent the position and orientation of the phases acquired at capillary equilibrium conditions. After both phases are solidified, the rock matrix is etched and replaced by a resin to enhance the quality of polishing. Polished sections are then serially made at each 5- to 10-μm depth and photomicrographed, wherein the three phases are distinguishable from each other. Experimental results have been obtained with Berea sandstone and the phase distribution is being analyzed. Relative permeabilities measured with the other phase solidified compare very well with conventional results obtained by the Penn State steady-state method, using Soltrol™ and brine. Wettabilities of the fluid pairs were also visualized directly by this new technique.
Effect of Crude-Oil-Induced Wettability Changes on Oil Recovery
Authors: Morrow Norman R. , Lim Hau T. , Ward Jill S.
Published: December 2007

Displacements in strongly water-wet cores are compared with results of similar tests for a mixed wettability condition induced by a selected crude oil. Cores exposed to crude oil showed weakly water-wet imbibition behavior and 30 to 65% improvement in microscopic displacement efficiency. Other characteristics included clean breakthrough and low relative permeability to water at residual oil saturation. Flow visualization experiments with crude oil in micromodels showed improved oil recovery from pore bodies with oil trapping in pore throats. Capillary numbers for mobilization of residual oil from weakly water-wet systems were higher than for strongly water-wet systems. Contact-angle measurements showed that adsorbed transition metal ions at a high-energy surface could have a dominant effect on wetting behavior.
A Field Scale In-Situ Combustion Simulator With Channeling Considerations
Authors: Ito Yoshiaki , Chow Allan Kwok-Yuen
Published: December 2007

Many thermal simulators have been developed in the past few years, most based on the assumption that all the important mechanisms of the combustion process would remain intact when a laboratory-scale simulation study is scaled up to a field-scale study. In most cases, the simulators provide the users with the capabilities to achieve good history matches of laboratory results when small gridblocks (i.e., 5 cm [2 in.]) are used. When the simulators are used in a field-scale study in which gridblocks are usually greater than 10 m [33 ft], however, many problems have been encountered, including high fuel consumption and misrepresentations of the chemical reactions.

A new and numerically stable algorithm has been developed to achieve the desirable fuel consumption. This algorithm involves an oil-flow-enhancement scheme. Arrhenius-type reactions have been found to be inadequate in field-scale combustion simulation. A new pseudokinetic scheme is introduced to field-scale studies in which the reaction zone is not simulated accurately because of the large size of the gridblocks.

In some in-situ combustion projects, viscous fingering and channeling phenomena can affect the efficiency of the combustion process. A new formula of molecular diffusivity of oxygen has been introduced to represent the contact efficiency of the reactants. A new concept that represents the nonequilibrium thermal condition between the injected fluid and the resident materials (i.e., poor exchange of heat energy) is discussed.
Heat Transfer and Oil Displacement Models for Tar Sands Reservoirs
Authors: Ward C. E. , Ward G. D.
Published: December 2007

A convective heat-transfer model and one-dimensional (1D) microcomputer displacement model applicable to steamfloods and firefloods of tar sands and heavy oils are presented. A method for predicting the fuel burn in a fireflood is also included.
Determination of Proppant and Fluid Schedules From Fracturing-Pressure Decline
Authors: Nolte K. G.
Published: December 2007

A procedure is presented for designing a fracture treatment when little or no information is available. This procedure is based on fluid efficiency, which is defined as the fracture volume divided by the injected fluid volume. The fluid efficiency for a treatment was found to determine the pad size and optimum proppant schedule completely without any assumption of the appropriate fracture-geometry model or associated parameters. The efficiency was also found to determine the fluid's exposure time to temperature. This determination requires an assumption for the portion of the fracture face that is cooled during a treatment. The exposure is important for defining the fluid additives of relatively large and high-temperature treatments. The fluid efficiency can be determined from a pressure-decline analysis for a calibration treatment performed before the actual stimulation treatment. In addition, if the appropriate geometry model is assumed, the decline analysis of the calibration treatment provides inferred values of fluid-loss coefficient and fracture width and penetration. Also, for the case when the calibration treatment is smaller than the actual stimulation, analyses are presented for predicting the relative change in efficiency, width, and penetration for the treatments.
Estimating Subsurface Fracture Density in Core: Effects Resulting From Variable Fracture Spacing
Authors: Lerche I. , Narr W.
Published: December 2007

The density of subsurface joint-type fractures in bedded rock is estimated quantitatively from the calculation of probabilities of core-fracture intersections for a range of fracture densities. The true fracture density is estimated by the determination of the value that yields a calculated number of fractured beds equal to the observed number of fractured beds. Core diameter, bed thicknesses, and geometric corrections necessitated by bedding dip and fracture pitch are accounted for. Fracture density is considered a function of the ratio of bed thickness to fracture spacing.

Fracture spacing may not be distributed normally about a mean, and the value of the statistical estimate of fracture density, and its standard error, is sensitive to the form of the fracture-spacing distribution. A functional form of the fracture-spacing distribution can be estimated from the core data for use when fracture density is derived.

Expressing the relationship between bed thickness and fracture spacing by a linear function may not always be reasonable. When the data set warrants a higher-order function, a solution may be found by approximating the function by several linear segments and solving for the fracture density of each segment of the data set.
Shape Factor, CA, Expressed as Skin, sCA
Authors: Fetkovich M.J. , Vienot M.E.
Published: December 2007

This work presents the conversion of the shape factor, CA, to a pseudosteady-state skin term, sCA. When the shape factor is expressed as a skin term, it becomes easier to see the effect that a well placement in a given drainage area will have on the wells performance. Skin factors for published drainage shapes and well locations are given.

Discussion

In attempting to calculate interference effects of well locations on production forecasts, it was found very convenient to express the shape factor, CA, as a pseudosteady-state skin term, sCA. When using pseudosteady-state flow pseudosteady-state skin term, sCA. When using pseudosteady-state flow equations, the effect of a well not located in the center of a radial or square drainage area becomes immediately apparent when the shape factor is expressed as a skin term. The general pseudosteady-state equation in terms of CA for oil, gas, or water can be written as

..........................................(1)

By using an effective drainage radius, r,', to maintain an equivalent reservoir volume

..........................................(2)

and the shape factor for a well at the center of a circular drainage area (CA =31.62), we can obtain the familiar radial flow pseudosteady-state equation

..........................................(3)

Introducing a reference shape factor term, we can write

..........................................(4)

..........................................(5)

Defining a pseudosteady-state skin factor, sCA, as

..........................................(6)

we have, referencing to the center of a circle (the classic analytical solution) with CA, ref = 31.62,

..........................................(7)

or, referencing to the center of a square (field and model situations) with CA, ref = 30.8828,

..........................................(8)

Values of scA referenced to the center of a circle or square are tabulated in Table 1. Values of CA in Table 1 were obtained from Ref. 1 Constant wellbore pressure production forecasts for wells not in the center of a circle are made conveniently by using the concept of effective wellbore radius with and from Ref. 2 and .

Nomenclature

A = drainage area, ft2 [M2] B = formation volume factor CA = shape factor D = nondarcy flow constant

JPT

February 1985

p. 321
Case Histories of Analyses of Characteristics of Reservoir Rock from Drill-Stem Tests
Authors: Ammann Charles B.
Published: December 2007

The presented case histories of analyses of characteristics of reservoir rock from drill-stem tests illustrate that drill-stem test analysis may be used to evaluate a formation within the vicinity of a wellbore. The examples presented show that an analysis will determine to a practical degree such properties as true pressures and potentiometric surfaces, transmissibilities, actual and in situ producing capacities and permeabilities, productivity index, damage ratio, production rates, distance to any apparent barrier interferences near the wellbore and the approximate drainage radius during a test.

The properties thus determined are dependable enough to enable an operator to decide just what is going on in a particular formation, if a formation is worth any effort and expense to complete for production and if a treatment of some type may be needed during completion. They are dependable enough to make comparisons of the rock matrices of different well locations in a reservoir, aiding in a determination of the degree of reservoir homogeneity.

The pressures and potentiometric surfaces determined are dependable enough to determine reservoir continuity between wells and to determine which reservoirs are within the same pressure system. Utilizing pressure-elevation graphs, gas-oil and oil-water contacts (which may not be obvious by other means such as electric logs) may be determined from the pressures obtained. In many cases the extrapolated pressures are the initial reservoir pressures, and the drill-stem test is the only means by which they are obtained.

Introduction

Four case histories were chosen to illustrate the practical usefulness of a drill-stem test analysis to determine a reservoir's characteristics and to show the limitations of an analysis. The case histories chosen illustrate the different types of drill-stern tests which may be taken. The methods and calculations used to make the analyses are presented.
Estimating Reserves for High-Rate Devonian Shale Oil and Gas Completions With Limited Production Data
Authors: Mason R. A.
Published: December 2007

Much of the activity in West Virginia in recent years has focused on the development of high-rate oil and gas completions in the naturally fractured Devonian shale. With a limited understanding of the reservoir production mechanisms, realistic estimates of oil and gas reserves early in the life of a high-rate well appeared unattainable. Early reserve estimates are necessary because typical completions produce the majority of their reserves in the first 18 months of continuous operations.

Material-balance considerations, however, can be successfully applied to high-rate Devonian shale oil and gas reservoirs to enable an estimation of reserves to an assumed abandonment pressure. The procedure uses Tracy's form of the Tarner material-balance method in conjunction with an empirically derived permeability-ratio curve. Necessary data are simply and economically collected early in the life of the well and include (1) production data for at least one continuous month, (2) corresponding initial and final measured bottomhole pressures (BHP's), (3) pressure-variant fluid properties, and (4) a representative permeability-ratio curve.
Evaluation of Silurian-Niagaran Reef Belt in Northeastern Michigan
Authors: Aminian K. , Ameri S. , Bomar R. M.
Published: December 2007

Silurian pinnacle reefs have remained the main exploration targets in the Michigan basin over the last decade. Recent discoveries have extended the reef belt into new areas in the western and northeastern parts of Michigan's lower peninsula. Meanwhile, the exploration for these reefs has continued in more developed areas of the belt in northern Michigan, southwestern Ontario, and southern Michigan.

The results of exploration activities in northeastern Michigan in Cheboygan, Montmorency, and Presque Isle counties is different from the rest of the northern portion of the belt. A detailed study used the data available from the exploration activities in this area to determine the reef belt characteristics and reserves potential in northeastern Michigan and its extension into Lake Huron.

The results indicated some interesting features, including the narrowing of the belt as it approaches Lake Huron. It was concluded that the different depositional environment during the Silurian Age had affected the development of the belt and the hydrocarbon accumulation in the pinnacle reefs in this part of the basin.
An Extended Analysis Method for Two-Pulse Tracer Logging
Authors: Anthony J. L. , Hill A. D.
Published: December 2007

Radioactive tracer logs are commonly used logs for quantitative determination of injection profiles. In particular, the velocity-shot method is used for quantitative analysis. In this technique, the transit time for the passage of a slug of radioactive tracer material between two stationary detectors is measured. From such transit times, the velocity of the fluid is calculated at various depths in the wellbore, yielding an injection profile. The accuracy of the velocity-shot method, however, is diminished by variations in wellbore diameter or by fluid exiting the wellbore between detector locations.

To increase the accuracy of radioactive tracer logging, the two-pulse method was developed. In wellboremodel experiments, pulses of a tracer material were injected into a fluid stream in a circular pipe with fluid exiting through perforations. The pulses were also monitored above and below abrupt diameter changes. The accuracies of the two-pulse and velocity-shot methods in a region of wellbore-diameter change or in a fluid-loss zone are compared on the basis of these experiments.
Technical Drilling Data Acquisition and Processing With an Integrated Computer System
Authors: Chevallier J. J. , Quetier F. P. , Marshall D. W.
Published: December 2007

Sedco Forex has developed an integrated computer system to enhance the technical performance of the company at various operational levels and to increase the understanding and knowledge of the drill crews.

This paper describes the system and how it is used for recording and processing drilling data at the rig site, for associated technical analyses, and for well design, planning, and drilling performance studies at the operational centers. Some capabilities related to the statistical analysis of the company's operational records are also described, and future development of rig computing systems for drilling applications and management tasks is discussed.
A Symmetric, Positive Definite Formulation of a Three-Dimensional Micellar/Polymer Simulator
Authors: Gupta A. Datta , Pope G. A. , Sepehrnoori K. , Thrasher R. L.
Published: December 2007

An efficient approach to compositional simulation is described. Application to micellar/polymer flooding resulted in a significant saving in computation time. A new method was developed to impose precisely the outflow boundary condition arising from continuity of flux across the reservoir/wellbore interface. In a manner analogous to classic well models, the above condition was used to define produced concentrations from the wellblock concentrations. Effects of numerical dispersion in multidimensional, multiphase, multicomponent flow and the effectiveness of a dispersion control scheme are also discussed.
Moving Elements for Transport Processes
Authors: Carey Graham F. , Mueller Alan , Sepehrnoori Kamy , Thrasher Richard L.
Published: December 2007

We consider a class of convection-dominated flows fundamental to reservoir simulation and their approximate solutions by use of finite-element techniques and moving meshes. Both the solution field and the coordinate functions enter as primary unknowns in the resulting problem statement. Hence the mesh evolves with the solution, and the method is particularly well-suited to those problems where tracking of sharp solution fronts is important. Examples of particular interest related to petroleum reservoir simulation are the model convection/diffusion, Burgers, and Buckley-Leverett equations, which are considered in the numerical studies. We consider effective solution techniques and system integration, as well as questions related to the use of constraints for limiting the permissible distortion of the mesh.
A New Approach to Limited Compositional Simulation: Direct Solution of the Phase Equilibrium Equations
Authors: Lo Tak Sing , Youngren Gary K.
Published: December 2007

A new method for solving the phase equilibrium in limited compositional models is presented. It is a direct solution algorithm based on simplified thermodynamics and can be easily implemented in existing simulators to model such mechanisms as retrograde condensation, oil stripping by gas cycling, and miscible and immiscible gas drive. In field-scale studies, the simplification in phase behavior is more than compensated for by the increase in simulator efficiency. Examples are given to illustrate the method's use in large-scale gas cycling.
Experience in the Use of 13% Cr Tubing in Corrosive CO2 Fields
Authors: Crolet J.-L. , Bonis M. R.
Published: December 2007

This paper discusses the following points in detail: the reasons for using 13% Cr steel tubing in corrosive offshore wells; the corrosion resistance to be expected with this material; the precautions to be taken both at the completion design stage and during practical implementation; the economic evaluation that can be made after 8 years of experience and that covers 140 wells; and the rationalized use of 13% Cr steel tubing based on early prediction of the corrosivity of future wells.
Inhibitor Film Persistence Measurement by Electrochemical Techniques
Authors: Choi H. J. , Cepulis R. L.
Published: December 2007

A technique that uses corrosion-potential, Φcorr, measurements was developed to evaluate rapidly the film persistence of commercial adsorption-type inhibitors for downhole tubular treatment. It was demonstrated that the Φcorr measurement revealed the progressive change with time of inhibitor film in aqueous moving fluids. The advantages of Φcorr measurements are that film effectiveness can be monitored continuously with a simple device and that they are nonintrusive.

Additional results of the tests showed that dissolved O2, CO2, and fluid flow drastically degraded the effectiveness of inhibitor film, and higher concentrations of inhibitors provided better performance. These indicate that simulation of process conditions is a prerequisite when the film persistence of commercial adsorption-type inhibitors is determined in a laboratory.
Effects of Commonly Used Oilfield Chemicals on the Rate of Oxygen Scavenging by Sulfite/Bisulfite
Authors: Braga T. G.
Published: December 2007

The effect of common oilfield biocides, corrosion inhibitors, scale preventives, and alcohols on the rate of O2 scavenging by sulfite/bisulfite is described. Emphasis is placed on the effect of the functional group of each of the chemical types. An attempt is made to explain the results in terms of the free-radical mechanism.
Natural Gas Hydrates in the Alaskan Arctic
Authors: Godbole S. P. , Kamath V. A. , Ehlig-Economides C.
Published: December 2007

The occurrence of in-situ natural gas hydrates in the arctic North Slope of Alaska is governed by several thermodynamic and geologic parameters, such as mean annual surface temperature, geothermal gradients above and below the base of the permafrost, pore-fluid salinity, permafrost base depth and temperature, subsurface pressure, and composition. Accurate knowledge of these parameters is necessary to determine the depths and thicknesses of zones of potential hydrate occurrences. The role of the parameters Is discussed in this paper. To determine the hydrate-stability zone, a nomogram has been developed and has been used for several Alaskan wells. For further delineation of gas hydrates, the neutron-transit-time crossplots have served as a valuable tool. To quantify gas hydrate deposits in terms of thickness, porosity, and saturation; use of neutron- and sonic-porosity-correction factors and Pickett crossplots is recommended.
A Comparison of Steamflood Strategies: Five-Spot Pattern vs. Inverted Nine-Spot Pattern
Authors: Ziegler Victor M.
Published: December 2007

This paper describes the use of a black-oil, thermal simulator to compare steamflood development using five-spot and inverted nine-spot patterns. The input data selected were representative of a homogeneous heavy-oil reservoir. This study considered three different development strategies: conventional pattern steamflooding, pattern steamflooding with infill drilling, and steamflooding with infill drilling and pattern realignment.

Comparison of pattern steamfloods indicates that at close well spacing (1.25 acres/well [0.5 ha/well]), the inverted nine-spot recovers more oil than the five-spot. Steam breakthrough and oil production are accelerated for the nine-spot relative to the five-spot pattern. At larger well spacing, however, oil recovery from the five-spot pattern exceeds that from the nine-spot. Conversion of a five-spot pattern to an inverted nine-spot increases and accelerates oil recovery. Processing of multiple sands will improve the effectiveness of this infill drilling strategy.

A development strategy using inverted nine-spot patterns on large well spacings (2.5 to 5.0 acres/well [1 to 2 ha/well]) that yields improved oil recovery compared with conventional five-spot steamflood development was identified. This strategy uses infill drilling and pattern realignment to improve steamflood performance.
Visualization of Laboratory Corefloods With the Aid of Computerized Tomography of X-Rays
Authors: Hove A. O. , Ringen J. K. , Read P. A.
Published: December 2007

This paper presents the use of X-ray tomography to inspect a series of laboratory core-displacement tests. Saturation profiles in thin longitudinal planes of view (slices) in the core are followed as a function of time.

Immiscible and miscible displacements in single core plugs and butted composite plugs are presented. Effects of heterogeneity of the core, dispersion of flood fronts, and end effects are observed and discussed. The technique has a large potential to improve the understanding of fluid displacement processes in laboratory core experiments.
Semilog Analysis of Gas Well Drawdown and Buildup Data
Authors: Reynolds A. C. , Bratvold R. B. , Ding W.
Published: December 2007

The pseudopressure function is well understood and widely used for analyzing gas well drawdown and buildup data. The usefulness of the pseudotime function for analyzing buildup data with drawdown type curves has also been established. Unfortunately, the pseudotime concept is often incorrectly applied when drawdown data are analyzed by semilog methods. This work provides information on appropriate definitions of dimensionless time that yield accurate analysis of data obtained under radial flow conditions. From the practical viewpoint, the most important result is that two Horner time ratios exist—one based on a normalized shut-in time and one based on shut-in pseudotime—that yield an accurate analysis of buildup data, including the correct determination of average pressure using the liquid Matthews-Brons-Hazebroek (MBH) functions.
Field Performance of Ultralightweight Cement Slurry Compositions Used in the UAE
Authors: Murali B. N. , Tanner C. H.
Published: December 2007

Operators in the UAE have achieved a high degree of success with a high-strength microsphere (HSMS) cement additive to deal with lost circulation during drilling and/or cementing. Slurries made with the additive maintain good strength properties at low weights.
Multiple Regression Approach To Optimize Drilling Operations in the Arabian Gulf Area
Authors: Al-Betairi Emad A. , Moussa Mohamed M. , Al-Otaibi Saud
Published: December 2007

This paper reports a successful application of multiple regression analysis, supported by a detailed statistical study to verify the Bourgoyne and Young model. The model estimates the optimum penetration rate (ROP), weight on bit (WOB), and rotary speed under the effect of controllable and uncontrollable factors. Field data from three wells in the Arabian Gulf were used and emphasized the validity of this model. The model coefficients are sensitive to the number of points included. The correlation coefficients and multicollinearity sensitivity of each drilling parameter on the ROP are studied.
Fractured Reservoir Evaluation Using Monte Carlo Techniques (includes associated paper 16991 )
Authors: Sears G.F. , Phillips N.V.
Published: December 2007

Pro forma cash-flow analysis of petroleum ventures usually isconsidered as a dterministic model. In the last 10 years, Monte Carlo analysishas allowed the introduction of probability distributions of input variables inplace of single-valued functions. Reserve determination and rate scheduling inthese current Monte Carlo techniques have relied on the volumetric formula, which works well in nonfractured reservoirs.

Recent massive drilling in fractured reservoirs has rendered this approachunusable. This paper develops a variation of the Arps rate-cumulative equationas a basic model for the determination of the distribution of original reservesand the decline rates. Continuation of the Monte Carlo technique into netpresent value analysis and internal rate of return (IRR) is also developed.

Introduction

Estimating the profitability of petroleum ventures is a risky business atbest. The prices of oil and gas are not the least of many uncertain variablesin any standard cash-flow model. Friedman used the idea of Monte Carlosimulation in competitive bidding strategy. Hertz popularized teh idea of MonteCarlo modeling to treat uncertainty in a business situation. Several authorshave applied this concept to petroleum ventures, particularly in the earlystages of development of a reservoir or even during exploration. The basicmodel used in these calculations has always been the volumetric model outlinedbelow. That approach works well in conventional reservoirs where porosity, netthickness, and recovery factor can be measured or estimated. In tight ornaturally fractured reservoirs, however, the volumetric approach fails becausethe hydrocarbons are not in an isotropic, homogeneous matrix as in conventionalreservoirs but instead are confined largely to the fracture system. A MonteCarlo model for fractured reservoirs using the general approach is outlinedbelow, but it is based on the Arps rate-cumulative and rate/time empiricalequations. The model is used to determine both the distribution of reserves andthe extraction schedule that woudl result. These lead to computation of the netpresent value of the reserves.

The volumetric formula is based on the equation (Equation 1)

P. 71^
Casing Heading in Flowing Oil Wells
Authors: Torre A. J. , Schmidt Z. , Blais R. N. , Doty D. R. , Brill J. P.
Published: December 2007

Casing heading, an unsteady flow in oil wells completed without packers, occurs when both gas and liquid superficial velocities are low. A hydrodynamic model is presented that simulates laboratory data for the cases considered. Results confirm that heading occurs for low superficial gas and liquid velocities and that choking re-establishes stability.