bluuebunny/crossref_metadata_2025 huggingface dataset:
The Successful Use of Austenitic Stainless Steels in Sea Water
Authors: Moller G.E.
Published: December 2007

Moller, G.E., International Nickel Co., Inc., Torrance, Calif.

Austenitic stainless steels are providing excellent trouble-free service in sea water for pumps, propellers, valves. and other marine equipment. propellers, valves. and other marine equipment. Occasionally, a failure occurs as the result of deep localized pitting in a crevice. Data are given showing that austenitic, ferritic. and martensitic stainless steels suffer pitting in crevices and under deposits in quiescent sea water. Austenitic stainless steels remain free from attack in high-velocity sea water. Low-purity ferritic and the martensitic stainless steels frequently pit in high-velocity sea water. Crevice corrosion can be controlled effectively with cathodic protection from iron, zinc. aluminum or magnesium galvanic anodes or impressed current cathodic protection by polarization to -0.6 v vs Calomel. Austenitic stainless steel performs well in many situations because it is a component of a multi-alloy assembly utilizing iron or steel. Examples from field experience arc given.

Introduction

During the past decade, there has been a growing use of austenitic stainless steel in marine equipment. Most applications have been successful but an unexpected failure has been observed occasionally. It is the purpose of this paper to describe when and how to use austenitic stainless steel with success. The selection of stainless steels appears to result from the engineering requirements of new, advanced, high-speed, high-reliability commercial, pleasure, and military craft. Ocean science and pleasure, and military craft. Ocean science and engineering, offshore oil production, fishing, and ocean mining are also contributing to the selection of stainless steels for sea-water applications. The increasing use of stainless steel in the marine environment is found in work-boat propellers, pump components, bow thrusters, valves, shafting pump components, bow thrusters, valves, shafting and shaft components, through-hull fittings, parts on data-gathering buoys, fasteners, and housings of oceanographic instruments. When austenitic stainless steel has given good, corrosion-free service, it is most often found to be used as a key component in a multi component, multi-alloy assembly or system receiving the benefit of built-in cathodic protection. For example, in Fig. 1 a cast Type 304 (Alloy Casting Institute CF-4) propeller is being used on a steel seagoing tugboat with zinc anodes attached to the rudder. Fig. 2 shows a cast ACI CE-30 power-plant sea-water circulation-pump impeller free power-plant sea-water circulation-pump impeller free of any corrosion after 6 years of service that was used in combination with an austenitic cast-iron suction bell and diffuser.

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Considerations Concerning Bank Financing of Oil and Gas Properties
Authors: Warren J.E.
Published: December 2007

Introduction

Over the years, technological development, expanding markets and competition have kept the petroleum industry dynamic and progressive, fulfilling a vital part in the nation's expanding economy. Looking to the future, indications point to a greater and greater demand for petroleum products to meet the growing needs of a larger population and an increasing per capita dependency upon energy. Expansion of facilities in all branches of the industry will be needed as demand grows. This expansion will increase financial requirements, for there is a continual need of capital to make it all possible. A major share of these capital requirements will be needed to explore for and develop increasing amounts of crude oil and natural gas.

This paper will cover first, the banking concept as it applies to all oil property loans; second, current considerations concerning specific loan situations; and, finally, considerations of future political and economic forces as they are related to oil and gas loans.

Banking Concept Concerning Oil Property Loans

We have all heard in the oil country allegations such as "tight bankers" and "bankers only loan money on cinches". This is a natural human reaction, for all of us accept easily those things that conform to our own thinking and forward our own interests, and reject readily those contrary to our beliefs and interests. The misunderstanding arises because banking and oil producing, by their very natures, must operate in different business climates. Actually, banking and the oil business do not have conflicting objectives, for bankers are anxious to do all they can to build relationships and promote the welfare of their oil clients. They must, however, confine their judgment within limits imposed by their over-all responsibilities. So, perhaps it might be well at this point to compare the two businesses - banking and petroleum - and point out the differences in business climate in which each one is permitted to operate.
New Material and Technique for Matrix Stimulation in High-Water-Cut Oil Wells
Authors: Chang F. F. , Love T. G. , Affeld C. J. , Blevins III J. B. , Thomas R. L. , Fu D. K.
Published: December 2007

A new process has been developed that effectively diverts acid away from zones with high water saturation into hydrocarbon zones. This process is designed to increase the success of matrix acidizing treatments. Because of the relative permeability effect, aqueous acid predominantly enters the zone with highest water saturation, resulting in stimulation of the water zones and an increase of water cut. Although foam can be used to divert acid from the "aquifer" to the damaged oil zones, nitrogen is not readily available in some areas and additional handling equipment is required. A new nonparticulate, nongaseous material has been developed to effectively divert acid away from highly water saturated zones. The material forms a highly viscous plug when it contacts water in the matrix yet degrades when mixed with oil in the matrix of the formation.

In this article we discuss in detail the diversion technique from both laboratory testing and field studies. Laboratory tests conducted in a dual-core flow apparatus showed excellent diversion from a water-rich zone to an oil-rich zone, as well as from a high-permeability formation to a low-permeability formation. Case histories showed the new material successfully diverted acid and stimulated the carbonate formations in the Permian Basin.
Laboratory Development and Field Application of a Novel Water-Based Drill-In Fluid for Geopressured Horizontal Wells
Authors: Dobson J. W. , Harrison J. C. , Hale A. H. , Lau H. C. , Bernardi L. A. , Kielty J. M. , Albrecht M. S. , Bruner S. D.
Published: December 2007

Research has identified a novel water-based drill-in fluid for drilling and completing geopressured horizontal wells. This fluid has a unique combination of properties which make it especially suitable for geopressured applications. They include the use of calcium and/or zinc bromide as a base brine, minimal concentration of calcium carbonate as bridging material, low plastic viscosity, tight fluid loss control, good filter-cake properties, and excellent return permeability. This drill-in fluid has been used successfully to drill a 1,200-ft production interval, 4.75-in. diameter wellbore in the Gulf of Mexico with a system weight of 13.2 lbm/gal, bottomhole temperature of 185°F, and a 1,400 to 1,700 psi overbalance. The system functioned very well in both the drilling and the completion operations. Fluid rheology was easily maintainable and the hole conditions were excellent without torque or drag problems. Initial production data suggest that the well is producing at expected rates with low drawdown pressure.
Water Injection Profile Modification in a Layered Reservoir With Polymer Treatment
Authors: El-Hadidi S. M. , Falade G. K. , Dabbouk C. , Al-Ansari F.
Published: December 2007

The main focus of this paper is the applications of polymer treatment in controlling injectivity and the improvement of the nearwellbore injection profiles.

Reservoir high-permeability zones causing distortions of water injection profiles at the wellbore, and the possible existence of layer barriers, were identified with conventional investigation tools such as openhole logs, production logging tools, formation, and microscanners.

A polymer screening procedure was put in place so that appropriate polymer formulations that can reduce fluid mobility in the high-permeability zones at the near-wellbore region can be identified. The use of these polymer formulations facilitated the improvement of wellbore injectivity profiles.

The field performance of the polymer treatment program was ascertained by the use of a monitoring program that combined the application of the production logging tools and well-test analyses.
A Note on IMPES and Some IMPES-Based Simulation Models
Authors: Coats K. H.
Published: December 2007

The generalized IMPES method applies to simulation models involving any number of conservation equations. The IMPES pressure equation is a linear combination of the linearized conservation equations. This article shows the generality, simplicity, uniqueness, and derivational brevity of that equation. The associated IMPES reduction vector leads directly to the value of total compressibility in a multiphase gridblock. That compressibility in turn gives several error checks on black oil pressure/volume/temperature (PVT) data.

Three IMPES-type compositional models are compared and found to be very similar, with moderate differences in efficiencies and generality. An example problem serves two comparative purposes related to IMPES model efficiency.
Frontier Geothermal Drilling Operations Succeed at 500°C BHST
Authors: Saito Seiji , Sakuma Sumio
Published: December 2007

The Japanese government-funded geothermal exploration Well WD-1A reached 3729 m at total depth, where the bottomhole static temperature is more than 500°C. A trajectory correction run was carried out with a positive displacement motor and measurement while drilling tool where the formation temperature is greater than 350°C. The combination of large surface mud containers and sufficient mud cooling equipment were used to cool return mud from the well. A top drive system was used to cool the bottomhole assembly while running each drillpipe stand in the hole. A borehole dynamic temperature experiment and drill bit tests were carried out in this well.
Generalized 3D Analytical Model for Transient Flow in Compartmentalized Reservoirs
Authors: Rahman N. M. A. , Ambastha A. K.
Published: December 2007

A new generalized transient-flow model for a three-dimensional (3D) compartmentalized system with n compartments has been developed analytically. Each compartment may have distinct rock and fluid properties and may produce through a number of partially penetrating wells. A partially communicating fault or barrier causing poor hydraulic communication between a pair of adjoining compartments is modeled as a thin skin at the interface. Production rates and conditions at the extreme boundaries are considered to be time variant. The solution was also validated by examining a few limiting cases. An example problem with stacked channel realization was studied. A simple method for detecting the poorly drained compartments from the extended drawdown data was developed. This has also lead to an estimation of hydrocarbon-pore volume in each compartment.
Geostatistical Analysis of Permeability Data and Modeling of Fluid-Flow Effects in Carbonate Outcrops
Authors: Jennings J. W. , Ruppel S. C. , Ward W. B.
Published: December 2007

Permeability data from Permian dolomitized shallow-water platform carbonate outcrops in west Texas and New Mexico exhibit two to five orders of magnitude variability, most of which occurs within distances of a few feet [1 to 2 m] within single rock-fabric units. A variety of longer-range features are also observed, including vertical interbed average-permeability contrasts, 140- to 180-ft [42- to 54-m] lateral periodicities, and up to 2,700-ft [810-m] lateral trends. The short-range heterogeneities can be modeled with K-Bessel semivariograms having asymptotic power-law behavior at the origin. The periodicities can be modeled with "hole-effect" J-Bessel semivariograms.

Stochastic two-dimensional areal and vertical cross-section models explore the effects of these heterogeneities. Fluid-flow simulations demonstrate that some long-range features control overall flow behavior even when short-range variability composes most of the variance. The short-range heterogeneities produce local smearing of displacement fronts.
Production-Induced Compaction of a Sandstone Reservoir: The Strong Influence of Stress Path
Authors: Hettema M. H. H. , Schutjens P. M. T. M. , Verboom B. J. M. , Gussinklo H. J.
Published: December 2007

The decrease of pore pressure during hydrocarbon production (depletion) leads to compaction of the reservoir, which in turn changes the stresses acting on the reservoir. The prediction of reservoir compaction and its consequences is usually based on laboratory experiments performed under uniaxial strain conditions, i.e., allowing no lateral strain during depletion. Field data of the Groningen gas field (The Netherlands) indicate that the stress development of the field deviates significantly from the stress path under uniaxial strain conditions. Laboratory experiments show that the applied stress path has a strong influence on the depletion-induced compaction behavior. We discuss the consequences of these results for the field compaction behavior by considering the responsible deformation mechanisms active in reservoir and experiment. The new Groningen field data, in combination with our experimental results, provide an explanation for the difference between the prediction of compaction and subsidence based on uniaxial experiments and the measurement of compaction and subsidence in the Groningen field. With the use of the new stress path, the predicted and measured compaction and subsidence are in agreement.
A Relation Between Gamma Radiation and Permeability, Denver-Julesburg Basin
Authors: Rabe C.L.
Published: December 2007

Introduction

The Muddy and Dakota sands, more commonly known as the "D" and "J" sands, respectively, of the Denver-Julesburg Basin are correlative over a large area. It is reasonable to believe, therefore, that depositional environment throughout the Basin was comparable. Local variations in sand development do occur, however, and productivity is often governed by permeability as well as structural position. Experience indicates permeability is commonly a function of cementing material. While cases of siliceous or calcareous cementing have been observed, the bonding material is, for the most part, clay. Under the latter circumstance, clay should bear some relation to permeability. Similarly, gamma radiation should bear some relation to the amount of clay. This study was undertaken to determine if a cross relation exists between gamma radiation and permeability.

Results of Investigation

A qualitative relation does exist between gamma radiation and permeability for clay-bonded Muddy and Dakota sands of the Denver-Julesburg Basin. This is illustrated graphically by Fig. 1, which shows corrected gamma ray deflection vs permeability for five wells over an area approximately 50 miles long and 8 miles wide. The "corrected" gamma ray deflection cannot be read directly from the gamma ray survey in all cases. It became apparent early in the investigation that methods would have to be developed for converting all gamma ray surveys to a common deflection scale and to correct for thin bed effects.

Common Scale Deflection

Because all logs are not recorded in the same calibration units or at the same sensitivity, it was felt they could be most readily converted to a common scale by measurement of deflection in inches from zero. Initially, four wells in the Jacinto field of Nebraska were carefully correlated, and selected intervals were planimetered to obtain average deflections.
Fully Coupled Analysis of Well Responses in Stress-Sensitive Reservoirs
Authors: Chin L. Y. , Raghavan R. , Thomas L. K.
Published: December 2007

A fully coupled geomechanics and single-phase, fluid-flow model is developed to evaluate the combined effects of stress, fluid flow, and reservoir property changes on well responses in stresssensitive reservoirs. In particular, we pay attention to the interpretation of pressure buildup tests and to changes in the production characteristics of wells. In general, for weak hydrocarbon reservoirs that exhibit nonlinear, elastic and plastic constitutive behaviors, and stress-dependent properties such as permeability and porosity, the physical effect contributed from geomechanics may not be ignored in well test analysis. The coupled interaction between geomechanics and reservoir fluid production markedly affects the stress state and reservoir properties. Because we are using a coupled, numerical model, we evaluate the consequences of using simplified relationships (e.g., permeability as a function of pressure). Numerical analyses are performed to quantitatively assess the impact of reservoir stress sensitivity on practical well test problems. The key variables investigated in the study, that are important in evaluating stress-sensitive reservoirs, include permeability, porosity, and constitutive behaviors of reservoir rock including hysteresis and loading conditions. The development of high-stress regions around wellbores and its consequences on well performance are considered. The numerical results from the study indicate that for analyzing highly stress-sensitive reservoirs, a fully coupled geomechanics and fluid-flow modeling approach is necessary and the developed model employed in this study provides such a tool.
The Effect of a Short Term Shut-In on a Subsequent Pressure Build-Up Test on an Oil Well
Authors: Nisle Robert G.
Published: December 2007

In conducting a pressure build-up test on an oil well, it is often necessary to shut-in the well for a short time prior to initiation of the test. The effect of such a short term shut-in on the resulting pressure build-up curve is derived. The derivation is based on the Kelvin point-source solution and is a straight forward extension of the fundamental theory.

The magnitude of the effect is evaluated and illustrated by an example. It is shown that if the production subsequent to the short term shut-in is at least 10 times the duration of the shut-in, the effect will be less than 10 per cent.

Introduction

It often happens that before a pressure build-up test can be made an additional valve must be mounted on the wellhead, or on arrival at the well, it might be learned that the well had been shut-in several hours the previous day because of a shortage of tankage. In such cases the question is "How will such an interruption of production affect the results of a pressure buildup test?" This work explains how to take account of such a short term shut-in in order that the test can proceed without further delay.

The solution presented here makes use of the Kelvin point-source solution used by Horner in his treatment of the pressure build-up in wells. Use is also made of the super-position theorem.

Mathematical Derivation

The well is assumed to have been in production at a constant rate for a relatively long time (several days or more). It is then shut-in for a short time, after which it is again placed in production at the previous constant rate. It continues to produce at this rate until shut-in for a pressure build-up test.

The Kelvin point-source solution is expressed by Eq. 1.
Computational Fluid Dynamics (CFD) Study of Bubble Carry-Under in Gas-Liquid Cylindrical Cyclone Separators
Authors: Erdal F. M. , Shirazi S. A. , Mantilla I. , Shoham O.
Published: December 2007

The gas-liquid cylindrical cyclone (GLCC©) separator is an attractive compact separator alternative to the conventional vessel-type separator. Thus, it is important to develop predictive tools for design and to be able to improve the technology of the GLCC. Previous studies on the GLCC have focused on mechanistic models capable of predicting the operational envelope for liquid carryover and on the understanding of the flow field in the GLCC. The main objective of this work was to investigate the behavior of small gas bubbles in the lower part of the GLCC, below the inlet, and the related gas carry-under phenomena. This investigation was performed by flow visualization and by using a commercially available computational fluid dynamics (CFD) code. Simulations of single-phase and two-phase flows were carried out and bubble trajectories were obtained in an axisymmetric geometry that represents the GLCC configuration. Bubble trajectory analysis was used to quantify the effects of the important parameters on bubble carry-under. These include bubble size, ratio of the GLCC length below the inlet to diameter, viscosity, Reynolds number, and inlet tangential velocity.
Kinetics of the Primary Reaction of HF on Alumino-Silicates
Authors: Gdanski R. D.
Published: December 2007

The standard description of HF acidizing chemistry clearly demonstrates a primary and secondary reaction of HF with alumino-silicates.1–6 Field experience has taught our industry that possible precipitation during the secondary reaction can adversely affect treatment success,7,8 especially in formations with high K-feldspar content9 or temperatures above 300°F. Recent work has also been reported on the existence of a third, or tertiary reaction of HF with alumino-silicates.10

In this paper determination of the rate law and kinetics for the primary reaction of HF on sand, clay, and feldspar over a broad temperature range is reported. The rate law for the primary reaction of HF with sand had no HCl dependence and was second order in HF concentration. The rate law for the primary reaction of HF with clay and feldspar was assumed to also have no HCl dependence and was adequately described by a first order in HF concentration. In addition, a mass transfer equation for reactive fluids flowing through porous sandstone media is proposed. These findings were made possible by recently applied experimental techniques including 19F nuclear magnetic resonance (NMR) spectroscopy,10 fractional pore-volume flow experiments,11 and an accurate knowledge of the HF stoichiometry.12 Laboratory findings have been verified through detailed analyses of flowback samples from field treatments.13
Correlation of Emulsion Stability With Phase Behavior in Surfactant Systems for Tertiary Oil Recovery
Authors: Vinatieri James E.
Published: December 2007

This paper describes a study of the emulsions which could occur during a pilot surfactant flood, such as that conducted by Phillips Petroleum Co. in the North Burbank Unit, Osage County, OK. The phase behavior of this surfactant system can be characterized by three types of microemulsions, with the transition from one type to another being a function of the salinity. The rate at which emulsions coalesce was seen to correlate directly with the type of microemulsion.

Coalescence was slow for macroemulsions at low salinities, rapid at intermediate salinities (where the final state was a three-phase system), and varied from slow to rapid at salinities above the three-phase region. Knowledge of the correlation between phase behavior and emulsion stability can be useful in treating macroemulsions produced during a surfactant flood.
Formulation of a General Multiphase, Multicomponent Chemical Flood Model
Authors: Fleming Paul D. , Thomas Charles P. , Winter William K.
Published: December 2007

A general multiphase, multicomponent chemical flood model has been formulated. The set of mass conservation laws for each component in an isothermal system is closed by assuming local thermodynamic (phase) equilibrium, Darcy's law for multiphase flow through porous media, and Fick's law of diffusion. For the special case of binary, two-phase flow of nonmixing incompressible fluids, the equations reduce to those of Buckley and Leverett. The Buckley-Leverett equations also may be obtained for significant fractions of both components in the phases if the two phases are sufficiently incompressible. To illustrate the usefulness of the approach, ã simple chemical flood model for a ternary, two-phase system is obtained which can be applied to surfactant flooding, polymer flooding, caustic flooding, etc.
Subsurface Sealing of Tubing Thread Leaks
Authors: True Martin E. , O'Reilly W.M.
Published: December 2007

A technique, equipment, and a compound have been developed and field tested for sealing tubing joint thread leaks without removing the tubing from the well. This eliminates the necessity of killing the well with possible damage to the producing formation, which could result if it were exposed to drilling mud. A thread sealing compound, developed and tested in the laboratory, is introduced into the tubing and squeezed into the joint to eliminate the leak. A high percentage of successful field applications have effected an appreciable cost reduction in repairing leaking tubing strings in East Texas and in the Louisiana Gulf Coast area.

Introduction

In producing oil and gas wells the industry has been plagued with a never ending problem of tubing connection leakage. This situation is becoming increasingly more significant as more gas wells are placed on production and as higher pressures are encountered at greater depths of current drilling.

Substantial progress has been made in minimizing thread leaks by careful handling and cleaning of joints and by the use of improved sealing compounds in combination with controlled makeup. But even with the use of the best known methods and sealing materials during initial makeup, occasional leaks through tubing joint threads appear inevitable. In some instances, tubing joints in high-pressure gas wells have been found to leak gas at relatively less pressure than that at which the tubing had been tested satisfactorily using liquid.

Many expedients have been employed to prevent the physical replacement of tubing when leaks have developed. Perhaps the most commonly used is the sodium silicate treatment in which the solution is lubricated into the tubing to form a crystalline plug in the leak. Generally, any benefit realized is of a temporary nature.

In addition to field studies on handling and makeup of tubing, extensive laboratory work has been undertaken on the development and testing of thread dopes. Also, substantial effort has been devoted to testing tubing joints using high-pressure gas as a pressure medium. The results of this work have emphasized that tubing joints are susceptible to occasional leaks, especially when subjected to relatively high differential pressures.

To cope with the problem of leaking connections, an extensive investigation was undertaken to devise means of sealing leaks without removing the tubing from the well and without reducing the inside diameter of the tubing. The purpose of this paper is to present a technique, together with the associated equipment and compound, which have been developed for effecting a seal of leaking tubing in place.
Reverse Combustion Instabilities in Tar Sands and Coal
Authors: Gunn Robert D. , Krantz William B.
Published: December 2007

A linear stability analysis shows that reverse combustion in coal and tar sands is only conditionally stable for mobility ratios less than one. However, high air-flow rates and gas generation at the combustion front can be stabilizing influences. For unstable operation, an estimate of the size of the reverse combustion channel may be obtained from the curve for the most highly amplified wave length. This provides a method for calculating the air flux, combustion front velocity, and rate of progress of the burn front.

Recently the U.S. DOE Laramie Energy Technology Center (LETC) and Sandia Laboratories obtained experimental data about reverse combustion from a field test of in-situ coal gasification at Hanna, WY. These data show that 9.7 days were required for the development of a reverse combustion path 68 to 70 ft in length. The stability theory developed in this work predicts a length of 64 ft for this same 9.7-day period. In addition to quantitative predictions, stability theory provides an explanation of certain puzzling qualitative observations concerning reverse combustion.
Producer-Engineer-Purchaser... A Case History
Authors: Kubitz John R. , Shearin H.M.
Published: December 2007

Seldom do circumstances present an opportunity to report a complete sequence of management and technological events involving geology, discovery, evaluation, development planning and presentation for sale of products from a major natural gas resource. The Ozona Gas area, Crockett County, Tex., may well represent a classic example of

- geological study and successful interpretation following an offset failure;

- air drilling, limited entry fracturing, and modern completion techniques resulting in a significant reduction in per well costs and increased initial production potentials;

- comprehensive engineering study during and following the use of extensive well testing and fluid sample analyses, special core analysis and radioactive tracing techniques;

- evaluation of reserves based on total effective net productive formation throughout a 70,000-acre area; and

- recommendations for developing dry gas and by-product volumes available for transmission and processing during a 20-year period. All technical and economic data were analyzed and summarized for presentation and use in determining optimum development programs through electronic data processing and computing equipment.

Introduction

The Ozona area is located in Crockett County, in West Texas, about 130 miles southeast of Midland and immediately south and southwest of the town of Ozona (Fig. 1). The first significant well in this area was drilled during late 1939. Subsequent drilling of 14 additional wells failed to discover any sizeable reserves. These wells were all drilled using mud as the drilling fluid, with the exception of one air-drilled hole. All operators overlooked the principal shallow pay zone, the Canyon sand at approximately 6,500 ft, in an effort to establish the deeper Strawn or Ellenburger production. These early wells took up to six months to drill and log with an average drilling time of approximately four months/well. These expensive wells helped Crockett County to become known as the graveyard of the West Texas oil industry. A group, consisting mainly of Delta Drilling Co., Odessa and Tyler, Tex., Johnson and Lindley, Houston, Tex., and Pauley Petroleum Inc., Los Angeles, Calif., entered the area during mid-1961 with the following drilling and development sequence. The initial attempt to establish production in the area appeared to bear out the futility of drilling this area after drilling and suspending the first test during 1961. This well, the Friend No. l, was spudded July 13, 1961 and suspended on Aug. 5, 1961 after finding the Ellenburger too low for commercial production.

JPT

P. 719ˆ
An Implicit Treatment of Upscaling in Numerical Reservoir Simulation
Authors: Guedes S. S. , Schiozer D. J.
Published: December 2007

This paper presents a multiscale computational model for multiphase flow that implicitly treats upscaling without using pseudofunctions. The model overcomes some practical difficulties related to use of traditional pseudocurves by executing the upscaling and solution processes in one step and taking into account changes in the numerical model in an adaptive manner.
Removal of Asphalt Deposits by Cosolvent Squeeze: Mechanisms and Screening
Authors: Minssieux Louis
Published: December 2007

Performance improvement of usual solvents for asphalt deposits was investigated in an effort to optimize squeeze treatments of formations damaged with asphaltenes. The approach adopted for increasing the solvent power for asphaltenes of such solvents as xylene was to design solvent mixtures with a polarity adjusted to specific chemical features of asphaltenes contained in the crude oil considered. For that purpose, Hansen's theory was used as a guide in defining the composition of cosolvents suitable for asphaltenes. In addition, to increase solvency and to disperse asphaltenes, proper additives were used as a means to create hydrogen bonding with the heteroatoms present in the asphaltene chemical structure or to modify the intermolecular interactions involved in asphaltene aggregation.

Laboratory screening of cosolvents involved four types of tests that were based on the physical/chemical mechanisms deemed predominant in a squeeze operation (i.e., the solvency of asphaltenes, the ability to desorb the asphaltenes adsorbed onto minerals making up the reservoir rock, and the capacity to maintain dispersion of the asphaltenes within the organic phase). Several cosolvents, with a few percent commercial chemicals containing an alcohol or amine functional group in their molecules, were found to exhibit the required properties vs. either solid extracted asphaltenes or well deposits.

The final cosolvent efficiency was checked at reservoir temperature in squeeze experiments carried out in core samples. After a permeability damage occurred during asphaltenic crude oil flow, the remedial effects of squeezes of different cosolvents were evaluated. Several examples illustrate the improvement gained with the designed cosolvents and additives in restoring part of the oil permeability and in reducing the in-situ asphaltene deposition accompanying crude oil flow through core samples.
Upscaling Immiscible Gas Displacements: Quantitative Use of Fine-Grid Flow Data in Grid-Coarsening Schemes
Authors: Darman N. H. , Durlofsky L. J. , Sorbie K. S. , Pickup G. E.
Published: December 2007

This paper presents and assesses grid-coarsening schemes based on the quantitative use of fine-scale two-phase-flow information. The basic approach is motivated from a volume-average analysis of the fine-scale saturation equation including gravitational effects. Extensive results for layered systems are presented. We show that coarse-grid simulation error correlates closely with specific subgrid quantities involving higher moments of fine-grid variables, which can be computed from the fine-scale simulations. With formation of a coarse grid that minimizes the appropriate subgrid property, optimal coarse-scale descriptions can be generated. The overall approach is shown to be applicable to coarse-scale descriptions with either rock or pseudorelative permeability curves. The accuracy of the coarse-grid calculations is, however, significantly better when pseudofunctions are used. The method is applied to determine the optimal number and configuration of coarse-grid layers in more general cases and it is shown that coarse-grid results do not always improve as the number of coarse layers is increased.
Compressibility of Natural Gases
Authors: Trube Albert S.
Published: December 2007

The purpose of this paper is to clarify the definition of compressibility and to present a uniform basis upon which instantaneous compressibilities of liquids and gases can be compared. The equations gaverning the instantaneous compressibilities of imperfect gases are derived and the concept of pseudo-reduced compressibility is introduced. Part of the data presented by Brown, Katz et al on compressibility factors for natural gases has been rearranged. A graph of pseudo-reduced compressibility vs pseudo-reduced pressure for various pseudo-reduced temperatures is presented. The need for additional work in relating the compressibilities of liquids and gases is discussed.

This information should be of value to reservoir engineers in making non-steady state performance calculations in gas reservoirs. It should be of further use in pointing the direction for additional research in the nature of liquid and gas compressibilities.

Introduction

With the increasing use of steady and non-steady state well and reservoir data, there is a corresponding increase in the importance of the various factors entering into such calculations. Increasing emphasis is being placed on the necessity for obtaining reasonably accurate estimates of the physical properties of the reservoir fluids well in advance of the more accurate laboratory data.

One such factor is the isothermal coefficient of expansion of the media which are transmitting and attenuating the non-steady state pressure waves. The average isothermal coefficient of expansion, or "compressibility" is a complex function controlled by the physical properties of the formation and the fluids contained therein. The isothermal expansion coefficients for reservoir gases are usually quite variable, in many cases being highly-pressure sensitive. The coefficients for reservoir liquids tend to be pressure sensitive, but not nearly so much as reservoir gases. The coefficients for solids, usually expressed in terms of a "modulus of elasticity" are relatively insensitive to pressure variations within their elastic limits. For this reason, and also because many previous applications have been limited to relatively small pressure ranges, there has been a tendency to ignore the variable nature of isothermal expansion coefficients and treat them as constants.
Principal Component Analysis Applied to 3D Seismic Data for Reservoir Property Estimation
Authors: Scheevel J. R. , Payrazyan K.
Published: December 2007

We apply a common statistical tool, Principal Component Analysis (PCA) to the problem of direct property estimation from three-dimensional (3D) seismic-amplitude data. We use PCA in a novel way to successfully make detailed effective porosity predictions in channelized sand and shale.

The novelty of this use revolves around the sampling method, which consists of a small vertical sampling window applied by sliding along each vertical trace in a cube of seismic-amplitude data. The window captures multiple, vertically adjacent amplitude samples, which are then treated as vectors for purposes of the PCA analysis. All vectors from all sample window locations within the seismicdata volume form the set of input vectors for the PCA algorithm.

Final output from the PCA algorithm can be a cube of assigned classes, whose clustering is based on the values of the most significant principal components (PC's). The clusters are used as a categorical variable when predicting reservoir properties away from well control. The novelty in this approach is that PCA analysis is used to analyze covariance relationships between all vector elements (neighboring amplitude values) by using the statistical mass of the large number of vectors sampled in the seismic data set.

Our approach results in a powerful signal-analysis method that is statistical in nature. We believe it offers data-driven objectivity and a potential for property extraction not easily achieved in model-driven fourier-based time-series methods of analysis (digital signal processing).

We evaluate the effectiveness of our method by applying a cross-validation technique, alternately withholding each of the three wells drilled in the area and computing predicted effective porosity (PHIE) estimates at the withheld location by using the remaining two wells as hard data. This process is repeated three times, each time excluding only one of the wells as a blind control case. In each of the three blind control wells, our method predicts accurate estimates of sand/shale distribution in the well and effective porosity-thickness product values. The method properly predicts a low sand-to-shale ratio at the blind well location, even when the remaining two hard data wells contain only high sand-to-shale ratios.

Good predictive results from this study area make us optimistic that the method is valuable for general reservoir property prediction from 3D seismic data, especially in areas of rapid lateral variation of the reservoir. We feel that this method of predicting properties from the 3D seismic is preferable to traditional, solely variogram-based geostatistical estimation methods. Such methods have difficulty capturing the detailed lithology distribution when limited by the hard data control's sampling bias. This problem is especially acute in areas where rapid lateral geological variation is the rule. Our method effectively overcomes this limitation because it provides a deterministic soft template for reservoir-property distributions.
Laboratory Study Investigating Emulsion Formation in the Near-Wellbore Region of a High Water-Cut Oil Well
Authors: Janssen P. H. , van den Broek W. M. G. T. , Harris C. K.
Published: December 2007

An experimental study was conducted to determine the morphology of oil/water mixtures produced into a high water-cut well. This information is important for determining the feasibility of downhole oil/water separation.

Core-flow and microflow experiments were performed to simulate the two-phase flow process in the near-wellbore region of a high water-cut well. In the core-flow experiments the morphology of oil/water mixtures leaving different types of porous media was observed and the droplet-size distribution was determined for different fluid properties and flow parameters. In the microflow experiments the flow regimes and breakup mechanisms of the oil phase in the pore space were visualized and observed.

The experimental results show that the oil/water mixture emerging from the porous medium depends strongly on its wettability. When the porous medium is oil-wet, the produced oil is mainly in the form of large drops that are formed at the porous end face. From water-wet porous media, small oil droplets are produced at high flow rates; their sizes are typically of the pore size's order and are formed inside the porous medium. A correlation between the droplet size and relevant fluid, and flow and porous-medium parameters has been developed, allowing for the assessment of circumstances in which downhole separation can be problematic. The experimental results have also shown that in water-wet porous media a transition from capillary-dominated to dispersed flow takes place in the capillary number range investigated (10-5<Nc<10-3).
A Method for Extrapolation of Cut vs Recovery Curves
Authors: Ershaghi Iraj , Omorigie Osazuwa
Published: December 2007

JPT Forum articles are limited to 1,500 words including 250 words for each table and figure, or a maximum of two pages in JPT. A Forum article may present preliminary results or conclusions of an investigation that the present preliminary results or conclusions of an investigation that the author wishes to publish before completing a full study; it may impart general technical information that does not warrant publication as a full-length paper. All Forum articles are subject to approval by an editorial committee.

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Introduction

For a fully developed waterflood with no major operational changes planned, a plot of fractional water cut vs total recovery is used often to obtain a quick estimate of ultimate recovery at a given economic water cut. Extrapolation of past performance on the "cut-cum" plot is a complicated task. The difficulty arises mainly because curve fitting by simple polynomial approximation does not result in satisfactory answers in most cases.This paper presents an equation that is a fair representation of the waterflood process, based on the concepts of fractional flow and the Buckley-Leverett recovery formula,* which may be written as

(1)

ER = over-all reservoir recovery, volume of hydrocarbon recovered divided by oil in place, place,

fw= fractional water cut,

where m and n are constants.

Derivation of the Equation

The fractional flow equation (after neglecting the capillary pressure and gravity terms) may be written as

(2)

The main portion of the ko/kw curve vs Sw plotted on semilog paper is quite linear and may be expressed as

(3)

where a and b are constants. On substitution, Eq. 2 may be written as

(4)

where

As shown by Welge,* the water saturation at the producing end (S,.) may be expressed as producing end (S,.) may be expressed as(5)

where

Sav = average water saturation throughout thesystem.

Since

(6)

In these equation, Swi is the initial water saturation.

JPT

P. 203
The Fluid Travel Log
Authors: Walker Terry , Sherwood John , Sumner Cyril R. , Marshall Ray
Published: December 2007

By using down-hole ejection of radioactive fluid and two gamma counters the velocity of flow at a given point or the determination of whether or not fluid has passed a given point can be determined accurately on production or injection wells. In this method the counters are positioned at the proper points, a small concentrated quantity of radioactive fluid is ejected, and a recorder operating in time-drive records the time interval or fluid movement past the counters, each counter recording on a separate pen for a permanent record. Inside the casing or in open hole if a caliper log is available, a time profile and resulting velocity profile determines the full injection or production distribution. During injection profiling the procedures readily point out and locate any channeling which may exist. Equally simple job procedures are available for detecting casing leaks, tubing leaks, leaking packers and many other operational problems which are detectable by a study of fluid flow. Field examples are given to indicate the success and utility of the method. Of great importance to the operations engineer is the fact that job procedures with the well at normal operating conditions are standardized for ready field interpretation.

Introduction

With the increasing application of water flooding, pressure maintenance and other recovery-increasing techniques in the oil industry, an accurate means of determining input profiles is an absolute requirement. The injection fluid costs, especially in miscible floods and gas injection, are such that channeling behind the pipe must be located and remedied. Also, the efficiency of secondary recovery techniques requires orderly flood-front movement throughout the vertical extent of the zones. Therefore, the input profile must be as desired, and accurate profiling by some means is necessary on the injection wells after completion and at intervals during the flood. In some cases in waterflood projects, even input profiles are not the only requirement-the production profiles should also be such that orderly flood-front movement is obtained. Again, an accurate means of profiling is required at intervals during the project. There are a number of production problems where accurate production profiles can be of great aid in remedial work. Where wells are producing large amounts of water along with a small amount of oil from either long perforated intervals or open hole, shutting off the water section and allowing greater drawdown on the oil section can greatly increase oil production. In wells of this type, of course, are the condition where the highest permeability zones are watered out with oil remaining in the less permeable zones.

JPT

P. 851ˆ
Reliability of Deepwater Subsea Blowout Preventers
Authors: Holand Per
Published: December 2007

Operational experience data from deepwater subsea blowout preventers (BOP's) used in the U.S. Gulf of Mexico (GOM) in 1997 and 1998 have been collected and analyzed to reveal BOP reliability problems. Results focus on rig downtime caused by BOP failures, criticality of failures in terms of ability to control a well kick, and BOP subsea test-time consumption. Results have been compared with corresponding results from previous BOP reliability studies carried out for other areas and periods. An overall conclusion is that there are no main differences in overall reliability of deepwater BOP's vs. BOP's operating in "normal" water depths, except for increased downtime caused by increased BOP handling time in deep waters.