bluuebunny/crossref_metadata_2025 huggingface dataset:
Polymer Gelants for High Temperature Water Shutoff Applications
Authors: Bryant Steven L. , Bartosek Martin , Lockhart Thomas P. , Giacca Diego
Published: December 2007

Polymer gelants are a well established means for shutting off water in lower temperature formations, but extending their application to hot reservoirs (>80°C) presents a number of technical challenges, particularly in matrix reservoirs. Achieving reliable high temperature performance requires programmable gelation delay, good injectivity, good propagation of gelant components and durability of the permeability reduction. The performance of a gelant against these criteria is dictated by a relatively small set of chemical and physical phenomena. A discussion of these phenomena provides a rational background for assessing the advantages and disadvantages of currently available gelants. This also helps to identify the best avenues for improving polymer gelant systems. This approach is particularly relevant when seeking gelants for high temperature matrix applications, because increased temperature renders it much more difficult to satisfy the four performance features simultaneously.
A Multiply-Fractured Horizontal Well in a Rectangular Drainage Region
Authors: Chen Chih-Cheng , Raghavan Rajagopal
Published: December 2007

We examine the productivity of a multiply-fractured well in a reservoir that is in the form of a rectangle. The properties of the individual fractures (length, conductivity, skin, etc.) are entirely arbitrary. The fractures are assumed to be parallel to one of the sides of the rectangle and maybe either parallel or perpendicular to the horizontal well. The primary objective of this work is to outline a computationally-efficient scheme to compute well productivity. This objective yields a simple method to incorporate this completion scheme in reservoir-simulation models. It should permit an engineer to understand interactions between the fractures in the presence of boundaries. The model also permits us to compute pressure distributions under depletion conditions for single-phase oil and gas reservoirs. Further, it provides for a realistic design of this completion scheme.

It is to be emphasized that the problem we consider is a nontrivial one in that flow to a single vertical fracture of finite conductivity in a rectangular drainage area is yet to be modeled successfully.
Conditions for Determining Areal Permeability Distribution by Calculation
Authors: Nelson R. William
Published: December 2007

NELSON, R. WILLIAM, GENERAL ELECTRIC CO., RICHLAND, WASH.

Introduction

Methods for determining permeability presented by W. D. Krugers in a paper entitled "Determining Areal Permeability Distribution by Calculation" have considerable merit. They can be expected to contribute significantly to analysis of flow in heterogeneous systems. Some rather subtle yet important conditions must be met, however, to assure that the computed permeabilities are correct. The conditions which insure a unique permeability distribution may have been overlooked in the method as proposed and presented in the subject paper. The subtlety of the special requirements may permit good agreement between computed and measured pressures in the reservoir; but the computed permeability may still be in error. The general theory and discussion to the requirements for a unique determination of the permeability distribution are presented elsewhere in more detail. Accordingly, only major features will be presented here in the notation of Kruger.

GENERAL DESCRIPTION OF REQUIREMENTS

A brief mention of the route to be followed in showing the special requirements may be helpful. The equation to be solved is a quasilinear, first-order, partial differential equation in the unknown permeability. This equation can be solved through an extension of Lagrange's method by reduction to a system of subsidiary ordinary differential equations. Through consideration of the identity of one of the Lagrange subsidiary differential equations with the stream function, a special interrelationship can be shown. The interrelationship has special significance with respect to the boundary condition. If the boundary function satisfies part of the subsidiary differential equation, no unique solution for the permeability distribution exists. In the physical problem this requirement for uniqueness indicates that the permeability measurements used as a boundary condition can not be along a stream tube. The boundary condition must be along a line, or series of lines, which completely traverse the region and pass through every stream tube.

DERIVATION OF SPECIAL REQUIREMENTS ON THE BOUNDARY CONDITION

If the velocity components in the directions of increasing x and y are vx and vy, the equation for the streamlines is

dx/vx = dy/vy ..............................(1)

Eq. 1 of Kruger's paper can be expanded to give:

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

khEq. 2, when is the dependent variable, is a quasilinear first-order partial differential equation. The analytical method of solution is described in several texts with Goursat's treatment as translated by Hedrick and Dunkel, being very readable and complete. Eq. 2 is reducible to the system of subsidiary differential equations.

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

Through assuming the form of the solution to be

......(4)

where F is an arbitrary function of two independent integrals of the system of Eq. 3.

SPEJ

P. 223^
Adsorption of Carboxylic Acids on Reservoir Minerals From Organic and Aqueous Phase
Authors: Madsen Lene , Lind Ida
Published: December 2007

Adsorption of organic acids onto North Sea chalk and pure minerals from a hydrocarbon phase and an aqueous phase show that the maximum adsorption is larger for calcite than for silicate surfaces in the hydrocarbon phase. The opposite is observed, however, in the aqueous phase. This suggests that the available silicate surfaces and oil/water ratio may play a role in the wettability of chalk.
Extended-Reach Composite-Materials Drillpipe
Authors: Hareland Geir , Lyons W. C. , Baldwin D. D. , Briggs G. M. , Bratli R. K.
Published: December 2007

This paper presents a new composite drillpipe design that allows for an increase in the drilling reach of high-angle, directional wells. Horizontal reach is greatly limited by resisting friction forces that are created by the interaction between the drillstring and the lower side of the borehole. As the drillstring is advanced further into a highly directional borehole, the resisting friction forces give rise to ever-increasing applied-torque and axial (push)-force requirements. The gravitational forces (i.e., drillstring weight) dominate the buoyancy forces in nearly all modern drillstring designs that are currently used in highly directional drilling operations. These dominating gravitational forces create reaction forces between the drillpipe and the borehole wall. The reaction forces, when multiplied by the coefficient of friction between the drillstring and the borehole, yield tangential surface forces on the drillstring (normal to, and parallel with, the pipe axis). These forces resist the applied torque that rotates the drillstring and the applied axial (push) force that advances the drillstring. The new composite drillpipe design discussed in this paper reduces the specific weight of the drillpipe so that it will have nearly neutral buoyancy in 15.4-lbm/gal drilling muds. With this reduction in drillpipe specific weight, a drillstring with this new design will have greatly reduced gravitational forces and, in turn, greatly reduced resisting friction forces. This design feature allows the applied torque and axial force to be more effective, thus allowing greater extended-reach capabilities. It is estimated that the current extended horizontal-reach approximate limit of 10 km could be increased to 15 km or more with the application of this new composite drillpipe design. Such an increase in reach would have an important impact on the development of oil and gas fields that are economically dependent on advanced directional drilling technologies. This new composite drillpipe technology has been extensively bench and field tested and has been successfully used in short-radius drilling operations. The design features of the proposed light-weight composite drillpipe are discussed and compared to current horizontal drilling operational requirements (using a steel drillpipe). The new light-weight designs can be used with either steel or titanium tool joints (with a filament-wound composite-tube body structure between the tool joints). The drillpipe may be fabricated in either 30- or 42-ft lengths. Engineering feasibility studies have shown that this new light-weight composite drillpipe will be economical to fabricate and should provide significant economic advantages in the development of oil and gas fields requiring extensive directional drilling operations.
Harnessing Information Technology To Facilitate Change
Authors: Chevallier Jean
Published: December 2007

This paper provides a business perspective of how harnessing information technology (IT) can facilitate change, especially in the oil and gas industry. The oil and gas industry has benefited significantly by leveraging developments in IT for applications that reduce the cost of oil exploration; reduce the time required to perform complex tasks; and link people and information, thereby enabling virtual teams. Typical examples of virtual teamwork are three-dimensional (3D) seismic surveys and million-gridblock reservoir simulations. To implement information-age solutions with global access and anytime availability, one must be aware of security, remote connectivity, and information management issues. Overcoming these issues can be an opportunity for oil and gas industry IT solutions organizations. Future developments in software, Intranet, powerful clients, massively parallel processing (MPP), and asynchronous transfer mode (ATM) will further enhance IT's capability to facilitate change in the oil and gas industry. IT already has played a significant role in the revival of this industry and will continue to do so into the 21st-century.
Methods for Determining Residual Oil with Pulsed Neutron Capture Logs
Authors: Richardson J.E. , Wyman R.E. , Jorden J.R. , Mitchell F.R.
Published: December 2007

The special techniques described here appear to be promising for determining precise quantitative residual oil saturations - under certain reservoir conditions. A field test of one method was encouraging. The PNC logs showed saturations that agreed with other measurements, and the degree of uncertainty in the estimates approached theoretical expectations.

Purpose and Scope

The basic physical principles of pulsed neutron capture (PNC) logging and descriptions of logging instrumentation and operation have been documented in earlier publications.3,4 In addition, several methods of PNC data interpretation for petroleum engineering applications have appeared in the literature.6 These latter reports demonstrate that PNC logging has become a valuable technique for formation evaluation. The most significant use of PNC logging has been to discriminate among gas-bearing, oil-bearing, and salt-water-bearing formations in cased holes. For example, gas-oil, gas-water, and oil-water contacts have been found and followed. Unsuspected hydrocarbon migration between zones also has been detected. In addition, water saturations have been calculated from PNC log data when porosity, rock type, formation hydrocarbon type, and formation water salinity were known or could be estimated.

Interpretations of PNC log data are often precise enough for decisions regarding recompletion or for a qualitative assessment of reservoir mechanism and performance. But how useful are these data when we must decide whether or not to conduct a tertiary recovery project in the flooded-out portion of a reservoir? In comparison with waterflooding, tertiary recovery is more complicated; thus its performance is harder to predict. Also, the process costs are higher, so there is much less margin for error. Therefore, many of the parameters must be measured with great accuracy for designing a tertiary recovery project.

One of the most important parameters is the residual oil saturation - the target for profit. A decision to undertake a tertiary recovery project could depend entirely on the estimate of residual oil saturation and the margin of error associated with the estimate. Minimum expected errors in oil saturation and saturation distribution (among other parameters) are essential for a tertiary recovery project.

The purpose of this paper is to describe in some detail the possibility of using PNC data to estimate more precisely the residual oil saturation remaining at the end of a waterflood (either natural or induced).
Use of Higher Moments for the Description of Upscaled, Process Independent Relative Permeabilities
Authors: Durlofsky Louis J.
Published: December 2007

Traditional approaches for the scale up of highly detailed reservoir descriptions to the coarser scales more appropriate for reservoir simulation often rely on the use of pseudo relative permeabilities. Two of the major limitations in the use of pseudo relative permeabilities are the process dependency inherent in the resulting curves and the need for a different set of curves in each coarse scale grid block. In this paper, these limitations are illustrated and quantified through numerical simulations of viscous dominated displacements in fine scale, heterogeneous, two dimensional systems. It is concluded that the functional form of traditional pseudo relative permeability descriptions is too limited to capture a wide variety of flow behavior and that an ‘extended description,’ in which the upscaled relative permeabilities depend on variables in addition to the phase saturations, is required. The additional variables we propose are higher moments of the fine scale variables, specifically the variance of saturation, the variance of pressure and the velocity-saturation covariance. It is then shown that these new variables are capable of accurately correlating upscaled relative permeabilities for a variety of displacements in a process independent manner; i.e., the extended description can account for varying inlet conditions and permeability realizations. The practical use of this methodology in an actual reservoir simulation will, however, require the derivation and solution of coarse scale evolution equations for the moments.
Field Tests Indicate New Perforating Devices Improve Efficiency in Casing Completion Operations
Authors: Wade R.T. , Pohoriles E.M. , Bell W.T.
Published: December 2007

New completion concepts by the petroleum industry have resulted in renewed activity in the design of perforating equipment. This paper coversthe development and use of explosive devices for the "single-point entry" technique used in formation preparation,field results achieved with the reactive-liner shaped-charge ("Crack-Jet") perforators anda discussion of the magnetic positioning of perforating guns.

Through application of magnetic positioning devices, uniform high-performance perforations may be made in large casings with small, through-tubing guns. Field results have indicated an appreciable advantage in the placement of a circular notch or several perforations in the plane of desired fracture initiation. The use of radial-firing, multi jet devices for the "single-point entry" technique is discussed. Reactive-liner shaped charges, initially field-tested in West Texas, have been used in all types of formations, both consolidated and unconsolidated. Field results are presented, and various formation test targets perforated with the reactive-liner charge are shown. Performance in several problem areas indicates improved rates of injection and more-favorable production rates.

Introduction

Rapid changes in completion practices during the past few years have required the development of new perforating tools. The need for small, through-tubing perforators to penetrate large casings has led to the technique of magnetic positioning. The advantages of the "single-point entry" technique for formation fracturing have been realized by the development of radial-firing explosive devices for use on electrical cables. A major breakthrough in shaped-charge design has been achieved with the new reactive liner which develops high lateral pressures within the perforation, resulting in cleaner holes and, in tight formations, intensive fracturing. These recent developments provide increased efficiency and permit successful revision of older completion techniques.

Magnetic Positioning

Through-tubing completions, which continue to gain in popularity, pose additional problems in gun design. Besides improved safety and convenience, they make possible a differential pressure into the wellbore at the time of shooting which results in cleaner perforations. The trend in recent years has been toward even smaller-size tubings to permit multiple completions. Gun design problems, already severe in the small diameters, thus have increased. Excessive ranges of clearance that are encountered create a major problem in the design of through-tubing perforators. Clearance is defined as the distance from the perforator to the casing along the axis of the jet. Fig. 1 illustrates the clearance problem resulting from the use of a 1–11/16-in. gun below 2-in. tubing. In 7-in. casing the individual shot clearances could vary from 0 to 4 1/2-in. Obviously, the performance on the large-clearance shots would be drastically reduced; both penetration and entrance hole sizes are severely affected.

JPT

P. 1069^
Interactive Reservoir Simulation With the World Wide Web
Authors: Chawathé Adwait , Ouenes Ahmed , Schofield Samuel , William Weiss
Published: December 2007

Technology transfer through the World Wide Web (WWW) allows efficient use of available computing resources. A centralized highspeed computer can be accessed through the Internet by many users (independents) who otherwise may be handicapped by lack of such resources. The Petroleum Technology Transfer Council (PTTC) has a regional lead office in New Mexico dedicated to this objective. As an example of sharing resources, we have coupled an automatic history-matching algorithm to an analytical polymer/waterflood simulator that may be accessed over the Internet.

The polymer/waterflood predictive model (PFPM) was developed for the U.S. Dept. of Energy (DOE) and is available to the public as a freeware from the Internet site http://www.bpo.gov. The simulator has been tested by various users over a period of time and is considered to be reliable. We attached a user-friendly, Web-based graphical user interface (GUI) to the PFPM model and put it on a fast, dedicated Internet server. This paper describes the development and implementation of this new Internet-based, interactive simulation tool.
Studies of the Mechanism of Paraffin Deposition and Its Control
Authors: Shock D.A. , Sudbury J.D. , Crockett J.J.
Published: December 2007

A review of the background literature on the paraffin deposition problem has shown:it is a major production operational problem,the problem apparently occurs in all crude oil types and areas of production, andinsufficient information is available to clearly delineate its occurrence.

A number of experiments have been performed which show that there are numerous types of paraffin deposition. Several evaluation schemes have been devised, one of the most useful is the determination of viscosity at various temperatures. The viscosity temperature curves of several types of crude oils are discussed with reference to the deposition problem. Solvent evaluation procedures have been proven useful in determining the response of a given paraffin to a proposed solvent treatment.

Introduction

When considering that wax or paraffin problems have been recognized as a major problem from the inception of oil production, it is slightly less than amazing that the literature contains only a handful of references in which the problem is surveyed. The latest thorough examination of the problem by Reistle is now 20 years old. Brown reported on the API survey in 1940, Wright on Southeastern Ohio problems, and Sayre on problems in the Bradford, Pa., field in 1951. These papers have discussed the various developments on the problem from an operational standpoint. There is no evidence in the literature that additional work is being done to define the conditions under which paraffin problems occur and examine critically the various means of alleviation.

During the past two years, the authors have gradually accumulated background on these aspects of the paraffin problem. Thc technology has advanced sufficiently that a new appraisal of the problem by the industry would yield profitable results. This paper is presented not so much as a completed investigation, but as a stimulus to encourage others to re-examine the problem. This presentation will cover our appraisal of the problem and several techniques we have found useful.
Pore-Level Mechanisms for Altering Multiphase Permeability with Gels
Authors: Thompson Karsten E. , Fogler H. Scott
Published: December 2007

The pore-level mechanisms by which a crosslinked gel changes a porous medium's physical morphology and multiphase permeability are examined using relative permeabilities, pulse tracers, and micromodel visualization. Coreflood experiments indicate that to retain oil permeability while reducing water-permeability, the maintenance of oil-phase pathways after a gel treatment is crucial. However, because the gel changes the medium's morphology, the original pathways for oil are disrupted if the posttreatment fractional flow of water is nonzero. This redistribution of phases generally causes a loss of oil-phase permeability that cannot be regained under normal flow conditions.

Relative permeabilities during drainage are not affected significantly by the gel, but during secondary imbibition, the hysteresis in relative permeability is much more pronounced. Tracer experiments indicate the reason for this behavior is that the gel reduces the connectivity of the medium and the fluids distribute themselves more inefficiently, causing a large fraction of dead-end or isolated nonwetting-phase fluid to exist. These conclusions are particularly important for water-control applications where water saturation increases with time. The mechanism suggests that even if a gel exhibits preferential permeability reduction, the loss of absolute permeability and the shift in saturation can be highly damaging to the oil-phase permeability of a treated zone.
Mechanistic Foam Flow Simulation in Heterogeneous and Multidimensional Porous Media
Authors: Kovscek Anthony R. , Patzek Tadeusz W. , Radke Clayton J.
Published: December 2007

Gases typically display large flow mobilities in porous media relative to oil or water, thereby impairing their effectiveness as displacing fluids. Foamed gas, though, is a promising agent for achieving mobility control in porous media. Because reservoir-scale simulation is a vital component of the engineering and economic evaluation of any enhanced oil recovery (EOR) or aquifer remediation project, efficient application of foam as a displacement fluid requires a predictive numerical model. Unfortunately, no such model is currently available for foam injection in the field where flow is multidimensional and the porous medium is heterogeneous.

We have incorporated a conservation equation for the number density of foam bubbles into a fully implicit, three-dimensional, compositional, and thermal reservoir simulator and created a fully functional, mechanistic foam simulator. Because foam mobility is a strong function of bubble texture, the bubble population balance is necessary to make accurate predictions of foam-flow behavior. Foam generation and destruction are included through rate expressions that depend on saturations and surfactant concentration. Gas relative permeability and effective viscosity are modified according to the texture of foam bubbles. In this paper, we explore foam flow in radial, layered, and heterogeneous porous media. Simulations in radial geometries indicate that foam can be formed deep within rock formations, but that the rate of propagation is slow. Foam proves effective in controlling gas mobility in layered porous media. Significant flow diversion and sweep improvement by foam are predicted, regardless of whether the layers are communicating or isolated.
Theoretical and Practical Aspects of Free Piston Operation
Authors: Lebeaux J.M. , Sudduth L.F.
Published: December 2007

Theory of operation of the free piston as well as practical limits of the device in prolonged flowing life of wells producing from volumetric type reservoirs are discussed. Reservoir behavior and the gas expansion work formulae are used to exhibit utility of free piston in prolonging natural flowing life. Examples are exhibited to show actual performance of the tool in West Texas. Investment and operating costs of the free piston are compared with those required for other artificial lift methods. A nomograph which may be used in determining adaptability of the tool is exhibited. Use of the free piston in intermittent gas lift operations is briefly mentioned.

Introduction

The basic idea of interposing in the tubing of a producing well of a solid interface, between gas and liquid phases of the produced fluid, to increase the efficiency of the lift is not new. In the original plunger lift the interface used was a solid critical diameter piston. The increase of efficiency of lift was obtained by better utilization of the energy of the compressed gas, either of the formation gas or of compressed gas supplied to the well from an outside source. Reduction to a minimum of the channeling of gas through the liquid phase and the filling back of the oil and water to be produced resulted in better utilization of the energy. This type of installation required a perfectly cylindrical and uniform diameter tubing to permit the travel of the tool.

Several years ago a free piston was developed which incorporated an expanding rubber element for sealing against the tubing wall and was therefore applicable in any conventional tubing string. Fig. 1 shows the piston.

The piston is manufactured in two types: Type 1, which is designed for installations using an outside source of gas; and Type 2, which is designed for those installations which use the well's own energy as a driving mechanism. This paper will consider only the latter type of free piston which has had considerable success in operations in West Texas, with the performance of the Type 1 only very briefly mentioned later in the text.
A Rotational High Pressure Viscosimeter
Authors: Hawkins Murray F. , Kimmel Marion L.
Published: December 2007

Introduction

Sage appears to have been the first (1933) to design a rolling ball viscosimeter for the express purpose of measuring the viscosity of oils with natural gas in solution, i.e., under reservoir conditions. In 1940 Hocott and Buckley further refined the rolling ball instrument in both design and method of operation, and their instrument, known as the Humble type, was the forerunner of present day viscosimeters used in petroleum production and research laboratories. They also initiated the technique of charging the viscosimeter with a sample directly from a bottom hole sampler.

In 1948 the committee on engineering research of the Petroleum Division of the AIME in Part 3 (1) of the Physical-Chemical Topics of Table 1 suggested the "development of improved and simpler methods of measuring viscosity of reservoir fluids." This note will describe a rotational, high pressure viscosimeter which has been developed in response to this suggestion but whose relative merits are yet to be determined fully.

The Instrument

Fig. 1 is a photograph and Fig. 2 is a cross sectional drawing of the instrument. It consists of a non-magnetic, stainless steel rotor about 4 in. in length and 1 in. in diameter centered axially within a non-magnetic, stainless steel, pressure vessel of cylindrical bore. The rotor is mounted on miniature, precision ball bearings and has a radial clearance of about 1/64 in. Alnico magnets are inserted perpendicular to the axis of rotation on either end of the rotor, those at the top to serve as indicator magnets, those at the bottom, as the driven magnets which turn the rotor. A constant (but variable) speed motor outside the pressure vessel turns the rotor by means of a driving magnet attached to the motor shaft. The motor speed is checked using an aircraft type, precision, spring-wound interval timer and an electric impulse counter to record revolutions by means of an electric contactor on the motor shaft.
Platforms in the Southern North Sea
Authors: Campbell Patrick J.D.
Published: December 2007

Introduction

While so much attention is being centered on developments and expectations in the Northern North Sea it is useful to look back at what has been done to date in the South. Such is the tempo in this industry that we rarely realize it was only 6 years ago that we were first faced with placing platforms off the east of England. We then described the environment there with all the superlatives now used for the Western Approaches. However, with familiarization and careful planning, operations in the gas fields are now routine. We should therefore review our experiences in the South and see whether what we have learned there can be used to help us in the North. In this review the platforms considered are those installed by Shell U. K. Exploration and Production Ltd. (Shell Expro) as operators of concessions owned jointly by Shell U. K, Ltd. and Esso Petroleum Co. Ltd.

Leman Gas Field Platforms

In 1967 Shell Expro installed its first platform in the North Sea in the Leman gas field about 30 miles off the cost of Norfolk. This was a drilling platform with decks measuring 150 x 114 ft. It stands on two similar jackets that provide, in all, 16 piles in a 4 x 4 configuration. In 1968 this Complex A development was extended with a production platform having decks 140 ft long and 70 ft wide. The platform is a 12-piled structure, the piles being in a 4 x 3 configuration. The reason for going to a two-platform plan was that it was necessary to install a platform as soon as possible to start development drilling, and install a complex that could safely produce gas to shore without disrupting that drilling. A further important advantage gained by this approach was that more reservoir data could be obtained before the design of the production facilities was completed. The second complex - Complex B - was started in 1969 when Platform BD (B - Drilling) was completed. Before detailed designing on this platform was started, several possible configurations were studied in order to arrive at the most economical platform design to suit the packaged rig that had already been contracted for. As a result, a 12-pile (4 x 3) single-jacket platform was selected with decks 150 ft long and 114 ft wide. A similar optimization study on the production platform resulted in an eight-pile (4 x 2) production platform resulted in an eight-pile (4 x 2) jacket designed to support production decks 150 ft long and 55 ft wide. For the third complex - Complex C - a twin-platform design was again chosen, A third drilling contractor had been selected, so the drilling platform was redesigned to accommodate a different rig configuration. This platform has one jacket of 12 piles, but in two rows of six each.

JPT

P. 1046
Oil Spill Contingency Planning in the North Sea
Authors: Daniels J.T.
Published: December 2007

The North Sea is one of the world's important commercial fishing areas; yet the introduction in the early 1970's of oil-producing operations into the North Sea has not been hampered by particularly restrictive legislation or critical public opinion. If anything, the public and their governments have welcomed the oil public and their governments have welcomed the oil industry to their respective countries. The happy situation that prevails in the North Sea area has not been achieved without a great deal of effort by the oil companies and the governments; the way in which this effort was organized and directed forms the basis of this article.

Work of the North Sea Offshore Operating Committee

While the first plans for offshore oil production were still being drawn up, and the majority of oil fields in the North Sea were in the discovery phase, the industry, through the various North Sea country offshore operating committees, was setting up committees to study the problems associated with oil production in the marine environment. The first work of these committees was to accept the fact - one that is still not accepted universally - that oil spills were possible from the offshore oil fields and to study feasible methods of cleaning up an oil spill. This was done by first reviewing the published data and house reports of the classic oil spills such as that from the Torrey Canyon and the spill in the Santa Barbara Channel. From analysis of these spills it became evident that any plan or method would have to cover a wide range of individual company management structures or be extremely restrictive on any specific company's management. Accordingly, the groups restricted their studies to equipment and methods of cleaning up oil spills and gave only general advice on how individual company plans could be drafted to suit the available jointly owned equipment. All the conventional methods of cleanup were evaluated and it was decided that the only one that could be relied upon to be effective was dispersing the oil with chemical dispersants. (The North Sea groups are striving to develop methods that will pick up oil in the hostile North Sea, and are giving advice to operators and governments regarding improved operating practices that will minimize spillage.) Generally speaking, no mechanical equipment available today can collect or retain oil in seas that exceed 10-ft wave height. Therefore, the present plans of nearly all the North Sea Offshore Operating Committees are based on using oil-dispersing chemicals. The chemicals to be used were selected after consultation with, and on the recommendation of, the national government laboratories who were undertaking large-scale tests of dispersants. On successfully obtaining suitable supplies of approved dispersant, the next step was to decide on methods of application.

P. 1153
Analysis of Naturally Fractured Reservoirs From Sonic and Resistivity Logs
Authors: Aguilera Roberto
Published: December 2007

This study was an effort to find a reliable means of detecting and analyzing fractured systems from logs. It appears from the cases considered that the porosity exponent m is an adequate criterion to detect such a system and that the parameter P, a function of formation resistivity and sonic velocity, provides a reliable means of distinguishing the hydrocarbon-bearing zones.

Introduction

Detection and evaluation of naturally fractured reservoirs is becoming more important every day. This investigation was undertaken to try to find a reliable means of detecting and evaluating fractured systems from sonic and resistivity logs. A theoretical model developed for detection purposes indicates that for such systems the porosity exponent m (commonly referred to as cementation factor) should be relatively small, ranging between 1.1 and 1.3. This criterion has been successfully used in recognizing natural fractures in different wells of the Altamont trend. (It must be pointed out that the method is limited to gross sections where a statistically significant number of zones is available, some of which are 100 percent water saturated and fractured.) For evaluation purposes a previously defined parameter, P, has been used. This parameter is a parameter, P, has been used. This parameter is a function of formation resistivity and sonic velocity. By determining the mean value of P at a water saturation of 100 percent, it is possible to evaluate the resistivity index, I, for hydrocarbon zones, and hence values of water saturation. This technique has also been used in wells of the Altamont trend. For illustration, analyses of a commercial well and of a noncommercial well are presented.

Theory

The idealized model considered in this study is presented in Fig. 1. It is similar to the one presented by Warren and Root to analyze pressure behavior in fractured reservoirs and to the one presented by Towle to study the relationship between formation resistivity factor and porosity. In this model it was assumed that the spacing between parallelpipeds represented the fractures. This assumption does not appear to be unreasonable. Since porosity is defined as the ratio of the void space in a porosity is defined as the ratio of the void space in a rock to the bulk volume of that rock, porosity could be expressed for the case of this model as(1)= 1 - X 3

where

= porosity, fraction, X = length of the block, fraction.

The resistance of each block is given by the equation(2)r = RL/A,

where

R = resistivity L = length of current path A = cross-sectional area of the current path.

As defined by Archiel the formation factor is given by(3)F = Ro/Rw,

JPT

P. 1233
A Simple Method for Determining Well Pressure in Closed Rectangular Reservoirs
Authors: Cobb William M. , Dentist Walter L.
Published: December 2007

In 1968, Earlougher et al., introduced a "buildingblock" concept, using a constart-rate well producing from the center of a closed square, to generate solutions for pressure behavior in several rectangular systems. Tables of the dimensionless pressure drop function for the square system are presented in Ref. 1, along with illustrations of the technique. Their procedure, while a step toward reducing laborious procedure, while a step toward reducing laborious computations, can sometimes be quite tedious. This note describes a further simplification for obtaining dimensionless pressures for these other rectangular systems at the producing well; other points within these systems are not considered. Conveniently, Earlougher et al. have tabulated the Matthews-Brons-Hazebroek pressure correction function, PDMBH, for 16 closed rectangular systems. These correction functions provide the basis from which the dimensionless wellbore pressure drop functions can easily be obtained. In a recent comprehensive review of pressure buildup analysis, it was shown thatwhereSolving Eq. 1 for pD yieldsIt is clear from Eq. 5 that pD is a function of pDMBH, tDA, and A/rw2. Thus, given pDMBH and A/rw2 for a particular system, pD as a function of tDA can be particular system, pD as a function of tDA can be calculated directly. Columns 2 and 3 of Table 1 present the pD and pDMBH data of Ref. 1 for the case of a well in the pDMBH data of Ref. 1 for the case of a well in the center of a square with it value for A/rw of 2,000. The pD data tabulated in Column 4 are obtained by direct substitution of tDA and pDMBH of Columns 1 and 3, respectively, into Eq. 5. As can be seen, the solutions in Columns 2 and 4 are identical. For dimensionless times less than those given in Table 1, pD can be obtained from pD can be obtained fromFor times greater than those given in Table 1, pD can be obtained bywhere CA is the reservoir shape factor, and is be Euler constant - approximately 1.7811.

P. 1305
Effect of Gas Slip on Unsteady Flow of Gas Through Porous Media - Experimental Verification
Authors: Wallick G.C. , Aronofsky J.S.
Published: December 2007

This paper presents an experimental verification of numerical solutions of the differential equation describing the transient flow of an ideal gas through a porous material including gas slip effects. Several experiments previously proposed by one of the authors are described together with the correlation of the experimental results with the numerical solutions. Excellent agreement is shown between experiment and theory, thus demonstrating the validity of both the basic assumption made in the derivation of the differential equation and of the numerical solutions of the differential equation.

Introduction

In a recent paper, one of the authors has discussed a numerical solution of the differential equation describing the unsteady flow of an ideal gas through a porous material. This paper was primarily concerned with the effect of gas slip on the flow behavior. In steady state measurements, Klinkenberg and others have observed that the apparent gas permeability of a porous material may be expressed as a linear function of the reciprocal average pressure of the form,

(Equation 1)

where the intercept is a constant for a given porous material and the slope is a constant for a given porous material-gas combination.

A number of numerical solutions of the resultant differential equation were presented and specific flow experiments were proposed as a means of testing the numerical solutions. The purpose of the present paper is to describe the results of several of these experiments and the correlation of the experimental data with the results of the numerical analysis. Reference should be made to the previous paper for details of the mathematical and numerical analysis.
Flash Calculations as Performed on the IBM Card Programmed Calculator
Authors: Organick Elliott I. , Meyer Henry I.
Published: December 2007

One of the fundamental and perhaps most tedious of all calculations in petroleum engineering has been the so-called "flash calculation." High speed computing machines have been playing an increasingly important role in the oil industry, and it is natural that one of our first job assignments for these machines would be to relieve the engineer by performing flash calculations for him.

One of the machines currently available which is particularly suitable for this work is the International Business Machines Corp. Card Programmed Calculator, or CPC. Two CPC procedures developed for flash calculations are reported. In each case the machine is made to print a composite, compact, and accurate record of the entire calculation (see Figs. 1 and 2).

The first procedure, or program, is applicable primarily for separator calculations. This program may be used conveniently and efficiently in calculating optimum separator pressures and temperatures in single and in series staging of well effluent feed streams of up to 11 components. Machine time is four minutes per stage. The second program is designed primarily for reservoir flash calculations at elevated pressures or for process calculations at very low temperatures where the equilibrium constants vary significantly with the composition of the feed stream. This latter method will handle mixtures containing up to in 20 components in seven minutes of machine time.

Introduction

During the past three years there has been generated an enormous interest among engineers and scientists regarding the application of high speed digital computers to the solution of problems of research and industry. Computer manufacturers have managed to keep pace with this interest by developing machines capable of handling economically the most prodigious of calculations conceived by would-be customers. In general. however, these machines, announced by more than 15 manufacturers, are not yet generally available and will not be for at least another year.
Combustion-Drive Tests
Authors: Showalter W.E.
Published: December 2007

SHOWALTER, W.E., UNION OIL CO. OF CALIFORNIA, BREA, CALIF.

This paper discusses some of the results of combustion-drive tests which were made in a test cell using a sand bed 10 in. in diameter × 10-ft long. The test method is illustrated and described.The relationship between the API gravity of the in situ oil and the amount of air required for combustion drive is discussed n detail. Other things constant, the air requirement for combustion drive increases as the API gravity of the in situ oil decreases. If the test results apply to actual reservoirs, the lowest-priced oils may cost the most to recover by this method.Information is shown which indicates that the effect of pressure on the amount of hydrocarbon burned is not large. A method of predicting air requirements from the API gravity of the in situ oil is presented.

Introduction

Combustion drive is the term used to identify the process of interstitial or in situ burning as an oil recovery method. Part of the in situ oil is burned to generate the energy needed to produce the remainder of the oil. Combustion drive as an oil recovery mechanism remains an economic uncertainty in spite of all the work that has been done by the industry in both laboratory and field. This paper will show some of the results of tests which were made in a test cell for the purpose of studying the nature of the combustion-drive process. It will present data which indicate that the API gravity of the in situ oil is a significant indicator of the amount of air required to drive a burning front through oil sand. Air requirement varies inversely as the API gravity of the in situ oil.

EXPERIMENTAL

The tests were performed in a cell which utilized a cylindrical sand section 10 in. in diameter × 10-ft long. The thin-walled metal pipe which held the sand was wound with twenty external electrical resistance heaters which, by means of an automatic controller, maintained adjacent sections of the wall of the pipe at temperatures equal to the temperatures of the contained sand. Each heater covered 6 linear in. of the pipe. By this means lateral heat loss from the sand section was minimized, thereby causing the sand section to simulate more closely a horizontal increment of a combustion-drive reservoir.Fig. 1 shows a schematic diagram of the test assembly.Thermocouplestomeasurethetemperature in the sand were located every 6 in. along the length of the sand section. The pipe containing the sand was enclosed in a cell designed for an operating pressure of 500 psig. The inlet air pressure was controlled at the inlet, and the gas flow rate was controlled and measured at the outlet of the cell.The oil sand used for the tests was prepared by mixing first water and then oil with the non-consolidated sand using a closed mixer similar to a cement mixer. Table 1 shows a screen analysis of the sand. Ninety percent of the sand was 100 mesh or finer. This sand was a mixture of 80 per cent No. 120 Nevada White Sand and 20 per cent Tennessee Hi-Fusion Moulding Sand No. 3. The Nevada sand was a clean silica sand.

SPEJ

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