bluuebunny/crossref_metadata_2025_split huggingface dataset:
Twelve Years of Gas Injection in a Frio Sand
Authors: Millikin B.T. 
Published: December 2007

Introduction
The purpose of this paper is to contribute to the existing knowledge of the economic recovery of oil by methods other than normal depletion. A case history is presented of a gas injection project in one zone of the multiple producing zone Frio sands of south Texas. Approximately 75 per cent of the produced gas has been returned to the formation for 12 of the 13 years of producing life. The study is an example of the performance which has been experienced by return of a large portion of the produced gas to the gas cap of a thin non-homogeneous sand.

Geology
The producing zone is the Frio sand of lower Oligocene age. The oil and gas accumulation is a combination of a structural and stratigraphic trap. The structure consists of a large asymmetrical nose plunging gently to the northeast. The reservoir is limited on the west flank by an oil-water contact, on the north and south by the sand lens grading into shale, and on the east by a steep fold or fault parallel to the axis of the structure. The dip of the west flank or oil producing flank is approximately 130 ft per mile, or only 1.5 degrees.
There are 11 separate Frio producing zones in the field but this paper is limited to only one of the zones. The sand lenses are separated vertically by 25 to 75 ft of shale and were correlated across the field by means of markers picked from the electric logs. A portion of a typical cross section is shown on Fig. 1 and the section is located with reference to the area on Fig. 2. The D-5 reservoir is the large sand lens which appears in the D zone on the cross sections. It covers an area of approximately 2,100 acres. The structural map of the D zone (Fig. 2) was contoured on the subsea correlation points on the top of the D zone.
The reservoir rock is predominately firm, medium to fine-grained gray, argillaceous sandstone but lenses of soft, loosely consolidated sandstone occur throughout the producing zone. An x-ray diffraction indicates the clay content to be chiefly of the montmorillonite group and solubility tests indicate a low carbonate content. The porosity ranges from 8 to 28 per cent with a weighted average of 23 per cent. The majority of the horizontal permeability ranges from 100 to 500 md and averages 194 md. The vertical permeability is approximately one-half of the horizontal permeability.
An Evaluation of Scale Inhibitors
Authors: Vetter O.J. 
Published: December 2007

A rating of inhibitors in the order of their effectiveness is a relative matter and depends upon test conditions. The most important conditions are the degree of supersaturation and the temperature; the higher the supersaturation and the higher the temperature the less effective a scale inhibitor becomes.

Scale Inhibition Is Still an Art
Scale inhibition is still closer to being an art than a science. The literature deals only to a very small extent with the problems of scale inhibition. Most of the published data do not consider the basic facts of crystallization and inhibition. such as reaction mechanisms and kinetics. Because these fundamental considerations are often neglected, there are many recorded failures of scale treating procedures in oil and gas fields.
This neglect of fundamentals and lack of data is surprising because the formation of scale is a rather costly problem for some industries, above all the petroleum industry. We lose many millions of dollars petroleum industry. We lose many millions of dollars in revenue every year because scale creates flow restrictions in our fields.
Accurate evaluation of scale inhibitors is the first and most important step toward effective scale control.

How Are Scale Inhibitors Presently Tested? Presently Tested?

Test Machines
Several investigators have been concerned with the development of test machines designed to simulate the conditions of scale deposition in the field. The degree of scale buildup in these test devices is used to screen and rank commercial products and experimental chemicals.

Scale Coupons
The use of scale coupons in the field is a test somewhat related to the use of test machines in the laboratory. Steel coupons are inserted in flow lines, and the amount of scale they accumulate is used to evaluate an inhibitor that has been injected into the system upstream of the coupon.
Precipitation Test Precipitation Test In the "chelation test," which should be called the precipitation test, two chemically incompatible precipitation test, two chemically incompatible solutions are combined. The precipitation of scale-forming solids - for example, calcium carbonate (CaCO ), calcium sulfate (CaSO,) or barium sulfate (BaSO ) is measured in the presence of an inhibitor of varying concentrations by means of chemical analyses. The amounts of precipitate obtained are then compared with the amount of precipitate formed by mixing solutions containing no scale inhibitor. The more solids that are kept in solution by a given amount of inhibitor. or the less inhibitor that is needed to keep a given amount of solids in solution, the more effective and desirable the inhibitor is thought to be.
This test is widely used for laboratory evaluation of scale inhibitors. The test is very quick and convenient to run, gives fast results, does not require costly equipment, and can be run by relatively untrained personnel. Unfortunately, the reproducibility of the result is sometimes very poor, and data reported by different testers is often contradictory.
P. 997
On Fractures Produced by Low-Velocity Impact In Plexiglas Rods Simulating Drill Bits
Authors: Rinehart John S. , Prompsy Jean-Jacques 
Published: December 2007

Introduction
The purpose of the present study was to arrive at a better understanding of the stress fields developed within drill bits under dynamic loading and the influence that these stress fields could have on the failure of the drill bits. Particular emphasis has been given to the influence that bit shape has on the establishment of highly localized, potentially destructive stress inhomogeneities within the bit. This paper covers one phase of a broad study involving three velocity regimes: impacts at very low velocities, 0 to 20 ft/sec, a velocity range in which dynamic effects are just beginning to be found; impacts at velocities ranging from 20 to several hundred ft/sec, a range commonly encountered in practical drilling operations; and impulsive loading through the detonation of explosives, a velocity range in which the dynamic effects are greatly exaggerated and made more identifiable. Specifically, fracturing which develops at the end of a cylindrical bar undergoing a shock produced by impact was experimentally investigated, the impacted area being the face of a truncated cone terminating the cylindrical bar. Fracture characteristics were looked at as a function of impact velocity, area of impacted face and cone angleparameters of considerable importance in the design of drill bit.

EXPERIMENTS
The specimens were made of Plexiglas, which enabled the fracture pattern to be easily observed. In Plexiglas, the velocity of a longitudinal wave is about 8,700 ft/sec, and the velocity of the transverse wave about 4,200 ft/sec. The specimens were impacted by a steel cylinder whose lower face was parallel to the terminal face of the experimental bit, as shown in Fig. 1. The impacting mass was shifted up and down on two steel rods, dropping from a maximum height of 11 ft, with the velocity varied between 0 and 6.5 m/sec. The initial mass of the cylinder was 4.1 kg, which could be increased by steps up to 8.8 kg by addition of steel plates. The velocity of the steel cylinder was determined by using an electric circuit; as the cylinder dropped, it contacted two steel wires, the first one starting and the second one stopping an electronic counter. Two similar counters connected in parallel were used to corroborate each other. The velocity was checked at each drop as it had been observed to vary somewhat from drop to drop. The two contact wires were located just above the top of the specimen so as to give a value of the instantaneous velocity of the steel cylinder at impact. The distance between the wires was 40 0.5 mm and the discrepancy between the counters was never more than 0.1 m/sec. Thus the velocity was known to within 3.25 per cent. This precision was sufficient with respect to the precision of the machining of the specimens. A very small lack of parallelism between the face of a specimen and that of the impacting hammer resulted in an oblique impact which required a much lower velocity to break the specimen.
SPEJ
P. 203^
Inflow Performance Relationships for Damaged Wells Producing by Solution-Gas Drive
Authors: Standing M.B. 
Published: December 2007

The dimensionless inflow performance relationship (IPR) for solution-gas drive wells presented by Vogel* is very useful in well producibility calculations. Well rates at various pressure drawdowns can be predicted easily by use of either his chart or his equation (his Fig. 5 and Eq. 1). A second use of his relationship, to be illustrated later, is as a means of averaging results of several rate tests on a given well.
Vogel investigated effects of wellbore damage on the shape of IPR curves. He states that the effect of skin, or damage, is to cause a straightening of the IPR curve. The reference curve he presents, however, (his Fig. 5) essentially applies to wells without damage during their early life. My purpose here is to present a companion chart that can be used for calculations involving damaged wells. The chart is useful in predicting stimulation that might be accomplished, under predicting stimulation that might be accomplished, under given drawdowns, if the wellbore damage is changed from one value to some other value.
Consider the pressure-distance profile of the positively damaged well illustrated in Fig. 1. The flow positively damaged well illustrated in Fig. 1. The flow efficiency, FE, of the well-formation system is given by the relationship(1)
Graphically, this amounts to the distance (p - p' wf) divided by the distance (p - p wf). For a well draining a closed cylindrical volume, flow efficiency can also be expressed as
(2)
where s is the dimensionless skin factor. FE also expresses the ratio of the well's flow rate with damage to the flow rate without damage.
P. 1399
Estimated Effect of Vertical Fractures on Secondary Recovery
Authors: Crawford Paul B. , Collins R.E. 
Published: December 2007

Abstract
Potentiometric model studies have been made of vertically fractured reservoirs. All fractures originated at the well and extended into the reservoir for various distances. Studies were made to determine the areal sweep efficiencies for line-drive patterns. The areal sweep efficiency for the unfractured system studied was 70.6 per cent. It was found that if the vertical fracture was parallel with the direction of flood, the areal sweep efficiency may be considerably reduced, approaching zero in some instances. If the fracture was at right angles to the direction of flood, the areal sweep efficiency may be greater than that for the unfractured system. The sweep efficiency depends on the length and orientation of the fracture and direction of the flood. It is concluded that considerable effort should be made to determine the nature and direction of fractures before initiating a flooding program. Such information is required if the maximum sweep efficiency is to be obtained and channeling is to be reduced to a minimum.

Introduction
The recent development and application of fracturing techniques to petroleum reservoirs has served to focus considerable attention on the effect such fractures may have on secondary oil recoveries. The opinion has been expressed that fracturing may not alter appreciably the water flooding possibilities. Others have thought that channeling may occur and that the creation of fractures may serve to substantially reduce the possibilities of conducting a successful water flood in the reservoir.
The purpose of this study was to obtain quantitative estimates of the effect of vertical fractures on the areal sweep efficiencies of line-drive flooding patterns. In presenting this work on vertical fractures, it is not to be inferred that the present fracturing techniques result in producing a vertical fracture. The types of fracture which are created are not known with certainty in every case. Some are believed to be horizontal, others inclined along bedding planes, and some data indicate vertical fracturing. Each fracture will probably exert a different influence on the sweep efficiency of the secondary recovery program; consequently each fractured well should perhaps be considered as a separate problem, requiring a careful analysis.
Planning the Energy Years
Authors: Nedom H.A. 
Published: December 2007

Future worldwide petroleum opportunities are equal to or better than any known in the past. However, the rules of the game are changing, and the opportunities will be seized by those who can adjust rapidly.
In a world of mushrooming energy needs, this country and its petroleum industry are in crucial times. The international balance of supply and demand and our country's energy shortage call for critical decisions on a national level that will in turn guide the future actions of companies and individuals. This paper examines the guideposts of long-range planning 20 years ahead, and in doing so, injects large elements of judgment and conclusion. The complex future is viewed from a worldwide perspective and from that of the U. S., the petroleum industry, and an average oil company.

Worldwide
Energy consumption is rapidly growing. The present rate will double by 1985, but fortunately the petroleum needed through that period and for years beyond petroleum needed through that period and for years beyond is either on hand or reasonably certain of discovery. Studies of geologically favorable areas around the world and their high potential confirm this conclusion. Those areas of greatest promise are Africa and the Far East, both unexplored relative to their onshore and offshore potential. Discoveries in Nigeria and Indonesia provide samplings of the larger areas that await exploration. Next in future importance is the Middle East, which already holds two-thirds of the known world oil reserve, and where the hydrocarbon potential remains high. Large concessions have yet to potential remains high. Large concessions have yet to be explored by new and improved seismic methods.
North and South America will also contribute significantly. In summary, the world petroleum future is one of large and rising consumption with adequate supply.
The world's large petroleum reserve areas are widely separated from the points of maximum consumption and this dislocation will increase as newer reserves are found in more and more remote places. The North Sea discoveries are welcome exceptions to this worldwide trend. In the future, countries that are large consumers and that are net importers will become even more dependent upon those with excess supply, and will increasingly rely upon large-volume, low-cost, long-distance transportation to bring the petroleum to market. Countries with excess supply, petroleum to market. Countries with excess supply, which even now have a political weapon against energy-short nations such as the U. S. and most countries of Europe, will find that their bargaining positions will improve. However, their influence will positions will improve. However, their influence will be limited by the over-all ample supply, since each country with petroleum to sell will be competing in a worldwide buyer's market. Of great interest on the international scene will be the strategies used by energy-short nations to insure that their future supplies are in friendly hands and available when needed.
P. 13
Optimization of a Cyclic Steam Injection Process Using Penalty Functions
Authors: Gottfried Byron S. 
Published: December 2007

Abstract
A penalty-function technique is described that can be used to solve constrained nonlinear optimization problems. The method is based upon the strategy of transforming the original constrained optimization problem into an equivalent unconstrained problem, and then solving a sequence of unconstrained optimization problems. This strategy is particularly attractive because unconstrained optimization problems are generally much easier to solve than constrained problems.
The method is applied to a cyclic steam injection process that has been studied previously using process that has been studied previously using other techniques. Detailed solutions are presented and the characteristics of the method are discussed The method works, and it exhibits several favorable characteristics, such as applicability to a wide variety of nonlinear problems and freedom from convergence difficulties or computer storage limitations. Moreover, the method can be understood and implemented on a digital computer with ease.

Introduction
It is difficult for the analyst to recognize the methods that are best suited to a particular problem. Recent texts on optimization theory have not aided the situation because little is presented about which techniques are most applicable to different problems. Thus, the difficulties of identifying particular optimization techniques for various specialized applications remain largely unresolved.
This paper presents a penalty-function optimization algorithm is suited to a variety of nonlinear engineering optimization problems. The method is applied to a problem that has been previously optimization of a cyclic steam injection previously optimization of a cyclic steam injection process. This example has a serial structure and may, process. This example has a serial structure and may, therefore, appear to be an unlikely application for a penalty-function optimizer. There are, however, several significant advantages to the use of a penalty-function algorithm rather than dynamic penalty-function algorithm rather than dynamic programming or the maximum principle. programming or the maximum principle.
Scaled Fluid-Flow Models with Geometry Differing from that of Prototype
Authors: van Daalen F. , van Domselaar H.R. 
Published: December 2007

Abstract
Experiments on oil displacement from homogeneous porous media have shown that the component porous media have shown that the component oil flow across the layer is often negligibly small compared with that parallel to it. This result is applied in the inspectional analysis of the equations governing the macroscopic displacement processes. It is shown that in rectangular homogeneous models the dimensionless groups l/h and a can usually be neglected. This finding has been proved experimentally in rectangular models of various dimensions, two extremes of which are described in this paper.
The work has been extended to curved models. An additional requirement is that the angles of dip must be small. Comparative experiments have been carried out in three-dimensional models of various geometrical configurations. The results of both studies indicate a greater flexibility in the use of models than has previously been assumed.

Introduction
The production behavior of petroleum reservoirs can to a large extent be investigated with the help of scaled models, although the great number of parameters to be scaled in such processes precludes parameters to be scaled in such processes precludes complete simulation. However, not all parameters have an equally important influence on the process; and it is therefore necessary to select the most important ones and investigate which parameters can possibly be neglected.
To date, oil reservoirs have almost always been represented by models of similar geometry. In other words, the characteristic length, width and height are scaled down by the same factor. For many reservoirs, however, the length-height ratio is extremely large, and laboratory models become inconveniently long or very thin. In such cases it would be desirable to make the model too thick relatively. It will be demonstrated that this is in a number of cases a justifiable solution.
A Systematic Approach to Well Surveying Calculations
Authors: Taylor Howard L. , Mason Mack C. 
Published: December 2007

Abstract
The information used in well surveying calculations is studied and formalized. A general, natural, mathematical approach to the problem is presented and four special cases are developed: presented and four special cases are developed: (1) triangular or trapezoidal, (2) secant, (3) quadratic, and (4) minimum curvature.
These methods are compared and their properties analyzed for reasonableness. Two of these methods are new and have appeared promising when applied to real and test data.

Introduction
Several new approaches have been proposed to the problem of performing well surveying calculations; and it has been pointed out that improvements in directional drilling tools and techniques justify a better treatment than the old tangential methods. However, a systematic analysis of the problem in a standard mathematical form has not been published. This paper will try to cover several of the more useful methods in a natural mathematical framework and to suggest several alternative approaches and directions for improvement.

Formulation of the Problem
In performing a directional survey of a well, a tool measures an inclination angle with respect to the vertical and a bearing angle with respect to North at a number of points, Pi, in the well. Thus, we know three things: (1) the location of the first point, Po, at the surface, (2) the distance between any two points, Pi - and Pi+1, along the arc length, and (3) the direction of the wellbore at each point, Pi (as given by the inclination and bearing).
Pi (as given by the inclination and bearing).If one considers using a smooth approximation to the wellbore rather than straight-line segments joined at angles, the question of what degree of smoothness is to be used arises. For example, cubic spline approximations could be used to insure second-order smoothness. There are two difficulties that arise. In the first place, the authors know of no reason why a wellbore should have second-order smoothness. Second, the calculations become very difficult, partly because more than two points must be dealt with at a time. In this paper we shall follow the common practice of only analyzing the wellbore from one point, say P0, to the next point, P1, and assume that the process is repeated until P1, and assume that the process is repeated until the final point, Pn, is located.
Referring to Fig. 1, we assume that the Z-axis is vertical and the X-axis is in the direction North. Thus the Y-axis will point East. The angle of inclination will be 0 and the angle from North, which is essentially the bearing, will be, where and . Hence, we can state our problem mathematically as follows.