bluuebunny/crossref_metadata_2025 huggingface dataset:
The Petroleum Engineer's Function in Oil and Gas Financing
Authors: Dodson Charles R.
Published: December 2007

Introduction

Although petroleum engineering as a profession is relatively new timewise, it has matured rapidly and become a recognized and essential element in the financing of oil and gas operations. Most oil operators have become accustomed to working with the bank petroleum engineer and know that certain requirements must be met to obtain loans. It is worth noting that petroleum engineers have found bank work to be interesting, varied and rewarding. For the alert, competent and ambitious, there are ample opportunities for advancement and promotion to officer status.

The main objectives in this discussion are to comment on financing oil and gas operations by banks and to discuss in some detail the importance, content and usefulness of the engineering report in establishing the value of a property as collateral and in forecasting production for repayment of a loan. It may seem contradictory to the popular idea of conservative bank practice that a bank would accept as collateral for loans oil and gas still in the reservoir rock-commodities that are fluid, mobile, cannot be inspected or insured and must be produced from wells and sold in order to make payments on the loans. However, experience with loans based on properly engineered reserves has been most satisfactory and many oil-minded banks claim they have never had a bad oil loan.

Oil loans are not new to banks; they were started in the early thirties, increased noticeably after 1935 and especially since 1945. In the meantime, banks have made hundreds of oil loans and found them not only safe and profitable, but helpful in developing the growth of important relationships in regard to deposits and use of other bank services. The acceptability of the oil loan to commercial banks is due primarily tolegislation that regulates oil production to prevent waste,recognition of correlative rights,increased engineering ability to estimate with reasonable accuracy reserves and forecasts of production andadvanced production technology.

These factors have tended to stabilize prices and substantially improve reliance on reserve estimates and forecasts of revenue.
Results of Well Stimulation by Hydraulic Fracturing and High Rate Oil Backflush
Authors: Ghauri W.K.
Published: December 2007

Well stimulation by hydraulic fracturing and by associated techniques has been carried out in fields along the Whittier fault trend in the Los Angeles basin since 1953, with a total of 53 jobs performed to date. The hydraulic fracturing methods of hydrafrac and sandoil frac have been tried extensively along with the stimulation technique of the "high rate oil back flush", which consists simply of injecting large volumes of formation crude at high rates into the producing zone. Although several of the treatments individually have yielded no additional oil, well stimulation by these methods on an over-all basis has been highly successful and should find applicability to other California oil fields producing from similar low-permeability, shaly measures.

Introduction

The well stimulation treatments discussed in this paper were performed from 1953 to the present in the Brea-Olinda and Esperanza fields, which lie along the Whittier fault trend in the Los Angeles basin (Fig. 1). Since production stimulation by hydraulic fracturing is at present relatively unproved in California, the following geological and reservoir information regarding the producing measures where these treatments were performed is presented to aid in future applications to other California fields. The Brea-Olinda field, where most of the treatments discussed herein (80 per cent) were performed, extends for about six miles laterally along the Whittier fault trend and comprises a practically continuous, elongated belt of accumulation, about 1/2 to one-mile wide. Since the turn of the century, the field has undergone sporadic development as a result of the discoveries of deeper pools and the lateral extensions of existing pools. Cumulative production from the field is 260 million bbl of oil, with some 650 active wells currently producing 17,500 B/D. The Esperanza field, where the remainder of the treatments were performed, was discovered only recently (1956) and has yielded 250,000 bbl of oil, with seven active wells currently producing 400 B/D.
Surface Tension of Reservoir Crude-Oil/Gas Systems Recognizing the Asphalt in the Heavy Fraction
Authors: Firoozabadi Abbas , Katz Donald L. , Soroosh Hossein , Sajjadian Vali A.
Published: December 2007

Improvements in predicting surface tensions for crude-oil/gas systems at reservoir conditions has been attributed to new parachors for distillation cuts of crude oil and the recognition that the last fraction or residue of distillation has a parachor not continuous with the distillation cuts.

For such reservoir gas/oil systems as condensates, which normally do not contain asphalt materials, the new parachors for the crude cuts would suffice for the surface-tension computation. For a reservoir fluid containing asphaltic substances, the calculation procedure should include a single measurement of the surface tension.
Field Consolidation of Fractured Core
Authors: Conley F.R. , Glover J.A. , Knutson C.F.
Published: December 2007

A recent investigation of fractured core from the Embar reservoir of the Gebo field, Hot Springs County, Wyo., utilized novel techniques that are believed to be worth reporting. The most successful procedure was to:

- cut the interval with a rubber sleeve core barrel;

- cut the core, encased in the rubber sleeve, into approximately 3-ft sections for ease of handling;

- plug the ends of the sleeve and displace the drilling mud, oil and water from around the core with a polyester resin;

- allow the resin to polymerize; and

- slab the core, which is cast in resin, and investigate the amount and type of fracturing exposed.

Discussion

An in-fill well to be drilled in the Gebo field, Hot Springs County, Wyo., provided an opportunity to do some additional coring in the fractured Embar formation. Since the recovery from this formation had been poor, the Gebo Unit No. 47 was scheduled to core the Embar using a rubber sleeve core barrel. The upper productive member of the Embar formation was cored in two 20-ft sections at an average rate of 15 min/ft, with a core recovery of 95 per cent. When the 20-ft sections of core encased in the rubber sleeve were removed from the core barrel, it was obvious from the limber nature of these sections and a number of narrow necks (or points of reduced diameter of the sleeve) that the core was broken into a number of pieces. In order to study the anticipated fracture system at leisure in the lab, alternate 3-ft sections of the core were cast into plastic briquets at the rig site. Several different plastic application techniques were tested, and the most successful method is described in this note. About 2 in. of core were removed from the end of each 3-ft section to be plastic treated. Rubber stoppers (with flared copper tubing running through them) were clamped in place, and the section was placed in a holder. This holder kept the rubber sleeve from expanding to more than 3 1/2 in. OD and kept fractures from being wedged open and increasing the length of the core. (See Fig. 1.) The section of core in the holder was then mounted vertically, and plastic was pumped into the bottom of the sleeve. (See Fig. 2.) Enough plastic was pumped into the bottom of the section of core to displace most of the oil, mud and water out the top of the core. After about 250 ml of clean plastic had been produced from the overflow at the top of the holder, the upper copper line was sealed off by bending and crimping; enough additional plastic was pumped into the bottom tubing to expand the sleeve against the holder.
Considerations for Optimum Fracture Geometry Design
Authors: Elbel J. L.
Published: December 2007

This paper gives production forecasts for (1) various equal-proppant-volume fracture geometries with various formation permeabilities, (2) equal fracture lengths with different proppant volumes, and (3) equal fracture lengths and proppant volumes with various proppant distributions. It shows conditions when Prats' relationship for maximum productivity is true and when higher values of dimensionless fracture conductivity are beneficial. These should give the design engineer useful tools when optimizing fracture design.
New Correlations for Calculation of Vertical Coverage and Areal Sweep Efficiency
Authors: Fassihi M. R.
Published: December 2007

This paper presents two new correlations for calculating vertical coverage and areal sweep efficiency. Use of these correlations can facilitate the waterflood performance calculations.
Early Production: One Stage Further
Authors: Van Bilderbeek B. H.
Published: December 2007

This paper discusses the design procedures followed during the development of a new mudline suspension system for use on jackup rigs in drilling or tieback applications. This has resulted in the design of an integrated system that combines mudline support hangers with the surface wellhead into a package that materially changes the method of operation on jackup rigs. The new system uses mandrel-type surface hangers that can be installed through the blowout preventer (BOP).
Analytical Chemistry of Portland Cement and Its Oilfield Admixtures
Authors: Simpson Benny E.
Published: December 2007

The successful cementing of boreholes in earthen formations requires careful control of the properties of cementing slurries and of the final set product. Accurate, dependable, time-efficient chemical analyses are prerequisites in determining quality of cement, additives, field blends, slurries, and set cement. A review highlighting chemical, spectrochemical, microscopic, and thermal methods of analysis of portland cement and oilfield cementing systems is presented.
Behavior of Wells Completed in Multiple Producing Zones
Authors: Raghavan Rajagopal
Published: December 2007

This paper summarizes recent advances in our understanding of layered reservoirs. Procedures to combine pressure and rate data to determine the flow capacity, skin factor, and average pressure of a given layer are documented. Concerns pertaining to stimulation are addressed.
Four-Phase Flash Equilibrium Calculations Using the Peng-Robinson Equation of State and a Mixing Rule for Asymmetric Systems
Authors: Enick Robert M. , Holder Gerald D. , Mohamed Rahoma
Published: December 2007

A technique for predicting one- to four-phase flash equilibrium is presented for multicomponent systems containing water, such as CO2/crude-oil/H2O mixtures that characterize the CO2 miscible flooding of petroleum reservoirs. The Peng-Robinson equation of state (PR-EOS) is used to describe the aqueous and hydrocarbon phases, and an accelerated and stabilized successive-substitution method is used to obtain convergence, even in the near-critical region.

In order to describe accurately multiphase equilibria involving water, a recently developed mixing rule for asymmetric systems is incorporated that permits the solubilities of both CO2 in H2O and H2O in CO2 to be modeled. The equation of state (EOS) is also modified to enable the aqueous-phase density to be predicted accurately. A comparison of predicted and experimental three- and four-phase behaviors is made for a CO2/Maljamar crude-oil/H2O mixture at 302.5°C [576.5°F].
Computer Determination of Calibration and Environmental Corrections for a Natural Spectral Gamma Ray Logging System
Authors: Koizumi Carl J.
Published: December 2007

Pulse-height spectra recorded by a passive spectral gamma-ray logging system were simulated by radiation-transport calculations for several combinations of gamma ray sources and tool environments. Derived from the calculated log responses were (1) source- and energy-dependent environmental corrections and (2) calibration factors and an environmental correction method for three-window potassium/uranium/thorium analysis.
Experimental and Theoretical Study of the Electromagnetic Propagation Tool in Layered and Homogeneous Media
Authors: Safinya K. A. , Clark B. , Habashy T. M. , Randall C. , Perez-Falcon A.
Published: December 2007

We report a detailed experimental and theoretical study of the electromagnetic propagation tool (EPT™) in homogeneous and layered media. In this study, we measured the tool response in a number of homogeneous media, the standoff response in three formations, and the field maps for the magnetic field components parallel to the tool pad. We compared the experimental results to four theoretical models of different complexities. The best agreement is obtained with the model that takes into account the dominant geometric effects of EPT structure and the effect of the mutual coupling between the different slots. This study of EPT response is limited to relatively fresh fluids.
Predicting Reservoir-Condition PV Compressibility From Hydrostatic-Stress Laboratory Data
Authors: Andersen Mark A.
Published: December 2007

Laboratory PV reduction data can be converted into reservoir-condition formation compressibility through a nonlinear elastic model. Data demonstrate the validity of the theory for consolidated sandstone. The algorithm described requires a nonlinear fitting routine available in many computer subroutine libraries to obtain the prediction parameters.
Flow Distribution in a Roller Jet Bit Determined From Hot-Wire Anemometry Measurements
Authors: Gavignet A. A. , Bradbury L. J. , Quetier F. P.
Published: December 2007

In current practice, the optimization of drilling hydraulics consists of the selection of nozzle sizes that maximize either jet impact or hydraulic power at the nozzle. But what is required for a real optimization is the knowledge of the hydraulic forces available for cleaning at the rock face, not at the nozzle. This paper shows the results of hot-wire anemometry experiments that provide insight into the flow distribution in a jet bit. Direct measurements of the flow field, including turbulence levels, are reported and discussed.
How to Live with Proration of Water Floods In Lansing-Kansas City Fields, Kansas
Authors: Funk E.E.
Published: December 2007

While the impact of relatively large amounts of waterflood oil production has caused some waterflood proration, reduction of input rates or restriction of stimulated production endangers ultimate oil recovery. Water flood proration may safely be applied to new projects using a preset project allowable. Operators may thereby develop in stages so that stimulated wells produce at capacities within the project allowable.

Project allowables are best suited to large projects. A State unitization law is needed to encourage formation of most of the possible large projects. Stage development cooperatively within a preset allowable is possible, but the existing haphazard projects in the Lansing-Kansas City fields need capacity allowables. Haphazard injection is inefficient and must be discouraged.

Prorated water floods must use not less than a minimum efficient input rate. High recovery efficiency dictates low pumping fluid levels and the avoidance of wellbore restrictions. Suddenly applied waterflood proration will reduce ultimate oil recovery, but selective application by wells will reduce the loss. Selection requires good data on each well's current performance and general condition.

Introduction

Water flooding has, from the process's inception some 40 years ago, continually grown. Until recent years, the many remarkable production increases obtained by water flooding were universally acclaimed by the industry. Likewise, it was unthinkable to restrict waterflood production rates because the process in itself is a sound act of conservation. The economic facts of life in the domestic oil production field now so favor water flooding that it was inevitable to hear some operators, having few properties under flood, clamor for proration of water floods.

Kansas, as well as several other states, has seen its Corporation Commission recognize the clamor for proration of water floods. For the most part the Kansas Commission used stop-gap measures at first. Recent actions show a fairly consistent policy that operators may expect some proration of water floods. Operators must admit that both pressure maintenance and secondary recovery activities can be handled in such a manner that no damage will result from fairly applied and properly administered proration.
In-Situ Gel Calculations in Complex Reservoir Systems Using a New Chemical Flood Simulator
Authors: Scott T. , Roberts L. J. , Sharpe S. R. , Clifford P. J. , Sorbie K. S.
Published: December 2007

This paper presents results for a series of calculations on the deep emplacement of a polymer gel in a stratified reservoir model. These calculations were performed with a new chemical flooding simulator that has the facility to describe generalized chemical reactions between components. This code is described, and preliminary calculations on an in-situ gel treatment in a large model reservoir are presented. We find that to obtain significant amounts of incremental oil while avoiding very large pressure buildup, the polymer gel system must have the correct combination of long gelation times and good permeability-reducing properties in the high-permeability streak (residual resistance factor FR~ 10 to 40 in the cases studied here). No commercial polymer/ crosslinker systems are currently available that have the very long gel times required to obtain deep emplacement in a large reservoir system.
Recognition of Waterflood Sweep and Formation Lithology in a Giant Egyptian Oil Field by Applied Petrophysics
Authors: LaChance D. P. , Winston R. T.
Published: December 2007

This paper presents a simplified formation-evaluation methodology that was successfully applied to the study of a giant Egyptian oil field. This method could resolve formation lithology and injected water saturations with a high degree of confidence. Observed core lithologies were matched with openhole log responses to generate lithology windows in a lithoporosity plot. Resolution of formation lithology by openhole logs required plotting the log responses on the lithoporosity plot and determining the lithology window in which the data fell. Formation intervals swept by injection water were found by analysis of two calculated water saturations (formation water and injection water) together with lithology and field-history information. This work relied heavily on the first successful full-zone core obtained in the field, which was cored and handled with fiberglass core barrels.

This paper includes field case histories and techniques that may be useful. The methods are simple, can be related to actual data instead of theoretical or calculated data, and provide results that fit reasonable expectations. Finally, the lithology determination method is easy to computerize.
Field Evaluation of Catalytic Deoxygenation Process for Oxygen Scavenging in Oilfield Waters
Authors: Cantu L. A. , Harrison L. D.
Published: December 2007

An extended field test at the Grubb Lease, San Miguelito field, Ventura, CA, has shown that the catalytic deoxygenation (Cadeox™) process is an effective new oxygen-scavenging method for oilfield injection waters. The process can reduce oxygen concentration from the saturation level in seawater (about 8 ppm) to substantially below the corrosive level (≤_0.01 ppm) with less than 60 seconds of contact time. The process is effective at temperatures as low as 5°C [41 °F] and at a water pH range of 4 to 10.

The Cadeox process uses a simple hydrogen and oxygen reaction to remove corrosive oxygen from injection waters. Palladium-impregnated anion-exchange resin beads in a packed column are used as reaction sites for H2 and O2 to form water.
New Degasser/Desurger Design Solves Gas Separation Problems
Authors: Hertz Darryl W.
Published: December 2007

A new degasser/desurger design has demonstrated superior gas separation characteristics compared with a conventionally designed flume separator in oilfield production, battery service. These new degasser units have been in continuous sour service for 3 years in the Salt Creek field. They have efficiently removed gas from surging liquid volumes of up to 170,000 BFPD [27 030 m3/d fluid] and cost much less than conventionally designed two-phase separators.
Investigation of Unexpectedly Low Field-Observed Fluid Mobilities During Some CO2 Tertiary Floods
Authors: Patel P. D. , Christman P. G. , Gardner J. W.
Published: December 2007

Phase behavior, inorganic precipitation, and wettability are investigated as possible reasons for the unexpectedly low field-observed mobilities during some CO2 floods, in particular, the Denver Unit, Wasson field CO2 pilot. The observed mobility was not a near-wellbore effect and probably played a major role in reservoir sweep: the low effective permeability offset the detrimentally low CO2 viscosity. Experimental and simulation studies, supplemented by literature data, lead to the conclusion that rock wettability could be the root cause of these low fluid mobilities. Phase behavior effects, though they may play a role, are not necessary to explain the injectivity behavior, and inorganic precipitates probably have little effect under the conditions investigated here. Thus, current simulator modeling of low fluid mobilities, which are based on arbitrary permeability reduction factors allegedly caused by phase behavior, appears unjustifiable even though overall simulator results may be acceptable.
System Grounding of Electric Submersible Pumps
Authors: Solomon J. H.
Published: December 2007

To ground or not to ground? That is the question. This paper assists in answering that question. Proper system grounding of electrical submersible pumps has long been an issue for debate. Some believe that an ungrounded system is best, whereas others are equally convinced that the opposite is true. Many are not aware of how important the correct answer may be.
The Effect of Circulating Media and Nozzle Design on Rock Bit Performance
Authors: Payne L.L.
Published: December 2007

In an attempt to discover the effect of various circulating media and nozzledesigns on rock bit performance, a series of laboratory and field tests havebeen conducted. Although it is possible to conduct experiments in thelaboratory, actual conditions existing in the bored hole cannot be duplicated.Consequently, most laboratory results require confirmation from fieldapplication. However, notwithstanding the limitations, interesting andinformative results obtained from laboratory tests may aid in planning futureinvestigations.

Circulation of Air or Gas

Laboratory experiments conducted over several years proved that this type ofmedium was superior to a drilling fluid insofar as rock bit performance isconsidered. A special bit, mounted on a drill press and used for testingformation cores received from various fields, consistently indicated higherdrillability than actually obtained in practice. In the laboratory, air wasused to cool the cutters and to remove cuttings. Drilling was conducted underatmospheric pressure and this no doubt had a partial effect upon the morefavorable drilling rate obtained in the laboratory.

Extensive field tests were conducted in the fall of 1949 to determine therelative merits of circulating air compared to water while drilling a softlimestone encountered in a Michigan limestone quarry. The initial test ofcirculating air confirmed previous laboratory indications. On-bottom drillingtime per foot of hole was reduced 50 per cent compared to previous resultsobtained while circulating water. Bearing life materially increased whilecirculating air and the footage per bit was doubled over the results obtainedwith water. The on-bottom drilling cost per foot of hole was reduced byhalf.

A second field test was conducted in a Michigan dolomite quarry. On-bottomdrilling time per foot of hole was reduced by 20 per cent and the amount ofhole drilled per bit was doubled. A substantial reduction in total drillingcost per foot of hole resulted. The holes drilled vary in depth from 50'Ft to120'Ft. At these depths pressure on the formation differed only slightly whiledrilling with water or air. The results proved rather conclusively that whendrilling in the absence of sub-surface water flow a rock bit will performbetter with air used in the circulating system.

During 1950 a major operator became interested in circulating air onseismograph, rigs. Considerable difficulty had been encountered in Canadaduring the winter months because of the extreme cold freezing the circulatingfluid. Furthermore, in many areas a ready source of water is not available andmust be trucked to the rigs.
Gamma-Ray-Absorption Techniques Improve Analysis of Core Displacement Tests
Authors: Nicholls C. I. , Heaviside J.
Published: December 2007

A gamma-ray-absorption apparatus for monitoring fluid saturations in core displacements is described along with the design principles, their implementation, and an accurate calibration procedure. The apparatus is capable of measuring fluid saturations to ~ 1% in 10 seconds for a 4-mm [0.16-in.] slice of a 38-mm [1.5-in.] -diameter core.

The apparatus has been useci to study a variety of displacement processes, including miscible and immiscible. Examples of its application combined with distributed pressure measurements are demonstrated for relative permeability experiments.
An Extraordinary Drilling Challenge in the Rocky Mountain Overthrust Belt
Authors: Swanson J. D. , Brandt I. M. , Johnston R. D.
Published: December 2007

The rugged northwest Wyoming overthrust presented a significant drilling challenge. The evaluation of the Madison formation below 16,500 ft [5029 m] in the Broad Canyon No. 1 exploratory well was the culmination of 6 years of drilling activity in the area. Two previous wells, drilled from essentially the same location, failed to reach the Mississippian objective and were abandoned after numerous drilling problems. Drilling through the Madison objective was completed on the third well, Broad Canyon No. 1, after 500 days of continuous operations. The setting and cementing of deep, large-diameter casing strings and the eventual drilling of a liner through a plastic flowing eyaporite zone highlighted the successful drilling program.
Adsorption and Chlorination of Mutual Solvents Used in Acidizing
Authors: King G. E. , Lee R. M.
Published: December 2007

Loss of mutual solvents during acidizing can be severe, depending on the type of product. Results showed that some mutual solvents can penetrate deeply into a test formation. Chlorination of mutual solvents by HCl was also considered and was found to be minimal when the treatments were designed properly.
A Simplified Method for Determining Gas-Well Deliverability
Authors: Chase Robert W. , Anthony Ted M.
Published: December 2007

This paper presents a simplified method for predicting the performance of a gas well. A method for determining the deliverability of an unfractured gas well by use of a single-point flow test and a dimensionless Vogel-type inflow performance curve was proposed by Mishra and Caudle. Their procedure necessitates the calculation of real-gas pseudopressures for shut-in and flowing bottomhole pressures (BHP) obtained from pressure-buildup and stabilized-flow tests, respectively. This paper offers a simplification of this technique in which a range of pressure values is defined over which pressure-squared terms can be substituted for pseudopressures. A comparison is made between results obtained from analysis of well-test data on several gas wells made with conventional multipoint test methods, with the Mishra-Caudle technique, and with the simplified method presented in this paper. The simplified method offers the engineer who might not have access to a pseudopressure computer program or pseudopressure tables a method for estimating gas-well deliverabilities. The method of Mishra and Caudle and the simplified method were both observed to yield slightly conservative estimates of gas-well deliverabilities compared with the deliverabilities calculated from multipoint flow-test analyses. The simplified technique was found to be useful for predicting the performance of fractured gas wells as well as unfractured wells.
Effect of Stimulation on the Performance of Devonian Shale Gas Wells
Authors: Zuber M. D. , Lee W. J. , Gatens J. M.
Published: December 2007

This paper presents the results of a study of the effect of various stimulation methods on Devonian shale reservoirs and compares the economics of the stimulation alternatives. Formation permeability anisotropy and induced fracture wing length are the key factors that determine the optimal stimulation technique. Induced fracture conductivity and orientation’ are also important.
A Philosophy for Exploration
Authors: Pyle Howard C.
Published: December 2007

Factors Influencing Exploration

Oil finding is not a precise science; therefore, it must be guided along philosophic lines. Oil is where you find it, and potential oil areas can be classified as either fairway or long-shot, with all shades of gradation between the two.

True fairway areas, themselves, have many gradations and classifications. In South Texas along the Frio-Vicksburg trend, for example, oil is found from 4,000 to 6,000 ft in wells which cost a bare $50,000. The majority of land there is held in small tracts, and it is not uncommon for a wildcat well to be drilled on a 320-acre lease. The ratio of discovery to dry hole is good, but it is exceedingly difficult to find large oil accumulations. Nothing is more discouraging than to have made a discovery or two and then find that only 1 million bbl have been added to reserves. Admittedly 1 million bbl of oil is a real asset, but for the company that produces that amount in a week or a month it does not help much to maintain reserves.

The Miocene belt of Coastal Louisiana is another typical fairway area. Ratios of discoveries to dry holes are favorable there also, and leases on relatively large tracts of land are sometimes available. Producing sands are sometimes thick, and discovery often leads to developing important large oil and gas reserves. On the other hand, most of the area is inaccessible and the pay sands are deep. Wells usually cost more than $250,000 to drill and, in some areas, can consistently cost twice that much. Large reserves can be discovered so that costs per barrel for finding oil are competitive. In such an area, the larger companies can hope to build reserves.

Other factors influence the choice of an area for exploration. Competition is always present, and the type of this competition is an important consideration. Areas such as South Texas are ideally suited for the small operator, to whom drilling of a $50,000 well is a big event in the year. The small operator will find ready financial assistance from the "high tax rate boys", and he probably will spread his risk by having only a piece of several wildcats. Something about being in the 75 to 90 per cent tax bracket causes people to want to participate in any old play-particularly in the last quarter of the tax year. As a result of this urge and the willing cooperation of small wild-catters, lease costs, royalty rates and brokers overrides all increase-and the sizes of lease blocks decrease. A pattern becomes established for the area.
Some Theoretical Aspects of Underground Combustion in Segregated Oil Reservoirs
Authors: Gottfried Byron S.
Published: December 2007

This paper is concerned with possible transport mechanisms which occur during segregated burning (i.e., burning in an oil reservoir in which the oilbearing formation is overlain by a "clean" porous zone containing only gas). Two analytical models are presented. In the first, burning is assumed to occur at the gas-oil interface, and the dominant mechanism is taken to be the rate at which oxygen diffuses to the interface. The second model assumes that combustion occurs within the clean zone, with the dominant mechanism being the mechanism of fuel deposition from the oil-bearing formation to the clean zone. Comparison of the results of the analyses with limited experimental data indicates that the latter mechanism is much more plausible. Both models are idealized representations of the actual process and are somewhat conjectural, however, owing to t he lack of more definitive laboratory or field data.

INTRODUCTION

In recent years there has been considerable theoretical and experimental research directed toward understanding the recovery of crude oil by underground combustion. Although two different recovery schemes have been proposed, known as forward and reverse combustion, it is only forward combustion that shows promise of becoming a practical recovery technique.17

Most of the analyses of the forward combustion process have considered it to be piston like; i.e., oil is displaced by a vertical combustion zone which, with its ensuing gases, pushes the oil forward as the flame front is propagated through the reservoir.1-8,11,12,14-16 However, information gained in field pilot studies indicates that, at least to a certain extent, forward combustion proceeds in a segregated manner in oil reservoirs.1 An ideal segregated system is one in which the oil-bearing formation is overlain by a "clean" porous zone containing only gas. The location of the combustion zone in such a system is not immediately evident, although combustion is believed to occur either at the gas-oil interface or within the clean zone. In either case, the combustion zone may be horizontal and it moves in parallel rather than in series with the produced oil.

The purpose of this paper is to explore the likely mechanisms by which segregated burning can occur, and to determine the sensitivity of the resulting models to changes in various physical parameters. Two governing mechanisms are considered: the case of a horizontal combustion zone at the gas-oil interface with the rate of combustion governed by the rate at which oxygen diffuses to the interface, and the case of combustion within the clean zone with the combustion process controlled by the transport of fuel from the oilbearing formation to the clean zone. Both models are somewhat hypothetical and involve considerable simplification of the actual process. However, the results allow some preliminary understanding of segregated burning which is useful in the absence of more definitive laboratory or field pilot data.
Hydraulic Fracturing with the Single-Point Entry Technique
Authors: Huitt J.L.
Published: December 2007

Introduction

Hydraulic fracturing is now in its second decade as one of the most useful techniques developed for well stimulation. As fracturing became an established practice in the oil industry, the necessary experience was gained from which advancements in fracturing technology could be made. Today, some wells are treated with fluid volumes exceeding 100,000 gal and at rates approaching 100 bbl/min Fracturing fluids are compounded for the particular formation to be fractured. Treatments are now designed with a certain degree of accuracy for a given formation area to be exposed to the fracture. These and other advances in fracturing technology have been well-received by the industry and used to advantage. Even with these improvements, however, conventional fracturing has failed to effectively stimulate wells completed in some formations. A number of the failures can be attributed to inadequate capacity of the fractures.

Formation Capacity-Fracture Capacity

Formation capacity may be defined as the product of the permeability (horizontal) of the formation times the thickness of the productive zone. Likewise, the fracture capacity is the product of the permeability of the fracture times its width. For best results in well stimulation, the fracture capacity should be at least 10 times the formation capacity.

Conventional fracturing usually results in fractures having capacities of a few hundred to a few thousand millidarcy-feet. Fractures with capacities in this range are usually adequate for stimulation in zones of low permeability and/or small thickness. For example, a zone of 40 ft in thickness with a permeability of 5 md has a capacity of 200 md-ft, and a well completed in this zone should be stimulated effectively with a fracture of 2,000 md-ft capacity. This capacity fracture can often be obtained by conventional fracturing, provided the fracture is propped effectively.
Properties of Capillary Fluids at the Microscopic Level
Authors: Christenson Hugo K. , Israelachvili Jacob N. , Pashley Richard M.
Published: December 2007

Results are presented of experimental measurements of the properties of model reservoir fluids (water and hydrocarbons) at the microscopic and submicroscopic level—i.e., when they are confined in narrow spaces comparable to the pore sizes of reservoir rocks. Measurements of capillary forces (or pressures) were carried out for curved oil/water interfaces (menisci) of radii as small as 20 A [2 nm]. The results show that the capillary pressure is accurately given by the Laplace equation for even the smallest pore radii of interest in waterflooding. The Kelvin equation describing the equilibrium radius of an oil/water interface has also been verified down to very small radii, but the effect of ions leaching out from the silicate surfaces can greatly enhance the equilibrium meniscus (Kelvin) radius and must not be ignored in such processes. The phenomenon of the spontaneous condensation of water bridges between two surfaces has been observed, highlighting an additional important mechanism for trapping residual oil. The first measurements of the microviscosity of liquids in narrow channels show that the bulk liquid viscosity pertains down to very thin films in the case of both aqueous salt solutions and hydrocarbons. Results of the effects of salinity and pH on clay-swelling pressures are also described. These show that in addition to the expected long-range repulsive electrostatic force between charged surfaces in salt solutions, there is also a short-range (<20-Å [2-nm]), monotonically repulsive "hydration" force, which is an oscillatory function of distance below 15 Å [1.5 nm], with minima at discrete surface separations corresponding to the thickness of layers of water molecules: e.g., at 2.8, 5.6, 7.8 Å, etc. [0.28, 0.56, 0.78 nm]. The oscillatory force is believed to be responsible for the crystalline swelling of clays.
Application of Gradient Theory of Inhomogeneous Fluid to Prediction of Low Interfacial Tensions in CO2/Hydrocarbon Systems
Authors: Gupta Mukesh K. , Robinson Robert L.
Published: December 2007

Sahimi, Davis, and Scriven recently presented predictions of interfacial tensions (IFT's) for CO2/hydrocarbon systems using the gradient theory of inhomogeneous fluid (GTIF) model. In the present paper, additional calculations from the GTIF model are presented at low IFT's, and comparisons are made with experimental measurements. The results show that the GTIF model predicts "classical" scaling behavior at low IFT's, in conflict with experimental observations. Thus, while the GTIF model has been documented by its authors to yield good predictions at high and moderate levels of IFT, it could be inappropriate for use at the low levels of IFT (σ<0.1 mN/m [0.1 dynes/cm]) that may be required to enhance the oil displacement efficiencies in enhanced gas drives.
An Overview of Top-Drive Drilling System Applications and Experiences
Authors: Boyadjieff George I.
Published: December 2007

Top-drive drilling has become one of the new technologies of the 1980's. Application of this seemingly old concept is now widespread in most offshore areas of the world. Top-drive drilling may be one of the biggest changes made to the rotary-drilling method since the development of the rotary table.

This paper analyzes why the concept of drilling with top drive, similar to the very old concept of a power swivel, has suddenly become so successful. Applications and locations are presented to show the system's worldwide use. Results of more than 50 systems currently in operation are analyzed to present benefits and trends.

The results show surprising benefits for almost any type of well, and overall time savings generally exceed 20%. Benefits from the extended-reach potential associated with top drives are enormous. These results explain the primary motivation for most applications of the system.
History of a Milham Sand Water Flood Following Accidental Stimulation
Authors: Jones Frank T.
Published: December 2007

A brief history of the Waggoner "ABC" Milham sand waterflood project, in Wilbarger County, Tex., is presented. This water flood, operated by Cities Service Oil Co., has been successful in spite of irregular well spacing and injection patterns. Injection of slightly less than 19.5 million bbl of water over the past 11 years has resulted in the recovery of 2.77 million bbl of secondary oil. Efforts to maintain economical rates of production and injection on an individual well basis have resulted in sizeable frac treatments on both producing and injection wells. Results of these jobs are tabulated, and it is concluded that this method of well stimulation has extended the profitable life of individual wells.

Introduction

The Waggoner ABC water flood is located 13 miles southeast of Vernon, Tex. The name "Waggoner ABC", for the purpose of this report, applies to all leases supplied with injection water from the Waggoner ABC water station. Therefore, this term includes several offset leases acquired by the operator as the water flood expanded as shown in Fig. 1. Interest has been expressed in the performance of the Waggoner ABC water flood for several reasons.It is the oldest flood in Wilbarger County; consequently, a longer history is available for study and comparison.A high secondary recovery has been achieved.It has an irregular development pattern.Relatively large frac treatments of both injection and producing wells have been made.

Geology

The Milham sand of Pennsylvanian age is found at approximately 2,350 ft along a trend deposited on the south flank of the Red River uplift. The trend has the general appearance of an offshore bar, but it is believed to have been deposited further at sea as a result of current action on a shelf. Table 1 summarizes the reservoir information.
The Ultrashort-Radius Radial System
Authors: Dickinson W. , Anderson R. R. , Dickinson R. W.
Published: December 2007

A group of interrelated horizontal drilling and completion technologies, collectively called the ultrashort-radius radial system (URRS), was developed and is being progressively applied in the field. Multiple radiais can be placed at the same level and on multiple levels. Three-dimensional (3D) surveying is supplied. Horizontal completions can be provided, including 100%-fill gravel packing, in-situ electrolytic perforation and cutting, and flexible sand barriers (FSB's). Initial field applications were in unconsolidated formations.
A Preliminary Investigation on the Objective Function of Penetration Cost Applied to Optimized Drilling
Authors: Guo X. Z.
Published: December 2007

This paper describes a theoretical analysis of the penetration-cost objective function, specifically its first- and second-order differentiability, convexity, and feasibility, and presents the location and method of searching for the optimum drilling parameter. It discusses the features and practical significance of a combined isocost graph, such as determining the maximum economic results for each combination of bit weight and speed and providing a scientifically sound basis for modifying drilling parameters. This paper also gives a case study of the Zhong Yuan oil field.
The PVT Behavior of Methane in the Gaseous and Liquid States
Authors: Matschke Donald E. , Thodos George
Published: December 2007

Introduction

Considerable time and effort frequently are expended to establish, with a degree of confidence, the PVT behavior of pure substances. In particular, a great deal of experimental information contributed by a number of investigators is available in the literature. The data of each investigator, although significant in themselves, cannot be used with a high degree of confidence until they are compared with the continuum of information presented by others.

Current interest in thermodynamic and transport properties, for not only the gaseous state but the condensed state as well, requires that PVT information be presented for both regions. The density dependence on temperature and pressure, when presented as a continuum, is of considerable value in itself, especially since the available equations of state fail to properly account for the PVT behavior in the condensed state. For this reason and to incorporate PVT data recently presented in the literature, this investigation was carried out.

In their studies concerned with the thermodynamic properties of methane, Matthews and Hurd in 1946 utilized the data of Kvalnes and Gaddy and Olds, Reamer, Sage and Lacey to establish the PVT behavior of methane in the superheated region and the saturated liquid densities of Keyes, Taylor and Smith in conjunction with the Clapeyron equation to develop the densities for the saturated envelope.

Current activity sponsored by API Project No. 44 under the direction of F.D. Rossini has led to a tabular presentation of compressibility factors for gaseous methane in the superheated region. These values were obtained by using smoothed residuals, developed from experimental data and the Benedict-Webb-Rubin equation, to establish internally consistent compressibility factors for the real gas. This approach offers probably the most precise presentation of PVT information for gaseous methane to date.

The PVT behavior of methane also can be represented accurately by equations of state such as the Benedict-Webb-Rubin equation or the Martin-Hou equation. These equations, although valuable for analytically representing the PVT behavior, lack precision in the compressed-liquid region.
Current Status and Future Trends of Jet-Bit Drilling in China
Authors: Kexiang Li
Published: December 2007

Three levels in the development of jet-bit drilling in China are discussed, showing significant economic results for each higher pump-pressure level. Drilling practice in China has shown that there is still much room for a further increase of pump pressure and specific hydraulic horsepower. The development of jet-bit drilling is the main direction in upgrading drilling techniques in the near future. Laboratory studies have proved significant rock-cutting action by the combination of hydraulic and mechanical power. Bit hydraulics can do much more than bottomhole cleaning, and hydraulic parameters can be selected beyond the range of the Fullerton chart or the Amoco hydraulic drillability curve. More attention should be paid to rock-cutting by hydraulic power. The bit-weight/rotary-speed selection and mud performance should be optimized, along with the best use of hydraulic power. This approach should be followed as long as it results in a higher drilling rate and lower cost.
Increased ROP of Jet Drilling From Improvement of the Bottomhole Flow Field
Authors: Liao Rongqing
Published: December 2007

With the wide application of jet drilling, continuous research has been carried out to utilize fully the bit hydraulic power at the hole bottom. This paper describes an experimental study of fluid-flow direction in the flow field and discusses its application. The undesirable flow patterns of vortex, backflow, and stagnation were found to be the main factors affecting bottomhole scavenging efficiency. Improving the bottomhole flow field of a jet bit will increase the rate of penetration (ROP) and reduce the cost of jet drilling.