bluuebunny/crossref_metadata_2025 huggingface dataset:
The Use of Computerised Information Systems in Development and Production Operations: Part 1
Authors: Eckenhausen M. R. A.
Published: December 2007

Timely and reliable information is essential for managing the oil and gas Exploration and Production business. Information on the status and progress of development and production operations is vital for many disciplines in the organisation.

Computer Applications for Operations (CAO) are computerised information systems which support the planning and management of oil and gas field development and operations. These systems enable close monitoring, timely control and realistic evaluation and planning of operations. They stimulate "managing during the event" instead of "thereafter".
Pre- and Post-Stimulation Pressure Test Analysis and Its Role in the Design and Evaluation of Hydraulic Fracture Treatments
Authors: Cuesta J. F. , Elphick J. J.
Published: December 2007

Current technical literature contains a mass of theoretical writing in specialized areas of pressure transient analysis. This paper presents a review of analysis and design methodology specifically applicable to stimulation work. Firstly, it identifies all the flow regimes encountered in pre-stimulation tests and presents formulae necessary to calculate the reservoir parameters required for fracturing treatment design. Secondly, it develops a new methodology for fracturing treatment design and thirdly, the paper logically analyzes the flow regimes in poststimulation flow tests and reviews the formulae for calculating the parameters of the hydraulically created fractures. A field example explains the practical application of the method covered.
A Novel Class of Surfactants with Extreme Brine Resistance and its Potential Application in Enhanced Oil Recovery
Authors: Stournas S.
Published: December 2007

Most of the surfactants that have been employed or proposed for enhanced recovery applications are of the anionic type. It has been discovered that another class of surfactants, which incorporate both an anionic and a cationic center in the same molecule, possess interesting and unusual properties. These surfactants display great chemical and thermal stability and are totally immune to precipitation in the presence of monovalent and/or divalent cations; in fact, many of them are freely soluble in saturated solutions of sodium, calcium, or magnesium chlorides. In several instances they are capable of lowering the oil-water interfacial tension down to the millidyne region even in the presence of over 200,000 ppm of total dissolved solids. What is even more noteworthy is that in many instances the solubility behavior of these surfactants is opposite to the one usually observed, in that they are more soluble in concentrated brines than in dilute ones; in other words they display increased solubility as the salt content of the water increases.
A New Micellar Phase-Behavior Model for Simulating Systems with Up to Three Amphiphilic Species
Authors: Prouvost L. P. , Satoh T. , Sepehrnoori K. , Pope G. A.
Published: December 2007

A thermodynamic model has been developed for the phase behavior of micellar systems containing up to three amphiphilic species. This model has been tested against experimental data using chemicals typical of those used in surfactant flooding. A fairly good match of static phase behavior experiments has been obtained. The model has been implemented in a compositional simulator and found to be both simple enough and accurate enough for practical reservoir engineering calculations. One important design is to study the separation of the chemicals as they transport through the reservoir. This type of study should be useful in selecting surfactants and cosurfactants for optimal behavior. Relatively little experimental phase behavior data are needed to estimate the parameters in the model.
The Value of 3D Seismic in Field Development
Authors: Gaarenstroom L.
Published: December 2007

Since 3 Dimensional Seismic Surveys were introduced in the North Sea in 1976 Shell Expro has carried out ten such Surveys covering most of their fields.

The 3D seismic method is considered as a tool of growing importance for field development, especially for the marginal and economically sensistive fields. Appraisal and development drilling indicates that most fields are often more complex than originally anticipated.

Interpreted 3D seismic data available in the pre-development phase of a field's life in combination with appraisal well data could substantially support sound decisions on platform construction, drilling slots, and field development drilling.

In the example discussed, we show that an early understanding of complicated reservoir structures and structural discontinuities is a pre-requisite for optimum development of a complex structural-stratigraphic trap, such as the Cormorant Field (fig. 1).
Geological Modeling of a Heterogeneous Sandstone Reservoir: Lower Jurassic Statfjord Formation, Brent Field
Authors: Johnson H. D. , Krol D. E.
Published: December 2007

A geological/reservoir engineering modelling study of the Brent field's Statfjord Formation reservoir is outlined as follows: (1) it describes the geological characteristics of the reservoir, (2) it illustrates how these features were incorporated into a detailed (32 layer) computer simulation model, and (3) it summarizes some of the main conclusions concerning the nature of fluid flow through this heterogeneous reservoir in relation to possible field development scenarios.

The study demonstrates how complex, three-dimensional reservoir heterogeneity can be modelled with the latest type of large-capacity computers, such as the CRAY. Since these models are geologically more realistic, they can provide a better illustration of reservoir behaviour, which will improve performance prediction.
Use of Pressure Transient Testing To Evaluate Fractured Reservoirs in Western Venezuela
Authors: Da Prat G. , Mannucci J. , Prado L. , Millan E.
Published: December 2007

For a naturally fractured reservoir the existence of two semi-log straight lines when analysing real pressure transient data is seldom observed and some existing models for interpretation of fractured systems have always been subjected to controversy. In this study an analysis of pressure transient data taken in wells completed in fractured reservoirs in Western Venezuela has shown the existence of two well-defined parallel semilog straight lines which confirms the Warren and Root model from a practical viewpoint. The data was analysed using the type-curve corresponding to the solutions for a well with wellbore storage and skin in a reservoir with double porosity (pseudo-steady state flow). The analysis provides values for the dimensionless fractured storage parameter, ω and the dimensionless matrix-fracture permeability ratio, λ which are considered to be representative of a two-porosity system. Finally, a production forecast analysis is made for the reservoir using the obtained values of ω and λ.
Performance Testing of Well Completion Components Under Simulated Downhole Conditions
Authors: Weekers E. E. A. J. , Kastelein H. J.
Published: December 2007

Leakage of downhole equipment can have severe operational consequences, including effects on safety, but almost invariably results in delays at significant cost.

To improve component selection on the basis of technical data and to gain more insight into the failure modes and factors involved, Shell International have built a versatile well completion component test facility.

This paper briefly describes the facility and some of the operational experiences and results gained to date in tests on premium threaded tubing/casing connections. The test procedure for tubing/casing connections that is described in the paper is largely based on the API Recommended Practice 37. Some suggestions for improving the API procedure are also presented.
Analyzing Pressure Buildup Data by the Rectangular Hyperbola Approach
Authors: Haugland T. , Larsen L. , Skjaeveland S. M.
Published: December 2007

This paper examines applicability and limitations on the use of rectangular hyperbolas to analyze pressure buildup data, with emphasis on the determination of average pressure and flow capacity. It is shown that the method can be used with confidence only if it is applied to data that can also be analyzed by conventional semilog methods, and that it for such data is essentially equivalent to the conventional methods in terms of information needed and information obtained. If we use semilog data, then we can determine the flow capacity from the slope of the hyperbola, and we can determine the average pressure indirectly from the asymptote, provided we know the drainage area and the MBH function of the reservoir. Following stabilized flow we only need the shape factor in addition to the area. If we use the direct approach, and assume that the asymptote is equal to the average pressure, then we need the same type of information to make a proper choice of interval where the hyperbola should match the buildup curve. For this direct approach we will normally get. an estimate of average pressure that is less than m/1.151 psi (kPa) above the last wellbore pressure being used in the analysis, where m is the conventional semilog slope. Moreover, if we use only semilog buildup data following pseudosteady-state flow, then we can only get an accurate estimate of average pressure by this approach if the shape factor is close to 21, or higher.

If nothing is known about the reservoir, then the hyperbola method can be used to get. a rough estimate of the average pressure, but with a high degree of uncertainty if we only have data from a short buildup period. This claim follows from the many examples included in this paper of asymptotes determined from hyperbolas matched to dimensionless synthetic buildup data plotted vs. interval midpoints.
Static Pressure Gradient Reversals in Gas Wells
Authors: Bender C. V. , Holden W. R.
Published: December 2007

Static pressure surveys in gas wells have frequently shown a phenomenon in which pressure gradients decrease with increasing depth. Computer simulations have indicated that the main cause of these gradient reversals is reasonable temperature increases with increasing depth. To explain the pressure gradient reversals exhibited in several field examples, seven temperature distributions were incorporated in the computer model.
Evaluation of Core Damage Caused by Oil-Based Drilling and Coring Fluids
Authors: Thomas D. C. , Hsing H. , Menzie D. E.
Published: December 2007

This paper discusses the chemical damage to cores created when oil-based coring fluids have been used in the coring operation. Changes in formation wettability and emulsification in the pores caused by oil-based fluids affect the analysis of the cores.

Two methods were used to evaluate the degree of damage to the core. First, the effective permeability to oil and to brine of a core were compared before and after injection of a drilling or coring fluid filtrate. Second, the effective permeability to oil of a core was compared before and after injection of a drilling or coring fluid filtrate at various pressure drops. Instrumentation included an ultra-speed centrifuge and permeability measurement apparatus. The experimental results indicate that the irreducible brine saturation and wettability could be changed.
Archie's m for Permeability
Authors: Hagiwara T.
Published: December 2007

The permeability of a rock may be given by k = const, ϕm  where ϕ, m, and  are the porosity, Archie's "m", and the average pore throat radius squared of the rock. Or using a capillary pressure curve, we may write k = const. Sm/p2f (G) where (S, p, G) are either Thomeer or Swanson parameters.
Effect of CO2 Flooding on Dolomite Reservoir Rock, Denver Unit, Wasson (San Andres) Field, TX
Authors: Mathis R. L. , Sears S. O.
Published: December 2007

This report documents results of a study to determine whether brine and carbon dioxide (CO2) injection significantly changes total porosity in a dolomite reservoir. Pre- and postpilot cores from closely-spaced wells in the Shell Western E&P Inc. Denver Unit CO2 pilot provided the necessary data. We concluded that only minor porosity enhancement resulted from brine dissolution of anhydrite.
Linear Stability Analysis of Immiscible Displacement Including Continuously Changing Mobility and Capillary Effects: Part II— General Basic Flow Profiles
Authors: Huang A. B. , Chikhliwala E. D. , Yortsos Y. C.
Published: December 2007

This paper reports on the continuation of previous work1 in the linear stability or immiscible, two-phase flow displacement processes in porous media that includes continuously changing mobility and capillary effects.

In Part I simple Dasic-flow profiles that allow exact solutions to be obtained were investigated. This work uses the previous formulation in terms of eigenvalue problems to examine the stability characteristics of general basic flow profiles. hotivated by the connection between the present problem and the stability of shear layers in parallel flow2, the numerical method of "matched initial values" successfully used in the stuay of latter3 is adopted in this numerical investigation.

First, the stability of non-capillary flows corresponding to a straight line fractional flow is examined. The mathematical equivalence of these flows to miscible Displacement in the absence of diffusion is established. It is shown that such displacement is neutrally stable to small disturbances of any wavelength provided that the total mobility is continuously increasing in the direction of flow. The disp1acement is unstable to small disturbances of any wavelength if the total mobility profile contains any segment of decreasing mobility. The numerical results are in agreement with the exact solutions of part I in the limits of small and large wavenumber.

Next, the stability cf capillary fiov.-s for general basic flow profiles is examined. An analysis of the eigenvalue problem indicates the existence of a single stability curve parametrized by the viscosity ratio and relative permeability ano capillary pressure characteristics. Numerical investigations using power-law functional forms for the relative permeability show that the displacement is stable to any small disturbance provided that the viscosity ratio μoμw takes values below a critical value. The latter can toe evaluatec, fairly accurately both for arbitrarily fixed saturation end-points and the Buckley-Leverett problem, by the condition that the end-point total flow mobilities are equal.

For values of the viscosity ratio above the critical, the numerical results show that the displacement is unstable to small disturbances of wavelength larger than a critical value, and stable otherwise. This effect is attributed to the stabilizing" action of capillarity. Values of wavelength corresponding to the highest rate of growth are numerically determined. It is found that stability is enhanced at lower values of the capillary number and the injection rate. Finally, a limited sensitivity study of the effect on stability of the functional forms of relative permeability ana capillary pressure is carried out.
Rheological Characteristics of Adjustable Cross-Linked Fracturing Fluids
Authors: Royce T. N. , Beck L. M. , Rickards A. R.
Published: December 2007

A study was done evaluating apparent viscosity and fluid stability by allowing cross-linking to occur at varying times during and after a period of high shear. A high temperature closed-loop pipe viscometer was used for this process. To observe the interdependencies of shear history, cross-linking time, and apparent viscosity, two adjustable cross-linked fracturing fluid systems were employed. As part of the study, a plexiglass parallel plate fracture and wellbore model was used to observe proppant transport for both fluid systems at ambient temperature.

Results of these studies indicate that when cross-linking time is less than the high shear duration period, both the maximum viscosity and the fluid's stability are reduced. The amount of reduction is shown to be related to the difference between the high shear duration period and the cross-link time. Also, from observations made on the plexiglassfracture model, a better understanding of the relationships among treating string residence time, cross-link time, fluid stability, and proppant transport in the vicinity of the wellbore can be developed.
Current Drillstem Testing Practices: Design, Conduct & Interpretation
Authors: Erdle James C.
Published: December 2007

Improvements in Drillstem Test design, monitoring and interpretation procedures which maximize the probability of a successful test and permit well performance predictions.
Depletion Experiences and Modeling of Mixed-Porosity, Fractured, Cavernous Reservoirs in Hungary
Authors: Bálint V. , Pach F.
Published: December 2007

Publications are relatively sparse about the analysis and modeling of mfxed porosity, fractured karstic reservoir /MPFKR/. The oil field Nagylengyel is of such type. To estimate the texture /structure/of the field some probability model was developed. By the application of the model the water driven primary depletion and the depletion by a secondary gas cap could be followed up rather well, showing results corresponding to the pilot plant and field tests.
A New Electromagnetic Propagation Tool for Well Logging
Authors: Iskander M. F. , Rattlingourd S. L. , Oomrigar J.
Published: December 2007

The use of electromagnetic (EM) energy to evaluate rock formations and, in particular, to determine the water saturation, as well as to infer the oil and gas saturations within pores, has recently received much attention. The dielectric properties of rocks measured by these tools at microwave frequencies are strongly dependent on the water saturation and are relatively insensitive to salinity changes. Therefore, dielectric properties measurements, when used with the data obtained from other well-logging tools (e.g., those involving neutron and gamma ray densities measurements), provide valuable information that helps distinguish between hydrocarbon-bearing and water-bearing zones. The presently available EM tools are generally single frequency devices. In addition, it is difficult to design low-frequency tools of reasonable sizes and of controlled radiation patterns.

In this paper, we present a new EM tool which is based on the design of an open transmission line coupler. The main features of this tool include its broadband performance and its compact size, even down to frequencies as low as in the kHz range. It thus provides the possibilities of: Logging at various depths of investigation by varying the frequency and the separation between the couplers.The combination of low- and high-frequency measurements to separate specific dielectric parameters, such as the dc conductivity.The broadband coupling characteristics of the new coupler makes it possible, for the first time, to make swept frequency and time-domain well logging measurements.The borehole effects are minimized, since the tool is a patch-type device.

Unlike the other low-frequency EM tools, the new coupler has very well-controlled coupling characteristics, with the major part of the energy transmitted to the rock formation.

Results of our experimental evaluation of the designed tool, including measurement of the depth of investigation and the attenuation and phase shift between the transmitting and receiving couplers as a function of frequency, will be presented. It is generally shown that lower frequencies provide less attenuation and larger depth of investigation.

The tool performance is also evaluated by utilizing a computer program where the rock formation is simulated by two-dimensional cross sections with a borehole and a flushed zone of variable thickness. Results of these numerical simulations are presented. At lower frequencies, it is shown that the mud cake effects are minimized and the sensitivity of the measurements to the formation beyond the flushed zone is improved. Limitations on using planar models to evaluate the EPT performance are also discussed.

The new EM tool is capable of realizing the full potential of dielectric logging. It has the advantages of both presently available high- and low-frequency EM tools combined together. It also facilitates the unique capabilities of swept-frequency and time-domain well logging.
Deep Sucker Rod Pumping for Gas Well Unloading
Authors: Henderson L. J.
Published: December 2007

Exxon Company, U.S.A.'s Pyote Gas Unit 14-1 in the Block 16 (Ellenburger) field became the world's deepest rod pumped well on October 7, 1983. The rod pump was installed at 16,850 ft. in an attempt to extend the productive life of the well. The artificial lift system was designed to lift wellbore fluid that was restricting the flow of gas, thus allowing the gas to be produced up the tubing-casing annulus. Implementation of the project was possible because of the recent improvements in predictive techniques, materials available for rod pumping, and industry's experience in artificial lift.
Experimental Investigation of the Performance Characteristics of Hydrocyclones
Authors: Sharma S. P.
Published: December 2007

A mathematical model of hydrocyclone classifiers used to process drilling fluid is presented. Four basic non-dimensional parameters are defined to describe the performance of the hydrocyclones. The mathematical model is based on data acquired during a series of tests using 3", 4", 5", and 7" cones with interchangable parts. The analysis of the model indicates a non-Stokesian behavior in the classification process. According to the present findings, a Stoke-sian model tends to underdesign the hydrocyclones by at least 15-25%. Further, an optimum value of 4 × 104 for the inlet Reynolds number to the hydrocyclones has been found. A term called the "Performance Parameter," introduced in the analysis, can assist a designer to search for an optimum design through a parametric study.
Comparison of Methods for Determining In-Situ Leakoff Rate Based on Analysis with an On-Site Computer
Authors: Cooper G. D. , Nelson S. G. , Schopper M. D.
Published: December 2007

Two methods for determining a rate of fluid loss during a fracturing treatment have been proposed. In each method, the basis for determination of the in situ leakoff rate is the downhole pressure behavior after initiating a small fracture in the zone of interest. The first method, by Nolte, utilizes a master curve fit of data derived from the pressure decline following a fracturing treatment. The second method, by Nierode, relates two or more instantaneous shut-in pressures (ISIP's) as hydraulic fracturing progresses. Nierode then calculates from the pressure changes a rate of fluid loss.

This paper discusses the analysis of downhole pressure behavior using both techniques, and direct comparisons of results are made. These studies were conducted throughout the North American continent using an on-site computer. Furthermore, limitations rarely encountered for both the Nolte and Nierode analyses are discussed. The main limitations are establishing heights for the Nolte in situ leakoff analysis and increasing pressures during the Nolte pressure decline phase. For the Nierode technique, the main limitation has been initial ISIP's higher than the final ISIP.

Combined leakoff values determined from laboratory tests and reservoir information are compared to in situ leakoff rate determinations. Specific emphasis is placed on determining the effects of natural fractures, fracture heights, and permeability on these fluid loss techniques.
Establishing the Effective Aquifer Pressure Controlling Water Drive for Gas Storage Cycles
Authors: Katz D. L. , Shah D. P.
Published: December 2007

In water drive gas storage reservoirs, water influx and efflux rates may be determined by the simplified pseudo steady-state method. It is necessary to determine the water movement rate per unit driving force and established an appropriate distance in the aquifer from the gas reservoir at which the aquifer pressure is stable during the storage cycles. A method for this determination is demonstrated on an aquifer storage reservoir. The joining of the water movement with the p/z material balance permits a more accurate method of verifying gas inventory. This new procedure is presented to up-grade the verification of gas inventories as applied to an Illinois aquifer storage reservoir.
A New Iterative Technique With Updated Curves for Estimating Average Reservoir Pressure of Gas Wells From Buildup Tests
Authors: Toh C. H. , Farshad F. F. , LeBlanc J. L.
Published: December 2007

The dimensionless functions used in traditional methods for estimating average gas reservoir pressure can give erroneous results, since the assumption that the product of viscosity and compressibility is essentially constant is not valid for highly compressible fluids.

In this paper a new approach, accounting for the change in the viscosity and compressibility, has been proposed for gas reservoirs. This involves the application of a perturbation technique to obtain a solution of the diffusivity equation for real gas flow in bounded systems. A set of new dimensionless functions was generated and used to estimate the average reservoir pressure by a proposed method.
The National Petroleum Council EOR Study: Thermal Processes
Authors: King J. E. , Blevins T. R. , Britton M. W.
Published: December 2007

The EOR thermal potential of the United States has been estimated from an improved data base and individual reservoir assessment. Reservoirs with ongoing thermal projects were evaluated by means of an industry survey. Future projects were evaluated by simplified model predictions. Predictions for Implemented and Advanced Technology compare current proven practice with anticipated future technology development. For an assumed base economic case, the Implemented Technology potential is estimated at 6.5 billion barrels. The Advanced Technology potential for this case is estimated at 10.5 billion barrels. These values include oil consumed as generator fuel.
Analysis of Temperature Distribution and Performance of Polycrystalline Diamond Compact Bits Under Field Drilling Conditions
Authors: Zijsling D. H.
Published: December 2007

Analysis of laboratory tests on full-scale field-worn polycrystalline diamond compact (PDC) bits showed the frictional heat at the rock/bit interface to be largely generated at the diamond cutting edges of the PDCs. Inspection of the observed wear of the PDCs together with the analysis revealed that the diamond layer attacks the formation at a large negative rake angle and that rock flour accumulates under the cutting edge during drilling, forming a stable buildup edge.

A thermal model has been developed on the basis of these results to predict the temperature distribution in the PDCs under quasi-static drilling conditions. The maximum temperature is found to occur at the PDC's cutting edge and is virtually independent of PDC position under normal rotary drilling conditions. At elevated rotary speeds however, the maximum cutting edge temperature occurs in PDCs at the gauge of the bit. This temperature can exceed the boiling point of water-based drilling fluids, resulting in higher cutting edge temperatures and wear rates of the PDCs which may lead to premature failure of the bit. Under normal rotary drilling conditions the maximum cutting edge temperature increases with the penetration rate. For the higher speed positive displacement motor drilling applications however, bits can be designed to give a virtually constant maximum cutting edge temperature over a wide range of bit penetration rates. This is achieved by selecting the optimum number of cutters whilst making use of the thermal insulating capacity of the buildup edge under the PDC. In addition a further reduction In the maximum cutting edge temperature can be achieved at these speeds by reducing the diamond layer thickness of the relevant PDCs.

The results also showed that for effective cooling of the PDCs fluid velocities of at least 50 m/s are required along the diamond surfaces when drilling with oil-based fluids. With water-based drilling fluids, higher velocities should be used to prevent bit balling or boiling of the drilling fluid at the diamond surface of the PDCs.
The Interpretation of Tracer Test Response from Heterogeneous Reservoirs
Authors: Smith P. J. , Brown C. E.
Published: December 2007

Tracer testing is an increasingly used tool for reservoir characterisation. Hitherto either qualitative results (such as preferential flow paths) or simple conceptual models for the reservoir variability (such as layering) have been used. These studies allow a more general class of heterogeneous reservoirs to be investigated.

The results confirm that the characterisation of reservoir heterogeneity from tracer response requires both a measure of the dispersivity plus a knowledge of the correlation scale length and variability within the reservoir. The application of this work will have particular significance to the characterisation of reservoirs prior to the prediction of EOR schemes.
Role of Roughness and Edges During Imbibition in Square Capillaries
Authors: Lenormand Roland , Zarcone Cesar
Published: December 2007

The displacement of one fluid by another in a two-dimensional etched network has been described at the microscopic level: during imbibition, the wetting fluid can flow through the roughness of surfaces, along the edges of the ducts (rectangular cross-section) or in the bulk of the ducts. In this paper, we present results for the time scales of these different mechanisms and the consequences for imbibition in large 2-dimensional networks of capillaries and approximate laws for the flow rates by roughness and corners are calculated in an infinitely long square duct. A theoretical model is built for describing the relationship between the fluid configuration and the Capillary Number (or flow rate):

VERY LOW FLOW RATE: The wetting fluid can reach all the parts of the network by flowing along the surface roughness. It begins to fill the bulk of the smallest ducts and the number of filled ducts increases with time. This is a Cluster growth mechanism. LOW FLOW RATE: The wetting fluid can flow along the corners of the ducts but not through the roughness. The mechanism is like Invasion Percolation but the wetting phase flows along the grains of the solid in a special network called: DUAL network. HIGH FLOW RATE: The wetting fluid only flows in the bulk of the ducts and the mechanism is a Frontal Drive without fingers nor trapping of the nonwetting phase.
Reservoir Management of the Bryan (Woodbine) Field
Authors: Givens J. W.
Published: December 2007

The Bryan (Woodbine) Field is a major oil reservoir which was recently discovered in Southeast Texas. The initial reservoir performance, reservoir rock properties, and reservoir fluid data indicated that the reservoir pressure would soon be depleted below the bubble-point pressure. The operators and working interest owners in the field realized the need for unitization in order to maximize the ultimate recovery from the reservoir and therefore began cooperative discussions and regular meetings early in the reservoir life. Because the reservoir is located largely under the city limits, there are a number of unique problems related to development and unitization. A unitization formula has been negotiated and the Unit Agreement is being circulated for ratification. Engineering studies of secondary recovery by waterflooding are in progress.

The purposes of this paper are (1) to present the geology, performance history, and reservoir parameters of the Bryan Field, (2) to describe the unitization process and its status, and (3) to discuss enhanced recovery alternatives.
The Tertiary Extension of the Wizard Lake D-3A Pool Miscible Flood
Authors: Backmeyer L. A. , Guise D. R. , MacDonell P. E. , Nute A. J.
Published: December 2007

A tertiary extension of the existing secondary hydrocarbon miscible flood in the Wizard Lake D-3A Pool was implemented in October, 1983. The extension will result in the oil-water contact being lowered 22.6 meters (74.1 feet) to allow miscible displacement of the residual oil in the water flushed portion of the reef. This water flushed zone was formed when the oil-water contact rose during primary depletion of the reservoir from discovery in 1951 until the implementation of the secondary miscible flood in 1969, and also during the repressuring phase of the secondary miscible flood. Ultimate recovery from the pool is expected to be 59 539 103m3 (374.49 MMSTB) or 95.95 percent of the original oil-in-place; which is 4 531 103m3 (28.50 MMSTB) higher than the secondary miscible flood and 18 583 103m3 (116.88 MMSTB) more than under primary depletion.

This paper reviews the implementation and monitoring of the tertiary extension of the miscible flood and also the performance of the pool to January 1, 1984.
Design and Implementation of a Miscible Water-Alternating-Gas Flood at Prudhoe Bay
Authors: Rupp K. A. , Nelson W. C. , Christian L. D. , Zimmerman K. A. , Metz B. E. , Styler J. W.
Published: December 2007

An enriched, Water-Alternating-Gas (WAG), miscible flood was brought on stream in December 1982 in the Prudhoe Bay Field on Alaska's North Slope. This paper outlines details of the Project and traces its evolution from conceptual engineering through start-up to initial performance.

The Project involves an area containing 442 million barrels original oil in place. The 3,650 acre Project Area includes sixty 80-acre spaced wells in eleven inverted nine-spot patterns. Facilities process the 40 to 45 MMscf/D of miscible injectant which is then injected alternately with water on a 3 month/6 month gas/water cycle in eleven injection wells. An extensive surveillance program includes one fiberglass cased observation well, a comprehensive cased hole logging program, and radioactive gas tracers. The Project will consist of WAG injecting a slug of more than 10% total pore volume (TPV) miscible gas. The miscible gas will be injected at a rate of approximately 1% TPV per year, followed by. water injection to displace miscible gas through the reservoir and tertiary oil to producing wells. The estimated incremental-to-waterflood recovery is 5.5% of the original oil in place or 24 million barrels of oil.
Comparison of Digital and Analog Techniques for Determining Sonic Velocity from Borehole Acoustic Waveforms
Authors: Wu P. T.
Published: December 2007

Analog threshold detection, or the first motion detection (FMD) method, has been the traditional method for estimating formation compressional slowness. Recent advances in the design of wireline acoustic tools now allow near simultaneous acquisition of sonic waveforms from a downhole multireceiver array. Kimball and Marzetta1 proposed a digital method based on semblance called slowness-time-coherence (STC) to determine the slowness (Δt) of all coherent components of the waveforms. The purposes of this paper are to compare and explain the differences between the compressional slowness obtained from the FMD and the STC methods under different formation conditions.
The Analysis of the Invaded Zone Characteristics and Their Influence on Wireline Log and Well-Test Interpretation
Authors: Phelps G. D. , Stewart G. , Peden J. M.
Published: December 2007

This study examines the invasion of a hydrocarbon bearing formation by drilling fluid filtrate, and investigates, with the aid of a numerical model, the significance of capillary forces on the resulting displacement.

It is observed that in high permeability zones, capillary imbibition can draw filtrate into the formation faster than it is lost through the filtercake, which is assumed to control the fluid loss rate.

On the basis of conclusions drawn from the numerical study, the phenomena of supercharging (the difference between the water phase pressure at the sandface and the undisturbed formation pressure) has been reanalysed, and an equation recognising supercharging as a two phase problem is presented. Depending on the character of the displacement, supercharging in a hydrocarbon zone can be enhanced or reduced due to the presence of mud filtrate.

A field example is used to validate the proposed theory, as well as to demonstrate how the down hole static fluid loss rate may be determined from repeat formation tester (RPT)* based measurements.
A New Approach to Casing Design for Salt Formations
Authors: Hackney R. M.
Published: December 2007

Data from over forty incidences of casing collapse in the Midcontinent area is used to develop a new design method for casing to be set across salt formations. The new method reduces overdesign of casing 37% over hydrostatic collapse designs while predicting all failures. This design method involves modification of the standard Von Mises equations to account for the nonuniform collapse loads generally presented by salt formations. The modification involves use of curved beam theory and correlation to field data. It is valid across the midcontinent region and may be adapted to other areas. Additionally, tight casing due to excessive elastic deformation may be considered as well as failure due to plastic collapse.

Discussion includes current industry design methods and the mechanics of formation flow.
Thermally Stable Synthetic Diamond Drill Bit Proves Effective in Gulf Coast
Authors: Stoddard J. , Cerkovnik J.
Published: December 2007

A new thermally stable diamond cutter has proven effective in drilling medium to hard limestone and moderately abrasive sand. This new type of diamond is called "Ballas" which is a synthetic polycrystalline diamond. Ballas can be thought of as a more refined, or pure, polycrystalline diamond compact cutter which is free of foreign material within or attached to the diamond mass. The Ballas cutter is thermally stable up to 1200 degrees C compared to a conventional polycrystalline diamond compact which is only thermally stable up to 750 degrees C. This additional temperature resistance allows the use of self sharpening polycrystalline diamond to be used in harder, more abrasive formations which cannot be cut with the present diamond compact material.

The use of the Ballas material has shown significant rate of penetration advantage in drilling the carbonate formations of East Texas and the depleted sands of So. Louisiana. Along with the success, present bit designs have experienced some problems drilling some of the clean plastic shales common on the Gulf Coast.
The Rise and Fall of the Offshore Contract Drilling Industry, 1979 to 1983
Authors: Rankin M. D.
Published: December 2007

As the offshore contract drilling industry moves into its third decade, it faces a number of serious and expensive problems which defy easy solutions. Over a period of three years, the industry has been transformed from a thriving, profitable business into one of incredible surplus capacity and economic margins insufficient for long term survival.

Few other industries can claim the level of capital growth and entrepreneurship which has been the trademark of the contract drilling business. The industry is largely free of commercial regulation although a number of developing countries have implemented policies which severely limit the ability of private concerns to enter the market. By and large, offshore contract drilling is a textbook example of the free marketplace-living and dying by the double edged "sword" of supply and demand.

The purpose of this paper involves a general assessment of industry performance over the period 1979-1983, years which encompass the latest "boom-bust" cycle. The analysis is intended to be an objective assessment, rather than an indictment, with the hopeful result that the industry will eventually profit from the less fortunate aspects of the recent past.
Air Drilling Practices in the Midcontinent and Rocky Mountain Areas
Authors: Sheffield J. S. , Sitzman J. J.
Published: December 2007

This paper is adapted to air drilling in the Midcontinent and Rocky Mountain areas. A compilation of operational experience and design data dealing with air drilling is explained and summarized.

Discussion includes when and when not to air drill, how to plan for air drilling, and different drilling strategies employed during air drilling operations.

Operational experience is reviewed in several Rocky Mountain areas and in Arkansas. Air drilling has proven to be a significant factor in reducing drilling costs in these areas. Conclusions and recommendations are made with regard to the major areas discussed in the paper concerning what well conditions lend themselves to air drilling, and when to use mist, inhibited mist or foam.

Methods to utilize air drilling to its fullest potential such as the use of air hammers and polymer foam drilling are also discussed.
Design Outline for a Microcomputer Drilling Management Program
Authors: Weatherspoon R. L.
Published: December 2007

This paper outlines the design considerations and performance criteria of a microcomputer program developed for drilling management. The program utilizes existing daily report procedures used in most offices to build an on-site well information data base. The data base is then used for real-time operations optimization, report generation, and subsequent well analysis. It is totally self-contained for use on IBM-XT microcomputer. The outline, while specific to the IBM-XT, can be used by any data processing department to structure their own drilling management system for micro, mini, or mainframe computer installations.
The Well Testing Program at the Heber Geothermal Field
Authors: Da Sie W. J. , Hoang V. T.
Published: December 2007

In 1984, Chevron Geothermal Company of California embarked on the drilling and testing of geothermal development wells for the Dravo dual flash and San Diego Gas and Electric binary plant both scheduled for startup in 1985. This paper describes the methods and special techniques used in processing and analyzing the large volumes of pressure data gathered during the extensive single well and interference testing program. A summary of the testing results is presented which show the Heber reservoir to be of high quality with excellent communication between the wells drilled. Special phenomena observable in some of the interference testing results, possibly related to spatial transitions in reservoir characteristics, are described in some detail.
Hydraulic Fracture Growth During Steam Stimulation in a Single-Well Test
Authors: Holzhausen G. R. , Card C. C. , Raisbeck J. M. , Dobecki T. L.
Published: December 2007

Ground deformation was monitored for nearly ten weeks during the first cycle of steam stimulation in a single-well test using an array of high-resolution borehole tiltmeters. The test was conducted in a section of the Athabasca oil sands having properties similar to the unconsolidated oil sands of California. The 310-meter injection depth was also comparable to the depth of thermal stimulation in many California oil fields. Ground response indicated that steam injection was not a continuous process, but rather was characterized by numerous episodic events. During these events wellhead pressure dropped (in one case by 2650 kPa), boiler feed rate increased by a few percent, and the ground surface within the instrument array was lifted up. Pressures again began to rise and the ground surface subsided within a few hours of the beginning of an event, but subsidence always preceded pressure increase. The magnitudes of the pressure and deformation changes varied from event to event, apparently unsystematically.

The events are interpreted to have resulted from breakdown of the oil sands and attendant propagation of hydraulic fractures away from the wellbore in approximately horizontal planes. Larger fractures may have continued to propagate until internal pressures were insufficient to lift the overburden, at which time they collapsed. Fracture growth terminated at higher pressures in events for which deformation changes were small, perhaps because of inelastic blunting of the fracture tips. Modelling suggests that the radii of fractures formed in the larger events may have been about 160 meters, whereas those formed in the smallest events had radii of about 40 meters.

A delay of three weeks between the start of steam injection and the occurrence of the first episodic event suggests that there may have been major modification of the in-situ stress state during this period. Pressure records from cold-water hydraulic fracturing a week before the start of steam injection indicate that this fracture was vertical, from which we infer that the most compressive component of in-situ stress was also vertical. Gradual heating of the oil sands during steam injection should have closed the vertical fracture by thermal expansion, and then led to an increase of horizontal compression as further lateral expansion was suppressed. Formation of horizontal fractures after three weeks of steaming is consistent with a modified in-situ stress state in which horizontal exceeded vertical compression.
Steady-State Analysis of In-Situ Combustion
Authors: Agca C. , Yortsos Y. C.
Published: December 2007

The success on an in-situ combustion project depends primarily on the development of a stable combustion front, which propagates at constant velocity, and sustains a constant temperature high enough for the efficient mobilization of the original reservoir oil. To determine the conditions favoring a stable combustion front, a numerical solution of the equations describing conservation of mass and thermal energy is typically implemented using thermal simulators.

In this paper, an alternative simplified steady-state analysis is attempted by treating the combustion region as a moving zone of constant length, within which the oxidation reaction is taking place. Steadystate solutions are obtained which relate the combustion characteristics, such as front velocity, combustion temperature, and reaction extent, to the reservoir and process parameters. In particular, the effects of reservoir thickness, heat losses to surrounding formations, initial reservoir temperature, injection rate, and injection pressure are analyzed.

It is found that, for typical values of the parameters three steady-state develop, one at a low temperature near the initial reservoir temperature, and one at a sufficiently high temperature, both of which are stable, and one at intermediate temperatures, which is unstable. In such cases, preheating (ignition) near the injection well is necessary for the desired steady-state at the higher temperature to be reached. The region in the values of the parameters where such behavior occurs is numerically determined. It is also found that single steady-states may develop, either at a low temperature implying an unsuccessful combustion project, or at a high temperature implying spontaneous ignition. Conditions are obtained that determine the range in the values of the parameters where such cases prevail.

The steady-state results indicate that the combustion temperature increases with an increase in reservoir thickness, injection rate and injection pressure. The front velocity was found to vary almost nearly with the injection rate, although it is rather insensitive to the values of most of the other parameters. The combustion reaction reaches completion at higher temperatures.

The simple analysis presented here delineates the range of the values of the reservoir and the process parameters that would result into favorable combustion characteristics and thus a successful in-situ combustion project. The numerical results obtained agree both qualitatively and quantitatively with field values previously reported for successful in-situ combustion projects.