bluuebunny/crossref_metadata_2025 huggingface dataset:
An Automatic, Unstructured Grid-Generation System for Geologically Complex Reservoirs
Authors: Kocberber Sait
Published: December 2007

This paper presents an automatic, 3D, locally unstructured hybridgrid-generation system for sloping faults. This gridding system replaces a portion of an existing finite-difference grid around sloping faults with a finite-element grid made of tetrahedrons. This innovative approach retains the finite-difference character of the grid and minimizes the decrease in computational efficiency. This paper discusses the details of the gridding techniques used and provides several example grids that demonstrate that locally unstructured grids can accurately represent geologically complex reservoirs.
A New Approach for Residual and Jacobian Arrays Construction in Reservoir Simulators
Authors: Lim K. T. , Schiozer D. J. , Aziz Khalid
Published: December 2007

We describe a simple and convenient approach for constructing the residual and Jacobian arrays in a reservoir simulator. The key idea is to keep track of all the "connections" in a model, as opposed to the conventional approach of keeping track of gridblocks and wells when computing the flux terms. Each gridblock may have a variable number of connections that depends on the grid geometry. A connection, however, always links two nodes, which can be gridblock nodes or source/sink nodes. A data structure identifying each pair of connected nodes and the corresponding geometric factors of each connection are sufficient to implement this approach. No-flow boundaries and internal barriers are excluded because of the absence of a connection. The residual function computation is divided into two principal steps: (1) computation of the accumulation term, which is local to each grid block, and (2) computation of flux terms and/or potential difference between all connections by traversing the list of connections and their allocation to the appropriate nodes. This approach can be extended in a natural way to include node connections in well and surface flowline networks.
SWUG Story
Authors: Adams W. T. , Bouett L. W. , Gamble S. D.
Published: December 2007

This paper documents the rise, the history, the workings, and the future prospects of a vigorous and unusual software user group. The software with which the user group mostly concerns itself is a single vender's set of independent programs, which analyze geological, reservoir, and production data stored in the vender's proprietary database structure. Since its introduction about 7 years ago, this PCbased software has become widespread in many of the client companies and much of the industry; it is often treated as a de facto standard. The user group is independent of the vender, but works closely with the vender on both bugs and enhancements. It consists of members from both small and major operating companies, service companies, as well as consultants. The group documents its work and keeps in touch with members, but it is officially, and in most other respects, an informal group. Its one official function may be unique to our industry: the group has a representative with a seat on the vender's software development committee (SDC), whose recommendations are carried directly to the vender's parent company's board of directors (BOD).
Using Distributed Processing on a Local Area Network To Increase Available Computing Power
Authors: Capps K. S. , Sherry K. J.
Published: December 2007

The migration from central computers to desktop computers distributed the total computing horsepower of a system over many different machines. A typical engineering office may have several networked desktop computers that are sometimes idle, especially after work hours and when people are absent. Users would benefit if applications were able to use these networked computers collectively.

This paper describes a method of distributing the workload of an application on one desktop system to otherwise idle systems on the network. We present this discussion from a developer's viewpoint, because the developer must modify an application before the user can realize any benefit of distributed computing on available systems.
A Theory of Transitional and Turbulent Flow of Non-Newtonian Slurries Between Flat Parallel Plates
Authors: Hanks Richard W. , Valia Maheshkumar P.
Published: December 2007

A theoretical model is developed which Permits prediction of velocity profiles and frictional prediction of velocity profiles and frictional resistance factors for the isothermal flow of Bingham plastic non-Newtonian slurries in laminar, transitional, and turbulent flow between that parallel walls, in rectangular ducts of large width-to-height ratios, or in concentric annuli with radius ratios approaching unity. The theory is tested with available frictional resistance data for a range of Hedstrom numbers from 10(4) to 10(8) and a set of theoretical design curves of friction factor vs Reynolds number is developed. The model indices that for certain ranges of Hedstrom number (the non-Newtonian index) turbulence is suppressed relative to Newtonian flow behavior, whereas for other ranges of Hedstrom number, the converse is true.

Introduction

The handling of non-Newtonian fluids in turbulent motion is an important operation in many modern technological processes. Despite this fact, however, little has been done to develop models which are comparable to those available for Newtonian turbulent flow. In particular, a model of the transitional flow regime is notably lacking. Recently, a theory of laminar-turbulent transition for non-Newtonian slurries flowing in pipes and parallel plates was presented. A theory of parallel plates was presented. A theory of transitional and turbulent flow of Newtonian fluids in pipes and parallel plate ducts has also recently been developed. This theory permits the analytic calculation of the friction factor-Reynolds number curves as a continuous function of Reynolds number from the critical Reynolds number of laminar turbulent transition to any condition of turbulent flow. In this paper these two theories will be combined in order to develop a theory for the transitional and turbulent flow of non-Newtonian slurries in parallel plate ducts, rectangular ducts of large width-to-height ratio, or concentric annuli with radius ratios approaching unity.

THEORETICAL ANALYSIS

The rheological model which will be used to represent the non-Newtonian slurry behavior is the linear Bingham plastic model,

..............(1)

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

For this model the laminar flow curve is given by

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

where q = 2v/b, b is one-half the distance between the plates, w = b(−dp/dz) is the wall shear stress, and D = o/ w. The end of the laminax flow, region is determined by the equations

........(4)

.........(5)

where N Rec = 4bp vc/ p is the critical Reynolds number, Dc is the critical transitional value of D and N He -16bp o/ p is the Hedstrom number expressed in terms of the hydraulic diameter for parallel plates. parallel plates. The calculation of the transitional flow field for this type of fluid will be based upon the model developed by Hanks for Newtonian fluids.

SPEJ

P. 52
An Approach to Handle Discontinuities by the Stehfest Algorithm
Authors: Chen Chih-Cheng , Raghavan Rajagopal
Published: December 2007

A simple, yet effective and remarkable, procedure is devised to incorporate the existence of discontinuities such as the Heaviside unit function in the construction of inverse transforms by the Stehfest algorithm. This generic method may be used to overcome difficulties in handling changes in flow rate in well-test-analysis applications.

Example applications are presented to demonstrate the viability of our algorithm. Significant savings in storage and CPU time should accrue when this method is used to compute commingled-reservoir responses. We demonstrate the application of this method to situations where layers (or perforations) are added during a test. This completion scheme has come into vogue recently and no simple procedures are currently available to compute well responses.
Improved Measurement Quality and Reliability in a Formation-Evaluation LWD System
Authors: Moake G. L. , Heysse D. R. , Jackson C. E. , Jerabek Al , Merchant G. A. , Schultz W. E.
Published: December 2007

This paper describes a new logging-while-drilling (LWD) tool-string, which is equivalent to a wireline triple-combo. It is composed of two tools, resistivity and nuclear, that can be combined or run separately. New features have been incorporated in the tool designs to minimize problems encountered with previous tools, and to reliably provide near-wireline-quality measurements. The resistivity tool provides symmetrical measurements of both phase and attenuation resistivity for two different transmitter spacings. This provides enough information to determine Rt, as well as to quantify invasion. The symmetrical design provides borehole compensation and ensures that the actual measure point of the tool is the same for all formations. The nuclear tool measures density, Pe, neutron porosity, standoff, and borehole diameter (caliper). The standoff measurement is used to improve the nuclear-data quality by weighting small-standoff data greater than large-standoff data. It is also used to correct the neutron porosity for standoff and borehole diameter. Logs comparing this toolstring to wireline tools are presented.
International Offshore Leasing Practices
Authors: Kaufmann Alvin
Published: December 2007

In formulating their leasing practices, some countries are interested in maximum government revenue, others in maintaining low prices, still others in the industrial spill-overs resulting from the development of a natural resource. As a consequence of these varied goals, the regulations differ greatly from country to country.

Introduction

Governmental leasing practices are designed to achieve optimum resource development consonant with the goals of a particular country, and to provide the resource owners with a share of the income. In most countries, these practices are the same offshore and on, the major exception being the U. S. Some countries are interested in maximum governmental revenue, others in maintaining low prices, and still others in the industrial spill-overs resulting from the development of a natural resource. As a consequence of these varied goals, the regulations may differ greatly from country to country. Most of the nations of the world have coastlines with attendant offshore areas available for development. To summarize the regulations for all of these countries would be an extremely complex and, in some ways, useless task. Many of the nations have no offshore production, and thus their regulations have no real impact except perhaps negatively. Some countries have detailed petroleum legislation, others have none. In both cases, most petroleum exploration and exploitation privileges given to companies in recent years have been let after negotiation or competitive bidding. Sometimes the contract bears little resemblance to the regulations, and in such cases we have used the latest agreement available to us. For the sake of simplicity only those countries will be studied that are major offshore producers, or whose regulations illustrate a system. It should be noted that in considering the regulations we have made no judgment about what constitutes an offshore area. In all cases we have accepted, as a matter of convenience, the definition of the nation concerned. Thus, in the case of Venezuela, Lake Maracaibo would be classified as an offshore area. Offshore regulations have been discussed in some detail in a recent publication,* and so win not be repeated here. The pertinent details of regulations and contracts have been summarized in Tables 1A and 1B. These summaries are by no means definitive; they set forth only the broad outline of the individual country's regulations, or contractual agreements. The latter will vary from agreement to agreement, but we have tried to arrive at a common denominator within each country.

The United States

The Federal system (Table 1A) in the U. S. and that used by the individual coastal states are quite similar. The major differences are in magnitude rather than type. For example, all use a competitive bonus bidding system, and all have a royalty on production. The royalty varies from a low of 5 percent on discovery leases in Alaska to a high of 50 percent in the California sliding scale system.

JPT

P. 247
Oriented Perforation to Prevent Casing Collapse for Highly Inclined Wells
Authors: Morita Nobuo , McLeod Harry
Published: December 2007

This paper shows that the oriented-perforation technique is an effective method to control casing collapse problems for highly inclined wells. Three wells were perforated with 180° phasing in the maximum in-situ stress direction. These three wells did not experience casing collapse, while surrounding wells with the standard perforation technique did. Two of the three wells with oriented perforations experienced significantly reduced sand problems. Numerical analysis was conducted to compare how effective oriented perforations were in minimizing casing failure when a sheared zone was created around a well during drilling and production.
Completion and Workover of Horizontal and Extended-Reach Wells in the Statfjord Field
Authors: Kostøl Petter , Østvang Knut
Published: December 2007

This paper gives a short introduction to the Statfjord field and background for extended-reach-drilled (ERD) and horizontal wells. We reviewed experiences with completion and workovers of horizontal and ERD wells on Statfjord. Ten horizontal wells with horizontal sections of up to 2150 m and four ERD wells with a horizontal reach of up to 7290 m were completed. Several wells were recompleted, and we performed interventions for logging purposes. We describe the development of the completion and workover techniques since the first horizontal well was drilled in 1990 to April 1994.
Oilwell Deliverability Monitoring: A Case History
Authors: Thrasher T. S. , Fetkovich E. J. , Scott S. L.
Published: December 2007

This paper presents a case history study that demonstrates a method to monitor wellhead-deliverability performance for flowing oil wells in a manner similar to gas wells. Separator test data measured for production allocation are used along with the material-balance relationship and multiphase-flow analysis to develop a wellhead backpressure curve for flowing oil wells. An equivalent wellhead static pressure for flowing oil wells is described and shown to be a function of reservoir depletion and multiphase-flow rate. Determination of the equivalent wellhead static pressure extends our understanding of wellhead backpressure analysis for both flowing oil and gas wells.

A case history example demonstrating the application of the methods described in the paper is developed with the separator test data from Point Arguello field wells. The resulting wellhead backpressure curves clearly defined individual well deliverability and proved to be valuable diagnostic tools to monitor well performance and to quantify production potential. We show that the procedures developed in this paper are directly equivalent to procedures applied to conventional gaswell wellhead backpressure analysis commonly used in the industry to monitor gaswell performance. By monitoring flowing oilwell performance with the methods described in this paper, operators can address the challenge of maintaining well productivity and field production plateau.
Analysis of Buildup Curves Obtained After Well Treatment
Authors: van Everdingen A.F. , Meyer L. Joffre
Published: December 2007

Two new unit functions, based on the continuity equation of unsteady-state flow of slightly compressible fluids in permeable media, give the pressure decrease in a well produced at unit rate after its effective radius has been considerably enlarged by acidizing or when the wellbore is intersected by an induced, vertical fracture.

Introduction

Many papers have appeared that contain detailed analyses of the pressure data in wells from the moment the well is shut in until such data form the straight-line relationship, described by Horner,1 between pressure increases and the log of ?t/(t+?t). When formations are not very permeable, it may take some time to gather sufficient pressure data. Attempts have been made to limit the duration of buildup tests and to extract information on the characteristics of the formation and the efficiency of well completion from data recorded in the first hours of the shut-in period. Details are well presented in Refs. 2 and 3, which also contain an extensive bibliography of articles of interest.

The relation between pressure and time is a function of the producing rates and the characteristics of the formation and its fluid content, which can cover a considerable range as shown by the following data. Depending on the formation, the permeability, k, can have a value anywhere between 1 and 1,000 md; the porosity, f, varies from 5 to 35 percent; the fluids can have a viscosity, µ, between 0.02 for gas and 5 cp for oil. The compressibility, c, can be somewhere between 5×10−1 atm−1 for undersaturated fluids and 10−2 atm−1 for gas, whereas the hole diameter can be as small as 4 in. and as large as 10 in. (radius, rw, 5 to 12.5 cm). To simplify computational work, these units were combined into dimensionless groups in Ref. 4 so that only a few fundamental curves are required to analyze flow problems in wells and reservoirs. The following conversion factors are used in these analyses.

Dimensionless time:Equation 1

Dimensionless rate:Equation 2

Dimensionless cumulative production:Equation 3

As it is difficult to measure, with any precision, pressure increases occurring in less than 1 minute after shut-in, 1 minute is about the shortest time interval to be considered. The following table gives the values assigned to the factors in Eq. 1; they convert 60 seconds to 62 dimensionless time units.k=0.001 darcyt=60 secondsf=0.12µ=0.02 cpc=0.005 atm−1rw=9 cm
Design and Installation of an Ultra Deepwater Subsea System: How To Minimize Risks and Costs
Authors: Izetti R.G. , Moreira J.R.F.
Published: December 2007

The world's deepest Subsea Tree was successfully installed offshore Brazilat a water depth of 1027m. The "psychological" barrier of 1000m was fmally broken.

Actually, subsea completion technology reached a point where the fundamental question is no longer whether fields located at water depths beyond 1000m can be profitably completed. The key issue now is: is there a better and safer way to do it?

PETROBRAS has pursued an aggressive strategy m research and development concept evaluations and various field studies aiming at a continuous decrease in both CAPEX and OPEX.

This paper primarily describes the major subsea completion achievements, resulting from this great effort, which among other topics include:implementation of an standardization program; sharp reduction of both subseacompletion and drilling time; a new flowline connection method which combines the advantages of both lay-away and pull-in methods; design and future installation of the world first subsea electrical submersible pump; completion equipment simplification and resulting cost reduction.

Also addressed are the key safety aspects related to deepwater completions and the equipment design improvement necessary to safely conduct those operations.

Introduction

Since its first Subsea Tree installation in June, 1979 on the RJS-3 8 well in 189m (620ft) water depth, PETROBRAS has been overcoming challenges towards deeper waters, basically motivated by its necessity of producing in increasingly water depths, where the latest important giant oil fields were discovered. Although presently only 22.5% (160000 bpd) of the production comes from wells that are located deeper than 400m, this figure is expected to reach61% by the year 2003.

Since that first one up to now, 219 Subsea Trees have already been installed, breaking some remarkable barriers.

In September, 1984 the first diverless Subsea Tree was run on the Pirauna-02well at 307m (1007ft) water depth, breaking the divers operational limits.
Calculation of Pressure-Temperature Phase Envelopes of Multicomponent Systems
Authors: Kalippan C.S. , Rowe Allen M.
Published: December 2007

K-factor data for hydrocarbon systems have been correlated as a function of temperature, pressure and convergence pressure. Recently, a very precise technique was developed to predict precise technique was developed to predict accurate convergence pressures, even in the area of the critical state. It is the object of this paper to demonstrate bow this convergence pressure paper to demonstrate bow this convergence pressure calculation can be used to determine the p-T envelopes of multicomponent systems, including the retrograde region.

Introduction

The petroleum engineer is interested in the p-T envelope that describes the fluid existing in a given reservoir. If the reservoir temperature and pressure are sufficiently high, relative to this pressure are sufficiently high, relative to this phase envelope, it may be economically feasible phase envelope, it may be economically feasible to miscibly displace the reservoir fluid with a drier, less expensive gas (Fig. 1). These phase envelopes are normally established by laboratory measurements involving expensive PVT equipment. By the use of a computer program that utilizes some of the latest correlations of hydrocarbon property data, these envelopes can be generated property data, these envelopes can be generated in seconds from composition analysis data including the molecular weight of the C7+ fraction. It is the purpose of this paper to show how convergence pressures can be used to predict be p-T envelopes of multicomponent systems. p-T envelopes of multicomponent systems. Convergence pressure is shown to be a phase-rule variable for the two-phase, three-component system at equilibrium. Ternary phase diagrams are presented for three-component systems that define the convergence pressure for a given temperature pressure, and system composition.

PREDICTION OF THE PREDICTION OF THE PRESSURE-TEMPERATURE ENVELOPE OF A PRESSURE-TEMPERATURE ENVELOPE OF A TWO-COMPONENT SYSTEM

The data for the two-component system will be used to demonstrate how convergence pressure calculations can be used to predict p-T envelopes for multicomponent systems. Figs. 2 and 3 show experimental p-T-Z data for a system such as the ethane-heptane system. (p-Z)T = C1 data has been used to establish convergence pressure K-factor correlations such as those published in the 1957 NGSMA Data Book. These K-factors are plotted as functions of T, p, p cv. plotted as functions of T, p, p cv. These data, in turn, can be used to predict the (p-T)Z = C1 envelope. Suppose we wish to calculate the p-T envelope of Mixture Z of Fig. 3. To use the convergence pressure correlations to establish such a p-T envelope, the following three methods (A, B and C) were developed to predict dewpoint and/or bubble-point states. The predict dewpoint and/or bubble-point states. The method depends on whether the temperature was equal to, greater, or less than the critical temperature.

SPEJ

P. 243
Well Construction Team Approach Creates a New Future for One Company's Operations on the Dutch Continental Shelf
Authors: Stringer R.B. , Bakker T.W.
Published: December 2007

Rising costs and low energy prices were inhibiting the development of marginal fields on the Dutch Continental Shelf, resulting in a reduction in drilling activity and a loss of business opportunities. Independent benchmark surveys and critical analysis of total well costs showed the potential for major cost reductions that could turn many of the smaller offshore gas finds into economic development prospects. This triggered a change from traditional operating and contracting strategies to a partnering approach with the principal drilling and service contractors and the institution of a well-construction team (WCT). The WCT proved so successful, with an average well cost reduction of 21% in the first year, that a similar organization has been set up for all the land drilling and workover operations. This paper describes the strategies used and presents a comparison between the traditional performance and the results from the first year of operating as a WCT. The comparison includes the results of an independent benchmark study of 20 North Sea operating companies.

Introduction

The operator's Well Engineering Dept. delivered 22 offshore wells of various types during 1992 at a cost of $260 million. Subsequent remedial work with associated production deferment cost a further $60 million, giving a total cost to the operator of $320 million. Although this was considered to be representative of the general industry performance on the Dutch Continental Shelf, these cost levels made many of the smaller gas finds subeconomic development prospects. This resulted in a reduction in activity from five rigs in 1992 to two rigs in 1993. Further reductions in drilling activity were likely in the following months unless major cost savings could be realized. The prospect of minimal activity threatened both the contractors' survival and the continuation of the operator's offshore activities. These threats dictated a need for a radical change in strategy.

The following options for achieving this change were considered by the operator:terminating the current contracts and retendering in order to obtain lower rates oraggressively pursuing improvements in all elements of the well-construction process while retaining the existing contracts.

The latter option was selected as the only sure way of delivering the "best -value" wells to the operator while providing the contractors with the profit margins necessary to sustain and improve their business into the future. This decision was supported by an analysis of the 1992 well costs, which indicated that, in an ideal world, the total costs could be halved by a combination of optimization of well design and working practices, the development and application of new technology, and avoiding workovers through improved quality.
Capillary Trapping Mechanisms in Water-Wet Laminated Rocks
Authors: Huang Yaduo , Ringrose P. S. , Sorbie K. S.
Published: December 2007

Most flooding experiments in sandstone cores are carried out either in almost homogeneous samples or in core samples of uncertain heterogeneity. As a result, the interaction of small-scale sedimentary heterogeneity with the fluid mechanics of water-oil displacement cannot be adequately understood or quantified. Because most clastic sediments show some degree of lamination, this might be expected to have a significant influence on both oil displacement efficiency and residual/remaining oil saturation.

This paper reports results from low-rate, drainage/imbibition floods in a 20 × 10 × 1- cm water-wet slab of cross-laminated heterogeneous eolian sandstone. The distribution of porosity, permeability, initial water saturation and residual oil saturation were monitored with computerized-tomography (CT) scanning techniques. The low-rate imbibition floods show that between 30% and 55% of original oil may be trapped in isolated high-permeability lamina. This work shows the importance of recognizing the role of core-scale heterogeneity in the laboratory measurement of waterflood behavior (i.e., the interaction of capillary forces with rock structure, particularly lamination). The practice of performing high-rate floods on rock samples assumed to be homogeneous is unwise and can lead to erroneous conclusions. The results of this work have major implications for (1) two-phase petrophysical measurements; (2) assessment of residual/remaining oil, and (3) multi phase-flow scaleup.
Mechanical Treatment of Weighted Drilling Muds
Authors: Bobo Roy A. , Hoch R.S.
Published: December 2007

Maintenance of desirable plastic flow properties of weighted drilling muds may be greatly simplified by use of centrifugal classification to control the drilled solids content. The new application of a decanting type centrifuge to separate and reject the low density solids from the weighting material results in a drilling mud of greatly improved quality with lower values of yield and rigidity.

Its practicality and economy has been proven in field operation. The degree of separation of light and heavy solids is not limited by the machine, but by the particle size distribution of the solids in the mud. Removal of the low density component of drilling mud that makes chemical treatment necessary permits a marked reduction in chemicals.

The main uses of the centrifugal process are the treatment of muds while drilling, the reclaiming of discarded muds, cleaning up of workover muds, and the reduction in lime content of mud for completion.

Introduction

Drilling mud in any circulatory system is made viscous and difficult to pump by gradual accumulation of drilled solids which pass through the shale shaker and are continually reground. In a weighted mud containing a large proportion of barite by volume, the amount of drilled solids that may be tolerated is greatly reduced. Much effort has been expended to control by chemical treatment the effects of such solids. Though chemical treatment is quite effective, the time eventually comes at deeper depths after enough drilled solids nave entered the system when a portion of the mud must be discarded and replaced with water and more weighting material. Once begun, this process is generally continued at frequent intervals with resultant high maintenance costs.
A New Method for Representing Multiple Wells With Arbitrary Rates in Numerical Reservoir Simulation
Authors: Peaceman Donald W.
Published: December 2007

A new equation is presented for calculating the equivalent wellblock radii, req, for all nw wells in a reservoir that fully accounts for arbitrary well rates and the interaction between wells. The data required for the new equation may be obtained in a preprocessor by calculating nw single-phase pressure distributions. Then, an accurate req can be calculated for each well at each timestep, even under conditions where well rates vary with time.
Shale Oil Recovery by In-Situ Retorting-A Pilot Study
Authors: Burwell E.L. , Sterner T.E. , Carpenter H.C.
Published: December 2007

Results of this in-situ combustion experiment, conducted by the U. S. Bureau of Mines near Rock Springs, Wyoming, to produce shale oil from oil shale, indicate that a combustion zone can be established in a fractured oil shale body by using air injection and a propane burner. During the six-week period that combustion was maintained, 8,000 gallons of oil was produced. produced. Introduction

This paper describes an in-situ combustion experiment conducted by the U. S. Bureau of Mines in the Green River oil shale formation near Rock Springs, Wyo. The experiment was designed to study the engineering problems associated with the establishment, maintenance, and control of a self-sustaining combustion zone in the oil shale and the use of this process to produce shale oil. A 20-ft-thick section of the oil shale located from 68 to 88 ft below the surface of the ground was ignited by use of a propane burner in the central well of an expanded five-spot development pattern. A combustion zone was established in the formation and maintained with little difficulty for a 6-week period, at the end of which time air injection and the combustion phase of the project weld terminated. Several thousand phase of the project weld terminated. Several thousand gallons of shale oil were recovered and stored for analysis. Permeability loss at the injection well and high viscosity of shale oil were problems experienced by other investigators during oil shale retorting, but were not encountered during this test.

Geology

The combustion experiment was performed in the Tipton member of the Green River oil shale formation near Rock Springs, Wyo. The Tipton member in the area of the test-site has a 2-percent dip to the west and a general geologic strike to the north, Green River oil shale is a dolomitic marlstone with a finely laminated structure consisting of an intimate mixture of organic and inorganic materials. The mineral portion ranges from 92 weight percent of shales having an oil yield (as determined by Fischer assay) of 10 gal/ton to 60 weight percent of those having a yield of 75 gal/ton. It consists largely of dolomite, calcite, feldspars, quartz, and illite clay. In the leaner shales cementation is primarily inorganic; however in rich strata it appears that the organic material is the principal cementing agent principal cementing agent Both the porosity and the permeability of oil shale are extremely low because the solid, essentially insoluble organic material serving as a cementing agent blocks the major portion of any pores that might be present. present. Site Preparation

Since the success of any in-situ combustion oil recovery experiment in oil shale depends directly on the ability of air, combustion gases, and produced oil to move through the shale formation, produced oil to move through the shale formation, the first part of the site preparation consisted of an intensive fracturing program. Fracturing techniques that were investigated included electrolinking, hydraulic fracturing, and explosive fracturing.

P. 1520
Identification of Parameters Influencing the Response of Gas Storage Wells to Hydraulic Fracturing With the Aid of a Neural Network
Authors: McVey D. S. , Mohaghegh Shahab , Aminian Khashayar , Ameri Samuel
Published: December 2007

Performing hydraulic fractures on gas storage wells to improve their deliverability is a common practice in the eastern part of the U.S. Most fields used for storage in this region are old, and the reservoir characteristic data necessary for most reservoir studies and hydraulic fracture design and evaluation are scarce. This paper introduces a new method by which parameters that influence the response of gas storage wells to hydraulic fracturing may be identified in the absence of sufficient reservoir data. Control and manipulation of these parameters, once identified correctly, could enhance the outcome of frac jobs in gas storage fields. We conducted the study on a gas storage field in the Clinton formation of northeastern Ohio. We found that well-performance indicators before a hydraulic fracture play an important role in how good the well will respond to a new frac job. We also identified several other important factors.

The identification of controlling parameters serves as a foundation for improved frac job design in the fields where adequate engineering data are not available. Another application of this type of study could be the enhancement of selection criteria among the candidate wells for hydraulic fracturing. To achieve the objective of this study, we designed, trained, and applied an artificial neural network. The paper will discuss the results of the incorporation of this new technology in hydraulic fracture design and evaluation.
Allocation of Costs Between Petroleum Liquids and Gases
Authors: Hunter E.E.
Published: December 2007

Introduction

Petroleum producers have been engaged for many years in supplying several different types of materials from the leases they operate. Some leases produce crude oil and casing-head gas, others produce gas-well gas and condensate, and still others produce all four of these materials. Therefore, the problem of allocating costs between these intermingled products is not a new one.

While in some fields gas has been the dominant product, most producers have been interested principally in oil. Consequently, little has been done about the cost allocation problem by oil producing companies. For accounting purposes, these companies have generally considered gas a by-product, and whatever realization was obtained from it was accounted for as a reduction of producing costs, which were all considered to be applicable to crude oil. The inadequacy of this procedure under present day conditions, and the need for a more realistic approach to the problem of accounting for costs, can probably be illustrated best by a brief review of the growing importance of gas in the economic structure of the industry.

Need for Allocation

Known natural gas reserves in the United States approximately doubled during the 10 years ending with 1952, rising to a total of nearly 200 trillion cu ft at the beginning of 1953. In terms of heat value the 200 trillion cu ft of gas is approximately equal to the combined heat content of the 28 billion bbls of crude oil and the 5 billion bbls of condensate in reserve at the beginning of 1953. However, the heat units produced in the form of oil in 1952 were almost twice as great as those produced in the form of gas - a good indication that there is much more room for expansion in production of gas than for crude oil.

The rapid growth in demand for gas since the end of World War II has brought about a substantial increase in the wellhead price, despite increasing reserves. In the Southwest, for instance, the price doubled in the period from 1943 to 1951, rising to an average of approximately 5.6 cents a thousand in the latter year. Marketed production of gas in the United States had increased to a rate of about 7.5 trillion cu ft in 1951 and over 8 trillion in 1952. The increase in demand thus indicated has been close to 12 per cent a year since 1946, more than twice as great as the rate of increase in demand for crude oil.
Analytical Solution of the Tracer Equation for the Homogeneous Five-Spot Problem
Authors: Almeida A. R. , Cotta R. M.
Published: December 2007

The Generalized Integral Transform Technique (GITT) has been successfully employed in various heat and fluid flow problems. This paper describes the first application of the GITT in petroleum reservoir simulation problems.

The two-dimensional tracer equation for the five-spot pattern is solved analytically by means of this approach, with the usual assumptions of steady-state single-phase flow and unit mobility ratio. The solution is compared, in a wide range of situations, with alternative analytical (when possible) or numerical (finite differences) solutions, as well as with experimental data from other sources.
Liquid Fuels From Oil Shale - A Critical Review
Authors: Rubel A.C.
Published: December 2007

Shale deposits of northwestern Colorado contain more than 100 billion barrels of recoverable shale oil from which, by processes now developed, high quality liquid fuels, gas, sulfur, ammonia, and petrochemical products may be produced.

Experience during the past two years indicates that in the immediate future we face an increasing dependence upon crude supplies outside of the United States.

Studies conducted by the National Petroleum Council indicate that a considerable proportion of this shale oil may be recovered and processed into products equal to those from natural crudes on the Pacific Coast at a cost closely approaching current prices from natural crude.

It would therefore seem to be in the public interest for the petroleum industry and the Defense Department to thoroughly explore the possibilities of developing this great resource as a supplement to our domestic crude supply.

Immediate industry study on an expanded pilot plant scale is suggested.

Introduction

Probably the greatest concentration of potential energy to be found any place in the world lies in the oil shale deposits of the Green River Formation in northwestern Colorado. Those deposits are capable of producing billions of barrels of high quality liquid fuels, as well as large quantities of ammonia, sulfur, coke and fuel gas.

There is a definite need to provide a larger available and dependable reserve of liquid fuel within our own territorial limits to augment our domestic production and, in case of war, enable us to be independent of imports if they are denied us by enemy action.

It would therefore seem to be prudent and sensible for both the oil industry and the Defense Department to take a very careful look at this vast resource.

The history of oil from shale is old. Liquid fuels from this source have been produced in Europe, particularly Scotland, for over a century. Because of the high cost of production, it has attracted little attention in the United States, although immediately following World War I rapidly declining reserves directed the attention if the U. S. Bureau of Mines and several companies to oil shale as a potential source of liquid fuels.
Drillstring Component Mass Imbalance: A Major Source of Downhole Vibrations
Authors: Dykstra M. W. , Chen D. C-K. , Warren T. M. , Azar J. J.
Published: December 2007

A study consisting of surface and downhole field experiments, theoretical analysis, and numerical modeling has shown that mass imbalance of drillstring components is a major source of downhole lateral vibrations. Factors that contribute to imbalance include bore misalignment, initial curvature, and gradual wear during service. Field experiments were conducted on the surface to quantify drill-string component mass imbalance for modeling purposes. Tests focused on drill collars. Lateral displacements of collars were measured while each was rotated in the derrick, and results were interpreted with simple models. All collars were unbalanced to some extent. A similar procedure can be used in the field to identify nearly balanced collars for use near the bit. Field experiments conducted downhole used a bull nose in place of a bit to evaluate drill-string vibrations without the bit as a source. A pendulum assembly with stabilizers 65 and 95 ft from the bull nose was used. Simultaneous surface and downhole measurements of accelerations were made. Lateral shocks caused by collar/wellbore collisions were measured at various locations in the drillstring at rotary speeds that caused the collars to whirl. Acceleration magnitudes were heavily influenced by local formation strength. Backward whirl of the drill-string was observed while rotating both on and off bottom. It was identified through downhole measurements, and was associated with sudden, dramatic increases in surface torque.
Simple Procedures for Imposing Constraints for Nonlinear Least Squares Optimization
Authors: Carvalho R. , Thompson L. G. , Redner R. , Reynolds A. C.
Published: December 2007

Nonlinear regression methods (least squares, least absolute value, etc.) have gained acceptance as practical technology for analyzing well-test pressure data. Even for relatively simple problems, however, commonly used algorithms sometimes converge to nonfeasible parameter estimates (e.g., negative permeabilities) resulting in a failure of the method. To avoid this problem, the optimization method must be constrained. Several methods for constrained optimization exist, but nonlinear least squares with penally functions used to impose constraints is usually the algorithm of choice for pressure transient analysis problems. With some experience, penalty functions can be used effectively, but their use requires the user to determine the weighting given the penalty function. Moreover, if initial estimates are far from the solution, non-physical estimates of the parameters may still be obtained.

The primary objective of this work is to present a new method for imaging the objective function across all boundaries imposed to satisfy physical constraints on the parameters. The algorithm is extremely simple and reliable. The method uses an equivalent unconstrained objective function to impose the physical constraints required in the original problem. Thus, it can be used with standard unconstrained least squares software without reprogramming and provides a viable alternative to penalty functions for imposing constraints when estimating well and reservoir parameters from pressure transient data.

In this work, we also present two methods of implementing the penalty function approach for imposing parameter constraints in a general unconstrained least squares algorithm. Based on our experience, the new imaging method always converges to a feasible solution in less time than the penalty function methods.
Permeability Continuity of Laminae in the Calvin Sandstone
Authors: Robertson R.W. , Caudle B.H.
Published: December 2007

Laboratory tests that were conducted to determine the continuity of laminae in a sandstone outcrop in Oklahoma revealed that such laminae would probably have adverse effects on miscible displacement operations in a sandstone reservoir.

Introduction

The existence of thin, horizontal strata in sandstone rocks has long been recognized by geologists. These same permeable layers of consolidated sand grains have recently been identified in sandstones that appeared outwardly to be homogeneous. The existence of the microstrata seems to be accepted even though a detailed study of their areal extent has not been attempted. One reason for this neglect may be that the thin strata have in the past been considered relatively insignificant in relation to the larger strata in the formation. It is now thought, however, that these thin layers may be very important in the way they affect some of the processes used to recover petroleum from the sandstone reservoir. Holden and petroleum from the sandstone reservoir. Holden and Sprinkle found the laminae to exist in several water-deposited sandstone formations along the Gulf Coast and inland to Oklahoma. The laminae examined by Holden and Sprinkle were found to differ radically in permeability, with adjacent ones having ratios as high permeability, with adjacent ones having ratios as high as 10:1. If the laminae are continuous over a long distance, the extreme permeability differences would most probably affect the recovery of petroleum obtained probably affect the recovery of petroleum obtained by the replacement of one fluid with another. This would include miscible secondary recovery operations and also primary operations in which the energy source is solution gas drive. Holden, in his investigation, found the laminae to exist in the Calvin sandstone of Oklahoma. The Calvin is a highly permeable, well consolidated sandstone, and because of this, we selected it for this study of the continuity of microstrata. The laminae in question are about 1 mm and larger in thickness. A Calvin sandstone thin-section is shown in Fig. 1, which indicates the relative dimensions involved. Dye was injected into the sample before the thin-section was taken.

JPT

P. 661