bluuebunny/crossref_metadata_2025 huggingface dataset:
Mathematical Simulation of Natural Gas Condensation Processess Using the Peng-Robinson Equation of State
Authors: Nagy Zoltán , Shirkovskiy Arkadiy I.
Published: December 2007

On the basis of its simplicity and the data obtained by a great number of tests and comparative analysis, we consider the Peng-Robinson (PR) equation of state to be the most suitable to calculate the condensation processes of natural gas, further on to set up the equations of material and heat balances.

In case of mixtures, the accuracy of the PR equation of state was mainly influenced by the correct selection of the interaction coefficients.

The paper presents the calculation correlations of the thermal and thermodynamic properties published uncompletely before, as expressed with the parameters of the PR equation of state.

The simulation of natural gas processes could be made more robust by introducing new differential characteristics. Such is the partial derivative of temperature change owing to pressure change (∂T/∂P), that can be effectively used to calculate expansion and compression processes to reduce the number of iteration steps. This term has been calculated using the derivatives (∂Z/∂T)p which can easily be determined from the PR equation of state.

Using the experiences obtained by the application of the PENG-ROBINSON AGA PROGRAM we have developed a module for calculation of phase equilibria and thermodynamic properties of fluid systems. This is the main module of our program MODEL-TECH (constructed in module structure) which is suitable to calculate separators, heat-exchangers, heat sources, heat drains, Joule-Thomson effect, expansion turbines, compressors, detander-compressor units, arbitrary columns and simulation processes of any degree of complexity built from the above elements.
Offshore Exploitation of Refrigerated Natural Gas Liquids
Authors: Castel Elisabeth J. , Baggio Jean-Louis
Published: December 2007

Producing refrigerated Natural Gas liquids will improve offshore associated Gas recovery.

The following system includes production, storage and loading of Natural Gaz liquids cooled down to atmospheric pressure.

Natural Gaz liquids are cooled down using a NGL refrigerant cycle and stored in floating or gravity concrete membrane tanks. Loading is carried out using a distant loading terminal with separate mooring and loading devices. The whole system was designed to meet requirements for safety, easy maintenance and use of existing technology. Detailed engineering of the elements was performed including process calculation, structural analysis and risk analysis.

An application of the system will be presented and an appraisal of its cost given.
Deconvolution With Propagated Geometric Factors
Authors: Thadani Suresh G. , Merchant Givlamabbas A.
Published: December 2007

The deconvolution process is basic to the improvement of the thin bed response of induction logging tools. Past approaches to this problem (Smith, Bostick 1964) have focussed on the design of inverse filters based on the Doll Geometric factor (Doll 1949). As is well known, the Doll Geometric factor does not accurately model the response of the induction tool particularly in formations with conductivities greater than 1 mho/meter. Recently (Thadani, Hall 1981), new techniques based on the solution of Maxwell's equations have been developed that permit the computation of propagated geometric factors i.e. geometric factors that fully incorporate propagation effects. These techniques make it possible to accurately compute the vertical investigation characteristic or response function of the induction tool in a large class of cylindrically symmetric formation geometries, including the thin invaded bed formation model.

In this paper, it is shown by the application of the above techniques that the response function of the induction tool is a function of both the formation parameters and the relative position of the tool with respect to the formation. In particular, it is shown that the shape of the response function becomes asymmetric with respect to the center of the tool as the conductivity of the formation increases. Synthetic data computed by using the above techniques is used to evaluate the performance of inverse filters based on the Doll Geometric factor for various formation geometries including the thin bed formation model. Currently, various deconvolution filters are being developed using response functions based on propagated geometric factors. The paper will include the results of an evaluation of these filters on various cylindrically symmetric formation geometries.
Petroleum Industry Technical Manpower Requirements for the Next Decade
Authors: Early P. J.
Published: December 2007

It is a pleasure to take part in this SPE session on Resource Management in a Changing Environment. My topic -- Manpower -- has recently been a serious problem for our industry. Thus, it is appropriate that your Program Committee included this discussion of technical manpower requirements over the next decade.

You have already heard forecasts on energy supply and demand, future capital requirements, and the technological direction our industry will take. These interrelated subjects also will influence future manpower requirements, but I will try to avoid ground already covered.

This dynamic interplay makes forecasting difficult, and I do not intend to make specific, year-by-year predictions about personnel needs.
Dependence of Residual Nonwetting Liquid on Pore Topology
Authors: Pathak Prabodh , Davis H. Ted , Scriven L. E.
Published: December 2007

Fluid distributions and flow through the pore-space of reservoir rock depend not only on pore sizes and shapes but also local pore connectivity. This can be characterized in terms of the network concept of coordination but is more appropriately described by the topological invariant called genus, which is the basic measure of the multiplicity of paths through the pore network. The larger the genus per unit volume, the larger the number of alternative paths available for fluid connection and flow. Genus is the number of distinct holes in a holey structure such as porous rock.

Model rocks of a series of pore structures were prepared by controlled sintering of model sediments of three different grain shapes and two grain sizes. The morphology of each core was found by serial sectioning and recording all the relevant dimensions and connections. From features on representative two-dimensional sections the statistics of genus and other relevant properties of the three-dimensional structures were calculated by means of mathematical relations known for random structures.

Resxdual saturat ions when oil was displaced by water, and vice versa, were measured in each core before it was sectioned. The experiments were made at low capillary numbers, and by the Penn State method.

The measured residual saturations of nonwetting liquid in model rocks synthesized from grains of the same size but different shapes correlate re-markably well with genus per unit volume. Pore topology, heretofore unstudied, is as crucial as pore geometry in determining residual nonwetting saturations* The higher the genus, the more alternate routes are available for oil drainage, the larger the average number of choke-off and break-off events it takes to isolate blobs of oil, and so the lower the residual saturation.
Interpretation of Interference Tests in Reservoirs With Double Porosity Behavior—Theory and Field Examples
Authors: Deruyck Bruno G. , Bourdet Dominique P. , DaPrat Giovanni , Ramey Henry J.
Published: December 2007

A systematic approach for analyzing interference tests in reservoirs with double porosity behavior is presented; it applies to both naturally fractured reservoirs and multilayered reservoirs with sufficiently high permeability contrast between layers.

Type curves are presented for the pressure response at an observation well, the active well being produced at either constant flow rate or constant pressure.

They are derived from two models with the assumptions of pseudo-steady state or transient interporosity flow regime. The distinctive specific features they exhibit are clearly identified and quantitatively related to the model parameters.

An interpretation method, based on type curve matching, is proposed: after selection of the most appropriate model, and identification of the successive flow regimes, the double porosity behavior of the reservoir is characterized and pertinent parameters are evaluated: flow conductivity kh, interporosity flow parameter λ, and storativity (ϕVct)h segregation throughout the reservoir.

Actual field examples are discussed to illustrate the method.
Clay Models and Acoustic Velocities
Authors: Minear John W.
Published: December 2007

Acoustic velocity, or porosity derived from the velocity, are often corrected for shale or clay effects. These corrections are largely empirical. Two-phase porous media models are applicable to sedimentary formations and provide a new approach to estimating the effects of shale and clay on clean formations. One particular model is used to calculate the effects of laminated and structural shale and dispersed clay on compressional and shear wave slowness. The calculations suggest that laminated and structural shale have about the same effect. Dispersed clay may have negligible effect. Shale and clay increase shear wave slowness more than compressional wave slowness.
Causes and Prevention of Vibration Induced Failures in Submergible Oilwell Pumping Equipment
Authors: Brinner T. R. , Traylor F. T. , Stewart R. E.
Published: December 2007

Vibration phenomena in Electric Submergible Pumping Systems is rarely identified as the cause of premature system failure. This is the result of a number of factors. The first is a lack of sensed and recorded downhole operational parameters pertinent to the mechanical condition of the machine. The second arises from the practice of attempting restart several times before pulling a failed unit; this procedure has the effect of causing additional damage and thus masking any evidence of vibration. Finally, a vibration induced failure can eventually be manifested in other, more common failure modes which are ultimately credited with causing the event. The point is that failure, regardless of cause, cannot be addressed unless the mode of initiation is understood. This paper suggests that vibration initiated failures, while not frequent, are more prevalent than previously believed. It is also suggested that improvements in reliability will be observed when the phenomena is fully understood and addressed from the equipment design, application, and operation viewpoint. This work describes the vibration problem and the conditions which increase its probability of occurrence. It will also suggest measures to avoid the phenomena, and illustrate this with known field case studies that have been confirmed by experimental laboratory work.
The Geology of the Yellowhouse Unit, Hockley County, Texas
Authors: Long Gregory P.
Published: December 2007

A detailed description of the porosity and permeability trends within the Yellowhouse (San Andres) Unit reservoir was prepared for the Amoco Production Company (USA) Producing Department to aid present and future engineering studies. The waterflood pattern in the western half of the Unit is under consideration for conversion to a 44.25 acre, 5-spot pattern from an 88.5 acre, 5-spot pattern. The geologic study examined the San Andres Formation Zones VIII, IX, and X.

Production within the Unit is from Zone IX. Zones VIII and X were found to be nonproductive. Zones VIII and IX are interpreted to be two shallowing-upward carbonate sequences consisting of (1) subtidal wackestones and burrowed mudstones, (2) intertidal mudstones and algal-1aminated mudstones, and (3) supratidal dolomites and anhydrites. Each of these facies exhibits characteristic porosities and permeabilities. Porosity and permeability data, core descriptions and log response from six cored wells were merged to determine pay quality, zonation and lateral and vertical continuity.

A shelfward decrease in permeability forms the trap in Zone IX. As the subtidal wackestones, in which the porosity and permeability are best developed, grade into the shallower intertidal mudstones, a change in pore type from intercrystalline to moldic is observed. This pore-type change reduces permeability and forms the trap. Additional development potential exists west and south of the Yellowhouse Unit. The data suggests that Zone VIII is tight and nonproductive within the Unit. More core and log data is needed to delineate porosity and permeability trends in Zone X.
Temperature Effects on Relative Permeabilities of Oil-Water Systems
Authors: Sufi Arshad H. , Ramey Henry J. , Brigham William E.
Published: December 2007

Relative permeability is perhaps the most important parameter in describing underground flow behavior of immiscible fluids. In recent years, thermal recovery methods have gained in importance. This requires an understanding of temperature effects on flow characteristics of reservoir fluids.

This paper presents an experimental study dealing with temperature effects on relative permeabilities of oil-water systems. Results indicate that the curves are independent of temperature as are the end point saturations. There is a decrease in "practical" residual oil with temperature saturation due to a change in the shape of the fractional flow curve.
Geothermal Reservoir Testing by Piezometric Surface Drawdown/Buildup
Authors: Bodvarsson Gunnar , Zais Elliot J.
Published: December 2007

The monitoring of a piezometric surface drawdown or buildup provides data that can be interpreted in terms of estimates of reservoir porosity and permeability. In the case of heterogeneous/anisotropic reservoirs such estimates will generally deviate from conventional well testing results. The Laugarnes geothermal field in Southwestern Iceland presents an interesting case where results of both types of test procedures can be compared. Processing and interpreting the piezometric surface data, we find that they lead to estimates of the reservoir permeability of 10 to 50 millidarcy that is orders of magnitude lower than results of conventional well interference testing. The porosity of the reservoir is estimated at 3 × 10-3. This is a plausible value for flood basalts of the rift zone type.
Combined Natural Gamma Ray Spectral/Litho-Density Measurements Applied to Complex Lithologies
Authors: Quirein John A. , Gardner John S. , Watson John T.
Published: December 2007

Well log data has long been used to provide litho-logical descriptions of complex formations. Historically, most of the approaches used have been restrictive because they assumed fixed, known, and distinct lithologies for specified zones. The approach described in this paper attempts to alleviate this restriction by estimating the "probability of a model" for the models suggested as most likely by the reservoir geology. Lithological variables are simultaneously estimated from response equations for each model and combined in accordance with the probability of each respective model.

The initial application of this approach has been the estimation of calcite, quartz, and dolomite in the presence of clays, feldspars, anhydrite, or salt. Estimations were made by using natural gamma ray spectra, photoelectric effect, bulk density, and neutron porosity information.

For each model, response equations and parameter selections are obtained from the thorium vs potassium crossplot and the apparent matrix density vs apparent volumetric photoelectric cross section crossplot. The thorium and potassium response equations are used to estimate the volumes of clay and feldspar. The apparent matrix density and volumetric cross section response equations can then be corrected for the presence of clay and feldspar. A test ensures that the clay correction lies within the limits for the assumed lithology model. If it is not within limits, either the estimate of clay volume or the lithology model, or both, are changed.

Results are presented for varying lithologies. For one test well, 6,000 feet were processed in a single pass, without zoning and without adjusting more than one parameter pick. The program recognized sand, limestone, dolomite, clay, feldspar, anhydrite, and salt without analyst intervention.
Economic Considerations in the Acquisition of Oil and Gas Reserves for Oil Income Programs
Authors: Isaacs V. A. , Doubek R. J.
Published: December 2007

Petro-Lewis has designed a financing format for the acquisition of producing properties. Through this format, individuals can acquire an interest in a Limited Partnership that directly owns the producing properties. For this ownership in the Limited Partnership, the investor receives income derived from the cash flow stream of the producing properties, and liquidity through the General Partner's willingness to buy back this interest on an engineered basis.

This paper will outline the structure which has proved successful in acquiring these properties, as well as describe the evaluation techniques employed, with an analysis of the results which have been achieved during the last ten years.
Expected Returns on Investment in the Giddings, Austin Chalk (Gas) Field
Authors: Reeve Richard P. , Peters Ekwere J.
Published: December 2007

An economic evaluation has been performed to determine the expected returns on investment for a drilling program in the Giddings, Austin Chalk Gas Field. Using projected production schedules of selected well types from the encountered reserve distribution, computer based cashflow analyses were performed under six hypothesized future scenarios of varying hydrocarbon pricing, demand, taxation, and inflation. For the six future scenarios studied, the Giddings Gas Field drilling program was found to produce a positive, after tax net present value, using 15% as a discount factor. Furthermore, the returns on investment were higher for an independent than for a major producer. Our results suggest a drilling program initiated in the near future will prove to be an attractive economic venture.
Experimental Investigation of the Steam Drive Process for the Asphalt Ridge Tar Sands Deposit, Utah
Authors: Watts K. G. , Hutchinson H. L. , Johnson L. A. , Barbour R. V. , Thomas K. P.
Published: December 2007

A series of laboratory experiments was conducted at the University of Wyoming to determine the steamflood recovery mechanisms for the Asphalt Ridge Tar Sands deposit located near Vernal, Utah. Steam at various temperatures and qualities, hot water and also nitrogen were injected into an adiabatic tube containing the tar sands, and the recovery curves were measured. From the results of the experiments, it was concluded that the Asphalt Ridge steamflood mechanisms consist of viscosity reduction, solvent extraction-enrichment, liquid displacement, and steam distillation. In addition to determining the steamflood mechanisms, it was also shown that, for the Asphalt Ridge Tar Sands (1) steam injection recovered more oil than did a hot waterflood at the same temperature (2) thick, viscous oil was produced during low quality steam runs, whereas a lighter oil was produced at higher qualities, and (3) intermediate quality steam will recover more of the original oil in place than will either high quality steam or hot water.
An Analysis of Rate-Sensitive Skin in Oil Wells
Authors: Blacker Laura K.
Published: December 2007

This paper documents the results of the perforating program for the first forty wells in the Kuparuk River Field in Alaska. Several different types of perforating guns were used to perforate the wells at varying shot densities. Pressure transient tests were conducted on each well to measure skin damage and flow efficiency. A correlation of average flow efficiency with perforating gun type and shot density is presented. This shows that shot densities above 4 shots/ft result in less skin damage, and wells completed with 12 shots/ft have little or no damage. The effect of perforation penetration is also shown to be a factor in reducing damage, but with all other factors being equal, 12 shots/ft is shown to result in the least amount of damage.

The above results are explained by a detailed analysis of multiple buildup tests at varying rates which were performed on some of the highly damaged wells completed during the early development of the field. These tests indicated skin damage to be rate sensitive with some true formation damage also present. Non-Darcy flow and gas saturation near the wellbore are shown to contribute to the rate-sensitive skin factors. A method of analysis is presented which allows non-Darcy flow skin factors to be calculated when gas saturation is also causing a skin effect. This can be accomplished without fluid property and relative permeability data, which is necessary to calculate saturation effects using standard analysis methods.
The Development of a General Phase Envelope Construction Algorithm for Reservoir Fluid Studies
Authors: Li Yau-Kun , Nghiem Long X.
Published: December 2007

This paper deals with the development of a general algorithm for phase envelope construction. It extends the pressure-temperature diagram construction method of Michelse1 to the generation of phase envelopes on pressure-composition, temperature-composition and composition-composition diagrams. The bubble point and dew point curves are traced in one pass, and an estimate of the critical point is also given. The loci of mixtures having a constant vapor-liquid split (e.g. 25% vapor mole fraction or volume fraction) can also be generated. The algorithm selects internally the primary variables and the points on the diagram to enhance the convergence.

Results are presented for simple mixtures, typical reservoir oil-CO2 mixtures and a gas condensate. Problems associated with a discontinuity in the phase envelope because of a three-phase region are also presented, and it is shown how an analysis of the Gibbs energy surface can help in discarding unrealistic results.
Financial and Engineering Considerations in Petroleum Property Acquisitions
Authors: Chan S. A.
Published: December 2007

One of the popular methods for a new or growing oil company to quickly build up a reserve base has been to acquire properties through an exchange of the purchaser's stock. While there are definite advantages to both the buyer and seller; in regards to tax treatment of the exchange, in market liquidity for the seller, and in conserving cash of the buyer, there are major considerations that the purchaser should consider, especially from the standpoint of synergistic value added to the purchaser with respect to additional reserves, cash flow, and market value of the purchaser's stock. Numerous companies have attempted to roll oil and gas properties into their reserve asset base through exchanges of stock. In some of these cases, the end result of the exchange has left the purchaser with a larger debt burden, and greater unanticipated capital commitments which end up adversely affecting the purchaser's stock price on the open market.1 There are a number of factors that need to be considered before a petroleum company pursues such a course of action. While the following ideas presented do not represent an all inclusive checklist, sufficient thought and preparation will help to lessen the dangers of the venture.
Norway—The Dilemma of a Small Country Torn Between National and International Energy Interests
Authors: Frognes Gunnar
Published: December 2007

The objective of this paper is to show how petroleum discoveries and an increasingly important continental shelf may conceivably influence the standing of a small nation in the international community.

Norway is a small and remotely located country, traditionally endowed with few natural resources. For years she has enjoyed the privileges of a small state, being of moderate international prominence, inoffensive to neighbouring states and having a sheltered existence within the framework of a military alliance, all factors giving her "freedom from error" and a fair amount of flexibility in foreign affairs.

In 1968 oil was discovered in the Norwegian part of the North Sea, and since then oil and gas fields have been developed and petroleum reserves gradually built up. To-day, Norway produces petroleum from the North Sea at a rate seven times her own consumption, which is rather unique for an industrialized country. The introduction of economic zones in the seventies, giving coastal states exclusive economic rights in an area extending 200 nautical miles off their shores, has further enhanced the resources potentially available to Norway. Depending on developments in the international energy markets, she may now become an important supplier of energy, especially of natural gas to Western Europe.

Considering the foreign policy and military dimensions of energy security, Norway may, more or less against her will, find herself at the focus of critical energy issues. The situaton is not made easier by the fact that the maritime areas under Norwegian jurisdiction seem to become increasingly important from a military point of view. The stronger this international dimension becomes, the more difficult it will be for Norway to have an influence on developments and defend her interests. Norway may have to take a stand on controversial issues which most small countries can keep at a comfortable distance.
Review of the Completion Practices in the Morrow Formation in Eddy, Chaves and Lea Counties of Southeast New Mexico
Authors: Pai Vithal J. , Garbis Sam J.
Published: December 2007

The Morrow formation is one of the main targets of the drilling activity in Southeast, New Mexico. This paper presents background information including formation lithology derived from X-Ray diffraction data and scanning electron micrographs. Formation rock characteristics such as frac gradients, permeability, porosity and formation water properties are also presented. Completion techniques such as cementing practices, casing programs and perforating programs are reviewed. The stimulation fluids, volumes, injection rates, and types of proppant used are presented to provide an optimum completion program.
Completion Practices and Reserve Estimates for Pecos Slope Abo Gas Field
Authors: Boneau David F. , Braswell Joe , Stall Albert R. , Tisdale Robert E.
Published: December 2007

Yates Petroleum has developed successful drilling and completion practices through experience with 200 wells in the Pecos Slope Abo gas field. Several methods have been used for estimating ultimate reserves from the wells in this low permeability reservoir. The most promising is a drawdown analysis that matches computerized type curves with data on daily flow rates and tubing pressure.
Formation Damage Potential from Carbon Dioxide—Crude Oil Interaction
Authors: Smith Gerald H. , Patton John T.
Published: December 2007

The rapidly expanding use of carbon dioxide, CO2, to enhance the production of crude oil has given rise to reports of apparent formation damage covering a wide range of oil and reservoir properties from different parts of the United States. In 1979 research was initiated at New Mexico State University to define the causes and re-commend solutions to the CO2 formation damage problems. One plausible damage mechanism concerns the precipitation of organic particulates as CO2 dissolves in the reservoir crude.

Three crude oils from pilot CO2 tests were studied to determine their tendency to form precipitates at their respective reservoir pressure and temperature. The three crudes selected for study were a Wilmington crude (California), a Maljamar crude (New Mexico) and a Hilly Upland crude (West Virginia).

To estimate formation damage potential for individual crude oils, volumetric flow versus time through an 8 micron absolute filter has been recorded for the crude saturated with CO2 at temperatures in the range of 77°–123°F (25°–50.5°C) and at pressures in the range of 300–1800 psig (3–18 MPa). The results, surprisingly, show no correlation with the asphaltic content of the crude, previously determined by inducing precipitation by the addition of either pentane or hexane to the crude.

Maljamar crude oil was the only crude that produced CO2 precipitated organic type particules. This crude was subjected to tests in an unconsolidated sand-pack to quantify its damage potential. Under tertiary recovery conditions a permeability reduction of 25% was observed even after 29% of the residual oil had been displaced. Under conditions simulating CO2 secondary recovery (no previous waterflood) some permeability reduction was observed. The relative permeability to water at residual oil saturation was 34% lower using CO2 as a secondary recovery phase as compared to a conventional waterflood.
Considerations For Designing Workover Operations With Continuous Coiled Tubing
Authors: McReynolds A. S.
Published: December 2007

The use of continuous coiled tubing to perform various types of remedial treatments or workovers has been well documented.1,2,3,4 Numerous successful treatments have been obtained with this device in oil, gas, injection and geothermal wells. However, the occurrence of and, more importantly, the causes of failures in operations involving coiled tubing have not been addressed by the industry. An examination of causes of failure should lead to a higher success ratio.
Application of Small-Diameter Inertial Grade Gyroscopes Significantly Reduces Borehole Position Uncertainty
Authors: Uttecht G. W. , Dewardt J. P.
Published: December 2007

Initial tests with a new directional survey tool show a significant enhancement in attainable accuracy over conventional instrumentation. Two prototype systems, developed over the last two years by Gyrodata, Inc., have recently been tested in a well in West Texas. Although many more tests are required, preliminary results indicate that the original design objective for borehole position uncertainty less than 1.7 feet per 1,000 feet of hole–has been met.

The Gyrodata Wellbore Surveyor employs an inertial grade rate gyro adapted from the aerospace industry. In combination with its other sensors and electronics, the device can sense the orientation of the earth's spin vector at each independent survey station. As a result, the major systematic errors associated with conventional gyros–geographical reference and unaccountable drift–are eliminated. Other sources of inaccuracy are minimized by the system's measuring techniques and operational procedures, and additional benefits should arise from faster survey speed and increased reliability. A true north reference device can also employ a small outside diameter since it requires only one gyro and one accelerometer, rather than the two or three of each needed in an inertial navigation system.
Salt Drilling in the Rocky Mountains
Authors: Sheffield J. S. , Collins K. B. , Hackney R. M.
Published: December 2007

A compilation of literature, design and operational data dealing with drilling and setting casing through salt formations is explained and summarized. This paper is adapted to drilling conditions in the Rocky Mountain area.

Discussion includes the origin of salt deposits, how salt can be detected during the planning and drilling of a well, and different drilling strategies employed for drilling salt. Casing design and cementing are discussed as well as failure of casing due to salt loading.

Operating experience is reviewed in several Rocky Mountain areas. Casing strings were set through salt with collapse ratings ranging from .3 psi per foot to 1.5 psi per foot. Casing collapse due to salt loading was observed in several wells with casing design ratings less than 1.0 psi per foot.

Conclusions are made concerning the major areas discussed in the paper including salt flow, inter-bedded salt, cementing and drilling strategy. The suggestion is made that casing set through salt zones should be designed for a collapse rating of 1.2 psi per foot.
Environmental Impact of Oil-Base Mud Cuttings Discharges—A North Sea Perspective
Authors: Poley J. P. , Wilkinson T. G.
Published: December 2007

Discharges of Oil-Based Mud Cuttings have an environmental impact which is limited in time and in volume/area. North Sea field data (1979-1982) indicates that beyond the immediate neighbourhood of the discharge, the hydrocarbon concentrations in the water column are effectively at ambient levels and environmental impact, if any, is difficult to establish.

Regarding the sea-bottom ecology the data shows the existence of three different zones:

A proximal zone, extending about 300-700 m from the platform, where cuttings form a surface deposit (thickest at the source and quickly thinning outward). Anaerobic conditions exist with associated H2S and biodegradation will be slow. Environmental impact will be most significant in the immediate neighbourhood of the source; any recovery will be slow. A distal zone, reaching beyond the proximal zone out to roughly 1500-5000 m, where cuttings may be found as thin patchy deposits of tiny particles, where aerobic conditions exist, and where biodegradation can readily take place. Environmental impact, if any, will be light, and recovery quick. The far zone, beyond some 1500-5000 m, where no environmental impact can be identified.

Local circumstances will determine the actual conditions around each source.
A Field Experiment To Assess Impact of Chemically Dispersed Oil on Arabian Gulf Corals
Authors: LeGore R. S. , Marszalek D. S. , Hofmann J. E. , Cuddeback J. E.
Published: December 2007

Field experiments were conducted on a coral reef at Jurayd Island (Saudi Arabia) in the Arabian Gulf to study the effects of chemically dispersed oil on local corals. Portions of the reef were exposed to predetermined concentrations of oil alone, dispersant alone, and oil-plus-dispersant mixtures. Areas of the reef not exposed to any of the toxicants were used as controls. Arabian Light Crude and Corexit 9527 dispersant were the test toxicants.

Two series of experiments were conducted beginning in September 1981, one with a 24-hour exposure period and the other with a 5-day (120-hour) exposure period. Corals were stained for growth rate studies and extensively photographed to document any observed effects. Corals were examined for biological impacts immediately after the exposures, and then at 3-month intervals for 1 year. Water temperature, salinity, dissolved oxygen, and hydrocarbon content were recorded during the exposure periods.

Coral growth appeared unaffected by exposure to the toxicants. Some Acropora species corals exposed to dispersed oil for 5 days exhibited delayed effects, which became apparent during the relatively cold winter season.
Computer Well Database—An Engineer's Tool
Authors: Hatch D. G. , Miller E. L.
Published: December 2007

A computerized exploration and petroleum engineering well database has been in use since 1975. The original design has evolved to meet changing user requirements and to take advantage of new computer hardware and telecommunications facilities. Today the system provides a broad information resource to geologists, engineers, and operating personnel.
Application of Sedimentological Studies in the Reservoir-Geological Modeling of the Al Huwaisah Field, Oman
Authors: Baumann André
Published: December 2007

A reservoir-geological review has been carried out on the Al Huwaisah oil field (North Oman) and a geological model has been developed. Mainly based on sedimentological studies of core material, the distribution of the different lithofacies types of the reservoir formation has been reconstructed and the depositional environment interpreted. The resulting geological model shows analogies with the sedimentation pattern on Recent carbonate shoals in the Arabian Gulf. This, in combination with the good correlation between lithofacies types and reservoir properties, allows prediction of the different reservoir units and hence optimisation of the future development of the field.
Field Studies of Inspection and Repair Operations of Subsea Structures
Authors: Bourhis M. Y. , Aldridge Thomas
Published: December 2007

There are approximately 3000 fixed offshore oil installations worldwide constructed to differing designs to meet a variety of requirements.

Subsea inspection techniques are required to confirm that initial construction is to pre-established standards and specifications and that structural deterioration is to levels which are consistent with the design and continued serviceability of a structure. Such inspection will normally satisfy the various interelated requirements of the operators the Government and the Certifying Authority.

Our paper contents :

– Review of the techniques at present commentary applied underwater – An application of ultrasonic equipment – An application of welded repair in a rigid hyperbaric habitat
Application of Acoustic Emission and Modal Analysis Techniques to Offshore Platform Surveillance
Authors: Claude Cochard
Published: December 2007

Two research projects have been conducted to study the possibility of using acoustic emission and modal analysis techniques for in situ surveillance of offshore platforms.

For acoustic emission, experiments onshore, in sheltered area and on platforms have been conducted. The experimental part of the program terminated with a test on a pre-cracked T-joint on a platform in the southern North Sea. A prototype industrial system and the corresponding interpretation software have been developped. The various tests show that acoustic emission allows detection of cracks and monitoring of crack growth in a limited area of a platform.

Modal analysis has been studied through theoretical analysis, small scale tests and field tests on an operational platform. Two slightly different techniques have evolved from the study:

– modal analysis per se which gives global information on the overall structure. – vibrodetection which provides more accurate measurements on individual bracings.
Analysis of Pressure Buildup Curves Based on Field Experience
Authors: Arora P. D.
Published: December 2007

The subject paper deals with the application of Build-up data in computing vital reservoir parameters in oil fields. Generally technique of Miller Dyes and Hutchinson is utilized to determine flow capacity, permeability skin effect and completion efficiency. Build-up data is utilized in detecting the existence of faults. Method of Brons and Marting has been found to be more reliable to determine the partial penetration effect. The computer software package which was developed recently is discussed and due to near ideal behaviour of build-up curves, it is safely utilized. The computational work using the software package is rapid.
Field Test Results—A New Logging Tool for Formation Density and Lithology Measurements
Authors: Borai A. M. , Muhsin M. A.
Published: December 2007

The formation porosity can be determined from borehole density measurements if the grain density of the rock is known. Generally, this is determined from the lithology.

The Litho-Density Tool, LDT, provides an improved measurement of the formation density and a new measurement of lithology.

Field tests of LDT proved that the tool could be run alone in a wide range of formations to provide porosity values comparable to those obtained by running a density log combined with a neutron log.
Improved Saturation Determination with EPT
Authors: Freeman D. W. , Henry K. C.
Published: December 2007

The accuracy of formation fluid saturations determined by log analysis has improved steadily over the years. However, the problem of what values to use for the exponents "m" and "n" in the saturation equation remains. Laboratory measurements on core samples show that these exponents can vary significantly over short intervals, but assumed average values must be used in actual calculations. These average values may or may not be representative, depending on the formation homogeneity.

The EPT (Electromagnetic Propagation Tool) measurement allows the calculation of saturations near the borehole without a knowledge of "m" or "n". Using the EPT saturation, a method is developed to calculate "m" and "n" from the logs as a continuous record. These calculated values provide an improved water saturation calculation from the regular resistivity and porosity logs.

Several examples are shown to demonstrate the application of the new method. Core analyses, core descriptions, and drill stem test results are included which support these improvements.
A 1982 Critique on Gas Cycling Operations on Gas-Condensate Reservoirs
Authors: Aziz R. M.
Published: December 2007

A discussion of gas-cycling operations in a gas-condensate reservoir cannot be complete without covering the full range of operations from drilling and well completion, reservoir analysis, surface handling of gas and liquids, LPG plant operation, gas compression, gas sales and reinjection. All of these factors are interrelated in a decision to start cycling and even more important, is the time to start and stop injection and the quantities of dry gas to be injected. The following discussion however, strictly deals with the reservoir aspects of cycling.

It is recognised that in certain gas reservoirs at high pressures, oil condenses out of the gas phase with reduction in reservoir pressure contrary to the normal phase behaviour at low pressures. The process is called retrograde condensation. The production process called cycling aims at preventing further dropout of retrograde liquid as well as revaporizing the liquid phase so that it can be produced with the gas.

Figure 1. is a typical phase diagram of a gas-condensate type reservoir. The pressure at which the first drop of liquid appears in the gas phase is called the dew point. Below the dew point pressure, further reduction in the reservoir pressure will increase the volume percent of liquids in the reservoir until the maximum liquids have been dropped out of the gas phase. Equilibrium volumes of the liquid and the gas phases at any pressure and temperature depend upon the composition of the mixture. The laboratory data collected by constant volume isothermal pressure reduction shows that at an intermediate pressure marked by point "A" in Figure 1. the liquid volume begins to decrease due to revaporization. However, not all of the liquids revaporize, even when the pressure is reduced to atmospheric pressure. From the reservoir point of view, it was assumed that the liquids dropped in the reservoir neither flow nor revaporize. Therefore, actual reservoir behaviour was calculated assuming a phase diagram shown by the dotted line on Figure 1.
A Rheological Model for Drilling Fluids and Cement Slurries
Authors: Gucuyene I. H.
Published: December 2007

A three constant model is developed describing the rheological behavior of drilling fluids and cement slurries. The proposed model and the former ones, the Bingham, power law, Herschel-Bulkley, Casson, Robertson-Stiff, were tested with the measured data for a total number of seventy one drilling fluids and cement slurries of which twenty of them are presented here. The results, in general, conform to the proposed model with a high degree of accuracy.

Flow equations, based on the proposed model, are also developed for both pipe and annular flows.
Parameterization of Match-Derived Pseudo-Relative Permeabilities
Authors: Hales H. B.
Published: December 2007

Pseudo-relative permeability functions were generated by automatically matching the pressures and oil production volumes obtained from two-dimensional cross-sectional simulations. The 2-D simulations used actual reservoir fluid and rock properties, but incorporated hypothesized stratifications and dip angles. The resulting pseudo-relative permeability curves were correlated as a function of the water breakthrough time and the maximum pressure differences observed in the corresponding simulations. The resulting suite of relative permeability curves then offered a simple method of matching historically observed pressures and production volumes in three-dimensional simulations of the reservoirs. Similar possibilities exist for altering pseudofunctions to obtain history matches in areal models.
Problems in Squeeze Cementing
Authors: Toor I. A.
Published: December 2007

For the past half century, work has been carried out to improve squeeze cementing. During the course of time, new techniques, equipment, cement and cement additives were introduced. Work is still underway to improve squeeze cementing. Basic concept of squeeze cementing, understanding the problems, planning for a squeeze job and then later testing of the job help in achieving the goal. Solutions were offered to some common problems, whereas many regional problems need time to time study and effort. Squeezing long perforations in highly permeable sand has always been a problem, for which some techniques were presented.
Loudon Surfactant Flood Pilot—Overview and Update
Authors: Bragg J. R. , Gale W. W. , Canning J. W.
Published: December 2007

A successful surfactant (microemulsion) flood pilot test in a watered-out portion of the Weiler sand, Loudon Field, Illinois (USA) was completed in October, 1981. The microemulsion system tested was designed to be effective in the presence of high-salinity formation water containing 104,000 ppm (mg/l) total dissolved solids (TDS) without use of a preflush. The test was conducted in a single, 0.68-acre (2752 m2) 5-spot operated in a manner that approximated a confined pattern. The test was highly successful, recovering 60% of the oil remaining after waterflood. Cores from a post-flood well drilled within the pattern have confirmed the low final oil saturations and low surfactant retention achieved in the flood.

Although oil recovery was excellent, loss of mobility control in the polymer drive bank and premature breakthrough of lower-salinity drive water were observed part-way through the test. Laboratory and field studies conducted since flood termination have confirmed that loss was caused by bacterial degradation of the xanthan biopolymer used. Several biocides were tested in the laboratory and in a field injection experiment to determine their effectiveness against the bacteria contaminating the pilot. Formaldehyde was shown to kill bacteria within the formation, have negligible adsorption on reservoir rock, and permit propagation of undegraded polymer. Based on these test results, formaldehyde should protect xanthan biopolymer from bacterial degradation in future microemulsion floods at Loudon.
Design and Evaluation of a Gravity-Stable, Miscible CO2-Solvent Flood, Bay St. Elaine Field
Authors: Nute A. J.
Published: December 2007

A gravity-stable miscible CO2-solvent flood is underway in the Bay St. Elaine Field, South Louisiana. A 33% pore volume CO2-solvent slug was injected into a dipping water drive reservoir and is being pushed downdip by the injection of nitrogen gas. The CO2-solvent selected for this tertiary flood was tailored by the addition of methane and n-butane to the carbon dioxide. This CO2-solvent provides the density difference required to complete a gravity-stable flood within the desired time period and also satisfies the minimum miscibility pressure requirements at reservoir conditions.

The paper presents laboratory experimental work performed and process design work required to undertake this type of enhanced recovery project. The results obtained from slim tube tests to determine the CO2-solvent composition are presented as well as results of 12-foot sand pack displacement tests to evaluate the recovery efficiency of the selected CO2-solvent. Procedures used to determine the mixing zone lengths needed for CO2-solvent slug design are discussed along with the method of calculating critical velocity.

Pressure pulse tests conducted to improve reservoir definition within the project area are reviewed. In situ residual oil saturations for the unconsolidated sand determined from pressure cores, log-inject-log water flood tests, single well partitioning tracer tests, and open hole well logs are presented. Field injection and current production data are also analyzed.

The methods presented are being used to design CO2-solvent floods for reservoirs previously thought to be unsuited for conventional miscible CO2 flooding. The procedures and concepts discussed can be applied to flood design for numerous secondary and tertiary miscible CO2 projects.