bluuebunny/crossref_metadata_2025 huggingface dataset:
Computer Enhancement of Borehole Television Imaging
Authors: Walbe K. A.
Published: December 2007

The Borehole Television Camera has been utilized successfully in the Appalachian Basin for the identification of natural fracturing and associated hydrocarbon production within the wellbore.

Many of the images recorded on the videotape at the time of logging are of less than optimum quality due to borehole conditions and camera lighting imbalances.

The on-board enhancement capability during logging is unfortunately limited to adjustments in light source intensity and the making of multiple passes over the zones of interest in order to get a better picture.

However, with the utilization of post logging computer processing, many of the downhole images can be enhanced visually, while at the same time, calibrated measurements can be made.

An image analysis and enhancement system consists of five components : the image source (which in this case is commonly a video cassette recorder (VCR); a video raster screen (RGB monitor); a video adapter board (frame-grabber); a computer with monitor (a coprocessed, 386-based machine with lots of memory); and, finally, a utile software package.

Having captured the image (using the frame-grabber board), the image is then processed and enhanced. The degree of resolution possible in an image is in part determined by the fineness of the pixel grid.

The image processing that can be performed includes the removal of artifacts and noise, contrast enhancement for easier viewing, object boundary determination so that objects may be counted and measured, and finally, image subtraction that can remove disruptive background shades.

Practical applications of the measurement techniques are in the estimation of: extent of corrosive pitting in casing, size of perforations after fracing, relative oil production from individual perforations based on oil globule size, and natural fracture width and fracture area measurements.
Economic Justification for LAN Installation in an Oilfield Equipment Manufacturing Operation
Authors: Frishmuth R. E. , Gariepy J. A.
Published: December 2007

The oil field equipment manufacturing business, like any other business working in a world wide environment, is becoming interested in reducing the amount of time required to take a product from initial concept to the market place. The most recent concept being employed to achieve this goal is concurrent engineering.

This paper discusses the use of local area networks connecting personal computers to facilitate both traditional engineering and manufacturing organizations and concurrent engineering concepts. The key to making either type of organizational structure work well is communication. As companies have moved away from large mainframe computers toward individual, stand alone, personal computers, communications as well as various databases have been difficult to maintain. The authors attempt to show how a LAN would help to solve problems with data integrity, communication and speed of product development. These ideas are combined with discussion of anticipated cost savings as well as LAN installation cost. The authors show that the initial cost of LAN installation can easily be justified by the costs saved in product development.
An Assessment of Natural Fracturing in the Umm Shaif Thamama Field by Reservoir Surveillance
Authors: Gibson A. P. , Al Kaioumi Q. M. , El-Amin A. M.
Published: December 2007

The presence of natural fracturing in the Umm Shaif Thamama Field was postulated following its discovery in 1958. The performance of this reservoir was poorly understood being based on information gathered from a small number of well tests executed during the 1960's and 70's. An up to date assessment of this reservoir was sought utilising the latest reservoir monitoring technology. The objective was to confirm the existence, magnitude and orientation of any fracturing in the Thamama reservoir. A further objective was to evaluate their distribution within the zones of the Thamama reservoir. The surveillance programme included multi-well interference testing, pressure build-up testing, production logging and water saturation monitoring. The conclusions from this study were an unusually high kv/kh and strongly anisotropic reservoir transmissibility arising from the presence of fractures.
Reducing Risk: Priorities and Strategies for Environmental Protection
Authors: Loehr R. C.
Published: December 2007

In late 1990, the USEPA - Science Advisory Board (SAB) completed a major report for the EPA Administrator and the report recommendations have resulted in policy changes in EPA. A key component of the report is the identification of relative environmental risk and the need to focus on environmental problems of greatest risk. This paper discusses the background and rationale of the report, how the recommendations have been implemented within EPA, and the potential impact to the petroleum production and refining industry.
EPA Initiatives for Improving the Management of Crude Oil and Natural Gas Exploration and Production Wastes
Authors: Derkics D. L. , Robinson B. B. , Souders S. H.
Published: December 2007

Pollution prevention and waste minimization have become essential components of exploration and production (E&P) operations. Environmental accountability necessitates including pollution prevention and waste minimization in well planning and engineering, and waste management programs. Viable approaches should include waste minimization guidelines, employee training, and development of innovative technologies in addition to good housekeeping practices and product substitution.

This paper presents several initiatives instituted by the Office of Solid Waste (OSW) of the U.S. Environmental Protection Agency (EPA) for improving the management of E&P wastes. Through these initiatives OSW encourages a cooperative effort among industry, regulatory agencies, and other interested parties to develop creative solutions for improving E&P waste management practices.
Impacts of Environmental Initiatives on the Cost of Producing Crude Oil and Natural Gas Supplies
Authors: Godec M. L. , Smith G. E. , Kosowski Bundhrig
Published: December 2007

The environmental regulatory climate is dynamic, and the cost to comply with increasing environmental requirements can have a significant impact on oil and gas exploration and production operations. Identification of potential future requirements can allow operators to build environmental compliance into project designs, saving costly retrofit as new requirements are imposed. This paper describes many of the initiatives currently being considered under several major federal environmental statutes, discusses the potential cost of compliance, and examines the potential impacts of these initiatives on oil and gas supplies.
Land Treatment of Petroleum Hydrocarbon-Based Drill Cuttings: Pilot Scale Field Study
Authors: Barker G. W. , Armstrong K. W. , Adamson T. J.
Published: December 2007

A pilot scale feasibility study was initiated to evaluate the feasibility of landfarming diesel mud residues in southeastern Oklahoma. Results indicated that land application of diesel residues is an environmentally acceptable disposal method. In a plot with an initial oil and grease (O&G) loading rate of 7.6%, the O&G content decreased by 89.5% during the 209-day study interval. Addition of nutrients enhanced degradation rates and reduced O&G levels below the 1% phytotoxic threshold. An O&G loading rate of 5.8% resulted in no measurable hydrocarbon migration in the soil profile. BTEX levels in leachate samples did not exceed drinking water standards. Total metals measured in the zone of incorporation did not exceed guidelines for limiting constituents. Seed germination studies suggested that landfarming operations could be revegetated within 180 days.
Analysis of Gas-Rise Velocities From Full-Scale Kick Experiments
Authors: Hovland Frank , Rommetveit Rolv
Published: December 2007

Gas kick experiments in oil- and water-based mud have been studied in a full scale inclined research well. One of the main objectives from these experiments has been the study of gas rise velocities. In order to analyse the gas velocities, the parameters varying during a real drilling operation have been systemized and gathered in a data base. The work represents a significant extension to existing correlations for gas/liquid flows in a full scale inclined annulus with real drilling muds.

In high concentration gas kicks the gas rises faster than in low and medium concentration kicks, this is observed for both oil and water based mud. The rise velocity correlations obtained from these experiments is not significantly dependent on gas void fraction, mud density, inclination, mud rheology, and surface tension. The results are quite different from other previously reported correlations, and this has a major implication on kick simulations.
Use of a Unique Weighting Agent for Slimhole Drilling
Authors: Randolph S. B. , Walker S. H. , Young G. A. , Dorrough D. S.
Published: December 2007

Slimhole continuous coring and drilling is becoming an accepted method for oil and gas exploration. As the applications for slimhole drilling expand into frontier areas, weighted drilling fluids specifically tailored for slimholes are needed. In high speed (200 to 1000 rpm), slimhole, coring the use of conventional weighting material may result in its deposition on the inner wall of the drillstring making it difficult to wireline retrieve the core. To solve this problem a finer-grind weighting material, pigment-grade barite, was investigated. The overall results of this investigation are as follows: Weighted cationic brine muds, exceeding 14 lb/gal, may be formulated with acceptable viscosity using pigment-grade barite.A centrifuge rotating at reduced speed is capable of discarding much of the low gravity solids without discarding too much fine grind barite.The pigment-grade barite did not interfere with wireline core retrieval within reasonable operating ranges of drilling parameters.
Control of Water Influx in Heavy-Oil Horizontal Wells by Polymer Treatment
Authors: Zaitoun Alain , Kohler Norbert , Montemurro M. A.
Published: December 2007

Four horizontal wells producing a heavy oil from a sand formation were successfully treated with a new polymer process to reduce their water production. In this process, Polyacrylamide is injected with a swelling agent which induces a strong viscosity build-up in-situ before production release. The treatment was shown to reduce the relative permeability to water with little effect on the relative permeability to oil. Because of the high oil/water mobility ratio, the polymer was expected to invade the zones of highest water saturation preferentially and thus did not require zone isolation during injection. Polymer slug volume was optimized by numerical simulations. In the best case, the treatment induced a drop in the water cut from 85 to less than 50% and a strong increase in oil production. The treatments performed in 1989 are still efficient in 1992. In addition to its effect on the water cut, the treatment reduced sand production in three of the wells.
Electrical Impedance Variation With Frequency in Shales and Shaly Sands
Authors: Adisoemarta P. S. , Morriss S. L.
Published: December 2007

An experimental research program has been initiated to investigate the electrical properties of swelling shales across a wide frequency range, 10 Hz to 1.3 GHz. This range spans the spectrum of the commonly used downhole logging measurements, from the deep laterologs to the microwave dielectric tools. Three distinct measurement techniques have been utilized to span the range: multiple electrodes at low frequencies, two-electrode with balanced bridge for the middle frequencies, and open-ended coaxial probe with network analyzer at the high end. The probe technique is simple to use, potentially enabling field measurements of complex permittivity to be taken, although some accuracy is sacrificed. The effects of swelling are most pronounced at the lowest frequencies. The weight of a shale which has been exposed to a change in relative humidity reaches equilibrium long before the electrical properties do.
Styles of Deposition and Diagenesis in Leonardian Carbonate Reservoirs in West Texas: Implications for Improved Reservoir Characterization.
Authors: Ruppel S. C.
Published: December 2007

Leonardian carbonate rocks in the Permian Basin constitute a thick succession of shallow-water platform deposits that display extreme degrees of reservoir heterogeneity and abnormally low recovery efficiencies. The complexity of these reservoirs is a function of the interrelated effects of (1) cyclic, multifrequency rise and fall of relative sea level, (2) paleotopography, and (3) diagenesis.

This paper presents a detailed geological characterization of Leonardian fades architecture based upon application of modern sequence stratigraphie concepts. It proposes a model that interrelates the distribution of depositional and diagenetic facies with development of porosity and permeability in this important hydrocarbon play.
Characterization of a Fluvial-Dominated Delta: Zone 1 of the Prudhoe Bay Field
Authors: Begg S. H. , Gustason E. R. , Deacon M. W.
Published: December 2007

Core and log data indicate highly variable reservoir quality in the lower part of the Prudhoe Bay reservoir. Characteristic reservoir descriptions were developed in order to investigate the sensitivity of production performance to reservoir heterogeneity. Detailed core description and analysis showed that grain-size (lithotype) was the major control on poroperm. In turn, the spatial distribution of lithotypes is governed by the depositional environment, which is interpreted as a fluvial-dominated delta. This led us to develop new, quantitative, object-based models of the distribution of lithotypes within each of four major facies associations. These models were then converted to spatial distributions of poroperm on the core-plug scale, and these then re-scaled to give effective reservoir simulation grid properties. The quantitative lithotype models contain a number of variable parameters which enable sensitivities to uncertainties in the geological description to be studied.
Pressure Transient Behavior of Fractured Wells in Coalbed Reservoirs
Authors: Anbarci Kemal , Ertekin Turgay
Published: December 2007

A solution package that describes the pressure transient behavior of coal reservoirs in the presence of a hydraulically fractured well is presented. In the development of the solutions uniform-flux vertical fracture model is employed. The proposed solutions are then extended to describe the pressure transient behavior of composite coalbed reservoirs with a vertical well which may have a vertical fracture. The proposed composite system solution has potential applications when "Tailored-pulse" fractures or damage exist around the degasification well.

In this study, dual porosity nature of coal seams is modeled by describing micropore structure by spherical matrix elements. The formulation employed includes single-phase laminar gas transport in the natural fracture network (cleat system). Flow within the micropores is described by Fick’s law of diffusion. Matrix to fissure flow mechanism is modeled by unsteady-state sorption/diffusion formulation. The equilibrium isotherm which defines the amount of desorbed gas is obtained through Langmuir’s theory. The solutions are obtained analytically in the Laplacian space and inverted to the real time domain via Stehfest algorithm.

The proposed solutions are tested against the subsets of the problem with known solutions and in each case excellent agreements are observed. Furthermore, the pressure transient data generated by a finite difference coal seam degasification model are used to check the validity of the solutions presented. Sensitivity of the solutions to a wide range of coal seam properties are also included.

The solutions presented in this paper equip me well test analysis engineer with a precise tool to analyze the pressure transient behavior of the hydraulically fractured degasification wells. The solution package encompasses infinite, constant pressure and no-flow outer boundary conditions together with constant flow rate specification at the wellbore.
Geologic Reservoir Characterization for Engineering Simulation, Hatter’s Pond Field, Mobile County, Alabama
Authors: Stoudt E. L. , Thomas A. R. , Ginger E. P. , Vinopal R. J.
Published: December 2007

Geologic reservoir characterization of Hatter’s Pond Field, Mobile County, Alabama was conducted using a combination of lithologic and petrophysical data in order to determine appropriate reservoir layering and flow units for engineering simulation and reservoir management. 15,000 feet of core provided the foundation for the geologic study. Layer models were constructed via computer, and numerical grids were supplied directly to the simulator. Three dimensional computer modelling enhanced understanding of reservoir quality distribution.

Lithologic analyses indicate that productive Norphlet Formation lithologies are aeolian dune sandstones capped by a reworked transgressive marine sand sequence. Smackover Formation reservoir units consist of dolomitized transgressive marine carbonates shoaling upward into pellet/oolite bars and sealed by the intertidal and supratidal carbonates and evaporites of the overlying Buckner Formation. Significant variations in porosity and permeability occur both vertically and laterally within the producing formations.

Geologic controls on reservoir quality in the Smackover Formation at Hatter’s Pond are strongly diagenetic. Texturally destructive dolomitization has obliterated depositional fabrics, and created pore systems controlled by dolomite crystal size/shape and the presence of early fabric-selective leaching in grainstones overlain by exposed facies. Norphlet Formation reservoir character is related to the original depositional fabric, which has been modified by pressure solution and quartz cementation.

Without available core, the model would have been much less accurate, because logs alone do not reflect the diagenetic changes that control the reservoir. By combining core, log, and other petrophysical data, the layering and flow units provided to the simulator produced acceptable history matches in as few as 6 simulation runs.
A Simulated Annealing Approach to Constrained Nonlinear Optimization of Formation Parameters in Quantitative Log Evaluation
Authors: Cheng-Dang Zhou , Chu-Qiao Gao , Zhen-Wu Jin , Xi-Ling Wu
Published: December 2007

Quantitative log evaluation is essentially a model-based inversion of well logs, which is a constrained nonlinear global optimization problem when a prior information is sparse, where how to obtain global optimal solutions is the key problem. While many previous papers either avoid the nonlinearity by transformation methods, or simplify the nonlinearity in log analysis by linear approximation, or even use "steepest descent", or conjugate gradient techniques which are inapplicable for finding a global optimal solution in log analysis, based on an analogy between the model-algorithm system and a statistical mechanical system, this paper investigates the use of an efficient, global, stochastic optimization method, that of simulated annealing, for determining the optimal estimates of formation parameters in log analysis in such a case of constrained nonlinear optimization which is based on a well log interpretive model.

This paper presents the algorithm of simulated annealing global optimization of log analysis. The methods are given to determine the key parameters in such a simulated annealing. And finally both the advantages and limitations of this approach are pointed out.

A field example presented from China demonstrates the usefulness of this new approach and its comparison with the results processed by another log analysis software widely used in China indicates that this approach can efficiently overcome local minimum problem and provides more accurate estimates of formation parameters.
Identification of Clay-Supported and Framework-Supported Domains from Geochemical and Geophysical Well Log Data
Authors: Herron S. L. , Herron M. M. , Plumb R. A.
Published: December 2007

Geochemical and geophysical well log data can be used to discriminate between clay-supported and framework- (or grain-) supported domains on the basis of observed clay and porosity relationships. The existence of these domains in unconsolidated materials has been inferred from experimental, bimodal mixtures of quartz and kaolinite but has not been demonstrated in consolidated rocks. The grain supported domain is characterized by decreasing porosity and increasing compressional velocity with increasing clay content. The transition to the clay-supported domain is marked by a reversal or flattening of these trends in porosity and velocity. In the clay-supported regime, increases in clay content correspond to increases in porosity and decreases in compressional velocity.

The existence of the two domains can be identified by modified v-shaped patterns in clay porosity crossplots or by inverted v-shaped patterns in clay velocity crossplots. Once the patterns have established for a given section of a well, they can be statistically analyzed, and then the clay volumes can be used to create synthetic logs of porosity and compressional velocity. Outside the range where the statistical fit is performed, deviations between the synthetic logs and the measured logs may be interpreted as geological discontinuities. These discontinuities are most likely due to the diagenetic history of the rocks, and in most cases probably represent time horizons.
A Comparison of Log Interpretation to Core Results Using a Full Element Model and a Reduced Element Model in the East Texas Cotton Valley Sandstone of GRI Well No. 3
Authors: Everett R. V. , Johnston D. J. , Quirein M. C.
Published: December 2007

The purpose of this project was to develop better methods for the evaluation of tight gas sands using logs and cores for enhanced hydrocarbon detection and enhanced stress profile determination. The results of this study showed that minerals greatly affect the interpretation of the hydrocarbon reserve potential derived from log measurements. Using the core measurements as a guide to determine which minerals were present in the formation, a mineral model that did not require core calibration was developed to convert elements to minerals. The first mineral model used the full range of elements available -Si, Ca, Fe, Al, K and Ti as well as correlations to the photoelectric effect (Pe) to derive Mg and the epithermal neutron-density logs to derive H2O+. The second model used a reduced set of elements, K and Th. Both models also used resistivity, electromagnetic, acoustic, epithermal neutron and density log measurements.
Areal 3D Seismic Methods for Reservoir Characterization Case History from the Niger Delta
Authors: Idowu A. O.
Published: December 2007

In the 1950s, early exploration period in the Niger Delta witnessed the use of 2D (two -dimensional) Seismic reflection method which is a adequate for imaging large subsurface geologic features including growth faulting and roll - over anticlines. This technique involves the Common Depth - Point Method (CDP) which acquires a plane of seismic information in distance along the surface and in time into the geological section, and is used to improve the signal - to - noise (S/N) ratio, to remove multiples and consequently give a representation of the subsurface particulrly if the data are collected up - or downdip.

By mid-1980s, the obvious geological structures have, in general been discovered and it became necessry to adopt a more sophisticated technique such as the 3D (three - dimensional) Seismic method to delineate more subtle reservoirs and resolve complex fault patterns in order to aid exploration as well as facilitate efficient field development. The case history discussed in this paper involves the use of areal 3D Seismic method for delineating the reservoir characterisation of the OK-field located in a shallow water area of the Western Niger Delta.

The areal 3D sismic technique is superior to the earlier CDP method in that a cube of seismic data can be collected in two dimensions in space and in one time by a variety of pattern adopted for gathering the 3D data for the OK-field’s reservoir which involves the shooting into lines of detectors which are at some angle to line of sources. The objective is to adequately sample the subsurface so that changes in vrious parameters such as the amplitude, phase or power in the seismic signal or velocity of propagation can be mapped areally and interpreted as an indication of changes in the physical properties of the rock matrix.

The 3D data for the field was acquired, processed through migration and it was possible to display what is essentially a cube of seismic data as a series of layers cut horizontally and vertically through the reservoir complex. This is done on a television screen for video presentation and reproduction, while the addition of on interactive computer system enables a three dimensional interpretation of the seismic data to be made. The net effect is that an efficient and cost-effective reservoir development was accomplished by proper timing and appropriate location of production wells for the drainage of this field.
Effect of Reservoir Stress Path on Compressibility and Permeability of Sandstones
Authors: Rhett D. W. , Teufel L. W.
Published: December 2007

Matrix permeability and pore volume compressibility are fundamentally important characteristics of hydrocarbon reservoirs because they provide measures of reservoir volume and reservoir producibility. In most laboratories these quantities are measured under hydrostatic (isotropic) loads that do not truly reflect the deviatoric stress state that exists in most reservoirs and do not adequately simulate the evolution of effective stresses in the reservoir as the reservoir is produced. Compression tests on reservoir sandstones show that both the compressibility and matrix permeability vary markedly with stress path (defined as the change in effective horizontal stress/change in effective overburden stress from initial reservoir conditions). Hence, changes in reservoir properties measured under hydrostatic loading conditions may be very misleading if applied to a reservoir that follows a non-hydrostatic stress path. Representative measurements of reservoir properties should be measured in the laboratory under loading paths that duplicate the stress path followed by the reservoir during production. Consequently, optimum reservoir management may require that the reservior stress path be determined by measuring in situ stresses early in the production history of a reservoir and periodically thereafter as the reservoir pore pressure is reduced.
NMR Imaging of Multiphase Flow in Porous Media
Authors: Chen Songhua , Qin Fangfang , Kim K-H. , Watson A. T.
Published: December 2007

The use of nuclear magnetic resonance (NMR) imaging techniques for determination of porosity and saturation distributions is investigated. Difficulties in quantitation which arise from the short transverse relaxation times exhibited by fluids in porous media are addressed. Procedures are presented whereby transverse relaxation during the signal acquisition process is modeled so that accurate estimates of intrinsic magnetization intensity, and thus porosity and saturation, can be obtained. Special consideration is given to saturation/position dependence and multi-exponential behavior of transverse relaxation. These procedures are validated with results for longitudinal profile images. The use of thin-slice cross sectional profile images are demonstrated by observing fluid displacement in a rock sample with structural heterogeneities.
Successful Submersible Lift Operations in Gassy Horizontal Wells, Pearsall Field, Texas
Authors: Freet T. G. , McCaslin K. P.
Published: December 2007

Oryx Energy Company has drilled, completed, and produced over 150 horizontal Austin Chalk wells in the Pearsall Field of South Texas. Although rod pumping is the predominant means of artificial lift for these wells1, selected wells are equipped with, submersible pumps to maximize production in a competitive reservoir. In 1989, the first submersible pump was installed in a horizontal well in the Field, and it was quickly discovered that high volume lift operations in gassy, naturally fractured horizontal wells offer unique challenges. These challenges included unpredictable changes in rates, heavy slugging and frequent pump cycling.

This paper reviews experiences with ten submersible installations in horizontal Chalk wells of varied operating conditions. Actual field performance of the installations will be discussed with special emphasis on the iterative design process that led to a dip tube design2 which successfully tackled the aforementioned challenges.
Experimental and Theoretical Investigation of Two-Phase Flow in Horizontal Wells
Authors: Ihara Masaru , Brill J. P. , Shoham Ovadia
Published: December 2007

An experimental and theoretical investigation of the flow behavior in horizontal wells and its interaction with the reservoir was performed. This has been recognized as one of the unsolved, yet most important problems in the production area.

A new test facility was designed and constructed, suitable for acquiring data on the relationship between the pressure drop along the well and the fluid influx from the reservoir. The test facility features a 1-in. I.D., 26-ft long horizontal well test section flowing into a 9.2-ft high vertical section. Pertinent preliminary data were acquired.

Initial models are proposed which describe the flow behavior in a horizontal well configuration for both the experimental work and field operations. The models use the IPR (Inflow Performance Relationship) approach, the black oil model and mechanistic models for wellbore hydraulics.

A sensitivity analysis was performed on key parameters using the model for field operations. Good agreement was found between the model for the experimental work and the preliminary experimental data.

A new IPR apart from the extension of the Darcy's law must be investigated extensively to help in the proper design of horizontal wells.
Assessing Risk Reduction Strategies on Offshore Newfoundland Development Projects
Authors: Way K. K. , Fong J. H. , Moynham G. J.
Published: December 2007

Development of petroleum reserves on the Grand Banks offshore Newfoundland commenced in 1990 with the signing of binding agreements relating to the Hibernia development project. Financial and fiscal incentives, which were provided to Hibernia, may not be available to subsequent projects. The possibility of low world oil prices and high development costs depresses the anticipated level of profitability of Grand Banks fields. Potential price volatility, wide ranges in reserves and uncertainty with respect to reservoir performance and costs contribute to the variability of anticipated profitability of such fields.

An illustrative, partially delineated, Grand Banks oilfield is examined in this paper. The field is considered a candidate for development, given satisfactory economic returns and the relevant project risks are identified, quantified and managed. This paper summarizes an approach to assessing the expected level and variability of economic returns on the subject field.
Risk Assessment Approach to Offshore Safety: Part B—The Valhall Firewater System: A Case Study
Authors: Ciaraldi S. W.
Published: December 2007

The use of risk analyses techniques as prescribed by Norwegian regulations is illustrated as it relates to an offshore piping retrofit. The Valhall Field case study of replacement of corrosion prone carbon-steel firewater systems with those constructed of fiberglass piping is reviewed. Key to justification of the deviation from the then existing regulatory restrictions on use of non-metallic piping materials was a risk assessment evaluation of the proposed modification. The risk assessment involved the establishment of performance based function criteria for deluge firewater systems and subsequent systematic evaluations of steel and fiberglass systems under normal operating and explosion/fire accident scenarios. The associated verification test program and specification/quality assurance (QA) developments are also briefly reviewed.
Slug Flow Characteristics and Their Effect on Corrosion Rates in Horizontal Oil and Gas Pipelines
Authors: Sun Jyi-Yu , Jepson W. P.
Published: December 2007

The flow characteristics of slug flow and their effect on the corrosion rates are examined experimentally in a 100 mm diameter, horizontal, Plexiglass pipeline. The system was maintained at a pressure of 2 bars and temperature of approximately 35 °C. After initial tests with oil only and water only, 80% water and 20% oil, and 60% water and 40% oil mixtures were examined. Carbon dioxide was used as the gas. Using the stationary slugs described by Jepsonl1,2, the mean wall shear stress and turbulent intensity at 7 different axial and three circumferential locations were measured using flush mounted TSI hot film anemometer probes. The regions included the film region ahead of the slug, the mixing zone at the slug front, and a short distance into the slug body. The oil, water, and carbon dioxide fractions were measured across a vertical diameter using a sampling probe. Corrosion rates at the top and bottom of the pipe were measured using electrical resistance probes. Pressure gradients across the slug front were also taken.

The results clearly show that the slug front is a highly turbulent region that has large wall shear stresses at the bottom of the pipe. The wall shear stress decreases with circumferential position but increases with increasing oil fraction in the fluids. For a Froude number of 12, the shear stress for water only is 26 N/m2. For the mixture of 60% water and 40% oil a value of 97 N/m2 is attained. These are much greater than anticipated. Instantaneous values are much larger than this. The corrosion rates are much greater than those predicted by usual laboratory methods, such as rotating cylinders or disks. The rates are shown to be greatest at the bottom of the pipe and correspond to the regions of high wall shear. Corrosion rates increase with an increase in oil concentration at the same Froude number. It is concluded that the wall shear stress associated with the slug front is sufficient to continuously remove corrosion products from the pipe wall.
A Transient Multiphase Temperature Prediction Program
Authors: Erickson D. D. , Mai M. C.
Published: December 2007

A computer model has been developed which accurately describes transient heat transfer in buried multiphase pipelines. The model is used primarily to estimate hydrate and paraffin potential during startup, shutdown, and blowdown in subsea oil/gas flowlines. Other uses include specification of minimum temperature requirements for pipeline materials that may be exposed to high-pressure blowdown. The model development is described, and examples of application are presented.
Dynamic Production System Nodal Analysis
Authors: Stoisits R. F.
Published: December 2007

A Dynamic Production System Nodal Analysis (DPSNA) Technique has been developed, verified, and applied to wells’ in the Kuparuk River Field.

This analytical technique combines reservoir performance models, nodal analysis for individual wells, and calculation of pressure drop in the network of surface lines to obtain a global analysis of the production system through time.

Evaluation of the DPSNA Technique was performed using well test data from twenty-five wells in the Kuparuk River Field. Each well in the analysis contained two productive intervals. The DPSNA Technique was able to predict the effect of a producing zone control strategy on oil, gas, and water production from these wells.
Design and Installation of a 20,500-ft Coiled Tubing Velocity String in the Gomez Field, Pecos County, Texas
Authors: Adams L. S. , Marsili D. L.
Published: December 2007

This paper reviews candidate selection, installation design, implementation, and production results of a 20,500 ft coiled tubing velocity string in the G. M. Shelton No. 2, a deep, low pressure, Gomez (Ellenburger) Field gas well.
Perforation Cavity Stability: Comprehensive Laboratory Experiments and Numerical Analysis
Authors: Tronvoll Johan , Morita Nobuo , Santarelli F. J.
Published: December 2007

The paper describes comprehensive laboratory and numerical studies of perforation cavity stability and sand production from a perforation tunnel. Jacketed cores with a cavity simulating a perforation tunnel were loaded in a high-pressure vessel and fluid flow was applied. The cavity deformation and failure were monitored by a cantilever deformation gauge, while produced sand was monitored acoustically and volumetrically at the outlet of the cavity. A cavity stability analysis was conducted using a 3D non-linear finite element model.

The numerical analysis shows that the onset of limited sand production matches the initiation of shear failure at the cavity wall. However, the perforation cavity is still relatively stable in the sense that it does not collapse. The sand production increases with the expansion of the post-failure zone, and the cavity finally collapses if excessive confining load is applied to the sample. The post-failure mechanisms are critical with respect to cavity collapse and sand production problems, which may explain the discrepancy between experimental and analytical results.
Indigenous Microorganisms in Connate Water of Many Oil Fields: A New Tool in Exploration and Production Techniques
Authors: Bernard F. P. , Connan Jacques
Published: December 2007

A microbiological investigation was carried out on 66 water samples taken from producing wells on 24 oil fields. The fields were all of a different nature and located in different places. Many of the samples contained microorganisms and it has been demonstrated that some of their associations do really originate in the connate water concerned and often contain unknown species.

These bacteria differ according to the nature of the geological formations and to the physico-chemical state of the water and the oil found in the various reservoirs. The nutrients which they need and the products of their metabolism thus vary substantially. They have been able to modify the state of oil and gas accumulations quite considerably and may continue to do so.

The result is that practical applications can already be established and there are many other potential uses. Some of them concern exploration and, by analogy, can be used to improve the rate of discovery. Others give rise to the reappraisal of certain aspects of reservoir management, in particular that of biodégradation of hydrocarbons and the aquifer regime. Other aspects concern production and the protection of installations, i.e. the fight against biocorrosion and souring.
Case Histories of Low-Cost Sand Consolidation in Thermal Wells
Authors: Shotts N. J. , Surles B. W. , Fader P. D.
Published: December 2007

A new sand control technology has been developed, patented,1,2 and successfully applied in the Kern River Field, Bakersfield, California, using a modified furan resin. The chemical system is very low cost, thermally stable to 700 °F and does not reduce gross production. It is environmentally safe and inert to oilfield chemicals.

The sand control process involves consolidating formation material during steam stimulation of a well by injecting the treatment chemical mixed with catalyst into the steam. After the steam diluted chemical travels downhole, polymerization occurs on the formation sand grains. Consolidation is completed within a few minutes. Additional shut-in time is not required; the well can be returned to production immediately.

Following successful lab testing3, field tests were conducted in the Kern River Field, Bakersfield, California, using both model test wells and active production wells. The tests determined the optimal treatment conditions for the process. To date, over 100 producing wells have been treated. Results indicate the process reduces sand production and operating costs without reducing gross production.
Sand Control in Wells With Gas Generator and Resin
Authors: Dees J. M.
Published: December 2007

Case histories of 22 treatments with a very new sand control procedure applied in Oryx Energy Company wells are reviewed. An acid curable resin is positioned in the casing across the perforated interval in an incompetent sand formation. A gas-frac propellent tool is placed in the resin. The propellent is fired to generate gas and drive the resin from the casing and into the formation outside the perforations. Resin remaining in the casing is displaced with gas or water to establish permeability to the non-resin phase and subsequent acid overflush ensures set of an oil-wet coating of hard plastic which acts as an external sand control screen. In addition, production rate from the well is frequently stimulated, apparently because fracturing pressures from the gas generator surge perforations clear of formation sand during the resin placement.
A New Solvent for Oilfield Scales
Authors: Paul J. M. , Fieler E. R.
Published: December 2007

Mobil has developed a new solvent to dissolve oilfield scales, including sulfates of barium, strontium and calcium, as well as calcium carbonate. Naturally occurring radioactive material (NORM), which is usually co-precipitated with barium and strontium sulfates, is removed by this solvent. Performance features of the solvent and case histories of field tests are reviewed. Materials compatibility with the solvent and disposal options are also briefly discussed.
High Fracturing Pressures for Shales and Which Tip Effects May Be Responsible
Authors: Gardner D. C.
Published: December 2007

Frequently, net treating pressures (pressure in excess of closure stress) observed during hydraulic fracturing, are significantly greater than what is predicted by industry fracturing simulators. Elevated net pressures have been attributed to various fracture tip phenamena, some of the more popular of these being: 1. high fracture toughness, 2. "dry zone," a zone near the fracture tip where injected fluid is excluded, 3. non-linear or inelastic effects resulting in dilation or reduced fracture widths.

A study of the above effects on fracture widths and pressures was conducted for symmetric radial ("penny") fractures. A rigorous solution method was developed which permitted characterization of the extent of a "dry zone" and it’s effect on width and pressure. Results indicate that the size of this zone is largely controlled by the pressure within the zone and by the pressure gradient of the injected fluid that is next to it. Therefore, conditions which promote large pressure gradients such as high viscosity, large moduli and high injection rates, also create larger "dry zones." However, the width and pressure near the wellbore were found to be essentially independent of the size of the "dry zone."

The effects that dilatant behavior, possibly caused by plasticity or micro cracking, might have on elevating fracturing net pressures was simulated using an approximate inelastic solution. This solution method modifies the elasticity equation by a "stiffening" function to effectively reduce the width such that the greatest relative reduction occurs near the crack tip. Net pressures and widths near the wellbore can be considerably greater than those obtained with the elastic solution (widths are still greater even in those cases where toughness is elevated to match the net pressure). Bottom hole pressure data was obtained during extensive fracture testing of shales/mudstones in the North Sea. A radial fracturing model simulating inelastic conditions, was found to better predict fracturing pressure responses than its elastic counterpart.
Recovery Optimization in a Multi-Reservoir Offshore Gas Field With Water Influx
Authors: Hower T. L. , Lewis D. R. , Owens R. W.
Published: December 2007

A detailed engineering and geologic evaluation of an offshore Gulf Coast gas reservoir with water influx is presented. The study was undertaken to analyze various production management strategies in order to optimize the ultimate recovery of the reservoir given the detrimental effects of the water influx.

Without implementing any reservoir management techniques, the recovery factor of the reservoir is estimated at 66%, much lower than would be expected under volumetric depletion performance. It is demonstrated that producing high volumes of water from downdip wells and adding an additional well high on the structure can significantly increase the ultimate gas recovery from the reservoir. This is achieved by lowering the reservoir pressure which liberates trapped residual gas and by recovering mobile attic gas. However, accelerated gas production does not appear to be beneficial in this particular case due to a reduced volumetric sweep efficiency associated with the accelerated rate case. Economic analyses show that recompletion of an additional well at a higher structural position is the optimum strategy for this particular reservoir. Due to the limited extent of the aquifer, this single well will effectively lower reservoir pressure, liberate gas trapped at residual saturation and recover mobile gas remaining at the top of the structure.
An Integrated Approach To Evaluate the Upside Potential of a Mature Field, Countyline Unit, Sho-Vel-Tum Field, Oklahoma
Authors: Zambrano L. G. , Killberg G. C. , Kendall J. J.
Published: December 2007

Significant additional oil potential has been identified in the Countyline Unit, Sho-Vel-Tum field, Oklahoma. The study is an integrated multidisciplinary approach which incorporates: 3D seismic to define the reservoir structure and fault blocks; detailed reservoir characterization to define the geometry and internal architecture of each "flow unit" in each fault block; numerical simulation to determine reservoir performance and optimum recovery strategy.
Performance and Analysis of Three-Phase Capillary Pressure Curves for Drainage and Imbibition in Porous Media
Authors: Kalaydjian F. J-M.
Published: December 2007

Three-phase capillary pressure curves measured in both drainage and imbibition on an outcrop water wet sample and on unconsolidated water wat cores, under ambient conditions, are presented.

These measurements show that both drainage and imbibition capillary pressures depend on the three saturations.

The impact of the spreading coefficient S, measuring the ability for oil to spread on water in presence of gas, on three-phase capillary pressure curves is shown.

Its effects on both drainage and imbibition capillary pressure curves are quantified and supported by pore scale experiments performed in glass capillary tubes and in glass network micromodels.
Improving the Centrifuge Technique by Measuring Local Saturations
Authors: Chardaire-Riviere Catherine , Forbes Pierre , Zhang Jian Feng , Chavent Guy , Lenormand Roland
Published: December 2007

A significant new improvement in the centrifuge method is proposed. It consists in continuously recording the local saturation variation by using an ultrasonic device at different locations along the core, while centrifuging at any given time.

The experimental procedure consists in recording flight times of ultrasonic waves at three locations along the core and then determining local saturation by a simple specific calibration, which leads to correspondence between the ultrasonic signal and saturation.

By using this procedure, direct determinations of oil/brine capillary pressure curves are obtained by studying equilibrium regimes. Meanwhile, local saturation measurements make it possible to investigate the transient regime in order to compute relative permeability curves. Then relative permeability curves are estimated by using a least-squares technique.

The relative permeability curves representative of the centrifuge experiment are in good agreement with the curves obtained by using the unsteady-state technique for a sandstone sample.