bluuebunny/crossref_metadata_2025 huggingface dataset:
Details of In-Situ Foam Propagation Exposed With Magnetic Resonance Imaging
Authors: Wassmuth F. R. , Green K. A. , Randall L.
Published: December 2007

This paper demonstrates the application of magnetic résonance imaging (MRI) to steady- and unsteady-state foam flow in porous media. Foam corefloods with and without surfactant preadsorption are discussed. The MRI instrument proved to be a useful tool in determining the in-situ saturation distributions during foam-flow experiments, with resolutions unmatched by other imaging techniques.
An Approach to Simulating the Effects of Water-Induced Compaction in a North Sea Reservoir
Authors: Cook C. C. , Andersen M. A. , Halle G. , Gislefoss E. , Bowen G. R.
Published: December 2007

Rock-compaction drive under waterflood re-pressurization has not been accounted for previously in our flow-model studies for a Valhall waterflood. However, field observations from pilot water-floods indicate an increase in permeability with the injection of cool seawater into the chalk formation. Platform subsidence measurements taken during the pilot waterflood also provide evidence of a chalk/water interaction. Laboratory experiments on reservoir core samples indicate an accelerated compaction effect as the flood front passes through the sample. To assess the value of a large-scale waterflood at Valhall, we have developed a new approach to simulate the possible effects of water-induced rock compaction in our black-oil flow models.
Interpretation of Three-Phase Relative-Permeability Measurements by Front Tracking
Authors: Haugse Vidar
Published: December 2007

A new algorithm for analysis of laboratory experiments with flow of three phases through a porous medium is presented. The method is based on discrete measurements. Saturation and fractional-flow profiles that exactly match the measured recoveries are constructed from measured average fractional-flow values. The profiles are piecewise constant in the part of the solution that reaches the outlet during the experiment. The total mobility along the saturation path is estimated from the measured pressure drops. Application to synthetic examples and measured data show that the method is a powerful tool to estimate relative permeabilities along the saturation path of an experiment.
Using an Electrochemical Approach for Monitoring Kinetics of CaCO3 and BaSO4 Scale Formation and Inhibition on Metal Surfaces
Authors: Morizot A. P. , Neville A.
Published: December 2007

To date, much emphasis on scale-inhibitor evaluation and the study of scale kinetics has been carried out using static beaker tests. This paper describes the use of an electrochemically based technique that allows the extent of scaling on a solid surface to be determined in the presence and in the absence of scale inhibitor. The ability of the technique to provide kinetic information on surface scaling will be demonstrated with two common varieties of scale. A comparison is made between surface- and bulk-scaling kinetics. Finally, the potential for this technique as a method for online monitoring of scale formation downhole will be discussed.
A Simplified Method for Calculating Temperature Changes in Deep Wells
Authors: Romero-Juarez A.
Published: December 2007

Knowledge of temperature is important when estimating correctly the amount of additives to add to stimulation fluids and for calculating accurately tubing movements and thermal stresses in casing. This paper describes a fast method for determining temperature along the well using a pocket calculator. This simplified method can give the same temperature distributions as the more elaborate method.

Introduction

Temperature is an important parameter that determines the producing possibilities of a reservoir. Many papers with different objectives have been written regarding well and formation temperatures. Several papers focus on the determination of location and distribution of injected fluids in the formation. Other papers investigate the effect of injected fluids on formation temperature.Determination of temperature along the wellbore is important for several reasons. First, we need to know the temperature of the injection or stimulation fluids at the formation face, and second, we must evaluate the linear changes and stresses on tubing caused by the decrease in temperature when a well is converted from producer to injector, or when a well has to be stimulated. Many operating problems occur because of thermal effects: buckling of tubing, casing stress, and troubles when unseating packers. Particularly, after a deep well stimulation, accurate changes in tubing length must be known, since this may be decisive for a successful treatment. Moss and White, and Ramey, conducted important studies on temperature in injection wells. Ramey's paper has become a classic and many studies dealing paper has become a classic and many studies dealing with temperature effect on pipe movement refer to this paper.The effect of well temperature and pressure on stress and pipe movement is discussed by Matson et al., Lubinsky et at., and recently by Hammerlind . These and other papers where calculation of well temperature is necessary (as in Ref. 11) usually refer only to Ramey's study and do not give enough detail to apply the method easily. Even when information is complete, such as in Matson et al., it is heavily condensed and calculations are very difficult for most field engineers. A method for performing these calculations quickly would be helpful performing these calculations quickly would be helpful when evaluating well-temperature profiles for both injection and producing wells. Calculations using this method could be performed with a pocket calculator.This study relies a great deal on Ramey's paper and on data from Ref. 1.

The Simplified Method - Well Stimulation

In 1961, Ramey solved (with certain assumptions) the problem of distribution of transient temperature along a problem of distribution of transient temperature along a wellbore. For injection wells, the solution is expressed by the following equations, which may be adapted to the case of stimulating wells down tubing.

JPT

P. 763
Collecting Human-Factors Data From Accidents and Incidents
Authors: Gordon Rachael , Flin Rhona , Mearns Kathryn
Published: December 2007

To investigate human and organizational factors in offshore accidents, two human-factors incident reporting forms were developed and evaluated. The Open Reporting Form (ORF) contained 11 open questions and the Comprehensive Reporting Form (CRF) contained 166 questions/potential causal categories. Both forms were tested on five U.K. offshore installations where personnel involved in an incident were asked to complete one. Using statistical techniques, the form with more structured questions was found to provide 66% more information than the participating company's existing reporting form. Results of the research are described focusing on potential benefits for the offshore oil industry.
Candidate and Chemical Selection Guidelines for Relative Permeability Modification (RPM) Treatments
Authors: Mennella Aniello , Chiappa Luisa , Lockhart Thomas P. , Burrafato Giovanni
Published: December 2007

Water shutoff treatments with polymers that selectively reduce the water permeability can be effective at reducing water production from hydrocarbon wells that cannot be treated with conventional approaches. This paper describes the elaboration of understanding-based rules for candidate and chemical selection to guide the application of this technology in the field. These rules are based on an analysis of the principal operative issues and on experimental and simulation studies that explore the physical and chemical mechanisms governing treatment efficacy.
A Dynamic Plunger Lift Model for Gas Wells
Authors: Gasbarri Sandro , Wiggins Michael L.
Published: December 2007

Many low-volume gas wells produce at suboptimum rates because of liquid loading caused by an accumulation of liquids in the well-bore that creates additional backpressure on the reservoir and reduces production. Plunger lift is an artificial lift method which can use reservoir energy to remove these accumulated liquids from the wellbore and improve production. Lacking a thorough understanding of plunger lift systems leads to disappointing results in many applications. This study develops a plunger lift model that couples the dynamic nature of the mechanical plunger lift system with the reservoir performance. The model takes advantage of previous work and incorporates frictional effects of the liquid slug and the expanding gas above and below the plunger. The model considers separator and flowline effects and includes modeling of transient production behavior after the liquid slug has arrived at the surface. An improved understanding of plunger lift dynamics can lead to improved efficiency, increased production and recovery, and extended well life.
Oil-Based Muds for Reservoir Drilling: Their Performance and Cleanup Characteristics
Authors: Davison J. M. , Jones M. , Shuchart C. E. , Gerard C.
Published: December 2007

This paper evaluates the performance of a standard oil-based mud (OBM) to drill horizontal wellbores, concentrating on its formationdamage characteristics and the flow-initiation pressures (FIP's) required for production to flow through the filter cake. For heterogeneous reservoirs, damage is relatively low in low-permeability rocks, but the FIP is high. Conversely, for high-permeability rocks, the FIP is low but formation damage is relatively high. If the drawdown pressure available from the reservoir is low, the scenario exists where inflow will occur predominantly from the higher-permeability formations, which could be damaged badly, but little inflow will occur from relatively undamaged lower-permeability rocks. In terms of maximizing production, this is obviously a less-than-optimal scenario.

Evaluations of cleanup fluids were conducted to gauge their effect on lowering the FIP of OBM filter cakes. Various fluids were screened for their mud-removal performance, which would indicate potentially good OBM "chemical breakers." Mud parameters such as oil:water (O:W) ratio, base-oil type, and emulsifier content all affected the efficiency of the cleanup fluids. The best cleanup fluids were used then in a series of core tests to evaluate their effectiveness in reducing the filter-cake FIP. Reductions between 25 and 40% were possible, although parameters such as soak time and overbalance pressure were critical to their success.
Performance Evaluation of a Mature Miscible Gasflood at Prudhoe Bay
Authors: McGuire P. L. , Spence A. P. , Redman R. S.
Published: December 2007

This paper summarizes the acquisition, conventional and compositional core analysis, and reservoir-simulation history match of a core taken roughly 300 ft from a production well in the most mature area of the Prudhoe Bay Miscible Gas Project (PBMGP). Compositional analysis of the core yielded a great deal of in-situ enhanced oil recovery (EOR) performance data and provided insights that could not be obtained from routine core analysis or production data. Fine-gridded reservoir simulations yielded a good match of the offset well-production rates and the observed compositional behavior of the core. The simulations and core data showed a complex layered displacement with alternating intervals of stripped and enriched oil. The data showed that roughly 70% of the cumulative EOR came from reducing the residual oil saturation near the injection well. The remaining 30% was caused by oil swelling.
The Magnetic-Resonance While-Drilling Tool: Theory and Operation
Authors: Prammer M. G. , Drack E. , Goodman G. , Masak P. , Menger S. , Morys M. , Zannoni S. , Suddarth B. , Dudley J.
Published: December 2007

The first Magnetic-Resonance-Image Logging-While-Drilling (MRI-LWD*) tools have been built and field tested. The hardware was designed to provide data that are compatible with the Magnetic Resonance Imaging Log (MRIL®) wireline tool in terms of processing and interpretation. This paper discusses the theory of robust MRIL measurements in the drilling environment and reviews the theory of 7 relaxation time measurements. We report on the results of a field test in the Gulf of Mexico. The MRI-LWD device logged the entire total depth (TD) run from casing to TD and provided additional hydrocarbon-typing data in wiping mode over the target zones. Wireline MRIL data and conventional logs were used to verify the MRI-LWD measurements.
Evaluating Hydraulic Fracturing in Cased Holes With Cross-Dipole Acoustic Technology
Authors: Tang X. M. , Patterson D. , Hinds M.
Published: December 2007

A cross-dipole technology was used to evaluate a carbonate formation in southeastern New Mexico to determine fracture trends in a waterflooded environment. The measurements were first made in open hole, then in cased hole before and after fracture stimulation. The cross-dipole data were processed to find the amount of shear-wave anisotropy and the associated azimuth. The results demonstrate that stimulated fractures create a substantial anisotropy and a well-defined azimuth behind casing. More important, by evaluating the anisotropy magnitude and azimuth from the cased-hole data, we can determine the fracture extent along the borehole and its azimuth in the formation. The fracture extent is also consistent with that from a radioactive tracer measurement. The results of this study suggest that cross-dipole acoustic logging is an effective technology for cased-hole fracture stimulation evaluation.
DDTW—A Method for Gas Reservoir Evaluation Using Dual Wait-Time NMR and Density Log Data
Authors: Thern Holger F. , Chen Songhua
Published: December 2007

Accurate estimates of porosity, fluid saturations, and in-situ gas properties are critical for the evaluation of a gas reservoir. By combining data from a dual wait-time (DTW) nuclear magnetic resonance (NMR) log and a density log, these properties can be determined more reliably than by either of the data alone.

The density and NMR dual wait-time (DDTW) technique, introduced in this paper, is applicable to reservoirs where the pore-filling fluid consists of a liquid phase and a gas phase. The low proton density of the gas phase causes a reduction in the NMR signal strength resulting in underestimation of the apparent porosity. The polarization for different wait-times depends on the spin-lattice relaxation time of each fluid and may cause additional NMR porosity underestimation. The density log, on the other hand, delivers a porosity that is overestimated because of the presence of a gas phase. These data, together with known correlations for gas properties, yield a robust approach for the gas-zone porosity, ϕ, and the flushed zone gas saturation, Sg,xo. DDTW also derives gas properties including the in-situ gas density, ρg, as well as the two NMR-related properties, hydrogen index, IH,g, and spin-lattice relaxation time, T1g. Two field examples illustrate the method, and an error propagation study shows the reliability of the technique.
Relative Permeability Measurements for Post-Waterflood Depressurization of the Miller Field, North Sea
Authors: Naylor Peter , Fishlock Terence , Mogford David , Smith Robert
Published: December 2007

This paper describes a determination of critical gas saturations and relative permeabilities relevant to the depressurization of the Miller field. A series of reservoir-condition coreflood experiments and associated numerical simulations is described. Three experiments were conducted with aged Miller core and fluids at 120°C. Each was comprised of a waterflood at about 414 barg, followed by depressurization at different rates. The laboratory data included extensive three-phase in-situ saturation measurements that were used to derive gas relative permeabilities through the simulations.

The rate-dependent critical gas saturations varied between 0.06 and 0.21, and gas relative permeabilities of the order of 0.0001 were deduced. These laboratory results are consistent with published data and suggest that conventional Corey-type gas relative permeabilities are an order of magnitude too large and do not represent the depressurization process.
Natural Backfilling of Pipeline Trenches
Authors: Fredsoe Jorgen
Published: December 2007

Fredsoe, Jorgen, Inst. of Hydrodynamics and Hydraulic Engineering, Technical U. of Denmark*

A theory, is developed for predicting the rate of natural backfilling of pipeline trenches through the action of waves and currents. The pipeline trenches through the action of waves and currents. The sedimentation originating from bed and suspended loads is studied separately. Four numerical examples demonstrate how to use the theory, which is verified by experiments.

Introduction

The aim of the studies presented here is to provide mathematical models for calculation of natural backfilling in pipeline trenches under the assumption that the seabed consists of noncohesive sediments and that the depth of the trench is small compared with the water depth (Fig. 1). The transportation of noncohesive sediment normally is separated into the transportation of bed and suspended loads. In many contexts, such a distinction of minor importance, but for our purpose it will be demonstrated that such a distinction is necessary. For example. the especially simple case where the alignment of the dredged trench is parallel to the direction of the current is considered. In this case, no suspended sediment is carried from the undredged regions to the trench by the current, if secondary currents are neglected. As long as the variations in water depth are small, the magnitude of secondary currents is negligible. However, while the suspended load is carried in the current direction, the direction of the transport of bed load deviates from the current direction because of gravity effect on the bed load moving on the slopes of the dredged trench. As a result. sedimentation will occur in the trench because of gravity infill of bed load.If the current crosses the trench under a certain angle, some suspended sediment also may settle because of decreasing current velocity and wave action at the bed in the dredged trench.From these considerations, one can see that the sedimentation caused by the bed and suspended loads must be treated separately because the physical background is quite different for the two sedimentation mechanisms.These two different physical processes are described for the case of current only and for the case of combined currents and waves. Numerical examples are given, and the magnitude of backfilling from the various processes is compared. A model test that supports the theoretical findings is described.

Sedimentation of Bed Load

Fig. 1 defines the velocity and concentration profiles and the bed geometry.

Current

The simplest case, where the current is parallel to the alignment of the trench, was treated in detail by Fredsoe . The continuity equation for the bed-load transport is given by

(1)

where Dt is the local depth of the trench, is the porosity of sediments, x1 is a coordinate in the transverse porosity of sediments, x1 is a coordinate in the transverse direction of the trench, and qx is the bed-load transport in the x1-direction, given by

(2)

JPT

P. 1223
Frac/Pack Modeling for High-Permeability Viscous Oil Reservoirs of the Duri Field, Indonesia
Authors: Fan Y. , White D. E. , Aimar A. , Satyagraha M. T.
Published: December 2007

This paper documents frac/pack completions conducted in the Duri field for the shallow, highly permeable, and unconsolidated formations containing heavy viscous crude. A treatment design model with a pressure-dependent leakoff option is presented to investigate effects of fracturing fluids, reservoir mobility, and Young's modulus on the fluid leakoff, net pressure, and fracture propagation. Field treatment data are analyzed with the provided model, and several factors that have significant influence on treatment results are discussed.
Professional Standards and Employment Conditions
Authors: Council Engineers Joint
Published: December 2007

This report comprises an analysis of problems of current employmentconditions as they relate to the individual engineer. The Engineers JointCouncil (EJC) is an organization composed of eligible professional engineeringsocieties, with each of these societies having appointed representatives whogovern EJC. The functions of EJC are: to act as an advisory and coordinatingagency to seek and study matters of mutual interest to the constituentsocieties; to represent the constituent societies when joint representationseems desirable; and administer activities authorized by the constituentsocieties.

Foreword

Unlike the members of most learned professions, the engineer usually is anemployee rather than a private practitioner. Surveys indicate that about 80 percent of professional engineers are in the employee classification, and thissituation sometimes creates special problems which are not inherent in theother professions. One such problem is how specifically to create and maintainan employment atmosphere consistent with high professional standards.

Certain conditions of employment have had a profound influence on engineersand, among other factors, have caused a number of professional employee groupsto turn to collective bargaining. There is a need, therefore, for theengineering profession to state clearly the employment conditions thatengineers expect as professional men. Employers should align their policieswith respect to the engagement of professional engineering personnel to meetthese expectations. Mutual understanding between employers of engineers and theengineering profession is essential to the establishment of an environmentwhich will encourage the individual engineer to achieve full professionalstature.

A special committee of Engineers Joint Council was charged with a study ofthis employment problem and the preparation for EJC of "a means ofeducation of and vertical communication to the membership of the constituentsocieties (including students) concerning conditions surrounding unionizationof professional personnel."

Another assignment of the special committee was the preparation ofinformation for employers of engineers concerning employment practices, educational opportunities, and general measures for professional developmentthat influence the attitudes of engineers toward a true professional outlook.This study treats but one of many problems confronting the profession.Engineers Joint Council will continue its study of the problem related to theemployed engineer.
Scale Effects on the Application of Saturation-Height Functions to Reservoir Petrofacies Units
Authors: Worthington Paul F.
Published: December 2007

An internally self-consistent reservoir model has been constructed to investigate the effects of scale on the numerical form and application of four saturation-height functions and on the resulting predictions of reservoir fluid saturations. The treatment uses reservoir partitioning into strongly characterized, physically distinct lithounits, or petrofacies, for purposes of petrophysical interpretation, and a separate, correlative reservoir zonation for subsequent parameter mapping and volumetrics. The context is therefore that of a deterministic reservoir model.

The numerical difference between apetrofacies-specific saturation-height function calibrated at the well-log scale (< 1 m) and the same type of function generated at the reservoir zonal scale (>10 m) varies with the function used and the physical character of the particular petrofacies unit. The application of saturation-height functions established separately at these two different scales has allowed the departures introduced through scale transgression to be assessed quantitatively. This has been done by comparing the predicted zonal hydrocarbon saturations generated for reservoir mapping with benchmark values of the same parameter. For this deterministic approach to reservoir description, an extended algorithm that uses bulk volume water as predictand provides the most accurate evaluation of water saturation at the reservoir zonal scale, which must be used in volumetrics applications. In contrast, an exponential form of the saturation-height function shows relatively large errors at both scales.

The significance and variability of scale effects have required the formulation of a structured approach to the optimum application of saturation-height functions in deterministic reservoir description. Through this facility, it is possible to contain the uncertainty associated with the distribution of hydrocarbon saturation at the reservoir mapping and volumetrics stages.
Effects of Discontinuous Shales on Multizone Steamflood Performance in the Kern River Field
Authors: Williams Lee. L. , Fong William. S. , Kumar Mridul
Published: December 2007

Steamflood performance of the Monte Cristo I lease in the Kern River field was analyzed with a detailed, 18-pattern, heterogeneous model incorporating all reservoir zones. Results were used to improve reservoir management, quantify the impact of discontinuous shales on oil recovery from individual zones, determine interzone gravity drainage, and identify bypassed oil zones for future infill drilling.

Results show that detailed modeling provides a more realistic description of actual performance. Furthermore, small pattern-element or single-sand models used in previous steamflood studies are inadequate for such reservoirs. Calculated oil recovery and temperature profiles compare well with field data. Discontinuous shales allow significant oil drainage to occur from the upper to the lower sands. As a result, the upper, unsteamed zones contain less reserve than expected. On the other hand, the lower zones continue to produce long after steam injection into the zone has stopped, giving high apparent recovery. The multipattern, heterogeneous model also may be used to identify bypassed zones for future infill drilling.
Prediction of Oil Recovery by Waterflood - A Simplified Graphical Treatment of the Dykstra-Parsons Method
Authors: Johnson Carl E.
Published: December 2007

Introduction

A method for predicting waterflood oil recovery was reported by H. Dykstra and R. L. Parsons in 1950. It is now generally known as the Dykstra-Parsons method and is widely used by petroleum engineers.

The method is semiempirical and consists of a correlation of four fundamental variables. These are: V, vertical permeability variation; a, mobility ratio; Sw, initial water saturation; and R, fractional recovery of oil in place at a given producing water-oil ratio. The correlation extends over a wide range in each of these variables, and may be applied to all formations with initial oil saturations of 45 per cent or greater.

The method of calculation originally outlined by Dykstra and Parsons closely follows their derivation. And this is a convenient way of illustrating the development of some rather complicated ideas. However, in actual use it is more cumbersome than necessary. The purpose of this note, therefore, is to provide a simplified method for making Dykstra-Parsons predictions.
A Literature Analysis of the WAG Injectivity Abnormalities in the CO2 Process
Authors: Rogers John D. , Grigg Reid B.
Published: December 2007

This paper summarizes the hypotheses and theories relating to the causes and expectations of injectivity behavior in various CO2 and gasflooded reservoirs. The intent of the paper is to:

Provide a concise compendium to the current understanding of the water-alternating-gas (WAG) mechanism and predictability. Provide a comprehensive single-source review of the causes and conditions of injectivity abnormalities in CO2/gasflood EOR projects. Aid in formulating the direction of research. Help operators develop operational and design strategies for current and future projects, as well as to input parameters for simulating current and future projects.
A Model Study of Iceberg Scouring in the North Atlantic
Authors: Chari T.R.
Published: December 2007

A model has been developed to predict the maximum depth of iceberg scour in the north Atlantic Ocean. A prior knowledge of the environmental parameters: -such as the bathymetry, seabed properties, iceberg dimensions, and Ocean current data would be required to compute safe burial depth for blowout preventer stacks and pipelines.

Introduction

The seasonal presence of icebergs on the Canadian east coast is a potential threat to any possible production of offshore oil or gas. With the recent discovery of oil on the Grand Banks1 and promising results on the Labrador Shelf,2 solutions to the iceberg problem have to be found speedily before production can commence. Existing technology must be improved or new techniques devised for operations in these iceberg-infested waters. Atlantic icebergs appear in different shapes and usually weigh millions of tons. Underwater depths (drafts) as much as 500 ft (150 m) are common for such bergs. Conventional gravity or jacket-type production platforms are not likely to withstand a direct hit from a drifting iceberg unless protected by auxiliary structures3 or artificial islands.

An iceberg drifting freely will tend to ground in the course of its travel when the bathymetry changes either gradually or abruptly, causing the water depth to be shallower than the draft of the berg. Bottom scours as deep as 21 ft (6.4 m) and as long as 9,850 ft (3 km) have been measured4 off the Newfoundland coast. Thus, buried offshore installations such as foundations and pipelines are susceptible to damage and are likely to be torn out by bottom-dragging and scouring icebergs unless buried sufficiently deep. Alternative production systems such as a floating rig in combination with various forms of subsea installations currently are being examined1 by the oil industry. A drillship likely to be in the path of a drifting iceberg can be moved off location by disconnecting the riser pipe. If the iceberg is large, the blowout preventer (BOP) stack itself could be knocked off or scoured out by the berg. Duval5 has reported that an iceberg forced the drillship Pelican to disconnect below the BOP stack during the 1973 drilling season. Even if safe methods are available to avoid a direct hit from an iceberg by moving the rig away from the collision course, gouging icebergs still would be a problem unless ocean-bottom structures are buried sufficiently deep. This paper describes a mathematical model and the associated laboratory tests for estimating iceberg scour depths.

Methods of Estimating Scour Size

It is believed that as many as 40,000 icebergs are produced6 yearly from the Greenland glaciers. They drift along the west Greenland and Baffin Island coasts (Fig. 1) and finally are caught in the Labrador current. In this process a large number of bergs are trapped in the bays and coastal indentations en route and grounded permanently. About 2,500 bergs are believed7 to cross the 60th parallel each year. A detailed description of the iceberg production, drift, and decay is given by Smith8 and reviewed by Chari.9
Development of a Generalized Darcy Equation
Authors: Tek M.R.
Published: December 2007

General equations relating the pressure drop necessary to sustain the flow of a fluid through a porous matrix at a given rate have been developed. The results indicate that at high values of flow rate the pressure-flow behavior may not necessarily satisfy the usual Darcy equation.

The mathematical analysis, carried through the micro-pore geometry and extended through the macro-reservoir scale, indicate that Darcy's law, of limited applicability to certain ranges of Reynolds numbers, can be generalized through the inclusion of some additional parameters.

The "generalized Darcy equation" has also been formulated in dimensionless form permitting the evaluation of its predictive accuracy with regard to literature data.

A comparison between predicted and experimental values indicates that the generalized Darcy equation predicts the pressure drops with good agreement over all possible ranges of Reynolds numbers.

Introduction

The limits and the nature of validity of Darcy's law has been a subject of every-day interest to the industry for many years.

It is well known that as the Reynolds number, characteristic of the fluid flow through porous media, becomes large, Darcy's law gradually loses its predictive accuracy and ultimately becomes completely void. For the last 20 years much has been said and written on this subject. Unfortunately little has been accomplished to bring about a satisfactory agreement, at least on the nature of the threshold of validity of Darcy's law. Fluid dynamists, geo-physicists, and engineers all had their individual views, explanations, interpretations and concepts on the subject. To some, a mechanistic analogy with pipe-flow proved a satisfactory explanation. To others, turbulence, in its random character, was incompatible with the geometric structure of consolidated porous systems. To some, turbulence merely represented a factor influencing the permeability measurements and again to others, empirical or semi-empirical correlations proved satisfactory from an engineering viewpoint.

Deviations from Darcy's law at high flow rates have been studied by systematic experiments by Fancher, Lewis, and Barnes. In an article on the flow of gases through porous metals, Green and Duwez conclude that the onset of turbulence within the pores appears unsatisfactory to explain deviations from Darcy's law. This view is held by many others.
High-Temperature Blowdown Experiments in a Vuggy Carbonate Core
Authors: Dehghani Kaveh , Kamath Jairam
Published: December 2007

We conducted a series of tests on a vuggy carbonate core sample to quantify recovery mechanisms during a high-temperature blow-down process. We heated the core to 300°F, keeping the pressure above the bubblepoint, and then reduced the pore pressure at a constant rate from one end of the sample. Tests were conducted with the core at initial oil saturation, Soi, and at residual oil saturation, Sor, to water, with pressure reduction from top or bottom of the sample. The blowdown experiments show that 50 to 68% of the oil is recovered, with 8 to 20% owing to thermal expansion, 20 to 24% owing to thermally enhanced solution gas drive, 12 to 16% owing to distillation, and 8 to 10% owing to in-situ steamdrive.
Wall-Effect/Gel-Droplet Model of Disproportionate Permeability Reduction
Authors: Liang J. , Seright R. S.
Published: December 2007

Many polymers and gels can reduce the permeability to water more than they can the permeability to oil or gas. However, the mechanism of this disproportionate permeability reduction is not clear. This paper considers a promising potential explanation that is based on a combined "wall-effect" and "gel-droplet" model. Many aspects of the disproportionate permeability reduction can be explained by a wall-effect model if the gelant is prepared from or matches the wetting phase, and by a gel-droplet model if the gelant is prepared from or matches the nonwetting phase. The combined model predicts that disproportionate permeability reduction should increase with increasing residual nonwetting-phase saturation. New experimental results support this prediction.
Regional Upscaling: A New Method To Upscale Waterflooding in Heterogeneous Reservoirs for a Range of Capillary and Gravity Effects
Authors: Coll C. , Muggeridge A. H. , Jing X. D.
Published: December 2007

This paper presents a new, two-phase upscaling methodology hereafter referred to as "regional" upscaling. A fine-grid flow simulation is performed on a representative section of the reservoir. Dimensionless numbers are then calculated for each fine-grid cell to determine the dominant flow regime in that cell. The coarse grid is selected based upon the spatial locations of the different force regimes observed in the fine-grid simulation model. Two-phase upscaling is then performed from the fine to the coarse grid using the most appropriate pseudoization technique [Kyte and Berry or vertical equilibrium (VE)] for the dominant flow regime in each region. The method is compared with different global pseudoiza-tion methods and its accuracy examined for a range of different heterogeneity models, including one for a reservoir in Lake Maracaibo in western Venezuela.
Advances in Coupled Geomechanical and Reservoir Modeling With Applications to Reservoir Compaction
Authors: Settari A. , Walters Dale A.
Published: December 2007

Coupled geomechanical and reservoir modeling is becoming feasible on a full-field scale. This paper describes the advances of the coupled model described previously,1 its extensions for modeling compaction, and the application of the model in full-field studies.

The advances of the theory and numerical implementation since the original work1 make it practical to perform full-field coupled studies with complex, realistic descriptions of the geomechanical behavior of the reservoir and shales, which allows prediction of stress changes, reservoir compaction, and surface subsidence. These capabilities are demonstrated in field examples that analyze and predict classical pressure-induced compaction in a gas field and thermally induced compaction in a heavy-oil field. In both cases, the methodology of interpreting the geomechanical laboratory and field data and their integration in the coupled modeling process was the key to obtaining a realistic predictive tool. The examples demonstrate that the technology is maturing to the point that conventional studies can be converted to coupled modeling on a fairly routine basis.
A Centrifuge Core Cleaner
Authors: Conley Francis R. , Burrows David B.
Published: December 2007

Introduction

A prerequisite to the evaluation and management of oil properties is accurate information derived from the analysis of core samples; but reliable data, such as porosity and permeability, can result only if all oil and water have been removed from the core samples analyzed. The most common method of core cleaning used to date has been Soxhlet extraction - a somewhat static technique, which depends upon the slow diffusion of hot solvent through the core sample. Soxhlet extraction performs satisfactorily only with highly permeable samples and at best requires long cleaning periods.

The centrifuge method was developed in 1951 by Continental Oil Co. to overcome the inefficiencies inherent in the Soxhlet method. The new method is basically an operation in which hot solvents are caused to flow through the samples under the influence of centrifugal force.

The centrifuge unit has proved so successful that samples which formerly required days for partial extraction can now be completely cleaned in approximately one hour.

The original idea was conceived in 1950 by Elmer S. Messer, whose early experiments consisted of flowing solvent over sandstone samples suspended in a revolving basket and driven by a vertically mounted vacuum cleaner motor. Results were so outstanding that more permanent units were constructed.

A modified model using this basic design was recently built by Core Laboratories, Inc., and is now used regularly in their operations.

Design

Fig. 1 shows a photograph of the two extractors routinely used to clean small core plugs in the Production Research Div. of Continental Oil Co.'s Ponca City laboratories. For illustrative purposes, the basket from one of the units has been removed, and because both extractors are of identical design only one is described in the following discussion. Each extractor unit consists of a centrifuge and a solvent still.
Aspects of Multicomponent Resistivity Data and Macroscopic Resistivity Anisotropy
Authors: Schoen J. H. , Yu Liming , Georgi D. T. , Fanini O.
Published: December 2007

New induction-logging hardware makes it possible to obtain both resistivity and resistivity-anisotropy data. Resistivity anisotropy, the ratio of vertical to horizontal resistivity, is the macroscopic effect of thinly layered formations in which logging tools have insufficient vertical resolution to properly resolve the individual beds, or laminae. Generally, there are two special types of layering.

Laminated shaly sands. The sediment consists of thin-bedded sand/shale sequences (anisotropy in these sands originates from the contrast of shale and sand resistivity). Finely layered anisotropic sands. The sand is composed of layers of different grain sizes/sorting (anisotropy in these sands originates from the resistivity contrast associated with the different water saturation).

The interpretation of conventional resistivity data is well understood. However, interpretation of vertical resistivity and resistivity anisotropy is not well understood and is often counterintuitive. We have used forward modeling to illustrate the effects of porosity variability in layered formations. For example, we have investigated the porosity-layering effect, which varies from an average porosity of 20 p.u. by +/− 5, 10, and 15 p.u. Three types of layering were considered: graded bedding and square- and sin2-porosity variation with depth. The modeling shows that sharp bed boundaries create the maximum resistivity anisotropy for any two component resistivity distributions.

The new induction-logging hardware comprises three mutually orthogonal, transmitter-receiver coil configurations that measure all data necessary to derive both resistivity and resistivity anisotropy of the formation in vertical, deviated, and horizontal wells. Simple models illustrate the physics, and the tools' capabilities are demonstrated with a synthetic example. Based on the petrophysical analysis of porosity contrast and layering type, a resistivity model is constructed, and the tool responses of this model are computed. With inversion techniques, both resistivity and resistivity anisotropy can be recovered.
Understanding Fracture Performance by Integrating Well Testing and Fracture Modeling
Authors: Cipolla C. L. , Mayerhofer M. J.
Published: December 2007

This paper presents case histories and field data that detail the application of well test data to calibrate fracture models, understand fracture performance, and optimize treatment designs. The paper includes field results from gas reservoirs in the Rocky Mountains and west Texas. The case histories also illustrate the application of postfracture pressure-buildup data to identify reasons for fracture treatment problems and to confirm treatment success. The paper also includes a novel data set that illustrates fracture performance from a liquid CO2 stimulation (no sand, no water) in west Texas. The case histories illustrate the importance of integrating well test data with fracture treatment optimization, showing how this process can improve our ability to reliably make multimillion-dollar decisions concerning proppant selection and fracture treatment size.
Characterizing Curing Cement Slurries by Electrical Conductivity
Authors: Backe K. R. , Lile O. B. , Lyomov S. K.
Published: December 2007

Electrical conductivity is a parameter that can be used to monitor the entire hardening process of oilwell cement slurries. The theoretical relationship among conductivity, porosity, cement chemistry, and ion content is discussed. The theory is confirmed by experiments; the decline in the slurry conductivity is primarily a function of porosity decrease and, thus, the degree of hydration. The applied results show that the electrical conductivity of curing slurries reflects strength development and that rapid hydration will reduce the risk of gas migration.
Uncertainty in Production Forecasts Based on Well Observations, Seismic Data, and Production History
Authors: Hegstad Bjørn Kåre , Omre Henning
Published: December 2007

A stochastic model in a Bayesian setting, conditioned on well observations, seismic amplitude data and production history, is defined. Samples of reservoir characteristics and production forecasts from the posterior model are used to evaluate the impact of various observation types. Well observations are found to be important to production forecasts due to near-well conditioning, while seismic data impact facies geometries but not the production forecasts. Production history contributes significantly only if certain events, such as gas-breakthrough time, are observed in wells. A brute-force rejection sampling approach may work well if proper conditioning on well observations and seismic data is done.
Effect of Pressure Gradient and Initial Water Saturation on Water Injection in Water-Wet and Mixed-Wet Fractured Porous Media
Authors: Tang Guo-Qing , Firoozabadi Abbas
Published: December 2007

A systematic study of the effect of wettability and initial water saturation on water injection and imbibition is made in Kansas outcrop chalk samples. (Kansas outcrop chalk is very similar to the rock matrix of the North Sea fractured chalk reservoirs.) Water-injection tests were conducted at different pressure gradients to simulate the effect of gravity (that is, negative Pc) on recovery. Based on a large number of carefully conducted tests, the following conclusions are drawn:

Initial water saturation has a pronounced effect on water injection in an intermediate-wet chalk. This effect is much less pronounced for a strongly water-wet chalk. The effects are also in opposite directions. Pressure gradients (which simulate the negative Pc effect) have a very strong effect on water-injection performance in an intermediate-wet chalk.

Our interpretation of these experiments leads to the conclusion that recovery from the chalk reservoirs may be nearly independent of wettability state. The results from the experiments also reveal that there is no relation between laboratory measurements of spontaneous imbibition and field performance of mixed-wet reservoirs, even when the wettability state is perfectly restored in the laboratory.
A True In-Situ Fracturing Experiment Final Results
Authors: Parrish R.L. , Stevens A.L. , Turner T.F.
Published: December 2007

A true in-situ oil shale retort bed preparation experiment was performed by detonating an explosive slurry that had been displaced from well bores into preformed horizontal hydraulic fractures. The objective was to test this method for producing a distributed fracture network with sufficient void and permeability for retorting in a controlled manner. Numerous diagnostic and evaluation measurements were performed during the course of the experiment for initial site characterization, hydraulic fracture assessment, explosive displacement and detonation performance, and post detonation fracture and permeability assessment. Results show that fractures were induced; the fractures were found to be randomly distributed with no regions of extensive fracturing or shale dislocation. Enhancement of permeability was limited essentially to enlargement of the preformed hydraulic fracture horizons into which the explosive slurry was inserted and detonated. Successful retorting would be contingent on the ability to retort shale layers with random fractures but without significant permeability between the enlarged fractures.

Introduction

The potential advantages of true in-situ processing techniques, as compared with mining and surface retorting, for extracting hydrocarbons from oil shale have been recognized for many years. With such techniques, the only linkage between the underground shale bed and the surface is through a series of wells. Both the bed preparation and the retort processing phases are conducted from the surface through these wells. Resulting attractive features are that requirements for mining large quantities of raw shale and disposal of the spent shale are eliminated. Other environmental impacts, such as water requirements, may be reduced significantly.

In preparing an oil shale bed for in-situ processing, the naturally impermeable oil shale must be rubblized to introduce sufficient void and permeability. This permits process gases to flow from injection wells to the combustion front and permits product liquids and gases to flow from the pyrolysis zone to production wells during retorting. Past experiments1,2 have used variations of two basic methods (well bore springing and hydraulic/explosive fracturing) to fracture the shale bed and attempt to achieve the required void and permeability. The well bore springing method3 involves the detonation of explosive charges contained within the well, while the hydraulic/explosive fracturing method involves the detonation of slurry explosives that have been displaced from wells into preformed horizontal hydraulic fractures (hereafter called hydrofractures or simply cracks).