bluuebunny/crossref_metadata_2025 huggingface dataset:
Dielectric Log-A Logging Method for Determining Oil Saturation
Authors: Geng Xiuwen , Yong Yinzu , Lu Da , Zhao Shufang
Published: December 2007

This paper presents the principles of dielectric logging by describing measurement of phase shift. laboratory experiments, theoretical calculations for determining the vertical resolution and depth of investigation, and results of application in field practice.

Introduction

Measurement of oil saturation is an important pan of well logging in the development of- an oil field. It is an important basis for evaluating watered-out reservoirs, estimating the residual oil, and redividing and combining the productive zones. In the development of an oil field by water injection, the salinity of injected water always differs greatly from that of original formation water. For example, the salinity of original formation water in Daqing oil field is about 6,000 to 8,000 ppm, and the salinity of the injected water is as low as 500 to 800 ppm. Thus, the formation water gradually becomes less saline as the amount of injected water is increased. However, the resistivity log and the Neutron Lifetime Log- cannot be used to measure oil saturation in such strata. To solve this problem, it is necessary to introduce other logging methods for measuring oil saturation that are less influenced by the salinity of formation water. Dielectric constant logging is one method to solve this problem and has been described in U. S. and Soviet literature.

In the late 1960's, the study of dielectrologs was launched in Daqing oil field. Both theoretical and experimental studies on dielectrologs were carried out. Since 1974, the dielectrolog tool has been used in the field and has been run in more than 100 downhole operations. Field practice has proved that the accuracy for interpreting water saturation of formation and watered-out zones with dielectrolog is +/-8. 8% and +/-5. 7%, respectively.

Laboratory Experiment For Determining Dielectric Constant of Rocks

The dielectric constants for crude oil and minerals of sedimentary rocks are small (2 to 8), and that for water is very high (80). Therefore, the dielectric constant for water-bearing rocks depends mainly on its water volume. To verify the fundamental principle of this logging method, a laboratory study of main factors affecting the dielectric constant of rocks was performed with core samples from different oil-beefing zones in Daqing oil field. The frequency used here is 60 MHz. Fig. 1 gives the relationship between the dielectric constant and formation water volume of sandstone samples from different regions of Daqing oil field. Air saturation is used instead of oil saturation in these experiments. In Fig. 1 the dielectric constants of rocks correspond very well with the water volume. The dielectric constants of dry samples range from 4 to 7; those of rock matrix, oil, and air are rather small because they depend on shift polarization.

JPT

P. 1797^
A Comparative Study of the Characteristics and Susceptibility of Pattern-Type Water-Injection Well Networks From the Viewpoint of Balanced Waterfloods
Authors: Xian-zhang Tong
Published: December 2007

In"this paper, some standard geometrical flood patterns of "n-spot" are compared with each other on the basis of their respective susceptibility to the balance between total fluid injection and withdrawal rates by use of a basic parameter, Fm− the ratio between the average PI of production wells and the injectivity index of injection wells. The characteristic parameter. Fm, of a reservoir basically is dominated by the reservoir rock and fluid property as well as by completion practices.

Each pattern of well networks deserves preference under certain specific circumstances. All factors other than Fm being equal, the five-spot network offers greater total liquid deliverability when Fm lies within the range 1 to 1.5. When Fm is smaller than 0.5, the inverted nine-spot network begins to show its superiority.

Formulas and graphs showing relationships between n and Fm are presented for comparison and selection of optimal patterns for different circumstances.
A Thermodynamic Model for Low Interfacial Tensions in Alkaline Flooding
Authors: Sharma Mukul M. , Yen T. F.
Published: December 2007

Many experimental studies have been undertaken to measure interfacial tensions (IFT's) as a function of pH, salinity, temperature, and divalent ion concentrations. This behavior varies from one crude oil to another and is critical in determining its suitability as a candidate for caustic flooding.

A model based on a thermodynamic analysis of crude oil/caustic interfaces has been developed that predicts the IFT behavior of such systems. The model accounts for IFT variations with changes in pH, salinity, and temperature by using parameters that must be estimated from a preliminary experimental study. The model predictions compare well with earlier reported experimental results. It is shown that the application of such a model to empirical correlations for residual oil saturations and fractional flow curves enables us to predict the changes in the fractional flow and relative permeability curves for an alkaline flood with self-sharpening fronts if the injection pH and salinity are specified. The basic equations needed to extend this model to account for divalent ions and more complex flow systems are provided in the Appendices.
Stability of Aqueous Wetting Films in Athabasca Tar Sands
Authors: Hall A. C. , Collins S. H. , Melrose J. C.
Published: December 2007

The existence of thin films of water that completely wet the sand grains has long been regarded as an important feature of the Athabasca oil sands deposit. Direct microscopic evidence, however, cannot be relied on to establish whether such films are present, The existence and stability of such films, therefore, must be inferred from the relevant surface chemical forces for the oil/brine/rock system.

A detailed analysis of these forces shows that the stability of these thin wetting films is critically dependent on whether the zeta potentials (and charge densities) for the two electrical double layers bounding the film are of like sign. The zeta potential and charge density for the rock/brine interface will in almost all cases be negative in sign. Therefore, a requirement for the stability of a wetting film will be that these quantities are also negative at the brine/oil interface.

New measurements of the electrophoretic mobility of small particles of Athabasca bitumen suspended in an aqueous phase are reported. These data show that the zeta potential at the bitumen/water interface is strongly negative. Consequently, these results support the hypothesis that wetting films will be stable in this instance.
Effect of Groundwater and pH Modification on Quality of Leachate From Simulated In-Situ Retorted Utah Oil Shale
Authors: Bethea Robert M. , Barber Donald R. , Parker Harry W. , Guven Necip
Published: December 2007

Major variables reported in this study were retorting temperature, retorting atmosphere (inert, air added, air and CO2 added), and groundwater quality (source). All leaching tests were made at atmospheric pressure and most at room temperature. Leaching tests were made with groundwater to observe the ability of spent shale to remove materials from groundwater and the possible ability of those materials to plug the pore structure of the spent shale and to minimize further leaching. The factor having the greatest effect on leachate composition was retort temperature. The presence of CO2 during high-temperature retorting suppressed the amounts of base-forming materials generated. All bâchâtes were affected significantly by the groundwater used for leaching. As expected, more material was leached from the retorted Utah shale when the higher-purity groundwater was used.

The addition of 2% Wyoming bentonite for the purpose of pH modification to the groundwater used for leaching the retorted shale (780 and 1000 °C (1,436 and 1,832 °F) retort atmosphere of air with 15% CO2 added] showed that the bentonite had only a small effect on the leaching of monovalent cations and essentially no effect on the movement of the heavy, hazardous cations. The effect of retorting temperature was mixed with the exception of chromium, which increased four- to fivefold in the leachate.

The permeability of Utah shale was determined by retorting two cores from Rock 2 at 780°C (1,436 l;) for 48 hours in the presence of air alone. The differences in the Final permeability of these cores can be attributed to differences in groundwaters.
Completing High Pressure Gas Wells - Mechanics and Problems
Authors: Kilsdonk R.A.
Published: December 2007

Introduction

This discussion is limited to high pressure gas wells or wells with abnormal pressure gradients. It does not cover extreme high pressure gas wells such as have been recently completed on the Gulf Coast where shut-in tubing pressures have been recorded in the vicinity of 12,000 psi. It is realized that such wells would probably be of more singular interest; however, since relatively few have been completed to date, the data are very meager. It is the purpose of this paper to review some of the mechanics and problems involved in the completion of high pressure gas wells.

Generally speaking, completion practice refers to operations which take place from the time the well is drilled through the productive zones and continues until the well is placed on production.

The wells which will be discussed might be termed as medium high pressure gas wells having pressure gradients of about 0.8 psi/ft of depth. Three gas wells in this category were recently completed in the Gulf of Mexico approximately three miles off the Texas coast near Mustang Island. The completion of these wells will be discussed in detail.

Casing Program

The proper design of casing programs for high pressure gas wells is of utmost importance. This is particularly true of offshore wells where the safety of personnel and equipment is at stake. For this reason the factors of safety must be maintained well within the accepted limits. The program for all three offshore wells followed the same general pattern except for the 5-in. OD oil string. Due to trouble encountered with sticking in the deviated hole, the oil string was swaged to 4.5-in. OD at the bottom of the 7-in. OD casing at approximately 10,600 ft.

The typical program is shown in Table 1. Total average weight of tubular goods used in each well was 1,257,000 lb or approximately 628 tons. For the sake of simplicity the details of completion of Well No. A–3 will be discussed since all three wells were completed in the same manner.
Sand-Consolidation Resins—Their Stability in Hot Brine
Authors: Rensvold Roger F.
Published: December 2007

Four commercial in-situ sand-consolidation resin systems and one resin-sandpack system were tested for durability in hot [160°F (71.1°C)] flowing brine for up to 28 months, and in as much as 30 million PV brine. Brine was selected as the test fluid since it is considered to be more damaging than oil to the stability of resin-consolidated sand.

Two epoxy and two furan systems were investigated. Other commercial consolidation techniques—e.g., involving phenol formaldehyde and phenolic furan resins described in the literature1—have been recognized as effective sand-stabilization products; however, some limitations had to be placed on the scope of the study because of equipment and time limitations. Perhaps these techniques will be the subject of future investigations. Note that all processes evaluated in this investigation used silane coupling agents contained in the resinous materials. These agents increase the stability of sands consolidated by organic polymers.2

The overflush-catalyzed furan resin (System A) and the internally catalyzed epoxy resin (System D) demonstrated greater stability under the specific test conditions employed. System A retained higher strength during the first 15 million PV. Thereafter, System D appeared to be better. System A exhibited the highest initial permeability, and, after 5 million PV, Systems A, B, and D were about equal in permeability. From that point, the permeability of System A slowly increased, while decreasing for Systems B and D.

The epoxy-resin sandpack (40- to 60-mesh sand) showed little change in compressive strength after exposure to more than 30 million PV of hot, flowing brine.
High Pressure Cycling with Hydrogen Sulfide Laden Gas
Authors: Miller C.O.
Published: December 2007

Introduction

This paper describes the use of hydrogen sulfide laden gas in high pressure cycling in the New Hope, Smackover field located in Franklin County, Tex., some 50 miles north of Tyler. In Dec., 1953, Tidewater Oil Co. and Seaboard Oil Co. discovered the New Hope, Smackover field, underlying in part the New Hope oil field also discovered by these two companies in 1943.

The New Hope, Smackover gas-condensate reservoir was discovered by completion of the T. J. Ramey Unit 1–1-D well with open hole 12,086 to 12,322 ft. On test the well yield was approximately 150 bbl of "sour" condensate per million cubic feet of sour or hydrogen sulfide laden gas. This reservoir was discovered by deeper drilling on a known structure. Discovery well location was made on the basis of deep geophysical reflections.

Engineers have recently recognized that the so-called gas-condensate reservoir products actually exist in the formation in the gas phase. The condensate, as its name implies, is a portion of the liquefiable hydrocarbons whose recovery is accomplished by cooling or reducing the reservoir fluid pressure to a point within the retrograde condensate range.

One of the first questions to arise when a new gas-condensate reservoir is discovered is, What are the reserves? Other questions of equal importance arise. What plan of production shall be employed? Shall it be pressure depletion? Cycling? Or a combination of both? Certain economic and physical factors may alter an original plan of production during the actual producing period of a reservoir. It is probably safe to say all gas-condensate field production methods need to be constantly observed and periodically studied in detail to assure optimum production.
Rheology Enhancement by Molecular Association Complexes
Authors: Prud'homme Robert K. , Uhl Jonathan T.
Published: December 2007

Associations between polyethylene oxide polymer (PEO) chains and species containing sulfate groups can be used to increase the viscosity and elasticity of polymer solutions. The condensation of sodium dodecyl sulfate (SDS) micelles onto the PEO chain is shown to lead first to chain coil collapse and then to network or gel structure formation as SDS concentration is increased. Stronger interactions are produced between PEO and either Congo-red dye (a large organic molecule with two widely spaced sulfate groups) or polystyrene sulfonate (PSS). In these cases the association complexes lead to minor changes in the solution viscosity but large changes in the primary normal stress and storage modulus G′ at low frequencies. The structures formed by association are disrupted by flow but rapidly re-form. Association complexes are an attractive way of obtaining high-viscosity fluids that would be resistant to permanent shear degradation.
The Rules for Achieving High Solubilization of Brine and Oil by Amphiphilic Molecules
Authors: Bourrel M. , Chambu C.
Published: December 2007

The oil-recovery effectiveness of a chemical flood has been proved related to the phase behavior of the brine/oil/surfactant system. In particular, it is advantageous to formulate the system so that optimal three-phase behavior is obtained. However, it also has been demonstrated that all the optimized systems are not equivalent in terms of solubilization, interfacial tensions (IFT's), and oil-recovery efficiency.

This paper addresses the conditions that promote high solubilization in microemulsions, a property correlated to the values of the IFT and therefore correlated to the ability of such systems to displace the oil in porous media. When one formulation parameter is changed, another parameter must be varied at the same time for compensation to reoptimize the system. The mechanism of solubilization is investigated experimentally by considering the usual formulation parameters: salinity, oil type, alcohol type and concentration, and surfactant structure and type (anionics and nonionics). The results are interpreted in terms of interaction energies between surfactant, oil, and water. In particular, the role of the alcohol and its impact on the solubilization by amphiphilic systems are discussed in detail and interpreted.

Moreover, the concepts developed in this paper explain the effect of the surfactant structure and therefore aid in the design of amphiphilic molecules exhibiting a high solubilizing power for given conditions of brine, temperature, etc.
The Effect of Live Crude on Phase Behavior and Oil-Recovery Efficiency of Surfactant Flooding Systems
Authors: Nelson Richard C.
Published: December 2007

Neither pressure alone nor pressurizing with methane affects phase behavior of a particular surfactant/brine/stock-tank-oil system. Oil-recovery efficiency in corefloods is not significantly different whether the stock-tank oil is pressurized with methane or diluted with iso-octane to the viscosity of the live crude. In contrast, phase behavior and oil-recovery efficiency do change upon methane pressurization when a lower-molar-volume synthetic oil is substituted for the stock-tank oil. Some thermodynamic insight regarding the different behavior of the two oils is offered.
A Three-Parameter Representation of Surfactant/Oil/Brine Interaction
Authors: Puerto Maura C. , Reed Ronald L.
Published: December 2007

When optimal salinity, Cϕ, and solubilization parameter Vo/Vs are augmented by oil molar volume, Vmo, the resulting three-parameter representation provides a more precise description of microemulsion phase behavior than has previously been available. It then becomes possible to introduce the idea of equivalent oils (Eqo's) as a replacement for the equivalent alkane carbon number (EACN), which is shown to lack some of the properties needed to implement efficient preliminary screening of microemulsions for EOR.

Broadly speaking, oils are "equivalent" when they have the same molar volumes, optimal salinities, and solubilization parameters. If, in addition to equivalence, oils are required to have equal viscosities and similar phase behavior as a function of surfactant concentration, then it may be possible to replace microemulsion floods of live crude at high pressure with floods of appropriately diluted dead crude at low pressure.

This paper places EACN in perspective by means of the three-parameter representation, explores parallel effects of temperature and alcohol cosolvents, and reveals essential nonlinearities in optimal salinity as a function of oil composition (and hence molar volume) for mixtures of various oils. Much of this is subsequently used to develop methods for preparation of Eqo's and the more complex but evidently essential equivalent systems (EqS's) needed to model live crudes.
Magnitude and Detailed Structure of Residual Oil Saturation
Authors: Chatzis Ioannis , Morrow Norman R. , Lim Hau T.
Published: December 2007

Experimental results are presented that demonstrate the effect on residual oil, under water-wet conditions, of particle size, particle-size distribution, macroscopic and microscopic heterogeneities, microscopic dimensions such as ratio of pore-body to pore-throat size, and pore-to-pore coordination number. Experiments were performed in random packs of equal spheres, heterogeneous packs of spheres with microscopic and macroscopic heterogeneities, two-dimensional (2D) capillary networks having various pore geometries, and Berea sandstone. Detailed information on residual oil structure is presented, including blob-size distributions of residual oil. Major conclusions are (1) residual saturations are independent of absolute pore size, per se, in systems of similar pore geometry; (2) well-mixed two-component aggregates of spheres gave virtually the same residual saturations as random packings of equal spheres; (3) clusters of large pores accessible through small pores will retain oil; (4) high aspect ratios tend to cause entrapment of oil as a large number of relatively small blobs, each held in single pores; and (5) the role of pore-to-pore coordination number is generally secondary; hence, correlations that have been proposed between residual oil and coordination number are unreliable.
Heat Losses During Flow of Steam Down a Wellbore
Authors: Satter Abdus
Published: December 2007

Studies of wellbore, heat transmission during the injection of a hot fluid, as either gas or liquid, have appeared in the literature. The present investigation takes into account the effect of condensation, which is of practical significance when considering steam injection operations. Calculation procedures are given for superheated and for saturated and undersaturated steam. Effects of injection rate, time, pressure, temperature and depth of a well on heat losses have been analyzed. The benefits of using a packer are discussed. Also presented are correlations for estimating heat losses involved during injection of saturated steam.

Introduction

Studies of wellbore heat losses during the injection of a hot fluid have appeared in the literature. Ramey has presented a useful solution for calculating temperature of a heated gas as a function of depth and injection time. Ramey and others have also presented solutions for the hot liquid case. No method is available to take into account the effect of condensation, which is of practical significance when considering steam injection operations. This paper presents a method of estimating the quality of a condensing fluid as a function of depth and time. The approach is basically the same as that used by Ramey. The following injected fluids and conditions are considered in this study:Injection of superheated steamA. Decrease in temperature until cooled to thesaturated stateB. Condensation until condensed completely into hot(saturated) waterInjection of saturated or undersaturated steam;condensation until condensed completely into hot(saturated) water. Although this investigation does not include cooling of water after steam is completely condensed, Ramey's solution for the hot liquid case can be used for this purpose.

The effects of various process variables on heat losses during the injection of steam into a well are investigated.

THEORY QUALITY OF CONDENSING STEAM

Predicting the behavior of condensing steam flowing down the injection wellbore requires an estimate of the quality of steam, i.e., the mass fraction of vapor in the mixture. Let us divide the total depth of the injection well into several segments which might be, but do not have to be, of equal magnitude. Consider condensation within a given depth interval AZ, the bottom of which is located at a depth Z from the surface (Fig 1). The following equation, derived in the Appendix, relates the quality of steam at the bottom of an interval to that at the top of the interval:

(1)

(2)

(3)

See the nomenclature for symbol definitions. The major assumptions made in the solution are is follows:Steam is injected at a constant rate, wellheadpressure, temperature and quality.A down-hole packer is used to prevent steam from entering the tubing-casing annulus. The annulus is assumed to be filled with air at low pressure.

JPT

P. 845ˆ
Elimination of Xanthan Microgels by New Enzymatic Treatments
Authors: Kohler Norbert , Milas Michel , Rinaudo Marguerite
Published: December 2007

Polysaccharase and particularly combined polysac-charase/protease treatments offer new alternatives for clarifying aqueous xanthan gum dispersions. Each enzyme has its specific action—the proteases on the insoluble residual bacterial cells, and the polysaccharases primarily on the microgels.

Preliminary tests of these enzymatic treatments for scheduled field applications show promising improvements in filterability, especially for solutions prepared from xanthan powders.
Flooding of Semi-Depleted Solution Gas Reservoir in Fullerton Field
Authors: Nolan W.E. , Williams R.M.
Published: December 2007

Little flooding experience or technology exist which are applicable to solution gas-drive reservoirs which have been depleted considerably below the bubble point. The Fullerton field pilot is an example of flooding under these conditions where an intermediate stage or depletion exists and the water flooding will be neither a pressure maintenance project nor a depletion flood. In the case of Fullerton field where the gas saturation is approximately 18.0 per cent of total pore volume, "fill-up" will not be reached for a number of years after flooding operations begin. During this period compressibility of fluids and relative permeability factors determine performance of producing wells. The non-steady-state performance which will be in effect for a considerable time cannot be directly predicted by any presently accepted theoretical means.

The pilot flood has yielded considerable information which can be used in predicting performance during this important stage of flooding. The pilot has shown that favorable reactions on producing wells adjacent to injection wells are in effect long before a theoretical fill-up is obtained. This does not indicate poor performance, but merely that the reservoir fluids are compressed to the point where a significant oil bank is formed. This isolated pilot pattern flood, where all offset wells are producing, gives some indication of what might be expected under both pattern and line-drive flooding. The pilot has progressed to a point where sufficient stock-tank oil has been recovered, in the area under pattern flooding, to justify full scale flooding. In the area surrounding the pattern flood no means exist for confining fluid movement, and performance is a function of the interdependent combination of relative permeability, fluid saturation and fluid compressibility. This pilot flood has shown the degree to which outside offset producing wells respond prior to reaching gas-space fill-up and the degree to which productivity is affected by changes in saturation accompanied by only relatively slight pressure increase. Producing wells inside the pattern flood have shown the degree to which productivity can be affected by saturation change and a considerable increase in bottom-hole pressure.
Study of the Oil Wedge Phenomenon Through the Use of a Chemical Flood Simulator
Authors: Tham Min Jack , Nelson Richard C. , Hirasaki George J.
Published: December 2007

The presence of an oil wedge in some coreflood experiments indicates possible inefficient use of expensive surfactant mixture. The oil wedge problem his been studied in some detail by means of a chemical-flood simulator. Knowledge gained from this study will be useful in the design of future field-scale chemical floods.

The formation of an oil wedge in a chemical flood is caused by an unfavorable gravity override condition at the front of the surfactant bank and gravity underrun at the back side of the surfactant bank and by the limited availability of surfactant in the flood. Chemical-flooding systems that are Type III over a broad salinity range are less likely to form an oil wedge than systems that are Type III over a narrow salinity range.

The gravity override condition at the front of the surfactant bank may be improved by designing a chemical-flooding system that is Type III over a broad salinity range and that has a high upper Type III boundary on the salinity-requirement diagram. The gravity override condition can be improved also by preceding the chemical slug with a low-salinity preflood or by lowering the chemical-slug salinity.

The unfavorable gravity underrun condition at the back side of the surfactant bank can be improved by increasing the injection rate, by increasing the drive viscosity, by lowering the chemical-slug salinity, or by designing a better chemical-flooding system that has a broad Type III salinity range.
On-Site Acidizing Fluid Analysis Shows HCl and HF Contents Often Varied Substantially From Specified Amounts
Authors: Watkins David R. , Roberts Glen E.
Published: December 2007

A quality-control survey of 162 acidizing fluids revealed the following problems. problems.Acid concentrations were often too high or too low.Frequently, fluids were not thoroughly mixed.In some cases, fluids contained incompatible additives.

A field test kit and conventional laboratory analyses were used to determine the acid and iron concentrations in fluids from 44 acid jobs in southern California over a 4-year period. Results of the survey suggest that analysis of acid concentrations would enhance the quality of acidizing programs. The kit described here permits the simple and rapid analysis programs. The kit described here permits the simple and rapid analysis that would contribute to a quality-control program.

Introduction

Acidizing fluids are the product of research and field experience. Although laboratory tests contribute to the design of acidizing fluids, field tests and experience determine the final fluid composition. Once a fluid appears to work, it will be used routinely in a specific field. Routine use, however, does not ensure good acid quality. These fluids are complex mixtures that contain several critically active chemicals. One fluid may contain HCl, HF, acetic acid, corrosion inhibitor, antisludging agent, foaming agent, solvent or mutual solvent, sequestering agent, and other chemicals. Each one contributes a specific function and must be compatible with the others. The presence of these additives in proper concentration is always critical.

Therefore, we initiated a quality-control program for acids used in southern California. Our objective is to obtain the fluids we specify bychecking acid quality on the job to prevent the use of poor-quality fluids,defining quality control problems so they can be solved, andgiving the acid suppliers more incentive to control the quality of their fluids.

This paper presents the results of a 4-year quality control survey and a description of the kit used to analyze the fluids.

Description of the Acid Quality Test Kit

The test kit (see Fig. 1) permits rapid analysis of HF, HCl, and iron concentrations. Plastic labware is used almost exclusively in the kit to avoid the inconvenience of breakage in the field and to avoid contact of HF with glass. The HCl and HF concentrations in weight percent are determined by titration. Samples are titrated by using constant-volume dispensing bottles rather than a buret. These bottles accurately and reproducibly dispense 1-mL (1-cm3) quantities of the titrating solution; therefore, the analytical result is a concentration range rather than a discrete concentration. This range spans 0.4% for HF and 0.91% for HCl in the absence of HF. For example, in the HF titration each milliliter of titrating solution represents 0.4% of HF. If six 1-mL (1-cm3 ) quantities of the solution are required to reach the endpoint, the HF concentration is known to be between 2.0 and 2.4%.

JPT

p. 865
Laboratory Tests on Heavy Oil Recovery by Steam Injection
Authors: Closmann Philip J. , Seba Richard D.
Published: December 2007

This paper presents results of laboratory experiments conducted to determine the effect of various parameters on residual oil saturation from steamdrives of heavy-oil reservoirs. These experiments indicated that remaining oil saturation, both at steam breakthrough and after passage of several PV of steam, is a function of oil/water viscosity ratio at saturated steam conditions.
Experimental Studies of In-Situ Microbial Enhanced Oil Recovery
Authors: Jenneman Gary E. , Knapp Roy M. , McInerney Michael J. , Menzie D. E. , Revus D. E.
Published: December 2007

Experiments were conducted to study the feasibility of using microorganisms in EOR. particularly for the correction of permeability variation. The use of microorganisms requires the ability to transport viable cells as well as the nutrients required for cellular growth through reservoir formations. Nutrients such as glucose, peptone-protein, and phosphate and ammonium ions were transported through brine-saturated Berea sandstone cores in amounts sufficient to support microbial growth. Viable bacterial cells were transported through sandstone cores of 170-md permeability. Less than 1 % of the influent cell concentration was recovered in the effluent, indicating a high degree of cell retention inside the core. The addition of nutrients to these cores and subsequent incubation to allow for microbial growth resulted in permeability reductions of 60 to 80%. These data show that the growth of microorganisms significantly reduces the permeability of porous rock.
Effect of Applied Pressure on the Conductivity, Porosity and Permeability of Sandstones
Authors: Wyble D.O.
Published: December 2007

A pressurizing system was designed and built to apply a radial pressure of 5,000 psi to rock samples. Samples of the Bradford, Weir and Kirkwood sandstones were subjected to radial pressures parallel and perpendicular to the bedding in the system and the changes in conductivity, porosity and permeability were determined.

Asymptotic decreases in conductivity, porosity and Klinkenberg permeability were observed over the 0- to 3,500-psi range. From these data, the increase of formation factor over the same range was calculated. The cementation exponent expressed in the Archie equation was found to increase with pressure.

The rate of change varied from formation to formation. Only small differences were observed for samples taken parallel to the bedding as compared to those taken perpendicular to it except for the Bradford sand.

Above 3,500 psi the data are not good enough to tell if the properties continue to fall-off asymptotically or in a different manner. A possible explanation for the probable limit of the asymptotic rate around 3,500 to 4,500 psi is that this represents the maximum pressure which the formations have undergone during their geological life as a result of burial.

Introduction

For many years measurements have been made in the laboratory of the properties of oil-bearing sandstones with little consideration being given to whether these properties had been changed when the samples were moved from their original position in the ground to the laboratory.

Relatively little has been reported in the literature on the effect of pressure on the properties of sandstones. The changes in permeability for eight. typical consolidated oil-bearing sandstone samples with overburden pressure (0- to 15,000-psi range) was presented by Fatt and Davis in graphical form. In 1953 Fatt also reported the relationship between porosity and overburden pressure for four typical consolidated oil-bearing sandstone samples (0- to 5,000-psi range).
Diffusional Effects in the Recovery of Methane From Coalbeds
Authors: Smith Douglas M. , Williams Frank L.
Published: December 2007

This paper presents evidence that the unipore model is inadequate for describing diffusional fluxes from coal over the entire timescale of desorption. Field desorption of methane from coal pieces shows pronounced curvature, which is attributable to the bidisperse pore structure generally found for coal. A model is presented that accounts for the bidisperse pore structure of coal and predicts diffusion rates for both field and laboratory desorptions. Transient diffusivities are determined for Pittsburgh bituminous and Madrid (NM) anthracite coals by using a pulse tracer technique coupled with Fourier analysis of the elution curves. This technique allows the rapid determination of the diffusion parameters with minimal experimental effort. In addition, steady-state diffusivities are determined to identify mechanisms of diffusion. Diffusion was found to be a combination of bulk, Knudsen, and surface diffusions, depending on the coal pore structure and gas pressure.
Pressure Response at Observation Wells in Fractured Reservoirs
Authors: Chen C. C. , Yeh N. , Raghavan R. , Reynolds A. C.
Published: December 2007

This work examines interference test data in a naturally fractured reservoir. The reservoir model examined here assumes that the reservoir can be represented by a system of horizontal fractures that are separated by the matrix. This model is identical to the deSwaan-Kazemi model.

The main contribution of our work is that we combine the parameters of interest in a simple way and present solutions that can be used directly for field application. These solutions can be used to design or analyze interference tests. We also compare the solution for unsteady-state flow in the matrix with the Warren-Root model, which assumes pseudosteady-state fluid flow in the matrix.
Fatigue Analysis of Clad and Unclad Thick-Wall Structures
Authors: Gottlieb Theodore , Mann Tarlochan
Published: December 2007

It is common practice to clad steel components with a relatively thin layer of a stainless material to prevent corrosion economically. Little, however, has been published regarding the effect of such cladding on fatigue life in areas of localized high stress. Large valves that are pressure-cycled often and offshore equipment, such as risers, tensioners, and wellhead flanges that are loaded cyclically by ocean currents and waves, must be analyzed for fatigue life during design. Unlike storage vessels, drilling and completion hardware generally has areas of relatively high stress concentrations because of abrupt section size changes, threads, grooves for seals, bolt holes, and other stress-concentrating geometries. While yielding or rupturing is a function of bulk stresses, fatigue life is a function of peak stresses, which typically are highest on the surface of an area of stress concentration. It has been determined that both the metallurgical characteristics of the cladding and the pressure/load history can be varied to enhance or diminish significantly the fatigue life of a clad steel component. The results and conclusions of this study are based on laboratory studies. Axial fatigue tests (R = 0.05) were performed using a side-notched fatigue specimen that produces combined axial and bending stresses in the notched area. Specimens of AISI 4130 (at HRc 20) were tested unclad and with the notched area clad with Inconel 625 or AISI 316L. Each set of specimens was tested both unpreload-ed and preloaded to produce localized yielding at the notched surface only.

The findings of this study are applicable to components subject to failure by fatigue and corrosion fatigue and sour service steel components that become locally work-hardened either in service or during overload proof testing as required by most API specifications.
An Analytical Study of Interference in Composite Reservoirs
Authors: Satman Abdurrahman
Published: December 2007

This paper discusses the interference test in composite reservoirs. The composite model considers all important parameters of interest: the hydraulic diffusivity, the mobility ratio, the distance to the radial discontinuity, the distance between wells, the wellbore storage, and skin effect at the active well. Type curves expressed as a function of proper combinations of these parameters are presented.
Fatigue Behavior of Large-Diameter Wire Ropes
Authors: Hanzawa M. , Yokota H. , Toda Y. , Yokoyama K.
Published: December 2007

Factors influencing tensile fatigue strength of 50-mm wire ropes were investigated with a wire-breakage detecting system. The fatigue strength increased with an increase in wire strength and diameter and a decrease in self-rotativity of ropes. The epoxy resin was satisfactory as a socketing material.
Hydrodynamic Model For Intermittent Gas Lifting of Viscous Oil
Authors: Schmidt Zelimir , Doty Dale R. , Lukong Peter B. , Fernandez Orlando F. , Brill James P.
Published: December 2007

A hydrodynamic model was developed for intermittent gas lift. Simulation results were verified by experimental tests conducted with a 60 ft high 3 in. diameter test facility using air and an oil with viscosity of 108 cp. The simulation program was also successfully applied to data gathered on an instrumented intermittent gas lift well.

Results of the study indicate that initially the liquid slug undergoes a rapid acceleration and then accelerates at a much lower rate until the surface is reached, at which time rapid slug acceleration again occurs. It was found in this study that a significant portion of the liquid produced at the surface sometimes more than 50 percent, was contributed during the afterflow (i.e. liquid recovered in the form of entrained liquid in the gas core). In addition, the study has shown that by increasing the injection pressure, a higher recovery can be achieved more rapidly, but only at the pressure, a higher recovery can be achieved more rapidly, but only at the expense of increased gas injection. The model is also capable of predicting the cuing to tubing pressure ratio at which a minimum GOR will predicting the cuing to tubing pressure ratio at which a minimum GOR will occur. This minimum GOR pressure ratio was found to be sensitive to fluid viscosity.
Mean- and Low-Frequency Wave Forces on Semisubmersibles
Authors: Pinkster J. A.
Published: December 2007

Mean- and low-frequency wave drift forces on moored structures are important with respect to low-frequency motions and peak mooring loads. This paper addresses prediction of these forces on semisubmersible-type structures by use of computations based on three-dimensional (3D) potential theory. The discussion includes a computational method based on direct integration of pressure on the wetted part of the hull of arbitrarily shaped structures. Results of computations of horizontal drift forces on a six-column semisubmersible are compared with model tests in regular and irregular waves. The mean vertical drift forces on a submerged horizontal cylinder obtained from model tests also are compared with results of computations. On the basis of these comparisons, we conclude that wave drift forces on semisubmersible-type structures in conditions of waves without current can be predicted with reasonable accuracy by means of computations based on potential theory.
The Convergence of Upstream Collocation in the Buckley-Leverett Problem
Authors: Allen Myron B. , Pinder George F.
Published: December 2007

Upstream collocation is a fast and accurate scheme for simulating multiphase flows in oil reservoirs. In contrast to standard orthogonal collocation, upstream collocation yields numerical solutions to the Buckley-Leverett problem that converge to correct solutions physically. The failure of standard orthogonal collocation is not surprising, since the Buckley-Leverett problem as commonly stated is posed incompletely. The equal-area rule of Buckley and Leverett and the Welge tangent construction both specify additional constraints needed to close the problem properly. An error analysis of upstream collocation shows that this method forces convergence through an artificial dissipative term analogous to the "vanishing viscosity" used in shock fitting. This constraint is mathematically equivalent to the more familiar constructions and should prove beneficial in stimulating EOR schemes based on frontal displacement.
Analysis of Finite-Conductivity Fractures Intercepting Multilayer Commingled Reservoirs
Authors: Bennett Curtis O. , Raghavan Rajagopal , Reynolds Albert C.
Published: December 2007

The response of a fractured well in a multilayered reservoir is the primary subject of this study. Both analytical approximations and numerical results are presented. The analytical solutions served three important functions: (1) they enabled us to verify the numerical solutions used in this study; (2) they provided information on the structure of the solution and thus increased physical understanding; and (3) most importantly, they suggested a method whereby we were able to correlate multilayer solutions with single-layer solutions. We introduce the concept of dimensionless reservoir conductivity and show that in most realistic cases this parameter can be used to correlate commingled-reservoir solutions with the single-layer solutions available in the literature throughout the infinite-acting period. This concept and its utility in correlating solutions are the main contributions of this work.

We also consider the analysis of buildup data following a short producing time. As in the drawdown case, we show that the multilayer buildup solutions can be correlated with single-layer buildup solutions through the concept of dimensionless reservoir conductivity.
The Effect of Nozzle Diameter on Jet Impact for a Tricone Bit
Authors: Warren T. M. , Winters W. J.
Published: December 2007

Conventional techniques used to optimize the hydraulic conditions run with tricone bits usually are aimed at maximizing either jet hydraulic horsepower or jet impact force. A basic assumption underlying these optimization methods is that increased energy at the nozzle produces increased energy at the bottom of the hole. Conventional tricone bit nozzles are aimed at the "comer" of the borehole. The jets exist in a crossflow due to the return path of the fluid from under the bit. Many studies document the deflection and diffusion of a submerged jet stream in a crossflow. Studies were conducted with an 8½-in. [21.59-cm] Intl. Assn. of Drilling Contractors (IADC) Series 6-1-7 bit to determine the area and magnitude of the jet impact under a tricone bit. Flow rates up to 565 gal/min [35.6 dm3/s] and jet velocities up to 400 ft/sec [122 m/s] were used. The impact area was determined by (1) observing the location of an eroded zone beneath the bit in a block of Indiana limestone and (2) measuring the dynamic pressure beneath the bit in a test cell. Both tests indicate that a larger fraction of the jet energy reaches the hole bottom with small jets than with large jets. The tests also indicate that a larger fraction of the jet energy reaches the hole bottom when two jets are used instead of three.
Sensitivity of Steamflood Model Results to Grid and Timestep Sizes
Authors: Abou-Kassem Jamal Hussein , Aziz Khalid
Published: December 2007

Numerical simulation of complex processes in oil reservoirs has become a standard tool. The grid size and timestep sensitivity of a simulator are of prime concern in reaching the correct conclusions in any study. This paper presents an analysis of the sensitivity to timestep and grid size of a one-dimensional (1D) and two-dimensional (2D) compositional multiphase steamflood model used to simulate a heavy-oil reservoir.

The behavior of primary variables before breakthrough in the 1D and 2D cases is presented for clearer understanding of steamflooding heavy-oil reservoirs. The peculiar features exhibited by primary variables of the production and injection blocks for the 1D reservoir plus timestep and grid-size effects on primary variables for 2D cases studied are discussed.

Sensitivity studies of grid and timestep size are meaningful only if each is carried out while the other variable has minimum truncation error. The recovery performance parameters are less sensitive to timestep size than to grid size. They are also less sensitive in the 2D runs than in the 1D runs. The time/pore-volume-injected (PVI) relationship is very sensitive to grid size, and to a lesser extent, to timestep size.
Efficiency of D4 Gaussian Elimination on a Vector Computer
Authors: Stringer James C. , Thomas L. Kent , Pierson Ray G.
Published: December 2007

The efficiency of D4 Gaussian elimination on a vector computer, the Cray-1/S, is examined. The algorithm used in this work is employed routinely in Phillips Petroleum Co. reservoir simulation models. Comparisons of scalar and vector Cray-1/S times are given for various example cases including multiple unknowns per gridblock. Vectorization of the program on the Cray-1/S is discugsed.